document os
R=rsc
DELTA=143 (96 added, 0 deleted, 47 changed)
OCL=25876
CL=25888
diff --git a/src/lib/os/file.go b/src/lib/os/file.go
index b41f241..1fb2a64 100644
--- a/src/lib/os/file.go
+++ b/src/lib/os/file.go
@@ -2,6 +2,8 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
+// The os package provides a platform-independent interface to operating
+// system functionality. The design is Unix-like.
package os
import (
@@ -16,21 +18,25 @@
bufp int64; // location of next record in buf.
}
-// FDs are wrappers for file descriptors
+// FD represents an open file.
+// TODO(r): is FD the right name? Would File be better?
type FD struct {
fd int64;
name string;
dirinfo *dirInfo; // nil unless directory being read
}
+// Fd returns the integer Unix file descriptor referencing the open file.
func (fd *FD) Fd() int64 {
return fd.fd
}
+// Name returns the name of the file as presented to Open.
func (fd *FD) Name() string {
return fd.name
}
+// NewFD returns a new FD with the given file descriptor and name.
func NewFD(fd int64, name string) *FD {
if fd < 0 {
return nil
@@ -38,28 +44,35 @@
return &FD{fd, name, nil}
}
+// Stdin, Stdout, and Stderr are open FDs pointing to the standard input,
+// standard output, and standard error file descriptors.
var (
Stdin = NewFD(0, "/dev/stdin");
Stdout = NewFD(1, "/dev/stdout");
Stderr = NewFD(2, "/dev/stderr");
)
+// Flags to Open wrapping those of the underlying system. Not all flags
+// may be implemented on a given system.
const (
- O_RDONLY = syscall.O_RDONLY;
- O_WRONLY = syscall.O_WRONLY;
- O_RDWR = syscall.O_RDWR;
- O_APPEND = syscall.O_APPEND;
- O_ASYNC = syscall.O_ASYNC;
- O_CREAT = syscall.O_CREAT;
- O_NOCTTY = syscall.O_NOCTTY;
- O_NONBLOCK = syscall.O_NONBLOCK;
- O_NDELAY = O_NONBLOCK;
- O_SYNC = syscall.O_SYNC;
- O_TRUNC = syscall.O_TRUNC;
+ O_RDONLY = syscall.O_RDONLY; // open the file read-only.
+ O_WRONLY = syscall.O_WRONLY; // open the file write-only.
+ O_RDWR = syscall.O_RDWR; // open the file read-write.
+ O_APPEND = syscall.O_APPEND; // open the file append-only.
+ O_ASYNC = syscall.O_ASYNC; // generate a signal when I/O is available.
+ O_CREAT = syscall.O_CREAT; // create a new file if none exists.
+ O_NOCTTY = syscall.O_NOCTTY; // do not make file the controlling tty.
+ O_NONBLOCK = syscall.O_NONBLOCK; // open in non-blocking mode.
+ O_NDELAY = O_NONBLOCK; // synonym for O_NONBLOCK
+ O_SYNC = syscall.O_SYNC; // open for synchronous I/O.
+ O_TRUNC = syscall.O_TRUNC; // if possible, truncate file when opened.
)
-func Open(name string, mode int, flags int) (fd *FD, err *Error) {
- r, e := syscall.Open(name, int64(mode), int64(flags | syscall.O_CLOEXEC));
+// Open opens the named file with specified flag (O_RDONLY etc.) and perm, (0666 etc.)
+// if applicable. If successful, methods on the returned FD can be used for I/O.
+// It returns the FD and an Error, if any.
+func Open(name string, flag int, perm int) (fd *FD, err *Error) {
+ r, e := syscall.Open(name, int64(flag | syscall.O_CLOEXEC), int64(perm));
if e != 0 {
return nil, ErrnoToError(e);
}
@@ -73,6 +86,8 @@
return NewFD(r, name), ErrnoToError(e)
}
+// Close closes the FD, rendering it unusable for I/O.
+// It returns an Error, if any.
func (fd *FD) Close() *Error {
if fd == nil {
return EINVAL
@@ -82,6 +97,10 @@
return ErrnoToError(e)
}
+// Read reads up to len(b) bytes from the FD.
+// It returns the number of bytes read and an Error, if any.
