/usr/share/gocode/src/github.com/bradfitz/http2/hpack/hpack.go is in golang-github-bradfitz-http2-dev 0.0~git20150509-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 | // Copyright 2014 The Go Authors.
// See https://code.google.com/p/go/source/browse/CONTRIBUTORS
// Licensed under the same terms as Go itself:
// https://code.google.com/p/go/source/browse/LICENSE
// 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
package hpack
import (
"bytes"
"errors"
"fmt"
)
// A DecodingError is something the spec defines as a decoding error.
type DecodingError struct {
Err error
}
func (de DecodingError) Error() string {
return fmt.Sprintf("decoding error: %v", de.Err)
}
// An InvalidIndexError is returned when an encoder references a table
// entry before the static table or after the end of the dynamic table.
type InvalidIndexError int
func (e InvalidIndexError) Error() string {
return fmt.Sprintf("invalid indexed representation index %d", int(e))
}
// A HeaderField is a name-value pair. Both the name and value are
// treated as opaque sequences of octets.
type HeaderField struct {
Name, Value string
// Sensitive means that this header field should never be
// indexed.
Sensitive bool
}
func (hf *HeaderField) size() uint32 {
// http://http2.github.io/http2-spec/compression.html#rfc.section.4.1
// "The size of the dynamic table is the sum of the size of
// its entries. The size of an entry is the sum of its name's
// length in octets (as defined in Section 5.2), its value's
// length in octets (see Section 5.2), plus 32. The size of
// an entry is calculated using the length of the name and
// value without any Huffman encoding applied."
// This can overflow if somebody makes a large HeaderField
// Name and/or Value by hand, but we don't care, because that
// won't happen on the wire because the encoding doesn't allow
// it.
return uint32(len(hf.Name) + len(hf.Value) + 32)
}
// A Decoder is the decoding context for incremental processing of
// header blocks.
type Decoder struct {
dynTab dynamicTable
emit func(f HeaderField)
// buf is the unparsed buffer. It's only written to
// saveBuf if it was truncated in the middle of a header
// block. Because it's usually not owned, we can only
// process it under Write.
buf []byte // usually not owned
saveBuf bytes.Buffer
}
func NewDecoder(maxSize uint32, emitFunc func(f HeaderField)) *Decoder {
d := &Decoder{
emit: emitFunc,
}
d.dynTab.allowedMaxSize = maxSize
d.dynTab.setMaxSize(maxSize)
return d
}
// TODO: add method *Decoder.Reset(maxSize, emitFunc) to let callers re-use Decoders and their
// underlying buffers for garbage reasons.
func (d *Decoder) SetMaxDynamicTableSize(v uint32) {
d.dynTab.setMaxSize(v)
}
// SetAllowedMaxDynamicTableSize sets the upper bound that the encoded
// stream (via dynamic table size updates) may set the maximum size
// to.
func (d *Decoder) SetAllowedMaxDynamicTableSize(v uint32) {
d.dynTab.allowedMaxSize = v
}
type dynamicTable struct {
// ents is the FIFO described at
// http://http2.github.io/http2-spec/compression.html#rfc.section.2.3.2
// The newest (low index) is append at the end, and items are
// evicted from the front.
ents []HeaderField
size uint32
maxSize uint32 // current maxSize
allowedMaxSize uint32 // maxSize may go up to this, inclusive
}
func (dt *dynamicTable) setMaxSize(v uint32) {
dt.maxSize = v
dt.evict()
}
// TODO: change dynamicTable to be a struct with a slice and a size int field,
// per http://http2.github.io/http2-spec/compression.html#rfc.section.4.1:
//
//
// Then make add increment the size. maybe the max size should move from Decoder to
// dynamicTable and add should return an ok bool if there was enough space.
