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//go:build !purego && (aix || android || darwin || dragonfly || freebsd || illumos || ios || linux || netbsd || openbsd || plan9 || solaris)
// +build !purego
// +build aix android darwin dragonfly freebsd illumos ios linux netbsd openbsd plan9 solaris
// TODO: replace the above with go:build unix once Go 1.19 is the lowest
// supported version
package buffer
import (
"golang.org/x/sys/unix"
)
type Buffer struct {
n int
pg int
mmap []byte
}
func New(n int) (Buffer, error) {
pg := unix.Getpagesize()
full := ((n+(pg-1))/pg + 2) * pg
b, err := unix.Mmap(-1, 0, full, unix.PROT_NONE, unix.MAP_ANON|unix.MAP_PRIVATE)
if err != nil {
return Buffer{}, err
}
if n > 0 {
err = unix.Mprotect(b[pg:full-pg], unix.PROT_READ|unix.PROT_WRITE)
if err != nil {
unix.Munmap(b)
return Buffer{}, err
}
}
return Buffer{
n: n,
pg: pg,
mmap: b,
}, nil
}
func (a *Buffer) ProtectHead() []byte {
head := a.pg
return a.mmap[head : head+a.n : head+a.n]
}
func (a *Buffer) ProtectTail() []byte {
tail := len(a.mmap) - a.pg - a.n
return a.mmap[tail : tail+a.n : tail+a.n]
}
func (a *Buffer) Release() {
unix.Munmap(a.mmap)
}
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