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-rw-r--r--src/pkg/os/file.go207
1 files changed, 118 insertions, 89 deletions
diff --git a/src/pkg/os/file.go b/src/pkg/os/file.go
index 4335d45e5..4acf35d67 100644
--- a/src/pkg/os/file.go
+++ b/src/pkg/os/file.go
@@ -3,41 +3,66 @@
// license that can be found in the LICENSE file.
// Package os provides a platform-independent interface to operating system
-// functionality. The design is Unix-like.
+// functionality. The design is Unix-like, although the error handling is
+// Go-like; failing calls return values of type error rather than error numbers.
+// Often, more information is available within the error. For example,
+// if a call that takes a file name fails, such as Open or Stat, the error
+// will include the failing file name when printed and will be of type
+// *PathError, which may be unpacked for more information.
+//
// The os interface is intended to be uniform across all operating systems.
// Features not generally available appear in the system-specific package syscall.
+//
+// Here is a simple example, opening a file and reading some of it.
+//
+// file, err := os.Open("file.go") // For read access.
+// if err != nil {
+// log.Fatal(err)
+// }
+//
+// If the open fails, the error string will be self-explanatory, like
+//
+// open file.go: no such file or directory
+//
+// The file's data can then be read into a slice of bytes. Read and
+// Write take their byte counts from the length of the argument slice.
+//
+// data := make([]byte, 100)
+// count, err := file.Read(data)
+// if err != nil {
+// log.Fatal(err)
+// }
+// fmt.Printf("read %d bytes: %q\n", count, data[:count])
+//
package os
import (
+ "io"
"syscall"
)
// Name returns the name of the file as presented to Open.
-func (file *File) Name() string { return file.name }
+func (f *File) Name() string { return f.name }
// Stdin, Stdout, and Stderr are open Files pointing to the standard input,
// standard output, and standard error file descriptors.
var (
- Stdin = NewFile(syscall.Stdin, "/dev/stdin")
- Stdout = NewFile(syscall.Stdout, "/dev/stdout")
- Stderr = NewFile(syscall.Stderr, "/dev/stderr")
+ Stdin = NewFile(uintptr(syscall.Stdin), "/dev/stdin")
+ Stdout = NewFile(uintptr(syscall.Stdout), "/dev/stdout")
+ Stderr = NewFile(uintptr(syscall.Stderr), "/dev/stderr")
)
// Flags to Open wrapping those of the underlying system. Not all flags
// may be implemented on a given system.
const (
- O_RDONLY int = syscall.O_RDONLY // open the file read-only.
- O_WRONLY int = syscall.O_WRONLY // open the file write-only.
- O_RDWR int = syscall.O_RDWR // open the file read-write.
- O_APPEND int = syscall.O_APPEND // append data to the file when writing.
- O_ASYNC int = syscall.O_ASYNC // generate a signal when I/O is available.
- O_CREATE int = syscall.O_CREAT // create a new file if none exists.
- O_EXCL int = syscall.O_EXCL // used with O_CREATE, file must not exist
- O_NOCTTY int = syscall.O_NOCTTY // do not make file the controlling tty.
- O_NONBLOCK int = syscall.O_NONBLOCK // open in non-blocking mode.
- O_NDELAY int = O_NONBLOCK // synonym for O_NONBLOCK
- O_SYNC int = syscall.O_SYNC // open for synchronous I/O.
- O_TRUNC int = syscall.O_TRUNC // if possible, truncate file when opened.
+ O_RDONLY int = syscall.O_RDONLY // open the file read-only.
+ O_WRONLY int = syscall.O_WRONLY // open the file write-only.
+ O_RDWR int = syscall.O_RDWR // open the file read-write.
+ O_APPEND int = syscall.O_APPEND // append data to the file when writing.
+ O_CREATE int = syscall.O_CREAT // create a new file if none exists.
+ O_EXCL int = syscall.O_EXCL // used with O_CREATE, file must not exist
+ O_SYNC int = syscall.O_SYNC // open for synchronous I/O.
+ O_TRUNC int = syscall.O_TRUNC // if possible, truncate file when opened.
)
// Seek whence values.
@@ -47,52 +72,54 @@ const (
SEEK_END int = 2 // seek relative to the end
)
-type eofError int
-
-func (eofError) String() string { return "EOF" }
+// LinkError records an error during a link or symlink or rename
+// system call and the paths that caused it.
+type LinkError struct {
+ Op string
+ Old string
+ New string
+ Err error
+}
-// EOF is the Error returned by Read when no more input is available.
-// Functions should return EOF only to signal a graceful end of input.
-// If the EOF occurs unexpectedly in a structured data stream,
-// the appropriate error is either io.ErrUnexpectedEOF or some other error
-// giving more detail.
-var EOF Error = eofError(0)
+func (e *LinkError) Error() string {
+ return e.Op + " " + e.Old + " " + e.New + ": " + e.Err.Error()
+}
// Read reads up to len(b) bytes from the File.
-// It returns the number of bytes read and an Error, if any.
-// EOF is signaled by a zero count with err set to EOF.
-func (file *File) Read(b []byte) (n int, err Error) {
- if file == nil {
- return 0, EINVAL
+// It returns the number of bytes read and an error, if any.
+// EOF is signaled by a zero count with err set to io.EOF.
+func (f *File) Read(b []byte) (n int, err error) {
+ if f == nil {
+ return 0, ErrInvalid
}
- n, e := file.read(b)
+ n, e := f.read(b)
if n < 0 {
n = 0
}
- if n == 0 && !iserror(e) {
- return 0, EOF
+ if n == 0 && len(b) > 0 && e == nil {
+ return 0, io.EOF
}
- if iserror(e) {
- err = &PathError{"read", file.name, Errno(e)}
+ if e != nil {
+ err = &PathError{"read", f.name, e}
}
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
+// It returns the number of bytes read and the error, if any.
