Documentation
¶
Overview ¶
Package flate implements the DEFLATE compressed data format, described in RFC 1951. The gzip and zlib packages implement access to DEFLATE-based file formats.
Index ¶
- Constants
- func NewReader(r io.Reader) io.ReadCloser
- func NewReaderDict(r io.Reader, dict []byte) io.ReadCloser
- func NewStatelessWriter(dst io.Writer) io.WriteCloser
- func StatelessDeflate(out io.Writer, in []byte, eof bool, dict []byte) error
- type CorruptInputError
- type InternalError
- type ReadErrordeprecated
- type Reader
- type Resetter
- type WriteErrordeprecated
- type Writer
Constants ¶
const ( NoCompression = 0 BestSpeed = 1 BestCompression = 9 DefaultCompression = -1 // HuffmanOnly disables Lempel-Ziv match searching and only performs Huffman // entropy encoding. This mode is useful in compressing data that has // already been compressed with an LZ style algorithm (e.g. Snappy or LZ4) // that lacks an entropy encoder. Compression gains are achieved when // certain bytes in the input stream occur more frequently than others. // // Note that HuffmanOnly produces a compressed output that is // RFC 1951 compliant. That is, any valid DEFLATE decompressor will // continue to be able to decompress this output. HuffmanOnly = -2 ConstantCompression = HuffmanOnly // compatibility alias. )
Variables ¶
This section is empty.
Functions ¶
func NewReader ¶
func NewReader(r io.Reader) io.ReadCloser
NewReader returns a new ReadCloser that can be used to read the uncompressed version of r. If r does not also implement io.ByteReader, the decompressor may read more data than necessary from r. It is the caller's responsibility to call Close on the ReadCloser when finished reading.
The ReadCloser returned by NewReader also implements Resetter.
func NewReaderDict ¶
func NewReaderDict(r io.Reader, dict []byte) io.ReadCloser
NewReaderDict is like NewReader but initializes the reader with a preset dictionary. The returned Reader behaves as if the uncompressed data stream started with the given dictionary, which has already been read. NewReaderDict is typically used to read data compressed by NewWriterDict.
The ReadCloser returned by NewReader also implements Resetter.
func NewStatelessWriter ¶ added in v1.9.2
func NewStatelessWriter(dst io.Writer) io.WriteCloser
NewStatelessWriter will do compression but without maintaining any state between Write calls. There will be no memory kept between Write calls, but compression and speed will be suboptimal. Because of this, the size of actual Write calls will affect output size.
func StatelessDeflate ¶ added in v1.9.2
StatelessDeflate allows to compress directly to a Writer without retaining state. When returning everything will be flushed. Up to 8KB of an optional dictionary can be given which is presumed to presumed to precede the block. Longer dictionaries will be truncated and will still produce valid output. Sending nil dictionary is perfectly fine.
Types ¶
type CorruptInputError ¶
type CorruptInputError = flate.CorruptInputError
A CorruptInputError reports the presence of corrupt input at a given offset.
type InternalError ¶
type InternalError string
An InternalError reports an error in the flate code itself.
func (InternalError) Error ¶
func (e InternalError) Error() string
type Reader ¶
type Reader interface {
io.Reader
io.ByteReader
}
The actual read interface needed by NewReader. If the passed in io.Reader does not also have ReadByte, the NewReader will introduce its own buffering.
type Resetter ¶
type Resetter interface {
// Reset discards any buffered data and resets the Resetter as if it was
// newly initialized with the given reader.
Reset(r io.Reader, dict []byte) error
}
Resetter resets a ReadCloser returned by NewReader or NewReaderDict to to switch to a new underlying Reader. This permits reusing a ReadCloser instead of allocating a new one.
type WriteError
deprecated
type WriteError = flate.WriteError
A WriteError reports an error encountered while writing output.
Deprecated: No longer returned.
type Writer ¶
type Writer struct {
// contains filtered or unexported fields
}
A Writer takes data written to it and writes the compressed form of that data to an underlying writer (see NewWriter).
func NewWriter ¶
NewWriter returns a new Writer compressing data at the given level. Following zlib, levels range from 1 (BestSpeed) to 9 (BestCompression); higher levels typically run slower but compress more. Level 0 (NoCompression) does not attempt any compression; it only adds the necessary DEFLATE framing. Level -1 (DefaultCompression) uses the default compression level. Level -2 (ConstantCompression) will use Huffman compression only, giving a very fast compression for all types of input, but sacrificing considerable compression efficiency.
If level is in the range [-2, 9] then the error returned will be nil. Otherwise the error returned will be non-nil.
func NewWriterDict ¶
NewWriterDict is like NewWriter but initializes the new Writer with a preset dictionary. The returned Writer behaves as if the dictionary had been written to it without producing any compressed output. The compressed data written to w can only be decompressed by a Reader initialized with the same dictionary.
func (*Writer) Flush ¶
Flush flushes any pending data to the underlying writer. It is useful mainly in compressed network protocols, to ensure that a remote reader has enough data to reconstruct a packet. Flush does not return until the data has been written. Calling Flush when there is no pending data still causes the Writer to emit a sync marker of at least 4 bytes. If the underlying writer returns an error, Flush returns that error.
In the terminology of the zlib library, Flush is equivalent to Z_SYNC_FLUSH.
func (*Writer) Reset ¶
Reset discards the writer's state and makes it equivalent to the result of NewWriter or NewWriterDict called with dst and w's level and dictionary.
Source Files