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brotli/decode.go

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package brotli
/* Copyright 2013 Google Inc. All Rights Reserved.
Distributed under MIT license.
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/
/* Copyright 2013 Google Inc. All Rights Reserved.
Distributed under MIT license.
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/
/**
* @file
* API for Brotli decompression.
*/
/**
* Result type for ::BrotliDecoderDecompress and
* ::BrotliDecoderDecompressStream functions.
*/
const (
decoderResultError = 0
decoderResultSuccess = 1
decoderResultNeedsMoreInput = 2
decoderResultNeedsMoreOutput = 3
)
/**
* Template that evaluates items of ::BrotliDecoderErrorCode.
*
* Example: @code {.cpp}
* // Log Brotli error code.
* switch (brotliDecoderErrorCode) {
* #define CASE_(PREFIX, NAME, CODE) \
* case BROTLI_DECODER ## PREFIX ## NAME: \
* LOG(INFO) << "error code:" << #NAME; \
* break;
* #define NEWLINE_
* BROTLI_DECODER_ERROR_CODES_LIST(CASE_, NEWLINE_)
* #undef CASE_
* #undef NEWLINE_
* default: LOG(FATAL) << "unknown brotli error code";
* }
* @endcode
*/
/**
* Error code for detailed logging / production debugging.
*
* See ::BrotliDecoderGetErrorCode and ::BROTLI_LAST_ERROR_CODE.
*/
const (
decoderNoError = 0
decoderSuccess = 1
decoderNeedsMoreInput = 2
decoderNeedsMoreOutput = 3
decoderErrorFormatExuberantNibble = -1
decoderErrorFormatReserved = -2
decoderErrorFormatExuberantMetaNibble = -3
decoderErrorFormatSimpleHuffmanAlphabet = -4
decoderErrorFormatSimpleHuffmanSame = -5
decoderErrorFormatClSpace = -6
decoderErrorFormatHuffmanSpace = -7
decoderErrorFormatContextMapRepeat = -8
decoderErrorFormatBlockLength1 = -9
decoderErrorFormatBlockLength2 = -10
decoderErrorFormatTransform = -11
decoderErrorFormatDictionary = -12
decoderErrorFormatWindowBits = -13
decoderErrorFormatPadding1 = -14
decoderErrorFormatPadding2 = -15
decoderErrorFormatDistance = -16
decoderErrorDictionaryNotSet = -19
decoderErrorInvalidArguments = -20
decoderErrorAllocContextModes = -21
decoderErrorAllocTreeGroups = -22
decoderErrorAllocContextMap = -25
decoderErrorAllocRingBuffer1 = -26
decoderErrorAllocRingBuffer2 = -27
decoderErrorAllocBlockTypeTrees = -30
decoderErrorUnreachable = -31
)
/**
* The value of the last error code, negative integer.
*
* All other error code values are in the range from ::lastErrorCode
* to @c -1. There are also 4 other possible non-error codes @c 0 .. @c 3 in
* ::BrotliDecoderErrorCode enumeration.
*/
const lastErrorCode = decoderErrorUnreachable
/** Options to be used with ::BrotliDecoderSetParameter. */
const (
decoderParamDisableRingBufferReallocation = 0
decoderParamLargeWindow = 1
)
const huffmanTableBits = 8
const huffmanTableMask = 0xFF
/* We need the slack region for the following reasons:
- doing up to two 16-byte copies for fast backward copying
- inserting transformed dictionary word (5 prefix + 24 base + 8 suffix) */
var kRingBufferWriteAheadSlack uint32 = 42
var kCodeLengthCodeOrder = [codeLengthCodes]byte{1, 2, 3, 4, 0, 5, 17, 6, 16, 7, 8, 9, 10, 11, 12, 13, 14, 15}
/* Static prefix code for the complex code length code lengths. */
var kCodeLengthPrefixLength = [16]byte{2, 2, 2, 3, 2, 2, 2, 4, 2, 2, 2, 3, 2, 2, 2, 4}
var kCodeLengthPrefixValue = [16]byte{0, 4, 3, 2, 0, 4, 3, 1, 0, 4, 3, 2, 0, 4, 3, 5}
func decoderSetParameter(state *Reader, p int, value uint32) bool {
if state.state != BROTLI_STATE_UNINITED {
return false
}
switch p {
case decoderParamDisableRingBufferReallocation:
if !(value == 0) {
state.canny_ringbuffer_allocation = 0
} else {
state.canny_ringbuffer_allocation = 1
}
return true
case decoderParamLargeWindow:
state.large_window = (!(value == 0))
return true
default:
return false
}
}
/* Saves error code and converts it to BrotliDecoderResult. */
func saveErrorCode(s *Reader, e int) int {
s.error_code = int(e)
switch e {
case decoderSuccess:
return decoderResultSuccess
case decoderNeedsMoreInput:
return decoderResultNeedsMoreInput
case decoderNeedsMoreOutput:
return decoderResultNeedsMoreOutput
default:
return decoderResultError
}
}
/* Decodes WBITS by reading 1 - 7 bits, or 0x11 for "Large Window Brotli".
Precondition: bit-reader accumulator has at least 8 bits. */
func decodeWindowBits(s *Reader, br *bitReader) int {
var n uint32
var large_window bool = s.large_window
s.large_window = false
takeBits(br, 1, &n)
if n == 0 {
s.window_bits = 16
return decoderSuccess
}
takeBits(br, 3, &n)
if n != 0 {
s.window_bits = 17 + n
return decoderSuccess
}
takeBits(br, 3, &n)
if n == 1 {
if large_window {
takeBits(br, 1, &n)
if n == 1 {
return decoderErrorFormatWindowBits
}
s.large_window = true
return decoderSuccess
} else {
return decoderErrorFormatWindowBits
}
}
if n != 0 {
s.window_bits = 8 + n
return decoderSuccess
}
s.window_bits = 17
return decoderSuccess
}
/* Decodes a number in the range [0..255], by reading 1 - 11 bits. */
func decodeVarLenUint8(s *Reader, br *bitReader, value *uint32) int {
var bits uint32
switch s.substate_decode_uint8 {
case BROTLI_STATE_DECODE_UINT8_NONE:
if !safeReadBits(br, 1, &bits) {
return decoderNeedsMoreInput
}
if bits == 0 {
*value = 0
return decoderSuccess
}
fallthrough
/* Fall through. */
case BROTLI_STATE_DECODE_UINT8_SHORT:
if !safeReadBits(br, 3, &bits) {
s.substate_decode_uint8 = BROTLI_STATE_DECODE_UINT8_SHORT
return decoderNeedsMoreInput
}
if bits == 0 {
*value = 1
s.substate_decode_uint8 = BROTLI_STATE_DECODE_UINT8_NONE
return decoderSuccess
}
/* Use output value as a temporary storage. It MUST be persisted. */
*value = bits
fallthrough
/* Fall through. */
case BROTLI_STATE_DECODE_UINT8_LONG:
if !safeReadBits(br, *value, &bits) {
s.substate_decode_uint8 = BROTLI_STATE_DECODE_UINT8_LONG
return decoderNeedsMoreInput
}
*value = (1 << *value) + bits
s.substate_decode_uint8 = BROTLI_STATE_DECODE_UINT8_NONE
return decoderSuccess
default:
return decoderErrorUnreachable
}
}
/* Decodes a metablock length and flags by reading 2 - 31 bits. */
func decodeMetaBlockLength(s *Reader, br *bitReader) int {
var bits uint32
var i int
for {
switch s.substate_metablock_header {
case BROTLI_STATE_METABLOCK_HEADER_NONE:
if !safeReadBits(br, 1, &bits) {
return decoderNeedsMoreInput
}
if bits != 0 {
s.is_last_metablock = 1
} else {
s.is_last_metablock = 0
}
s.meta_block_remaining_len = 0
s.is_uncompressed = 0
s.is_metadata = 0
if s.is_last_metablock == 0 {
s.substate_metablock_header = BROTLI_STATE_METABLOCK_HEADER_NIBBLES
break
}
s.substate_metablock_header = BROTLI_STATE_METABLOCK_HEADER_EMPTY
fallthrough
/* Fall through. */
case BROTLI_STATE_METABLOCK_HEADER_EMPTY:
if !safeReadBits(br, 1, &bits) {
return decoderNeedsMoreInput
}
if bits != 0 {
s.substate_metablock_header = BROTLI_STATE_METABLOCK_HEADER_NONE
return decoderSuccess
}
s.substate_metablock_header = BROTLI_STATE_METABLOCK_HEADER_NIBBLES
fallthrough
/* Fall through. */
case BROTLI_STATE_METABLOCK_HEADER_NIBBLES:
if !safeReadBits(br, 2, &bits) {
return decoderNeedsMoreInput
}
s.size_nibbles = uint(byte(bits + 4))
s.loop_counter = 0
if bits == 3 {
s.is_metadata = 1
s.substate_metablock_header = BROTLI_STATE_METABLOCK_HEADER_RESERVED
break
}
s.substate_metablock_header = BROTLI_STATE_METABLOCK_HEADER_SIZE
fallthrough
/* Fall through. */
case BROTLI_STATE_METABLOCK_HEADER_SIZE:
i = s.loop_counter
for ; i < int(s.size_nibbles); i++ {
if !safeReadBits(br, 4, &bits) {
s.loop_counter = i
return decoderNeedsMoreInput
}
if uint(i+1) == s.size_nibbles && s.size_nibbles > 4 && bits == 0 {
return decoderErrorFormatExuberantNibble
}
s.meta_block_remaining_len |= int(bits << uint(i*4))
}
s.substate_metablock_header = BROTLI_STATE_METABLOCK_HEADER_UNCOMPRESSED
fallthrough
/* Fall through. */
case BROTLI_STATE_METABLOCK_HEADER_UNCOMPRESSED:
if s.is_last_metablock == 0 {
if !safeReadBits(br, 1, &bits) {
return decoderNeedsMoreInput
}
if bits != 0 {
s.is_uncompressed = 1
} else {
s.is_uncompressed = 0
}
}
s.meta_block_remaining_len++
s.substate_metablock_header = BROTLI_STATE_METABLOCK_HEADER_NONE
return decoderSuccess
case BROTLI_STATE_METABLOCK_HEADER_RESERVED:
if !safeReadBits(br, 1, &bits) {
return decoderNeedsMoreInput
}
if bits != 0 {
return decoderErrorFormatReserved
}
s.substate_metablock_header = BROTLI_STATE_METABLOCK_HEADER_BYTES
fallthrough
/* Fall through. */
case BROTLI_STATE_METABLOCK_HEADER_BYTES:
if !safeReadBits(br, 2, &bits) {
return decoderNeedsMoreInput
}
if bits == 0 {
s.substate_metablock_header = BROTLI_STATE_METABLOCK_HEADER_NONE
return decoderSuccess
}
s.size_nibbles = uint(byte(bits))
s.substate_metablock_header = BROTLI_STATE_METABLOCK_HEADER_METADATA
fallthrough
/* Fall through. */
case BROTLI_STATE_METABLOCK_HEADER_METADATA:
i = s.loop_counter
for ; i < int(s.size_nibbles); i++ {
if !safeReadBits(br, 8, &bits) {
s.loop_counter = i
return decoderNeedsMoreInput
}
if uint(i+1) == s.size_nibbles && s.size_nibbles > 1 && bits == 0 {
return decoderErrorFormatExuberantMetaNibble
}
s.meta_block_remaining_len |= int(bits << uint(i*8))
}
s.meta_block_remaining_len++
s.substate_metablock_header = BROTLI_STATE_METABLOCK_HEADER_NONE
return decoderSuccess
default:
return decoderErrorUnreachable
}
}
}
/* Decodes the Huffman code.