+// ReadAt always returns a non-nil error when n < len(b).
+// At end of file, that error is io.EOF.
+func (f *File) ReadAt(b []byte, off int64) (n int, err error) {
+ if f == nil {
+ return 0, ErrInvalid
}
for len(b) > 0 {
- m, e := file.pread(b, off)
- if m == 0 && !iserror(e) {
- return n, EOF
+ m, e := f.pread(b, off)
+ if m == 0 && e == nil {
+ return n, io.EOF
}
- if iserror(e) {
- err = &PathError{"read", file.name, Errno(e)}
+ if e != nil {
+ err = &PathError{"read", f.name, e}
break
}
n += m
@@ -103,36 +130,36 @@ func (file *File) ReadAt(b []byte, off int64) (n int, err Error) {
}
// Write writes len(b) bytes to the File.
-// It returns the number of bytes written and an Error, if any.
-// 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
+// It returns the number of bytes written and an error, if any.
+// Write returns a non-nil error when n != len(b).
+func (f *File) Write(b []byte) (n int, err error) {
+ if f == nil {
+ return 0, ErrInvalid
}
- n, e := file.write(b)
+ n, e := f.write(b)
if n < 0 {
n = 0
}
- epipecheck(file, e)
+ epipecheck(f, e)
- if iserror(e) {
- err = &PathError{"write", file.name, Errno(e)}
+ if e != nil {
+ err = &PathError{"write", f.name, e}
}
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
+// It returns the number of bytes written and an error, if any.
+// WriteAt returns a non-nil error when n != len(b).
+func (f *File) WriteAt(b []byte, off int64) (n int, err error) {
+ if f == nil {
+ return 0, ErrInvalid
}
for len(b) > 0 {
- m, e := file.pwrite(b, off)
- if iserror(e) {
- err = &PathError{"write", file.name, Errno(e)}
+ m, e := f.pwrite(b, off)
+ if e != nil {
+ err = &PathError{"write", f.name, e}
break
}
n += m
@@ -145,50 +172,52 @@ func (file *File) WriteAt(b []byte, off int64) (n int, err Error) {
// 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.
-// It returns the new offset and an Error, if any.
-func (file *File) Seek(offset int64, whence int) (ret int64, err Error) {
- r, e := file.seek(offset, whence)
- if !iserror(e) && file.dirinfo != nil && r != 0 {
+// It returns the new offset and an error, if any.
+func (f *File) Seek(offset int64, whence int) (ret int64, err error) {
+ r, e := f.seek(offset, whence)
+ if e == nil && f.dirinfo != nil && r != 0 {
e = syscall.EISDIR
}
- if iserror(e) {
- return 0, &PathError{"seek", file.name, Errno(e)}
+ if e != nil {
+ return 0, &PathError{"seek", f.name, e}
}
return r, nil
}
// WriteString is like Write, but writes the contents of string s rather than
// an array of bytes.
-func (file *File) WriteString(s string) (ret int, err Error) {
- if file == nil {
- return 0, EINVAL
+func (f *File) WriteString(s string) (ret int, err error) {
+ if f == nil {
+ return 0, ErrInvalid
}
- return file.Write([]byte(s))
+ return f.Write([]byte(s))
}
// Mkdir creates a new directory with the specified name and permission bits.
-// It returns an error, if any.
-func Mkdir(name string, perm uint32) Error {
- e := syscall.Mkdir(name, perm)
- if iserror(e) {
- return &PathError{"mkdir", name, Errno(e)}
+// If there is an error, it will be of type *PathError.
+func Mkdir(name string, perm FileMode) error {
+ e := syscall.Mkdir(name, syscallMode(perm))
+ if e != nil {
+ return &PathError{"mkdir", name, e}
}
return nil
}
// Chdir changes the current working directory to the named directory.
-func Chdir(dir string) Error {
- if e := syscall.Chdir(dir); iserror(e) {
- return &PathError{"chdir", dir, Errno(e)}
+// If there is an error, it will be of type *PathError.
+func Chdir(dir string) error {
+ if e := syscall.Chdir(dir); e != nil {
+ return &PathError{"chdir", dir, e}
}
return nil
}
// Chdir changes the current working directory to the file,
// which must be a directory.
-func (f *File) Chdir() Error {
- if e := syscall.Fchdir(f.fd); iserror(e) {
- return &PathError{"chdir", f.name, Errno(e)}
+// If there is an error, it will be of type *PathError.
+func (f *File) Chdir() error {
+ if e := syscall.Fchdir(f.fd); e != nil {
+ return &PathError{"chdir", f.name, e}
}
return nil
}
@@ -196,8 +225,8 @@ func (f *File) Chdir() Error {
// Open opens the named file for reading. If successful, methods on
// the returned file can be used for reading; the associated file
// descriptor has mode O_RDONLY.
-// It returns the File and an Error, if any.
-func Open(name string) (file *File, err Error) {
+// If there is an error, it will be of type *PathError.
+func Open(name string) (file *File, err error) {
return OpenFile(name, O_RDONLY, 0)
}
@@ -205,7 +234,7 @@ func Open(name string) (file *File, err Error) {
// it if it already exists. If successful, methods on the returned
// File can be used for I/O; the associated file descriptor has mode
// O_RDWR.
-// It returns the File and an Error, if any.
-func Create(name string) (file *File, err Error) {
+// If there is an error, it will be of type *PathError.
+func Create(name string) (file *File, err error) {
return OpenFile(name, O_RDWR|O_CREATE|O_TRUNC, 0666)
}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-24 10:12:11 +0000