mirror of
https://github.com/golang/go
synced 2024-10-03 03:01:21 -06:00
67faca7d9c
This change breaks out most of the atomics functions in the runtime into package runtime/internal/atomic. It adds some basic support in the toolchain for runtime packages, and also modifies linux/arm atomics to remove the dependency on the runtime's mutex. The mutexes have been replaced with spinlocks. all trybots are happy! In addition to the trybots, I've tested on the darwin/arm64 builder, on the darwin/arm builder, and on a ppc64le machine. Change-Id: I6698c8e3cf3834f55ce5824059f44d00dc8e3c2f Reviewed-on: https://go-review.googlesource.com/14204 Run-TryBot: Michael Matloob <matloob@golang.org> Reviewed-by: Russ Cox <rsc@golang.org>
443 lines
9.6 KiB
Go
443 lines
9.6 KiB
Go
// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package runtime
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import (
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"runtime/internal/atomic"
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"unsafe"
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)
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// The constant is known to the compiler.
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// There is no fundamental theory behind this number.
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const tmpStringBufSize = 32
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type tmpBuf [tmpStringBufSize]byte
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// concatstrings implements a Go string concatenation x+y+z+...
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// The operands are passed in the slice a.
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// If buf != nil, the compiler has determined that the result does not
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// escape the calling function, so the string data can be stored in buf
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// if small enough.
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func concatstrings(buf *tmpBuf, a []string) string {
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idx := 0
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l := 0
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count := 0
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for i, x := range a {
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n := len(x)
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if n == 0 {
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continue
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}
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if l+n < l {
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throw("string concatenation too long")
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}
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l += n
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count++
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idx = i
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}
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if count == 0 {
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return ""
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}
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// If there is just one string and either it is not on the stack
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// or our result does not escape the calling frame (buf != nil),
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// then we can return that string directly.
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if count == 1 && (buf != nil || !stringDataOnStack(a[idx])) {
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return a[idx]
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}
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s, b := rawstringtmp(buf, l)
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l = 0
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for _, x := range a {
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copy(b[l:], x)
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l += len(x)
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}
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return s
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}
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func concatstring2(buf *tmpBuf, a [2]string) string {
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return concatstrings(buf, a[:])
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}
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func concatstring3(buf *tmpBuf, a [3]string) string {
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return concatstrings(buf, a[:])
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}
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func concatstring4(buf *tmpBuf, a [4]string) string {
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return concatstrings(buf, a[:])
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}
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func concatstring5(buf *tmpBuf, a [5]string) string {
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return concatstrings(buf, a[:])
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}
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// Buf is a fixed-size buffer for the result,
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// it is not nil if the result does not escape.
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func slicebytetostring(buf *tmpBuf, b []byte) string {
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l := len(b)
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if l == 0 {
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// Turns out to be a relatively common case.
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// Consider that you want to parse out data between parens in "foo()bar",
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// you find the indices and convert the subslice to string.
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return ""
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}
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if raceenabled && l > 0 {
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racereadrangepc(unsafe.Pointer(&b[0]),
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uintptr(l),
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getcallerpc(unsafe.Pointer(&b)),
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funcPC(slicebytetostring))
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}
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if msanenabled && l > 0 {
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msanread(unsafe.Pointer(&b[0]), uintptr(l))
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}
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s, c := rawstringtmp(buf, l)
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copy(c, b)
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return s
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}
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// stringDataOnStack reports whether the string's data is
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// stored on the current goroutine's stack.
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func stringDataOnStack(s string) bool {
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ptr := uintptr(stringStructOf(&s).str)
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stk := getg().stack
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return stk.lo <= ptr && ptr < stk.hi
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}
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func rawstringtmp(buf *tmpBuf, l int) (s string, b []byte) {
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if buf != nil && l <= len(buf) {
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b = buf[:l]
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s = slicebytetostringtmp(b)
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} else {
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s, b = rawstring(l)
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}
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return
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}
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func slicebytetostringtmp(b []byte) string {
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// Return a "string" referring to the actual []byte bytes.
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// This is only for use by internal compiler optimizations
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// that know that the string form will be discarded before
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// the calling goroutine could possibly modify the original
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// slice or synchronize with another goroutine.
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// First such case is a m[string(k)] lookup where
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// m is a string-keyed map and k is a []byte.
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// Second such case is "<"+string(b)+">" concatenation where b is []byte.
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// Third such case is string(b)=="foo" comparison where b is []byte.