This method doesn't read data from the bit reader, BUT drops the amount of
bits that correspond to the decoded symbol.
bits MUST contain at least 15 (BROTLI_HUFFMAN_MAX_CODE_LENGTH) valid bits. */
func decodeSymbol(bits uint32, table []huffmanCode, br *bitReader) uint32 {
table = table[bits&huffmanTableMask:]
if table[0].bits > huffmanTableBits {
var nbits uint32 = uint32(table[0].bits) - huffmanTableBits
dropBits(br, huffmanTableBits)
table = table[uint32(table[0].value)+((bits>>huffmanTableBits)&bitMask(nbits)):]
}
dropBits(br, uint32(table[0].bits))
return uint32(table[0].value)
}
/* Reads and decodes the next Huffman code from bit-stream.
This method peeks 16 bits of input and drops 0 - 15 of them. */
func readSymbol(table []huffmanCode, br *bitReader) uint32 {
return decodeSymbol(get16BitsUnmasked(br), table, br)
}
/* Same as DecodeSymbol, but it is known that there is less than 15 bits of
input are currently available. */
func safeDecodeSymbol(table []huffmanCode, br *bitReader, result *uint32) bool {
var val uint32
var available_bits uint32 = getAvailableBits(br)
if available_bits == 0 {
if table[0].bits == 0 {
*result = uint32(table[0].value)
return true
}
return false /* No valid bits at all. */
}
val = uint32(getBitsUnmasked(br))
table = table[val&huffmanTableMask:]
if table[0].bits <= huffmanTableBits {
if uint32(table[0].bits) <= available_bits {
dropBits(br, uint32(table[0].bits))
*result = uint32(table[0].value)
return true
} else {
return false /* Not enough bits for the first level. */
}
}
if available_bits <= huffmanTableBits {
return false /* Not enough bits to move to the second level. */
}
/* Speculatively drop HUFFMAN_TABLE_BITS. */
val = (val & bitMask(uint32(table[0].bits))) >> huffmanTableBits
available_bits -= huffmanTableBits
table = table[uint32(table[0].value)+val:]
if available_bits < uint32(table[0].bits) {
return false /* Not enough bits for the second level. */
}
dropBits(br, huffmanTableBits+uint32(table[0].bits))
*result = uint32(table[0].value)
return true
}
func safeReadSymbol(table []huffmanCode, br *bitReader, result *uint32) bool {
var val uint32
if safeGetBits(br, 15, &val) {
*result = decodeSymbol(val, table, br)
return true
}
return safeDecodeSymbol(table, br, result)
}
/* Makes a look-up in first level Huffman table. Peeks 8 bits. */
func preloadSymbol(safe int, table []huffmanCode, br *bitReader, bits *uint32, value *uint32) {
if safe != 0 {
return
}
table = table[BrotliGetBits(br, huffmanTableBits):]
*bits = uint32(table[0].bits)
*value = uint32(table[0].value)
}
/* Decodes the next Huffman code using data prepared by PreloadSymbol.
Reads 0 - 15 bits. Also peeks 8 following bits. */
func readPreloadedSymbol(table []huffmanCode, br *bitReader, bits *uint32, value *uint32) uint32 {
var result uint32 = *value
var ext []huffmanCode
if *bits > huffmanTableBits {
var val uint32 = get16BitsUnmasked(br)
ext = table[val&huffmanTableMask:][*value:]
var mask uint32 = bitMask((*bits - huffmanTableBits))
dropBits(br, huffmanTableBits)
ext = ext[(val>>huffmanTableBits)&mask:]
dropBits(br, uint32(ext[0].bits))
result = uint32(ext[0].value)
} else {
dropBits(br, *bits)
}
preloadSymbol(0, table, br, bits, value)
return result
}
func log2Floor(x uint32) uint32 {
var result uint32 = 0
for x != 0 {
x >>= 1
result++
}
return result
}
/* Reads (s->symbol + 1) symbols.
Totally 1..4 symbols are read, 1..11 bits each.
The list of symbols MUST NOT contain duplicates. */
func readSimpleHuffmanSymbols(alphabet_size uint32, max_symbol uint32, s *Reader) int {
var br *bitReader = &s.br
var max_bits uint32 = log2Floor(alphabet_size - 1)
var i uint32 = s.sub_loop_counter
/* max_bits == 1..11; symbol == 0..3; 1..44 bits will be read. */
var num_symbols uint32 = s.symbol
for i <= num_symbols {
var v uint32
if !safeReadBits(br, max_bits, &v) {
s.sub_loop_counter = i
s.substate_huffman = BROTLI_STATE_HUFFMAN_SIMPLE_READ
return decoderNeedsMoreInput
}
if v >= max_symbol {
return decoderErrorFormatSimpleHuffmanAlphabet
}
s.symbols_lists_array[i] = uint16(v)
i++
}
for i = 0; i < num_symbols; i++ {
var k uint32 = i + 1
for ; k <= num_symbols; k++ {
if s.symbols_lists_array[i] == s.symbols_lists_array[k] {
return decoderErrorFormatSimpleHuffmanSame
}
}
}
return decoderSuccess
}
/* Process single decoded symbol code length:
A) reset the repeat variable
B) remember code length (if it is not 0)
C) extend corresponding index-chain
D) reduce the Huffman space
E) update the histogram */
func processSingleCodeLength(code_len uint32, symbol *uint32, repeat *uint32, space *uint32, prev_code_len *uint32, symbol_lists SymbolList, code_length_histo []uint16, next_symbol []int) {
*repeat = 0
if code_len != 0 { /* code_len == 1..15 */
SymbolListPut(symbol_lists, next_symbol[code_len], uint16(*symbol))
next_symbol[code_len] = int(*symbol)
*prev_code_len = code_len
*space -= 32768 >> code_len
code_length_histo[code_len]++
}
(*symbol)++
}
/* Process repeated symbol code length.
A) Check if it is the extension of previous repeat sequence; if the decoded
value is not BROTLI_REPEAT_PREVIOUS_CODE_LENGTH, then it is a new
symbol-skip
B) Update repeat variable
C) Check if operation is feasible (fits alphabet)
D) For each symbol do the same operations as in ProcessSingleCodeLength
PRECONDITION: code_len == BROTLI_REPEAT_PREVIOUS_CODE_LENGTH or
code_len == BROTLI_REPEAT_ZERO_CODE_LENGTH */
func processRepeatedCodeLength(code_len uint32, repeat_delta uint32, alphabet_size uint32, symbol *uint32, repeat *uint32, space *uint32, prev_code_len *uint32, repeat_code_len *uint32, symbol_lists SymbolList, code_length_histo []uint16, next_symbol []int) {
var old_repeat uint32 /* for BROTLI_REPEAT_ZERO_CODE_LENGTH */ /* for BROTLI_REPEAT_ZERO_CODE_LENGTH */
var extra_bits uint32 = 3
var new_len uint32 = 0
if code_len == repeatPreviousCodeLength {
new_len = *prev_code_len
extra_bits = 2
}
if *repeat_code_len != new_len {
*repeat = 0
*repeat_code_len = new_len
}
old_repeat = *repeat
if *repeat > 0 {
*repeat -= 2
*repeat <<= extra_bits
}
*repeat += repeat_delta + 3
repeat_delta = *repeat - old_repeat
if *symbol+repeat_delta > alphabet_size {
*symbol = alphabet_size
*space = 0xFFFFF
return
}
if *repeat_code_len != 0 {
var last uint = uint(*symbol + repeat_delta)
var next int = next_symbol[*repeat_code_len]
for {
SymbolListPut(symbol_lists, next, uint16(*symbol))
next = int(*symbol)
(*symbol)++
if (*symbol) == uint32(last) {
break
}
}
next_symbol[*repeat_code_len] = next
*space -= repeat_delta << (15 - *repeat_code_len)
code_length_histo[*repeat_code_len] = uint16(uint32(code_length_histo[*repeat_code_len]) + repeat_delta)
} else {
*symbol += repeat_delta
}
}
/* Reads and decodes symbol codelengths. */
func readSymbolCodeLengths(alphabet_size uint32, s *Reader) int {
var br *bitReader = &s.br
var symbol uint32 = s.symbol
var repeat uint32 = s.repeat
var space uint32 = s.space
var prev_code_len uint32 = s.prev_code_len
var repeat_code_len uint32 = s.repeat_code_len
var symbol_lists SymbolList = s.symbol_lists
var code_length_histo []uint16 = s.code_length_histo[:]
var next_symbol []int = s.next_symbol[:]
if !warmupBitReader(br) {
return decoderNeedsMoreInput
}
var p []huffmanCode
for symbol < alphabet_size && space > 0 {
p = s.table[:]
var code_len uint32
if !checkInputAmount(br, shortFillBitWindowRead) {
s.symbol = symbol
s.repeat = repeat
s.prev_code_len = prev_code_len
s.repeat_code_len = repeat_code_len
s.space = space
return decoderNeedsMoreInput
}
fillBitWindow16(br)
p = p[getBitsUnmasked(br)&uint64(bitMask(huffmanMaxCodeLengthCodeLength)):]
dropBits(br, uint32(p[0].bits)) /* Use 1..5 bits. */
code_len = uint32(p[0].value) /* code_len == 0..17 */
if code_len < repeatPreviousCodeLength {
processSingleCodeLength(code_len, &symbol, &repeat, &space, &prev_code_len, symbol_lists, code_length_histo, next_symbol) /* code_len == 16..17, extra_bits == 2..3 */
} else {
var extra_bits uint32
if code_len == repeatPreviousCodeLength {
extra_bits = 2
} else {
extra_bits = 3
}
var repeat_delta uint32 = uint32(getBitsUnmasked(br)) & bitMask(extra_bits)
dropBits(br, extra_bits)
processRepeatedCodeLength(code_len, repeat_delta, alphabet_size, &symbol, &repeat, &space, &prev_code_len, &repeat_code_len, symbol_lists, code_length_histo, next_symbol)
}
}
s.space = space
return decoderSuccess
}
func safeReadSymbolCodeLengths(alphabet_size uint32, s *Reader) int {
var br *bitReader = &s.br
var get_byte bool = false
var p []huffmanCode
for s.symbol < alphabet_size && s.space > 0 {
p = s.table[:]
var code_len uint32
var available_bits uint32
var bits uint32 = 0
if get_byte && !pullByte(br) {
return decoderNeedsMoreInput
}
get_byte = false
available_bits = getAvailableBits(br)
if available_bits != 0 {
bits = uint32(getBitsUnmasked(br))
}
p = p[bits&bitMask(huffmanMaxCodeLengthCodeLength):]
if uint32(p[0].bits) > available_bits {
get_byte = true
continue
}
code_len = uint32(p[0].value) /* code_len == 0..17 */
if code_len < repeatPreviousCodeLength {
dropBits(br, uint32(p[0].bits))
processSingleCodeLength(code_len, &s.symbol, &s.repeat, &s.space, &s.prev_code_len, s.symbol_lists, s.code_length_histo[:], s.next_symbol[:]) /* code_len == 16..17, extra_bits == 2..3 */
} else {
var extra_bits uint32 = code_len - 14
var repeat_delta uint32 = (bits >> p[0].bits) & bitMask(extra_bits)
if available_bits < uint32(p[0].bits)+extra_bits {
get_byte = true
continue
}
dropBits(br, uint32(p[0].bits)+extra_bits)
processRepeatedCodeLength(code_len, repeat_delta, alphabet_size, &s.symbol, &s.repeat, &s.space, &s.prev_code_len, &s.repeat_code_len, s.symbol_lists, s.code_length_histo[:], s.next_symbol[:])
}
}
return decoderSuccess
}
/* Reads and decodes 15..18 codes using static prefix code.
