mirror of
https://github.com/rclone/rclone
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43 lines
1.2 KiB
Go
43 lines
1.2 KiB
Go
// Package mmap implements a large block memory allocator using
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// anonymous memory maps.
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// +build windows
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package mmap
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import (
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"reflect"
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"unsafe"
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"github.com/pkg/errors"
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"golang.org/x/sys/windows"
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)
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// Alloc allocates size bytes and returns a slice containing them. If
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// the allocation fails it will return with an error. This is best
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// used for allocations which are a multiple of the PageSize.
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func Alloc(size int) ([]byte, error) {
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p, err := windows.VirtualAlloc(0, uintptr(size), windows.MEM_COMMIT, windows.PAGE_READWRITE)
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if err != nil {
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return nil, errors.Wrap(err, "mmap: failed to allocate memory for buffer")
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}
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var mem []byte
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sh := (*reflect.SliceHeader)(unsafe.Pointer(&mem))
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sh.Data = p
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sh.Len = size
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sh.Cap = size
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return mem, nil
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}
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// Free frees buffers allocated by Alloc. Note it should be passed
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// the same slice (not a derived slice) that Alloc returned. If the
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// free fails it will return with an error.
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func Free(mem []byte) error {
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sh := (*reflect.SliceHeader)(unsafe.Pointer(&mem))
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err := windows.VirtualFree(sh.Data, 0, windows.MEM_RELEASE)
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if err != nil {
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return errors.Wrap(err, "mmap: failed to unmap memory")
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}
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return nil
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}
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