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android / platform / external / zstd / 9700f925 / . / contrib / educational_decoder / zstd_decompress.c
blob: 8dc159008324fbd362d4895bd97cfbed75fa21b0 [file] [log] [blame]
/// Zstandard educational decoder implementation
/// See https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/// Zstandard decompression functions.
/// `dst` must point to a space at least as large as the reconstructed output.
size_t ZSTD_decompress(void *dst, size_t dst_len, const void *src,
size_t src_len);
/// If `dict != NULL` and `dict_len >= 8`, does the same thing as
/// `ZSTD_decompress` but uses the provided dict
size_t ZSTD_decompress_with_dict(void *dst, size_t dst_len, const void *src,
size_t src_len, const void *dict,
size_t dict_len);
/******* UTILITY MACROS AND TYPES *********************************************/
#define MAX_WINDOW_SIZE ((size_t)512 << 20)
// Max block size decompressed size is 128 KB and literal blocks must be smaller
// than that
#define MAX_LITERALS_SIZE ((size_t)(1024 * 128))
#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define ERROR(s) \
do { \
fprintf(stderr, "Error: %s\n", s); \
exit(1); \
} while (0)
#define INP_SIZE() \
ERROR("Input buffer smaller than it should be or input is " \
"corrupted")
#define OUT_SIZE() ERROR("Output buffer too small for output")
#define CORRUPTION() ERROR("Corruption detected while decompressing")
#define BAD_ALLOC() ERROR("Memory allocation error")
typedef uint8_t u8;
typedef uint16_t u16;
typedef uint32_t u32;
typedef uint64_t u64;
typedef int8_t i8;
typedef int16_t i16;
typedef int32_t i32;
typedef int64_t i64;
/******* END UTILITY MACROS AND TYPES *****************************************/
/******* IMPLEMENTATION PRIMITIVE PROTOTYPES **********************************/
/// The implementations for these functions can be found at the bottom of this
/// file. They implement low-level functionality needed for the higher level
/// decompression functions.
/*** CIRCULAR BUFFER ******************/
/// A standard circular buffer, used to facilitate back reference commands
typedef struct {
u8 *ptr;
size_t idx, last_flush, size;
} cbuf_t;
/// Initialize a circular buffer
static void cbuf_init(cbuf_t *buf, size_t size);
static void cbuf_free(cbuf_t *buf);
/// Copies up to `src_len` bytes from `src` into the buffer, stopping if it
/// would need to flush.
/// Returns the total amount of data copied.
static size_t cbuf_write_data(cbuf_t *buf, const u8 *src, size_t src_len);
/// Copies `len` bytes from `offset` back in the buffer, stopping if it would
/// need to flush.
/// Returns the number of bytes copied.
static size_t cbuf_copy_offset(cbuf_t *buf, size_t offset, size_t len);
/// Writes up to `len` copies of `byte`, stopping if would need to flush.
/// Returns the number of bytes copied.
static size_t cbuf_repeat_byte(cbuf_t *buf, u8 byte, size_t len);
/// The `full` versions of the above functions write the full amount requested,
/// flushing to `out` when necessary.
/// They return the number of bytes flushed to `out`, if any.
static size_t cbuf_write_data_full(cbuf_t *buf, const u8 *src, size_t src_len,
u8 *out, size_t out_len);
static size_t cbuf_copy_offset_full(cbuf_t *buf, size_t offset, size_t len,
u8 *out, size_t out_len);
static size_t cbuf_repeat_byte_full(cbuf_t *buf, u8 byte, size_t len, u8 *out,
size_t out_len);
/// Flushes any unflushed data to `dst`
static size_t cbuf_flush(cbuf_t *buf, u8 *dst, size_t dst_len);
/*** END CIRCULAR BUFFER **************/
/*** BITSTREAM OPERATIONS *************/
/// Read `num` bits (up to 64) from `src + offset`, where `offset` is in bits
static inline u64 read_bits_LE(const u8 *src, int num, size_t offset);
/// Read bits from the end of a HUF or FSE bitstream. `offset` is in bits, so
/// it updates `offset` to `offset - bits`, and then reads `bits` bits from
/// `src + offset`. If the offset becomes negative, the extra bits at the
/// bottom are filled in with `0` bits instead of reading from before `src`.
static inline u64 STREAM_read_bits(const u8 *src, int bits, i64 *offset);
/*** END BITSTREAM OPERATIONS *********/
/*** BIT COUNTING OPERATIONS **********/
/// Returns `x`, where `2^x` is the smallest power of 2 greater than or equal to
/// `num`, or `-1` if `num > 2^63`
static inline int log2sup(u64 num);
/// Returns `x`, where `2^x` is the largest power of 2 less than or equal to
/// `num`, or `-1` if `num == 0`.
static inline int log2inf(u64 num);
/*** END BIT COUNTING OPERATIONS ******/
/*** HUFFMAN PRIMITIVES ***************/
// Table decode method uses exponential memory, so we need to limit depth
#define HUF_MAX_BITS (16)
// Limit the maximum number of symbols to 256 so we can store a symbol in a byte
#define HUF_MAX_SYMBS (256)
/// Structure containing all tables necessary for efficient Huffman decoding
typedef struct {
u8 *symbols;
u8 *num_bits;
int max_bits;
} HUF_dtable;
/// Decode a single symbol and read in enough bits to refresh the state
static inline u8 HUF_decode_symbol(HUF_dtable *dtable, u16 *state,
const u8 *src, i64 *offset);
/// Read in a full state's worth of bits to initialize it
static inline void HUF_init_state(HUF_dtable *dtable, u16 *state, const u8 *src,
i64 *offset);
/// Initialize a Huffman decoding table using the table of bit counts provided
static void HUF_init_dtable(HUF_dtable *table, u8 *bits, int num_symbs);
/// Initialize a Huffman decoding table using the table of weights provided
/// Weights follow the definition provided in the Zstandard specification
static void HUF_init_dtable_usingweights(HUF_dtable *table, u8 *weights,
int num_symbs);
/// Decompresses a single Huffman stream, returns the number of bytes decoded.
/// `src_len` must be the exact length of the Huffman-coded block.
static size_t HUF_decompress_1stream(HUF_dtable *table, u8 *dst, size_t dst_len,
const u8 *src, size_t src_len);
/// Same as previous but decodes 4 streams, formatted as in the Zstandard
/// specification.
/// `src_len` must be the exact length of the Huffman-coded block.
static size_t HUF_decompress_4stream(HUF_dtable *dtable, u8 *dst,
size_t dst_len, const u8 *src,
size_t src_len);
/// Free the malloc'ed parts of a decoding table
static void HUF_free_dtable(HUF_dtable *dtable);
/// Deep copy a decoding table, so that it can be used and free'd without
/// impacting the source table.
static void HUF_copy_dtable(HUF_dtable *dst, const HUF_dtable *src);
/*** END HUFFMAN PRIMITIVES ***********/
/*** FSE PRIMITIVES *******************/
/// For more description of FSE see
/// https://github.com/Cyan4973/FiniteStateEntropy/
// FSE table decoding uses exponential memory, so limit the maximum accuracy
#define FSE_MAX_ACCURACY_LOG (15)
// Limit the maximum number of symbols so they can be stored in a single byte
#define FSE_MAX_SYMBS (256)
/// The tables needed to decode FSE encoded streams
typedef struct {
u8 *symbols;
u8 *num_bits;
u16 *new_state_base;
int accuracy_log;
} FSE_dtable;
/// Return the symbol for the current state
static inline u8 FSE_peek_symbol(FSE_dtable *dtable, u16 state);
/// Read the number of bits necessary to update state, update, and shift offset
/// back to reflect the bits read
static inline void FSE_update_state(FSE_dtable *dtable, u16 *state,
const u8 *src, i64 *offset);
/// Combine peek and update: decode a symbol and update the state
static inline u8 FSE_decode_symbol(FSE_dtable *dtable, u16 *state,
const u8 *src, i64 *offset);
/// Read bits from the stream to initialize the state and shift offset back
static inline void FSE_init_state(FSE_dtable *dtable, u16 *state, const u8 *src,
i64 *offset);
/// Decompress two interleaved bitstreams (e.g. compressed Huffman weights)
/// using an FSE decoding table. `src_len` must be the exact length of the
/// block.