Each code is 2..4 bits long. In total 30..72 bits are used. */
func readCodeLengthCodeLengths(s *Reader) int {
var br *bitReader = &s.br
var num_codes uint32 = s.repeat
var space uint32 = s.space
var i uint32 = s.sub_loop_counter
for ; i < codeLengthCodes; i++ {
var code_len_idx byte = kCodeLengthCodeOrder[i]
var ix uint32
var v uint32
if !safeGetBits(br, 4, &ix) {
var available_bits uint32 = getAvailableBits(br)
if available_bits != 0 {
ix = uint32(getBitsUnmasked(br) & 0xF)
} else {
ix = 0
}
if uint32(kCodeLengthPrefixLength[ix]) > available_bits {
s.sub_loop_counter = i
s.repeat = num_codes
s.space = space
s.substate_huffman = BROTLI_STATE_HUFFMAN_COMPLEX
return decoderNeedsMoreInput
}
}
v = uint32(kCodeLengthPrefixValue[ix])
dropBits(br, uint32(kCodeLengthPrefixLength[ix]))
s.code_length_code_lengths[code_len_idx] = byte(v)
if v != 0 {
space = space - (32 >> v)
num_codes++
s.code_length_histo[v]++
if space-1 >= 32 {
/* space is 0 or wrapped around. */
break
}
}
}
if num_codes != 1 && space != 0 {
return decoderErrorFormatClSpace
}
return decoderSuccess
}
/* Decodes the Huffman tables.
There are 2 scenarios:
A) Huffman code contains only few symbols (1..4). Those symbols are read
directly; their code lengths are defined by the number of symbols.
For this scenario 4 - 49 bits will be read.
B) 2-phase decoding:
B.1) Small Huffman table is decoded; it is specified with code lengths
encoded with predefined entropy code. 32 - 74 bits are used.
B.2) Decoded table is used to decode code lengths of symbols in resulting
Huffman table. In worst case 3520 bits are read. */
func readHuffmanCode(alphabet_size uint32, max_symbol uint32, table []huffmanCode, opt_table_size *uint32, s *Reader) int {
var br *bitReader = &s.br
/* Unnecessary masking, but might be good for safety. */
alphabet_size &= 0x7FF
/* State machine. */
for {
switch s.substate_huffman {
case BROTLI_STATE_HUFFMAN_NONE:
if !safeReadBits(br, 2, &s.sub_loop_counter) {
return decoderNeedsMoreInput
}
/* The value is used as follows:
1 for simple code;
0 for no skipping, 2 skips 2 code lengths, 3 skips 3 code lengths */
if s.sub_loop_counter != 1 {
s.space = 32
s.repeat = 0 /* num_codes */
var i int
for i = 0; i <= huffmanMaxCodeLengthCodeLength; i++ {
s.code_length_histo[i] = 0
}
for i = 0; i < codeLengthCodes; i++ {
s.code_length_code_lengths[i] = 0
}
s.substate_huffman = BROTLI_STATE_HUFFMAN_COMPLEX
continue
}
fallthrough
/* Read symbols, codes & code lengths directly. */
/* Fall through. */
case BROTLI_STATE_HUFFMAN_SIMPLE_SIZE:
if !safeReadBits(br, 2, &s.symbol) { /* num_symbols */
s.substate_huffman = BROTLI_STATE_HUFFMAN_SIMPLE_SIZE
return decoderNeedsMoreInput
}
s.sub_loop_counter = 0
fallthrough
/* Fall through. */
case BROTLI_STATE_HUFFMAN_SIMPLE_READ:
{
var result int = readSimpleHuffmanSymbols(alphabet_size, max_symbol, s)
if result != decoderSuccess {
return result
}
}
fallthrough
/* Fall through. */
case BROTLI_STATE_HUFFMAN_SIMPLE_BUILD:
{
var table_size uint32
if s.symbol == 3 {
var bits uint32
if !safeReadBits(br, 1, &bits) {
s.substate_huffman = BROTLI_STATE_HUFFMAN_SIMPLE_BUILD
return decoderNeedsMoreInput
}
s.symbol += bits
}
table_size = buildSimpleHuffmanTable(table, huffmanTableBits, s.symbols_lists_array[:], s.symbol)
if opt_table_size != nil {
*opt_table_size = table_size
}
s.substate_huffman = BROTLI_STATE_HUFFMAN_NONE
return decoderSuccess
}
fallthrough
/* Decode Huffman-coded code lengths. */
case BROTLI_STATE_HUFFMAN_COMPLEX:
{
var i uint32
var result int = readCodeLengthCodeLengths(s)
if result != decoderSuccess {
return result
}
buildCodeLengthsHuffmanTable(s.table[:], s.code_length_code_lengths[:], s.code_length_histo[:])
for i = 0; i < 16; i++ {
s.code_length_histo[i] = 0
}
for i = 0; i <= huffmanMaxCodeLength; i++ {
s.next_symbol[i] = int(i) - (huffmanMaxCodeLength + 1)
SymbolListPut(s.symbol_lists, s.next_symbol[i], 0xFFFF)
}
s.symbol = 0
s.prev_code_len = initialRepeatedCodeLength
s.repeat = 0
s.repeat_code_len = 0
s.space = 32768
s.substate_huffman = BROTLI_STATE_HUFFMAN_LENGTH_SYMBOLS
}
fallthrough
/* Fall through. */
case BROTLI_STATE_HUFFMAN_LENGTH_SYMBOLS:
{
var table_size uint32
var result int = readSymbolCodeLengths(max_symbol, s)
if result == decoderNeedsMoreInput {
result = safeReadSymbolCodeLengths(max_symbol, s)
}
if result != decoderSuccess {
return result
}
if s.space != 0 {
return decoderErrorFormatHuffmanSpace
}
table_size = buildHuffmanTable(table, huffmanTableBits, s.symbol_lists, s.code_length_histo[:])
if opt_table_size != nil {
*opt_table_size = table_size
}
s.substate_huffman = BROTLI_STATE_HUFFMAN_NONE
return decoderSuccess
}
fallthrough
default:
return decoderErrorUnreachable
}
}
}
/* Decodes a block length by reading 3..39 bits. */
func readBlockLength(table []huffmanCode, br *bitReader) uint32 {
var code uint32
var nbits uint32
code = readSymbol(table, br)
nbits = uint32(kBlockLengthPrefixCode1[code].nbits) /* nbits == 2..24 */
return uint32(kBlockLengthPrefixCode1[code].offset) + readBits(br, nbits)
}
/* WARNING: if state is not BROTLI_STATE_READ_BLOCK_LENGTH_NONE, then
reading can't be continued with ReadBlockLength. */
func safeReadBlockLength(s *Reader, result *uint32, table []huffmanCode, br *bitReader) bool {
var index uint32
if s.substate_read_block_length == BROTLI_STATE_READ_BLOCK_LENGTH_NONE {
if !safeReadSymbol(table, br, &index) {
return false
}
} else {
index = s.block_length_index
}
{
var bits uint32 /* nbits == 2..24 */
var nbits uint32 = uint32(kBlockLengthPrefixCode1[index].nbits)
if !safeReadBits(br, nbits, &bits) {
s.block_length_index = index
s.substate_read_block_length = BROTLI_STATE_READ_BLOCK_LENGTH_SUFFIX
return false
}
*result = uint32(kBlockLengthPrefixCode1[index].offset) + bits
s.substate_read_block_length = BROTLI_STATE_READ_BLOCK_LENGTH_NONE
return true
}
}
/* Transform:
1) initialize list L with values 0, 1,... 255
2) For each input element X:
2.1) let Y = L[X]
2.2) remove X-th element from L
2.3) prepend Y to L
2.4) append Y to output
In most cases max(Y) <= 7, so most of L remains intact.
