forked from SlyMarbo/spdy
/
compression.go
348 lines (303 loc) · 7.62 KB
/
compression.go
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// Copyright 2013 Jamie Hall. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package common
import (
"bytes"
"compress/zlib"
"errors"
"io"
"net/http"
"strings"
"sync"
)
// CompressionLevel can be used to customise the level of
// compression used when sending headers.
var CompressionLevel = zlib.BestCompression
var versionError = errors.New("Version not supported.")
var zlibV2Writers chan *zlib.Writer
var zlibV3Writers chan *zlib.Writer
func init() {
zlibV2Writers = make(chan *zlib.Writer, 5)
zlibV3Writers = make(chan *zlib.Writer, 5)
}
// Decompressor is used to decompress name/value header blocks.
// Decompressors retain their state, so a single Decompressor
// should be used for each direction of a particular connection.
type decompressor struct {
sync.Mutex
in *bytes.Buffer
out io.ReadCloser
version uint16
}
// NewDecompressor is used to create a new decompressor.
// It takes the SPDY version to use.
func NewDecompressor(version uint16) Decompressor {
out := new(decompressor)
out.version = version
return out
}
// Decompress uses zlib decompression to decompress the provided
// data, according to the SPDY specification of the given version.
func (d *decompressor) Decompress(data []byte) (headers http.Header, err error) {
d.Lock()
defer d.Unlock()
// Make sure the buffer is ready.
if d.in == nil {
d.in = bytes.NewBuffer(data)
} else {
d.in.Reset()
d.in.Write(data)
}
// Initialise the decompressor with the appropriate
// dictionary, depending on SPDY version.
if d.out == nil {
switch d.version {
case 2:
d.out, err = zlib.NewReaderDict(d.in, HeaderDictionaryV2)
case 3:
d.out, err = zlib.NewReaderDict(d.in, HeaderDictionaryV3)
default:
err = versionError
}
if err != nil {
return nil, err
}
}
var size int
var bytesToInt func([]byte) int
// SPDY/2 uses 16-bit fixed fields, where SPDY/3 uses 32-bit fields.
switch d.version {
case 2:
size = 2
bytesToInt = func(b []byte) int {
return int(BytesToUint16(b))
}
case 3:
size = 4
bytesToInt = func(b []byte) int {
return int(BytesToUint32(b))
}
default:
return nil, versionError
}
// Read in the number of name/value pairs.
pairs, err := ReadExactly(d.out, size)
if err != nil {
return nil, err
}
numNameValuePairs := bytesToInt(pairs)
headers = make(http.Header)
bounds := MAX_FRAME_SIZE - 12 // Maximum frame size minus maximum non-headers data (SYN_STREAM)
for i := 0; i < numNameValuePairs; i++ {
var nameLength, valueLength int
// Get the name's length.
length, err := ReadExactly(d.out, size)
if err != nil {
return nil, err
}
nameLength = bytesToInt(length)
bounds -= size
if nameLength > bounds {
debug.Printf("Error: Maximum header length is %d. Received name length %d.\n", bounds, nameLength)
return nil, errors.New("Error: Incorrect header name length.")
}
bounds -= nameLength
// Get the name.
name, err := ReadExactly(d.out, nameLength)
if err != nil {
return nil, err
}
// Get the value's length.
length, err = ReadExactly(d.out, size)
if err != nil {
return nil, err
}
valueLength = bytesToInt(length)
bounds -= size
if valueLength > bounds {
debug.Printf("Error: Maximum header length is %d. Received values length %d.\n", bounds, valueLength)
return nil, errors.New("Error: Incorrect header values length.")
}
bounds -= valueLength
// Get the values.
values, err := ReadExactly(d.out, valueLength)
if err != nil {
return nil, err
}
// Split the value on null boundaries.
for _, value := range bytes.Split(values, []byte{'\x00'}) {
headers.Add(string(name), string(value))
}
}
return headers, nil
}
// Compressor is used to compress name/value header blocks.
// Compressors retain their state, so a single Compressor
// should be used for each direction of a particular
// connection.
type compressor struct {
sync.Mutex
buf *bytes.Buffer
w *zlib.Writer
version uint16
}
// NewCompressor is used to create a new compressor.
