github.com/karrick/go@v0.0.0-20170817181416-d5b0ec858b37/src/runtime/alg.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 "runtime/internal/sys" 9 "unsafe" 10 ) 11 12 const ( 13 c0 = uintptr((8-sys.PtrSize)/4*2860486313 + (sys.PtrSize-4)/4*33054211828000289) 14 c1 = uintptr((8-sys.PtrSize)/4*3267000013 + (sys.PtrSize-4)/4*23344194077549503) 15 ) 16 17 // type algorithms - known to compiler 18 const ( 19 alg_NOEQ = iota 20 alg_MEM0 21 alg_MEM8 22 alg_MEM16 23 alg_MEM32 24 alg_MEM64 25 alg_MEM128 26 alg_STRING 27 alg_INTER 28 alg_NILINTER 29 alg_FLOAT32 30 alg_FLOAT64 31 alg_CPLX64 32 alg_CPLX128 33 alg_max 34 ) 35 36 // typeAlg is also copied/used in reflect/type.go. 37 // keep them in sync. 38 type typeAlg struct { 39 // function for hashing objects of this type 40 // (ptr to object, seed) -> hash 41 hash func(unsafe.Pointer, uintptr) uintptr 42 // function for comparing objects of this type 43 // (ptr to object A, ptr to object B) -> ==? 44 equal func(unsafe.Pointer, unsafe.Pointer) bool 45 } 46 47 func memhash0(p unsafe.Pointer, h uintptr) uintptr { 48 return h 49 } 50 func memhash8(p unsafe.Pointer, h uintptr) uintptr { 51 return memhash(p, h, 1) 52 } 53 func memhash16(p unsafe.Pointer, h uintptr) uintptr { 54 return memhash(p, h, 2) 55 } 56 func memhash32(p unsafe.Pointer, h uintptr) uintptr { 57 return memhash(p, h, 4) 58 } 59 func memhash64(p unsafe.Pointer, h uintptr) uintptr { 60 return memhash(p, h, 8) 61 } 62 func memhash128(p unsafe.Pointer, h uintptr) uintptr { 63 return memhash(p, h, 16) 64 } 65 66 //go:nosplit 67 func memhash_varlen(p unsafe.Pointer, h uintptr) uintptr { 68 ptr := getclosureptr() 69 size := *(*uintptr)(unsafe.Pointer(ptr + unsafe.Sizeof(h))) 70 return memhash(p, h, size) 71 } 72 73 var algarray = [alg_max]typeAlg{ 74 alg_NOEQ: {nil, nil}, 75 alg_MEM0: {memhash0, memequal0}, 76 alg_MEM8: {memhash8, memequal8}, 77 alg_MEM16: {memhash16, memequal16}, 78 alg_MEM32: {memhash32, memequal32}, 79 alg_MEM64: {memhash64, memequal64}, 80 alg_MEM128: {memhash128, memequal128}, 81 alg_STRING: {strhash, strequal}, 82 alg_INTER: {interhash, interequal}, 83 alg_NILINTER: {nilinterhash, nilinterequal}, 84 alg_FLOAT32: {f32hash, f32equal}, 85 alg_FLOAT64: {f64hash, f64equal}, 86 alg_CPLX64: {c64hash, c64equal}, 87 alg_CPLX128: {c128hash, c128equal}, 88 } 89 90 var useAeshash bool 91 92 // in asm_*.s 93 func aeshash(p unsafe.Pointer, h, s uintptr) uintptr 94 func aeshash32(p unsafe.Pointer, h uintptr) uintptr 95 func aeshash64(p unsafe.Pointer, h uintptr) uintptr 96 func aeshashstr(p unsafe.Pointer, h uintptr) uintptr 97 98 func strhash(a unsafe.Pointer, h uintptr) uintptr { 99 x := (*stringStruct)(a) 100 return memhash(x.str, h, uintptr(x.len)) 101 } 102 103 // NOTE: Because NaN != NaN, a map can contain any 104 // number of (mostly useless) entries keyed with NaNs. 105 // To avoid long hash chains, we