To reduce the cost of initialization, we reuse L, remember the upper bound
of Y values, and reinitialize only first elements in L.
Most of input values are 0 and 1. To reduce number of branches, we replace
inner for loop with do-while. */
func inverseMoveToFrontTransform(v []byte, v_len uint32, state *Reader) {
var mtf [256]byte
var i int
for i = 1; i < 256; i++ {
mtf[i] = byte(i)
}
var mtf_1 byte
/* Transform the input. */
for i = 0; uint32(i) < v_len; i++ {
var index int = int(v[i])
var value byte = mtf[index]
v[i] = value
mtf_1 = value
for index >= 1 {
index--
mtf[index+1] = mtf[index]
}
mtf[0] = mtf_1
}
}
/* Decodes a series of Huffman table using ReadHuffmanCode function. */
func huffmanTreeGroupDecode(group *huffmanTreeGroup, s *Reader) int {
if s.substate_tree_group != BROTLI_STATE_TREE_GROUP_LOOP {
s.next = group.codes
s.htree_index = 0
s.substate_tree_group = BROTLI_STATE_TREE_GROUP_LOOP
}
for s.htree_index < int(group.num_htrees) {
var table_size uint32
var result int = readHuffmanCode(uint32(group.alphabet_size), uint32(group.max_symbol), s.next, &table_size, s)
if result != decoderSuccess {
return result
}
group.htrees[s.htree_index] = s.next
s.next = s.next[table_size:]
s.htree_index++
}
s.substate_tree_group = BROTLI_STATE_TREE_GROUP_NONE
return decoderSuccess
}
/* Decodes a context map.
Decoding is done in 4 phases:
1) Read auxiliary information (6..16 bits) and allocate memory.
In case of trivial context map, decoding is finished at this phase.
2) Decode Huffman table using ReadHuffmanCode function.
This table will be used for reading context map items.
3) Read context map items; "0" values could be run-length encoded.
4) Optionally, apply InverseMoveToFront transform to the resulting map. */
func decodeContextMap(context_map_size uint32, num_htrees *uint32, context_map_arg *[]byte, s *Reader) int {
var br *bitReader = &s.br
var result int = decoderSuccess
switch int(s.substate_context_map) {
case BROTLI_STATE_CONTEXT_MAP_NONE:
result = decodeVarLenUint8(s, br, num_htrees)
if result != decoderSuccess {
return result
}
(*num_htrees)++
s.context_index = 0
*context_map_arg = make([]byte, uint(context_map_size))
if *context_map_arg == nil {
return decoderErrorAllocContextMap
}
if *num_htrees <= 1 {
for i := 0; i < int(context_map_size); i++ {
(*context_map_arg)[i] = 0
}
return decoderSuccess
}
s.substate_context_map = BROTLI_STATE_CONTEXT_MAP_READ_PREFIX
fallthrough
/* Fall through. */
case BROTLI_STATE_CONTEXT_MAP_READ_PREFIX:
{
var bits uint32
/* In next stage ReadHuffmanCode uses at least 4 bits, so it is safe
to peek 4 bits ahead. */
if !safeGetBits(br, 5, &bits) {
return decoderNeedsMoreInput
}
if bits&1 != 0 { /* Use RLE for zeros. */
s.max_run_length_prefix = (bits >> 1) + 1
dropBits(br, 5)
} else {
s.max_run_length_prefix = 0
dropBits(br, 1)
}
s.substate_context_map = BROTLI_STATE_CONTEXT_MAP_HUFFMAN
}
fallthrough
/* Fall through. */
case BROTLI_STATE_CONTEXT_MAP_HUFFMAN:
{
var alphabet_size uint32 = *num_htrees + s.max_run_length_prefix
result = readHuffmanCode(alphabet_size, alphabet_size, s.context_map_table[:], nil, s)
if result != decoderSuccess {
return result
}
s.code = 0xFFFF
s.substate_context_map = BROTLI_STATE_CONTEXT_MAP_DECODE
}
fallthrough
/* Fall through. */
case BROTLI_STATE_CONTEXT_MAP_DECODE:
{
var context_index uint32 = s.context_index
var max_run_length_prefix uint32 = s.max_run_length_prefix
var context_map []byte = *context_map_arg
var code uint32 = s.code
var skip_preamble bool = (code != 0xFFFF)
for context_index < context_map_size || skip_preamble {
if !skip_preamble {
if !safeReadSymbol(s.context_map_table[:], br, &code) {
s.code = 0xFFFF
s.context_index = context_index
return decoderNeedsMoreInput
}
if code == 0 {
context_map[context_index] = 0
context_index++
continue
}
if code > max_run_length_prefix {
context_map[context_index] = byte(code - max_run_length_prefix)
context_index++
continue
}
} else {
skip_preamble = false
}
/* RLE sub-stage. */
{
var reps uint32
if !safeReadBits(br, code, &reps) {
s.code = code
s.context_index = context_index
return decoderNeedsMoreInput
}
reps += 1 << code
if context_index+reps > context_map_size {
return decoderErrorFormatContextMapRepeat
}
for {
context_map[context_index] = 0
context_index++
reps--
if reps == 0 {
break
}
}
}
}
}
fallthrough
/* Fall through. */
case BROTLI_STATE_CONTEXT_MAP_TRANSFORM:
{
var bits uint32
if !safeReadBits(br, 1, &bits) {
s.substate_context_map = BROTLI_STATE_CONTEXT_MAP_TRANSFORM
return decoderNeedsMoreInput
}
if bits != 0 {
inverseMoveToFrontTransform(*context_map_arg, context_map_size, s)
}
s.substate_context_map = BROTLI_STATE_CONTEXT_MAP_NONE
return decoderSuccess
}
fallthrough
default:
return decoderErrorUnreachable
}
}
/* Decodes a command or literal and updates block type ring-buffer.
Reads 3..54 bits. */
func decodeBlockTypeAndLength(safe int, s *Reader, tree_type int) bool {
var max_block_type uint32 = s.num_block_types[tree_type]
var type_tree []huffmanCode
type_tree = s.block_type_trees[tree_type*huffmanMaxSize258:]
var len_tree []huffmanCode
len_tree = s.block_len_trees[tree_type*huffmanMaxSize26:]
var br *bitReader = &s.br
var ringbuffer []uint32 = s.block_type_rb[tree_type*2:]
var block_type uint32
if max_block_type <= 1 {
return false
}
/* Read 0..15 + 3..39 bits. */
if safe == 0 {
block_type = readSymbol(type_tree, br)
s.block_length[tree_type] = readBlockLength(len_tree, br)
} else {
var memento bitReaderState
bitReaderSaveState(br, &memento)
if !safeReadSymbol(type_tree, br, &block_type) {
return false
}
if !safeReadBlockLength(s, &s.block_length[tree_type], len_tree, br) {
s.substate_read_block_length = BROTLI_STATE_READ_BLOCK_LENGTH_NONE
bitReaderRestoreState(br, &memento)
return false
}
}
if block_type == 1 {
block_type = ringbuffer[1] + 1
} else if block_type == 0 {
block_type = ringbuffer[0]
} else {
block_type -= 2
}
if block_type >= max_block_type {
block_type -= max_block_type
}
ringbuffer[0] = ringbuffer[1]
ringbuffer[1] = block_type
return true
}
func detectTrivialLiteralBlockTypes(s *Reader) {
var i uint
for i = 0; i < 8; i++ {
s.trivial_literal_contexts[i] = 0
}
for i = 0; uint32(i) < s.num_block_types[0]; i++ {
var offset uint = i << literalContextBits
var error uint = 0
var sample uint = uint(s.context_map[offset])
var j uint
for j = 0; j < 1<<literalContextBits; {
var k int
for k = 0; k < 4; k++ {
error |= uint(s.context_map[offset+j]) ^ sample
j++
}
}
if error == 0 {
s.trivial_literal_contexts[i>>5] |= 1 << (i & 31)
}
}
}
func prepareLiteralDecoding(s *Reader) {
var context_mode byte
var trivial uint
var block_type uint32 = s.block_type_rb[1]
var context_offset uint32 = block_type << literalContextBits
s.context_map_slice = s.context_map[context_offset:]
trivial = uint(s.trivial_literal_contexts[block_type>>5])
s.trivial_literal_context = int((trivial >> (block_type & 31)) & 1)
s.literal_htree = []huffmanCode(s.literal_hgroup.htrees[s.context_map_slice[0]])
context_mode = s.context_modes[block_type] & 3
s.context_lookup = getContextLUT(int(context_mode))
}
/* Decodes the block type and updates the state for literal context.
Reads 3..54 bits. */
func decodeLiteralBlockSwitchInternal(safe int, s *Reader) bool {
if !decodeBlockTypeAndLength(safe, s, 0) {
return false
}
prepareLiteralDecoding(s)
return true
}
func decodeLiteralBlockSwitch(s *Reader) {
decodeLiteralBlockSwitchInternal(0, s)
}
func safeDecodeLiteralBlockSwitch(s *Reader) bool {
return decodeLiteralBlockSwitchInternal(1, s)
}
/* Block switch for insert/copy length.
Reads 3..54 bits. */
func decodeCommandBlockSwitchInternal(safe int, s *Reader) bool {
if !decodeBlockTypeAndLength(safe, s, 1) {
return false
}
s.htree_command = []huffmanCode(s.insert_copy_hgroup.htrees[s.block_type_rb[3]])
return true
}
func decodeCommandBlockSwitch(s *Reader) {
decodeCommandBlockSwitchInternal(0, s)
}
func safeDecodeCommandBlockSwitch(s *Reader) bool {
return decodeCommandBlockSwitchInternal(1, s)
}
/* Block switch for distance codes.
Reads 3..54 bits. */
func decodeDistanceBlockSwitchInternal(safe int, s *Reader) bool {
if !decodeBlockTypeAndLength(safe, s, 2) {
return false
}
s.dist_context_map_slice = s.dist_context_map[s.block_type_rb[5]<<distanceContextBits:]
s.dist_htree_index = s.dist_context_map_slice[s.distance_context]
return true
}
func decodeDistanceBlockSwitch(s *Reader) {
decodeDistanceBlockSwitchInternal(0, s)
}
func safeDecodeDistanceBlockSwitch(s *Reader) bool {
return decodeDistanceBlockSwitchInternal(1, s)
}
func unwrittenBytes(s *Reader, wrap bool) uint {
var pos uint
if wrap && s.pos > s.ringbuffer_size {
pos = uint(s.ringbuffer_size)
} else {
pos = uint(s.pos)
}
var partial_pos_rb uint = (s.rb_roundtrips * uint(s.ringbuffer_size)) + pos
return partial_pos_rb - s.partial_pos_out
}
/* Dumps output.
