github.com/sanprasirt/go@v0.0.0-20170607001320-a027466e4b6d/src/reflect/value.go (about) 1 // Copyright 2009 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package reflect 6 7 import ( 8 "math" 9 "runtime" 10 "unsafe" 11 ) 12 13 const ptrSize = 4 << (^uintptr(0) >> 63) // unsafe.Sizeof(uintptr(0)) but an ideal const 14 15 // Value is the reflection interface to a Go value. 16 // 17 // Not all methods apply to all kinds of values. Restrictions, 18 // if any, are noted in the documentation for each method. 19 // Use the Kind method to find out the kind of value before 20 // calling kind-specific methods. Calling a method 21 // inappropriate to the kind of type causes a run time panic. 22 // 23 // The zero Value represents no value. 24 // Its IsValid method returns false, its Kind method returns Invalid, 25 // its String method returns "<invalid Value>", and all other methods panic. 26 // Most functions and methods never return an invalid value. 27 // If one does, its documentation states the conditions explicitly. 28 // 29 // A Value can be used concurrently by multiple goroutines provided that 30 // the underlying Go value can be used concurrently for the equivalent 31 // direct operations. 32 // 33 // To compare two Values, compare the results of the Interface method. 34 // Using == on two Values does not compare the underlying values 35 // they represent. 36 type Value struct { 37 // typ holds the type of the value represented by a Value. 38 typ *rtype 39 40 // Pointer-valued data or, if flagIndir is set, pointer to data. 41 // Valid when either flagIndir is set or typ.pointers() is true. 42 ptr unsafe.Pointer 43 44 // flag holds metadata about the value. 45 // The lowest bits are flag bits: 46 // - flagStickyRO: obtained via unexported not embedded field, so read-only 47 // - flagEmbedRO: obtained via unexported embedded field, so read-only 48 // - flagIndir: val holds a pointer to the data 49 // - flagAddr: v.CanAddr is true (implies flagIndir) 50 // - flagMethod: v is a method value. 51 // The next five bits give the Kind of the value. 52 // This repeats typ.Kind() except for method values. 53 // The remaining 23+ bits give a method number for method values. 54 // If flag.kind() != Func, code can assume that flagMethod is unset. 55 // If ifaceIndir(typ), code can assume that flagIndir is set. 56 flag 57 58 // A method value represents a curried method invocation 59 // like r.Read for some receiver r. The typ+val+flag bits describe 60 // the receiver r, but the flag's Kind bits say Func (methods are 61 // functions), and the top bits of the flag give the method number 62 // in r's type's method table. 63 } 64 65 type flag uintptr 66 67 const ( 68 flagKindWidth = 5 // there are 27 kinds 69 flagKindMask flag = 1<<flagKindWidth - 1 70 flagStickyRO flag = 1 << 5 71 flagEmbedRO flag = 1 << 6 72 flagIndir flag = 1 << 7 73 flagAddr flag = 1 << 8 74 flagMethod flag = 1 << 9 75 flagMethodShift = 10 76 flagRO flag = flagStickyRO | flagEmbedRO 77 ) 78 79 func (f flag) kind() Kind { 80 return Kind(f & flagKindMask) 81 } 82 83 // pointer returns the underlying pointer represented by v. 84 // v.Kind() must be Ptr, Map, Chan, Func, or UnsafePointer 85 func (v Value) pointer() unsafe.Pointer { 86 if v.typ.size != ptrSize || !v.typ.pointers() { 87 panic("can't call pointer on a non-pointer Value") 88 } 89 if v.flag&flagIndir != 0 { 90 return *(*unsafe.Pointer)(v.ptr) 91 } 92 return v.ptr 93 } 94 95 // packEface converts v to the empty interface. 96 func packEface(v Value) interface{} { 97 t := v.typ 98 var i interface{} 99 e := (*emptyInterface)(unsafe.Pointer(&i)) 100 // First, fill in the data portion of the interface. 101 switch { 102 case ifaceIndir(t): 103 if v.flag&flagIndir == 0 { 104 panic("bad indir") 105 } 106 // Value is indirect, and so is the interface we're making. 107 ptr := v.ptr 108 if v.flag&flagAddr != 0 { 109 // TODO: pass safe boolean from valueInterface so 110 // we don't need to copy if safe==true? 111 c := unsafe_New(t) 112 typedmemmove(t, c, ptr) 113 ptr = c 114 } 115 e.word = ptr 116 case v.flag&flagIndir != 0: 117 // Value is indirect, but interface is direct. We need 118 // to load the data at v.ptr into the interface data word. 119 e.word = *(*unsafe.Pointer)(v.ptr) 120 default: 121 // Value is direct, and so is the interface. 122 e.word = v.ptr 123 } 124 // Now, fill in the type portion. We're very careful here not 125 // to have any operation between the e.word and e.typ assignments 126 // that would let the garbage collector observe the partially-built 127 // interface value. 128 e.typ = t 129 return i 130 } 131 132 // unpackEface converts the empty interface i to a Value. 133 func unpackEface(i interface{}) Value { 134 e := (*emptyInterface)(unsafe.Pointer(&i)) 135 // NOTE: don't read e.word until we know whether it is really a pointer or not. 136 t := e.typ 137 if t == nil { 138 return Value{} 139 } 140 f := flag(t.Kind()) 141 if ifaceIndir(t) { 142 f |= flagIndir 143 } 144 return Value{t, e.word, f} 145 } 146 147 // A ValueError occurs when a Value method is invoked on 148 // a Value that does not support it. Such cases are documented 149 // in the description of each method. 150 type ValueError struct { 151 Method string 152 Kind Kind 153 } 154 155 func (e *ValueError) Error() string { 156 if e.Kind == 0 { 157 return "reflect: call of " + e.Method + " on zero Value" 158 } 159 return "reflect: call of " + e.Method + " on " + e.Kind.String() + " Value" 160 } 161 162 // methodName returns the name of the calling method, 163 // assumed to be two stack frames above. 164 func methodName() string { 165 pc, _, _, _ := runtime.Caller(2) 166 f := runtime.FuncForPC(pc) 167 if f == nil { 168 return "unknown method" 169 } 170 return f.Name() 171 } 172 173 // emptyInterface is the header for an interface{} value. 174 type emptyInterface struct { 175 typ *rtype 176 word unsafe.Pointer 177 } 178 179 // nonEmptyInterface is the header for a interface value with methods. 180 type nonEmptyInterface struct { 181 // see ../runtime/iface.go:/Itab 182 itab *struct { 183 ityp *rtype // static interface type 184 typ *rtype // dynamic concrete type 185 link unsafe.Pointer 186 bad int32 187 unused int32 188 fun [100000]unsafe.Pointer // method table 189 } 190 word unsafe.Pointer 191 } 192 193 // mustBe panics if f's kind is not expected. 194 // Making this a method on flag instead of on Value 195 // (and embedding flag in Value) means that we can write 196 // the very clear v.mustBe(Bool) and have it compile into 197 // v.flag.mustBe(Bool), which will only bother to copy the 198 // single important word for the receiver. 199 func (f flag) mustBe(expected Kind) { 200 if f.kind() != expected { 201 panic(&ValueError{methodName(), f.kind()}) 202 } 203 } 204 205 // mustBeExported panics if f records that the value was obtained using 206 // an unexported field. 207 func (f flag) mustBeExported() { 208 if f == 0 { 209 panic(&ValueError{methodName(), 0}) 210 } 211 if f&flagRO != 0 { 212 panic("reflect: " + methodName() + " using value obtained using unexported field") 213 } 214 } 215 216 // mustBeAssignable panics if f records that the value is not assignable, 217 // which is to say that either it was obtained using an unexported field 218 // or it is not addressable. 219 func (f flag) mustBeAssignable() { 220 if f == 0 { 221 panic(&ValueError{methodName(), Invalid}) 222 } 223 // Assignable if addressable and not read-only. 224 if f&flagRO != 0 { 225 panic("reflect: " + methodName() + " using value obtained using unexported field") 226 } 227 if f&flagAddr == 0 { 228 panic("reflect: " + methodName() + " using unaddressable value") 229 } 230 } 231 232 // Addr returns a pointer value representing the address of v. 233 // It panics if CanAddr() returns false. 234 // Addr is typically used to obtain a pointer to a struct field 235 // or slice element in order to call a method that requires a 236 // pointer receiver. 237 func (v Value) Addr() Value { 238 if v.flag&flagAddr == 0 { 239 panic("reflect.Value.Addr of unaddressable value") 240 } 241 return Value{v.typ.ptrTo(), v.ptr, (v.flag & flagRO) | flag(Ptr)} 242 } 243 244 // Bool returns v's underlying value. 245 // It panics if v's kind is not Bool. 246 func (v Value) Bool() bool { 247 v.mustBe(Bool) 248 return *(*bool)(v.ptr) 249 } 250 251 // Bytes returns v's underlying value. 252 // It panics if v's underlying value is not a slice of bytes. 253 func (v Value) Bytes() []byte { 254 v.mustBe(Slice) 255 if v.typ.Elem().Kind() != Uint8 { 256 panic("reflect.Value.Bytes of non-byte slice") 257 } 258 // Slice is always bigger than a word; assume flagIndir. 259 return *(*[]byte)(v.ptr) 260 } 261 262 // runes returns v's underlying value. 263 // It panics if v's underlying value is not a slice of runes (int32s). 264 func (v Value) runes() []rune { 265 v.mustBe(Slice) 266 if v.typ.Elem().Kind() != Int32 { 267 panic("reflect.Value.Bytes of non-rune slice") 268 } 269 // Slice is always bigger than a word; assume flagIndir. 270 return *(*[]rune)(v.ptr) 271 } 272 273 // CanAddr reports whether the value's address can be obtained with Addr. 274 // Such values are called addressable. A value is addressable if it is 275 // an element of a slice, an element of an addressable array, 276 // a field of an addressable struct, or the result of dereferencing a pointer. 277 // If CanAddr returns false, calling Addr will panic. 278 func (v Value) CanAddr() bool { 279 return v.flag&flagAddr != 0 280 } 281 282 // CanSet reports whether the value of v can be changed. 283 // A Value can be changed only if it is addressable and was not 284 // obtained by the use of unexported struct fields. 285 // If CanSet returns false, calling Set or any type-specific 286 // setter (e.g., SetBool, SetInt) will panic. 287 func (v Value) CanSet() bool { 288 return v.flag&(flagAddr|flagRO) == flagAddr 289 } 290 291 // Call calls the function v with the input arguments in. 292 // For example, if len(in) == 3, v.Call(in) represents the Go call v(in[0], in[1], in[2]). 293 // Call panics if v's Kind is not Func. 294 // It returns the output results as Values. 295 // As in Go, each input argument must be assignable to the 296 // type of the function's corresponding input parameter. 297 // If v is a variadic function, Call creates the variadic slice parameter 298 // itself, copying in the corresponding values. 