/// 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);
+size_t ZSTD_decompress(void *const dst, const size_t dst_len,
+ const void *const src, const 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);
+size_t ZSTD_decompress_with_dict(void *const dst, const size_t dst_len,
+ const void *const src, const size_t src_len,
+ const void *const dict, const size_t dict_len);
/// Get the decompressed size of an input stream so memory can be allocated in
/// advance
-size_t ZSTD_get_decompressed_size(const void *src, size_t src_len);
+size_t ZSTD_get_decompressed_size(const void *const src, const size_t src_len);
/******* UTILITY MACROS AND TYPES *********************************************/
// Max block size decompressed size is 128 KB and literal blocks must be smaller
/*** 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);
+static inline u64 read_bits_LE(const u8 *src, const int num,
+ const 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);
+static inline u64 STREAM_read_bits(const u8 *src, const int bits,
+ i64 *const 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);
+static inline int log2inf(const u64 num);
/*** END BIT COUNTING OPERATIONS ******/
/*** HUFFMAN PRIMITIVES ***************/
} 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);
+static inline u8 HUF_decode_symbol(const HUF_dtable *const dtable,
+ u16 *const state, const u8 *const src,
+ i64 *const 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);
+static inline void HUF_init_state(const HUF_dtable *const dtable,
+ u16 *const state, const u8 *const src,
+ i64 *const offset);
/// 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);
+static size_t HUF_decompress_1stream(const HUF_dtable *const dtable, u8 *dst,
+ const 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);
+static size_t HUF_decompress_4stream(const HUF_dtable *const dtable, u8 *dst,
+ const size_t dst_len, const u8 *const src,
+ const size_t src_len);
+
+/// Initialize a Huffman decoding table using the table of bit counts provided
+static void HUF_init_dtable(HUF_dtable *const table, const u8 *const bits,
+ const 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 *const table,
+ const u8 *const weights,
+ const int num_symbs);
/// Free the malloc'ed parts of a decoding table
-static void HUF_free_dtable(HUF_dtable *dtable);
+static void HUF_free_dtable(HUF_dtable *const 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);
+static void HUF_copy_dtable(HUF_dtable *const dst, const HUF_dtable *const src);
/*** END HUFFMAN PRIMITIVES ***********/
/*** FSE PRIMITIVES *******************/
} FSE_dtable;
/// Return the symbol for the current state
-static inline u8 FSE_peek_symbol(FSE_dtable *dtable, u16 state);
+static inline u8 FSE_peek_symbol(const FSE_dtable *const dtable,
+ const 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);
+static inline void FSE_update_state(const FSE_dtable *const dtable,
+ u16 *const state, const u8 *const src,
+ i64 *const 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);
+static inline u8 FSE_decode_symbol(const FSE_dtable *const dtable,
+ u16 *const state, const u8 *const src,
+ i64 *const 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);
+static inline void FSE_init_state(const FSE_dtable *const dtable,
+ u16 *const state, const u8 *const src,
+ i64 *const 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);
+static size_t FSE_decompress_interleaved2(const FSE_dtable *const dtable,
+ u8 *dst, const size_t dst_len,
+ const u8 *const src,
+ const 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);
+static void FSE_init_dtable(FSE_dtable *const dtable,
+ const i16 *const norm_freqs, const int num_symbs,
+ const 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);
+static size_t FSE_decode_header(FSE_dtable *const dtable, const u8 *const src,
+ const size_t src_len,
+ const 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);
+static void FSE_init_dtable_rle(FSE_dtable *const dtable, const u8 symb);
/// Free the malloc'ed parts of a decoding table
-static void FSE_free_dtable(FSE_dtable *dtable);
+static void FSE_free_dtable(FSE_dtable *const 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);
+static void FSE_copy_dtable(FSE_dtable *const dst, const FSE_dtable *const src);
/*** END FSE PRIMITIVES ***************/
/******* END IMPLEMENTATION PRIMITIVE PROTOTYPES ******************************/
/// 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);