static size_t FSE_decompress_interleaved2(FSE_dtable *dtable, u8 *dst,
size_t dst_len, const u8 *src,
size_t src_len);
/// Initialize a decoding table using normalized frequencies.
static void FSE_init_dtable(FSE_dtable *dtable, const i16 *norm_freqs,
int num_symbs, int accuracy_log);
/// Decode an FSE header as defined in the Zstandard format specification and
/// use the decoded frequencies to initialize a decoding table.
static size_t FSE_decode_header(FSE_dtable *dtable, const u8 *src,
size_t src_len, int max_accuracy_log);
/// Initialize an FSE table that will always return the same symbol and consume
/// 0 bits per symbol, to be used for RLE mode in sequence commands
static void FSE_init_dtable_rle(FSE_dtable *dtable, u8 symb);
/// Free the malloc'ed parts of a decoding table
static void FSE_free_dtable(FSE_dtable *dtable);
/// Deep copy a decoding table, so that it can be used and free'd without
/// impacting the source table.
static void FSE_copy_dtable(FSE_dtable *dst, const FSE_dtable *src);
/*** END FSE PRIMITIVES ***************/
/******* END IMPLEMENTATION PRIMITIVE PROTOTYPES ******************************/
/******* ZSTD HELPER STRUCTS AND PROTOTYPES ***********************************/
/// Input and output pointers to allow them to be advanced by
/// functions that consume input/produce output
typedef struct {
u8 *dst;
size_t dst_len;
const u8 *src;
size_t src_len;
} io_streams_t;
/// The context needed to decode blocks in a frame
typedef struct {
size_t window_size;
size_t frame_content_size;
// The total amount of data available for backreferences, to determine if an
// offset too large to be correct
size_t current_total_output;
// A sliding window of the past `window_size` bytes decoded
cbuf_t window;
// Entropy encoding tables so they can be repeated by future blocks instead
// of
// retransmitting
HUF_dtable literals_dtable;
FSE_dtable ll_dtable;
FSE_dtable ml_dtable;
FSE_dtable of_dtable;
// The last 3 offsets for the special "repeat offsets". Array size is 4 so
// that previous_offsets[1] corresponds to the most recent offset
u64 previous_offsets[4];
// The dictionary id for this frame if one exists
u32 dictionary_id;
int single_segment_flag;
int content_checksum_flag;
} frame_context_t;
/// The decoded contents of a dictionary so that it doesn't have to be repeated
/// for each frame that uses it
typedef struct {
// Entropy tables
HUF_dtable literals_dtable;
FSE_dtable ll_dtable;
FSE_dtable ml_dtable;
FSE_dtable of_dtable;
// Raw content for backreferences
u8 *content;
size_t content_size;
// Offset history to prepopulate the frame's history
u64 previous_offsets[4];
u32 dictionary_id;
} dictionary_t;
/// A tuple containing the parts necessary to decode and execute a ZSTD sequence
/// command
typedef struct {
u32 literal_length;
u32 match_length;
u32 offset;
} sequence_command_t;
/// The decoder works top-down, starting at the high level like Zstd frames, and
/// working down to lower more technical levels such as blocks, literals, and
/// sequences. The high-level functions roughly follow the outline of the
/// format specification:
/// https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md
/// Before the implementation of each high-level function declared here, the
/// prototypes for their helper functions are defined and explained
/// Decode a single Zstd frame, or error if the input is not a valid frame.
/// Accepts a dict argument, which may be NULL indicating no dictionary.
/// See
/// https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md#frame-concatenation
static void decode_frame(io_streams_t *streams, dictionary_t *dict);
// Decode data in a compressed block
static void decompress_block(io_streams_t *streams, frame_context_t *ctx,
size_t block_len);
// Decode the literals section of a block
static size_t decode_literals(io_streams_t *streams, frame_context_t *ctx,
u8 **literals);
// Decode the sequences part of a block
static size_t decode_sequences(frame_context_t *ctx, const u8 *src,
size_t src_len, sequence_command_t **sequences);
// Execute the decoded sequences on the literals block
static size_t execute_sequences(io_streams_t *streams, frame_context_t *ctx,
sequence_command_t *sequences,
size_t num_sequences, const u8 *literals,
size_t literals_len);
// Parse a provided dictionary blob for use in decompression
static void parse_dictionary(dictionary_t *dict, const u8 *src, size_t src_len);
static void free_dictionary(dictionary_t *dict);
/******* END ZSTD HELPER STRUCTS AND PROTOTYPES *******************************/
size_t ZSTD_decompress(void *dst, size_t dst_len, const void *src,
size_t src_len) {
return ZSTD_decompress_with_dict(dst, dst_len, src, src_len, NULL, 0);
}
size_t ZSTD_decompress_usingDict(void *_ctx, void *dst, size_t dst_len,
const void *src, size_t src_len,
const void *dict, size_t dict_len) {
// _ctx needed to match ZSTD lib signature
return ZSTD_decompress_with_dict(dst, dst_len, src, src_len, dict,
dict_len);
}
size_t ZSTD_decompress_with_dict(void *dst, size_t dst_len, const void *src,
size_t src_len, const void *dict,
size_t dict_len) {
dictionary_t parsed_dict;
memset(&parsed_dict, 0, sizeof(dictionary_t));
// dict_len < 8 is not a valid dictionary
if (dict && dict_len > 8) {
parse_dictionary(&parsed_dict, (const u8 *)dict, dict_len);
}
io_streams_t streams = {(u8 *)dst, dst_len, (const u8 *)src, src_len};
while (streams.src_len > 0) {
decode_frame(&streams, &parsed_dict);
}
free_dictionary(&parsed_dict);
return streams.dst - (u8 *)dst;
}
/******* FRAME DECODING ******************************************************/
static void decode_data_frame(io_streams_t *streams, dictionary_t *dict);
static void init_frame_context(frame_context_t *context);
static void free_frame_context(frame_context_t *context);
static void parse_frame_header(io_streams_t *streams, frame_context_t *ctx,
dictionary_t *dict);
static void frame_context_apply_dict(frame_context_t *ctx, dictionary_t *dict);
static void decompress_data(io_streams_t *streams, frame_context_t *ctx);
static void decode_frame(io_streams_t *streams, dictionary_t *dict) {
if (streams->src_len < 4) {
INP_SIZE();
}
u32 magic_number = read_bits_LE(streams->src, 32, 0);
streams->src += 4;
streams->src_len -= 4;
if (magic_number >= 0x184D2A50U && magic_number <= 0x184D2A5F) {
// skippable frame
if (streams->src_len < 4) {
INP_SIZE();
}
size_t frame_size = read_bits_LE(streams->src, 32, 32);
if (streams->src_len < 4 + frame_size) {
INP_SIZE();
}
// skip over frame
streams->src += 4 + frame_size;
streams->src_len -= 4 + frame_size;
} else if (magic_number == 0xFD2FB528U) {
// ZSTD frame
decode_data_frame(streams, dict);
} else {
// not a real frame
ERROR("Invalid magic number");
}
}
/// Decode a frame that contains compressed data. Not all frames do as there
/// are skippable frames.