299 func (v Value) Call(in []Value) []Value { 300 v.mustBe(Func) 301 v.mustBeExported() 302 return v.call("Call", in) 303 } 304 305 // CallSlice calls the variadic function v with the input arguments in, 306 // assigning the slice in[len(in)-1] to v's final variadic argument. 307 // For example, if len(in) == 3, v.CallSlice(in) represents the Go call v(in[0], in[1], in[2]...). 308 // CallSlice panics if v's Kind is not Func or if v is not variadic. 309 // It returns the output results as Values. 310 // As in Go, each input argument must be assignable to the 311 // type of the function's corresponding input parameter. 312 func (v Value) CallSlice(in []Value) []Value { 313 v.mustBe(Func) 314 v.mustBeExported() 315 return v.call("CallSlice", in) 316 } 317 318 var callGC bool // for testing; see TestCallMethodJump 319 320 func (v Value) call(op string, in []Value) []Value { 321 // Get function pointer, type. 322 t := v.typ 323 var ( 324 fn unsafe.Pointer 325 rcvr Value 326 rcvrtype *rtype 327 ) 328 if v.flag&flagMethod != 0 { 329 rcvr = v 330 rcvrtype, t, fn = methodReceiver(op, v, int(v.flag)>>flagMethodShift) 331 } else if v.flag&flagIndir != 0 { 332 fn = *(*unsafe.Pointer)(v.ptr) 333 } else { 334 fn = v.ptr 335 } 336 337 if fn == nil { 338 panic("reflect.Value.Call: call of nil function") 339 } 340 341 isSlice := op == "CallSlice" 342 n := t.NumIn() 343 if isSlice { 344 if !t.IsVariadic() { 345 panic("reflect: CallSlice of non-variadic function") 346 } 347 if len(in) < n { 348 panic("reflect: CallSlice with too few input arguments") 349 } 350 if len(in) > n { 351 panic("reflect: CallSlice with too many input arguments") 352 } 353 } else { 354 if t.IsVariadic() { 355 n-- 356 } 357 if len(in) < n { 358 panic("reflect: Call with too few input arguments") 359 } 360 if !t.IsVariadic() && len(in) > n { 361 panic("reflect: Call with too many input arguments") 362 } 363 } 364 for _, x := range in { 365 if x.Kind() == Invalid { 366 panic("reflect: " + op + " using zero Value argument") 367 } 368 } 369 for i := 0; i < n; i++ { 370 if xt, targ := in[i].Type(), t.In(i); !xt.AssignableTo(targ) { 371 panic("reflect: " + op + " using " + xt.String() + " as type " + targ.String()) 372 } 373 } 374 if !isSlice && t.IsVariadic() { 375 // prepare slice for remaining values 376 m := len(in) - n 377 slice := MakeSlice(t.In(n), m, m) 378 elem := t.In(n).Elem() 379 for i := 0; i < m; i++ { 380 x := in[n+i] 381 if xt := x.Type(); !xt.AssignableTo(elem) { 382 panic("reflect: cannot use " + xt.String() + " as type " + elem.String() + " in " + op) 383 } 384 slice.Index(i).Set(x) 385 } 386 origIn := in 387 in = make([]Value, n+1) 388 copy(in[:n], origIn) 389 in[n] = slice 390 } 391 392 nin := len(in) 393 if nin != t.NumIn() { 394 panic("reflect.Value.Call: wrong argument count") 395 } 396 nout := t.NumOut() 397 398 // Compute frame type. 399 frametype, _, retOffset, _, framePool := funcLayout(t, rcvrtype) 400 401 // Allocate a chunk of memory for frame. 402 var args unsafe.Pointer 403 if nout == 0 { 404 args = framePool.Get().(unsafe.Pointer) 405 } else { 406 // Can't use pool if the function has return values. 407 // We will leak pointer to args in ret, so its lifetime is not scoped. 408 args = unsafe_New(frametype) 409 } 410 off := uintptr(0) 411 412 // Copy inputs into args. 413 if rcvrtype != nil { 414 storeRcvr(rcvr, args) 415 off = ptrSize 416 } 417 for i, v := range in { 418 v.mustBeExported() 419 targ := t.In(i).(*rtype) 420 a := uintptr(targ.align) 421 off = (off + a - 1) &^ (a - 1) 422 n := targ.size 423 addr := unsafe.Pointer(uintptr(args) + off) 424 v = v.assignTo("reflect.Value.Call", targ, addr) 425 if v.flag&flagIndir != 0 { 426 typedmemmove(targ, addr, v.ptr) 427 } else { 428 *(*unsafe.Pointer)(addr) = v.ptr 429 } 430 off += n 431 } 432 433 // Call. 434 call(frametype, fn, args, uint32(frametype.size), uint32(retOffset)) 435 436 // For testing; see TestCallMethodJump. 437 if callGC { 438 runtime.GC() 439 } 440 441 var ret []Value 442 if nout == 0 { 443 // This is untyped because the frame is really a 444 // stack, even though it's a heap object. 445 memclrNoHeapPointers(args, frametype.size) 446 framePool.Put(args) 447 } else { 448 // Zero the now unused input area of args, 449 // because the Values returned by this function contain pointers to the args object, 450 // and will thus keep the args object alive indefinitely. 451 memclrNoHeapPointers(args, retOffset) 452 // Wrap Values around return values in args. 453 ret = make([]Value, nout) 454 off = retOffset 455 for i := 0; i < nout; i++ { 456 tv := t.Out(i) 457 a := uintptr(tv.Align()) 458 off = (off + a - 1) &^ (a - 1) 459 fl := flagIndir | flag(tv.Kind()) 460 ret[i] = Value{tv.common(), unsafe.Pointer(uintptr(args) + off), fl} 461 off += tv.Size() 462 } 463 } 464 465 return ret 466 } 467 468 // callReflect is the call implementation used by a function 469 // returned by MakeFunc. In many ways it is the opposite of the 470 // method Value.call above. The method above converts a call using Values 471 // into a call of a function with a concrete argument frame, while 472 // callReflect converts a call of a function with a concrete argument 473 // frame into a call using Values. 474 // It is in this file so that it can be next to the call method above. 475 // The remainder of the MakeFunc implementation is in makefunc.go. 476 // 477 // NOTE: This function must be marked as a "wrapper" in the generated code, 478 // so that the linker can make it work correctly for panic and recover. 479 // The gc compilers know to do that for the name "reflect.callReflect". 480 func callReflect(ctxt *makeFuncImpl, frame unsafe.Pointer) { 481 ftyp := ctxt.typ 482 f := ctxt.fn 483 484 // Copy argument frame into Values. 485 ptr := frame 486 off := uintptr(0) 487 in := make([]Value, 0, int(ftyp.inCount)) 488 for _, typ := range ftyp.in() { 489 off += -off & uintptr(typ.align-1) 490 addr := unsafe.Pointer(uintptr(ptr) + off) 491 v := Value{typ, nil, flag(typ.Kind())} 492 if ifaceIndir(typ) { 493 // value cannot be inlined in interface data. 494 // Must make a copy, because f might keep a reference to it, 495 // and we cannot let f keep a reference to the stack frame 496 // after this function returns, not even a read-only reference. 497 v.ptr = unsafe_New(typ) 498 typedmemmove(typ, v.ptr, addr) 499 v.flag |= flagIndir 500 } else { 501 v.ptr = *(*unsafe.Pointer)(addr) 502 } 503 in = append(in, v) 504 off += typ.size 505 } 506 507 // Call underlying function. 508 out := f(in) 509 numOut := ftyp.NumOut() 510 if len(out) != numOut { 511 panic("reflect: wrong return count from function created by MakeFunc") 512 } 513 514 // Copy results back into argument frame. 515 if numOut > 0 { 516 off += -off & (ptrSize - 1) 517 if runtime.GOARCH == "amd64p32" { 518 off = align(off, 8) 519 } 520 for i, typ := range ftyp.out() { 521 v := out[i] 522 if v.typ != typ { 523 panic("reflect: function created by MakeFunc using " + funcName(f) + 524 " returned wrong type: have " + 525 out[i].typ.String() + " for " + typ.String()) 526 } 527 if v.flag&flagRO != 0 { 528 panic("reflect: function created by MakeFunc using " + funcName(f) + 529 " returned value obtained from unexported field") 530 } 531 off += -off & uintptr(typ.align-1) 532 addr := unsafe.Pointer(uintptr(ptr) + off) 533 if v.flag&flagIndir != 0 { 534 typedmemmove(typ, addr, v.ptr) 535 } else { 536 *(*unsafe.Pointer)(addr) = v.ptr 537 } 538 off += typ.size 539 } 540 } 541 542 // runtime.getArgInfo expects to be able to find ctxt on the 543 // stack when it finds our caller, makeFuncStub. Make sure it 544 // doesn't get garbage collected. 545 runtime.KeepAlive(ctxt) 546 } 547 548 // methodReceiver returns information about the receiver 549 // described by v. The Value v may or may not have the 550 // flagMethod bit set, so the kind cached in v.flag should 551 // not be used. 552 // The return value rcvrtype gives the method's actual receiver type. 553 // The return value t gives the method type signature (without the receiver). 554 // The return value fn is a pointer to the method code. 555 func methodReceiver(op string, v Value, methodIndex int) (rcvrtype, t *rtype, fn unsafe.Pointer) { 556 i := methodIndex 557 if v.typ.Kind() == Interface { 558 tt := (*interfaceType)(unsafe.Pointer(v.typ)) 559 if uint(i) >= uint(len(tt.methods)) { 560 panic("reflect: internal error: invalid method index") 561 } 562 m := &tt.methods[i] 563 if !tt.nameOff(m.name).isExported() { 564 panic("reflect: " + op + " of unexported method") 565 } 566 iface := (*nonEmptyInterface)(v.ptr) 567 if iface.itab == nil { 568 panic("reflect: " + op + " of method on nil interface value") 569 } 570 rcvrtype = iface.itab.typ 571 fn = unsafe.Pointer(&iface.itab.fun[i]) 572 t = tt.typeOff(m.typ) 573 } else { 574 rcvrtype = v.typ 575 ut := v.typ.uncommon() 576 if ut == nil || uint(i) >= uint(ut.mcount) { 577 panic("reflect: internal error: invalid method index") 578 } 579 m := ut.methods()[i] 580 if !v.typ.nameOff(m.name).isExported() { 581 panic("reflect: " + op + " of unexported method") 582 } 583 ifn := v.typ.textOff(m.ifn) 584 fn = unsafe.Pointer(&ifn) 585 t = v.typ.typeOff(m.mtyp) 586 } 587 return 588 } 589 590 // v is a method receiver. Store at p the word which is used to 591 // encode that receiver at the start of the argument list. 592 // Reflect uses the "interface" calling convention for 593 // methods, which always uses one word to record the receiver. 594 func storeRcvr(v Value, p unsafe.Pointer) { 595 t := v.typ 596 if t.Kind() == Interface { 597 // the interface data word becomes the receiver word 598 iface := (*nonEmptyInterface)(v.ptr) 599 *(*unsafe.Pointer)(p) = iface.word 600 } else if v.flag&flagIndir != 0 && !ifaceIndir(t) { 601 *(*unsafe.Pointer)(p) = *(*unsafe.Pointer)(v.ptr) 602 } else { 603 *(*unsafe.Pointer)(p) = v.ptr 604 } 605 } 606 607 // align returns the result of rounding x up to a multiple of n. 608 // n must be a power of two. 609 func align(x, n uintptr) uintptr { 610 return (x + n - 1) &^ (n - 1) 611 } 612 613 // callMethod is the call implementation used by a function returned 614 // by makeMethodValue (used by v.Method(i).Interface()). 615 // It is a streamlined version of the usual reflect call: the caller has 616 // already laid out the argument frame for us, so we don't have 617 // to deal with individual Values for each argument. 618 // It is in this file so that it can be next to the two similar functions above. 