github.com/lzhfromustc/gofuzz@v0.0.0-20211116160056-151b3108bbd1/runtime/string.go (about) 1 // Copyright 2014 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 runtime 6 7 import ( 8 "internal/bytealg" 9 "runtime/internal/sys" 10 "unsafe" 11 ) 12 13 // The constant is known to the compiler. 14 // There is no fundamental theory behind this number. 15 const tmpStringBufSize = 32 16 17 type tmpBuf [tmpStringBufSize]byte 18 19 // concatstrings implements a Go string concatenation x+y+z+... 20 // The operands are passed in the slice a. 21 // If buf != nil, the compiler has determined that the result does not 22 // escape the calling function, so the string data can be stored in buf 23 // if small enough. 24 func concatstrings(buf *tmpBuf, a []string) string { 25 idx := 0 26 l := 0 27 count := 0 28 for i, x := range a { 29 n := len(x) 30 if n == 0 { 31 continue 32 } 33 if l+n < l { 34 throw("string concatenation too long") 35 } 36 l += n 37 count++ 38 idx = i 39 } 40 if count == 0 { 41 return "" 42 } 43 44 // If there is just one string and either it is not on the stack 45 // or our result does not escape the calling frame (buf != nil), 46 // then we can return that string directly. 47 if count == 1 && (buf != nil || !stringDataOnStack(a[idx])) { 48 return a[idx] 49 } 50 s, b := rawstringtmp(buf, l) 51 for _, x := range a { 52 copy(b, x) 53 b = b[len(x):] 54 } 55 return s 56 } 57 58 func concatstring2(buf *tmpBuf, a [2]string) string { 59 return concatstrings(buf, a[:]) 60 } 61 62 func concatstring3(buf *tmpBuf, a [3]string) string { 63 return concatstrings(buf, a[:]) 64 } 65 66 func concatstring4(buf *tmpBuf, a [4]string) string { 67 return concatstrings(buf, a[:]) 68 } 69 70 func concatstring5(buf *tmpBuf, a [5]string) string { 71 return concatstrings(buf, a[:]) 72 } 73 74 // slicebytetostring converts a byte slice to a string. 75 // It is inserted by the compiler into generated code. 76 // ptr is a pointer to the first element of the slice; 77 // n is the length of the slice. 78 // Buf is a fixed-size buffer for the result, 79 // it is not nil if the result does not escape. 80 func slicebytetostring(buf *tmpBuf, ptr *byte, n int) (str string) { 81 if n == 0 { 82 // Turns out to be a relatively common case. 83 // Consider that you want to parse out data between parens in "foo()bar", 84 // you find the indices and convert the subslice to string. 85 return "" 86 } 87 if raceenabled { 88 racereadrangepc(unsafe.Pointer(ptr), 89 uintptr(n), 90 getcallerpc(), 91 funcPC(slicebytetostring)) 92 } 93 if msanenabled { 94 msanread(unsafe.Pointer(ptr), uintptr(n)) 95 } 96 if n == 1 { 97 p := unsafe.Pointer(&staticuint64s[*ptr]) 98 if sys.BigEndian { 99 p = add(p, 7) 100 } 101 stringStructOf(&str).str = p 102 stringStructOf(&str).len = 1 103 return 104 } 105 106 var p unsafe.Pointer 107 if buf != nil && n <= len(buf) { 108 p = unsafe.Pointer(buf) 109 } else { 110 p = mallocgc(uintptr(n), nil, false) 111 } 112 stringStructOf(&str).str = p 113 stringStructOf(&str).len = n 114 memmove(p, unsafe.Pointer(ptr), uintptr(n)) 115 return 116 } 117 118 // stringDataOnStack reports whether the string's data is 119 // stored on the current goroutine's stack. 120 func stringDataOnStack(s string) bool { 121 ptr := uintptr(stringStructOf(&s).str) 122 stk := getg().stack 123 return stk.lo <= ptr && ptr < stk.hi 124 } 125 126 func rawstringtmp(buf *tmpBuf, l int) (s string, b []byte) { 127 if buf != nil && l <= len(buf) { 128 b = buf[:l] 129 s = slicebytetostringtmp(&b[0], len(b)) 130 } else { 131 s, b = rawstring(l) 132 } 133 return 134 } 135 136 // slicebytetostringtmp returns a "string" referring to the actual []byte bytes. 137 // 138 // Callers need to ensure that the returned string will not be used after 139 // the calling goroutine modifies the original slice or synchronizes with 140 // another goroutine. 141 // 142 // The function is only called when instrumenting 143 // and otherwise intrinsified by the compiler. 144 // 145 // Some internal compiler optimizations use this function. 146 // - Used for m[T1{... Tn{..., string(k), ...} ...