// Copyright 2014 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package runtime import ( "internal/abi" "internal/bytealg" "internal/goarch" "unsafe" ) // The constant is known to the compiler. // There is no fundamental theory behind this number. const tmpStringBufSize = 32 type tmpBuf [tmpStringBufSize]byte // concatstrings implements a Go string concatenation x+y+z+... // The operands are passed in the slice a. // If buf != nil, the compiler has determined that the result does not // escape the calling function, so the string data can be stored in buf // if small enough. func concatstrings(buf *tmpBuf, a []string) string { idx := 0 l := 0 count := 0 for i, x := range a { n := len(x) if n == 0 { continue } if l+n < l { throw("string concatenation too long") } l += n count++ idx = i } if count == 0 { return "" } // If there is just one string and either it is not on the stack // or our result does not escape the calling frame (buf != nil), // then we can return that string directly. if count == 1 && (buf != nil || !stringDataOnStack(a[idx])) { return a[idx] } s, b := rawstringtmp(buf, l) for _, x := range a { copy(b, x) b = b[len(x):] } return s } func concatstring2(buf *tmpBuf, a0, a1 string) string { return concatstrings(buf, []string{a0, a1}) } func concatstring3(buf *tmpBuf, a0, a1, a2 string) string { return concatstrings(buf, []string{a0, a1, a2}) } func concatstring4(buf *tmpBuf, a0, a1, a2, a3 string) string { return concatstrings(buf, []string{a0, a1, a2, a3}) } func concatstring5(buf *tmpBuf, a0, a1, a2, a3, a4 string) string { return concatstrings(buf, []string{a0, a1, a2, a3, a4}) } // slicebytetostring converts a byte slice to a string. // It is inserted by the compiler into generated code. // ptr is a pointer to the first element of the slice; // n is the length of the slice. // Buf is a fixed-size buffer for the result, // it is not nil if the result does not escape. func slicebytetostring(buf *tmpBuf, ptr *byte, n int) string { if n == 0 { // Turns out to be a relatively common case. // Consider that you want to parse out data between parens in "foo()bar", // you find the indices and convert the subslice to string. return "" } if raceenabled { racereadrangepc(unsafe.Pointer(ptr), uintptr(n), getcallerpc(), abi.FuncPCABIInternal(slicebytetostring)) } if msanenabled { msanread(unsafe.Pointer(ptr), uintptr(n)) } if asanenabled { asanread(unsafe.Pointer(ptr), uintptr(n)) } if n == 1 { p := unsafe.Pointer(&staticuint64s[*ptr]) if goarch.BigEndian { p = add(p, 7) } return unsafe.String((*byte)(p), 1) } var p unsafe.Pointer if buf != nil && n <= len(buf) { p = unsafe.Pointer(buf) } else { p = mallocgc(uintptr(n), nil, false) } memmove(p, unsafe.Pointer(ptr), uintptr(n)) return unsafe.String((*byte)(p), n) } // stringDataOnStack reports whether the string's data is // stored on the current goroutine's stack. func stringDataOnStack(s string) bool { ptr := uintptr(unsafe.Pointer(unsafe.StringData(s))) stk := getg().stack return stk.lo <= ptr && ptr < stk.hi } func rawstringtmp(buf *tmpBuf, l int) (s string, b []byte) { if buf != nil && l <= len(buf) { b = buf[:l] s = slicebytetostringtmp(&b[0], len(b)) } else { s, b = rawstring(l) } return } // slicebytetostringtmp returns a "string" referring to the actual []byte bytes. // // Callers need to ensure that the returned string will not be used after // the calling goroutine modifies the original slice or synchronizes with // another goroutine. // // The function is only called when instrumenting // and otherwise intrinsified by the compiler. // // Some internal compiler optimizations use this function. // - Used for m[T1{... Tn{..., string(k), ...} ...