//
// Later we'll need a remove operation on dynamicTable.
func (dt *dynamicTable) add(f HeaderField) {
dt.ents = append(dt.ents, f)
dt.size += f.size()
dt.evict()
}
// If we're too big, evict old stuff (front of the slice)
func (dt *dynamicTable) evict() {
base := dt.ents // keep base pointer of slice
for dt.size > dt.maxSize {
dt.size -= dt.ents[0].size()
dt.ents = dt.ents[1:]
}
// Shift slice contents down if we evicted things.
if len(dt.ents) != len(base) {
copy(base, dt.ents)
dt.ents = base[:len(dt.ents)]
}
}
// constantTimeStringCompare compares string a and b in a constant
// time manner.
func constantTimeStringCompare(a, b string) bool {
if len(a) != len(b) {
return false
}
c := byte(0)
for i := 0; i < len(a); i++ {
c |= a[i] ^ b[i]
}
return c == 0
}
// Search searches f in the table. The return value i is 0 if there is
// no name match. If there is name match or name/value match, i is the
// index of that entry (1-based). If both name and value match,
// nameValueMatch becomes true.
func (dt *dynamicTable) search(f HeaderField) (i uint64, nameValueMatch bool) {
l := len(dt.ents)
for j := l - 1; j >= 0; j-- {
ent := dt.ents[j]
if !constantTimeStringCompare(ent.Name, f.Name) {
continue
}
if i == 0 {
i = uint64(l - j)
}
if f.Sensitive {
continue
}
if !constantTimeStringCompare(ent.Value, f.Value) {
continue
}
i = uint64(l - j)
nameValueMatch = true
return
}
return
}
func (d *Decoder) maxTableIndex() int {
return len(d.dynTab.ents) + len(staticTable)
}
func (d *Decoder) at(i uint64) (hf HeaderField, ok bool) {
if i < 1 {
return
}
if i > uint64(d.maxTableIndex()) {
return
}
if i <= uint64(len(staticTable)) {
return staticTable[i-1], true
}
dents := d.dynTab.ents
return dents[len(dents)-(int(i)-len(staticTable))], true
}
// Decode decodes an entire block.
//
// TODO: remove this method and make it incremental later? This is
// easier for debugging now.
func (d *Decoder) DecodeFull(p []byte) ([]HeaderField, error) {
var hf []HeaderField
saveFunc := d.emit
defer func() { d.emit = saveFunc }()
d.emit = func(f HeaderField) { hf = append(hf, f) }
if _, err := d.Write(p); err != nil {
return nil, err
}
if err := d.Close(); err != nil {
return nil, err
}
return hf, nil
}
func (d *Decoder) Close() error {
if d.saveBuf.Len() > 0 {
d.saveBuf.Reset()
return DecodingError{errors.New("truncated headers")}
}
return nil
}
func (d *Decoder) Write(p []byte) (n int, err error) {
if len(p) == 0 {
// Prevent state machine CPU attacks (making us redo
// work up to the point of finding out we don't have
// enough data)
return
}
// Only copy the data if we have to. Optimistically assume
// that p will contain a complete header block.
if d.saveBuf.Len() == 0 {
d.buf = p
} else {
d.saveBuf.Write(p)
d.buf = d.saveBuf.Bytes()
d.saveBuf.Reset()
}
for len(d.buf) > 0 {
err = d.parseHeaderFieldRepr()
if err != nil {
if err == errNeedMore {
err = nil
d.saveBuf.Write(d.buf)
}
break
}
}
return len(p), err
}
// errNeedMore is an internal sentinel error value that means the
// buffer is truncated and we need to read more data before we can
// continue parsing.
var errNeedMore = errors.New("need more data")
type indexType int
const (
indexedTrue indexType = iota
indexedFalse
indexedNever
)
func (v indexType) indexed() bool { return v == indexedTrue }
func (v indexType) sensitive() bool { return v == indexedNever }
// returns errNeedMore if there isn't enough data available.
// any other error is fatal.
// consumes d.buf iff it returns nil.
// precondition: must be called with len(d.buf) > 0
func (d *Decoder) parseHeaderFieldRepr() error {
b := d.buf[0]
switch {
case b&128 != 0:
// Indexed representation.
// High bit set?