assign a random number 106 // as the hash value for a NaN. 107 108 func f32hash(p unsafe.Pointer, h uintptr) uintptr { 109 f := *(*float32)(p) 110 switch { 111 case f == 0: 112 return c1 * (c0 ^ h) // +0, -0 113 case f != f: 114 return c1 * (c0 ^ h ^ uintptr(fastrand())) // any kind of NaN 115 default: 116 return memhash(p, h, 4) 117 } 118 } 119 120 func f64hash(p unsafe.Pointer, h uintptr) uintptr { 121 f := *(*float64)(p) 122 switch { 123 case f == 0: 124 return c1 * (c0 ^ h) // +0, -0 125 case f != f: 126 return c1 * (c0 ^ h ^ uintptr(fastrand())) // any kind of NaN 127 default: 128 return memhash(p, h, 8) 129 } 130 } 131 132 func c64hash(p unsafe.Pointer, h uintptr) uintptr { 133 x := (*[2]float32)(p) 134 return f32hash(unsafe.Pointer(&x[1]), f32hash(unsafe.Pointer(&x[0]), h)) 135 } 136 137 func c128hash(p unsafe.Pointer, h uintptr) uintptr { 138 x := (*[2]float64)(p) 139 return f64hash(unsafe.Pointer(&x[1]), f64hash(unsafe.Pointer(&x[0]), h)) 140 } 141 142 func interhash(p unsafe.Pointer, h uintptr) uintptr { 143 a := (*iface)(p) 144 tab := a.tab 145 if tab == nil { 146 return h 147 } 148 t := tab._type 149 fn := t.alg.hash 150 if fn == nil { 151 panic(errorString("hash of unhashable type " + t.string())) 152 } 153 if isDirectIface(t) { 154 return c1 * fn(unsafe.Pointer(&a.data), h^c0) 155 } else { 156 return c1 * fn(a.data, h^c0) 157 } 158 } 159 160 func nilinterhash(p unsafe.Pointer, h uintptr) uintptr { 161 a := (*eface)(p) 162 t := a._type 163 if t == nil { 164 return h 165 } 166 fn := t.alg.hash 167 if fn == nil { 168 panic(errorString("hash of unhashable type " + t.string())) 169 } 170 if isDirectIface(t) { 171 return c1 * fn(unsafe.Pointer(&a.data), h^c0) 172 } else { 173 return c1 * fn(a.data, h^c0) 174 } 175 } 176 177 func memequal0(p, q unsafe.Pointer) bool { 178 return true 179 } 180 func memequal8(p, q unsafe.Pointer) bool { 181 return *(*int8)(p) == *(*int8)(q) 182 } 183 func memequal16(p, q unsafe.Pointer) bool { 184 return *(*int16)(p) == *(*int16)(q) 185 } 186 func memequal32(p, q unsafe.Pointer) bool { 187 return *(*int32)(p) == *(*int32)(q) 188 } 189 func memequal64(p, q unsafe.Pointer) bool { 190 return *(*int64)(p) == *(*int64)(q) 191 } 192 func memequal128(p, q unsafe.Pointer) bool { 193 return *(*[2]int64)(p) == *(*[2]int64)(q) 194 } 195 func f32equal(p, q unsafe.Pointer) bool { 196 return *(*float32)(p) == *(*float32)(q) 197 } 198 func f64equal(p, q unsafe.Pointer) bool { 199 return *(*float64)(p) == *(*float64)(q) 200 } 201 func c64equal(p, q unsafe.Pointer) bool { 202 return *(*complex64)(p) == *(*complex64)(q) 203 } 204 func c128equal(p, q unsafe.Pointer) bool { 205 return *(*complex128)(p) == *(*complex128)(q) 206 } 207 func strequal(p, q unsafe.Pointer) bool { 208 return *(*string)(p) == *(*string)(q) 209 } 210 func interequal(p, q unsafe.Pointer) bool { 211 x := *(*iface)(p) 