diff options
Diffstat (limited to 'vendor/golang.org/x/sys/unix/syscall_linux.go')
| -rw-r--r-- | vendor/golang.org/x/sys/unix/syscall_linux.go | 50 |
1 files changed, 32 insertions, 18 deletions
diff --git a/vendor/golang.org/x/sys/unix/syscall_linux.go b/vendor/golang.org/x/sys/unix/syscall_linux.go index c5a98440e..d839962e6 100644 --- a/vendor/golang.org/x/sys/unix/syscall_linux.go +++ b/vendor/golang.org/x/sys/unix/syscall_linux.go @@ -1973,36 +1973,46 @@ func Signalfd(fd int, sigmask *Sigset_t, flags int) (newfd int, err error) { //sys preadv2(fd int, iovs []Iovec, offs_l uintptr, offs_h uintptr, flags int) (n int, err error) = SYS_PREADV2 //sys pwritev2(fd int, iovs []Iovec, offs_l uintptr, offs_h uintptr, flags int) (n int, err error) = SYS_PWRITEV2 -func bytes2iovec(bs [][]byte) []Iovec { - iovecs := make([]Iovec, len(bs)) - for i, b := range bs { - iovecs[i].SetLen(len(b)) +// minIovec is the size of the small initial allocation used by +// Readv, Writev, etc. +// +// This small allocation gets stack allocated, which lets the +// common use case of len(iovs) <= minIovs avoid more expensive +// heap allocations. +const minIovec = 8 + +// appendBytes converts bs to Iovecs and appends them to vecs. +func appendBytes(vecs []Iovec, bs [][]byte) []Iovec { + for _, b := range bs { + var v Iovec + v.SetLen(len(b)) if len(b) > 0 { - iovecs[i].Base = &b[0] + v.Base = &b[0] } else { - iovecs[i].Base = (*byte)(unsafe.Pointer(&_zero)) + v.Base = (*byte)(unsafe.Pointer(&_zero)) } + vecs = append(vecs, v) } - return iovecs + return vecs } -// offs2lohi splits offs into its lower and upper unsigned long. On 64-bit -// systems, hi will always be 0. On 32-bit systems, offs will be split in half. -// preadv/pwritev chose this calling convention so they don't need to add a -// padding-register for alignment on ARM. +// offs2lohi splits offs into its low and high order bits. func offs2lohi(offs int64) (lo, hi uintptr) { - return uintptr(offs), uintptr(uint64(offs) >> SizeofLong) + const longBits = SizeofLong * 8 + return uintptr(offs), uintptr(uint64(offs) >> longBits) } func Readv(fd int, iovs [][]byte) (n int, err error) { - iovecs := bytes2iovec(iovs) + iovecs := make([]Iovec, 0, minIovec) + iovecs = appendBytes(iovecs, iovs) n, err = readv(fd, iovecs) readvRacedetect(iovecs, n, err) return n, err } func Preadv(fd int, iovs [][]byte, offset int64) (n int, err error) { - iovecs := bytes2iovec(iovs) + iovecs := make([]Iovec, 0, minIovec) + iovecs = appendBytes(iovecs, iovs) lo, hi := offs2lohi(offset) n, err = preadv(fd, iovecs, lo, hi) readvRacedetect(iovecs, n, err) @@ -2010,7 +2020,8 @@ func Preadv(fd int, iovs [][]byte, offset int64) (n int, err error) { } func Preadv2(fd int, iovs [][]byte, offset int64, flags int) (n int, err error) { - iovecs := bytes2iovec(iovs) + iovecs := make([]Iovec, 0, minIovec) + iovecs = appendBytes(iovecs, iovs) lo, hi := offs2lohi(offset) n, err = preadv2(fd, iovecs, lo, hi, flags) readvRacedetect(iovecs, n, err) @@ -2037,7 +2048,8 @@ func readvRacedetect(iovecs []Iovec, n int, err error) { } func Writev(fd int, iovs [][]byte) (n int, err error) { - iovecs := bytes2iovec(iovs) + iovecs := make([]Iovec, 0, minIovec) + iovecs = appendBytes(iovecs, iovs) if raceenabled { raceReleaseMerge(unsafe.Pointer(&ioSync)) } @@ -2047,7 +2059,8 @@ func Writev(fd int, iovs [][]byte) (n int, err error) { } func Pwritev(fd int, iovs [][]byte, offset int64) (n int, err error) { - iovecs := bytes2iovec(iovs) + iovecs := make([]Iovec, 0, minIovec) + iovecs = appendBytes(iovecs, iovs) if raceenabled { raceReleaseMerge(unsafe.Pointer(&ioSync)) } @@ -2058,7 +2071,8 @@ func Pwritev(fd int, iovs [][]byte, offset int64) (n int, err error) { } func Pwritev2(fd int, iovs [][]byte, offset int64, flags int) (n int, err error) { - iovecs := bytes2iovec(iovs) + iovecs := make([]Iovec, 0, minIovec) + iovecs = appendBytes(iovecs, iovs) if raceenabled { raceReleaseMerge(unsafe.Pointer(&ioSync)) } |