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if raceenabled && len(b) > 0 {
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racereadrangepc(unsafe.Pointer(&b[0]),
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uintptr(len(b)),
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getcallerpc(unsafe.Pointer(&b)),
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funcPC(slicebytetostringtmp))
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}
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if msanenabled && len(b) > 0 {
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msanread(unsafe.Pointer(&b[0]), uintptr(len(b)))
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}
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return *(*string)(unsafe.Pointer(&b))
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}
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func stringtoslicebyte(buf *tmpBuf, s string) []byte {
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var b []byte
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if buf != nil && len(s) <= len(buf) {
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b = buf[:len(s)]
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} else {
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b = rawbyteslice(len(s))
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}
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copy(b, s)
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return b
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}
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func stringtoslicebytetmp(s string) []byte {
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// Return a slice referring to the actual string bytes.
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// This is only for use by internal compiler optimizations
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// that know that the slice won't be mutated.
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// The only such case today is:
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// for i, c := range []byte(str)
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str := stringStructOf(&s)
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ret := slice{array: unsafe.Pointer(str.str), len: str.len, cap: str.len}
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return *(*[]byte)(unsafe.Pointer(&ret))
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}
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func stringtoslicerune(buf *[tmpStringBufSize]rune, s string) []rune {
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// two passes.
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// unlike slicerunetostring, no race because strings are immutable.
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n := 0
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t := s
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for len(s) > 0 {
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_, k := charntorune(s)
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s = s[k:]
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n++
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}
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var a []rune
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if buf != nil && n <= len(buf) {
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a = buf[:n]
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} else {
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a = rawruneslice(n)
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}
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n = 0
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for len(t) > 0 {
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r, k := charntorune(t)
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t = t[k:]
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a[n] = r
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n++
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}
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return a
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}
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func slicerunetostring(buf *tmpBuf, a []rune) string {
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if raceenabled && len(a) > 0 {
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racereadrangepc(unsafe.Pointer(&a[0]),
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uintptr(len(a))*unsafe.Sizeof(a[0]),
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getcallerpc(unsafe.Pointer(&a)),
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funcPC(slicerunetostring))
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}
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if msanenabled && len(a) > 0 {
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msanread(unsafe.Pointer(&a[0]), uintptr(len(a))*unsafe.Sizeof(a[0]))
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}
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var dum [4]byte
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size1 := 0
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for _, r := range a {
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size1 += runetochar(dum[:], r)
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}
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s, b := rawstringtmp(buf, size1+3)
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size2 := 0
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for _, r := range a {
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// check for race
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if size2 >= size1 {
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break
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}
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size2 += runetochar(b[size2:], r)
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}
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return s[:size2]
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}
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type stringStruct struct {
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str unsafe.Pointer
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len int
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}
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// Variant with *byte pointer type for DWARF debugging.
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type stringStructDWARF struct {
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str *byte
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len int
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}
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func stringStructOf(sp *string) *stringStruct {
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return (*stringStruct)(unsafe.Pointer(sp))
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}
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func intstring(buf *[4]byte, v int64) string {
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var s string
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var b []byte
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if buf != nil {
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b = buf[:]
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s = slicebytetostringtmp(b)
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} else {
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s, b = rawstring(4)
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}
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n := runetochar(b, rune(v))
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return s[:n]
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}
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// stringiter returns the index of the next
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// rune after the rune that starts at s[k].
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func stringiter(s string, k int) int {
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if k >= len(s) {
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// 0 is end of iteration
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return 0
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}
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c := s[k]
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if c < runeself {
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return k + 1
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}
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// multi-char rune
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_, n := charntorune(s[k:])
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return k + n
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}
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// stringiter2 returns the rune that starts at s[k]
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// and the index where the next rune starts.
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func stringiter2(s string, k int) (int, rune) {
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if k >= len(s) {
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// 0 is end of iteration
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return 0, 0
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}
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c := s[k]
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if c < runeself {
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return k + 1, rune(c)
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}
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// multi-char rune
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r, n := charntorune(s[k:])
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return k + n, r
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}
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// rawstring allocates storage for a new string. The returned
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// string and byte slice both refer to the same storage.
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// The storage is not zeroed. Callers should use
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// b to set the string contents and then drop b.
