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 "unsafe" 10 ) 11 12 // The constant is known to the compiler. 13 // There is no fundamental theory behind this number. 14 const tmpStringBufSize = 32 15 16 type tmpBuf [tmpStringBufSize]byte 17 18 // concatstrings implements a Go string concatenation x+y+z+... 19 // The operands are passed in the slice a. 20 // If buf != nil, the compiler has determined that the result does not 21 // escape the calling function, so the string data can be stored in buf 22 // if small enough. 23 func concatstrings(buf *tmpBuf, a []string) string { 24 idx := 0 25 l := 0 26 count := 0 27 for i, x := range a { 28 n := len(x) 29 if n == 0 { 30 continue 31 } 32 if l+n < l { 33 throw("string concatenation too long") 34 } 35 l += n 36 count++ 37 idx = i 38 } 39 if count == 0 { 40 return "" 41 } 42 43 // If there is just one string and either it is not on the stack 44 // or our result does not escape the calling frame (buf != nil), 45 // then we can return that string directly. 46 if count == 1 && (buf != nil || !stringDataOnStack(a[idx])) { 47 return a[idx] 48 } 49 s, b := rawstringtmp(buf, l) 50 for _, x := range a { 51 copy(b, x) 52 b = b[len(x):] 53 } 54 return s 55 } 56 57 func concatstring2(buf *tmpBuf, a [2]string) string { 58 return concatstrings(buf, a[:]) 59 } 60 61 func concatstring3(buf *tmpBuf, a [3]string) string { 62 return concatstrings(buf, a[:]) 63 } 64 65 func concatstring4(buf *tmpBuf, a [4]string) string { 66 return concatstrings(buf, a[:]) 67 } 68 69 func concatstring5(buf *tmpBuf, a [5]string) string { 70 return concatstrings(buf, a[:]) 71 } 72 73 // Buf is a fixed-size buffer for the result, 74 // it is not nil if the result does not escape. 75 func slicebytetostring(buf *tmpBuf, b []byte) (str string) { 76 l := len(b) 77 if l == 0 { 78 // Turns out to be a relatively common case. 79 // Consider that you want to parse out data between parens in "foo()bar", 80 // you find the indices and convert the subslice to string. 81 return "" 82 } 83 if raceenabled { 84 racereadrangepc(unsafe.Pointer(&b[0]), 85 uintptr(l), 86 getcallerpc(), 87 funcPC(slicebytetostring)) 88 } 89 if msanenabled { 90 msanread(unsafe.Pointer(&b[0]), uintptr(l)) 91 } 92 if l == 1 { 93 stringStructOf(&str).str = unsafe.Pointer(&staticbytes[b[0]]) 94 stringStructOf(&str).len = 1 95 return 96 } 97 98 var p unsafe.Pointer 99 if buf != nil && len(b) <= len(buf) { 100 p = unsafe.Pointer(buf) 101 } else { 102 p = mallocgc(uintptr(len(b)), nil, false) 103 } 104 stringStructOf(&str).str = p 105 stringStructOf(&str).len = len(b) 106 memmove(p, (*(*slice)(unsafe.Pointer(&b))).array, uintptr(len(b))) 107 return 108 } 109 110 // stringDataOnStack reports whether the string's data is 111 // stored on the current goroutine's stack. 112 func stringDataOnStack(s string) bool { 113 ptr := uintptr(stringStructOf(&s).str) 114 stk := getg().stack 115 return stk.lo <= ptr && ptr < stk.hi 116 } 117 118 func rawstringtmp(buf *tmpBuf, l int) (s string, b []byte) { 119 if buf != nil && l <= len(buf) { 120 b = buf[:l] 121 s = slicebytetostringtmp(b) 122 } else { 123 s, b = rawstring(l) 124 } 125 return 126 } 127 128 // slicebytetostringtmp returns a "string" referring to the actual []byte bytes. 129 // 130 // Callers need to ensure that the returned string will not be used after 131 // the calling goroutine modifies the original slice or synchronizes with 132 // another goroutine. 133 // 134 // The function is only called when instrumenting 135 // and otherwise intrinsified by the compiler. 136 // 137 // Some internal compiler optimizations use this function. 138 // - Used for m[T1{... Tn{..., string(k), ...} ...}] and m[string(k)] 139 // where k is []byte, T1 to Tn is a nesting of struct and array literals. 