rss-tools/vendor/go.etcd.io/bbolt/bolt_unix.go (view raw)
| 1 | //go:build !windows && !plan9 && !solaris && !aix && !android |
| 2 | |
| 3 | package bbolt |
| 4 | |
| 5 | import ( |
| 6 | "fmt" |
| 7 | "syscall" |
| 8 | "time" |
| 9 | "unsafe" |
| 10 | |
| 11 | "golang.org/x/sys/unix" |
| 12 | |
| 13 | "go.etcd.io/bbolt/errors" |
| 14 | "go.etcd.io/bbolt/internal/common" |
| 15 | ) |
| 16 | |
| 17 | // flock acquires an advisory lock on a file descriptor. |
| 18 | func flock(db *DB, exclusive bool, timeout time.Duration) error { |
| 19 | var t time.Time |
| 20 | if timeout != 0 { |
| 21 | t = time.Now() |
| 22 | } |
| 23 | fd := db.file.Fd() |
| 24 | flag := syscall.LOCK_NB |
| 25 | if exclusive { |
| 26 | flag |= syscall.LOCK_EX |
| 27 | } else { |
| 28 | flag |= syscall.LOCK_SH |
| 29 | } |
| 30 | for { |
| 31 | // Attempt to obtain an exclusive lock. |
| 32 | err := syscall.Flock(int(fd), flag) |
| 33 | if err == nil { |
| 34 | return nil |
| 35 | } else if err != syscall.EWOULDBLOCK { |
| 36 | return err |
| 37 | } |
| 38 | |
| 39 | // If we timed out then return an error. |
| 40 | if timeout != 0 && time.Since(t) > timeout-flockRetryTimeout { |
| 41 | return errors.ErrTimeout |
| 42 | } |
| 43 | |
| 44 | // Wait for a bit and try again. |
| 45 | time.Sleep(flockRetryTimeout) |
| 46 | } |
| 47 | } |
| 48 | |
| 49 | // funlock releases an advisory lock on a file descriptor. |
| 50 | func funlock(db *DB) error { |
| 51 | return syscall.Flock(int(db.file.Fd()), syscall.LOCK_UN) |
| 52 | } |
| 53 | |
| 54 | // mmap memory maps a DB's data file. |
| 55 | func mmap(db *DB, sz int) error { |
| 56 | // Map the data file to memory. |
| 57 | b, err := unix.Mmap(int(db.file.Fd()), 0, sz, syscall.PROT_READ, syscall.MAP_SHARED|db.MmapFlags) |
| 58 | if err != nil { |
| 59 | return err |
| 60 | } |
| 61 | |
| 62 | // Advise the kernel that the mmap is accessed randomly. |
| 63 | err = unix.Madvise(b, syscall.MADV_RANDOM) |
| 64 | if err != nil && err != syscall.ENOSYS { |
| 65 | // Ignore not implemented error in kernel because it still works. |
| 66 | return fmt.Errorf("madvise: %s", err) |
| 67 | } |
| 68 | |
| 69 | // Save the original byte slice and convert to a byte array pointer. |
| 70 | db.dataref = b |
| 71 | db.data = (*[common.MaxMapSize]byte)(unsafe.Pointer(&b[0])) |
| 72 | db.datasz = sz |
| 73 | return nil |
| 74 | } |
| 75 | |
| 76 | // munmap unmaps a DB's data file from memory. |
| 77 | func munmap(db *DB) error { |
| 78 | // Ignore the unmap if we have no mapped data. |
| 79 | if db.dataref == nil { |
| 80 | return nil |
| 81 | } |
| 82 | |
| 83 | // Unmap using the original byte slice. |
| 84 | err := unix.Munmap(db.dataref) |
| 85 | db.dataref = nil |
| 86 | db.data = nil |
| 87 | db.datasz = 0 |
| 88 | return err |
| 89 | } |