60 lines
1.2 KiB
Go
60 lines
1.2 KiB
Go
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package mmap
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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 (
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PROT_READ = syscall.PROT_READ
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PROT_WRITE = syscall.PROT_WRITE
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)
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// Mmap creates a memory map of the given file. The flags argument should be a
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// combination of PROT_READ and PROT_WRITE. The size of the map will be the
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// file's size.
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func Map(f *os.File, flags int) ([]byte, error) {
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fi, err := f.Stat()
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if err != nil {
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return nil, err
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}
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size := fi.Size()
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addr, _, errno := syscall.Syscall6(
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syscall.SYS_MMAP,
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0, // addr: 0 => allow kernel to choose
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uintptr(size),
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uintptr(flags),
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uintptr(syscall.MAP_SHARED),
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f.Fd(),
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0) // offset: 0 => start of file
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if errno != 0 {
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return nil, syscall.Errno(errno)
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}
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return unsafe.Slice((*byte)(unsafe.Pointer(addr)), size), nil
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}
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// Munmap unmaps the data obtained by Map.
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func Unmap(data []byte) error {
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_, _, errno := syscall.Syscall(
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syscall.SYS_MUNMAP,
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uintptr(unsafe.Pointer(&data[:1][0])),
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uintptr(cap(data)),
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0)
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if errno != 0 {
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return syscall.Errno(errno)
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}
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return nil
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}
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func Sync(b []byte) (err error) {
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_p0 := unsafe.Pointer(&b[0])
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_, _, errno := syscall.Syscall(syscall.SYS_MSYNC, uintptr(_p0), uintptr(len(b)), uintptr(syscall.MS_SYNC))
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if errno != 0 {
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err = syscall.Errno(errno)
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}
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return
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}
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