619 // The remainder of the makeMethodValue implementation is in makefunc.go. 620 // 621 // NOTE: This function must be marked as a "wrapper" in the generated code, 622 // so that the linker can make it work correctly for panic and recover. 623 // The gc compilers know to do that for the name "reflect.callMethod". 624 func callMethod(ctxt *methodValue, frame unsafe.Pointer) { 625 rcvr := ctxt.rcvr 626 rcvrtype, t, fn := methodReceiver("call", rcvr, ctxt.method) 627 frametype, argSize, retOffset, _, framePool := funcLayout(t, rcvrtype) 628 629 // Make a new frame that is one word bigger so we can store the receiver. 630 args := framePool.Get().(unsafe.Pointer) 631 632 // Copy in receiver and rest of args. 633 // Avoid constructing out-of-bounds pointers if there are no args. 634 storeRcvr(rcvr, args) 635 if argSize-ptrSize > 0 { 636 typedmemmovepartial(frametype, unsafe.Pointer(uintptr(args)+ptrSize), frame, ptrSize, argSize-ptrSize) 637 } 638 639 // Call. 640 call(frametype, fn, args, uint32(frametype.size), uint32(retOffset)) 641 642 // Copy return values. On amd64p32, the beginning of return values 643 // is 64-bit aligned, so the caller's frame layout (which doesn't have 644 // a receiver) is different from the layout of the fn call, which has 645 // a receiver. 646 // Ignore any changes to args and just copy return values. 647 // Avoid constructing out-of-bounds pointers if there are no return values. 648 if frametype.size-retOffset > 0 { 649 callerRetOffset := retOffset - ptrSize 650 if runtime.GOARCH == "amd64p32" { 651 callerRetOffset = align(argSize-ptrSize, 8) 652 } 653 typedmemmovepartial(frametype, 654 unsafe.Pointer(uintptr(frame)+callerRetOffset), 655 unsafe.Pointer(uintptr(args)+retOffset), 656 retOffset, 657 frametype.size-retOffset) 658 } 659 660 // This is untyped because the frame is really a stack, even 661 // though it's a heap object. 662 memclrNoHeapPointers(args, frametype.size) 663 framePool.Put(args) 664 665 // See the comment in callReflect. 666 runtime.KeepAlive(ctxt) 667 } 668 669 // funcName returns the name of f, for use in error messages. 670 func funcName(f func([]Value) []Value) string { 671 pc := *(*uintptr)(unsafe.Pointer(&f)) 672 rf := runtime.FuncForPC(pc) 673 if rf != nil { 674 return rf.Name() 675 } 676 return "closure" 677 } 678 679 // Cap returns v's capacity. 680 // It panics if v's Kind is not Array, Chan, or Slice. 681 func (v Value) Cap() int { 682 k := v.kind() 683 switch k { 684 case Array: 685 return v.typ.Len() 686 case Chan: 687 return chancap(v.pointer()) 688 case Slice: 689 // Slice is always bigger than a word; assume flagIndir. 690 return (*sliceHeader)(v.ptr).Cap 691 } 692 panic(&ValueError{"reflect.Value.Cap", v.kind()}) 693 } 694 695 // Close closes the channel v. 696 // It panics if v's Kind is not Chan. 697 func (v Value) Close() { 698 v.mustBe(Chan) 699 v.mustBeExported() 700 chanclose(v.pointer()) 701 } 702 703 // Complex returns v's underlying value, as a complex128. 704 // It panics if v's Kind is not Complex64 or Complex128 705 func (v Value) Complex() complex128 { 706 k := v.kind() 707 switch k { 708 case Complex64: 709 return complex128(*(*complex64)(v.ptr)) 710 case Complex128: 711 return *(*complex128)(v.ptr) 712 } 713 panic(&ValueError{"reflect.Value.Complex", v.kind()}) 714 } 715 716 // Elem returns the value that the interface v contains 717 // or that the pointer v points to. 718 // It panics if v's Kind is not Interface or Ptr. 719 // It returns the zero Value if v is nil. 720 func (v Value) Elem() Value { 721 k := v.kind() 722 switch k { 723 case Interface: 724 var eface interface{} 725 if v.typ.NumMethod() == 0 { 726 eface = *(*interface{})(v.ptr) 727 } else { 728 eface = (interface{})(*(*interface { 729 M() 730 })(v.ptr)) 731 } 732 x := unpackEface(eface) 733 if x.flag != 0 { 734 x.flag |= v.flag & flagRO 735 } 736 return x 737 case Ptr: 738 ptr := v.ptr 739 if v.flag&flagIndir != 0 { 740 ptr = *(*unsafe.Pointer)(ptr) 741 } 742 // The returned value's address is v's value. 743 if ptr == nil { 744 return Value{} 745 } 746 tt := (*ptrType)(unsafe.Pointer(v.typ)) 747 typ := tt.elem 748 fl := v.flag&flagRO | flagIndir | flagAddr 749 fl |= flag(typ.Kind()) 750 return Value{typ, ptr, fl} 751 } 752 panic(&ValueError{"reflect.Value.Elem", v.kind()}) 753 } 754 755 // Field returns the i'th field of the struct v. 756 // It panics if v's Kind is not Struct or i is out of range. 757 func (v Value) Field(i int) Value { 758 if v.kind() != Struct { 759 panic(&ValueError{"reflect.Value.Field", v.kind()}) 760 } 761 tt := (*structType)(unsafe.Pointer(v.typ)) 762 if uint(i) >= uint(len(tt.fields)) { 763 panic("reflect: Field index out of range") 764 } 765 field := &tt.fields[i] 766 typ := field.typ 767 768 // Inherit permission bits from v, but clear flagEmbedRO. 769 fl := v.flag&(flagStickyRO|flagIndir|flagAddr) | flag(typ.Kind()) 770 // Using an unexported field forces flagRO. 771 if !field.name.isExported() { 772 if field.anon() { 773 fl |= flagEmbedRO 774 } else { 775 fl |= flagStickyRO 776 } 777 } 778 // Either flagIndir is set and v.ptr points at struct, 779 // or flagIndir is not set and v.ptr is the actual struct data. 780 // In the former case, we want v.ptr + offset. 781 // In the latter case, we must have field.offset = 0, 782 // so v.ptr + field.offset is still okay. 783 ptr := unsafe.Pointer(uintptr(v.ptr) + field.offset()) 784 return Value{typ, ptr, fl} 785 } 786 787 // FieldByIndex returns the nested field corresponding to index. 788 // It panics if v's Kind is not struct. 789 func (v Value) FieldByIndex(index []int) Value { 790 if len(index) == 1 { 791 return v.Field(index[0]) 792 } 793 v.mustBe(Struct) 794 for i, x := range index { 795 if i > 0 { 796 if v.Kind() == Ptr && v.typ.Elem().Kind() == Struct { 797 if v.IsNil() { 798 panic("reflect: indirection through nil pointer to embedded struct") 799 } 800 v = v.Elem() 801 } 802 } 803 v = v.Field(x) 804 } 805 return v 806 } 807 808 // FieldByName returns the struct field with the given name. 809 // It returns the zero Value if no field was found. 810 // It panics if v's Kind is not struct. 811 func (v Value) FieldByName(name string) Value { 812 v.mustBe(Struct) 813 if f, ok := v.typ.FieldByName(name); ok { 814 return v.FieldByIndex(f.Index) 815 } 816 return Value{} 817 } 818 819 // FieldByNameFunc returns the struct field with a name 820 // that satisfies the match function. 821 // It panics if v's Kind is not struct. 822 // It returns the zero Value if no field was found. 823 func (v Value) FieldByNameFunc(match func(string) bool) Value { 824 if f, ok := v.typ.FieldByNameFunc(match); ok { 825 return v.FieldByIndex(f.Index) 826 } 827 return Value{} 828 } 829 830 // Float returns v's underlying value, as a float64. 831 // It panics if v's Kind is not Float32 or Float64 832 func (v Value) Float() float64 { 833 k := v.kind() 834 switch k { 835 case Float32: 836 return float64(*(*float32)(v.ptr)) 837 case Float64: 838 return *(*float64)(v.ptr) 839 } 840 panic(&ValueError{"reflect.Value.Float", v.kind()}) 841 } 842 843 var uint8Type = TypeOf(uint8(0)).(*rtype) 844 845 // Index returns v's i'th element. 846 // It panics if v's Kind is not Array, Slice, or String or i is out of range. 847 func (v Value) Index(i int) Value { 848 switch v.kind() { 849 case Array: 850 tt := (*arrayType)(unsafe.Pointer(v.typ)) 851 if uint(i) >= uint(tt.len) { 852 panic("reflect: array index out of range") 853 } 854 typ := tt.elem 855 offset := uintptr(i) * typ.size 856 857 // Either flagIndir is set and v.ptr points at array, 858 // or flagIndir is not set and v.ptr is the actual array data. 859 // In the former case, we want v.ptr + offset. 860 // In the latter case, we must be doing Index(0), so offset = 0, 861 // so v.ptr + offset is still okay. 862 val := unsafe.Pointer(uintptr(v.ptr) + offset) 863 fl := v.flag&(flagRO|flagIndir|flagAddr) | flag(typ.Kind()) // bits same as overall array 864 return Value{typ, val, fl} 865 866 case Slice: 867 // Element flag same as Elem of Ptr. 868 // Addressable, indirect, possibly read-only. 869 s := (*sliceHeader)(v.ptr) 870 if uint(i) >= uint(s.Len) { 871 panic("reflect: slice index out of range") 872 } 873 tt := (*sliceType)(unsafe.Pointer(v.typ)) 874 typ := tt.elem 875 val := arrayAt(s.Data, i, typ.size) 876 fl := flagAddr | flagIndir | v.flag&flagRO | flag(typ.Kind()) 877 return Value{typ, val, fl} 878 879 case String: 880 s := (*stringHeader)(v.ptr) 881 if uint(i) >= uint(s.Len) { 882 panic("reflect: string index out of range") 883 } 884 p := arrayAt(s.Data, i, 1) 885 fl := v.flag&flagRO | flag(Uint8) | flagIndir 886 return Value{uint8Type, p, fl} 887 } 888 panic(&ValueError{"reflect.Value.Index", v.kind()}) 889 } 890 891 // Int returns v's underlying value, as an int64. 892 // It panics if v's Kind is not Int, Int8, Int16, Int32, or Int64. 893 func (v Value) Int() int64 { 894 k := v.kind() 895 p := v.ptr 896 switch k { 897 case Int: 898 return int64(*(*int)(p)) 899 case Int8: 900 return int64(*(*int8)(p)) 901 case Int16: 902 return int64(*(*int16)(p)) 903 case Int32: 904 return int64(*(*int32)(p)) 905 case Int64: 906 return *(*int64)(p) 907 } 908 panic(&ValueError{"reflect.Value.Int", v.kind()}) 909 } 910 911 // CanInterface reports whether Interface can be used without panicking. 912 func (v Value) CanInterface() bool { 913 if v.flag == 0 { 914 panic(&ValueError{"reflect.Value.CanInterface", Invalid}) 915 } 916 return v.flag&flagRO == 0 917 } 918 919 // Interface returns v's current value as an interface{}. 920 // It is equivalent to: 921 // var i interface{} = (v's underlying value) 922 // It panics if the Value was obtained by accessing 923 // unexported struct fields. 924 func (v Value) Interface() (i interface{}) { 925 return valueInterface(v, true) 926 } 927 928 func valueInterface(v Value, safe bool) interface{} { 929 if v.flag == 0 { 930 panic(&ValueError{"reflect.Value.Interface", 0}) 931 } 932 if safe && v.flag&flagRO != 0 { 933 // Do not allow access to unexported values via Interface, 934 // because they might be pointers that should not be 935 // writable or methods or function that should not be callable. 936 panic("reflect.Value.Interface: cannot return value obtained from unexported field or method") 937 } 938 if v.flag&flagMethod != 0 { 939 v = makeMethodValue("Interface", v) 940 } 941 942 if v.kind() == Interface { 943 // Special case: return the element inside the interface. 