+static void decode_frame(io_streams_t *const streams,
+ const dictionary_t *const dict);
// Decode data in a compressed block
-static void decompress_block(io_streams_t *streams, frame_context_t *ctx,
- size_t block_len);
+static void decompress_block(io_streams_t *const streams,
+ frame_context_t *const ctx,
+ const 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);
+static size_t decode_literals(io_streams_t *const streams,
+ frame_context_t *const ctx, u8 **const 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);
+static size_t decode_sequences(frame_context_t *const ctx, const u8 *const src,
+ const size_t src_len,
+ sequence_command_t **const 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);
+static void execute_sequences(io_streams_t *const streams,
+ frame_context_t *const ctx,
+ const sequence_command_t *const sequences,
+ const 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);
+static void parse_dictionary(dictionary_t *const dict, const u8 *const src,
+ const size_t src_len);
+static void free_dictionary(dictionary_t *const dict);
/******* END ZSTD HELPER STRUCTS AND PROTOTYPES *******************************/
-size_t ZSTD_decompress(void *dst, size_t dst_len, const void *src,
- size_t src_len) {
+size_t ZSTD_decompress(void *const dst, const size_t dst_len,
+ const void *const src, const 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) {
+size_t ZSTD_decompress_with_dict(void *const dst, const size_t dst_len,
+ const void *const src, const size_t src_len,
+ const void *const dict,
+ const size_t dict_len) {
dictionary_t parsed_dict;
memset(&parsed_dict, 0, sizeof(dictionary_t));
// dict_len < 8 is not a valid dictionary
/******* FRAME DECODING ******************************************************/
-static void decode_data_frame(io_streams_t *streams, dictionary_t *dict);
-static void init_frame_context(io_streams_t *streams, frame_context_t *context,
- dictionary_t *dict);
-static void free_frame_context(frame_context_t *context);
-static void parse_frame_header(frame_header_t *header, const u8 *src,
- size_t src_len);
-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) {
+static void decode_data_frame(io_streams_t *const streams,
+ const dictionary_t *const dict);
+static void init_frame_context(io_streams_t *const streams,
+ frame_context_t *const context,
+ const dictionary_t *const dict);
+static void free_frame_context(frame_context_t *const context);
+static void parse_frame_header(frame_header_t *const header,
+ const u8 *const src, const size_t src_len);
+static void frame_context_apply_dict(frame_context_t *const ctx,
+ const dictionary_t *const dict);
+
+static void decompress_data(io_streams_t *const streams,
+ frame_context_t *const ctx);
+
+static void decode_frame(io_streams_t *const streams,
+ const dictionary_t *const dict) {
if (streams->src_len < 4) {
INP_SIZE();
}
- u32 magic_number = read_bits_LE(streams->src, 32, 0);
+ const u32 magic_number = read_bits_LE(streams->src, 32, 0);
streams->src += 4;
streams->src_len -= 4;
if (streams->src_len < 4) {
INP_SIZE();
}
- size_t frame_size = read_bits_LE(streams->src, 32, 32);
+ const size_t frame_size = read_bits_LE(streams->src, 32, 32);
if (streams->src_len < 4 + frame_size) {
INP_SIZE();
/// 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) {
+static void decode_data_frame(io_streams_t *const streams,
+ const dictionary_t *const dict) {
frame_context_t ctx;
// Initialize the context that needs to be carried from block to block
/// Takes the information provided in the header and dictionary, and initializes
/// the context for this frame
-static void init_frame_context(io_streams_t *streams, frame_context_t *context,
- dictionary_t *dict) {
+static void init_frame_context(io_streams_t *const streams,
+ frame_context_t *const context,
+ const dictionary_t *const dict) {
+ // Most fields in context are correct when initialized to 0
memset(context, 0x00, sizeof(frame_context_t));
// Parse data from the frame header
frame_context_apply_dict(context, dict);
}
-static void free_frame_context(frame_context_t *context) {
+static void free_frame_context(frame_context_t *const context) {
HUF_free_dtable(&context->literals_dtable);
FSE_free_dtable(&context->ll_dtable);
memset(context, 0, sizeof(frame_context_t));
}
-static void parse_frame_header(frame_header_t *header, const u8 *src,
- size_t src_len) {
+static void parse_frame_header(frame_header_t *const header,
+ const u8 *const src, const size_t src_len) {