}] and m[string(k)] // where k is []byte, T1 to Tn is a nesting of struct and array literals. // - Used for "<"+string(b)+">" concatenation where b is []byte. // - Used for string(b)=="foo" comparison where b is []byte. func slicebytetostringtmp(ptr *byte, n int) string { if raceenabled && n > 0 { racereadrangepc(unsafe.Pointer(ptr), uintptr(n), getcallerpc(), abi.FuncPCABIInternal(slicebytetostringtmp)) } if msanenabled && n > 0 { msanread(unsafe.Pointer(ptr), uintptr(n)) } if asanenabled && n > 0 { asanread(unsafe.Pointer(ptr), uintptr(n)) } return unsafe.String(ptr, n) } func stringtoslicebyte(buf *tmpBuf, s string) []byte { var b []byte if buf != nil && len(s) <= len(buf) { *buf = tmpBuf{} b = buf[:len(s)] } else { b = rawbyteslice(len(s)) } copy(b, s) return b } func stringtoslicerune(buf *[tmpStringBufSize]rune, s string) []rune { // two passes. // unlike slicerunetostring, no race because strings are immutable. n := 0 for range s { n++ } var a []rune if buf != nil && n <= len(buf) { *buf = [tmpStringBufSize]rune{} a = buf[:n] } else { a = rawruneslice(n) } n = 0 for _, r := range s { a[n] = r n++ } return a } func slicerunetostring(buf *tmpBuf, a []rune) string { if raceenabled && len(a) > 0 { racereadrangepc(unsafe.Pointer(&a[0]), uintptr(len(a))*unsafe.Sizeof(a[0]), getcallerpc(), abi.FuncPCABIInternal(slicerunetostring)) } if msanenabled && len(a) > 0 { msanread(unsafe.Pointer(&a[0]), uintptr(len(a))*unsafe.Sizeof(a[0])) } if asanenabled && len(a) > 0 { asanread(unsafe.Pointer(&a[0]), uintptr(len(a))*unsafe.Sizeof(a[0])) } var dum [4]byte size1 := 0 for _, r := range a { size1 += encoderune(dum[:], r) } s, b := rawstringtmp(buf, size1+3) size2 := 0 for _, r := range a { // check for race if size2 >= size1 { break } size2 += encoderune(b[size2:], r) } return s[:size2] } type stringStruct struct { str unsafe.Pointer len int } // Variant with *byte pointer type for DWARF debugging. type stringStructDWARF struct { str *byte len int } func stringStructOf(sp *string) *stringStruct { return (*stringStruct)(unsafe.Pointer(sp)) } func intstring(buf *[4]byte, v int64) (s string) { var b []byte if buf != nil { b = buf[:] s = slicebytetostringtmp(&b[0], len(b)) } else { s, b = rawstring(4) } if int64(rune(v)) != v { v = runeError } n := encoderune(b, rune(v)) return s[:n] } // rawstring allocates storage for a new string. The returned // string and byte slice both refer to the same storage. // The storage is not zeroed. Callers should use // b to set the string contents and then drop b. func rawstring(size int) (s string, b []byte) { p := mallocgc(uintptr(size), nil, false) return unsafe.String((*byte)(p), size), unsafe.Slice((*byte)(p), size) } // rawbyteslice allocates a new byte slice. The byte slice is not zeroed. func rawbyteslice(size int) (b []byte) { cap := roundupsize(uintptr(size), true) p := mallocgc(cap, nil, false) if cap != uintptr(size) { memclrNoHeapPointers(add(p, uintptr(size)), cap-uintptr(size)) } *(*slice)(unsafe.Pointer(&b)) = slice{p, size, int(cap)} return } // rawruneslice allocates a new rune slice. The rune slice is not zeroed. func rawruneslice(size int) (b []rune) { if uintptr(size) > maxAlloc/4 { throw("out of memory") } mem := roundupsize(uintptr(size)*4, true) p := mallocgc(mem, nil, false) if mem != uintptr(size)*4 { memclrNoHeapPointers(add(p, uintptr(size)*4), mem-uintptr(size)*4) } *(*slice)(unsafe.Pointer(&b)) = slice{p, size, int(mem / 4)} return } // used by cmd/cgo func gobytes(p *byte, n int) (b []byte) { if n == 0 { return make([]byte, 0) } if n < 0 || uintptr(n) > maxAlloc { panic(errorString("gobytes: length out of range")) } bp := mallocgc(uintptr(n), nil, false) memmove(bp, unsafe.Pointer(p), uintptr(n)) *(*slice)(unsafe.Pointer(&b)) = slice{bp, n, n} return } // This is exported via linkname to assembly in syscall (for Plan9). // //go:linkname gostring func gostring(p *byte) string { l := findnull(p) if l == 0 { return "" } s, b := rawstring(l) memmove(unsafe.Pointer(&b[0]), unsafe.Pointer(p), uintptr(l)) return s } // internal_syscall_gostring is a version of gostring for internal/syscall/unix. // //go:linkname internal_syscall_gostring internal/syscall/unix.gostring func internal_syscall_gostring(p *byte) string { return gostring(p) } func gostringn(p *byte, l int) string { if l == 0 { return "" } s, b := rawstring(l) memmove(unsafe.Pointer(&b[0]), unsafe.Pointer(p), uintptr(l)) return s } func hasPrefix(s, prefix string) bool { return len(s) >= len(prefix) && s[:len(prefix)] == prefix } func hasSuffix(s, suffix string) bool { return len(s) >= len(suffix) && s[len(s)-len(suffix):] == suffix } const ( maxUint64 = ^uint64(0) maxInt64 = int64(maxUint64 >> 1) ) // atoi64 parses an int64 from a string s. // The bool result reports whether s is a number // representable by a value of type int64. func atoi64(s string) (int64, bool) { if s == "" { return 0, false } neg := false if s[0] == '-' { neg = true s = s[1:] } un := uint64(0) for i := 0; i < len(s); i++ { c := s[i] if c < '0' || c > '9' { return 0, false } if un > maxUint64/10 { // overflow return 0, false } un *= 10 un1 := un + uint64(c) - '0' if un1 < un { // overflow return 0, false } un = un1 } if !neg && un > uint64(maxInt64) { return 0, false } if neg && un > uint64(maxInt64)+1 { return 0, false } n := int64(un) if neg { n = -n } return n, true } // atoi is like atoi64 but for integers // that fit into an int. func atoi(s string) (int, bool) { if n, ok := atoi64(s); n == int64(int(n)) { return int(n), ok } return 0, false } // atoi32 is like atoi but for integers // that fit into an int32. func atoi32(s string) (int32, bool) { if n, ok := atoi64(s); n == int64(int32(n)) { return int32(n), ok } return 0, false } // parseByteCount parses a string that represents a count of bytes. // // s must match the following regular expression: // // ^[0-9]+(([KMGT]i)?B)?$ // // In other words, an integer byte count with an optional unit // suffix. Acceptable suffixes include one of // - KiB, MiB, GiB, TiB which represent binary IEC/ISO 80000 units, or // - B, which just represents bytes. // // Returns an int64 because that's what its callers want and receive, // but the result is always non-negative. func parseByteCount(s string) (int64, bool) { // The empty string is not valid. if s == "" { return 0, false } // Handle the easy non-suffix case. last := s[len(s)-1] if last >= '0' && last <= '9' { n, ok := atoi64(s) if !ok || n < 0 { return 0, false } return n, ok } // Failing a trailing digit, this must always end in 'B'. // Also at this point there must be at least one digit before // that B. if last != 'B' || len(s) < 2 { return 0, false } // The one before that must always be a digit or 'i'. if c := s[len(s)-2]; c >= '0' && c <= '9' { // Trivial 'B' suffix. n, ok := atoi64(s[:len(s)-1]) if !ok || n < 0 { return 0, false } return n, ok } else if c != 'i' { return 0, false } // Finally, we need at least 4 characters now, for the unit // prefix and at least one digit. if len(s) < 4 { return 0, false } power := 0 switch s[len(s)-3] { case 'K': power = 1 case 'M': power = 2 case 'G': power = 3 case 'T': power = 4 default: // Invalid suffix. return 0, false } m := uint64(1) for i := 0; i < power; i++ { m *= 1024 } n, ok := atoi64(s[:len(s)-3]) if !ok || n < 0 { return 0, false } un := uint64(n) if un > maxUint64/m { // Overflow. return 0, false } un *= m if un > uint64(maxInt64) { // Overflow. return 0, false } return int64(un), true } //go:nosplit func findnull(s *byte) int { if s == nil { return 0 } // Avoid IndexByteString on Plan 9 because it uses SSE instructions // on x86 machines, and those are classified as floating point instructions, // which are illegal in a note handler. if GOOS == "plan9" { p := (*[maxAlloc/2 - 1]byte)(unsafe.Pointer(s)) l := 0 for p[l] != 0 { l++ } return l } // pageSize is the unit we scan at a time looking for NULL. // It must be the minimum page size for any architecture Go // runs on. It's okay (just a minor performance loss) if the // actual system page size is larger than this value. const pageSize = 4096 offset := 0 ptr := unsafe.Pointer(s) // IndexByteString uses wide reads, so we need to be careful // with page boundaries. Call IndexByteString on // [ptr, endOfPage) interval. safeLen := int(pageSize - uintptr(ptr)%pageSize) for { t := *(*string)(unsafe.Pointer(&stringStruct{ptr, safeLen})) // Check one page at a time. if i := bytealg.IndexByteString(t, 0); i != -1 { return offset + i } // Move to next page ptr = unsafe.Pointer(uintptr(ptr) + uintptr(safeLen)) offset += safeLen safeLen = pageSize } } func findnullw(s *uint16) int { if s == nil { return 0 } p := (*[maxAlloc/2/2 - 1]uint16)(unsafe.Pointer(s)) l := 0 for p[l] != 0 { l++ } return l } //go:nosplit func gostringnocopy(str *byte) string { ss := stringStruct{str: unsafe.Pointer(str), len: findnull(str)} s := *(*string)(unsafe.Pointer(&ss)) return s } func gostringw(strw *uint16) string { var buf [8]byte str := (*[maxAlloc/2/2 - 1]uint16)(unsafe.Pointer(strw)) n1 := 0 for i := 0; str[i] != 0; i++ { n1 += encoderune(buf[:], rune(str[i])) } s, b := rawstring(n1 + 4) n2 := 0 for i := 0; str[i] != 0; i++ { // check for race if n2 >= n1 { break } n2 += encoderune(b[n2:], rune(str[i])) } b[n2] = 0 // for luck return s[:n2] }