944 // Empty interface has one layout, all interfaces with 945 // methods have a second layout. 946 if v.NumMethod() == 0 { 947 return *(*interface{})(v.ptr) 948 } 949 return *(*interface { 950 M() 951 })(v.ptr) 952 } 953 954 // TODO: pass safe to packEface so we don't need to copy if safe==true? 955 return packEface(v) 956 } 957 958 // InterfaceData returns the interface v's value as a uintptr pair. 959 // It panics if v's Kind is not Interface. 960 func (v Value) InterfaceData() [2]uintptr { 961 // TODO: deprecate this 962 v.mustBe(Interface) 963 // We treat this as a read operation, so we allow 964 // it even for unexported data, because the caller 965 // has to import "unsafe" to turn it into something 966 // that can be abused. 967 // Interface value is always bigger than a word; assume flagIndir. 968 return *(*[2]uintptr)(v.ptr) 969 } 970 971 // IsNil reports whether its argument v is nil. The argument must be 972 // a chan, func, interface, map, pointer, or slice value; if it is 973 // not, IsNil panics. Note that IsNil is not always equivalent to a 974 // regular comparison with nil in Go. For example, if v was created 975 // by calling ValueOf with an uninitialized interface variable i, 976 // i==nil will be true but v.IsNil will panic as v will be the zero 977 // Value. 978 func (v Value) IsNil() bool { 979 k := v.kind() 980 switch k { 981 case Chan, Func, Map, Ptr: 982 if v.flag&flagMethod != 0 { 983 return false 984 } 985 ptr := v.ptr 986 if v.flag&flagIndir != 0 { 987 ptr = *(*unsafe.Pointer)(ptr) 988 } 989 return ptr == nil 990 case Interface, Slice: 991 // Both interface and slice are nil if first word is 0. 992 // Both are always bigger than a word; assume flagIndir. 993 return *(*unsafe.Pointer)(v.ptr) == nil 994 } 995 panic(&ValueError{"reflect.Value.IsNil", v.kind()}) 996 } 997 998 // IsValid reports whether v represents a value. 999 // It returns false if v is the zero Value. 1000 // If IsValid returns false, all other methods except String panic. 1001 // Most functions and methods never return an invalid value. 1002 // If one does, its documentation states the conditions explicitly. 1003 func (v Value) IsValid() bool { 1004 return v.flag != 0 1005 } 1006 1007 // Kind returns v's Kind. 1008 // If v is the zero Value (IsValid returns false), Kind returns Invalid. 1009 func (v Value) Kind() Kind { 1010 return v.kind() 1011 } 1012 1013 // Len returns v's length. 1014 // It panics if v's Kind is not Array, Chan, Map, Slice, or String. 1015 func (v Value) Len() int { 1016 k := v.kind() 1017 switch k { 1018 case Array: 1019 tt := (*arrayType)(unsafe.Pointer(v.typ)) 1020 return int(tt.len) 1021 case Chan: 1022 return chanlen(v.pointer()) 1023 case Map: 1024 return maplen(v.pointer()) 1025 case Slice: 1026 // Slice is bigger than a word; assume flagIndir. 1027 return (*sliceHeader)(v.ptr).Len 1028 case String: 1029 // String is bigger than a word; assume flagIndir. 1030 return (*stringHeader)(v.ptr).Len 1031 } 1032 panic(&ValueError{"reflect.Value.Len", v.kind()}) 1033 } 1034 1035 // MapIndex returns the value associated with key in the map v. 1036 // It panics if v's Kind is not Map. 1037 // It returns the zero Value if key is not found in the map or if v represents a nil map. 1038 // As in Go, the key's value must be assignable to the map's key type. 1039 func (v Value) MapIndex(key Value) Value { 1040 v.mustBe(Map) 1041 tt := (*mapType)(unsafe.Pointer(v.typ)) 1042 1043 // Do not require key to be exported, so that DeepEqual 1044 // and other programs can use all the keys returned by 1045 // MapKeys as arguments to MapIndex. If either the map 1046 // or the key is unexported, though, the result will be 1047 // considered unexported. This is consistent with the 1048 // behavior for structs, which allow read but not write 1049 // of unexported fields. 1050 key = key.assignTo("reflect.Value.MapIndex", tt.key, nil) 1051 1052 var k unsafe.Pointer 1053 if key.flag&flagIndir != 0 { 1054 k = key.ptr 1055 } else { 1056 k = unsafe.Pointer(&key.ptr) 1057 } 1058 e := mapaccess(v.typ, v.pointer(), k) 1059 if e == nil { 1060 return Value{} 1061 } 1062 typ := tt.elem 1063 fl := (v.flag | key.flag) & flagRO 1064 fl |= flag(typ.Kind()) 1065 if ifaceIndir(typ) { 1066 // Copy result so future changes to the map 1067 // won't change the underlying value. 1068 c := unsafe_New(typ) 1069 typedmemmove(typ, c, e) 1070 return Value{typ, c, fl | flagIndir} 1071 } else { 1072 return Value{typ, *(*unsafe.Pointer)(e), fl} 1073 } 1074 } 1075 1076 // MapKeys returns a slice containing all the keys present in the map, 1077 // in unspecified order. 1078 // It panics if v's Kind is not Map. 1079 // It returns an empty slice if v represents a nil map. 1080 func (v Value) MapKeys() []Value { 1081 v.mustBe(Map) 1082 tt := (*mapType)(unsafe.Pointer(v.typ)) 1083 keyType := tt.key 1084 1085 fl := v.flag&flagRO | flag(keyType.Kind()) 1086 1087 m := v.pointer() 1088 mlen := int(0) 1089 if m != nil { 1090 mlen = maplen(m) 1091 } 1092 it := mapiterinit(v.typ, m) 1093 a := make([]Value, mlen) 1094 var i int 1095 for i = 0; i < len(a); i++ { 1096 key := mapiterkey(it) 1097 if key == nil { 1098 // Someone deleted an entry from the map since we 1099 // called maplen above. It's a data race, but nothing 1100 // we can do about it. 1101 break 1102 } 1103 if ifaceIndir(keyType) { 1104 // Copy result so future changes to the map 1105 // won't change the underlying value. 1106 c := unsafe_New(keyType) 1107 typedmemmove(keyType, c, key) 1108 a[i] = Value{keyType, c, fl | flagIndir} 1109 } else { 1110 a[i] = Value{keyType, *(*unsafe.Pointer)(key), fl} 1111 } 1112 mapiternext(it) 1113 } 1114 return a[:i] 1115 } 1116 1117 // Method returns a function value corresponding to v's i'th method. 1118 // The arguments to a Call on the returned function should not include 1119 // a receiver; the returned function will always use v as the receiver. 1120 // Method panics if i is out of range or if v is a nil interface value. 1121 func (v Value) Method(i int) Value { 1122 if v.typ == nil { 1123 panic(&ValueError{"reflect.Value.Method", Invalid}) 1124 } 1125 if v.flag&flagMethod != 0 || uint(i) >= uint(v.typ.NumMethod()) { 1126 panic("reflect: Method index out of range") 1127 } 1128 if v.typ.Kind() == Interface && v.IsNil() { 1129 panic("reflect: Method on nil interface value") 1130 } 1131 fl := v.flag & (flagStickyRO | flagIndir) // Clear flagEmbedRO 1132 fl |= flag(Func) 1133 fl |= flag(i)<<flagMethodShift | flagMethod 1134 return Value{v.typ, v.ptr, fl} 1135 } 1136 1137 // NumMethod returns the number of methods in the value's method set. 1138 func (v Value) NumMethod() int { 1139 if v.typ == nil { 1140 panic(&ValueError{"reflect.Value.NumMethod", Invalid}) 1141 } 1142 if v.flag&flagMethod != 0 { 1143 return 0 1144 } 1145 return v.typ.NumMethod() 1146 } 1147 1148 // MethodByName returns a function value corresponding to the method 1149 // of v with the given name. 1150 // The arguments to a Call on the returned function should not include 1151 // a receiver; the returned function will always use v as the receiver. 1152 // It returns the zero Value if no method was found. 1153 func (v Value) MethodByName(name string) Value { 1154 if v.typ == nil { 1155 panic(&ValueError{"reflect.Value.MethodByName", Invalid}) 1156 } 1157 if v.flag&flagMethod != 0 { 1158 return Value{} 1159 } 1160 m, ok := v.typ.MethodByName(name) 1161 if !ok { 1162 return Value{} 1163 } 1164 return v.Method(m.Index) 1165 } 1166 1167 // NumField returns the number of fields in the struct v. 1168 // It panics if v's Kind is not Struct. 1169 func (v Value) NumField() int { 1170 v.mustBe(Struct) 1171 tt := (*structType)(unsafe.Pointer(v.typ)) 1172 return len(tt.fields) 1173 } 1174 1175 // OverflowComplex reports whether the complex128 x cannot be represented by v's type. 1176 // It panics if v's Kind is not Complex64 or Complex128. 1177 func (v Value) OverflowComplex(x complex128) bool { 1178 k := v.kind() 1179 switch k { 1180 case Complex64: 1181 return overflowFloat32(real(x)) || overflowFloat32(imag(x)) 1182 case Complex128: 1183 return false 1184 } 1185 panic(&ValueError{"reflect.Value.OverflowComplex", v.kind()}) 1186 } 1187 1188 // OverflowFloat reports whether the float64 x cannot be represented by v's type. 1189 // It panics if v's Kind is not Float32 or Float64. 1190 func (v Value) OverflowFloat(x float64) bool { 1191 k := v.kind() 1192 switch k { 1193 case Float32: 1194 return overflowFloat32(x) 1195 case Float64: 1196 return false 1197 } 1198 panic(&ValueError{"reflect.Value.OverflowFloat", v.kind()}) 1199 } 1200 1201 func overflowFloat32(x float64) bool { 1202 if x < 0 { 1203 x = -x 1204 } 1205 return math.MaxFloat32 < x && x <= math.MaxFloat64 1206 } 1207 1208 // OverflowInt reports whether the int64 x cannot be represented by v's type. 1209 // It panics if v's Kind is not Int, Int8, int16, Int32, or Int64. 1210 func (v Value) OverflowInt(x int64) bool { 1211 k := v.kind() 1212 switch k { 1213 case Int, Int8, Int16, Int32, Int64: 1214 bitSize := v.typ.size * 8 1215 trunc := (x << (64 - bitSize)) >> (64 - bitSize) 1216 return x != trunc 1217 } 1218 panic(&ValueError{"reflect.Value.OverflowInt", v.kind()}) 1219 } 1220 1221 // OverflowUint reports whether the uint64 x cannot be represented by v's type. 1222 // It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64. 1223 func (v Value) OverflowUint(x uint64) bool { 1224 k := v.kind() 1225 switch k { 1226 case Uint, Uintptr, Uint8, Uint16, Uint32, Uint64: 1227 bitSize := v.typ.size * 8 1228 trunc := (x << (64 - bitSize)) >> (64 - bitSize) 1229 return x != trunc 1230 } 1231 panic(&ValueError{"reflect.Value.OverflowUint", v.kind()}) 1232 } 1233 1234 // Pointer returns v's value as a uintptr. 1235 // It returns uintptr instead of unsafe.Pointer so that 1236 // code using reflect cannot obtain unsafe.Pointers 1237 // without importing the unsafe package explicitly. 1238 // It panics if v's Kind is not Chan, Func, Map, Ptr, Slice, or UnsafePointer. 1239 // 1240 // If v's Kind is Func, the returned pointer is an underlying 1241 // code pointer, but not necessarily enough to identify a 1242 // single function uniquely. The only guarantee is that the 1243 // result is zero if and only if v is a nil func Value. 