if (src_len < 1) {
INP_SIZE();
}
- u8 descriptor = read_bits_LE(src, 8, 0);
+ const u8 descriptor = read_bits_LE(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;
+ const u8 frame_content_size_flag = descriptor >> 6;
+ const u8 single_segment_flag = (descriptor >> 5) & 1;
+ const u8 reserved_bit = (descriptor >> 3) & 1;
+ const u8 content_checksum_flag = (descriptor >> 2) & 1;
+ const u8 dictionary_id_flag = descriptor & 3;
if (reserved_bit != 0) {
CORRUPTION();
/// 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) {
+static void frame_context_apply_dict(frame_context_t *const ctx,
+ const dictionary_t *const dict) {
// If the content pointer is NULL then it must be an empty dict
if (!dict || !dict->content)
return;
}
/// Decompress the data from a frame block by block
-static void decompress_data(io_streams_t *streams, frame_context_t *ctx) {
-
+static void decompress_data(io_streams_t *const streams,
+ frame_context_t *const ctx) {
int last_block = 0;
do {
if (streams->src_len < 3) {
}
// Parse the block header
last_block = streams->src[0] & 1;
- int block_type = (streams->src[0] >> 1) & 3;
- size_t block_len = read_bits_LE(streams->src, 21, 3);
+ const int block_type = (streams->src[0] >> 1) & 3;
+ const size_t block_len = read_bits_LE(streams->src, 21, 3);
streams->src += 3;
streams->src_len -= 3;
/******* END FRAME DECODING ***************************************************/
/******* BLOCK DECOMPRESSION **************************************************/
-static void decompress_block(io_streams_t *streams, frame_context_t *ctx,
- size_t block_len) {
+static void decompress_block(io_streams_t *const streams, frame_context_t *const ctx,
+ const size_t block_len) {
if (streams->src_len < block_len) {
INP_SIZE();
}
// Part 1: decode the literals block
u8 *literals = NULL;
- size_t literals_size = decode_literals(streams, ctx, &literals);
+ const 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;
+ const size_t sequences_size = end_of_block - streams->src;
sequence_command_t *sequences = NULL;
- size_t num_sequences =
+ const size_t num_sequences =
decode_sequences(ctx, streams->src, sequences_size, &sequences);
streams->src += sequences_size;
/******* 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_literals_simple(io_streams_t *const streams,
+ u8 **const literals, const int block_type,
+ const int size_format);
+static size_t decode_literals_compressed(io_streams_t *const streams,
+ frame_context_t *const ctx,
+ u8 **const literals,
+ const int block_type,
+ const 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);
+ HUF_dtable *const dtable);
+static size_t fse_decode_hufweights(const u8 *const src, const size_t src_len,
+ u8 *const weights, int *const num_symbs,
+ const size_t compressed_size);
-static size_t decode_literals(io_streams_t *streams, frame_context_t *ctx,
- u8 **literals) {
+static size_t decode_literals(io_streams_t *const streams,
+ frame_context_t *const ctx, u8 **const literals) {
if (streams->src_len < 1) {
INP_SIZE();
}
}
/// 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) {
+static size_t decode_literals_simple(io_streams_t *const streams,
+ u8 **const literals, const int block_type,
+ const int size_format) {
size_t size;
switch (size_format) {
// These cases are in the form X0
}
/// 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) {
+static size_t decode_literals_compressed(io_streams_t *const streams,
+ frame_context_t *const ctx,
+ u8 **const literals,
+ const int block_type,
+ const int size_format) {
size_t regenerated_size, compressed_size;
// Only size_format=0 has 1 stream, so default to 4
int num_streams = 4;
// Decode provided Huffman table
HUF_free_dtable(&ctx->literals_dtable);
- size_t size = decode_huf_table(streams->src, compressed_size,
- &ctx->literals_dtable);
+ const size_t size = decode_huf_table(streams->src, compressed_size,
+ &ctx->literals_dtable);
streams->src += size;
streams->src_len -= size;
compressed_size -= size;
// Decode the Huffman table description
static size_t decode_huf_table(const u8 *src, size_t src_len,
- HUF_dtable *dtable) {
+ HUF_dtable *const dtable) {
if (src_len < 1) {
INP_SIZE();
}
const u8 *const osrc = src;
- u8 header = src[0];
+ const u8 header = src[0];
u8 weights[HUF_MAX_SYMBS];
memset(weights, 0, sizeof(weights));
if (header >= 128) {
// Direct representation, read the weights out
num_symbs = header - 127;
- size_t bytes = (num_symbs + 1) / 2;
