mirror of
https://github.com/go-gitea/gitea.git
synced 2024-12-22 06:18:10 +08:00
117 lines
3.6 KiB
Go
117 lines
3.6 KiB
Go
// 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 file.
|
|
|
|
// This file defines the common package interface and contains a little bit of
|
|
// factored out logic.
|
|
|
|
// Package mmap allows mapping files into memory. It tries to provide a simple, reasonably portable interface,
|
|
// but doesn't go out of its way to abstract away every little platform detail.
|
|
// This specifically means:
|
|
// * forked processes may or may not inherit mappings
|
|
// * a file's timestamp may or may not be updated by writes through mappings
|
|
// * specifying a size larger than the file's actual size can increase the file's size
|
|
// * If the mapped file is being modified by another process while your program's running, don't expect consistent results between platforms
|
|
package mmap
|
|
|
|
import (
|
|
"errors"
|
|
"os"
|
|
"reflect"
|
|
"unsafe"
|
|
)
|
|
|
|
const (
|
|
// RDONLY maps the memory read-only.
|
|
// Attempts to write to the MMap object will result in undefined behavior.
|
|
RDONLY = 0
|
|
// RDWR maps the memory as read-write. Writes to the MMap object will update the
|
|
// underlying file.
|
|
RDWR = 1 << iota
|
|
// COPY maps the memory as copy-on-write. Writes to the MMap object will affect
|
|
// memory, but the underlying file will remain unchanged.
|
|
COPY
|
|
// If EXEC is set, the mapped memory is marked as executable.
|
|
EXEC
|
|
)
|
|
|
|
const (
|
|
// If the ANON flag is set, the mapped memory will not be backed by a file.
|
|
ANON = 1 << iota
|
|
)
|
|
|
|
// MMap represents a file mapped into memory.
|
|
type MMap []byte
|
|
|
|
// Map maps an entire file into memory.
|
|
// If ANON is set in flags, f is ignored.
|
|
func Map(f *os.File, prot, flags int) (MMap, error) {
|
|
return MapRegion(f, -1, prot, flags, 0)
|
|
}
|
|
|
|
// MapRegion maps part of a file into memory.
|
|
// The offset parameter must be a multiple of the system's page size.
|
|
// If length < 0, the entire file will be mapped.
|
|
// If ANON is set in flags, f is ignored.
|
|
func MapRegion(f *os.File, length int, prot, flags int, offset int64) (MMap, error) {
|
|
if offset%int64(os.Getpagesize()) != 0 {
|
|
return nil, errors.New("offset parameter must be a multiple of the system's page size")
|
|
}
|
|
|
|
var fd uintptr
|
|
if flags&ANON == 0 {
|
|
fd = uintptr(f.Fd())
|
|
if length < 0 {
|
|
fi, err := f.Stat()
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
length = int(fi.Size())
|
|
}
|
|
} else {
|
|
if length <= 0 {
|
|
return nil, errors.New("anonymous mapping requires non-zero length")
|
|
}
|
|
fd = ^uintptr(0)
|
|
}
|
|
return mmap(length, uintptr(prot), uintptr(flags), fd, offset)
|
|
}
|
|
|
|
func (m *MMap) header() *reflect.SliceHeader {
|
|
return (*reflect.SliceHeader)(unsafe.Pointer(m))
|
|
}
|
|
|
|
// Lock keeps the mapped region in physical memory, ensuring that it will not be
|
|
// swapped out.
|
|
func (m MMap) Lock() error {
|
|
dh := m.header()
|
|
return lock(dh.Data, uintptr(dh.Len))
|
|
}
|
|
|
|
// Unlock reverses the effect of Lock, allowing the mapped region to potentially
|
|
// be swapped out.
|
|
// If m is already unlocked, aan error will result.
|
|
func (m MMap) Unlock() error {
|
|
dh := m.header()
|
|
return unlock(dh.Data, uintptr(dh.Len))
|
|
}
|
|
|
|
// Flush synchronizes the mapping's contents to the file's contents on disk.
|
|
func (m MMap) Flush() error {
|
|
dh := m.header()
|
|
return flush(dh.Data, uintptr(dh.Len))
|
|
}
|
|
|
|
// Unmap deletes the memory mapped region, flushes any remaining changes, and sets
|
|
// m to nil.
|
|
// Trying to read or write any remaining references to m after Unmap is called will
|
|
// result in undefined behavior.
|
|
// Unmap should only be called on the slice value that was originally returned from
|
|
// a call to Map. Calling Unmap on a derived slice may cause errors.
|
|
func (m *MMap) Unmap() error {
|
|
dh := m.header()
|
|
err := unmap(dh.Data, uintptr(dh.Len))
|
|
*m = nil
|
|
return err
|
|
}
|