1244 // 1245 // If v's Kind is Slice, the returned pointer is to the first 1246 // element of the slice. If the slice is nil the returned value 1247 // is 0. If the slice is empty but non-nil the return value is non-zero. 1248 func (v Value) Pointer() uintptr { 1249 // TODO: deprecate 1250 k := v.kind() 1251 switch k { 1252 case Chan, Map, Ptr, UnsafePointer: 1253 return uintptr(v.pointer()) 1254 case Func: 1255 if v.flag&flagMethod != 0 { 1256 // As the doc comment says, the returned pointer is an 1257 // underlying code pointer but not necessarily enough to 1258 // identify a single function uniquely. All method expressions 1259 // created via reflect have the same underlying code pointer, 1260 // so their Pointers are equal. The function used here must 1261 // match the one used in makeMethodValue. 1262 f := methodValueCall 1263 return **(**uintptr)(unsafe.Pointer(&f)) 1264 } 1265 p := v.pointer() 1266 // Non-nil func value points at data block. 1267 // First word of data block is actual code. 1268 if p != nil { 1269 p = *(*unsafe.Pointer)(p) 1270 } 1271 return uintptr(p) 1272 1273 case Slice: 1274 return (*SliceHeader)(v.ptr).Data 1275 } 1276 panic(&ValueError{"reflect.Value.Pointer", v.kind()}) 1277 } 1278 1279 // Recv receives and returns a value from the channel v. 1280 // It panics if v's Kind is not Chan. 1281 // The receive blocks until a value is ready. 1282 // The boolean value ok is true if the value x corresponds to a send 1283 // on the channel, false if it is a zero value received because the channel is closed. 1284 func (v Value) Recv() (x Value, ok bool) { 1285 v.mustBe(Chan) 1286 v.mustBeExported() 1287 return v.recv(false) 1288 } 1289 1290 // internal recv, possibly non-blocking (nb). 1291 // v is known to be a channel. 1292 func (v Value) recv(nb bool) (val Value, ok bool) { 1293 tt := (*chanType)(unsafe.Pointer(v.typ)) 1294 if ChanDir(tt.dir)&RecvDir == 0 { 1295 panic("reflect: recv on send-only channel") 1296 } 1297 t := tt.elem 1298 val = Value{t, nil, flag(t.Kind())} 1299 var p unsafe.Pointer 1300 if ifaceIndir(t) { 1301 p = unsafe_New(t) 1302 val.ptr = p 1303 val.flag |= flagIndir 1304 } else { 1305 p = unsafe.Pointer(&val.ptr) 1306 } 1307 selected, ok := chanrecv(v.pointer(), nb, p) 1308 if !selected { 1309 val = Value{} 1310 } 1311 return 1312 } 1313 1314 // Send sends x on the channel v. 1315 // It panics if v's kind is not Chan or if x's type is not the same type as v's element type. 1316 // As in Go, x's value must be assignable to the channel's element type. 1317 func (v Value) Send(x Value) { 1318 v.mustBe(Chan) 1319 v.mustBeExported() 1320 v.send(x, false) 1321 } 1322 1323 // internal send, possibly non-blocking. 1324 // v is known to be a channel. 1325 func (v Value) send(x Value, nb bool) (selected bool) { 1326 tt := (*chanType)(unsafe.Pointer(v.typ)) 1327 if ChanDir(tt.dir)&SendDir == 0 { 1328 panic("reflect: send on recv-only channel") 1329 } 1330 x.mustBeExported() 1331 x = x.assignTo("reflect.Value.Send", tt.elem, nil) 1332 var p unsafe.Pointer 1333 if x.flag&flagIndir != 0 { 1334 p = x.ptr 1335 } else { 1336 p = unsafe.Pointer(&x.ptr) 1337 } 1338 return chansend(v.pointer(), p, nb) 1339 } 1340 1341 // Set assigns x to the value v. 1342 // It panics if CanSet returns false. 1343 // As in Go, x's value must be assignable to v's type. 1344 func (v Value) Set(x Value) { 1345 v.mustBeAssignable() 1346 x.mustBeExported() // do not let unexported x leak 1347 var target unsafe.Pointer 1348 if v.kind() == Interface { 1349 target = v.ptr 1350 } 1351 x = x.assignTo("reflect.Set", v.typ, target) 1352 if x.flag&flagIndir != 0 { 1353 typedmemmove(v.typ, v.ptr, x.ptr) 1354 } else { 1355 *(*unsafe.Pointer)(v.ptr) = x.ptr 1356 } 1357 } 1358 1359 // SetBool sets v's underlying value. 1360 // It panics if v's Kind is not Bool or if CanSet() is false. 1361 func (v Value) SetBool(x bool) { 1362 v.mustBeAssignable() 1363 v.mustBe(Bool) 1364 *(*bool)(v.ptr) = x 1365 } 1366 1367 // SetBytes sets v's underlying value. 1368 // It panics if v's underlying value is not a slice of bytes. 1369 func (v Value) SetBytes(x []byte) { 1370 v.mustBeAssignable() 1371 v.mustBe(Slice) 1372 if v.typ.Elem().Kind() != Uint8 { 1373 panic("reflect.Value.SetBytes of non-byte slice") 1374 } 1375 *(*[]byte)(v.ptr) = x 1376 } 1377 1378 // setRunes sets v's underlying value. 1379 // It panics if v's underlying value is not a slice of runes (int32s). 1380 func (v Value) setRunes(x []rune) { 1381 v.mustBeAssignable() 1382 v.mustBe(Slice) 1383 if v.typ.Elem().Kind() != Int32 { 1384 panic("reflect.Value.setRunes of non-rune slice") 1385 } 1386 *(*[]rune)(v.ptr) = x 1387 } 1388 1389 // SetComplex sets v's underlying value to x. 1390 // It panics if v's Kind is not Complex64 or Complex128, or if CanSet() is false. 1391 func (v Value) SetComplex(x complex128) { 1392 v.mustBeAssignable() 1393 switch k := v.kind(); k { 1394 default: 1395 panic(&ValueError{"reflect.Value.SetComplex", v.kind()}) 1396 case Complex64: 1397 *(*complex64)(v.ptr) = complex64(x) 1398 case Complex128: 1399 *(*complex128)(v.ptr) = x 1400 } 1401 } 1402 1403 // SetFloat sets v's underlying value to x. 1404 // It panics if v's Kind is not Float32 or Float64, or if CanSet() is false. 1405 func (v Value) SetFloat(x float64) { 1406 v.mustBeAssignable() 1407 switch k := v.kind(); k { 1408 default: 1409 panic(&ValueError{"reflect.Value.SetFloat", v.kind()}) 1410 case Float32: 1411 *(*float32)(v.ptr) = float32(x) 1412 case Float64: 1413 *(*float64)(v.ptr) = x 1414 } 1415 } 1416 1417 // SetInt sets v's underlying value to x. 1418 // It panics if v's Kind is not Int, Int8, Int16, Int32, or Int64, or if CanSet() is false. 1419 func (v Value) SetInt(x int64) { 1420 v.mustBeAssignable() 1421 switch k := v.kind(); k { 1422 default: 1423 panic(&ValueError{"reflect.Value.SetInt", v.kind()}) 1424 case Int: 1425 *(*int)(v.ptr) = int(x) 1426 case Int8: 1427 *(*int8)(v.ptr) = int8(x) 1428 case Int16: 1429 *(*int16)(v.ptr) = int16(x) 1430 case Int32: 1431 *(*int32)(v.ptr) = int32(x) 1432 case Int64: 1433 *(*int64)(v.ptr) = x 1434 } 1435 } 1436 1437 // SetLen sets v's length to n. 1438 // It panics if v's Kind is not Slice or if n is negative or 1439 // greater than the capacity of the slice. 1440 func (v Value) SetLen(n int) { 1441 v.mustBeAssignable() 1442 v.mustBe(Slice) 1443 s := (*sliceHeader)(v.ptr) 1444 if uint(n) > uint(s.Cap) { 1445 panic("reflect: slice length out of range in SetLen") 1446 } 1447 s.Len = n 1448 } 1449 1450 // SetCap sets v's capacity to n. 1451 // It panics if v's Kind is not Slice or if n is smaller than the length or 1452 // greater than the capacity of the slice. 1453 func (v Value) SetCap(n int) { 1454 v.mustBeAssignable() 1455 v.mustBe(Slice) 1456 s := (*sliceHeader)(v.ptr) 1457 if n < s.Len || n > s.Cap { 1458 panic("reflect: slice capacity out of range in SetCap") 1459 } 1460 s.Cap = n 1461 } 1462 1463 // SetMapIndex sets the value associated with key in the map v to val. 1464 // It panics if v's Kind is not Map. 1465 // If val is the zero Value, SetMapIndex deletes the key from the map. 1466 // Otherwise if v holds a nil map, SetMapIndex will panic. 1467 // As in Go, key's value must be assignable to the map's key type, 1468 // and val's value must be assignable to the map's value type. 1469 func (v Value) SetMapIndex(key, val Value) { 1470 v.mustBe(Map) 1471 v.mustBeExported() 1472 key.mustBeExported() 1473 tt := (*mapType)(unsafe.Pointer(v.typ)) 1474 key = key.assignTo("reflect.Value.SetMapIndex", tt.key, nil) 1475 var k unsafe.Pointer 1476 if key.flag&flagIndir != 0 { 1477 k = key.ptr 1478 } else { 1479 k = unsafe.Pointer(&key.ptr) 1480 } 1481 if val.typ == nil { 1482 mapdelete(v.typ, v.pointer(), k) 1483 return 1484 } 1485 val.mustBeExported() 1486 val = val.assignTo("reflect.Value.SetMapIndex", tt.elem, nil) 1487 var e unsafe.Pointer 1488 if val.flag&flagIndir != 0 { 1489 e = val.ptr 1490 } else { 1491 e = unsafe.Pointer(&val.ptr) 1492 } 1493 mapassign(v.typ, v.pointer(), k, e) 1494 } 1495 1496 // SetUint sets v's underlying value to x. 1497 // It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64, or if CanSet() is false. 1498 func (v Value) SetUint(x uint64) { 1499 v.mustBeAssignable() 1500 switch k := v.kind(); k { 1501 default: 1502 panic(&ValueError{"reflect.Value.SetUint", v.kind()}) 1503 case Uint: 1504 *(*uint)(v.ptr) = uint(x) 1505 case Uint8: 1506 *(*uint8)(v.ptr) = uint8(x) 1507 case Uint16: 1508 *(*uint16)(v.ptr) = uint16(x) 1509 case Uint32: 1510 *(*uint32)(v.ptr) = uint32(x) 1511 case Uint64: 1512 *(*uint64)(v.ptr) = x 1513 case Uintptr: 1514 *(*uintptr)(v.ptr) = uintptr(x) 1515 } 1516 } 1517 1518 // SetPointer sets the unsafe.Pointer value v to x. 1519 // It panics if v's Kind is not UnsafePointer. 1520 func (v Value) SetPointer(x unsafe.Pointer) { 1521 v.mustBeAssignable() 1522 v.mustBe(UnsafePointer) 1523 *(*unsafe.Pointer)(v.ptr) = x 1524 } 1525 1526 // SetString sets v's underlying value to x. 1527 // It panics if v's Kind is not String or if CanSet() is false. 1528 func (v Value) SetString(x string) { 1529 v.mustBeAssignable() 1530 v.mustBe(String) 1531 *(*string)(v.ptr) = x 1532 } 1533 1534 // Slice returns v[i:j]. 1535 // It panics if v's Kind is not Array, Slice or String, or if v is an unaddressable array, 1536 // or if the indexes are out of bounds. 1537 func (v Value) Slice(i, j int) Value { 1538 var ( 1539 cap int 1540 typ *sliceType 1541 base unsafe.Pointer 1542 ) 1543 switch kind := v.kind(); kind { 1544 default: 1545 panic(&ValueError{"reflect.Value.Slice", v.kind()}) 1546 1547 case Array: 1548 if v.flag&flagAddr == 0 { 1549 panic("reflect.Value.Slice: slice of unaddressable array") 1550 } 1551 tt := (*arrayType)(unsafe.Pointer(v.typ)) 1552 cap = int(tt.len) 1553 typ = (*sliceType)(unsafe.Pointer(tt.slice)) 1554 base = v.ptr 1555 1556 case Slice: 1557 typ = (*sliceType)(unsafe.Pointer(v.typ)) 1558 s := (*sliceHeader)(v.ptr) 1559 base = s.Data 1560 cap = s.Cap 1561 1562 case String: 1563 s := (*stringHeader)(v.ptr) 1564 if i < 0 || j < i || j > s.Len { 1565 panic("reflect.Value.Slice: string slice index out of bounds") 1566 } 1567 t := stringHeader{arrayAt(s.Data, i, 1), j - i} 1568 return Value{v.typ, unsafe.Pointer(&t), v.flag} 1569 } 1570 1571 if i < 0 || j < i || j > cap { 1572 panic("reflect.Value.Slice: slice index out of bounds") 1573 } 1574 1575 // Declare slice so that gc can see the base pointer in it. 1576 var x []unsafe.Pointer 1577 1578 // Reinterpret as *sliceHeader to edit. 1579 s := (*sliceHeader)(unsafe.Pointer(&x)) 1580 s.Len = j - i 1581 s.Cap = cap - i 1582 if cap-i > 0 { 1583 s.Data = arrayAt(base, i, typ.elem.Size()) 1584 } else { 1585 // do not advance pointer, to avoid pointing beyond end of slice 1586 s.Data = base 1587 } 1588 1589 fl := v.flag&flagRO | flagIndir | flag(Slice) 1590 return Value{typ.common(), unsafe.Pointer(&x), fl} 1591 } 1592 1593 // Slice3 is the 3-index form of the slice operation: it returns v[i:j:k]. 