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@krishnasrinivas
Created May 24, 2016 08:36
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package main
import (
"fmt"
"log"
"os"
"path"
"runtime"
"strings"
"syscall"
"unsafe"
)
const (
// readDirentBufSize for syscall.ReadDirent() to hold multiple
// directory entries in one buffer. golang source uses 4096 as
// buffer size whereas we want 25 times larger to save lots of
// entries to avoid multiple syscall.ReadDirent() call.
readDirentBufSize = 4096 * 25
)
// actual length of the byte array from the c - world.
func clen(n []byte) int {
for i := 0; i < len(n); i++ {
if n[i] == 0 {
return i
}
}
return len(n)
}
// parseDirents - inspired from
// https://golang.org/src/syscall/syscall_<os>.go
func parseDirents(dirPath string, buf []byte) (entries []string, err error) {
bufidx := 0
for bufidx < len(buf) {
dirent := (*syscall.Dirent)(unsafe.Pointer(&buf[bufidx]))
// On non-Linux operating systems for rec length of zero means
// we have reached EOF break out.
if runtime.GOOS != "linux" && dirent.Reclen == 0 {
break
}
bufidx += int(dirent.Reclen)
bytes := (*[10000]byte)(unsafe.Pointer(&dirent.Name[0]))
var name = string(bytes[0:clen(bytes[:])])
// Reserved names skip them.
if name == "." || name == ".." {
continue
}
switch dirent.Type {
case syscall.DT_DIR:
entries = append(entries, name+"/")
case syscall.DT_REG:
entries = append(entries, name)
case syscall.DT_LNK, syscall.DT_UNKNOWN:
// If its symbolic link, follow the link using os.Stat()
// On Linux XFS does not implement d_type for on disk
// format << v5. Fall back to Stat().
var fi os.FileInfo
fi, err = os.Stat(path.Join(dirPath, name))
if err != nil {
// If file does not exist, we continue and skip it.
// Could happen if it was deleted in the middle while
// this list was being performed.
if os.IsNotExist(err) {
err = nil
continue
}
return nil, err
}
if fi.IsDir() {
entries = append(entries, fi.Name()+"/")
} else if fi.Mode().IsRegular() {
entries = append(entries, fi.Name())
}
default:
// Skip entries which are not file or directory.
continue
}
}
return entries, nil
}
// Return all the entries at the directory dirPath.
func readDir(dirPath string) (entries []string, err error) {
buf := make([]byte, readDirentBufSize)
d, err := os.Open(dirPath)
if err != nil {
// File is really not found.
if os.IsNotExist(err) {
return nil, err
}
// File path cannot be verified since one of the parents is a file.
if strings.Contains(err.Error(), "not a directory") {
return nil, err
}
return nil, err
}
defer d.Close()
fd := int(d.Fd())
for {
nbuf, err := syscall.ReadDirent(fd, buf)
if err != nil {
return nil, err
}
if nbuf <= 0 {
break
}
var tmpEntries []string
if tmpEntries, err = parseDirents(dirPath, buf[:nbuf]); err != nil {
return nil, err
}
entries = append(entries, tmpEntries...)
}
return
}
func main() {
entries, err := readDir(".")
if err != nil {
log.Fatal(err)
}
for _, entry := range entries {
_, err := os.Stat(entry + "/xl.json")
if err != nil {
log.Fatal(err)
}
}
fmt.Println(len(entries))
}
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