Returns BROTLI_DECODER_NEEDS_MORE_OUTPUT only if there is more output to push
and either ring-buffer is as big as window size, or |force| is true. */
func writeRingBuffer(s *Reader, available_out *uint, next_out *[]byte, total_out *uint, force bool) int {
var start []byte
start = s.ringbuffer[s.partial_pos_out&uint(s.ringbuffer_mask):]
var to_write uint = unwrittenBytes(s, true)
var num_written uint = *available_out
if num_written > to_write {
num_written = to_write
}
if s.meta_block_remaining_len < 0 {
return decoderErrorFormatBlockLength1
}
if next_out != nil && *next_out == nil {
*next_out = start
} else {
if next_out != nil {
copy(*next_out, start[:num_written])
*next_out = (*next_out)[num_written:]
}
}
*available_out -= num_written
s.partial_pos_out += num_written
if total_out != nil {
*total_out = s.partial_pos_out
}
if num_written < to_write {
if s.ringbuffer_size == 1<<s.window_bits || force {
return decoderNeedsMoreOutput
} else {
return decoderSuccess
}
}
/* Wrap ring buffer only if it has reached its maximal size. */
if s.ringbuffer_size == 1<<s.window_bits && s.pos >= s.ringbuffer_size {
s.pos -= s.ringbuffer_size
s.rb_roundtrips++
if uint(s.pos) != 0 {
s.should_wrap_ringbuffer = 1
} else {
s.should_wrap_ringbuffer = 0
}
}
return decoderSuccess
}
func wrapRingBuffer(s *Reader) {
if s.should_wrap_ringbuffer != 0 {
copy(s.ringbuffer, s.ringbuffer_end[:uint(s.pos)])
s.should_wrap_ringbuffer = 0
}
}
/* Allocates ring-buffer.
s->ringbuffer_size MUST be updated by BrotliCalculateRingBufferSize before
this function is called.
Last two bytes of ring-buffer are initialized to 0, so context calculation
could be done uniformly for the first two and all other positions. */
func ensureRingBuffer(s *Reader) bool {
var old_ringbuffer []byte = s.ringbuffer
if s.ringbuffer_size == s.new_ringbuffer_size {
return true
}
s.ringbuffer = make([]byte, uint(s.new_ringbuffer_size)+uint(kRingBufferWriteAheadSlack))
if s.ringbuffer == nil {
/* Restore previous value. */
s.ringbuffer = old_ringbuffer
return false
}
s.ringbuffer[s.new_ringbuffer_size-2] = 0
s.ringbuffer[s.new_ringbuffer_size-1] = 0
if !(old_ringbuffer == nil) {
copy(s.ringbuffer, old_ringbuffer[:uint(s.pos)])
old_ringbuffer = nil
}
s.ringbuffer_size = s.new_ringbuffer_size
s.ringbuffer_mask = s.new_ringbuffer_size - 1
s.ringbuffer_end = s.ringbuffer[s.ringbuffer_size:]
return true
}
func copyUncompressedBlockToOutput(available_out *uint, next_out *[]byte, total_out *uint, s *Reader) int {
/* TODO: avoid allocation for single uncompressed block. */
if !ensureRingBuffer(s) {
return decoderErrorAllocRingBuffer1
}
/* State machine */
for {
switch s.substate_uncompressed {
case BROTLI_STATE_UNCOMPRESSED_NONE:
{
var nbytes int = int(getRemainingBytes(&s.br))
if nbytes > s.meta_block_remaining_len {
nbytes = s.meta_block_remaining_len
}
if s.pos+nbytes > s.ringbuffer_size {
nbytes = s.ringbuffer_size - s.pos
}
/* Copy remaining bytes from s->br.buf_ to ring-buffer. */
copyBytes(s.ringbuffer[s.pos:], &s.br, uint(nbytes))
s.pos += nbytes
s.meta_block_remaining_len -= nbytes
if s.pos < 1<<s.window_bits {
if s.meta_block_remaining_len == 0 {
return decoderSuccess
}
return decoderNeedsMoreInput
}
s.substate_uncompressed = BROTLI_STATE_UNCOMPRESSED_WRITE
}
fallthrough
/* Fall through. */
case BROTLI_STATE_UNCOMPRESSED_WRITE:
{
var result int
result = writeRingBuffer(s, available_out, next_out, total_out, false)
if result != decoderSuccess {
return result
}
if s.ringbuffer_size == 1<<s.window_bits {
s.max_distance = s.max_backward_distance
}
s.substate_uncompressed = BROTLI_STATE_UNCOMPRESSED_NONE
break
}
}
}
assert(false) /* Unreachable */
return 0
}
/* Calculates the smallest feasible ring buffer.
If we know the data size is small, do not allocate more ring buffer
size than needed to reduce memory usage.
When this method is called, metablock size and flags MUST be decoded. */
func calculateRingBufferSize(s *Reader) {
var window_size int = 1 << s.window_bits
var new_ringbuffer_size int = window_size
var min_size int
/* We need at least 2 bytes of ring buffer size to get the last two
bytes for context from there */
if s.ringbuffer_size != 0 {
min_size = s.ringbuffer_size
} else {
min_size = 1024
}
var output_size int
/* If maximum is already reached, no further extension is retired. */
if s.ringbuffer_size == window_size {
return
}
/* Metadata blocks does not touch ring buffer. */
if s.is_metadata != 0 {
return
}
if s.ringbuffer == nil {
output_size = 0
} else {
output_size = s.pos
}
output_size += s.meta_block_remaining_len
if min_size < output_size {
min_size = output_size
} else {
min_size = min_size
}
if !(s.canny_ringbuffer_allocation == 0) {
/* Reduce ring buffer size to save memory when server is unscrupulous.
In worst case memory usage might be 1.5x bigger for a short period of
ring buffer reallocation. */
for new_ringbuffer_size>>1 >= min_size {
new_ringbuffer_size >>= 1
}
}
s.new_ringbuffer_size = new_ringbuffer_size
}
/* Reads 1..256 2-bit context modes. */
func readContextModes(s *Reader) int {
var br *bitReader = &s.br
var i int = s.loop_counter
for i < int(s.num_block_types[0]) {
var bits uint32
if !safeReadBits(br, 2, &bits) {
s.loop_counter = i
return decoderNeedsMoreInput
}
s.context_modes[i] = byte(bits)
i++
}
return decoderSuccess
}
func takeDistanceFromRingBuffer(s *Reader) {
if s.distance_code == 0 {
s.dist_rb_idx--
s.distance_code = s.dist_rb[s.dist_rb_idx&3]
/* Compensate double distance-ring-buffer roll for dictionary items. */
s.distance_context = 1
} else {
var distance_code int = s.distance_code << 1
var kDistanceShortCodeIndexOffset uint32 = 0xAAAFFF1B
var kDistanceShortCodeValueOffset uint32 = 0xFA5FA500
var v int = (s.dist_rb_idx + int(kDistanceShortCodeIndexOffset>>uint(distance_code))) & 0x3
/* kDistanceShortCodeIndexOffset has 2-bit values from LSB:
3, 2, 1, 0, 3, 3, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2 */
/* kDistanceShortCodeValueOffset has 2-bit values from LSB:
-0, 0,-0, 0,-1, 1,-2, 2,-3, 3,-1, 1,-2, 2,-3, 3 */
s.distance_code = s.dist_rb[v]
v = int(kDistanceShortCodeValueOffset>>uint(distance_code)) & 0x3
if distance_code&0x3 != 0 {
s.distance_code += v
} else {
s.distance_code -= v
if s.distance_code <= 0 {
/* A huge distance will cause a () soon.