1594 // It panics if v's Kind is not Array or Slice, or if v is an unaddressable array, 1595 // or if the indexes are out of bounds. 1596 func (v Value) Slice3(i, j, k int) Value { 1597 var ( 1598 cap int 1599 typ *sliceType 1600 base unsafe.Pointer 1601 ) 1602 switch kind := v.kind(); kind { 1603 default: 1604 panic(&ValueError{"reflect.Value.Slice3", v.kind()}) 1605 1606 case Array: 1607 if v.flag&flagAddr == 0 { 1608 panic("reflect.Value.Slice3: slice of unaddressable array") 1609 } 1610 tt := (*arrayType)(unsafe.Pointer(v.typ)) 1611 cap = int(tt.len) 1612 typ = (*sliceType)(unsafe.Pointer(tt.slice)) 1613 base = v.ptr 1614 1615 case Slice: 1616 typ = (*sliceType)(unsafe.Pointer(v.typ)) 1617 s := (*sliceHeader)(v.ptr) 1618 base = s.Data 1619 cap = s.Cap 1620 } 1621 1622 if i < 0 || j < i || k < j || k > cap { 1623 panic("reflect.Value.Slice3: slice index out of bounds") 1624 } 1625 1626 // Declare slice so that the garbage collector 1627 // can see the base pointer in it. 1628 var x []unsafe.Pointer 1629 1630 // Reinterpret as *sliceHeader to edit. 1631 s := (*sliceHeader)(unsafe.Pointer(&x)) 1632 s.Len = j - i 1633 s.Cap = k - i 1634 if k-i > 0 { 1635 s.Data = arrayAt(base, i, typ.elem.Size()) 1636 } else { 1637 // do not advance pointer, to avoid pointing beyond end of slice 1638 s.Data = base 1639 } 1640 1641 fl := v.flag&flagRO | flagIndir | flag(Slice) 1642 return Value{typ.common(), unsafe.Pointer(&x), fl} 1643 } 1644 1645 // String returns the string v's underlying value, as a string. 1646 // String is a special case because of Go's String method convention. 1647 // Unlike the other getters, it does not panic if v's Kind is not String. 1648 // Instead, it returns a string of the form "<T value>" where T is v's type. 1649 // The fmt package treats Values specially. It does not call their String 1650 // method implicitly but instead prints the concrete values they hold. 1651 func (v Value) String() string { 1652 switch k := v.kind(); k { 1653 case Invalid: 1654 return "<invalid Value>" 1655 case String: 1656 return *(*string)(v.ptr) 1657 } 1658 // If you call String on a reflect.Value of other type, it's better to 1659 // print something than to panic. Useful in debugging. 1660 return "<" + v.Type().String() + " Value>" 1661 } 1662 1663 // TryRecv attempts to receive a value from the channel v but will not block. 1664 // It panics if v's Kind is not Chan. 1665 // If the receive delivers a value, x is the transferred value and ok is true. 1666 // If the receive cannot finish without blocking, x is the zero Value and ok is false. 1667 // If the channel is closed, x is the zero value for the channel's element type and ok is false. 1668 func (v Value) TryRecv() (x Value, ok bool) { 1669 v.mustBe(Chan) 1670 v.mustBeExported() 1671 return v.recv(true) 1672 } 1673 1674 // TrySend attempts to send x on the channel v but will not block. 1675 // It panics if v's Kind is not Chan. 1676 // It reports whether the value was sent. 1677 // As in Go, x's value must be assignable to the channel's element type. 1678 func (v Value) TrySend(x Value) bool { 1679 v.mustBe(Chan) 1680 v.mustBeExported() 1681 return v.send(x, true) 1682 } 1683 1684 // Type returns v's type. 1685 func (v Value) Type() Type { 1686 f := v.flag 1687 if f == 0 { 1688 panic(&ValueError{"reflect.Value.Type", Invalid}) 1689 } 1690 if f&flagMethod == 0 { 1691 // Easy case 1692 return v.typ 1693 } 1694 1695 // Method value. 1696 // v.typ describes the receiver, not the method type. 1697 i := int(v.flag) >> flagMethodShift 1698 if v.typ.Kind() == Interface { 1699 // Method on interface. 1700 tt := (*interfaceType)(unsafe.Pointer(v.typ)) 1701 if uint(i) >= uint(len(tt.methods)) { 1702 panic("reflect: internal error: invalid method index") 1703 } 1704 m := &tt.methods[i] 1705 return v.typ.typeOff(m.typ) 1706 } 1707 // Method on concrete type. 1708 ut := v.typ.uncommon() 1709 if ut == nil || uint(i) >= uint(ut.mcount) { 1710 panic("reflect: internal error: invalid method index") 1711 } 1712 m := ut.methods()[i] 1713 return v.typ.typeOff(m.mtyp) 1714 } 1715 1716 // Uint returns v's underlying value, as a uint64. 1717 // It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64. 1718 func (v Value) Uint() uint64 { 1719 k := v.kind() 1720 p := v.ptr 1721 switch k { 1722 case Uint: 1723 return uint64(*(*uint)(p)) 1724 case Uint8: 1725 return uint64(*(*uint8)(p)) 1726 case Uint16: 1727 return uint64(*(*uint16)(p)) 1728 case Uint32: 1729 return uint64(*(*uint32)(p)) 1730 case Uint64: 1731 return *(*uint64)(p) 1732 case Uintptr: 1733 return uint64(*(*uintptr)(p)) 1734 } 1735 panic(&ValueError{"reflect.Value.Uint", v.kind()}) 1736 } 1737 1738 // UnsafeAddr returns a pointer to v's data. 1739 // It is for advanced clients that also import the "unsafe" package. 1740 // It panics if v is not addressable. 1741 func (v Value) UnsafeAddr() uintptr { 1742 // TODO: deprecate 1743 if v.typ == nil { 1744 panic(&ValueError{"reflect.Value.UnsafeAddr", Invalid}) 1745 } 1746 if v.flag&flagAddr == 0 { 1747 panic("reflect.Value.UnsafeAddr of unaddressable value") 1748 } 1749 return uintptr(v.ptr) 1750 } 1751 1752 // StringHeader is the runtime representation of a string. 1753 // It cannot be used safely or portably and its representation may 1754 // change in a later release. 1755 // Moreover, the Data field is not sufficient to guarantee the data 1756 // it references will not be garbage collected, so programs must keep 1757 // a separate, correctly typed pointer to the underlying data. 1758 type StringHeader struct { 1759 Data uintptr 1760 Len int 1761 } 1762 1763 // stringHeader is a safe version of StringHeader used within this package. 1764 type stringHeader struct { 1765 Data unsafe.Pointer 1766 Len int 1767 } 1768 1769 // SliceHeader is the runtime representation of a slice. 1770 // It cannot be used safely or portably and its representation may 1771 // change in a later release. 1772 // Moreover, the Data field is not sufficient to guarantee the data 1773 // it references will not be garbage collected, so programs must keep 1774 // a separate, correctly typed pointer to the underlying data. 1775 type SliceHeader struct { 1776 Data uintptr 1777 Len int 1778 Cap int 1779 } 1780 1781 // sliceHeader is a safe version of SliceHeader used within this package. 1782 type sliceHeader struct { 1783 Data unsafe.Pointer 1784 Len int 1785 Cap int 1786 } 1787 1788 func typesMustMatch(what string, t1, t2 Type) { 1789 if t1 != t2 { 1790 panic(what + ": " + t1.String() + " != " + t2.String()) 1791 } 1792 } 1793 1794 // arrayAt returns the i-th element of p, a C-array whose elements are 1795 // eltSize wide (in bytes). 1796 func arrayAt(p unsafe.Pointer, i int, eltSize uintptr) unsafe.Pointer { 1797 return unsafe.Pointer(uintptr(p) + uintptr(i)*eltSize) 1798 } 1799 1800 // grow grows the slice s so that it can hold extra more values, allocating 1801 // more capacity if needed. It also returns the old and new slice lengths. 1802 func grow(s Value, extra int) (Value, int, int) { 1803 i0 := s.Len() 1804 i1 := i0 + extra 1805 if i1 < i0 { 1806 panic("reflect.Append: slice overflow") 1807 } 1808 m := s.Cap() 1809 if i1 <= m { 1810 return s.Slice(0, i1), i0, i1 1811 } 1812 if m == 0 { 1813 m = extra 1814 } else { 1815 for m < i1 { 1816 if i0 < 1024 { 1817 m += m 1818 } else { 1819 m += m / 4 1820 } 1821 } 1822 } 1823 t := MakeSlice(s.Type(), i1, m) 1824 Copy(t, s) 1825 return t, i0, i1 1826 } 1827 1828 // Append appends the values x to a slice s and returns the resulting slice. 1829 // As in Go, each x's value must be assignable to the slice's element type. 1830 func Append(s Value, x ...Value) Value { 1831 s.mustBe(Slice) 1832 s, i0, i1 := grow(s, len(x)) 1833 for i, j := i0, 0; i < i1; i, j = i+1, j+1 { 1834 s.Index(i).Set(x[j]) 1835 } 1836 return s 1837 } 1838 1839 // AppendSlice appends a slice t to a slice s and returns the resulting slice. 1840 // The slices s and t must have the same element type. 1841 func AppendSlice(s, t Value) Value { 1842 s.mustBe(Slice) 1843 t.mustBe(Slice) 1844 typesMustMatch("reflect.AppendSlice", s.Type().Elem(), t.Type().Elem()) 1845 s, i0, i1 := grow(s, t.Len()) 1846 Copy(s.Slice(i0, i1), t) 1847 return s 1848 } 1849 1850 // Copy copies the contents of src into dst until either 1851 // dst has been filled or src has been exhausted. 1852 // It returns the number of elements copied. 1853 // Dst and src each must have kind Slice or Array, and 1854 // dst and src must have the same element type. 1855 func Copy(dst, src Value) int { 1856 dk := dst.kind() 1857 if dk != Array && dk != Slice { 1858 panic(&ValueError{"reflect.Copy", dk}) 1859 } 1860 if dk == Array { 1861 dst.mustBeAssignable() 1862 } 1863 dst.mustBeExported() 1864 1865 sk := src.kind() 1866 if sk != Array && sk != Slice { 1867 panic(&ValueError{"reflect.Copy", sk}) 1868 } 1869 src.mustBeExported() 1870 1871 de := dst.typ.Elem() 1872 se := src.typ.Elem() 1873 typesMustMatch("reflect.Copy", de, se) 1874 1875 var ds, ss sliceHeader 1876 if dk == Array { 1877 ds.Data = dst.ptr 1878 ds.Len = dst.Len() 1879 ds.Cap = ds.Len 1880 } else { 1881 ds = *(*sliceHeader)(dst.ptr) 1882 } 1883 if sk == Array { 1884 ss.Data = src.ptr 1885 ss.Len = src.Len() 1886 ss.Cap = ss.Len 1887 } else { 1888 ss = *(*sliceHeader)(src.ptr) 1889 } 1890 1891 return typedslicecopy(de.common(), ds, ss) 1892 } 1893 1894 // A runtimeSelect is a single case passed to rselect. 1895 // This must match ../runtime/select.go:/runtimeSelect 1896 type runtimeSelect struct { 1897 dir SelectDir // SelectSend, SelectRecv or SelectDefault 1898 typ *rtype // channel type 1899 ch unsafe.Pointer // channel 1900 val unsafe.Pointer // ptr to data (SendDir) or ptr to receive buffer (RecvDir) 1901 } 1902 1903 // rselect runs a select. It returns the index of the chosen case. 1904 // If the case was a receive, val is filled in with the received value. 1905 // The conventional OK bool indicates whether the receive corresponds 1906 // to a sent value. 