/// See
/// https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md#general-structure-of-zstandard-frame-format
static void decode_data_frame(io_streams_t *streams, dictionary_t *dict) {
frame_context_t ctx;
// Initialize the context that needs to be carried from block to block
init_frame_context(&ctx);
parse_frame_header(streams, &ctx, dict);
frame_context_apply_dict(&ctx, dict);
if (ctx.frame_content_size != 0 &&
ctx.frame_content_size > streams->dst_len) {
OUT_SIZE();
}
decompress_data(streams, &ctx);
free_frame_context(&ctx);
}
static void init_frame_context(frame_context_t *context) {
memset(context, 0x00, sizeof(frame_context_t));
// Set up the offset history for the repeat offset commands
context->previous_offsets[1] = 1;
context->previous_offsets[2] = 4;
context->previous_offsets[3] = 8;
}
static void free_frame_context(frame_context_t *context) {
HUF_free_dtable(&context->literals_dtable);
FSE_free_dtable(&context->ll_dtable);
FSE_free_dtable(&context->ml_dtable);
FSE_free_dtable(&context->of_dtable);
cbuf_free(&context->window);
memset(context, 0, sizeof(frame_context_t));
}
static void parse_frame_header(io_streams_t *streams, frame_context_t *ctx,
dictionary_t *dict) {
if (streams->src_len < 1) {
INP_SIZE();
}
u8 descriptor = read_bits_LE(streams->src, 8, 0);
// decode frame header descriptor into flags
u8 frame_content_size_flag = descriptor >> 6;
u8 single_segment_flag = (descriptor >> 5) & 1;
u8 reserved_bit = (descriptor >> 3) & 1;
u8 content_checksum_flag = (descriptor >> 2) & 1;
u8 dictionary_id_flag = descriptor & 3;
if (reserved_bit != 0) {
CORRUPTION();
}
streams->src++;
streams->src_len--;
ctx->single_segment_flag = single_segment_flag;
ctx->content_checksum_flag = content_checksum_flag;
// decode window size
if (!single_segment_flag) {
if (streams->src_len < 1) {
INP_SIZE();
}
// Use the algorithm from the specification to compute window size
// https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md#window_descriptor
u8 window_descriptor = read_bits_LE(streams->src, 8, 0);
u8 exponent = window_descriptor >> 3;
u8 mantissa = window_descriptor & 7;
size_t window_base = (size_t)1 << (10 + exponent);
size_t window_add = (window_base / 8) * mantissa;
ctx->window_size = window_base + window_add;
streams->src++;
streams->src_len--;
}
// decode dictionary id if it exists
if (dictionary_id_flag) {
const int bytes_array[] = {0, 1, 2, 4};
const int bytes = bytes_array[dictionary_id_flag];
if (streams->src_len < bytes) {
INP_SIZE();
}
ctx->dictionary_id = read_bits_LE(streams->src, bytes * 8, 0);
streams->src += bytes;
streams->src_len -= bytes;
} else {
ctx->dictionary_id = 0;
}
// decode frame content size if it exists
if (single_segment_flag || frame_content_size_flag) {
// if frame_content_size_flag == 0 but single_segment_flag is set, we
// still
// have a 1 byte field
const int bytes_array[] = {1, 2, 4, 8};
const int bytes = bytes_array[frame_content_size_flag];
if (streams->src_len < bytes) {
INP_SIZE();
}
ctx->frame_content_size = read_bits_LE(streams->src, bytes * 8, 0);
if (bytes == 2) {
ctx->frame_content_size += 256;
}
streams->src += bytes;
streams->src_len -= bytes;
}
if (single_segment_flag) {
ctx->window_size =
ctx->frame_content_size + (dict ? dict->content_size : 0);
// We need to allocate a buffer to write to of size at least output +
// dict
// size
size_t size = ctx->frame_content_size + (dict ? dict->content_size : 0);
}
// Allocate the window
if (ctx->window_size > MAX_WINDOW_SIZE) {
ERROR("Requested window size too large");
}
cbuf_init(&ctx->window, ctx->window_size);
}
/// A dictionary acts as initializing values for the frame context before
/// decompression, so we implement it by applying it's predetermined
/// tables and content to the context before beginning decompression
static void frame_context_apply_dict(frame_context_t *ctx, dictionary_t *dict) {
// If the content pointer is NULL then it must be an empty dict
if (!dict || !dict->content)
return;
if (ctx->dictionary_id == 0 && dict->dictionary_id != 0) {
// The dictionary is unneeded, and shouldn't be used as it may interfere
// with the default offset history
return;
}
// If the dictionary id is 0, it doesn't matter if we provide the wrong raw
// content dict, it won't change anything
if (ctx->dictionary_id != 0 && ctx->dictionary_id != dict->dictionary_id) {
ERROR("Wrong/no dictionary provided");
}
// Write the dict data in, and then flush to NULL so it's not sent to the
// output stream
cbuf_write_data_full(&ctx->window, dict->content, dict->content_size, NULL,
-1);
cbuf_flush(&ctx->window, NULL, -1);
ctx->current_total_output = dict->content_size;
// If it's a formatted dict copy the precomputed tables in so they can
// be used in the table repeat modes
if (dict->dictionary_id != 0) {
// Deep copy the entropy tables so they can be freed independently of
// the
// dictionary struct
HUF_copy_dtable(&ctx->literals_dtable, &dict->literals_dtable);
FSE_copy_dtable(&ctx->ll_dtable, &dict->ll_dtable);
FSE_copy_dtable(&ctx->of_dtable, &dict->of_dtable);
FSE_copy_dtable(&ctx->ml_dtable, &dict->ml_dtable);
memcpy(ctx->previous_offsets, dict->previous_offsets,
sizeof(ctx->previous_offsets));
}
}
/// Decompress the data from a frame block by block
static void decompress_data(io_streams_t *streams, frame_context_t *ctx) {
u8 last_block = 0;
do {
if (streams->src_len < 3) {
INP_SIZE();
}
// Parse the block header
last_block = streams->src[0] & 1;
u8 block_type = (streams->src[0] >> 1) & 3;
size_t block_len = read_bits_LE(streams->src, 21, 3);
streams->src += 3;
streams->src_len -= 3;
switch (block_type) {
case 0: {
// Raw, uncompressed block
if (streams->src_len < block_len) {
INP_SIZE();
}
if (streams->dst_len < block_len) {
OUT_SIZE();
}
// Write the raw data into the window buffer
size_t written =
cbuf_write_data_full(&ctx->window, streams->src, block_len,
streams->dst, streams->dst_len);
streams->src += block_len;
streams->src_len -= block_len;
streams->dst += written;
streams->dst_len -= written;
break;
}
case 1: {
// RLE block, repeat the first byte N times
if (streams->src_len < 1) {
INP_SIZE();
}
if (streams->dst_len < block_len) {
OUT_SIZE();
}
// Write streams->src[0] into the buffer block_len times
size_t written =
cbuf_repeat_byte_full(&ctx->window, streams->src[0], block_len,
streams->dst, streams->dst_len);
streams->dst += written;
streams->dst_len -= written;
streams->src += 1;
streams->src_len -= 1;
break;
}
case 2:
// Compressed block, this is mode complex
decompress_block(streams, ctx, block_len);
break;
}
} while (!last_block);
// Flush out anything left in the window buffer to the destination stream
size_t written = cbuf_flush(&ctx->window, streams->dst, streams->dst_len);
streams->dst += written;
streams->dst_len -= written;
if (ctx->content_checksum_flag) {
// This program does not support checking the checksum, so skip over it
// if
// it's present
if (streams->src_len < 4) {
INP_SIZE();
}
streams->src += 4;
streams->src_len -= 4;
}
}
/******* END FRAME DECODING ***************************************************/
/******* BLOCK DECOMPRESSION **************************************************/
static void decompress_block(io_streams_t *streams, frame_context_t *ctx,