// It takes the SPDY version to use.
func NewCompressor(version uint16) Compressor {
out := new(compressor)
out.version = version
return out
}
// Compress uses zlib compression to compress the provided
// data, according to the SPDY specification of the given version.
func (c *compressor) Compress(h http.Header) ([]byte, error) {
c.Lock()
defer c.Unlock()
// Ensure the buffer is prepared.
if c.buf == nil {
c.buf = new(bytes.Buffer)
} else {
c.buf.Reset()
}
// Same for the compressor.
if c.w == nil {
var err error
switch c.version {
case 2:
select {
case c.w = <-zlibV2Writers:
c.w.Reset(c.buf)
default:
c.w, err = zlib.NewWriterLevelDict(c.buf, CompressionLevel, HeaderDictionaryV2)
}
case 3:
select {
case c.w = <-zlibV3Writers:
c.w.Reset(c.buf)
default:
c.w, err = zlib.NewWriterLevelDict(c.buf, CompressionLevel, HeaderDictionaryV3)
}
default:
err = versionError
}
if err != nil {
return nil, err
}
}
var size int // Size of length values.
switch c.version {
case 2:
size = 2
case 3:
size = 4
default:
return nil, versionError
}
// Remove invalid headers.
h.Del("Connection")
h.Del("Keep-Alive")
h.Del("Proxy-Connection")
h.Del("Transfer-Encoding")
length := size // The 4-byte or 2-byte number of name/value pairs.
pairs := make(map[string]string) // Used to store the validated, joined headers.
for name, values := range h {
// Ignore invalid names.
if _, ok := pairs[name]; ok { // We've already seen this name.
return nil, errors.New("Error: Duplicate header name discovered.")
}
if name == "" { // Ignore empty names.
continue
}
// Multiple values are separated by a single null byte.
pairs[name] = strings.Join(values, "\x00")
// +size for len(name), +size for len(values).
length += len(name) + size + len(pairs[name]) + size
}
// Uncompressed data.
out := make([]byte, length)
// Current offset into out.
var offset uint32
// Write the number of name/value pairs.
num := uint32(len(pairs))
switch c.version {
case 3:
out[0] = byte(num >> 24)
out[1] = byte(num >> 16)
out[2] = byte(num >> 8)
out[3] = byte(num)
offset = 4
case 2:
out[0] = byte(num >> 8)
out[1] = byte(num)
offset = 2
}
// For each name/value pair...
for name, value := range pairs {
// The length of the name.
nLen := uint32(len(name))
switch c.version {
case 3:
out[offset+0] = byte(nLen >> 24)
out[offset+1] = byte(nLen >> 16)
out[offset+2] = byte(nLen >> 8)
out[offset+3] = byte(nLen)
offset += 4
case 2:
out[offset+0] = byte(nLen >> 8)
out[offset+1] = byte(nLen)
offset += 2
}
// The name itself.
copy(out[offset:], []byte(strings.ToLower(name)))
offset += nLen
// The length of the value.
vLen := uint32(len(value))
switch c.version {
case 3:
out[offset+0] = byte(vLen >> 24)
out[offset+1] = byte(vLen >> 16)
out[offset+2] = byte(vLen >> 8)
out[offset+3] = byte(vLen)
offset += 4
case 2:
out[offset+0] = byte(vLen >> 8)
out[offset+1] = byte(vLen)
offset += 2
}
// The value itself.
copy(out[offset:], []byte(value))
offset += vLen
}
// Compress.
err := WriteExactly(c.w, out)
if err != nil {
return nil, err
}
c.w.Flush()
return c.buf.Bytes(), nil
}
func (c *compressor) Close() error {
if c.w == nil {
return nil
}
var channel chan *zlib.Writer
switch c.version {
case 2:
channel = zlibV2Writers
case 3:
channel = zlibV3Writers
default:
return ErrInvalidVersion
}
select {
case channel <- c.w:
default:
err := c.w.Close()
if err != nil {
return err
}
}
c.w = nil
return nil
}