140 // - Used for "<"+string(b)+">" concatenation where b is []byte. 141 // - Used for string(b)=="foo" comparison where b is []byte. 142 func slicebytetostringtmp(b []byte) string { 143 if raceenabled && len(b) > 0 { 144 racereadrangepc(unsafe.Pointer(&b[0]), 145 uintptr(len(b)), 146 getcallerpc(), 147 funcPC(slicebytetostringtmp)) 148 } 149 if msanenabled && len(b) > 0 { 150 msanread(unsafe.Pointer(&b[0]), uintptr(len(b))) 151 } 152 return *(*string)(unsafe.Pointer(&b)) 153 } 154 155 func stringtoslicebyte(buf *tmpBuf, s string) []byte { 156 var b []byte 157 if buf != nil && len(s) <= len(buf) { 158 *buf = tmpBuf{} 159 b = buf[:len(s)] 160 } else { 161 b = rawbyteslice(len(s)) 162 } 163 copy(b, s) 164 return b 165 } 166 167 func stringtoslicerune(buf *[tmpStringBufSize]rune, s string) []rune { 168 // two passes. 169 // unlike slicerunetostring, no race because strings are immutable. 170 n := 0 171 for range s { 172 n++ 173 } 174 175 var a []rune 176 if buf != nil && n <= len(buf) { 177 *buf = [tmpStringBufSize]rune{} 178 a = buf[:n] 179 } else { 180 a = rawruneslice(n) 181 } 182 183 n = 0 184 for _, r := range s { 185 a[n] = r 186 n++ 187 } 188 return a 189 } 190 191 func slicerunetostring(buf *tmpBuf, a []rune) string { 192 if raceenabled && len(a) > 0 { 193 racereadrangepc(unsafe.Pointer(&a[0]), 194 uintptr(len(a))*unsafe.Sizeof(a[0]), 195 getcallerpc(), 196 funcPC(slicerunetostring)) 197 } 198 if msanenabled && len(a) > 0 { 199 msanread(unsafe.Pointer(&a[0]), uintptr(len(a))*unsafe.Sizeof(a[0])) 200 } 201 var dum [4]byte 202 size1 := 0 203 for _, r := range a { 204 size1 += encoderune(dum[:], r) 205 } 206 s, b := rawstringtmp(buf, size1+3) 207 size2 := 0 208 for _, r := range a { 209 // check for race 210 if size2 >= size1 { 211 break 212 } 213 size2 += encoderune(b[size2:], r) 214 } 215 return s[:size2] 216 } 217 218 type stringStruct struct { 219 str unsafe.Pointer 220 len int 221 } 222 223 // Variant with *byte pointer type for DWARF debugging. 224 type stringStructDWARF struct { 225 str *byte 226 len int 227 } 228 229 func stringStructOf(sp *string) *stringStruct { 230 return (*stringStruct)(unsafe.Pointer(sp)) 231 } 232 233 func intstring(buf *[4]byte, v int64) (s string) { 234 if v >= 0 && v < runeSelf { 235 stringStructOf(&s).str = unsafe.Pointer(&staticbytes[v]) 236 stringStructOf(&s).len = 1 237 return 238 } 239 240 var b []byte 241 if buf != nil { 242 b = buf[:] 243 s = slicebytetostringtmp(b) 244 } else { 245 s, b = rawstring(4) 246 } 247 if int64(rune(v)) != v { 248 v = runeError 249 } 250 n := encoderune(b, rune(v)) 251 return s[:n] 252 } 253 254 // rawstring allocates storage for a new string. The returned 255 // string and byte slice both refer to the same storage. 256 // The storage is not zeroed. Callers should use 257 // b to set the string contents and then drop b. 258 func rawstring(size int) (s string, b []byte) { 259 p := mallocgc(uintptr(size), nil, false) 260 261 stringStructOf(&s).str = p 262 stringStructOf(&s).len = size 263 264 *(*slice)(unsafe.Pointer(&b)) = slice{p, size, size} 265 266 return 267 } 268 269 // rawbyteslice allocates a new byte slice. The byte slice is not zeroed. 270 func rawbyteslice(size int) (b []byte) { 271 cap := roundupsize(uintptr(size)) 272 p := mallocgc(cap, nil, false) 273 if cap != uintptr(size) { 274 memclrNoHeapPointers(add(p, uintptr(size)), cap-uintptr(size)) 275 } 276 277 *(*slice)(unsafe.Pointer(&b)) = slice{p, size, int(cap)} 278 return 279 } 280 281 // rawruneslice allocates a new rune slice. The rune slice is not zeroed. 282 func rawruneslice(size int) (b []rune) { 283 if uintptr(size) > maxAlloc/4 { 284 throw("out of memory") 285 } 286 mem := roundupsize(uintptr(size) * 4) 287 p := mallocgc(mem, nil, false) 288 if mem != uintptr(size)*4 { 289 memclrNoHeapPointers(add(p, uintptr(size)*4), mem-uintptr(size)*4) 290 } 291 292 *(*slice)(unsafe.Pointer(&b)) = slice{p, size, int(mem / 4)} 293 return 294 } 295 296 // used by cmd/cgo 297 func gobytes(p *byte, n int) (b []byte) { 298 if n == 0 { 299 return make([]byte, 0) 300 } 301 302 if n < 0 || uintptr(n) > maxAlloc { 303 panic(errorString("gobytes: length out of range")) 304 } 305 306 bp := mallocgc(uintptr(n), nil, false) 307 memmove(bp, unsafe.Pointer(p), uintptr(n)) 308 309 *(*slice)(unsafe.Pointer(&b)) = slice{bp, n, n} 310 return 311 } 312 313 // This is exported via linkname to assembly in syscall (for Plan9). 