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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// This package provides basic interfaces to I/O primitives.
// Its primary job is to wrap existing implementations of such primitives,
// such as those in package os, into shared public interfaces that
// abstract the functionality.
// It also provides buffering primitives and some other basic operations.
package io
import (
"os";
)
// Error represents an unexpected I/O behavior.
type Error struct {
os.ErrorString
}
// ErrEOF means that data was expected, but a read got EOF instead.
var ErrEOF os.Error = &Error{"EOF"}
// ErrShortWrite means that a write accepted fewer bytes than requested
// but failed to return an explicit error.
var ErrShortWrite os.Error = &Error{"short write"}
// Reader is the interface that wraps the basic Read method.
// An implementation of Read is allowed to use all of p for
// scratch space during the call, even if it eventually returns
// n < len(p).
type Reader interface {
Read(p []byte) (n int, err os.Error);
}
// Writer is the interface that wraps the basic Write method.
type Writer interface {
Write(p []byte) (n int, err os.Error);
}
// Closer is the interface that wraps the basic Close method.
type Closer interface {
Close() os.Error;
}
// ReadWrite is the interface that groups the basic Read and Write methods.
type ReadWriter interface {
Reader;
Writer;
}
// ReadCloser is the interface that groups the basic Read and Close methods.
type ReadCloser interface {
Reader;
Closer;
}
// WriteCloser is the interface that groups the basic Write and Close methods.
type WriteCloser interface {
Writer;
Closer;
}
// ReadWriteCloser is the interface that groups the basic Read, Write and Close methods.
type ReadWriteCloser interface {
Reader;
Writer;
Closer;
}
// Convert a string to an array of bytes for easy marshaling.
func StringBytes(s string) []byte {
b := make([]byte, len(s));
for i := 0; i < len(s); i++ {
b[i] = s[i];
}
return b;
}
// WriteString writes the contents of the string s to w, which accepts an array of bytes.
func WriteString(w Writer, s string) (n int, err os.Error) {
return w.Write(StringBytes(s))
}
// ReadAtLeast reads r into buf until at least min bytes have been read,
// or until EOF or error.
func ReadAtLeast(r Reader, buf []byte, min int) (n int, err os.Error) {
n = 0;
for n < min {
nn, e := r.Read(buf[n:len(buf)]);
if nn > 0 {
n += nn
}
if e != nil {
return n, e
}
if nn <= 0 {
return n, ErrEOF // no error but insufficient data
}
}
return n, nil
}
// FullRead reads r until the buffer buf is full, or until EOF or error.
func FullRead(r Reader, buf []byte) (n int, err os.Error) {
// TODO(rsc): 6g bug prevents obvious return
n, err = ReadAtLeast(r, buf, len(buf));
return;
}
// Convert something that implements Read into something
// whose Reads are always FullReads
type fullRead struct {
r Reader;
}
func (fr *fullRead) Read(p []byte) (n int, err os.Error) {
n, err = FullRead(fr.r, p);
return n, err
}
// MakeFullReader takes r, an implementation of Read, and returns an object
// that still implements Read but always calls FullRead underneath.
func MakeFullReader(r Reader) Reader {
if fr, ok := r.(*fullRead); ok {
// already a fullRead
return r
}
return &fullRead{r}
}
// Copy n copies n bytes (or until EOF is reached) from src to dst.
// It returns the number of bytes copied and the error, if any.
func Copyn(src Reader, dst Writer, n int64) (written int64, err os.Error) {
buf := make([]byte, 32*1024);
for written < n {
l := len(buf);
if d := n - written; d < int64(l) {
l = int(d);
}
nr, er := src.Read(buf[0 : l]);
if nr > 0 {
nw, ew := dst.Write(buf[0 : nr]);
if nw > 0 {
written += int64(nw);
}
if ew != nil {
err = ew;
break;
}
if nr != nw {
err = os.EIO;
break;
}
}
if er != nil {
err = er;
break;
}
if nr == 0 {
err = ErrEOF;
break;
}
}
return written, err
}
// Copy copies from src to dst until EOF is reached.
// It returns the number of bytes copied and the error, if any.
func Copy(src Reader, dst Writer) (written int64, err os.Error) {
buf := make([]byte, 32*1024);
for {
nr, er := src.Read(buf);
if nr > 0 {
nw, ew := dst.Write(buf[0:nr]);
if nw > 0 {
written += int64(nw);
}
if ew != nil {
err = ew;
break;
}
if nr != nw {
err = os.EIO;
break;
}
}
if er != nil {
err = er;
break;
}
if nr == 0 {
break;
}
}
return written, err
}
// A ByteReader satisfies Reads by consuming data from a slice of bytes.
// Clients can call NewByteReader to create one or wrap pointers
// to their own slices: r := ByteReader{&data}.
type ByteReader struct {
Data *[]byte
}
func (r ByteReader) Read(p []byte) (int, os.Error) {
n := len(p);
b := r.Data;
if n > len(b) {
n = len(b);
}
for i := 0; i < n; i++ {
p[i] = b[i];
}
*b = b[n:len(b)];
return n, nil;
}
// NewByteReader returns a new ByteReader reading from data.
func NewByteReader(data []byte) ByteReader {
return ByteReader{ &data };
}
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