This is a little faster than failing here. */
s.distance_code = 0x7FFFFFFF
}
}
}
}
func safeReadBitsMaybeZero(br *bitReader, n_bits uint32, val *uint32) bool {
if n_bits != 0 {
return safeReadBits(br, n_bits, val)
} else {
*val = 0
return true
}
}
/* Precondition: s->distance_code < 0. */
func readDistanceInternal(safe int, s *Reader, br *bitReader) bool {
var distval int
var memento bitReaderState
var distance_tree []huffmanCode = []huffmanCode(s.distance_hgroup.htrees[s.dist_htree_index])
if safe == 0 {
s.distance_code = int(readSymbol(distance_tree, br))
} else {
var code uint32
bitReaderSaveState(br, &memento)
if !safeReadSymbol(distance_tree, br, &code) {
return false
}
s.distance_code = int(code)
}
/* Convert the distance code to the actual distance by possibly
looking up past distances from the s->ringbuffer. */
s.distance_context = 0
if s.distance_code&^0xF == 0 {
takeDistanceFromRingBuffer(s)
s.block_length[2]--
return true
}
distval = s.distance_code - int(s.num_direct_distance_codes)
if distval >= 0 {
var nbits uint32
var postfix int
var offset int
if safe == 0 && (s.distance_postfix_bits == 0) {
nbits = (uint32(distval) >> 1) + 1
offset = ((2 + (distval & 1)) << nbits) - 4
s.distance_code = int(s.num_direct_distance_codes) + offset + int(readBits(br, nbits))
} else {
/* This branch also works well when s->distance_postfix_bits == 0. */
var bits uint32
postfix = distval & s.distance_postfix_mask
distval >>= s.distance_postfix_bits
nbits = (uint32(distval) >> 1) + 1
if safe != 0 {
if !safeReadBitsMaybeZero(br, nbits, &bits) {
s.distance_code = -1 /* Restore precondition. */
bitReaderRestoreState(br, &memento)
return false
}
} else {
bits = readBits(br, nbits)
}
offset = ((2 + (distval & 1)) << nbits) - 4
s.distance_code = int(s.num_direct_distance_codes) + ((offset + int(bits)) << s.distance_postfix_bits) + postfix
}
}
s.distance_code = s.distance_code - numDistanceShortCodes + 1
s.block_length[2]--
return true
}
func readDistance(s *Reader, br *bitReader) {
readDistanceInternal(0, s, br)
}
func safeReadDistance(s *Reader, br *bitReader) bool {
return readDistanceInternal(1, s, br)
}
func readCommandInternal(safe int, s *Reader, br *bitReader, insert_length *int) bool {
var cmd_code uint32
var insert_len_extra uint32 = 0
var copy_length uint32
var v CmdLutElement
var memento bitReaderState
if safe == 0 {
cmd_code = readSymbol(s.htree_command, br)
} else {
bitReaderSaveState(br, &memento)
if !safeReadSymbol(s.htree_command, br, &cmd_code) {
return false
}
}
v = kCmdLut[cmd_code]
s.distance_code = int(v.distance_code)
s.distance_context = int(v.context)
s.dist_htree_index = s.dist_context_map_slice[s.distance_context]
*insert_length = int(v.insert_len_offset)
if safe == 0 {
if v.insert_len_extra_bits != 0 {
insert_len_extra = readBits(br, uint32(v.insert_len_extra_bits))
}
copy_length = readBits(br, uint32(v.copy_len_extra_bits))
} else {
if !safeReadBitsMaybeZero(br, uint32(v.insert_len_extra_bits), &insert_len_extra) || !safeReadBitsMaybeZero(br, uint32(v.copy_len_extra_bits), &copy_length) {
bitReaderRestoreState(br, &memento)
return false
}
}
s.copy_length = int(copy_length) + int(v.copy_len_offset)
s.block_length[1]--
*insert_length += int(insert_len_extra)
return true
}
func readCommand(s *Reader, br *bitReader, insert_length *int) {
readCommandInternal(0, s, br, insert_length)
}
func safeReadCommand(s *Reader, br *bitReader, insert_length *int) bool {
return readCommandInternal(1, s, br, insert_length)
}
func checkInputAmountMaybeSafe(safe int, br *bitReader, num uint) bool {
if safe != 0 {
return true
}
return checkInputAmount(br, num)
}
func processCommandsInternal(safe int, s *Reader) int {
var pos int = s.pos
var i int = s.loop_counter
var result int = decoderSuccess
var br *bitReader = &s.br
var hc []huffmanCode
if !checkInputAmountMaybeSafe(safe, br, 28) {
result = decoderNeedsMoreInput
goto saveStateAndReturn
}
if safe == 0 {
warmupBitReader(br)
}
/* Jump into state machine. */
if s.state == BROTLI_STATE_COMMAND_BEGIN {
goto CommandBegin
} else if s.state == BROTLI_STATE_COMMAND_INNER {
goto CommandInner
} else if s.state == BROTLI_STATE_COMMAND_POST_DECODE_LITERALS {
goto CommandPostDecodeLiterals
} else if s.state == BROTLI_STATE_COMMAND_POST_WRAP_COPY {
goto CommandPostWrapCopy
} else {
return decoderErrorUnreachable
}
CommandBegin:
if safe != 0 {
s.state = BROTLI_STATE_COMMAND_BEGIN
}
if !checkInputAmountMaybeSafe(safe, br, 28) { /* 156 bits + 7 bytes */
s.state = BROTLI_STATE_COMMAND_BEGIN
result = decoderNeedsMoreInput
goto saveStateAndReturn
}
if s.block_length[1] == 0 {
if safe != 0 {
if !safeDecodeCommandBlockSwitch(s) {
result = decoderNeedsMoreInput
goto saveStateAndReturn
}
} else {
decodeCommandBlockSwitch(s)
}
goto CommandBegin
}
/* Read the insert/copy length in the command. */
if safe != 0 {
if !safeReadCommand(s, br, &i) {
result = decoderNeedsMoreInput
goto saveStateAndReturn
}
} else {
readCommand(s, br, &i)
}
if i == 0 {
goto CommandPostDecodeLiterals
}
s.meta_block_remaining_len -= i
CommandInner:
if safe != 0 {
s.state = BROTLI_STATE_COMMAND_INNER
}
/* Read the literals in the command. */
if s.trivial_literal_context != 0 {
var bits uint32
var value uint32
preloadSymbol(safe, s.literal_htree, br, &bits, &value)
for {
if !checkInputAmountMaybeSafe(safe, br, 28) { /* 162 bits + 7 bytes */
s.state = BROTLI_STATE_COMMAND_INNER
result = decoderNeedsMoreInput
goto saveStateAndReturn
}
if s.block_length[0] == 0 {
if safe != 0 {
if !safeDecodeLiteralBlockSwitch(s) {
result = decoderNeedsMoreInput
goto saveStateAndReturn
}
} else {
decodeLiteralBlockSwitch(s)
}
preloadSymbol(safe, s.literal_htree, br, &bits, &value)
if s.trivial_literal_context == 0 {
goto CommandInner
}
}
if safe == 0 {
s.ringbuffer[pos] = byte(readPreloadedSymbol(s.literal_htree, br, &bits, &value))
} else {
var literal uint32
if !safeReadSymbol(s.literal_htree, br, &literal) {
result = decoderNeedsMoreInput
goto saveStateAndReturn
}
s.ringbuffer[pos] = byte(literal)
}
s.block_length[0]--
pos++
if pos == s.ringbuffer_size {
s.state = BROTLI_STATE_COMMAND_INNER_WRITE
i--
goto saveStateAndReturn
}
i--
if i == 0 {
break
}
}
} else {
var p1 byte = s.ringbuffer[(pos-1)&s.ringbuffer_mask]
var p2 byte = s.ringbuffer[(pos-2)&s.ringbuffer_mask]
for {
var context byte
if !checkInputAmountMaybeSafe(safe, br, 28) { /* 162 bits + 7 bytes */
s.state = BROTLI_STATE_COMMAND_INNER
result = decoderNeedsMoreInput
goto saveStateAndReturn
}
if s.block_length[0] == 0 {
if safe != 0 {
if !safeDecodeLiteralBlockSwitch(s) {
result = decoderNeedsMoreInput
goto saveStateAndReturn
}
} else {
decodeLiteralBlockSwitch(s)
}
if s.trivial_literal_context != 0 {
goto CommandInner
}
}
context = getContext(p1, p2, s.context_lookup)
hc = []huffmanCode(s.literal_hgroup.htrees[s.context_map_slice[context]])
p2 = p1
if safe == 0 {
p1 = byte(readSymbol(hc, br))
} else {
var literal uint32
if !safeReadSymbol(hc, br, &literal) {
result = decoderNeedsMoreInput
goto saveStateAndReturn
}
p1 = byte(literal)
}
s.ringbuffer[pos] = p1
s.block_length[0]--
pos++
if pos == s.ringbuffer_size {
s.state = BROTLI_STATE_COMMAND_INNER_WRITE
i--
goto saveStateAndReturn
}
i--
if i == 0 {
break
}
}
}
if s.meta_block_remaining_len <= 0 {
s.state = BROTLI_STATE_METABLOCK_DONE
goto saveStateAndReturn
}
CommandPostDecodeLiterals:
if safe != 0 {
s.state = BROTLI_STATE_COMMAND_POST_DECODE_LITERALS
}
if s.distance_code >= 0 {
/* Implicit distance case. */
if s.distance_code != 0 {
s.distance_context = 0
} else {
s.distance_context = 1
}
s.dist_rb_idx--
s.distance_code = s.dist_rb[s.dist_rb_idx&3]
} else {
/* Read distance code in the command, unless it was implicitly zero. */
if s.block_length[2] == 0 {
if safe != 0 {
if !safeDecodeDistanceBlockSwitch(s) {
result = decoderNeedsMoreInput
goto saveStateAndReturn
}
} else {
decodeDistanceBlockSwitch(s)
}
}
if safe != 0 {
if !safeReadDistance(s, br) {
result = decoderNeedsMoreInput
goto saveStateAndReturn
}
} else {
readDistance(s, br)
}
}
if s.max_distance != s.max_backward_distance {
if pos < s.max_backward_distance {
s.max_distance = pos
} else {
s.max_distance = s.max_backward_distance
}
}
i = s.copy_length
/* Apply copy of LZ77 back-reference, or static dictionary reference if
the distance is larger than the max LZ77 distance */
if s.distance_code > s.max_distance {
/* The maximum allowed distance is BROTLI_MAX_ALLOWED_DISTANCE = 0x7FFFFFFC.
With this choice, no signed overflow can occur after decoding
a special distance code (e.g., after adding 3 to the last distance). */
if s.distance_code > maxAllowedDistance {
return decoderErrorFormatDistance
}
if i >= minDictionaryWordLength && i <= maxDictionaryWordLength {
var address int = s.distance_code - s.max_distance - 1
var words *dictionary = s.dictionary
var transforms *BrotliTransforms = s.transforms
var offset int = int(s.dictionary.offsets_by_length[i])
var shift uint32 = uint32(s.dictionary.size_bits_by_length[i])
var mask int = int(bitMask(shift))
var word_idx int = address & mask
var transform_idx int = address >> shift
/* Compensate double distance-ring-buffer roll. */
s.dist_rb_idx += s.distance_context
offset += word_idx * i
if words.data == nil {
return decoderErrorDictionaryNotSet
}
if transform_idx < int(transforms.num_transforms) {
var word []byte
word = words.data[offset:]
var len int = i
if transform_idx == int(transforms.cutOffTransforms[0]) {
copy(s.ringbuffer[pos:], word[:uint(len)])
} else {
len = BrotliTransformDictionaryWord(s.ringbuffer[pos:], word, int(len), transforms, transform_idx)
}
pos += int(len)
s.meta_block_remaining_len -= int(len)
if pos >= s.ringbuffer_size {
s.state = BROTLI_STATE_COMMAND_POST_WRITE_1
goto saveStateAndReturn
}
} else {
return decoderErrorFormatTransform
}
} else {
return decoderErrorFormatDictionary
}
} else {
var src_start int = (pos - s.distance_code) & s.ringbuffer_mask
var copy_dst []byte
copy_dst = s.ringbuffer[pos:]
var copy_src []byte
copy_src = s.ringbuffer[src_start:]
var dst_end int = pos + i
var src_end int = src_start + i
/* Update the recent distances cache. */
s.dist_rb[s.dist_rb_idx&3] = s.distance_code
s.dist_rb_idx++
s.meta_block_remaining_len -= i
/* There are 32+ bytes of slack in the ring-buffer allocation.