1907 //go:noescape 1908 func rselect([]runtimeSelect) (chosen int, recvOK bool) 1909 1910 // A SelectDir describes the communication direction of a select case. 1911 type SelectDir int 1912 1913 // NOTE: These values must match ../runtime/select.go:/selectDir. 1914 1915 const ( 1916 _ SelectDir = iota 1917 SelectSend // case Chan <- Send 1918 SelectRecv // case <-Chan: 1919 SelectDefault // default 1920 ) 1921 1922 // A SelectCase describes a single case in a select operation. 1923 // The kind of case depends on Dir, the communication direction. 1924 // 1925 // If Dir is SelectDefault, the case represents a default case. 1926 // Chan and Send must be zero Values. 1927 // 1928 // If Dir is SelectSend, the case represents a send operation. 1929 // Normally Chan's underlying value must be a channel, and Send's underlying value must be 1930 // assignable to the channel's element type. As a special case, if Chan is a zero Value, 1931 // then the case is ignored, and the field Send will also be ignored and may be either zero 1932 // or non-zero. 1933 // 1934 // If Dir is SelectRecv, the case represents a receive operation. 1935 // Normally Chan's underlying value must be a channel and Send must be a zero Value. 1936 // If Chan is a zero Value, then the case is ignored, but Send must still be a zero Value. 1937 // When a receive operation is selected, the received Value is returned by Select. 1938 // 1939 type SelectCase struct { 1940 Dir SelectDir // direction of case 1941 Chan Value // channel to use (for send or receive) 1942 Send Value // value to send (for send) 1943 } 1944 1945 // Select executes a select operation described by the list of cases. 1946 // Like the Go select statement, it blocks until at least one of the cases 1947 // can proceed, makes a uniform pseudo-random choice, 1948 // and then executes that case. It returns the index of the chosen case 1949 // and, if that case was a receive operation, the value received and a 1950 // boolean indicating whether the value corresponds to a send on the channel 1951 // (as opposed to a zero value received because the channel is closed). 1952 func Select(cases []SelectCase) (chosen int, recv Value, recvOK bool) { 1953 // NOTE: Do not trust that caller is not modifying cases data underfoot. 1954 // The range is safe because the caller cannot modify our copy of the len 1955 // and each iteration makes its own copy of the value c. 1956 runcases := make([]runtimeSelect, len(cases)) 1957 haveDefault := false 1958 for i, c := range cases { 1959 rc := &runcases[i] 1960 rc.dir = c.Dir 1961 switch c.Dir { 1962 default: 1963 panic("reflect.Select: invalid Dir") 1964 1965 case SelectDefault: // default 1966 if haveDefault { 1967 panic("reflect.Select: multiple default cases") 1968 } 1969 haveDefault = true 1970 if c.Chan.IsValid() { 1971 panic("reflect.Select: default case has Chan value") 1972 } 1973 if c.Send.IsValid() { 1974 panic("reflect.Select: default case has Send value") 1975 } 1976 1977 case SelectSend: 1978 ch := c.Chan 1979 if !ch.IsValid() { 1980 break 1981 } 1982 ch.mustBe(Chan) 1983 ch.mustBeExported() 1984 tt := (*chanType)(unsafe.Pointer(ch.typ)) 1985 if ChanDir(tt.dir)&SendDir == 0 { 1986 panic("reflect.Select: SendDir case using recv-only channel") 1987 } 1988 rc.ch = ch.pointer() 1989 rc.typ = &tt.rtype 1990 v := c.Send 1991 if !v.IsValid() { 1992 panic("reflect.Select: SendDir case missing Send value") 1993 } 1994 v.mustBeExported() 1995 v = v.assignTo("reflect.Select", tt.elem, nil) 1996 if v.flag&flagIndir != 0 { 1997 rc.val = v.ptr 1998 } else { 1999 rc.val = unsafe.Pointer(&v.ptr) 2000 } 2001 2002 case SelectRecv: 2003 if c.Send.IsValid() { 2004 panic("reflect.Select: RecvDir case has Send value") 2005 } 2006 ch := c.Chan 2007 if !ch.IsValid() { 2008 break 2009 } 2010 ch.mustBe(Chan) 2011 ch.mustBeExported() 2012 tt := (*chanType)(unsafe.Pointer(ch.typ)) 2013 if ChanDir(tt.dir)&RecvDir == 0 { 2014 panic("reflect.Select: RecvDir case using send-only channel") 2015 } 2016 rc.ch = ch.pointer() 2017 rc.typ = &tt.rtype 2018 rc.val = unsafe_New(tt.elem) 2019 } 2020 } 2021 2022 chosen, recvOK = rselect(runcases) 2023 if runcases[chosen].dir == SelectRecv { 2024 tt := (*chanType)(unsafe.Pointer(runcases[chosen].typ)) 2025 t := tt.elem 2026 p := runcases[chosen].val 2027 fl := flag(t.Kind()) 2028 if ifaceIndir(t) { 2029 recv = Value{t, p, fl | flagIndir} 2030 } else { 2031 recv = Value{t, *(*unsafe.Pointer)(p), fl} 2032 } 2033 } 2034 return chosen, recv, recvOK 2035 } 2036 2037 /* 2038 * constructors 2039 */ 2040 2041 // implemented in package runtime 2042 func unsafe_New(*rtype) unsafe.Pointer 2043 func unsafe_NewArray(*rtype, int) unsafe.Pointer 2044 2045 // MakeSlice creates a new zero-initialized slice value 2046 // for the specified slice type, length, and capacity. 2047 func MakeSlice(typ Type, len, cap int) Value { 2048 if typ.Kind() != Slice { 2049 panic("reflect.MakeSlice of non-slice type") 2050 } 2051 if len < 0 { 2052 panic("reflect.MakeSlice: negative len") 2053 } 2054 if cap < 0 { 2055 panic("reflect.MakeSlice: negative cap") 2056 } 2057 if len > cap { 2058 panic("reflect.MakeSlice: len > cap") 2059 } 2060 2061 s := sliceHeader{unsafe_NewArray(typ.Elem().(*rtype), cap), len, cap} 2062 return Value{typ.common(), unsafe.Pointer(&s), flagIndir | flag(Slice)} 2063 } 2064 2065 // MakeChan creates a new channel with the specified type and buffer size. 2066 func MakeChan(typ Type, buffer int) Value { 2067 if typ.Kind() != Chan { 2068 panic("reflect.MakeChan of non-chan type") 2069 } 2070 if buffer < 0 { 2071 panic("reflect.MakeChan: negative buffer size") 2072 } 2073 if typ.ChanDir() != BothDir { 2074 panic("reflect.MakeChan: unidirectional channel type") 2075 } 2076 ch := makechan(typ.(*rtype), uint64(buffer)) 2077 return Value{typ.common(), ch, flag(Chan)} 2078 } 2079 2080 // MakeMap creates a new map with the specified type. 2081 func MakeMap(typ Type) Value { 2082 return MakeMapWithSize(typ, 0) 2083 } 2084 2085 // MakeMapWithSize creates a new map with the specified type and initial capacity. 2086 func MakeMapWithSize(typ Type, cap int) Value { 2087 if typ.Kind() != Map { 2088 panic("reflect.MakeMapWithSize of non-map type") 2089 } 2090 m := makemap(typ.(*rtype), cap) 2091 return Value{typ.common(), m, flag(Map)} 2092 } 2093 2094 // Indirect returns the value that v points to. 2095 // If v is a nil pointer, Indirect returns a zero Value. 2096 // If v is not a pointer, Indirect returns v. 2097 func Indirect(v Value) Value { 2098 if v.Kind() != Ptr { 2099 return v 2100 } 2101 return v.Elem() 2102 } 2103 2104 // ValueOf returns a new Value initialized to the concrete value 2105 // stored in the interface i. ValueOf(nil) returns the zero Value. 2106 func ValueOf(i interface{}) Value { 2107 if i == nil { 2108 return Value{} 2109 } 2110 2111 // TODO: Maybe allow contents of a Value to live on the stack. 2112 // For now we make the contents always escape to the heap. It 2113 // makes life easier in a few places (see chanrecv/mapassign 2114 // comment below). 2115 escapes(i) 2116 2117 return unpackEface(i) 2118 } 2119 2120 // Zero returns a Value representing the zero value for the specified type. 2121 // The result is different from the zero value of the Value struct, 2122 // which represents no value at all. 2123 // For example, Zero(TypeOf(42)) returns a Value with Kind Int and value 0. 2124 // The returned value is neither addressable nor settable. 2125 func Zero(typ Type) Value { 2126 if typ == nil { 2127 panic("reflect: Zero(nil)") 2128 } 2129 t := typ.common() 2130 fl := flag(t.Kind()) 2131 if ifaceIndir(t) { 2132 return Value{t, unsafe_New(typ.(*rtype)), fl | flagIndir} 2133 } 2134 return Value{t, nil, fl} 2135 } 2136 2137 // New returns a Value representing a pointer to a new zero value 2138 // for the specified type. That is, the returned Value's Type is PtrTo(typ). 2139 func New(typ Type) Value { 2140 if typ == nil { 2141 panic("reflect: New(nil)") 2142 } 2143 ptr := unsafe_New(typ.(*rtype)) 2144 fl := flag(Ptr) 2145 return Value{typ.common().ptrTo(), ptr, fl} 2146 } 2147 2148 // NewAt returns a Value representing a pointer to a value of the 2149 // specified type, using p as that pointer. 2150 func NewAt(typ Type, p unsafe.Pointer) Value { 2151 fl := flag(Ptr) 2152 return Value{typ.common().ptrTo(), p, fl} 2153 } 2154 2155 // assignTo returns a value v that can be assigned directly to typ. 2156 // It panics if v is not assignable to typ. 2157 // For a conversion to an interface type, target is a suggested scratch space to use. 2158 func (v Value) assignTo(context string, dst *rtype, target unsafe.Pointer) Value { 2159 if v.flag&flagMethod != 0 { 2160 v = makeMethodValue(context, v) 2161 } 2162 2163 switch { 2164 case directlyAssignable(dst, v.typ): 2165 // Overwrite type so that they match. 2166 // Same memory layout, so no harm done. 2167 fl := v.flag & (flagRO | flagAddr | flagIndir) 2168 fl |= flag(dst.Kind()) 2169 return Value{dst, v.ptr, fl} 2170 2171 case implements(dst, v.typ): 2172 if target == nil { 2173 target = unsafe_New(dst) 2174 } 2175 x := valueInterface(v, false) 2176 if dst.NumMethod() == 0 { 2177 *(*interface{})(target) = x 2178 } else { 2179 ifaceE2I(dst, x, target) 2180 } 2181 return Value{dst, target, flagIndir | flag(Interface)} 2182 } 2183 2184 // Failed. 2185 panic(context + ": value of type " + v.typ.String() + " is not assignable to type " + dst.String()) 2186 } 2187 2188 // Convert returns the value v converted to type t. 2189 // If the usual Go conversion rules do not allow conversion 2190 // of the value v to type t, Convert panics. 