ioutil_linux.go (1712B)
1 // Copyright 2010 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-GO file. 4 5 // Modifications Copyright 2020 The Libc Authors. All rights reserved. 6 // Use of this source code is governed by a BSD-style 7 // license that can be found in the LICENSE file. 8 9 package libc // import "modernc.org/libc" 10 11 import ( 12 "fmt" 13 "os" 14 "sync" 15 "time" 16 "unsafe" 17 18 "golang.org/x/sys/unix" 19 "modernc.org/libc/errno" 20 "modernc.org/libc/fcntl" 21 ) 22 23 // Random number state. 24 // We generate random temporary file names so that there's a good 25 // chance the file doesn't exist yet - keeps the number of tries in 26 // TempFile to a minimum. 27 var randState uint32 28 var randStateMu sync.Mutex 29 30 func reseed() uint32 { 31 return uint32(time.Now().UnixNano() + int64(os.Getpid())) 32 } 33 34 func nextRandom(x uintptr) { 35 randStateMu.Lock() 36 r := randState 37 if r == 0 { 38 r = reseed() 39 } 40 r = r*1664525 + 1013904223 // constants from Numerical Recipes 41 randState = r 42 randStateMu.Unlock() 43 copy((*RawMem)(unsafe.Pointer(x))[:6:6], fmt.Sprintf("%06d", int(1e9+r%1e9)%1e6)) 44 } 45 46 func tempFile(s, x uintptr, flags int32) (fd int, err error) { 47 const maxTry = 10000 48 nconflict := 0 49 flags |= int32(os.O_RDWR | os.O_CREATE | os.O_EXCL | unix.O_LARGEFILE) 50 for i := 0; i < maxTry; i++ { 51 nextRandom(x) 52 fdcwd := fcntl.AT_FDCWD 53 n, _, err := unix.Syscall6(unix.SYS_OPENAT, uintptr(fdcwd), s, uintptr(flags), 0600, 0, 0) 54 if err == 0 { 55 return int(n), nil 56 } 57 58 if err != errno.EEXIST { 59 return -1, err 60 } 61 62 if nconflict++; nconflict > 10 { 63 randStateMu.Lock() 64 randState = reseed() 65 nconflict = 0 66 randStateMu.Unlock() 67 } 68 } 69 return -1, unix.Errno(errno.EEXIST) 70 }