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.
10 "runtime/internal/sys"
14 // The constant is known to the compiler.
15 // There is no fundamental theory behind this number.
16 const tmpStringBufSize = 32
18 type tmpBuf [tmpStringBufSize]byte
20 // concatstrings implements a Go string concatenation x+y+z+...
21 // The operands are passed in the slice a.
22 // If buf != nil, the compiler has determined that the result does not
23 // escape the calling function, so the string data can be stored in buf
25 func concatstrings(buf *tmpBuf, a []string) string {
35 throw("string concatenation too long")
45 // If there is just one string and either it is not on the stack
46 // or our result does not escape the calling frame (buf != nil),
47 // then we can return that string directly.
48 if count == 1 && (buf != nil || !stringDataOnStack(a[idx])) {
51 s, b := rawstringtmp(buf, l)
59 func concatstring2(buf *tmpBuf, a0, a1 string) string {
60 return concatstrings(buf, []string{a0, a1})
63 func concatstring3(buf *tmpBuf, a0, a1, a2 string) string {
64 return concatstrings(buf, []string{a0, a1, a2})
67 func concatstring4(buf *tmpBuf, a0, a1, a2, a3 string) string {
68 return concatstrings(buf, []string{a0, a1, a2, a3})
71 func concatstring5(buf *tmpBuf, a0, a1, a2, a3, a4 string) string {
72 return concatstrings(buf, []string{a0, a1, a2, a3, a4})
75 // slicebytetostring converts a byte slice to a string.
76 // It is inserted by the compiler into generated code.
77 // ptr is a pointer to the first element of the slice;
78 // n is the length of the slice.
79 // Buf is a fixed-size buffer for the result,
80 // it is not nil if the result does not escape.
81 func slicebytetostring(buf *tmpBuf, ptr *byte, n int) (str string) {
83 // Turns out to be a relatively common case.
84 // Consider that you want to parse out data between parens in "foo()bar",
85 // you find the indices and convert the subslice to string.
89 racereadrangepc(unsafe.Pointer(ptr),
92 abi.FuncPCABIInternal(slicebytetostring))
95 msanread(unsafe.Pointer(ptr), uintptr(n))
98 p := unsafe.Pointer(&staticuint64s[*ptr])
102 stringStructOf(&str).str = p
103 stringStructOf(&str).len = 1
108 if buf != nil && n <= len(buf) {
109 p = unsafe.Pointer(buf)
111 p = mallocgc(uintptr(n), nil, false)
113 stringStructOf(&str).str = p
114 stringStructOf(&str).len = n
115 memmove(p, unsafe.Pointer(ptr), uintptr(n))
119 // stringDataOnStack reports whether the string's data is
120 // stored on the current goroutine's stack.
121 func stringDataOnStack(s string) bool {
122 ptr := uintptr(stringStructOf(&s).str)
124 return stk.lo <= ptr && ptr < stk.hi
127 func rawstringtmp(buf *tmpBuf, l int) (s string, b []byte) {
128 if buf != nil && l <= len(buf) {
130 s = slicebytetostringtmp(&b[0], len(b))
137 // slicebytetostringtmp returns a "string" referring to the actual []byte bytes.
139 // Callers need to ensure that the returned string will not be used after
140 // the calling goroutine modifies the original slice or synchronizes with
141 // another goroutine.
143 // The function is only called when instrumenting
144 // and otherwise intrinsified by the compiler.
146 // Some internal compiler optimizations use this function.
147 // - Used for m[T1{... Tn{..., string(k), ...} ...}] and m[string(k)]
148 // where k is []byte, T1 to Tn is a nesting of struct and array literals.
149 // - Used for "<"+string(b)+">" concatenation where b is []byte.
150 // - Used for string(b)=="foo" comparison where b is []byte.
151 func slicebytetostringtmp(ptr *byte, n int) (str string) {
152 if raceenabled && n > 0 {
153 racereadrangepc(unsafe.Pointer(ptr),
156 abi.FuncPCABIInternal(slicebytetostringtmp))
158 if msanenabled && n > 0 {
159 msanread(unsafe.Pointer(ptr), uintptr(n))
161 stringStructOf(&str).str = unsafe.Pointer(ptr)
162 stringStructOf(&str).len = n
166 func stringtoslicebyte(buf *tmpBuf, s string) []byte {
168 if buf != nil && len(s) <= len(buf) {
172 b = rawbyteslice(len(s))
178 func stringtoslicerune(buf *[tmpStringBufSize]rune, s string) []rune {
180 // unlike slicerunetostring, no race because strings are immutable.
187 if buf != nil && n <= len(buf) {
188 *buf = [tmpStringBufSize]rune{}
195 for _, r := range s {
202 func slicerunetostring(buf *tmpBuf, a []rune) string {
203 if raceenabled && len(a) > 0 {
204 racereadrangepc(unsafe.Pointer(&a[0]),
205 uintptr(len(a))*unsafe.Sizeof(a[0]),
207 abi.FuncPCABIInternal(slicerunetostring))
209 if msanenabled && len(a) > 0 {
210 msanread(unsafe.Pointer(&a[0]), uintptr(len(a))*unsafe.Sizeof(a[0]))
214 for _, r := range a {
215 size1 += encoderune(dum[:], r)
217 s, b := rawstringtmp(buf, size1+3)
219 for _, r := range a {
224 size2 += encoderune(b[size2:], r)
229 type stringStruct struct {
234 // Variant with *byte pointer type for DWARF debugging.
