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149 lines
3.1 KiB
Go
149 lines
3.1 KiB
Go
// Copyright 2015 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package bio implements common I/O abstractions used within the Go toolchain.
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package bio
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import (
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"bufio"
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"io"
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"log"
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"os"
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)
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// Reader implements a seekable buffered io.Reader.
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type Reader struct {
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f *os.File
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*bufio.Reader
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}
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// Writer implements a seekable buffered io.Writer.
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type Writer struct {
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f *os.File
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*bufio.Writer
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}
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// Create creates the file named name and returns a Writer
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// for that file.
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func Create(name string) (*Writer, error) {
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f, err := os.Create(name)
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if err != nil {
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return nil, err
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}
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return &Writer{f: f, Writer: bufio.NewWriter(f)}, nil
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}
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// Open returns a Reader for the file named name.
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func Open(name string) (*Reader, error) {
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f, err := os.Open(name)
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if err != nil {
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return nil, err
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}
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return NewReader(f), nil
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}
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// NewReader returns a Reader from an open file.
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func NewReader(f *os.File) *Reader {
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return &Reader{f: f, Reader: bufio.NewReader(f)}
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}
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func (r *Reader) MustSeek(offset int64, whence int) int64 {
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if whence == 1 {
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offset -= int64(r.Buffered())
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}
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off, err := r.f.Seek(offset, whence)
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if err != nil {
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log.Fatalf("seeking in output: %v", err)
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}
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r.Reset(r.f)
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return off
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}
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func (w *Writer) MustSeek(offset int64, whence int) int64 {
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if err := w.Flush(); err != nil {
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log.Fatalf("writing output: %v", err)
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}
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off, err := w.f.Seek(offset, whence)
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if err != nil {
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log.Fatalf("seeking in output: %v", err)
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}
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return off
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}
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func (r *Reader) Offset() int64 {
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off, err := r.f.Seek(0, 1)
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if err != nil {
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log.Fatalf("seeking in output [0, 1]: %v", err)
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}
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off -= int64(r.Buffered())
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return off
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}
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func (w *Writer) Offset() int64 {
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if err := w.Flush(); err != nil {
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log.Fatalf("writing output: %v", err)
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}
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off, err := w.f.Seek(0, 1)
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if err != nil {
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log.Fatalf("seeking in output [0, 1]: %v", err)
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}
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return off
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}
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func (r *Reader) Close() error {
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return r.f.Close()
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}
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func (w *Writer) Close() error {
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err := w.Flush()
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err1 := w.f.Close()
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if err == nil {
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err = err1
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}
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return err
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}
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func (r *Reader) File() *os.File {
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return r.f
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}
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func (w *Writer) File() *os.File {
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return w.f
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}
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// Slice reads the next length bytes of r into a slice.
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//
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// This slice may be backed by mmap'ed memory. Currently, this memory
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// will never be unmapped. The second result reports whether the
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// backing memory is read-only.
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func (r *Reader) Slice(length uint64) ([]byte, bool, error) {
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if length == 0 {
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return []byte{}, false, nil
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}
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data, ok := r.sliceOS(length)
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if ok {
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return data, true, nil
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}
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data = make([]byte, length)
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_, err := io.ReadFull(r, data)
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if err != nil {
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return nil, false, err
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}
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return data, false, nil
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}
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// SliceRO returns a slice containing the next length bytes of r
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// backed by a read-only mmap'd data. If the mmap cannot be
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// established (limit exceeded, region too small, etc) a nil slice
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// will be returned. If mmap succeeds, it will never be unmapped.
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func (r *Reader) SliceRO(length uint64) []byte {
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data, ok := r.sliceOS(length)
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if ok {
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return data
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}
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return nil
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}
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