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