Fix Readdirnames to behave properly if reading in little pieces. Requires storing some
state in the FD.
This is Darwin only. Next CL will make Readdir use Readdirnames to generate its files
and move Readdir into portable code, as well as fix Readdirnames for Linux.
R=rsc
DELTA=116 (79 added, 12 deleted, 25 changed)
OCL=24756
CL=24768
diff --git a/src/lib/os/dir_amd64_darwin.go b/src/lib/os/dir_amd64_darwin.go
index f140182..e66f540 100644
--- a/src/lib/os/dir_amd64_darwin.go
+++ b/src/lib/os/dir_amd64_darwin.go
@@ -10,36 +10,44 @@
"unsafe";
)
+const (
+ blockSize = 4096 // TODO(r): use statfs
+)
+
// Negative count means read until EOF.
func Readdirnames(fd *FD, count int) (names []string, err *os.Error) {
- // Getdirentries needs the file offset - it's too hard for the kernel to remember
- // a number it already has written down.
- base, err1 := syscall.Seek(fd.fd, 0, 1);
- if err1 != 0 {
- return nil, os.ErrnoToError(err1)
+ // If this fd has no dirinfo, create one.
+ if fd.dirinfo == nil {
+ fd.dirinfo = new(DirInfo);
+ // The buffer must be at least a block long.
+ // TODO(r): use fstatfs to find fs block size.
+ fd.dirinfo.buf = make([]byte, blockSize);
}
- // The buffer must be at least a block long.
- // TODO(r): use fstatfs to find fs block size.
- var buf = make([]byte, 8192);
- names = make([]string, 0, 100); // TODO: could be smarter about size
- for {
- if count == 0 {
- break
- }
- ret, err2 := syscall.Getdirentries(fd.fd, &buf[0], int64(len(buf)), &base);
- if ret < 0 || err2 != 0 {
- return names, os.ErrnoToError(err2)
- }
- if ret == 0 {
- break
- }
- for w, i := uintptr(0),uintptr(0); i < uintptr(ret); i += w {
- if count == 0 {
- break
+ d := fd.dirinfo;
+ size := count;
+ if size < 0 {
+ size = 100
+ }
+ names = make([]string, 0, size); // Empty with room to grow.
+ for count != 0 {
+ // Refill the buffer if necessary
+ if d.bufp == d.nbuf {
+ var errno int64;
+ // Final argument is (basep *int64) and the syscall doesn't take nil.
+ d.nbuf, errno = syscall.Getdirentries(fd.fd, &d.buf[0], int64(len(d.buf)), new(int64));
+ if d.nbuf < 0 {
+ return names, os.ErrnoToError(errno)
}
- dirent := unsafe.Pointer((uintptr(unsafe.Pointer(&buf[0])) + i)).(*syscall.Dirent);
- w = uintptr(dirent.Reclen);
- if dirent.Ino == 0 {
+ if d.nbuf == 0 {
+ break // EOF
+ }
+ d.bufp = 0;
+ }
+ // Drain the buffer
+ for count != 0 && d.bufp < d.nbuf {
+ dirent := unsafe.Pointer(&d.buf[d.bufp]).(*syscall.Dirent);
+ d.bufp += int64(dirent.Reclen);
+ if dirent.Ino == 0 { // File absent in directory.
continue
}
count--;
@@ -54,7 +62,7 @@
names[len(names)-1] = string(dirent.Name[0:dirent.Namlen]);
}
}
- return names, nil;
+ return names, nil
}
// TODO(r): see comment in dir_amd64_linux.go
@@ -74,7 +82,7 @@
}
// The buffer must be at least a block long.
// TODO(r): use fstatfs to find fs block size.
- var buf = make([]byte, 8192);
+ var buf = make([]byte, blockSize);
dirs = make([]Dir, 0, 100); // TODO: could be smarter about size
for {
if count == 0 {
@@ -106,7 +114,7 @@
}
dirs = dirs[0:len(dirs)+1];
filename := string(dirent.Name[0:dirent.Namlen]);
- dirp, err := Stat(dirname + filename);
+ dirp, err := Lstat(dirname + filename);
if dirp == nil || err != nil {
dirs[len(dirs)-1].Name = filename; // rest will be zeroed out
} else {
diff --git a/src/lib/os/os_file.go b/src/lib/os/os_file.go
index 25b14d0..cd924bd 100644
--- a/src/lib/os/os_file.go
+++ b/src/lib/os/os_file.go
@@ -7,10 +7,18 @@
import syscall "syscall"
import os "os"
+// Auxiliary information if the FD describes a directory
+type DirInfo struct { // TODO(r): 6g bug means this can't be private
+ buf []byte; // buffer for directory I/O
+ nbuf int64; // length of buf; return value from Getdirentries
+ bufp int64; // location of next record in buf.
