os.File.ReadAt/WriteAt
R=r
DELTA=84 (81 added, 0 deleted, 3 changed)
OCL=34006
CL=34006
diff --git a/src/pkg/os/file.go b/src/pkg/os/file.go
index 958a823..c9c0078 100644
--- a/src/pkg/os/file.go
+++ b/src/pkg/os/file.go
@@ -115,7 +115,7 @@
// It returns the number of bytes read and an Error, if any.
// EOF is signaled by a zero count with err set to EOF.
// TODO(r): Add Pread, Pwrite (maybe ReadAt, WriteAt).
-func (file *File) Read(b []byte) (ret int, err Error) {
+func (file *File) Read(b []byte) (n int, err Error) {
if file == nil {
return 0, EINVAL
}
@@ -132,10 +132,31 @@
return n, err
}
+// ReadAt reads len(b) bytes from the File starting at byte offset off.
+// It returns the number of bytes read and the Error, if any.
+// EOF is signaled by a zero count with err set to EOF.
+// ReadAt always returns a non-nil Error when n != len(b).
+func (file *File) ReadAt(b []byte, off int64) (n int, err Error) {
+ if file == nil {
+ return 0, EINVAL;
+ }
+ for len(b) > 0 {
+ m, e := syscall.Pread(file.fd, b, off);
+ n += m;
+ if e != 0 {
+ err = &PathError{"read", file.name, Errno(e)};
+ break;
+ }
+ b = b[m:len(b)];
+ off += int64(m);
+ }
+ return;
+}
+
// Write writes len(b) bytes to the File.
// It returns the number of bytes written and an Error, if any.
-// If the byte count differs from len(b), it usually implies an error occurred.
-func (file *File) Write(b []byte) (ret int, err Error) {
+// Write returns a non-nil Error when n != len(b).
+func (file *File) Write(b []byte) (n int, err Error) {
if file == nil {
return 0, EINVAL
}
@@ -157,6 +178,26 @@
return n, err
}
+// WriteAt writes len(b) bytes to the File starting at byte offset off.
+// It returns the number of bytes written and an Error, if any.
+// WriteAt returns a non-nil Error when n != len(b).
+func (file *File) WriteAt(b []byte, off int64) (n int, err Error) {
+ if file == nil {
+ return 0, EINVAL;
+ }
+ for len(b) > 0 {
+ m, e := syscall.Pwrite(file.fd, b, off);
+ n += m;
+ if e != 0 {
+ err = &PathError{"write", file.name, Errno(e)};
+ break;
+ }
+ b = b[m:len(b)];
+ off += int64(m);
+ }
+ return;
+}
+
// Seek sets the offset for the next Read or Write on file to offset, interpreted
// according to whence: 0 means relative to the origin of the file, 1 means
// relative to the current offset, and 2 means relative to the end.