}] and m[string(k)] 147 // where k is []byte, T1 to Tn is a nesting of struct and array literals. 148 // - Used for "<"+string(b)+">" concatenation where b is []byte. 149 // - Used for string(b)=="foo" comparison where b is []byte. 150 func slicebytetostringtmp(ptr *byte, n int) (str string) { 151 if raceenabled && n > 0 { 152 racereadrangepc(unsafe.Pointer(ptr), 153 uintptr(n), 154 getcallerpc(), 155 funcPC(slicebytetostringtmp)) 156 } 157 if msanenabled && n > 0 { 158 msanread(unsafe.Pointer(ptr), uintptr(n)) 159 } 160 stringStructOf(&str).str = unsafe.Pointer(ptr) 161 stringStructOf(&str).len = n 162 return 163 } 164 165 func stringtoslicebyte(buf *tmpBuf, s string) []byte { 166 var b []byte 167 if buf != nil && len(s) <= len(buf) { 168 *buf = tmpBuf{} 169 b = buf[:len(s)] 170 } else { 171 b = rawbyteslice(len(s)) 172 } 173 copy(b, s) 174 return b 175 } 176 177 func stringtoslicerune(buf *[tmpStringBufSize]rune, s string) []rune { 178 // two passes. 179 // unlike slicerunetostring, no race because strings are immutable. 180 n := 0 181 for range s { 182 n++ 183 } 184 185 var a []rune 186 if buf != nil && n <= len(buf) { 187 *buf = [tmpStringBufSize]rune{} 188 a = buf[:n] 189 } else { 190 a = rawruneslice(n) 191 } 192 193 n = 0 194 for _, r := range s { 195 a[n] = r 196 n++ 197 } 198 return a 199 } 200 201 func slicerunetostring(buf *tmpBuf, a []rune) string { 202 if raceenabled && len(a) > 0 { 203 racereadrangepc(unsafe.Pointer(&a[0]), 204 uintptr(len(a))*unsafe.Sizeof(a[0]), 205 getcallerpc(), 206 funcPC(slicerunetostring)) 207 } 208 if msanenabled && len(a) > 0 { 209 msanread(unsafe.Pointer(&a[0]), uintptr(len(a))*unsafe.Sizeof(a[0])) 210 } 211 var dum [4]byte 212 size1 := 0 213 for _, r := range a { 214 size1 += encoderune(dum[:], r) 215 } 216 s, b := rawstringtmp(buf, size1+3) 217 size2 := 0 218 for _, r := range a { 219 // check for race 220 if size2 >= size1 { 221 break 222 } 223 size2 += encoderune(b[size2:], r) 224 } 225 return s[:size2] 226 } 227 228 type stringStruct struct { 229 str unsafe.Pointer 230 len int 231 } 232 233 // Variant with *byte pointer type for DWARF debugging. 234 type stringStructDWARF struct { 235 str *byte 236 len int 237 } 238 239 func stringStructOf(sp *string) *stringStruct { 240 return (*stringStruct)(unsafe.Pointer(sp)) 241 } 242 243 func intstring(buf *[4]byte, v int64) (s string) { 244 var b []byte 245 if buf != nil { 246 b = buf[:] 247 s = slicebytetostringtmp(&b[0], len(b)) 248 } else { 249 s, b = rawstring(4) 250 } 251 if int64(rune(v)) != v { 252 v = runeError 253 } 254 n := encoderune(b, rune(v)) 255 return s[:n] 256 } 257 258 // rawstring allocates storage for a new string. The returned 259 // string and byte slice both refer to the same storage. 260 // The storage is not zeroed. Callers should use 261 // b to set the string contents and then drop b. 262 func rawstring(size int) (s string, b []byte) { 263 p := mallocgc(uintptr(size), nil, false) 264 265 stringStructOf(&s).str = p 266 stringStructOf(&s).len = size 267 268 *(*slice)(unsafe.Pointer(&b)) = slice{p, size, size} 269 270 return 271 } 272 273 // rawbyteslice allocates a new byte slice. The byte slice is not zeroed. 274 func rawbyteslice(size int) (b []byte) { 275 cap := roundupsize(uintptr(size)) 276 p := mallocgc(cap, nil, false) 277 if cap != uintptr(size) { 278 memclrNoHeapPointers(add(p, uintptr(size)), cap-uintptr(size)) 279 } 280 281 *(*slice)(unsafe.Pointer(&b)) = slice{p, size, int(cap)} 282 return 283 } 284 285 // rawruneslice allocates a new rune slice. The rune slice is not zeroed. 286 func rawruneslice(size int) (b []rune) { 287 if uintptr(size) > maxAlloc/4 { 288 throw("out of memory") 289 } 290 mem := roundupsize(uintptr(size) * 4) 291 p := mallocgc(mem, nil, false) 292 if mem != uintptr(size)*4 { 293 memclrNoHeapPointers(add(p, uintptr(size)*4), mem-uintptr(size)*4) 294 } 295 296 *(*slice)(unsafe.Pointer(&b)) = slice{p, size, int(mem / 4)} 297 return 298 } 299 300 // used by cmd/cgo 301 func gobytes(p *byte, n int) (b []byte) { 302 if n == 0 { 303 return make([]byte, 0) 304 } 305 306 if n < 0 || uintptr(n) > maxAlloc { 307 panic(errorString("gobytes: length out of range")) 308 } 309 310 bp := mallocgc(uintptr(n), nil, false) 311 memmove(bp, unsafe.Pointer(p), uintptr(n)) 312 313 *(*slice)(unsafe.Pointer(&b)) = slice{bp, n, n} 314 return 315 } 316 317 // This is exported via linkname to assembly in syscall (for Plan9). 