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b809e71d6f
reflect.SliceHeader is deprecated, however the replacement gives a go vet warning so this disables the lint warning in one use of reflect.SliceHeader and replaces it in the other.
52 lines
1.5 KiB
Go
52 lines
1.5 KiB
Go
// Package mmap implements a large block memory allocator using
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// anonymous memory maps.
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//go:build windows
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package mmap
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import (
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"fmt"
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"reflect"
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"unsafe"
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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, fmt.Errorf("mmap: failed to allocate memory for buffer: %w", err)
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}
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// SliceHeader is deprecated...
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var mem []byte
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sh := (*reflect.SliceHeader)(unsafe.Pointer(&mem)) // nolint:staticcheck
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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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// ...However the correct code gives a go vet warning
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// "possible misuse of unsafe.Pointer"
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//
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// Maybe there is a different way of writing this, but none of
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// the allowed uses of unsafe.Pointer seemed to cover it other
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// than using SliceHeader (use 6 of unsafe.Pointer).
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//
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// return unsafe.Slice((*byte)(unsafe.Pointer(p)), size), 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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p := unsafe.SliceData(mem)
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err := windows.VirtualFree(uintptr(unsafe.Pointer(p)), 0, windows.MEM_RELEASE)
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if err != nil {
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return fmt.Errorf("mmap: failed to unmap memory: %w", err)
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}
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return nil
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}
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