size_t block_len) {
if (streams->src_len < block_len) {
INP_SIZE();
}
// We need this to determine how long the compressed literals block was
const u8 *const end_of_block = streams->src + block_len;
// Part 1: decode the literals block
u8 *literals = NULL;
size_t literals_size = decode_literals(streams, ctx, &literals);
// Part 2: decode the sequences block
if (streams->src > end_of_block) {
INP_SIZE();
}
size_t sequences_size = end_of_block - streams->src;
sequence_command_t *sequences = NULL;
size_t num_sequences =
decode_sequences(ctx, streams->src, sequences_size, &sequences);
streams->src += sequences_size;
streams->src_len -= sequences_size;
// Part 3: combine literals and sequence commands to generate output
execute_sequences(streams, ctx, sequences, num_sequences, literals,
literals_size);
free(literals);
free(sequences);
}
/******* END BLOCK DECOMPRESSION **********************************************/
/******* LITERALS DECODING ****************************************************/
static size_t decode_literals_simple(io_streams_t *streams, u8 **literals,
int block_type, int size_format);
static size_t decode_literals_compressed(io_streams_t *streams,
frame_context_t *ctx, u8 **literals,
int block_type, int size_format);
static size_t decode_huf_table(const u8 *src, size_t src_len,
HUF_dtable *dtable);
static size_t fse_decode_hufweights(const u8 *src, size_t src_len, u8 *weights,
int *num_symbs, size_t compressed_size);
static size_t decode_literals(io_streams_t *streams, frame_context_t *ctx,
u8 **literals) {
if (streams->src_len < 1) {
INP_SIZE();
}
// Decode literals header
int block_type = streams->src[0] & 3;
int size_format = (streams->src[0] >> 2) & 3;
if (block_type <= 1) {
// Raw or RLE literals block
return decode_literals_simple(streams, literals, block_type,
size_format);
} else {
// Huffman compressed literals
return decode_literals_compressed(streams, ctx, literals, block_type,
size_format);
}
}
/// Decodes literals blocks in raw or RLE form
static size_t decode_literals_simple(io_streams_t *streams, u8 **literals,
int block_type, int size_format) {
size_t size;
switch (size_format) {
// These cases are in the form X0
// In this case, the X bit is actually part of the size field
case 0:
case 2:
size = read_bits_LE(streams->src, 5, 3);
streams->src += 1;
streams->src_len -= 1;
break;
case 1:
if (streams->src_len < 2) {
INP_SIZE();
}
size = read_bits_LE(streams->src, 12, 4);
streams->src += 2;
streams->src_len -= 2;
break;
case 3:
if (streams->src_len < 2) {
INP_SIZE();
}
size = read_bits_LE(streams->src, 20, 4);
streams->src += 3;
streams->src_len -= 3;
break;
default:
// Impossible
size = -1;
}
if (size > MAX_LITERALS_SIZE) {
CORRUPTION();
}
*literals = malloc(size);
if (!*literals) {
BAD_ALLOC();
}
switch (block_type) {
case 0:
// Raw data
if (size > streams->src_len) {
INP_SIZE();
}
memcpy(*literals, streams->src, size);
streams->src += size;
streams->src_len -= size;
break;
case 1:
// Single repeated byte
if (1 > streams->src_len) {
INP_SIZE();
}
memset(*literals, streams->src[0], size);
streams->src += 1;
streams->src_len -= 1;
break;
}
return size;
}
/// Decodes Huffman compressed literals
static size_t decode_literals_compressed(io_streams_t *streams,
frame_context_t *ctx, u8 **literals,
int block_type, int size_format) {
size_t regenerated_size, compressed_size;
// Only size_format=0 has 1 stream, so default to 4
int num_streams = 4;
switch (size_format) {
case 0:
num_streams = 1;
// Fall through as it has the same size format
case 1:
if (streams->src_len < 3) {
INP_SIZE();
}
regenerated_size = read_bits_LE(streams->src, 10, 4);
compressed_size = read_bits_LE(streams->src, 10, 14);
streams->src += 3;
streams->src_len -= 3;
break;
case 2:
if (streams->src_len < 4) {
INP_SIZE();
}
regenerated_size = read_bits_LE(streams->src, 14, 4);
compressed_size = read_bits_LE(streams->src, 14, 18);
streams->src += 4;
streams->src_len -= 4;
break;
case 3:
if (streams->src_len < 5) {
INP_SIZE();
}
regenerated_size = read_bits_LE(streams->src, 18, 4);
compressed_size = read_bits_LE(streams->src, 18, 22);
streams->src += 5;
streams->src_len -= 5;
break;
default:
// Impossible
compressed_size = regenerated_size = -1;
}
if (regenerated_size > MAX_LITERALS_SIZE ||
compressed_size > regenerated_size) {
CORRUPTION();
}
if (compressed_size > streams->src_len) {
INP_SIZE();
}
*literals = malloc(regenerated_size);
if (!*literals) {
BAD_ALLOC();
}
if (block_type == 2) {
// Decode provided Huffman table
HUF_free_dtable(&ctx->literals_dtable);
size_t size = decode_huf_table(streams->src, compressed_size,
&ctx->literals_dtable);
streams->src += size;
streams->src_len -= size;
compressed_size -= size;
} else {
// If we're to repeat the previous Huffman table, make sure it exists
if (!ctx->literals_dtable.symbols) {
CORRUPTION();
}
}
if (num_streams == 1) {
HUF_decompress_1stream(&ctx->literals_dtable, *literals,
regenerated_size, streams->src, compressed_size);
} else {
HUF_decompress_4stream(&ctx->literals_dtable, *literals,
regenerated_size, streams->src, compressed_size);
}
streams->src += compressed_size;
streams->src_len -= compressed_size;
return regenerated_size;
}
// Decode the Huffman table description
static size_t decode_huf_table(const u8 *src, size_t src_len,
HUF_dtable *dtable) {
if (src_len < 1) {
INP_SIZE();
}
const u8 *const osrc = src;
u8 header = src[0];
u8 weights[HUF_MAX_SYMBS];
memset(weights, 0, sizeof(weights));
src++;
src_len--;
int num_symbs;
if (header >= 128) {
// Direct representation, read the weights out
num_symbs = header - 127;
size_t bytes = (num_symbs + 1) / 2;
if (bytes > src_len) {
INP_SIZE();
}
for (int i = 0; i < num_symbs; i++) {
if (i % 2 == 0) {
weights[i] = src[i / 2] >> 4;
} else {
weights[i] = src[i / 2] & 0xf;
}
}
src += bytes;
src_len -= bytes;
} else {
// The weights are FSE encoded, decode them before we can construct the
// table
size_t size =
fse_decode_hufweights(src, src_len, weights, &num_symbs, header);
src += size;
src_len -= size;
}
// Construct the table using the decoded weights
HUF_init_dtable_usingweights(dtable, weights, num_symbs);
return src - osrc;
}
static size_t fse_decode_hufweights(const u8 *src, size_t src_len, u8 *weights,
int *num_symbs, size_t compressed_size) {
const int MAX_ACCURACY_LOG = 7;
FSE_dtable dtable;
// Construct the FSE table
size_t read = FSE_decode_header(&dtable, src, src_len, MAX_ACCURACY_LOG);
if (src_len < compressed_size) {
INP_SIZE();
}
// Decode the weights
*num_symbs = FSE_decompress_interleaved2(
&dtable, weights, HUF_MAX_SYMBS, src + read, compressed_size - read);
FSE_free_dtable(&dtable);
return compressed_size;
}
/******* END LITERALS DECODING ************************************************/
/******* SEQUENCE DECODING ****************************************************/
/// The combination of FSE states needed to decode sequences
typedef struct {
u16 ll_state, of_state, ml_state;
FSE_dtable ll_table, of_table, ml_table;
} sequence_state_t;
/// Different modes to signal to decode_seq_tables what to do
typedef enum {
seq_literal_length = 0,
seq_offset = 1,
seq_match_length = 2,
} seq_part_t;
typedef enum {
seq_predefined = 0,