318 //go:linkname gostring 319 func gostring(p *byte) string { 320 l := findnull(p) 321 if l == 0 { 322 return "" 323 } 324 s, b := rawstring(l) 325 memmove(unsafe.Pointer(&b[0]), unsafe.Pointer(p), uintptr(l)) 326 return s 327 } 328 329 func gostringn(p *byte, l int) string { 330 if l == 0 { 331 return "" 332 } 333 s, b := rawstring(l) 334 memmove(unsafe.Pointer(&b[0]), unsafe.Pointer(p), uintptr(l)) 335 return s 336 } 337 338 func hasPrefix(s, prefix string) bool { 339 return len(s) >= len(prefix) && s[:len(prefix)] == prefix 340 } 341 342 const ( 343 maxUint = ^uint(0) 344 maxInt = int(maxUint >> 1) 345 ) 346 347 // atoi parses an int from a string s. 348 // The bool result reports whether s is a number 349 // representable by a value of type int. 350 func atoi(s string) (int, bool) { 351 if s == "" { 352 return 0, false 353 } 354 355 neg := false 356 if s[0] == '-' { 357 neg = true 358 s = s[1:] 359 } 360 361 un := uint(0) 362 for i := 0; i < len(s); i++ { 363 c := s[i] 364 if c < '0' || c > '9' { 365 return 0, false 366 } 367 if un > maxUint/10 { 368 // overflow 369 return 0, false 370 } 371 un *= 10 372 un1 := un + uint(c) - '0' 373 if un1 < un { 374 // overflow 375 return 0, false 376 } 377 un = un1 378 } 379 380 if !neg && un > uint(maxInt) { 381 return 0, false 382 } 383 if neg && un > uint(maxInt)+1 { 384 return 0, false 385 } 386 387 n := int(un) 388 if neg { 389 n = -n 390 } 391 392 return n, true 393 } 394 395 // atoi32 is like atoi but for integers 396 // that fit into an int32. 397 func atoi32(s string) (int32, bool) { 398 if n, ok := atoi(s); n == int(int32(n)) { 399 return int32(n), ok 400 } 401 return 0, false 402 } 403 404 //go:nosplit 405 func findnull(s *byte) int { 406 if s == nil { 407 return 0 408 } 409 410 // Avoid IndexByteString on Plan 9 because it uses SSE instructions 411 // on x86 machines, and those are classified as floating point instructions, 412 // which are illegal in a note handler. 413 if GOOS == "plan9" { 414 p := (*[maxAlloc/2 - 1]byte)(unsafe.Pointer(s)) 415 l := 0 416 for p[l] != 0 { 417 l++ 418 } 419 return l 420 } 421 422 // pageSize is the unit we scan at a time looking for NULL. 423 // It must be the minimum page size for any architecture Go 424 // runs on. It's okay (just a minor performance loss) if the 425 // actual system page size is larger than this value. 426 const pageSize = 4096 427 428 offset := 0 429 ptr := unsafe.Pointer(s) 430 // IndexByteString uses wide reads, so we need to be careful 431 // with page boundaries. Call IndexByteString on 432 // [ptr, endOfPage) interval. 433 safeLen := int(pageSize - uintptr(ptr)%pageSize) 434 435 for { 436 t := *(*string)(unsafe.Pointer(&stringStruct{ptr, safeLen})) 437 // Check one page at a time. 438 if i := bytealg.IndexByteString(t, 0); i != -1 { 439 return offset + i 440 } 441 // Move to next page 442 ptr = unsafe.Pointer(uintptr(ptr) + uintptr(safeLen)) 443 offset += safeLen 444 safeLen = pageSize 445 } 446 } 447 448 func findnullw(s *uint16) int { 449 if s == nil { 450 return 0 451 } 452 p := (*[maxAlloc/2/2 - 1]uint16)(unsafe.Pointer(s)) 453 l := 0 454 for p[l] != 0 { 455 l++ 456 } 457 return l 458 } 459 460 //go:nosplit 461 func gostringnocopy(str *byte) string { 462 ss := stringStruct{str: unsafe.Pointer(str), len: findnull(str)} 463 s := *(*string)(unsafe.Pointer(&ss)) 464 return s 465 } 466 467 func gostringw(strw *uint16) string { 468 var buf [8]byte 469 str := (*[maxAlloc/2/2 - 1]uint16)(unsafe.Pointer(strw)) 470 n1 := 0 471 for i := 0; str[i] != 0; i++ { 472 n1 += encoderune(buf[:], rune(str[i])) 473 } 474 s, b := rawstring(n1 + 4) 475 n2 := 0 476 for i := 0; str[i] != 0; i++ { 477 // check for race 478 if n2 >= n1 { 479 break 480 } 481 n2 += encoderune(b[n2:], rune(str[i])) 482 } 483 b[n2] = 0 // for luck 484 return s[:n2] 485 }