212 y := *(*iface)(q) 213 return x.tab == y.tab && ifaceeq(x.tab, x.data, y.data) 214 } 215 func nilinterequal(p, q unsafe.Pointer) bool { 216 x := *(*eface)(p) 217 y := *(*eface)(q) 218 return x._type == y._type && efaceeq(x._type, x.data, y.data) 219 } 220 func efaceeq(t *_type, x, y unsafe.Pointer) bool { 221 if t == nil { 222 return true 223 } 224 eq := t.alg.equal 225 if eq == nil { 226 panic(errorString("comparing uncomparable type " + t.string())) 227 } 228 if isDirectIface(t) { 229 return eq(noescape(unsafe.Pointer(&x)), noescape(unsafe.Pointer(&y))) 230 } 231 return eq(x, y) 232 } 233 func ifaceeq(tab *itab, x, y unsafe.Pointer) bool { 234 if tab == nil { 235 return true 236 } 237 t := tab._type 238 eq := t.alg.equal 239 if eq == nil { 240 panic(errorString("comparing uncomparable type " + t.string())) 241 } 242 if isDirectIface(t) { 243 return eq(noescape(unsafe.Pointer(&x)), noescape(unsafe.Pointer(&y))) 244 } 245 return eq(x, y) 246 } 247 248 // Testing adapters for hash quality tests (see hash_test.go) 249 func stringHash(s string, seed uintptr) uintptr { 250 return algarray[alg_STRING].hash(noescape(unsafe.Pointer(&s)), seed) 251 } 252 253 func bytesHash(b []byte, seed uintptr) uintptr { 254 s := (*slice)(unsafe.Pointer(&b)) 255 return memhash(s.array, seed, uintptr(s.len)) 256 } 257 258 func int32Hash(i uint32, seed uintptr) uintptr { 259 return algarray[alg_MEM32].hash(noescape(unsafe.Pointer(&i)), seed) 260 } 261 262 func int64Hash(i uint64, seed uintptr) uintptr { 263 return algarray[alg_MEM64].hash(noescape(unsafe.Pointer(&i)), seed) 264 } 265 266 func efaceHash(i interface{}, seed uintptr) uintptr { 267 return algarray[alg_NILINTER].hash(noescape(unsafe.Pointer(&i)), seed) 268 } 269 270 func ifaceHash(i interface { 271 F() 272 }, seed uintptr) uintptr { 273 return algarray[alg_INTER].hash(noescape(unsafe.Pointer(&i)), seed) 274 } 275 276 const hashRandomBytes = sys.PtrSize / 4 * 64 277 278 // used in asm_{386,amd64}.s to seed the hash function 279 var aeskeysched [hashRandomBytes]byte 280 281 // used in hash{32,64}.go to seed the hash function 282 var hashkey [4]uintptr 283 284 func alginit() { 285 // Install aes hash algorithm if we have the instructions we need 286 if (GOARCH == "386" || GOARCH == "amd64") && 287 GOOS != "nacl" && 288 support_aes && // AESENC 289 support_ssse3 && // PSHUFB 290 support_sse41 { // PINSR{D,Q} 291 useAeshash = true 292 algarray[alg_MEM32].hash = aeshash32 293 algarray[alg_MEM64].hash = aeshash64 294 algarray[alg_STRING].hash = aeshashstr 295 // Initialize with random data so hash collisions will be hard to engineer. 296 getRandomData(aeskeysched[:]) 297 return 298 } 299 getRandomData((*[len(hashkey) * sys.PtrSize]byte)(unsafe.Pointer(&hashkey))[:]) 300 hashkey[0] |= 1 // make sure these numbers are odd 301 hashkey[1] |= 1 302 hashkey[2] |= 1 303 hashkey[3] |= 1 304 }