seq_rle = 1,
seq_fse = 2,
seq_repeat = 3,
} seq_mode_t;
/// The predefined FSE distribution tables for `seq_predefined` mode
static const i16 SEQ_LITERAL_LENGTH_DEFAULT_DIST[36] = {
4, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 2, 2,
2, 2, 2, 2, 2, 2, 2, 3, 2, 1, 1, 1, 1, 1, -1, -1, -1, -1};
static const i16 SEQ_OFFSET_DEFAULT_DIST[29] = {
1, 1, 1, 1, 1, 1, 2, 2, 2, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, -1, -1, -1, -1, -1};
static const i16 SEQ_MATCH_LENGTH_DEFAULT_DIST[53] = {
1, 4, 3, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, -1, -1, -1, -1, -1, -1, -1};
/// The sequence decoding baseline and number of additional bits to read/add
/// https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md#the-codes-for-literals-lengths-match-lengths-and-offsets
static const u32 SEQ_LITERAL_LENGTH_BASELINES[36] = {
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
12, 13, 14, 15, 16, 18, 20, 22, 24, 28, 32, 40,
48, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65538};
static const u8 SEQ_LITERAL_LENGTH_EXTRA_BITS[36] = {
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,
1, 1, 2, 2, 3, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16};
static const u32 SEQ_MATCH_LENGTH_BASELINES[53] = {
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, 37, 39, 41, 43, 47, 51, 59, 67, 83,
99, 131, 259, 515, 1027, 2051, 4099, 8195, 16387, 32771, 65539};
static const u8 SEQ_MATCH_LENGTH_EXTRA_BITS[53] = {
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1,
2, 2, 3, 3, 4, 4, 5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16};
/// Offset decoding is simpler so we just need a maximum code value
static const u8 SEQ_MAX_CODES[3] = {35, -1, 52};
static void decompress_sequences(frame_context_t *ctx, const u8 *src,
size_t src_len, sequence_command_t *sequences,
size_t num_sequences);
static sequence_command_t decode_sequence(sequence_state_t *state,
const u8 *src, i64 *offset);
static size_t decode_seq_table(const u8 *src, size_t src_len, FSE_dtable *table,
seq_part_t type, seq_mode_t mode);
static size_t decode_sequences(frame_context_t *ctx, const u8 *src,
size_t src_len, sequence_command_t **sequences) {
size_t num_sequences;
// Decode the sequence header and allocate space for the output
if (src_len < 1) {
INP_SIZE();
}
if (src[0] == 0) {
*sequences = NULL;
return 0;
} else if (src[0] < 128) {
num_sequences = src[0];
src++;
src_len--;
} else if (src[0] < 255) {
if (src_len < 2) {
INP_SIZE();
}
num_sequences = ((src[0] - 128) << 8) + src[1];
src += 2;
src_len -= 2;
} else {
if (src_len < 3) {
INP_SIZE();
}
num_sequences = src[1] + ((u64)src[2] << 8) + 0x7F00;
src += 3;
src_len -= 3;
}
*sequences = malloc(num_sequences * sizeof(sequence_command_t));
if (!*sequences) {
BAD_ALLOC();
}
decompress_sequences(ctx, src, src_len, *sequences, num_sequences);
return num_sequences;
}
/// Decompress the FSE encoded sequence commands
static void decompress_sequences(frame_context_t *ctx, const u8 *src,
size_t src_len, sequence_command_t *sequences,
size_t num_sequences) {
if (src_len < 1) {
INP_SIZE();
}
u8 compression_modes = src[0];
src++;
src_len--;
if ((compression_modes & 3) != 0) {
CORRUPTION();
}
sequence_state_t state;
size_t read;
// Update the tables we have stored in the context
read = decode_seq_table(src, src_len, &ctx->ll_dtable, seq_literal_length,
(compression_modes >> 6) & 3);
src += read;
src_len -= read;
read = decode_seq_table(src, src_len, &ctx->of_dtable, seq_offset,
(compression_modes >> 4) & 3);
src += read;
src_len -= read;
read = decode_seq_table(src, src_len, &ctx->ml_dtable, seq_match_length,
(compression_modes >> 2) & 3);
src += read;
src_len -= read;
// Check to make sure none of the tables are uninitialized
if (!ctx->ll_dtable.symbols || !ctx->of_dtable.symbols ||
!ctx->ml_dtable.symbols) {
CORRUPTION();
}
// Now use the context's tables
memcpy(&state.ll_table, &ctx->ll_dtable, sizeof(FSE_dtable));
memcpy(&state.of_table, &ctx->of_dtable, sizeof(FSE_dtable));
memcpy(&state.ml_table, &ctx->ml_dtable, sizeof(FSE_dtable));
int padding = 8 - log2inf(src[src_len - 1]);
i64 offset = src_len * 8 - padding;
FSE_init_state(&state.ll_table, &state.ll_state, src, &offset);
FSE_init_state(&state.of_table, &state.of_state, src, &offset);
FSE_init_state(&state.ml_table, &state.ml_state, src, &offset);
for (size_t i = 0; i < num_sequences; i++) {
// Decode sequences one by one
sequences[i] = decode_sequence(&state, src, &offset);
}
if (offset != 0) {
CORRUPTION();
}
// Don't free our tables so they can be used in the next block
}
// Decode a single sequence and update the state
static sequence_command_t decode_sequence(sequence_state_t *state,
const u8 *src, i64 *offset) {
// Decode symbols, but don't update states
u8 of_code = FSE_peek_symbol(&state->of_table, state->of_state);
u8 ll_code = FSE_peek_symbol(&state->ll_table, state->ll_state);
u8 ml_code = FSE_peek_symbol(&state->ml_table, state->ml_state);
// Offset doesn't need a max value as it's not decoded using a table
if (ll_code > SEQ_MAX_CODES[seq_literal_length] ||
ml_code > SEQ_MAX_CODES[seq_match_length]) {
CORRUPTION();
}
// Read the interleaved bits
sequence_command_t seq;
// Offset computation works differently
seq.offset = ((u32)1 << of_code) + STREAM_read_bits(src, of_code, offset);
seq.match_length =
SEQ_MATCH_LENGTH_BASELINES[ml_code] +
STREAM_read_bits(src, SEQ_MATCH_LENGTH_EXTRA_BITS[ml_code], offset);
seq.literal_length =
SEQ_LITERAL_LENGTH_BASELINES[ll_code] +
STREAM_read_bits(src, SEQ_LITERAL_LENGTH_EXTRA_BITS[ll_code], offset);
// If the stream is complete don't read bits to update state
if (*offset != 0) {
// Update state in the order specified in the specification
FSE_update_state(&state->ll_table, &state->ll_state, src, offset);
FSE_update_state(&state->ml_table, &state->ml_state, src, offset);
FSE_update_state(&state->of_table, &state->of_state, src, offset);
}
return seq;
}
/// Given a sequence part and table mode, decode the FSE distribution
static size_t decode_seq_table(const u8 *src, size_t src_len, FSE_dtable *table,
seq_part_t type, seq_mode_t mode) {
// Constant arrays indexed by seq_part_t
const i16 *const default_distributions[] = {SEQ_LITERAL_LENGTH_DEFAULT_DIST,
SEQ_OFFSET_DEFAULT_DIST,
SEQ_MATCH_LENGTH_DEFAULT_DIST};
const size_t default_distribution_lengths[] = {36, 29, 53};
const size_t default_distribution_accuracies[] = {6, 5, 6};
const size_t max_accuracies[] = {9, 8, 9};
if (mode != seq_repeat) {
// ree old one before overwriting
FSE_free_dtable(table);
}
switch (mode) {
case seq_predefined: {
const i16 *distribution = default_distributions[type];
const size_t symbs = default_distribution_lengths[type];
const size_t accuracy_log = default_distribution_accuracies[type];
FSE_init_dtable(table, distribution, symbs, accuracy_log);
return 0;
}
case seq_rle: {
if (src_len < 1) {
INP_SIZE();
}
u8 symb = src[0];
src++;
src_len--;
FSE_init_dtable_rle(table, symb);
return 1;
}
case seq_fse: {
size_t read =
FSE_decode_header(table, src, src_len, max_accuracies[type]);
src += read;
src_len -= read;
return read;
}
case seq_repeat:
// Don't have to do anything here as we're not changing the table
return 0;
default:
