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// Copyright 2011 Evan Shaw. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE-MMAP-GO file.
// +build darwin dragonfly freebsd linux openbsd solaris netbsd
// Modifications (c) 2017 The Memory Authors.
package memory // import "modernc.org/memory"
import (
"os"
"syscall"
"unsafe"
)
const pageSizeLog = 20
var (
osPageMask = osPageSize - 1
osPageSize = os.Getpagesize()
)
func unmap(addr uintptr, size int) error {
_, _, errno := syscall.Syscall(syscall.SYS_MUNMAP, addr, uintptr(size), 0)
if errno != 0 {
return errno
}
return nil
}
// pageSize aligned.
func mmap(size int) (uintptr, int, error) {
size = roundup(size, osPageSize)
b, err := syscall.Mmap(-1, 0, size+pageSize, syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED|syscall.MAP_ANON)
if err != nil {
return 0, 0, err
}
n := len(b)
p := uintptr(unsafe.Pointer(&b[0]))
if p&uintptr(osPageMask) != 0 {
panic("internal error")
}
mod := int(p) & pageMask
if mod != 0 {
m := pageSize - mod
if err := unmap(p, m); err != nil {
return 0, 0, err
}
n -= m
p += uintptr(m)
}
if p&uintptr(pageMask) != 0 {
panic("internal error")
}
if n-size != 0 {
if err := unmap(p+uintptr(size), n-size); err != nil {
return 0, 0, err
}
}
return p, size, nil
}
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