70 lines
1.6 KiB
Go
70 lines
1.6 KiB
Go
// Copyright 2010 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-GO file.
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// Modifications Copyright 2020 The Libc 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 libc // import "modernc.org/libc"
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import (
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"fmt"
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"os"
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"sync"
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"time"
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"unsafe"
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"golang.org/x/sys/unix"
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"modernc.org/libc/errno"
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"modernc.org/libc/fcntl"
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)
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// Random number state.
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// We generate random temporary file names so that there's a good
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// chance the file doesn't exist yet - keeps the number of tries in
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// TempFile to a minimum.
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var randState uint32
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var randStateMu sync.Mutex
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func reseed() uint32 {
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return uint32(time.Now().UnixNano() + int64(os.Getpid()))
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}
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func nextRandom(x uintptr) {
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randStateMu.Lock()
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r := randState
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if r == 0 {
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r = reseed()
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}
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r = r*1664525 + 1013904223 // constants from Numerical Recipes
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randState = r
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randStateMu.Unlock()
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copy((*RawMem)(unsafe.Pointer(x))[:6:6], fmt.Sprintf("%06d", int(1e9+r%1e9)%1e6))
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}
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func tempFile(s, x uintptr) (fd, err int) {
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const maxTry = 10000
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nconflict := 0
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for i := 0; i < maxTry; i++ {
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nextRandom(x)
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fdcwd := fcntl.AT_FDCWD
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n, _, err := unix.Syscall6(unix.SYS_OPENAT, uintptr(fdcwd), s, uintptr(os.O_RDWR|os.O_CREATE|os.O_EXCL|unix.O_LARGEFILE), 0600, 0, 0)
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if err == 0 {
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return int(n), 0
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}
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if err != errno.EEXIST {
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return -1, int(err)
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}
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if nconflict++; nconflict > 10 {
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randStateMu.Lock()
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randState = reseed()
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nconflict = 0
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randStateMu.Unlock()
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}
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}
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return -1, errno.EEXIST
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}
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