43 lines
1.2 KiB
Go
43 lines
1.2 KiB
Go
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// +build nacl linux js solaris
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package godirwalk
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import (
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"bytes"
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"reflect"
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"syscall"
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"unsafe"
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)
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// nameOffset is a compile time constant
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const nameOffset = int(unsafe.Offsetof(syscall.Dirent{}.Name))
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func nameFromDirent(de *syscall.Dirent) (name []byte) {
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// Because this GOOS' syscall.Dirent does not provide a field that specifies
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// the name length, this function must first calculate the max possible name
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// length, and then search for the NULL byte.
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ml := int(de.Reclen) - nameOffset
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// Convert syscall.Dirent.Name, which is array of int8, to []byte, by
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// overwriting Cap, Len, and Data slice header fields to the max possible
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// name length computed above, and finding the terminating NULL byte.
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sh := (*reflect.SliceHeader)(unsafe.Pointer(&name))
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sh.Cap = ml
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sh.Len = ml
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sh.Data = uintptr(unsafe.Pointer(&de.Name[0]))
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if index := bytes.IndexByte(name, 0); index >= 0 {
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// Found NULL byte; set slice's cap and len accordingly.
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sh.Cap = index
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sh.Len = index
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return
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}
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// NOTE: This branch is not expected, but included for defensive
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// programming, and provides a hard stop on the name based on the structure
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// field array size.
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sh.Cap = len(de.Name)
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sh.Len = sh.Cap
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return
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}
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