// Impossible, as mode is from 0-3
return -1;
}
}
/******* END SEQUENCE DECODING ************************************************/
/******* SEQUENCE EXECUTION ***************************************************/
static size_t execute_sequences(io_streams_t *streams, frame_context_t *ctx,
sequence_command_t *sequences,
size_t num_sequences, const u8 *literals,
size_t literals_len) {
u64 *offset_hist = ctx->previous_offsets;
size_t total_output = ctx->current_total_output;
for (size_t i = 0; i < num_sequences; i++) {
sequence_command_t seq = sequences[i];
if (seq.literal_length > literals_len) {
CORRUPTION();
}
{
// Copy literals to the buffer
size_t written =
cbuf_write_data_full(&ctx->window, literals, seq.literal_length,
streams->dst, streams->dst_len);
literals += seq.literal_length;
literals_len -= seq.literal_length;
streams->dst += written;
streams->dst_len -= written;
total_output += seq.literal_length;
}
size_t offset;
// Offsets are special, we need to handle the repeat offsets
if (seq.offset <= 3) {
u32 idx = seq.offset;
if (seq.literal_length == 0) {
// Special case when literal length is 0
idx++;
}
if (idx == 1) {
offset = offset_hist[1];
} else {
// If idx == 4 then literal length was 0 and the offset was 3
offset = idx < 4 ? offset_hist[idx] : offset_hist[1] - 1;
// If idx == 2 we don't need to modify offset_hist[3]
if (idx > 2) {
offset_hist[3] = offset_hist[2];
}
offset_hist[2] = offset_hist[1];
offset_hist[1] = offset;
}
} else {
offset = seq.offset - 3;
// Shift back history
offset_hist[3] = offset_hist[2];
offset_hist[2] = offset_hist[1];
offset_hist[1] = offset;
}
if (offset > total_output) {
CORRUPTION();
}
{
// Do the offset copy operation
size_t written =
cbuf_copy_offset_full(&ctx->window, offset, seq.match_length,
streams->dst, streams->dst_len);
streams->dst += written;
streams->dst_len -= written;
total_output += seq.match_length;
}
}
{
// Copy any leftover literal bytes
size_t written =
cbuf_write_data_full(&ctx->window, literals, literals_len,
streams->dst, streams->dst_len);
streams->dst += written;
streams->dst_len -= written;
total_output += literals_len;
}
ctx->current_total_output = total_output;
return total_output;
}
/******* END SEQUENCE EXECUTION ***********************************************/
/******* DICTIONARY PARSING ***************************************************/
static void init_raw_content_dict(dictionary_t *dict, const u8 *src,
size_t src_len);
static void parse_dictionary(dictionary_t *dict, const u8 *src,
size_t src_len) {
memset(dict, 0, sizeof(dictionary_t));
if (src_len < 8) {
INP_SIZE();
}
u32 magic_number = read_bits_LE(src, 32, 0);
if (magic_number != 0xEC30A437) {
// raw content dict
init_raw_content_dict(dict, src, src_len);
return;
}
dict->dictionary_id = read_bits_LE(src, 32, 32);
src += 8;
src_len -= 8;
// Parse the provided entropy tables in order
{
size_t read = decode_huf_table(src, src_len, &dict->literals_dtable);
src += read;
src_len -= read;
}
{
size_t read = decode_seq_table(src, src_len, &dict->of_dtable,
seq_offset, seq_fse);
src += read;
src_len -= read;
}
{
size_t read = decode_seq_table(src, src_len, &dict->ml_dtable,
seq_match_length, seq_fse);
src += read;
src_len -= read;
}
{
size_t read = decode_seq_table(src, src_len, &dict->ll_dtable,
seq_literal_length, seq_fse);
src += read;
src_len -= read;
}
if (src_len < 12) {
INP_SIZE();
}
// Read in the previous offset history
dict->previous_offsets[1] = read_bits_LE(src, 32, 0);
dict->previous_offsets[2] = read_bits_LE(src, 32, 32);
dict->previous_offsets[3] = read_bits_LE(src, 32, 64);
src += 12;
src_len -= 12;
// Ensure the provided offsets aren't too large
for (int i = 1; i <= 3; i++) {
if (dict->previous_offsets[i] > src_len) {
ERROR("Dictionary corrupted");
}
}
// The rest is the content
dict->content = malloc(src_len);
if (!dict->content) {
BAD_ALLOC();
}
dict->content_size = src_len;
memcpy(dict->content, src, src_len);
}
/// If parse_dictionary is given a raw content dictionary, it delegates here
static void init_raw_content_dict(dictionary_t *dict, const u8 *src,
size_t src_len) {
dict->dictionary_id = 0;
// Copy in the content
dict->content = malloc(src_len);
if (!dict->content) {
BAD_ALLOC();
}
dict->content_size = src_len;
memcpy(dict->content, src, src_len);
}
/// Free an allocated dictionary
static void free_dictionary(dictionary_t *dict) {
HUF_free_dtable(&dict->literals_dtable);
FSE_free_dtable(&dict->ll_dtable);
FSE_free_dtable(&dict->of_dtable);
FSE_free_dtable(&dict->ml_dtable);
free(dict->content);
memset(dict, 0, sizeof(dictionary_t));
}
/******* END DICTIONARY PARSING ***********************************************/
/******* CIRCULAR BUFFER ******************************************************/
static void cbuf_init(cbuf_t *buf, size_t size) {
buf->ptr = malloc(size);
if (!buf->ptr) {
BAD_ALLOC();
}
memset(buf->ptr, 0x3f, size);
buf->size = size;
buf->idx = 0;
buf->last_flush = 0;
}
static size_t cbuf_write_data(cbuf_t *buf, const u8 *src, size_t src_len) {
if (buf->size == 0 && src_len > 0) {
CORRUPTION();
}
size_t max_len = buf->size - buf->idx;
size_t len = MIN(src_len, max_len);
memcpy(buf->ptr + buf->idx, src, len);
buf->idx += len;
return len;
}
static size_t cbuf_write_data_full(cbuf_t *buf, const u8 *src, size_t src_len,
u8 *out, size_t out_len) {
size_t written = 0;
size_t flushed = 0;
while (1) {
written += cbuf_write_data(buf, src + written, src_len - written);
if (written == src_len) {
break;
} else {
flushed += cbuf_flush(buf, out + flushed, out_len - flushed);
}
}
return flushed;
}
static size_t cbuf_copy_offset(cbuf_t *buf, size_t offset, size_t len) {
if (buf->size == 0 && len > 0) {
CORRUPTION();
}
if (offset > buf->size) {
CORRUPTION();
}
size_t max_len = buf->size - buf->idx;
len = MIN(len, max_len);
size_t read_off = (buf->idx + buf->size - offset) % buf->size;
for (size_t i = 0; i < len; i++) {
buf->ptr[buf->idx++] = buf->ptr[read_off++];
if (read_off == buf->size) {
read_off = 0;
}
}
return len;
}
static size_t cbuf_copy_offset_full(cbuf_t *buf, size_t offset, size_t len,
u8 *out, size_t out_len) {
size_t written = 0;
size_t flushed = 0;
while (1) {
written += cbuf_copy_offset(buf, offset, len - written);
if (written == len) {
break;
} else {
flushed += cbuf_flush(buf, out + flushed, out_len - flushed);
}
}
return flushed;
}
static size_t cbuf_repeat_byte(cbuf_t *buf, u8 byte, size_t len) {
if (buf->size == 0 && len > 0) {
CORRUPTION();
}
size_t max_len = buf->size - buf->idx;
len = MIN(len, max_len);
memset(buf->ptr + buf->idx, byte, len);
return len;
}
static size_t cbuf_repeat_byte_full(cbuf_t *buf, u8 byte, size_t len, u8 *out,
size_t out_len) {
size_t written = 0;
size_t flushed = 0;
while (1) {
written += cbuf_repeat_byte(buf, byte, len - written);
if (written == len) {
break;
} else {
flushed += cbuf_flush(buf, out + flushed, out_len - flushed);
}
}
return flushed;
}
static size_t cbuf_flush(cbuf_t *buf, u8 *dst, size_t dst_len) {
if (buf->idx < buf->last_flush) {
CORRUPTION();
}
size_t len = buf->idx - buf->last_flush;
if (dst && len > dst_len) {
OUT_SIZE();
}
// allow for NULL buffers to indicate flushing to nowhere
if (dst) {
memcpy(dst, buf->ptr + buf->last_flush, len);
}