+ const size_t bytes = (num_symbs + 1) / 2;
if (bytes > src_len) {
INP_SIZE();
}
for (int i = 0; i < num_symbs; i++) {
+ // read_bits_LE isn't applicable here because the weights are order
+ // reversed within each byte
+ // https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md#huffman-tree-header
if (i % 2 == 0) {
weights[i] = src[i / 2] >> 4;
} else {
} else {
// The weights are FSE encoded, decode them before we can construct the
// table
- size_t size =
+ const size_t size =
fse_decode_hufweights(src, src_len, weights, &num_symbs, header);
src += size;
src_len -= size;
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) {
+static size_t fse_decode_hufweights(const u8 *const src, const size_t src_len,
+ u8 *const weights, int *const num_symbs,
+ const 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);
+ const size_t read =
+ FSE_decode_header(&dtable, src, src_len, MAX_ACCURACY_LOG);
if (src_len < compressed_size) {
INP_SIZE();
/// 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) {
+static void decompress_sequences(frame_context_t *const ctx, const u8 *src,
+ size_t src_len,
+ sequence_command_t *const sequences,
+ const size_t num_sequences);
+static sequence_command_t decode_sequence(sequence_state_t *const state,
+ const u8 *const src,
+ i64 *const offset);
+static size_t decode_seq_table(const u8 *src, size_t src_len,
+ FSE_dtable *const table, const seq_part_t type,
+ const seq_mode_t mode);
+
+static size_t decode_sequences(frame_context_t *const ctx, const u8 *src,
+ size_t src_len,
+ sequence_command_t **const sequences) {
size_t num_sequences;
// Decode the sequence header and allocate space for the output
}
/// 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) {
+static void decompress_sequences(frame_context_t *const ctx, const u8 *src,
+ size_t src_len,
+ sequence_command_t *const sequences,
+ const size_t num_sequences) {
if (src_len < 1) {
INP_SIZE();
}
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;
+ {
+ 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;
+ }
+
+ {
+ const size_t read =
+ decode_seq_table(src, src_len, &ctx->of_dtable, seq_offset,
+ (compression_modes >> 4) & 3);
+ src += read;
+ src_len -= read;
+ }
+
+ {
+ const size_t 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 ||
CORRUPTION();
}
- // Now use the context's tables
+ sequence_state_t state;
+ // Copy the context's tables into the local state
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]);
+ const 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);
}
// Decode a single sequence and update the state
-static sequence_command_t decode_sequence(sequence_state_t *state,
- const u8 *src, i64 *offset) {
+static sequence_command_t decode_sequence(sequence_state_t *const state,
+ const u8 *const src,
+ i64 *const 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);
+ const u8 of_code = FSE_peek_symbol(&state->of_table, state->of_state);
+ const u8 ll_code = FSE_peek_symbol(&state->ll_table, state->ll_state);
+ const 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] ||
}
/// 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) {
-
+static size_t decode_seq_table(const u8 *src, size_t src_len,
+ FSE_dtable *const table, const seq_part_t type,
+ const 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,
if (src_len < 1) {
INP_SIZE();
}
- u8 symb = src[0];
+ const u8 symb = src[0];
src++;
src_len--;
FSE_init_dtable_rle(table, symb);
/******* 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;
+static void execute_sequences(io_streams_t *const streams,
+ frame_context_t *const ctx,
+ const sequence_command_t *const sequences,
+ const size_t num_sequences,
+ const u8 *literals,
+ size_t literals_len) {
+ u64 *const 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];
+ const sequence_command_t seq = sequences[i];
if (seq.literal_length > literals_len) {
CORRUPTION();
/******* END SEQUENCE EXECUTION ***********************************************/
/******* OUTPUT SIZE COUNTING *************************************************/
-size_t traverse_frame(frame_header_t *header, const u8 *src, size_t src_len);
+size_t traverse_frame(const frame_header_t *const header, const u8 *src,
+ size_t src_len);
/// Get the decompressed size of an input stream so memory can be allocated in
/// advance.
/// This is more complex than the implementation in the reference
/// implementation, as this API allows for the decompression of multiple
/// concatenated frames.