2191 func (v Value) Convert(t Type) Value { 2192 if v.flag&flagMethod != 0 { 2193 v = makeMethodValue("Convert", v) 2194 } 2195 op := convertOp(t.common(), v.typ) 2196 if op == nil { 2197 panic("reflect.Value.Convert: value of type " + v.typ.String() + " cannot be converted to type " + t.String()) 2198 } 2199 return op(v, t) 2200 } 2201 2202 // convertOp returns the function to convert a value of type src 2203 // to a value of type dst. If the conversion is illegal, convertOp returns nil. 2204 func convertOp(dst, src *rtype) func(Value, Type) Value { 2205 switch src.Kind() { 2206 case Int, Int8, Int16, Int32, Int64: 2207 switch dst.Kind() { 2208 case Int, Int8, Int16, Int32, Int64, Uint, Uint8, Uint16, Uint32, Uint64, Uintptr: 2209 return cvtInt 2210 case Float32, Float64: 2211 return cvtIntFloat 2212 case String: 2213 return cvtIntString 2214 } 2215 2216 case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr: 2217 switch dst.Kind() { 2218 case Int, Int8, Int16, Int32, Int64, Uint, Uint8, Uint16, Uint32, Uint64, Uintptr: 2219 return cvtUint 2220 case Float32, Float64: 2221 return cvtUintFloat 2222 case String: 2223 return cvtUintString 2224 } 2225 2226 case Float32, Float64: 2227 switch dst.Kind() { 2228 case Int, Int8, Int16, Int32, Int64: 2229 return cvtFloatInt 2230 case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr: 2231 return cvtFloatUint 2232 case Float32, Float64: 2233 return cvtFloat 2234 } 2235 2236 case Complex64, Complex128: 2237 switch dst.Kind() { 2238 case Complex64, Complex128: 2239 return cvtComplex 2240 } 2241 2242 case String: 2243 if dst.Kind() == Slice && dst.Elem().PkgPath() == "" { 2244 switch dst.Elem().Kind() { 2245 case Uint8: 2246 return cvtStringBytes 2247 case Int32: 2248 return cvtStringRunes 2249 } 2250 } 2251 2252 case Slice: 2253 if dst.Kind() == String && src.Elem().PkgPath() == "" { 2254 switch src.Elem().Kind() { 2255 case Uint8: 2256 return cvtBytesString 2257 case Int32: 2258 return cvtRunesString 2259 } 2260 } 2261 } 2262 2263 // dst and src have same underlying type. 2264 if haveIdenticalUnderlyingType(dst, src, false) { 2265 return cvtDirect 2266 } 2267 2268 // dst and src are unnamed pointer types with same underlying base type. 2269 if dst.Kind() == Ptr && dst.Name() == "" && 2270 src.Kind() == Ptr && src.Name() == "" && 2271 haveIdenticalUnderlyingType(dst.Elem().common(), src.Elem().common(), false) { 2272 return cvtDirect 2273 } 2274 2275 if implements(dst, src) { 2276 if src.Kind() == Interface { 2277 return cvtI2I 2278 } 2279 return cvtT2I 2280 } 2281 2282 return nil 2283 } 2284 2285 // makeInt returns a Value of type t equal to bits (possibly truncated), 2286 // where t is a signed or unsigned int type. 2287 func makeInt(f flag, bits uint64, t Type) Value { 2288 typ := t.common() 2289 ptr := unsafe_New(typ) 2290 switch typ.size { 2291 case 1: 2292 *(*uint8)(ptr) = uint8(bits) 2293 case 2: 2294 *(*uint16)(ptr) = uint16(bits) 2295 case 4: 2296 *(*uint32)(ptr) = uint32(bits) 2297 case 8: 2298 *(*uint64)(ptr) = bits 2299 } 2300 return Value{typ, ptr, f | flagIndir | flag(typ.Kind())} 2301 } 2302 2303 // makeFloat returns a Value of type t equal to v (possibly truncated to float32), 2304 // where t is a float32 or float64 type. 2305 func makeFloat(f flag, v float64, t Type) Value { 2306 typ := t.common() 2307 ptr := unsafe_New(typ) 2308 switch typ.size { 2309 case 4: 2310 *(*float32)(ptr) = float32(v) 2311 case 8: 2312 *(*float64)(ptr) = v 2313 } 2314 return Value{typ, ptr, f | flagIndir | flag(typ.Kind())} 2315 } 2316 2317 // makeComplex returns a Value of type t equal to v (possibly truncated to complex64), 2318 // where t is a complex64 or complex128 type. 2319 func makeComplex(f flag, v complex128, t Type) Value { 2320 typ := t.common() 2321 ptr := unsafe_New(typ) 2322 switch typ.size { 2323 case 8: 2324 *(*complex64)(ptr) = complex64(v) 2325 case 16: 2326 *(*complex128)(ptr) = v 2327 } 2328 return Value{typ, ptr, f | flagIndir | flag(typ.Kind())} 2329 } 2330 2331 func makeString(f flag, v string, t Type) Value { 2332 ret := New(t).Elem() 2333 ret.SetString(v) 2334 ret.flag = ret.flag&^flagAddr | f 2335 return ret 2336 } 2337 2338 func makeBytes(f flag, v []byte, t Type) Value { 2339 ret := New(t).Elem() 2340 ret.SetBytes(v) 2341 ret.flag = ret.flag&^flagAddr | f 2342 return ret 2343 } 2344 2345 func makeRunes(f flag, v []rune, t Type) Value { 2346 ret := New(t).Elem() 2347 ret.setRunes(v) 2348 ret.flag = ret.flag&^flagAddr | f 2349 return ret 2350 } 2351 2352 // These conversion functions are returned by convertOp 2353 // for classes of conversions. For example, the first function, cvtInt, 2354 // takes any value v of signed int type and returns the value converted 2355 // to type t, where t is any signed or unsigned int type. 2356 2357 // convertOp: intXX -> [u]intXX 2358 func cvtInt(v Value, t Type) Value { 2359 return makeInt(v.flag&flagRO, uint64(v.Int()), t) 2360 } 2361 2362 // convertOp: uintXX -> [u]intXX 2363 func cvtUint(v Value, t Type) Value { 2364 return makeInt(v.flag&flagRO, v.Uint(), t) 2365 } 2366 2367 // convertOp: floatXX -> intXX 2368 func cvtFloatInt(v Value, t Type) Value { 2369 return makeInt(v.flag&flagRO, uint64(int64(v.Float())), t) 2370 } 2371 2372 // convertOp: floatXX -> uintXX 2373 func cvtFloatUint(v Value, t Type) Value { 2374 return makeInt(v.flag&flagRO, uint64(v.Float()), t) 2375 } 2376 2377 // convertOp: intXX -> floatXX 2378 func cvtIntFloat(v Value, t Type) Value { 2379 return makeFloat(v.flag&flagRO, float64(v.Int()), t) 2380 } 2381 2382 // convertOp: uintXX -> floatXX 2383 func cvtUintFloat(v Value, t Type) Value { 2384 return makeFloat(v.flag&flagRO, float64(v.Uint()), t) 2385 } 2386 2387 // convertOp: floatXX -> floatXX 2388 func cvtFloat(v Value, t Type) Value { 2389 return makeFloat(v.flag&flagRO, v.Float(), t) 2390 } 2391 2392 // convertOp: complexXX -> complexXX 2393 func cvtComplex(v Value, t Type) Value { 2394 return makeComplex(v.flag&flagRO, v.Complex(), t) 2395 } 2396 2397 // convertOp: intXX -> string 2398 func cvtIntString(v Value, t Type) Value { 2399 return makeString(v.flag&flagRO, string(v.Int()), t) 2400 } 2401 2402 // convertOp: uintXX -> string 2403 func cvtUintString(v Value, t Type) Value { 2404 return makeString(v.flag&flagRO, string(v.Uint()), t) 2405 } 2406 2407 // convertOp: []byte -> string 2408 func cvtBytesString(v Value, t Type) Value { 2409 return makeString(v.flag&flagRO, string(v.Bytes()), t) 2410 } 2411 2412 // convertOp: string -> []byte 2413 func cvtStringBytes(v Value, t Type) Value { 2414 return makeBytes(v.flag&flagRO, []byte(v.String()), t) 2415 } 2416 2417 // convertOp: []rune -> string 2418 func cvtRunesString(v Value, t Type) Value { 2419 return makeString(v.flag&flagRO, string(v.runes()), t) 2420 } 2421 2422 // convertOp: string -> []rune 2423 func cvtStringRunes(v Value, t Type) Value { 2424 return makeRunes(v.flag&flagRO, []rune(v.String()), t) 2425 } 2426 2427 // convertOp: direct copy 2428 func cvtDirect(v Value, typ Type) Value { 2429 f := v.flag 2430 t := typ.common() 2431 ptr := v.ptr 2432 if f&flagAddr != 0 { 2433 // indirect, mutable word - make a copy 2434 c := unsafe_New(t) 2435 typedmemmove(t, c, ptr) 2436 ptr = c 2437 f &^= flagAddr 2438 } 2439 return Value{t, ptr, v.flag&flagRO | f} // v.flag&flagRO|f == f? 2440 } 2441 2442 // convertOp: concrete -> interface 2443 func cvtT2I(v Value, typ Type) Value { 2444 target := unsafe_New(typ.common()) 2445 x := valueInterface(v, false) 2446 if typ.NumMethod() == 0 { 2447 *(*interface{})(target) = x 2448 } else { 2449 ifaceE2I(typ.(*rtype), x, target) 2450 } 2451 return Value{typ.common(), target, v.flag&flagRO | flagIndir | flag(Interface)} 2452 } 2453 2454 // convertOp: interface -> interface 2455 func cvtI2I(v Value, typ Type) Value { 2456 if v.IsNil() { 2457 ret := Zero(typ) 2458 ret.flag |= v.flag & flagRO 2459 return ret 2460 } 2461 return cvtT2I(v.Elem(), typ) 2462 } 2463 2464 // implemented in ../runtime 2465 func chancap(ch unsafe.Pointer) int 2466 func chanclose(ch unsafe.Pointer) 2467 func chanlen(ch unsafe.Pointer) int 2468 2469 // Note: some of the noescape annotations below are technically a lie, 2470 // but safe in the context of this package. Functions like chansend 2471 // and mapassign don't escape the referent, but may escape anything 2472 // the referent points to (they do shallow copies of the referent). 2473 // It is safe in this package because the referent may only point 2474 // to something a Value may point to, and that is always in the heap 2475 // (due to the escapes() call in ValueOf). 2476 2477 //go:noescape 2478 func chanrecv(ch unsafe.Pointer, nb bool, val unsafe.Pointer) (selected, received bool) 2479 2480 //go:noescape 2481 func chansend(ch unsafe.Pointer, val unsafe.Pointer, nb bool) bool 2482 2483 func makechan(typ *rtype, size uint64) (ch unsafe.Pointer) 2484 func makemap(t *rtype, cap int) (m unsafe.Pointer) 2485 2486 //go:noescape 2487 func mapaccess(t *rtype, m unsafe.Pointer, key unsafe.Pointer) (val unsafe.Pointer) 2488 2489 //go:noescape 2490 func mapassign(t *rtype, m unsafe.Pointer, key, val unsafe.Pointer) 2491 2492 //go:noescape 2493 func mapdelete(t *rtype, m unsafe.Pointer, key unsafe.Pointer) 2494 2495 // m escapes into the return value, but the caller of mapiterinit 2496 // doesn't let the return value escape. 2497 //go:noescape 2498 func mapiterinit(t *rtype, m unsafe.Pointer) unsafe.Pointer 2499 2500 //go:noescape 2501 func mapiterkey(it unsafe.Pointer) (key unsafe.Pointer) 2502 2503 //go:noescape 2504 func mapiternext(it unsafe.Pointer) 2505 2506 //go:noescape 2507 func maplen(m unsafe.Pointer) int 2508 2509 // call calls fn with a copy of the n argument bytes pointed at by arg. 2510 // After fn returns, reflectcall copies n-retoffset result bytes 2511 // back into arg+retoffset before returning. If copying result bytes back, 2512 // the caller must pass the argument frame type as argtype, so that 2513 // call can execute appropriate write barriers during the copy. 2514 func call(argtype *rtype, fn, arg unsafe.Pointer, n uint32, retoffset uint32) 2515 2516 func ifaceE2I(t *rtype, src interface{}, dst unsafe.Pointer) 2517 2518 // typedmemmove copies a value of type t to dst from src. 2519 //go:noescape 2520 func typedmemmove(t *rtype, dst, src unsafe.Pointer) 2521 2522 // typedmemmovepartial is like typedmemmove but assumes that 2523 // dst and src point off bytes into the value and only copies size bytes. 2524 //go:noescape 2525 func typedmemmovepartial(t *rtype, dst, src unsafe.Pointer, off, size uintptr) 2526 2527 // typedslicecopy copies a slice of elemType values from src to dst, 2528 // returning the number of elements copied. 2529 //go:noescape 2530 func typedslicecopy(elemType *rtype, dst, src sliceHeader) int 2531 2532 //go:noescape 2533 func memclrNoHeapPointers(ptr unsafe.Pointer, n uintptr) 2534 2535 // Dummy annotation marking that the value x escapes, 2536 // for use in cases where the reflect code is so clever that 2537 // the compiler cannot follow. 2538 func escapes(x interface{}) { 2539 if dummy.b { 2540 dummy.x = x 2541 } 2542 } 2543 2544 var dummy struct { 2545 b bool 2546 x interface{} 2547 }