// we could have a 0 size buffer
if (buf->size) {
buf->idx = buf->idx % buf->size;
}
buf->last_flush = buf->idx;
return len;
}
static void cbuf_free(cbuf_t *buf) {
free(buf->ptr);
memset(buf, 0, sizeof(cbuf_t));
}
/******* END CIRCULAR BUFFER **************************************************/
/******* BITSTREAM OPERATIONS *************************************************/
static inline u64 read_bits_LE(const u8 *src, int num, size_t offset) {
if (num > 64) {
return -1;
}
src += offset / 8;
offset %= 8;
u64 res = 0;
int shift = 0;
int left = num;
while (left > 0) {
u64 mask = left >= 8 ? 0xff : (((u64)1 << left) - 1);
res += (((u64)*src++ >> offset) & mask) << shift;
shift += 8 - offset;
left -= 8 - offset;
offset = 0;
}
return res;
}
static inline u64 STREAM_read_bits(const u8 *src, int bits, i64 *offset) {
*offset = *offset - bits;
size_t actual_off = *offset;
if (*offset < 0) {
bits += *offset;
actual_off = 0;
}
u64 res = read_bits_LE(src, bits, actual_off);
if (*offset < 0) {
// Fill in the bottom "overflowed" bits with 0's
res = -*offset >= 64 ? 0 : (res << -*offset);
}
return res;
}
/******* END BITSTREAM OPERATIONS *********************************************/
/******* BIT COUNTING OPERATIONS **********************************************/
static inline int log2sup(u64 num) {
for (int i = 0; i < 64; i++) {
if (((u64)1 << i) >= num) {
return i;
}
}
return -1;
}
static inline int log2inf(u64 num) {
for (int i = 63; i >= 0; i--) {
if (((u64)1 << i) <= num) {
return i;
}
}
return -1;
}
/******* END BIT COUNTING OPERATIONS ******************************************/
/******* HUFFMAN PRIMITIVES ***************************************************/
static inline u8 HUF_decode_symbol(HUF_dtable *dtable, u16 *state,
const u8 *src, i64 *offset) {
// Look up the symbol and number of bits to read
const u8 symb = dtable->symbols[*state];
const u8 bits = dtable->num_bits[*state];
const u16 rest = STREAM_read_bits(src, bits, offset);
*state = ((*state << bits) + rest) & (((u16)1 << dtable->max_bits) - 1);
return symb;
}
static inline void HUF_init_state(HUF_dtable *dtable, u16 *state, const u8 *src,
i64 *offset) {
// Read in a full dtable->max_bits to initialize the state
const u8 bits = dtable->max_bits;
*state = STREAM_read_bits(src, bits, offset);
}
static size_t HUF_decompress_1stream(HUF_dtable *dtable, u8 *dst,
size_t dst_len, const u8 *src,
size_t src_len) {
u8 *const dst_max = dst + dst_len;
u8 *const odst = dst;
// To maintain similarity with FSE, start from the end
// Find the last 1 bit
int padding = 8 - log2inf(src[src_len - 1]);
i64 offset = src_len * 8 - padding;
u16 state;
HUF_init_state(dtable, &state, src, &offset);
while (dst < dst_max && offset > -dtable->max_bits) {
*dst++ = HUF_decode_symbol(dtable, &state, src, &offset);
}
// If we stopped before consuming all the input, we didn't have enough space
if (dst == dst_max && offset > -dtable->max_bits) {
OUT_SIZE();
}
// The current state should be the `max_bits` preceding the start as
// everything from `src` onward should be consumed
if (offset != -dtable->max_bits) {
CORRUPTION();
}
return dst - odst;
}
static size_t HUF_decompress_4stream(HUF_dtable *dtable, u8 *dst,
size_t dst_len, const u8 *src,
size_t src_len) {
// Decode each stream independently for simplicity
// If we wanted to we could decode all 4 at the same time for speed,
// utilizing
// more execution units
const u8 *src1, *src2, *src3, *src4, *src_end;
u8 *dst1, *dst2, *dst3, *dst4, *dst_end;
size_t total_out = 0;
if (src_len < 6) {
INP_SIZE();
}
src1 = src + 6;
src2 = src1 + read_bits_LE(src, 16, 0);
src3 = src2 + read_bits_LE(src, 16, 16);
src4 = src3 + read_bits_LE(src, 16, 32);
src_end = src + src_len;
// We can't test with all 4 sizes because the 4th size is a function of the
// other 3 and the provided length
if (src4 - src >= src_len) {
INP_SIZE();
}
size_t segment_size = (dst_len + 3) / 4;
dst1 = dst;
dst2 = dst1 + segment_size;
dst3 = dst2 + segment_size;
dst4 = dst3 + segment_size;
dst_end = dst + dst_len;
total_out +=
HUF_decompress_1stream(dtable, dst1, segment_size, src1, src2 - src1);
total_out +=
HUF_decompress_1stream(dtable, dst2, segment_size, src2, src3 - src2);
total_out +=
HUF_decompress_1stream(dtable, dst3, segment_size, src3, src4 - src3);
total_out += HUF_decompress_1stream(dtable, dst4, dst_end - dst4, src4,
src_end - src4);
return total_out;
}
static void HUF_init_dtable(HUF_dtable *table, u8 *bits, int num_symbs) {
memset(table, 0, sizeof(HUF_dtable));
if (num_symbs > HUF_MAX_SYMBS) {
ERROR("Too many symbols for Huffman");
}
u8 max_bits = 0;
u16 rank_count[HUF_MAX_BITS + 1];
memset(rank_count, 0, sizeof(rank_count));
// Count the number of symbols for each number of bits, and determine the
// depth of the tree
for (int i = 0; i < num_symbs; i++) {
if (bits[i] > HUF_MAX_BITS) {
ERROR("Huffman table depth too large");
}
max_bits = MAX(max_bits, bits[i]);
rank_count[bits[i]]++;
}
size_t table_size = 1 << max_bits;
table->max_bits = max_bits;
table->symbols = malloc(table_size);
table->num_bits = malloc(table_size);
if (!table->symbols || !table->num_bits) {
free(table->symbols);
free(table->num_bits);
BAD_ALLOC();
}
u32 rank_idx[HUF_MAX_BITS + 1];
// Initialize the starting codes for each rank (number of bits)
rank_idx[max_bits] = 0;
for (int i = max_bits; i >= 1; i--) {
rank_idx[i - 1] = rank_idx[i] + rank_count[i] * (1 << (max_bits - i));
// The entire range takes the same number of bits so we can memset it
memset(&table->num_bits[rank_idx[i]], i, rank_idx[i - 1] - rank_idx[i]);
}
if (rank_idx[0] != table_size) {
CORRUPTION();
}
// Allocate codes and fill in the table
for (int i = 0; i < num_symbs; i++) {
if (bits[i] != 0) {
// Allocate a code for this symbol and set its range in the table
const u16 code = rank_idx[bits[i]];
const u16 len = 1 << (max_bits - bits[i]);
memset(&table->symbols[code], i, len);
rank_idx[bits[i]] += len;
}
}
}
static void HUF_init_dtable_usingweights(HUF_dtable *table, u8 *weights,
int num_symbs) {
// +1 because the last weight is not transmitted in the header
if (num_symbs + 1 > HUF_MAX_SYMBS) {
ERROR("Too many symbols for Huffman");
}
u8 bits[HUF_MAX_SYMBS];
u64 weight_sum = 0;
for (int i = 0; i < num_symbs; i++) {
weight_sum += weights[i] > 0 ? (u64)1 << (weights[i] - 1) : 0;
}
// Find the first power of 2 larger than the sum
int max_bits = log2inf(weight_sum) + 1;
u64 left_over = ((u64)1 << max_bits) - weight_sum;
// If the left over isn't a power of 2, the weights are invalid
if (left_over & (left_over - 1)) {
CORRUPTION();
}
int last_weight = log2inf(left_over) + 1;
for (int i = 0; i < num_symbs; i++) {
bits[i] = weights[i] > 0 ? (max_bits + 1 - weights[i]) : 0;
}
bits[num_symbs] =
max_bits + 1 - last_weight; // last weight is always non-zero
HUF_init_dtable(table, bits, num_symbs + 1);
}
static void HUF_free_dtable(HUF_dtable *dtable) {
free(dtable->symbols);
free(dtable->num_bits);
memset(dtable, 0, sizeof(HUF_dtable));
}
static void HUF_copy_dtable(HUF_dtable *dst, const HUF_dtable *src) {
if (src->max_bits == 0) {
memset(dst, 0, sizeof(HUF_dtable));
return;
}
size_t size = (size_t)1 << src->max_bits;
dst->max_bits = src->max_bits;
dst->symbols = malloc(size);
