6.6 KiB
fwd
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.
Constants
const (
// DefaultReaderSize is the default size of the read buffer
DefaultReaderSize = 2048
)const (
// DefaultWriterSize is the
// default write buffer size.
DefaultWriterSize = 2048
)type Reader
type Reader struct {
// contains filtered or unexported fields
}Reader is a buffered look-ahead reader
func NewReader
func NewReader(r io.Reader) *ReaderNewReader returns a new *Reader that reads from ‘r’
func NewReaderSize
func NewReaderSize(r io.Reader, n int) *ReaderNewReaderSize returns a new *Reader that reads from ‘r’ and has a buffer size ‘n’
func (*Reader) BufferSize
func (r *Reader) BufferSize() intBufferSize returns the total size of the buffer
func (*Reader) Buffered
func (r *Reader) Buffered() intBuffered returns the number of bytes currently in the buffer
func (*Reader) Next
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 (*Reader) Peek
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 (*Reader) Read
func (r *Reader) Read(b []byte) (int, error)Read implements io.Reader
func (*Reader) ReadByte
func (r *Reader) ReadByte() (byte, error)ReadByte implements io.ByteReader
func (*Reader) ReadFull
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 (*Reader) Reset
func (r *Reader) Reset(rd io.Reader)Reset resets the underlying reader and the read buffer.
func (*Reader) Skip
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 (*Reader) WriteTo
func (r *Reader) WriteTo(w io.Writer) (int64, error)WriteTo implements io.WriterTo
type Writer
type Writer struct {
// contains filtered or unexported fields
}Writer is a buffered writer
func NewWriter
func NewWriter(w io.Writer) *WriterNewWriter returns a new writer that writes to ‘w’ and has a buffer
that is DefaultWriterSize bytes.
func NewWriterSize
func NewWriterSize(w io.Writer, size int) *WriterNewWriterSize returns a new writer that writes to ‘w’ and has a buffer that is ‘size’ bytes.
func (*Writer) BufferSize
func (w *Writer) BufferSize() intBufferSize returns the maximum size of the buffer.
func (*Writer) Buffered
func (w *Writer) Buffered() intBuffered returns the number of buffered bytes in the reader.
func (*Writer) Flush
func (w *Writer) Flush() errorFlush flushes any buffered bytes to the underlying writer.
func (*Writer) Next
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 (*Writer) ReadFrom
func (w *Writer) ReadFrom(r io.Reader) (int64, error)ReadFrom implements io.ReaderFrom
func (*Writer) Write
func (w *Writer) Write(p []byte) (int, error)Write implements io.Writer
func (*Writer) WriteByte
func (w *Writer) WriteByte(b byte) errorWriteByte implements io.ByteWriter
func (*Writer) WriteString
func (w *Writer) WriteString(s string) (int, error)WriteString is analogous to Write, but it takes a string.
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