source: code/trunk/vendor/golang.org/x/sys/unix/dirent.go@ 69

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris

package unix

import "unsafe"

// readInt returns the size-bytes unsigned integer in native byte order at offset off.
func readInt(b []byte, off, size uintptr) (u uint64, ok bool) {
        if len(b) < int(off+size) {
                return 0, false
        }
        if isBigEndian {
                return readIntBE(b[off:], size), true
        }
        return readIntLE(b[off:], size), true
}

func readIntBE(b []byte, size uintptr) uint64 {
        switch size {
        case 1:
                return uint64(b[0])
        case 2:
                _ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
                return uint64(b[1]) | uint64(b[0])<<8
        case 4:
                _ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
                return uint64(b[3]) | uint64(b[2])<<8 | uint64(b[1])<<16 | uint64(b[0])<<24
        case 8:
                _ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
                return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
                        uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
        default:
                panic("syscall: readInt with unsupported size")
        }
}

func readIntLE(b []byte, size uintptr) uint64 {
        switch size {
        case 1:
                return uint64(b[0])
        case 2:
                _ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
                return uint64(b[0]) | uint64(b[1])<<8
        case 4:
                _ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
                return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24
        case 8:
                _ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
                return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
                        uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
        default:
                panic("syscall: readInt with unsupported size")
        }
}

// ParseDirent parses up to max directory entries in buf,
// appending the names to names. It returns the number of
// bytes consumed from buf, the number of entries added
// to names, and the new names slice.
func ParseDirent(buf []byte, max int, names []string) (consumed int, count int, newnames []string) {
        origlen := len(buf)
        count = 0
        for max != 0 && len(buf) > 0 {
                reclen, ok := direntReclen(buf)
                if !ok || reclen > uint64(len(buf)) {
                        return origlen, count, names
                }
                rec := buf[:reclen]
                buf = buf[reclen:]
                ino, ok := direntIno(rec)
                if !ok {
                        break
                }
                if ino == 0 { // File absent in directory.
                        continue
                }
                const namoff = uint64(unsafe.Offsetof(Dirent{}.Name))
                namlen, ok := direntNamlen(rec)
                if !ok || namoff+namlen > uint64(len(rec)) {
                        break
                }
                name := rec[namoff : namoff+namlen]
                for i, c := range name {
                        if c == 0 {
                                name = name[:i]
                                break
                        }
                }
                // Check for useless names before allocating a string.
                if string(name) == "." || string(name) == ".." {
                        continue
                }
                max--
                count++
                names = append(names, string(name))
        }
        return origlen - len(buf), count, names
}