314 //go:linkname gostring 315 func gostring(p *byte) string { 316 l := findnull(p) 317 if l == 0 { 318 return "" 319 } 320 s, b := rawstring(l) 321 memmove(unsafe.Pointer(&b[0]), unsafe.Pointer(p), uintptr(l)) 322 return s 323 } 324 325 func gostringn(p *byte, l int) string { 326 if l == 0 { 327 return "" 328 } 329 s, b := rawstring(l) 330 memmove(unsafe.Pointer(&b[0]), unsafe.Pointer(p), uintptr(l)) 331 return s 332 } 333 334 func index(s, t string) int { 335 if len(t) == 0 { 336 return 0 337 } 338 for i := 0; i < len(s); i++ { 339 if s[i] == t[0] && hasPrefix(s[i:], t) { 340 return i 341 } 342 } 343 return -1 344 } 345 346 func contains(s, t string) bool { 347 return index(s, t) >= 0 348 } 349 350 func hasPrefix(s, prefix string) bool { 351 return len(s) >= len(prefix) && s[:len(prefix)] == prefix 352 } 353 354 const ( 355 maxUint = ^uint(0) 356 maxInt = int(maxUint >> 1) 357 ) 358 359 // atoi parses an int from a string s. 360 // The bool result reports whether s is a number 361 // representable by a value of type int. 362 func atoi(s string) (int, bool) { 363 if s == "" { 364 return 0, false 365 } 366 367 neg := false 368 if s[0] == '-' { 369 neg = true 370 s = s[1:] 371 } 372 373 un := uint(0) 374 for i := 0; i < len(s); i++ { 375 c := s[i] 376 if c < '0' || c > '9' { 377 return 0, false 378 } 379 if un > maxUint/10 { 380 // overflow 381 return 0, false 382 } 383 un *= 10 384 un1 := un + uint(c) - '0' 385 if un1 < un { 386 // overflow 387 return 0, false 388 } 389 un = un1 390 } 391 392 if !neg && un > uint(maxInt) { 393 return 0, false 394 } 395 if neg && un > uint(maxInt)+1 { 396 return 0, false 397 } 398 399 n := int(un) 400 if neg { 401 n = -n 402 } 403 404 return n, true 405 } 406 407 // atoi32 is like atoi but for integers 408 // that fit into an int32. 409 func atoi32(s string) (int32, bool) { 410 if n, ok := atoi(s); n == int(int32(n)) { 411 return int32(n), ok 412 } 413 return 0, false 414 } 415 416 //go:nosplit 417 func findnull(s *byte) int { 418 if s == nil { 419 return 0 420 } 421 422 // Avoid IndexByteString on Plan 9 because it uses SSE instructions 423 // on x86 machines, and those are classified as floating point instructions, 424 // which are illegal in a note handler. 425 if GOOS == "plan9" { 426 p := (*[maxAlloc/2 - 1]byte)(unsafe.Pointer(s)) 427 l := 0 428 for p[l] != 0 { 429 l++ 430 } 431 return l 432 } 433 434 // pageSize is the unit we scan at a time looking for NULL. 435 // It must be the minimum page size for any architecture Go 436 // runs on. It's okay (just a minor performance loss) if the 437 // actual system page size is larger than this value. 438 const pageSize = 4096 439 440 offset := 0 441 ptr := unsafe.Pointer(s) 442 // IndexByteString uses wide reads, so we need to be careful 443 // with page boundaries. Call IndexByteString on 444 // [ptr, endOfPage) interval. 445 safeLen := int(pageSize - uintptr(ptr)%pageSize) 446 447 for { 448 t := *(*string)(unsafe.Pointer(&stringStruct{ptr, safeLen})) 449 // Check one page at a time. 450 if i := bytealg.IndexByteString(t, 0); i != -1 { 451 return offset + i 452 } 453 // Move to next page 454 ptr = unsafe.Pointer(uintptr(ptr) + uintptr(safeLen)) 455 offset += safeLen 456 safeLen = pageSize 457 } 458 } 459 460 func findnullw(s *uint16) int { 461 if s == nil { 462 return 0 463 } 464 p := (*[maxAlloc/2/2 - 1]uint16)(unsafe.Pointer(s)) 465 l := 0 466 for p[l] != 0 { 467 l++ 468 } 469 return l 470 } 471 472 //go:nosplit 473 func gostringnocopy(str *byte) string { 474 ss := stringStruct{str: unsafe.Pointer(str), len: findnull(str)} 475 s := *(*string)(unsafe.Pointer(&ss)) 476 return s 477 } 478 479 func gostringw(strw *uint16) string { 480 var buf [8]byte 481 str := (*[maxAlloc/2/2 - 1]uint16)(unsafe.Pointer(strw)) 482 n1 := 0 483 for i := 0; str[i] != 0; i++ { 484 n1 += encoderune(buf[:], rune(str[i])) 485 } 486 s, b := rawstring(n1 + 4) 487 n2 := 0 488 for i := 0; str[i] != 0; i++ { 489 // check for race 490 if n2 >= n1 { 491 break 492 } 493 n2 += encoderune(b[n2:], rune(str[i])) 494 } 495 b[n2] = 0 // for luck 496 return s[:n2] 497 } 498
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