import "github.com/philhofer/fwd"
The fwd
package provides a buffered reader and writer. Each has methods that help improve the encoding/decoding performance of some binary protocols.
The fwd.Writer
and fwd.Reader
type provide similar functionality to their counterparts in bufio
, plus a few extra utility methods that simplify read-ahead and write-ahead. I wrote this package to improve serialization performance for http://github.com/tinylib/msgp, where it provided about a 2x speedup over bufio
for certain workloads. However, care must be taken to understand the semantics of the extra methods provided by this package, as they allow the user to access and manipulate the buffer memory directly.
The extra methods for fwd.Reader
are Peek
, Skip
and Next
. (*fwd.Reader).Peek
, unlike (*bufio.Reader).Peek
, will re-allocate the read buffer in order to accommodate arbitrarily large read-ahead. (*fwd.Reader).Skip
skips the next n
bytes in the stream, and uses the io.Seeker
interface if the underlying stream implements it. (*fwd.Reader).Next
returns a slice pointing to the next n
bytes in the read buffer (like Peek
), but also increments the read position. This allows users to process streams in arbitrary block sizes without having to manage appropriately-sized slices. Additionally, obviating the need to copy the data from the buffer to another location in memory can improve performance dramatically in CPU-bound applications.
fwd.Writer
only has one extra method, which is (*fwd.Writer).Next
, which returns a slice pointing to the next n
bytes of the writer, and increments the write position by the length of the returned slice. This allows users to write directly to the end of the buffer.
const ( // DefaultReaderSize is the default size of the read buffer DefaultReaderSize = 2048 )
const ( // DefaultWriterSize is the // default write buffer size. DefaultWriterSize = 2048 )
type Reader struct { // contains filtered or unexported fields }
Reader is a buffered look-ahead reader
func NewReader(r io.Reader) *Reader
NewReader returns a new *Reader that reads from ‘r’
func NewReaderSize(r io.Reader, n int) *Reader
NewReaderSize returns a new *Reader that reads from ‘r’ and has a buffer size ‘n’
func (r *Reader) BufferSize() int
BufferSize returns the total size of the buffer
func (r *Reader) Buffered() int
Buffered returns the number of bytes currently in the buffer
func (r *Reader) Next(n int) ([]byte, error)
Next returns the next ‘n’ bytes in the stream. Unlike Peek, Next advances the reader position. The returned bytes point to the same data as the buffer, so the slice is only valid until the next reader method call. An EOF is considered an unexpected error. If an the returned slice is less than the length asked for, an error will be returned, and the reader position will not be incremented.
func (r *Reader) Peek(n int) ([]byte, error)
Peek returns the next ‘n’ buffered bytes, reading from the underlying reader if necessary. It will only return a slice shorter than ‘n’ bytes if it also returns an error. Peek does not advance the reader. EOF errors are not returned as io.ErrUnexpectedEOF.
func (r *Reader) Read(b []byte) (int, error)
Read implements io.Reader
func (r *Reader) ReadByte() (byte, error)
ReadByte implements io.ByteReader
func (r *Reader) ReadFull(b []byte) (int, error)
ReadFull attempts to read len(b) bytes into ‘b’. It returns the number of bytes read into ‘b’, and an error if it does not return len(b). EOF is considered an unexpected error.
func (r *Reader) Reset(rd io.Reader)
Reset resets the underlying reader and the read buffer.
func (r *Reader) Skip(n int) (int, error)
Skip moves the reader forward ‘n’ bytes. Returns the number of bytes skipped and any errors encountered. It is analogous to Seek(n, 1). If the underlying reader implements io.Seeker, then that method will be used to skip forward.
If the reader encounters an EOF before skipping ‘n’ bytes, it returns io.ErrUnexpectedEOF. If the underlying reader implements io.Seeker, then those rules apply instead. (Many implementations will not return io.EOF
until the next call to Read.)
func (r *Reader) WriteTo(w io.Writer) (int64, error)
WriteTo implements io.WriterTo
type Writer struct { // contains filtered or unexported fields }
Writer is a buffered writer
func NewWriter(w io.Writer) *Writer
NewWriter returns a new writer that writes to ‘w’ and has a buffer that is DefaultWriterSize
bytes.
func NewWriterSize(w io.Writer, size int) *Writer
NewWriterSize returns a new writer that writes to ‘w’ and has a buffer that is ‘size’ bytes.
func (w *Writer) BufferSize() int
BufferSize returns the maximum size of the buffer.
func (w *Writer) Buffered() int
Buffered returns the number of buffered bytes in the reader.
func (w *Writer) Flush() error
Flush flushes any buffered bytes to the underlying writer.
func (w *Writer) Next(n int) ([]byte, error)
Next returns the next ‘n’ free bytes in the write buffer, flushing the writer as necessary. Next will return io.ErrShortBuffer
if ‘n’ is greater than the size of the write buffer. Calls to ‘next’ increment the write position by the size of the returned buffer.
func (w *Writer) ReadFrom(r io.Reader) (int64, error)
ReadFrom implements io.ReaderFrom
func (w *Writer) Write(p []byte) (int, error)
Write implements io.Writer
func (w *Writer) WriteByte(b byte) error
WriteByte implements io.ByteWriter
func (w *Writer) WriteString(s string) (int, error)
WriteString is analogous to Write, but it takes a string.
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