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func rawstring(size int) (s string, b []byte) {
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p := mallocgc(uintptr(size), nil, flagNoScan|flagNoZero)
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stringStructOf(&s).str = p
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stringStructOf(&s).len = size
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*(*slice)(unsafe.Pointer(&b)) = slice{p, size, size}
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for {
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ms := maxstring
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if uintptr(size) <= uintptr(ms) || atomic.Casuintptr((*uintptr)(unsafe.Pointer(&maxstring)), uintptr(ms), uintptr(size)) {
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return
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}
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}
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}
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// rawbyteslice allocates a new byte slice. The byte slice is not zeroed.
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func rawbyteslice(size int) (b []byte) {
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cap := roundupsize(uintptr(size))
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p := mallocgc(cap, nil, flagNoScan|flagNoZero)
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if cap != uintptr(size) {
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memclr(add(p, uintptr(size)), cap-uintptr(size))
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}
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*(*slice)(unsafe.Pointer(&b)) = slice{p, size, int(cap)}
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return
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}
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// rawruneslice allocates a new rune slice. The rune slice is not zeroed.
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func rawruneslice(size int) (b []rune) {
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if uintptr(size) > _MaxMem/4 {
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throw("out of memory")
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}
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mem := roundupsize(uintptr(size) * 4)
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p := mallocgc(mem, nil, flagNoScan|flagNoZero)
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if mem != uintptr(size)*4 {
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memclr(add(p, uintptr(size)*4), mem-uintptr(size)*4)
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}
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*(*slice)(unsafe.Pointer(&b)) = slice{p, size, int(mem / 4)}
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return
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}
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// used by cmd/cgo
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func gobytes(p *byte, n int) []byte {
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if n == 0 {
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return make([]byte, 0)
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}
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x := make([]byte, n)
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memmove(unsafe.Pointer(&x[0]), unsafe.Pointer(p), uintptr(n))
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return x
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}
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func gostring(p *byte) string {
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l := findnull(p)
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if l == 0 {
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return ""
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}
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s, b := rawstring(l)
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memmove(unsafe.Pointer(&b[0]), unsafe.Pointer(p), uintptr(l))
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return s
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}
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func gostringn(p *byte, l int) string {
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if l == 0 {
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return ""
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}
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s, b := rawstring(l)
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memmove(unsafe.Pointer(&b[0]), unsafe.Pointer(p), uintptr(l))
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return s
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}
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func index(s, t string) int {
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if len(t) == 0 {
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return 0
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}
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for i := 0; i < len(s); i++ {
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if s[i] == t[0] && hasprefix(s[i:], t) {
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return i
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}
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}
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return -1
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}
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func contains(s, t string) bool {
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return index(s, t) >= 0
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}
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func hasprefix(s, t string) bool {
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return len(s) >= len(t) && s[:len(t)] == t
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}
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func atoi(s string) int {
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n := 0
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for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
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n = n*10 + int(s[0]) - '0'
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s = s[1:]
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}
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return n
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}
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//go:nosplit
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func findnull(s *byte) int {
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if s == nil {
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return 0
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}
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p := (*[_MaxMem/2 - 1]byte)(unsafe.Pointer(s))
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l := 0
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for p[l] != 0 {
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l++
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}
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return l
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}
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func findnullw(s *uint16) int {
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if s == nil {
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return 0
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}
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p := (*[_MaxMem/2/2 - 1]uint16)(unsafe.Pointer(s))
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l := 0
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for p[l] != 0 {
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l++
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}
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return l
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}
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var maxstring uintptr = 256 // a hint for print
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//go:nosplit
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func gostringnocopy(str *byte) string {
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ss := stringStruct{str: unsafe.Pointer(str), len: findnull(str)}
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s := *(*string)(unsafe.Pointer(&ss))
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for {
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ms := maxstring
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if uintptr(len(s)) <= ms || atomic.Casuintptr(&maxstring, ms, uintptr(len(s))) {
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break
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}
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}
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return s
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}
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func gostringw(strw *uint16) string {
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var buf [8]byte
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str := (*[_MaxMem/2/2 - 1]uint16)(unsafe.Pointer(strw))
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n1 := 0
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for i := 0; str[i] != 0; i++ {
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n1 += runetochar(buf[:], rune(str[i]))
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}
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s, b := rawstring(n1 + 4)
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n2 := 0
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for i := 0; str[i] != 0; i++ {
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// check for race
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if n2 >= n1 {
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break
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}
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n2 += runetochar(b[n2:], rune(str[i]))
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}
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b[n2] = 0 // for luck
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return s[:n2]
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}
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