Also, we have 16 short codes, that make these 16 bytes irrelevant
in the ring-buffer. Let's copy over them as a first guess. */
copy(copy_dst, copy_src[:16])
if src_end > pos && dst_end > src_start {
/* Regions intersect. */
goto CommandPostWrapCopy
}
if dst_end >= s.ringbuffer_size || src_end >= s.ringbuffer_size {
/* At least one region wraps. */
goto CommandPostWrapCopy
}
pos += i
if i > 16 {
if i > 32 {
copy(copy_dst[16:], copy_src[16:][:uint(i-16)])
} else {
/* This branch covers about 45% cases.
Fixed size short copy allows more compiler optimizations. */
copy(copy_dst[16:], copy_src[16:][:16])
}
}
}
if s.meta_block_remaining_len <= 0 {
/* Next metablock, if any. */
s.state = BROTLI_STATE_METABLOCK_DONE
goto saveStateAndReturn
} else {
goto CommandBegin
}
CommandPostWrapCopy:
{
var wrap_guard int = s.ringbuffer_size - pos
for {
i--
if i < 0 {
break
}
s.ringbuffer[pos] = s.ringbuffer[(pos-s.distance_code)&s.ringbuffer_mask]
pos++
wrap_guard--
if wrap_guard == 0 {
s.state = BROTLI_STATE_COMMAND_POST_WRITE_2
goto saveStateAndReturn
}
}
}
if s.meta_block_remaining_len <= 0 {
/* Next metablock, if any. */
s.state = BROTLI_STATE_METABLOCK_DONE
goto saveStateAndReturn
} else {
goto CommandBegin
}
saveStateAndReturn:
s.pos = pos
s.loop_counter = i
return result
}
func processCommands(s *Reader) int {
return processCommandsInternal(0, s)
}
func safeProcessCommands(s *Reader) int {
return processCommandsInternal(1, s)
}
/* Returns the maximum number of distance symbols which can only represent
distances not exceeding BROTLI_MAX_ALLOWED_DISTANCE. */
var maxDistanceSymbol_bound = [maxNpostfix + 1]uint32{0, 4, 12, 28}
var maxDistanceSymbol_diff = [maxNpostfix + 1]uint32{73, 126, 228, 424}
func maxDistanceSymbol(ndirect uint32, npostfix uint32) uint32 {
var postfix uint32 = 1 << npostfix
if ndirect < maxDistanceSymbol_bound[npostfix] {
return ndirect + maxDistanceSymbol_diff[npostfix] + postfix
} else if ndirect > maxDistanceSymbol_bound[npostfix]+postfix {
return ndirect + maxDistanceSymbol_diff[npostfix]
} else {
return maxDistanceSymbol_bound[npostfix] + maxDistanceSymbol_diff[npostfix] + postfix
}
}
/* Invariant: input stream is never overconsumed:
- invalid input implies that the whole stream is invalid -> any amount of
input could be read and discarded
- when result is "needs more input", then at least one more byte is REQUIRED
to complete decoding; all input data MUST be consumed by decoder, so
client could swap the input buffer
- when result is "needs more output" decoder MUST ensure that it doesn't
hold more than 7 bits in bit reader; this saves client from swapping input
buffer ahead of time
- when result is "success" decoder MUST return all unused data back to input
buffer; this is possible because the invariant is held on enter */
func decoderDecompressStream(s *Reader, available_in *uint, next_in *[]byte, available_out *uint, next_out *[]byte) int {
var result int = decoderSuccess
var br *bitReader = &s.br
/* Do not try to process further in a case of unrecoverable error. */
if int(s.error_code) < 0 {
return decoderResultError
}
if *available_out != 0 && (next_out == nil || *next_out == nil) {
return saveErrorCode(s, decoderErrorInvalidArguments)
}
if *available_out == 0 {
next_out = nil
}
if s.buffer_length == 0 { /* Just connect bit reader to input stream. */
br.input_len = *available_in
br.input = *next_in
br.byte_pos = 0
} else {
/* At least one byte of input is required. More than one byte of input may
be required to complete the transaction -> reading more data must be
done in a loop -> do it in a main loop. */
result = decoderNeedsMoreInput
br.input = s.buffer.u8[:]
br.byte_pos = 0
}
/* State machine */
for {
if result != decoderSuccess {
/* Error, needs more input/output. */
if result == decoderNeedsMoreInput {
if s.ringbuffer != nil { /* Pro-actively push output. */
var intermediate_result int = writeRingBuffer(s, available_out, next_out, nil, true)
/* WriteRingBuffer checks s->meta_block_remaining_len validity. */
if int(intermediate_result) < 0 {
result = intermediate_result
break
}
}
if s.buffer_length != 0 { /* Used with internal buffer. */
if br.byte_pos == br.input_len {
/* Successfully finished read transaction.
Accumulator contains less than 8 bits, because internal buffer
is expanded byte-by-byte until it is enough to complete read. */
s.buffer_length = 0
/* Switch to input stream and restart. */
result = decoderSuccess
br.input_len = *available_in
br.input = *next_in
br.byte_pos = 0
continue
} else if *available_in != 0 {
/* Not enough data in buffer, but can take one more byte from
input stream. */
result = decoderSuccess
s.buffer.u8[s.buffer_length] = (*next_in)[0]
s.buffer_length++
br.input_len = uint(s.buffer_length)
*next_in = (*next_in)[1:]
(*available_in)--
/* Retry with more data in buffer. */
continue
}
/* Can't finish reading and no more input. */
break
/* Input stream doesn't contain enough input. */
} else {
/* Copy tail to internal buffer and return. */
*next_in = br.input[br.byte_pos:]
*available_in = br.input_len - br.byte_pos
for *available_in != 0 {
s.buffer.u8[s.buffer_length] = (*next_in)[0]
s.buffer_length++
*next_in = (*next_in)[1:]
(*available_in)--
}
break
}
}
/* Unreachable. */
/* Fail or needs more output. */
if s.buffer_length != 0 {
/* Just consumed the buffered input and produced some output. Otherwise
it would result in "needs more input". Reset internal buffer. */
s.buffer_length = 0
} else {
/* Using input stream in last iteration. When decoder switches to input
stream it has less than 8 bits in accumulator, so it is safe to
return unused accumulator bits there. */
bitReaderUnload(br)
*available_in = br.input_len - br.byte_pos
*next_in = br.input[br.byte_pos:]
}
break
}
switch s.state {
/* Prepare to the first read. */
case BROTLI_STATE_UNINITED:
if !warmupBitReader(br) {
result = decoderNeedsMoreInput
break
}
/* Decode window size. */
result = decodeWindowBits(s, br) /* Reads 1..8 bits. */
if result != decoderSuccess {
break
}
if s.large_window {
s.state = BROTLI_STATE_LARGE_WINDOW_BITS
break
}
s.state = BROTLI_STATE_INITIALIZE
case BROTLI_STATE_LARGE_WINDOW_BITS:
if !safeReadBits(br, 6, &s.window_bits) {
result = decoderNeedsMoreInput
break
}
if s.window_bits < largeMinWbits || s.window_bits > largeMaxWbits {
result = decoderErrorFormatWindowBits
break
}
s.state = BROTLI_STATE_INITIALIZE
fallthrough
/* Maximum distance, see section 9.1. of the spec. */
/* Fall through. */
case BROTLI_STATE_INITIALIZE:
s.max_backward_distance = (1 << s.window_bits) - windowGap
/* Allocate memory for both block_type_trees and block_len_trees. */
s.block_type_trees = make([]huffmanCode, (3 * (huffmanMaxSize258 + huffmanMaxSize26)))
if s.block_type_trees == nil {
result = decoderErrorAllocBlockTypeTrees
break
}
s.block_len_trees = s.block_type_trees[3*huffmanMaxSize258:]
s.state = BROTLI_STATE_METABLOCK_BEGIN
fallthrough
/* Fall through. */
case BROTLI_STATE_METABLOCK_BEGIN:
BrotliDecoderStateMetablockBegin(s)
s.state = BROTLI_STATE_METABLOCK_HEADER
fallthrough
/* Fall through. */
case BROTLI_STATE_METABLOCK_HEADER:
result = decodeMetaBlockLength(s, br)
/* Reads 2 - 31 bits. */
if result != decoderSuccess {
break
}
if s.is_metadata != 0 || s.is_uncompressed != 0 {
if !bitReaderJumpToByteBoundary(br) {
result = decoderErrorFormatPadding1
break
}
}
if s.is_metadata != 0 {
s.state = BROTLI_STATE_METADATA
break
}
if s.meta_block_remaining_len == 0 {
s.state = BROTLI_STATE_METABLOCK_DONE
break
}
calculateRingBufferSize(s)
if s.is_uncompressed != 0 {
s.state = BROTLI_STATE_UNCOMPRESSED
break
}
s.loop_counter = 0
s.state = BROTLI_STATE_HUFFMAN_CODE_0
case BROTLI_STATE_UNCOMPRESSED:
{
result = copyUncompressedBlockToOutput(available_out, next_out, nil, s)
if result != decoderSuccess {
break
}
s.state = BROTLI_STATE_METABLOCK_DONE
break
}
fallthrough
case BROTLI_STATE_METADATA:
for ; s.meta_block_remaining_len > 0; s.meta_block_remaining_len-- {
var bits uint32
/* Read one byte and ignore it. */
if !safeReadBits(br, 8, &bits) {
result = decoderNeedsMoreInput
break
}
}
if result == decoderSuccess {
s.state = BROTLI_STATE_METABLOCK_DONE
}
case BROTLI_STATE_HUFFMAN_CODE_0:
if s.loop_counter >= 3 {
s.state = BROTLI_STATE_METABLOCK_HEADER_2
break
}
/* Reads 1..11 bits. */
result = decodeVarLenUint8(s, br, &s.num_block_types[s.loop_counter])