+// EOF is signaled by a zero count with a nil Error.
+// TODO(r): Add Pread, Pwrite (maybe ReadAt, WriteAt).
func (fd *FD) Read(b []byte) (ret int, err *Error) {
if fd == nil {
return 0, EINVAL
@@ -96,6 +115,9 @@
return int(r), ErrnoToError(e)
}
+// Write writes len(b) bytes to the FD.
+// 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 (fd *FD) Write(b []byte) (ret int, err *Error) {
if fd == nil {
return 0, EINVAL
@@ -110,6 +132,10 @@
return int(r), ErrnoToError(e)
}
+// Seek sets the offset for the next Read or Write on FD 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.
+// It returns the new offset and an Error, if any.
func (fd *FD) Seek(offset int64, whence int) (ret int64, err *Error) {
r, e := syscall.Seek(fd.fd, offset, int64(whence));
if e != 0 {
@@ -121,6 +147,8 @@
return r, nil
}
+// WriteString is like Write, but writes the contents of string s rather than
+// an array of bytes.
func (fd *FD) WriteString(s string) (ret int, err *Error) {
if fd == nil {
return 0, EINVAL
@@ -132,12 +160,14 @@
return int(r), ErrnoToError(e)
}
-func Pipe() (fd1 *FD, fd2 *FD, err *Error) {
+// Pipe returns a connected pair of FDs; reads from r return bytes written to w.
+// It returns the FDs and an Error, if any.
+func Pipe() (r *FD, w *FD, err *Error) {
var p [2]int64;
// See ../syscall/exec.go for description of lock.
syscall.ForkLock.RLock();
- r, e := syscall.Pipe(&p);
+ ret, e := syscall.Pipe(&p);
if e != 0 {
syscall.ForkLock.RUnlock();
return nil, nil, ErrnoToError(e)
@@ -149,11 +179,17 @@
return NewFD(p[0], "|0"), NewFD(p[1], "|1"), nil
}
+// Mkdir creates a new directory with the specified name and permission bits.
+// It returns an error, if any.
func Mkdir(name string, perm int) *Error {
r, e := syscall.Mkdir(name, int64(perm));
return ErrnoToError(e)
}
+// Stat returns the Dir structure describing the named file. If the file
+// is a symbolic link, it returns information about the file the link
+// references.
+// It returns the Dir and an error, if any.
func Stat(name string) (dir *Dir, err *Error) {
stat := new(syscall.Stat_t);
r, e := syscall.Stat(name, stat);
@@ -163,6 +199,8 @@
return dirFromStat(name, new(Dir), stat), nil
}
+// Fstat returns the Dir structure describing the file associated with the FD.
+// It returns the Dir and an error, if any.
func Fstat(fd *FD) (dir *Dir, err *Error) {
stat := new(syscall.Stat_t);
r, e := syscall.Fstat(fd.fd, stat);
@@ -172,6 +210,9 @@
return dirFromStat(fd.name, new(Dir), stat), nil
}
+// Lstat returns the Dir structure describing the named file. If the file
+// is a symbolic link, it returns information about the link itself.
+// It returns the Dir and an error, if any.
func Lstat(name string) (dir *Dir, err *Error) {
stat := new(syscall.Stat_t);
r, e := syscall.Lstat(name, stat);
@@ -181,10 +222,21 @@
return dirFromStat(name, new(Dir), stat), nil
}
-// Non-portable function defined in operating-system-dependent file.
+// Readdirnames has a non-portable implemenation so its code is separated into an
+// operating-system-dependent file.
+
+// Readdirnames reads the contents of the directory associated with fd and
+// returns an array of up to count names, in directory order. Subsequent
+// calls on the same fd will yield further names.
+// A negative count means to read until EOF.
+// It returns the array and an Error, if any.
func Readdirnames(fd *FD, count int) (names []string, err *os.Error)
-// Negative count means read until EOF.
+// Readdir reads the contents of the directory associated with fd and
+// returns an array of up to count Dir structures, in directory order. Subsequent
+// calls on the same fd will yield further Dirs.
+// A negative count means to read until EOF.
+// It returns the array and an Error, if any.
func Readdir(fd *FD, count int) (dirs []Dir, err *os.Error) {
dirname := fd.name;
if dirname == "" {
