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// Copyright 2010 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-GO file.
// Modifications Copyright 2020 The Libc 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 libc // import "modernc.org/libc"
import (
"fmt"
"os"
"sync"
"time"
"unsafe"
"golang.org/x/sys/unix"
"modernc.org/libc/errno"
"modernc.org/libc/fcntl"
)
// Random number state.
// We generate random temporary file names so that there's a good
// chance the file doesn't exist yet - keeps the number of tries in
// TempFile to a minimum.
var randState uint32
var randStateMu sync.Mutex
func reseed() uint32 {
return uint32(time.Now().UnixNano() + int64(os.Getpid()))
}
func nextRandom(x uintptr) {
randStateMu.Lock()
r := randState
if r == 0 {
r = reseed()
}
r = r*1664525 + 1013904223 // constants from Numerical Recipes
randState = r
randStateMu.Unlock()
copy((*RawMem)(unsafe.Pointer(x))[:6:6], fmt.Sprintf("%06d", int(1e9+r%1e9)%1e6))
}
func tempFile(s, x uintptr, flags int32) (fd int, err error) {
const maxTry = 10000
nconflict := 0
flags |= int32(os.O_RDWR | os.O_CREATE | os.O_EXCL | unix.O_LARGEFILE)
for i := 0; i < maxTry; i++ {
nextRandom(x)
fdcwd := fcntl.AT_FDCWD
n, _, err := unix.Syscall6(unix.SYS_OPENAT, uintptr(fdcwd), s, uintptr(flags), 0600, 0, 0)
if err == 0 {
return int(n), nil
}
if err != errno.EEXIST {
return -1, err
}
if nconflict++; nconflict > 10 {
randStateMu.Lock()
randState = reseed()
nconflict = 0
randStateMu.Unlock()
}
}
return -1, unix.Errno(errno.EEXIST)
}
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