2008-07-26 15:49:21 -06:00
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// Copyright 2009 The Go Authors. 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 file.
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2009-03-06 18:20:53 -07:00
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// This package contains an interface to the low-level operating system
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// primitives. The details vary depending on the underlying system.
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// Its primary use is inside other packages that provide a more portable
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// interface to the system, such as "os", "time" and "net". Use those
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// packages rather than this one if you can.
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// For details of the functions and data types in this package consult
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// the manuals for the appropriate operating system.
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2010-04-06 11:28:55 -06:00
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// These calls return errno == 0 to indicate success; otherwise
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// errno is an operating system error number describing the failure.
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2008-07-26 15:49:21 -06:00
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package syscall
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2011-04-06 15:52:02 -06:00
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import (
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"sync"
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"unsafe"
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)
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2009-06-01 23:14:57 -06:00
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// StringByteSlice returns a NUL-terminated slice of bytes
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// containing the text of s.
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func StringByteSlice(s string) []byte {
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2009-12-15 16:40:16 -07:00
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a := make([]byte, len(s)+1)
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2010-10-26 22:52:54 -06:00
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copy(a, s)
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2009-12-15 16:40:16 -07:00
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return a
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2009-06-01 23:14:57 -06:00
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}
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// StringBytePtr returns a pointer to a NUL-terminated array of bytes
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// containing the text of s.
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2009-12-15 16:40:16 -07:00
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func StringBytePtr(s string) *byte { return &StringByteSlice(s)[0] }
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2011-02-09 12:28:47 -07:00
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// Single-word zero for use when we need a valid pointer to 0 bytes.
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// See mksyscall.sh.
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var _zero uintptr
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2011-04-06 15:52:02 -06:00
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// Mmap manager, for use by operating system-specific implementations.
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type mmapper struct {
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sync.Mutex
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active map[*byte][]byte // active mappings; key is last byte in mapping
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mmap func(addr, length uintptr, prot, flags, fd int, offset int64) (uintptr, int)
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munmap func(addr uintptr, length uintptr) int
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}
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func (m *mmapper) Mmap(fd int, offset int64, length int, prot int, flags int) (data []byte, errno int) {
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if length <= 0 {
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return nil, EINVAL
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}
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// Map the requested memory.
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addr, errno := m.mmap(0, uintptr(length), prot, flags, fd, offset)
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if errno != 0 {
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return nil, errno
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}
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// Slice memory layout
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var sl = struct {
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addr uintptr
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len int
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cap int
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}{addr, length, length}
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// Use unsafe to turn sl into a []byte.
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b := *(*[]byte)(unsafe.Pointer(&sl))
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// Register mapping in m and return it.
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p := &b[cap(b)-1]
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m.Lock()
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defer m.Unlock()
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m.active[p] = b
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return b, 0
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}
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func (m *mmapper) Munmap(data []byte) (errno int) {
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if len(data) == 0 || len(data) != cap(data) {
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return EINVAL
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}
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// Find the base of the mapping.
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p := &data[cap(data)-1]
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m.Lock()
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defer m.Unlock()
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b := m.active[p]
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if b == nil || &b[0] != &data[0] {
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return EINVAL
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}
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// Unmap the memory and update m.
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if errno := m.munmap(uintptr(unsafe.Pointer(&b[0])), uintptr(len(b))); errno != 0 {
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return errno
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}
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m.active[p] = nil, false
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return 0
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}
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