dst->num_bits = malloc(size);
if (!dst->symbols || !dst->num_bits) {
BAD_ALLOC();
}
memcpy(dst->symbols, src->symbols, size);
memcpy(dst->num_bits, src->num_bits, size);
}
/******* END HUFFMAN PRIMITIVES ***********************************************/
/******* FSE PRIMITIVES *******************************************************/
static inline u8 FSE_peek_symbol(FSE_dtable *dtable, u16 state) {
return dtable->symbols[state];
}
static inline void FSE_update_state(FSE_dtable *dtable, u16 *state,
const u8 *src, i64 *offset) {
const u8 bits = dtable->num_bits[*state];
const u16 rest = STREAM_read_bits(src, bits, offset);
*state = dtable->new_state_base[*state] + rest;
}
// Decodes a single FSE symbol and updates the offset
static inline u8 FSE_decode_symbol(FSE_dtable *dtable, u16 *state,
const u8 *src, i64 *offset) {
const u8 symb = FSE_peek_symbol(dtable, *state);
FSE_update_state(dtable, state, src, offset);
return symb;
}
static inline void FSE_init_state(FSE_dtable *dtable, u16 *state, const u8 *src,
i64 *offset) {
const u8 bits = dtable->accuracy_log;
*state = STREAM_read_bits(src, bits, offset);
}
static size_t FSE_decompress_interleaved2(FSE_dtable *dtable, u8 *dst,
size_t dst_len, const u8 *src,
size_t src_len) {
if (src_len == 0) {
INP_SIZE();
}
u8 *dst_max = dst + dst_len;
u8 *const odst = dst;
// Find the last 1 bit
int padding = 8 - log2inf(src[src_len - 1]);
i64 offset = src_len * 8 - padding;
u16 state1, state2;
FSE_init_state(dtable, &state1, src, &offset);
FSE_init_state(dtable, &state2, src, &offset);
// Decode until we overflow the stream
// Since we decode in reverse order, overflowing the stream is offset going
// negative
while (1) {
if (dst > dst_max - 2) {
OUT_SIZE();
}
*dst++ = FSE_decode_symbol(dtable, &state1, src, &offset);
if (offset < 0) {
// There's still a symbol to decode in state2
*dst++ = FSE_decode_symbol(dtable, &state2, src, &offset);
break;
}
if (dst > dst_max - 2) {
OUT_SIZE();
}
*dst++ = FSE_decode_symbol(dtable, &state2, src, &offset);
if (offset < 0) {
// There's still a symbol to decode in state1
*dst++ = FSE_decode_symbol(dtable, &state1, src, &offset);
break;
}
}
// number of symbols read
return dst - odst;
}
static void FSE_init_dtable(FSE_dtable *dtable, const i16 *norm_freqs,
int num_symbs, int accuracy_log) {
if (accuracy_log > FSE_MAX_ACCURACY_LOG) {
ERROR("FSE accuracy too large");
}
if (num_symbs > FSE_MAX_SYMBS) {
ERROR("Too many symbols for FSE");
}
dtable->accuracy_log = accuracy_log;
size_t size = (size_t)1 << accuracy_log;
dtable->symbols = malloc(size * sizeof(u8));
dtable->num_bits = malloc(size * sizeof(u8));
dtable->new_state_base = malloc(size * sizeof(u16));
// Used to determine how many bits need to be read for each state,
// and where the destination range should start
// Needs to be u16 because max value is 2 * max number of symbols,
// which can be larger than a byte can store
u16 state_desc[FSE_MAX_SYMBS];
int high_threshold = size;
for (int s = 0; s < num_symbs; s++) {
// Scan for low probability symbols to put at the top
if (norm_freqs[s] == -1) {
dtable->symbols[--high_threshold] = s;
state_desc[s] = 1;
}
}
// Place the rest in the table
u16 step = (size >> 1) + (size >> 3) + 3;
u16 mask = size - 1;
u16 pos = 0;
for (int s = 0; s < num_symbs; s++) {
if (norm_freqs[s] <= 0) {
continue;
}
state_desc[s] = norm_freqs[s];
for (int i = 0; i < norm_freqs[s]; i++) {
dtable->symbols[pos] = s;
do {
pos = (pos + step) & mask;
} while (pos >=
high_threshold); // Make sure we don't occupy a spot taken
// by the low prob symbols
// Note: no other collision checking is necessary as `step` is
// coprime to
// `size`, so the cycle will visit each position exactly once
}
}
if (pos != 0) {
CORRUPTION();
}
// Now we can fill baseline and num bits
for (int i = 0; i < size; i++) {
u8 symbol = dtable->symbols[i];
u16 next_state_desc = state_desc[symbol]++;
// Fills in the table appropriately
// next_state_desc increases by symbol over time, decreasing number of
// bits
dtable->num_bits[i] = (u8)(accuracy_log - log2inf(next_state_desc));
// baseline increases until the bit threshold is passed, at which point
// it
// resets to 0
dtable->new_state_base[i] =
((u16)next_state_desc << dtable->num_bits[i]) - size;
}
}
static size_t FSE_decode_header(FSE_dtable *dtable, const u8 *src,
size_t src_len, int max_accuracy_log) {
if (max_accuracy_log > FSE_MAX_ACCURACY_LOG) {
ERROR("FSE accuracy too large");
}
if (src_len < 1) {
INP_SIZE();
}
int accuracy_log = 5 + read_bits_LE(src, 4, 0);
if (accuracy_log > max_accuracy_log) {
ERROR("FSE accuracy too large");
}
// The +1 facilitates the `-1` probabilities
i32 remaining = (1 << accuracy_log) + 1;
i16 frequencies[FSE_MAX_SYMBS];
int symb = 0;
size_t offset = 4;
while (remaining > 1 && symb < FSE_MAX_SYMBS) {
int bits = log2sup(remaining +
1); // the number of possible values we could read
u16 val = read_bits_LE(src, bits, offset);
offset += bits;
// try to mask out the lower bits to see if it qualifies for the "small
// value" threshold
u16 lower_mask = ((u16)1 << (bits - 1)) - 1;
u16 threshold = ((u16)1 << bits) - 1 - remaining;
if ((val & lower_mask) < threshold) {
offset--;
val = val & lower_mask;
} else if (val > lower_mask) {
val = val - threshold;
}
i16 proba = (i16)val - 1;
// a value of -1 is possible, and has special meaning
remaining -= proba < 0 ? -proba : proba;
frequencies[symb] = proba;
symb++;
// Handle the special probability = 0 case
if (proba == 0) {
// read the next two bits to see how many more 0s
int repeat = read_bits_LE(src, 2, offset);
offset += 2;
while (1) {
for (int i = 0; i < repeat && symb < FSE_MAX_SYMBS; i++) {
frequencies[symb++] = 0;
}
if (repeat == 3) {
repeat = read_bits_LE(src, 2, offset);
offset += 2;
} else {
break;
}
}
}
}
if (remaining != 1 || symb >= FSE_MAX_SYMBS) {
CORRUPTION();
}
// Initialize the decoding table using the determined weights
FSE_init_dtable(dtable, frequencies, symb, accuracy_log);
return (offset + 7) / 8;
}
static void FSE_init_dtable_rle(FSE_dtable *dtable, u8 symb) {
dtable->symbols = malloc(sizeof(u8));
dtable->num_bits = malloc(sizeof(u8));
dtable->new_state_base = malloc(sizeof(u16));
// This setup will always have a state of 0, always return symbol `symb`,
// and
// never consume any bits
dtable->symbols[0] = symb;
dtable->num_bits[0] = 0;
dtable->new_state_base[0] = 0;
dtable->accuracy_log = 0;
}
static void FSE_free_dtable(FSE_dtable *dtable) {
free(dtable->symbols);
free(dtable->num_bits);
free(dtable->new_state_base);
memset(dtable, 0, sizeof(FSE_dtable));
}
static void FSE_copy_dtable(FSE_dtable *dst, const FSE_dtable *src) {
if (src->accuracy_log == 0) {
memset(dst, 0, sizeof(FSE_dtable));
return;
}
size_t size = (size_t)1 << src->accuracy_log;
dst->accuracy_log = src->accuracy_log;
dst->symbols = malloc(size);
dst->num_bits = malloc(size);
dst->new_state_base = malloc(size * sizeof(u16));
if (!dst->symbols || !dst->num_bits || !dst->new_state_base) {
BAD_ALLOC();
}
memcpy(dst->symbols, src->symbols, size);
memcpy(dst->num_bits, src->num_bits, size);
memcpy(dst->new_state_base, src->new_state_base, size * sizeof(u16));
}
/******* END FSE PRIMITIVES ***************************************************/