+}
+
// FDs are wrappers for file descriptors
type FD struct {
fd int64;
name string;
+ dirinfo *DirInfo; // nil unless directory being read
}
func (fd *FD) Fd() int64 {
@@ -25,7 +33,7 @@
if fd < 0 {
return nil
}
- return &FD{fd, name}
+ return &FD{fd, name, nil}
}
var (
@@ -90,6 +98,17 @@
return int(r), ErrnoToError(e)
}
+func (fd *FD) Seek(offset int64, whence int) (ret int64, err *Error) {
+ r, e := syscall.Seek(fd.fd, offset, int64(whence));
+ if e != 0 {
+ return -1, ErrnoToError(e)
+ }
+ if fd.dirinfo != nil && r != 0 {
+ return -1, ErrnoToError(syscall.EISDIR)
+ }
+ return r, nil
+}
+
func (fd *FD) WriteString(s string) (ret int, err *Error) {
if fd == nil {
return 0, EINVAL
diff --git a/src/lib/os/os_test.go b/src/lib/os/os_test.go
index 5e0c2bf..5c37a6b 100644
--- a/src/lib/os/os_test.go
+++ b/src/lib/os/os_test.go
@@ -101,11 +101,11 @@
fd, err := Open(dir, O_RDONLY, 0);
defer fd.Close();
if err != nil {
- t.Fatalf("open %q failed: %s\n", dir, err.String());
+ t.Fatalf("open %q failed: %v\n", dir, err);
}
s, err2 := Readdirnames(fd, -1);
if err2 != nil {
- t.Fatal("readdirnames . failed:", err);
+ t.Fatalf("readdirnames %q failed: %v", err2);
}
for i, m := range contents {
found := false;
@@ -127,11 +127,11 @@
fd, err := Open(dir, O_RDONLY, 0);
defer fd.Close();
if err != nil {
- t.Fatalf("open %q failed: %s\n", dir, err.String());
+ t.Fatalf("open %q failed: %v", dir, err);
}
s, err2 := Readdir(fd, -1);
if err2 != nil {
- t.Fatal("readdir . failed:", err);
+ t.Fatalf("readdir %q failed: %v", dir, err2);
}
for i, m := range contents {
found := false;
@@ -158,3 +158,46 @@
testReaddir(".", dot, t);
testReaddir("/etc", etc, t);
}
+
+// Read the directory one entry at a time.
+func smallReaddirnames(fd *FD, length int, t *testing.T) []string {
+ names := make([]string, length);
+ count := 0;
+ for {
+ d, err := Readdirnames(fd, 1);
+ if err != nil {
+ t.Fatalf("readdir %q failed: %v", fd.Name(), err);
+ }
+ if len(d) == 0 {
+ break
+ }
+ names[count] = d[0];
+ count++;
+ }
+ return names[0:count]
+}
+
+// Check that reading a directory one entry at a time gives the same result
+// as reading it all at once.
+func TestReaddirnamesOneAtATime(t *testing.T) {
+ dir := "/usr/bin"; // big directory that doesn't change often.
+ fd, err := Open(dir, O_RDONLY, 0);
+ defer fd.Close();
+ if err != nil {
+ t.Fatalf("open %q failed: %v", dir, err);
+ }
+ all, err1 := Readdirnames(fd, -1);
+ if err1 != nil {
+ t.Fatalf("readdirnames %q failed: %v", dir, err1);
+ }
+ fd1, err2 := Open(dir, O_RDONLY, 0);
+ if err2 != nil {
+ t.Fatalf("open %q failed: %v\n", dir, err2);
+ }
+ small := smallReaddirnames(fd1, len(all)+100, t); // +100 in case we screw up
+ for i, n := range all {
+ if small[i] != n {
+ t.Errorf("small read %q %q mismatch: %v\n", small[i], n);
+ }
+ }
+}
