buf.go raw

   1  // Copyright 2015 The Go Authors. All rights reserved.
   2  // Use of this source code is governed by a BSD-style
   3  // license that can be found in the LICENSE file.
   4  
   5  // Package bio implements common I/O abstractions used within the Go toolchain.
   6  package bio
   7  
   8  import (
   9  	"bufio"
  10  	"io"
  11  	"log"
  12  	"os"
  13  )
  14  
  15  // Reader implements a seekable buffered io.Reader.
  16  type Reader struct {
  17  	f *os.File
  18  	*bufio.Reader
  19  }
  20  
  21  // Writer implements a seekable buffered io.Writer.
  22  type Writer struct {
  23  	f *os.File
  24  	*bufio.Writer
  25  }
  26  
  27  // Create creates the file named name and returns a Writer
  28  // for that file.
  29  func Create(name string) (*Writer, error) {
  30  	f, err := os.Create(name)
  31  	if err != nil {
  32  		return nil, err
  33  	}
  34  	return &Writer{f: f, Writer: bufio.NewWriter(f)}, nil
  35  }
  36  
  37  // Open returns a Reader for the file named name.
  38  func Open(name string) (*Reader, error) {
  39  	f, err := os.Open(name)
  40  	if err != nil {
  41  		return nil, err
  42  	}
  43  	return NewReader(f), nil
  44  }
  45  
  46  // NewReader returns a Reader from an open file.
  47  func NewReader(f *os.File) *Reader {
  48  	return &Reader{f: f, Reader: bufio.NewReader(f)}
  49  }
  50  
  51  func (r *Reader) MustSeek(offset int64, whence int) int64 {
  52  	if whence == 1 {
  53  		offset -= int64(r.Buffered())
  54  	}
  55  	off, err := r.f.Seek(offset, whence)
  56  	if err != nil {
  57  		log.Fatalf("seeking in output: %v", err)
  58  	}
  59  	r.Reset(r.f)
  60  	return off
  61  }
  62  
  63  func (w *Writer) MustSeek(offset int64, whence int) int64 {
  64  	if err := w.Flush(); err != nil {
  65  		log.Fatalf("writing output: %v", err)
  66  	}
  67  	off, err := w.f.Seek(offset, whence)
  68  	if err != nil {
  69  		log.Fatalf("seeking in output: %v", err)
  70  	}
  71  	return off
  72  }
  73  
  74  func (r *Reader) Offset() int64 {
  75  	off, err := r.f.Seek(0, 1)
  76  	if err != nil {
  77  		log.Fatalf("seeking in output [0, 1]: %v", err)
  78  	}
  79  	off -= int64(r.Buffered())
  80  	return off
  81  }
  82  
  83  func (w *Writer) Offset() int64 {
  84  	if err := w.Flush(); err != nil {
  85  		log.Fatalf("writing output: %v", err)
  86  	}
  87  	off, err := w.f.Seek(0, 1)
  88  	if err != nil {
  89  		log.Fatalf("seeking in output [0, 1]: %v", err)
  90  	}
  91  	return off
  92  }
  93  
  94  func (r *Reader) Close() error {
  95  	return r.f.Close()
  96  }
  97  
  98  func (w *Writer) Close() error {
  99  	err := w.Flush()
 100  	err1 := w.f.Close()
 101  	if err == nil {
 102  		err = err1
 103  	}
 104  	return err
 105  }
 106  
 107  func (r *Reader) File() *os.File {
 108  	return r.f
 109  }
 110  
 111  func (w *Writer) File() *os.File {
 112  	return w.f
 113  }
 114  
 115  // Slice reads the next length bytes of r into a slice.
 116  //
 117  // This slice may be backed by mmap'ed memory. Currently, this memory
 118  // will never be unmapped. The second result reports whether the
 119  // backing memory is read-only.
 120  func (r *Reader) Slice(length uint64) ([]byte, bool, error) {
 121  	if length == 0 {
 122  		return []byte{}, false, nil
 123  	}
 124  
 125  	data, ok := r.sliceOS(length)
 126  	if ok {
 127  		return data, true, nil
 128  	}
 129  
 130  	data = make([]byte, length)
 131  	_, err := io.ReadFull(r, data)
 132  	if err != nil {
 133  		return nil, false, err
 134  	}
 135  	return data, false, nil
 136  }
 137  
 138  // SliceRO returns a slice containing the next length bytes of r
 139  // backed by a read-only mmap'd data. If the mmap cannot be
 140  // established (limit exceeded, region too small, etc) a nil slice
 141  // will be returned. If mmap succeeds, it will never be unmapped.
 142  func (r *Reader) SliceRO(length uint64) []byte {
 143  	data, ok := r.sliceOS(length)
 144  	if ok {
 145  		return data
 146  	}
 147  	return nil
 148  }
 149