235 type stringStructDWARF struct {
240 func stringStructOf(sp *string) *stringStruct {
241 return (*stringStruct)(unsafe.Pointer(sp))
244 func intstring(buf *[4]byte, v int64) (s string) {
248 s = slicebytetostringtmp(&b[0], len(b))
252 if int64(rune(v)) != v {
255 n := encoderune(b, rune(v))
259 // rawstring allocates storage for a new string. The returned
260 // string and byte slice both refer to the same storage.
261 // The storage is not zeroed. Callers should use
262 // b to set the string contents and then drop b.
263 func rawstring(size int) (s string, b []byte) {
264 p := mallocgc(uintptr(size), nil, false)
266 stringStructOf(&s).str = p
267 stringStructOf(&s).len = size
269 *(*slice)(unsafe.Pointer(&b)) = slice{p, size, size}
274 // rawbyteslice allocates a new byte slice. The byte slice is not zeroed.
275 func rawbyteslice(size int) (b []byte) {
276 cap := roundupsize(uintptr(size))
277 p := mallocgc(cap, nil, false)
278 if cap != uintptr(size) {
279 memclrNoHeapPointers(add(p, uintptr(size)), cap-uintptr(size))
282 *(*slice)(unsafe.Pointer(&b)) = slice{p, size, int(cap)}
286 // rawruneslice allocates a new rune slice. The rune slice is not zeroed.
287 func rawruneslice(size int) (b []rune) {
288 if uintptr(size) > maxAlloc/4 {
289 throw("out of memory")
291 mem := roundupsize(uintptr(size) * 4)
292 p := mallocgc(mem, nil, false)
293 if mem != uintptr(size)*4 {
294 memclrNoHeapPointers(add(p, uintptr(size)*4), mem-uintptr(size)*4)
297 *(*slice)(unsafe.Pointer(&b)) = slice{p, size, int(mem / 4)}
302 func gobytes(p *byte, n int) (b []byte) {
304 return make([]byte, 0)
307 if n < 0 || uintptr(n) > maxAlloc {
308 panic(errorString("gobytes: length out of range"))
311 bp := mallocgc(uintptr(n), nil, false)
312 memmove(bp, unsafe.Pointer(p), uintptr(n))
314 *(*slice)(unsafe.Pointer(&b)) = slice{bp, n, n}
318 // This is exported via linkname to assembly in syscall (for Plan9).
319 //go:linkname gostring
320 func gostring(p *byte) string {
326 memmove(unsafe.Pointer(&b[0]), unsafe.Pointer(p), uintptr(l))
330 func gostringn(p *byte, l int) string {
335 memmove(unsafe.Pointer(&b[0]), unsafe.Pointer(p), uintptr(l))
339 func hasPrefix(s, prefix string) bool {
340 return len(s) >= len(prefix) && s[:len(prefix)] == prefix
345 maxInt = int(maxUint >> 1)
348 // atoi parses an int from a string s.
349 // The bool result reports whether s is a number
350 // representable by a value of type int.
351 func atoi(s string) (int, bool) {
363 for i := 0; i < len(s); i++ {
365 if c < '0' || c > '9' {
373 un1 := un + uint(c) - '0'
381 if !neg && un > uint(maxInt) {
384 if neg && un > uint(maxInt)+1 {
396 // atoi32 is like atoi but for integers
397 // that fit into an int32.
398 func atoi32(s string) (int32, bool) {
399 if n, ok := atoi(s); n == int(int32(n)) {
406 func findnull(s *byte) int {
411 // Avoid IndexByteString on Plan 9 because it uses SSE instructions
412 // on x86 machines, and those are classified as floating point instructions,
413 // which are illegal in a note handler.
415 p := (*[maxAlloc/2 - 1]byte)(unsafe.Pointer(s))
423 // pageSize is the unit we scan at a time looking for NULL.
424 // It must be the minimum page size for any architecture Go
425 // runs on. It's okay (just a minor performance loss) if the
426 // actual system page size is larger than this value.
427 const pageSize = 4096
430 ptr := unsafe.Pointer(s)
431 // IndexByteString uses wide reads, so we need to be careful
432 // with page boundaries. Call IndexByteString on
433 // [ptr, endOfPage) interval.
434 safeLen := int(pageSize - uintptr(ptr)%pageSize)
437 t := *(*string)(unsafe.Pointer(&stringStruct{ptr, safeLen}))
438 // Check one page at a time.
439 if i := bytealg.IndexByteString(t, 0); i != -1 {
443 ptr = unsafe.Pointer(uintptr(ptr) + uintptr(safeLen))
449 func findnullw(s *uint16) int {
453 p := (*[maxAlloc/2/2 - 1]uint16)(unsafe.Pointer(s))
462 func gostringnocopy(str *byte) string {
463 ss := stringStruct{str: unsafe.Pointer(str), len: findnull(str)}
464 s := *(*string)(unsafe.Pointer(&ss))
468 func gostringw(strw *uint16) string {
470 str := (*[maxAlloc/2/2 - 1]uint16)(unsafe.Pointer(strw))
472 for i := 0; str[i] != 0; i++ {
473 n1 += encoderune(buf[:], rune(str[i]))
475 s, b := rawstring(n1 + 4)
477 for i := 0; str[i] != 0; i++ {
482 n2 += encoderune(b[n2:], rune(str[i]))
484 b[n2] = 0 // for luck