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Published: Nov 13, 2017 License: Apache-2.0, BSD-3-Clause Imports: 5 Imported by: 0



Package hpack implements HPACK, a compression format for efficiently representing HTTP header fields in the context of HTTP/2.

See http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-09



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var ErrInvalidHuffman = errors.New("hpack: invalid Huffman-encoded data")

ErrInvalidHuffman is returned for errors found decoding Huffman-encoded strings.

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var ErrStringLength = errors.New("hpack: string too long")

ErrStringLength is returned by Decoder.Write when the max string length (as configured by Decoder.SetMaxStringLength) would be violated.


func AppendHuffmanString

func AppendHuffmanString(dst []byte, s string) []byte

AppendHuffmanString appends s, as encoded in Huffman codes, to dst and returns the extended buffer.

func HuffmanDecode

func HuffmanDecode(w io.Writer, v []byte) (int, error)

HuffmanDecode decodes the string in v and writes the expanded result to w, returning the number of bytes written to w and the Write call's return value. At most one Write call is made.

func HuffmanDecodeToString

func HuffmanDecodeToString(v []byte) (string, error)

HuffmanDecodeToString decodes the string in v.

func HuffmanEncodeLength

func HuffmanEncodeLength(s string) uint64

HuffmanEncodeLength returns the number of bytes required to encode s in Huffman codes. The result is round up to byte boundary.


type Decoder

type Decoder struct {
	// contains filtered or unexported fields

A Decoder is the decoding context for incremental processing of header blocks.

func NewDecoder

func NewDecoder(maxDynamicTableSize uint32, emitFunc func(f HeaderField)) *Decoder

NewDecoder returns a new decoder with the provided maximum dynamic table size. The emitFunc will be called for each valid field parsed, in the same goroutine as calls to Write, before Write returns.

func (*Decoder) Close

func (d *Decoder) Close() error

func (*Decoder) DecodeFull

func (d *Decoder) DecodeFull(p []byte) ([]HeaderField, error)

Decode decodes an entire block.

TODO: remove this method and make it incremental later? This is easier for debugging now.

func (*Decoder) EmitEnabled

func (d *Decoder) EmitEnabled() bool

EmitEnabled reports whether calls to the emitFunc provided to NewDecoder are currently enabled. The default is true.

func (*Decoder) SetAllowedMaxDynamicTableSize

func (d *Decoder) SetAllowedMaxDynamicTableSize(v uint32)

SetAllowedMaxDynamicTableSize sets the upper bound that the encoded stream (via dynamic table size updates) may set the maximum size to.

func (*Decoder) SetEmitEnabled

func (d *Decoder) SetEmitEnabled(v bool)

SetEmitEnabled controls whether the emitFunc provided to NewDecoder should be called. The default is true.

This facility exists to let servers enforce MAX_HEADER_LIST_SIZE while still decoding and keeping in-sync with decoder state, but without doing unnecessary decompression or generating unnecessary garbage for header fields past the limit.

func (*Decoder) SetEmitFunc

func (d *Decoder) SetEmitFunc(emitFunc func(f HeaderField))

SetEmitFunc changes the callback used when new header fields are decoded. It must be non-nil. It does not affect EmitEnabled.

func (*Decoder) SetMaxDynamicTableSize

func (d *Decoder) SetMaxDynamicTableSize(v uint32)

func (*Decoder) SetMaxStringLength

func (d *Decoder) SetMaxStringLength(n int)

SetMaxStringLength sets the maximum size of a HeaderField name or value string. If a string exceeds this length (even after any decompression), Write will return ErrStringLength. A value of 0 means unlimited and is the default from NewDecoder.

func (*Decoder) Write

func (d *Decoder) Write(p []byte) (n int, err error)

type DecodingError

type DecodingError struct {
	Err error

A DecodingError is something the spec defines as a decoding error.

func (DecodingError) Error

func (de DecodingError) Error() string

type Encoder

type Encoder struct {
	// contains filtered or unexported fields

func NewEncoder

func NewEncoder(w io.Writer) *Encoder

NewEncoder returns a new Encoder which performs HPACK encoding. An encoded data is written to w.

func (*Encoder) SetMaxDynamicTableSize

func (e *Encoder) SetMaxDynamicTableSize(v uint32)

SetMaxDynamicTableSize changes the dynamic header table size to v. The actual size is bounded by the value passed to SetMaxDynamicTableSizeLimit.

func (*Encoder) SetMaxDynamicTableSizeLimit

func (e *Encoder) SetMaxDynamicTableSizeLimit(v uint32)

SetMaxDynamicTableSizeLimit changes the maximum value that can be specified in SetMaxDynamicTableSize to v. By default, it is set to 4096, which is the same size of the default dynamic header table size described in HPACK specification. If the current maximum dynamic header table size is strictly greater than v, "Header Table Size Update" will be done in the next WriteField call and the maximum dynamic header table size is truncated to v.

func (*Encoder) WriteField

func (e *Encoder) WriteField(f HeaderField) error

WriteField encodes f into a single Write to e's underlying Writer. This function may also produce bytes for "Header Table Size Update" if necessary. If produced, it is done before encoding f.

type HeaderField

type HeaderField struct {
	Name, Value string

	// Sensitive means that this header field should never be
	// indexed.
	Sensitive bool

A HeaderField is a name-value pair. Both the name and value are treated as opaque sequences of octets.

func (HeaderField) IsPseudo

func (hf HeaderField) IsPseudo() bool

IsPseudo reports whether the header field is an http2 pseudo header. That is, it reports whether it starts with a colon. It is not otherwise guaranteed to be a valid pseudo header field, though.

func (HeaderField) Size

func (hf HeaderField) Size() uint32

Size returns the size of an entry per RFC 7541 section 4.1.

func (HeaderField) String

func (hf HeaderField) String() string

type InvalidIndexError

type InvalidIndexError int

An InvalidIndexError is returned when an encoder references a table entry before the static table or after the end of the dynamic table.

func (InvalidIndexError) Error

func (e InvalidIndexError) Error() string

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