if result != decoderSuccess {
break
}
s.num_block_types[s.loop_counter]++
if s.num_block_types[s.loop_counter] < 2 {
s.loop_counter++
break
}
s.state = BROTLI_STATE_HUFFMAN_CODE_1
fallthrough
/* Fall through. */
case BROTLI_STATE_HUFFMAN_CODE_1:
{
var alphabet_size uint32 = s.num_block_types[s.loop_counter] + 2
var tree_offset int = s.loop_counter * huffmanMaxSize258
result = readHuffmanCode(alphabet_size, alphabet_size, s.block_type_trees[tree_offset:], nil, s)
if result != decoderSuccess {
break
}
s.state = BROTLI_STATE_HUFFMAN_CODE_2
}
fallthrough
/* Fall through. */
case BROTLI_STATE_HUFFMAN_CODE_2:
{
var alphabet_size uint32 = numBlockLenSymbols
var tree_offset int = s.loop_counter * huffmanMaxSize26
result = readHuffmanCode(alphabet_size, alphabet_size, s.block_len_trees[tree_offset:], nil, s)
if result != decoderSuccess {
break
}
s.state = BROTLI_STATE_HUFFMAN_CODE_3
}
fallthrough
/* Fall through. */
case BROTLI_STATE_HUFFMAN_CODE_3:
{
var tree_offset int = s.loop_counter * huffmanMaxSize26
if !safeReadBlockLength(s, &s.block_length[s.loop_counter], s.block_len_trees[tree_offset:], br) {
result = decoderNeedsMoreInput
break
}
s.loop_counter++
s.state = BROTLI_STATE_HUFFMAN_CODE_0
break
}
fallthrough
case BROTLI_STATE_METABLOCK_HEADER_2:
{
var bits uint32
if !safeReadBits(br, 6, &bits) {
result = decoderNeedsMoreInput
break
}
s.distance_postfix_bits = bits & bitMask(2)
bits >>= 2
s.num_direct_distance_codes = numDistanceShortCodes + (bits << s.distance_postfix_bits)
s.distance_postfix_mask = int(bitMask(s.distance_postfix_bits))
s.context_modes = make([]byte, uint(s.num_block_types[0]))
if s.context_modes == nil {
result = decoderErrorAllocContextModes
break
}
s.loop_counter = 0
s.state = BROTLI_STATE_CONTEXT_MODES
}
fallthrough
/* Fall through. */
case BROTLI_STATE_CONTEXT_MODES:
result = readContextModes(s)
if result != decoderSuccess {
break
}
s.state = BROTLI_STATE_CONTEXT_MAP_1
fallthrough
/* Fall through. */
case BROTLI_STATE_CONTEXT_MAP_1:
result = decodeContextMap(s.num_block_types[0]<<literalContextBits, &s.num_literal_htrees, &s.context_map, s)
if result != decoderSuccess {
break
}
detectTrivialLiteralBlockTypes(s)
s.state = BROTLI_STATE_CONTEXT_MAP_2
fallthrough
/* Fall through. */
case BROTLI_STATE_CONTEXT_MAP_2:
{
var num_direct_codes uint32 = s.num_direct_distance_codes - numDistanceShortCodes
var num_distance_codes uint32
var max_distance_symbol uint32
if s.large_window {
num_distance_codes = uint32(distanceAlphabetSize(uint(s.distance_postfix_bits), uint(num_direct_codes), largeMaxDistanceBits))
max_distance_symbol = maxDistanceSymbol(num_direct_codes, s.distance_postfix_bits)
} else {
num_distance_codes = uint32(distanceAlphabetSize(uint(s.distance_postfix_bits), uint(num_direct_codes), maxDistanceBits))
max_distance_symbol = num_distance_codes
}
var allocation_success bool = true
result = decodeContextMap(s.num_block_types[2]<<distanceContextBits, &s.num_dist_htrees, &s.dist_context_map, s)
if result != decoderSuccess {
break
}
if !BrotliDecoderHuffmanTreeGroupInit(s, &s.literal_hgroup, numLiteralSymbols, numLiteralSymbols, s.num_literal_htrees) {
allocation_success = false
}
if !BrotliDecoderHuffmanTreeGroupInit(s, &s.insert_copy_hgroup, numCommandSymbols, numCommandSymbols, s.num_block_types[1]) {
allocation_success = false
}
if !BrotliDecoderHuffmanTreeGroupInit(s, &s.distance_hgroup, num_distance_codes, max_distance_symbol, s.num_dist_htrees) {
allocation_success = false
}
if !allocation_success {
return saveErrorCode(s, decoderErrorAllocTreeGroups)
}
s.loop_counter = 0
s.state = BROTLI_STATE_TREE_GROUP
}
fallthrough
/* Fall through. */
case BROTLI_STATE_TREE_GROUP:
{
var hgroup *huffmanTreeGroup = nil
switch s.loop_counter {
case 0:
hgroup = &s.literal_hgroup
case 1:
hgroup = &s.insert_copy_hgroup
case 2:
hgroup = &s.distance_hgroup
default:
return saveErrorCode(s, decoderErrorUnreachable)
}
result = huffmanTreeGroupDecode(hgroup, s)
if result != decoderSuccess {
break
}
s.loop_counter++
if s.loop_counter >= 3 {
prepareLiteralDecoding(s)
s.dist_context_map_slice = s.dist_context_map
s.htree_command = []huffmanCode(s.insert_copy_hgroup.htrees[0])
if !ensureRingBuffer(s) {
result = decoderErrorAllocRingBuffer2
break
}
s.state = BROTLI_STATE_COMMAND_BEGIN
}
break
}
fallthrough
case BROTLI_STATE_COMMAND_BEGIN,
/* Fall through. */
BROTLI_STATE_COMMAND_INNER,
/* Fall through. */
BROTLI_STATE_COMMAND_POST_DECODE_LITERALS,
/* Fall through. */
BROTLI_STATE_COMMAND_POST_WRAP_COPY:
result = processCommands(s)
if result == decoderNeedsMoreInput {
result = safeProcessCommands(s)
}
case BROTLI_STATE_COMMAND_INNER_WRITE,
/* Fall through. */
BROTLI_STATE_COMMAND_POST_WRITE_1,
/* Fall through. */
BROTLI_STATE_COMMAND_POST_WRITE_2:
result = writeRingBuffer(s, available_out, next_out, nil, false)
if result != decoderSuccess {
break
}
wrapRingBuffer(s)
if s.ringbuffer_size == 1<<s.window_bits {
s.max_distance = s.max_backward_distance
}
if s.state == BROTLI_STATE_COMMAND_POST_WRITE_1 {
if s.meta_block_remaining_len == 0 {
/* Next metablock, if any. */
s.state = BROTLI_STATE_METABLOCK_DONE
} else {
s.state = BROTLI_STATE_COMMAND_BEGIN
}
break
} else if s.state == BROTLI_STATE_COMMAND_POST_WRITE_2 {
s.state = BROTLI_STATE_COMMAND_POST_WRAP_COPY /* BROTLI_STATE_COMMAND_INNER_WRITE */
} else {
if s.loop_counter == 0 {
if s.meta_block_remaining_len == 0 {
s.state = BROTLI_STATE_METABLOCK_DONE
} else {
s.state = BROTLI_STATE_COMMAND_POST_DECODE_LITERALS
}
break
}
s.state = BROTLI_STATE_COMMAND_INNER
}
case BROTLI_STATE_METABLOCK_DONE:
if s.meta_block_remaining_len < 0 {
result = decoderErrorFormatBlockLength2
break
}
BrotliDecoderStateCleanupAfterMetablock(s)
if s.is_last_metablock == 0 {
s.state = BROTLI_STATE_METABLOCK_BEGIN
break
}
if !bitReaderJumpToByteBoundary(br) {
result = decoderErrorFormatPadding2
break
}
if s.buffer_length == 0 {
bitReaderUnload(br)
*available_in = br.input_len - br.byte_pos
*next_in = br.input[br.byte_pos:]
}
s.state = BROTLI_STATE_DONE
fallthrough
/* Fall through. */
case BROTLI_STATE_DONE:
if s.ringbuffer != nil {
result = writeRingBuffer(s, available_out, next_out, nil, true)
if result != decoderSuccess {
break
}
}
return saveErrorCode(s, result)
}
}
return saveErrorCode(s, result)
}
func decoderHasMoreOutput(s *Reader) bool {
/* After unrecoverable error remaining output is considered nonsensical. */
if int(s.error_code) < 0 {
return false
}
return s.ringbuffer != nil && unwrittenBytes(s, false) != 0
}
func decoderGetErrorCode(s *Reader) int {
return int(s.error_code)
}
func decoderErrorString(c int) string {
switch c {
case decoderNoError:
return "NO_ERROR"
case decoderSuccess:
return "SUCCESS"
case decoderNeedsMoreInput:
return "NEEDS_MORE_INPUT"
case decoderNeedsMoreOutput:
return "NEEDS_MORE_OUTPUT"
case decoderErrorFormatExuberantNibble:
return "EXUBERANT_NIBBLE"
case decoderErrorFormatReserved:
return "RESERVED"
case decoderErrorFormatExuberantMetaNibble:
return "EXUBERANT_META_NIBBLE"
case decoderErrorFormatSimpleHuffmanAlphabet:
return "SIMPLE_HUFFMAN_ALPHABET"
case decoderErrorFormatSimpleHuffmanSame:
return "SIMPLE_HUFFMAN_SAME"
case decoderErrorFormatClSpace:
return "CL_SPACE"
case decoderErrorFormatHuffmanSpace:
return "HUFFMAN_SPACE"
case decoderErrorFormatContextMapRepeat:
return "CONTEXT_MAP_REPEAT"
case decoderErrorFormatBlockLength1:
return "BLOCK_LENGTH_1"
case decoderErrorFormatBlockLength2:
return "BLOCK_LENGTH_2"
case decoderErrorFormatTransform:
return "TRANSFORM"
case decoderErrorFormatDictionary:
return "DICTIONARY"
case decoderErrorFormatWindowBits:
return "WINDOW_BITS"
case decoderErrorFormatPadding1:
return "PADDING_1"
case decoderErrorFormatPadding2:
return "PADDING_2"
case decoderErrorFormatDistance:
return "DISTANCE"
case decoderErrorDictionaryNotSet:
return "DICTIONARY_NOT_SET"
case decoderErrorInvalidArguments:
return "INVALID_ARGUMENTS"
case decoderErrorAllocContextModes:
return "CONTEXT_MODES"
case decoderErrorAllocTreeGroups:
return "TREE_GROUPS"
case decoderErrorAllocContextMap:
return "CONTEXT_MAP"
case decoderErrorAllocRingBuffer1:
return "RING_BUFFER_1"
case decoderErrorAllocRingBuffer2:
return "RING_BUFFER_2"
case decoderErrorAllocBlockTypeTrees:
return "BLOCK_TYPE_TREES"
case decoderErrorUnreachable:
return "UNREACHABLE"
default:
return "INVALID"
}
}
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