// http://http2.github.io/http2-spec/compression.html#rfc.section.6.1
return d.parseFieldIndexed()
case b&192 == 64:
// 6.2.1 Literal Header Field with Incremental Indexing
// 0b10xxxxxx: top two bits are 10
// http://http2.github.io/http2-spec/compression.html#rfc.section.6.2.1
return d.parseFieldLiteral(6, indexedTrue)
case b&240 == 0:
// 6.2.2 Literal Header Field without Indexing
// 0b0000xxxx: top four bits are 0000
// http://http2.github.io/http2-spec/compression.html#rfc.section.6.2.2
return d.parseFieldLiteral(4, indexedFalse)
case b&240 == 16:
// 6.2.3 Literal Header Field never Indexed
// 0b0001xxxx: top four bits are 0001
// http://http2.github.io/http2-spec/compression.html#rfc.section.6.2.3
return d.parseFieldLiteral(4, indexedNever)
case b&224 == 32:
// 6.3 Dynamic Table Size Update
// Top three bits are '001'.
// http://http2.github.io/http2-spec/compression.html#rfc.section.6.3
return d.parseDynamicTableSizeUpdate()
}
return DecodingError{errors.New("invalid encoding")}
}
// (same invariants and behavior as parseHeaderFieldRepr)
func (d *Decoder) parseFieldIndexed() error {
buf := d.buf
idx, buf, err := readVarInt(7, buf)
if err != nil {
return err
}
hf, ok := d.at(idx)
if !ok {
return DecodingError{InvalidIndexError(idx)}
}
d.emit(HeaderField{Name: hf.Name, Value: hf.Value})
d.buf = buf
return nil
}
// (same invariants and behavior as parseHeaderFieldRepr)
func (d *Decoder) parseFieldLiteral(n uint8, it indexType) error {
buf := d.buf
nameIdx, buf, err := readVarInt(n, buf)
if err != nil {
return err
}
var hf HeaderField
if nameIdx > 0 {
ihf, ok := d.at(nameIdx)
if !ok {
return DecodingError{InvalidIndexError(nameIdx)}
}
hf.Name = ihf.Name
} else {
hf.Name, buf, err = readString(buf)
if err != nil {
return err
}
}
hf.Value, buf, err = readString(buf)
if err != nil {
return err
}
d.buf = buf
if it.indexed() {
d.dynTab.add(hf)
}
hf.Sensitive = it.sensitive()
d.emit(hf)
return nil
}
// (same invariants and behavior as parseHeaderFieldRepr)
func (d *Decoder) parseDynamicTableSizeUpdate() error {
buf := d.buf
size, buf, err := readVarInt(5, buf)
if err != nil {
return err
}
if size > uint64(d.dynTab.allowedMaxSize) {
return DecodingError{errors.New("dynamic table size update too large")}
}
d.dynTab.setMaxSize(uint32(size))
d.buf = buf
return nil
}
var errVarintOverflow = DecodingError{errors.New("varint integer overflow")}
// readVarInt reads an unsigned variable length integer off the
// beginning of p. n is the parameter as described in
// http://http2.github.io/http2-spec/compression.html#rfc.section.5.1.
//
// n must always be between 1 and 8.
//
// The returned remain buffer is either a smaller suffix of p, or err != nil.
// The error is errNeedMore if p doesn't contain a complete integer.
func readVarInt(n byte, p []byte) (i uint64, remain []byte, err error) {
if n < 1 || n > 8 {
panic("bad n")
}
if len(p) == 0 {
return 0, p, errNeedMore
}
i = uint64(p[0])
if n < 8 {
i &= (1 << uint64(n)) - 1
}
if i < (1<<uint64(n))-1 {
return i, p[1:], nil
}
origP := p
p = p[1:]
var m uint64
for len(p) > 0 {
b := p[0]
p = p[1:]
i += uint64(b&127) << m
if b&128 == 0 {
return i, p, nil
}
m += 7
if m >= 63 { // TODO: proper overflow check. making this up.
return 0, origP, errVarintOverflow
}
}
return 0, origP, errNeedMore
}
func readString(p []byte) (s string, remain []byte, err error) {
if len(p) == 0 {
return "", p, errNeedMore
}
isHuff := p[0]&128 != 0
strLen, p, err := readVarInt(7, p)
if err != nil {
return "", p, err
}
if uint64(len(p)) < strLen {
return "", p, errNeedMore
}
if !isHuff {
return string(p[:strLen]), p[strLen:], nil
}
// TODO: optimize this garbage:
var buf bytes.Buffer
if _, err := HuffmanDecode(&buf, p[:strLen]); err != nil {
return "", nil, err
}
return buf.String(), p[strLen:], nil
}
|