-size_t ZSTD_get_decompressed_size(const void *src, size_t src_len) {
+size_t ZSTD_get_decompressed_size(const void *src, const size_t src_len) {
const u8 *ip = (const u8 *) src;
+ size_t ip_len = src_len;
size_t dst_size = 0;
// Each frame header only gives us the size of its frame, so iterate over all
// frames
- while (src_len > 0) {
- if (src_len < 4) {
+ while (ip_len > 0) {
+ if (ip_len < 4) {
INP_SIZE();
}
- u32 magic_number = read_bits_LE(ip, 32, 0);
+ const u32 magic_number = read_bits_LE(ip, 32, 0);
ip += 4;
- src_len -= 4;
+ ip_len -= 4;
if (magic_number >= 0x184D2A50U && magic_number <= 0x184D2A5F) {
// skippable frame, this has no impact on output size
- if (src_len < 4) {
+ if (ip_len < 4) {
INP_SIZE();
}
- size_t frame_size = read_bits_LE(ip, 32, 32);
+ const size_t frame_size = read_bits_LE(ip, 32, 32);
- if (src_len < 4 + frame_size) {
+ if (ip_len < 4 + frame_size) {
INP_SIZE();
}
// skip over frame
ip += 4 + frame_size;
- src_len -= 4 + frame_size;
+ ip_len -= 4 + frame_size;
} else if (magic_number == 0xFD2FB528U) {
// ZSTD frame
frame_header_t header;
- parse_frame_header(&header, ip, src_len);
+ parse_frame_header(&header, ip, ip_len);
if (header.frame_content_size == 0 && !header.single_segment_flag) {
// Content size not provided, we can't tell
dst_size += header.frame_content_size;
// we need to traverse the frame to find when the next one starts
- size_t traversed = traverse_frame(&header, ip, src_len);
+ const size_t traversed = traverse_frame(&header, ip, ip_len);
ip += traversed;
- src_len -= traversed;
+ ip_len -= traversed;
} else {
// not a real frame
ERROR("Invalid magic number");
/// Iterate over each block in a frame to find the end of it, to get to the
/// start of the next frame
-size_t traverse_frame(frame_header_t *header, const u8 *src, size_t src_len) {
+size_t traverse_frame(const frame_header_t *const header, const u8 *src,
+ size_t src_len) {
const u8 *const src_beg = src;
const u8 *const src_end = src + src_len;
src += header->header_size;
}
// Parse the block header
last_block = src[0] & 1;
- int block_type = (src[0] >> 1) & 3;
- size_t block_len = read_bits_LE(src, 21, 3);
+ const int block_type = (src[0] >> 1) & 3;
+ const size_t block_len = read_bits_LE(src, 21, 3);
src += 3;
switch (block_type) {
/******* END OUTPUT SIZE COUNTING *********************************************/
/******* DICTIONARY PARSING ***************************************************/
-static void init_raw_content_dict(dictionary_t *dict, const u8 *src,
- size_t src_len);
+static void init_raw_content_dict(dictionary_t *const dict, const u8 *const src,
+ const size_t src_len);
-static void parse_dictionary(dictionary_t *dict, const u8 *src,
+static void parse_dictionary(dictionary_t *const 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);
+ const u32 magic_number = read_bits_LE(src, 32, 0);
if (magic_number != 0xEC30A437) {
// raw content dict
init_raw_content_dict(dict, src, src_len);
// Parse the provided entropy tables in order
{
- size_t read = decode_huf_table(src, src_len, &dict->literals_dtable);
+ const 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);
+ const 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);
+ const 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);
+ const size_t read = decode_seq_table(src, src_len, &dict->ll_dtable,
+ seq_literal_length, seq_fse);
src += read;
src_len -= read;
}
}
/// 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) {
+static void init_raw_content_dict(dictionary_t *const dict, const u8 *const src,
+ const size_t src_len) {
dict->dictionary_id = 0;
// Copy in the content
dict->content = malloc(src_len);
}
/// Free an allocated dictionary
-static void free_dictionary(dictionary_t *dict) {
+static void free_dictionary(dictionary_t *const dict) {
HUF_free_dtable(&dict->literals_dtable);
FSE_free_dtable(&dict->ll_dtable);
FSE_free_dtable(&dict->of_dtable);
}
/******* 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) {
+/// Read `num` bits (up to 64) from `src + offset`, where `offset` is in bits
+static inline u64 read_bits_LE(const u8 *src, const int num,
+ const size_t offset) {
if (num > 64) {
return -1;
}
+ // Skip over bytes that aren't in range
src += offset / 8;
- offset %= 8;
+ size_t bit_offset = 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;
+ // Dead the next byte, shift it to account for the offset, and then mask
+ // out the top part if we don't need all the bits
+ res += (((u64)*src++ >> bit_offset) & mask) << shift;
+ shift += 8 - bit_offset;
+ left -= 8 - bit_offset;
+ bit_offset = 0;
}
return res;
}
-static inline u64 STREAM_read_bits(const u8 *src, int bits, i64 *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 *const src, const int bits,
+ i64 *const offset) {
*offset = *offset - bits;
size_t actual_off = *offset;
+ size_t actual_bits = bits;
+ // Don't actually read bits from before the start of src, so if `*offset <
+ // 0` fix actual_off and actual_bits to reflect the quantity to read
if (*offset < 0) {
- bits += *offset;
+ actual_bits += *offset;
actual_off = 0;
}
- u64 res = read_bits_LE(src, bits, actual_off);
+ u64 res = read_bits_LE(src, actual_bits, actual_off);
if (*offset < 0) {
// Fill in the bottom "overflowed" bits with 0's
/******* 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) {
+/// 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(const u64 num) {
for (int i = 63; i >= 0; i--) {
if (((u64)1 << i) <= num) {
return i;
/******* END BIT COUNTING OPERATIONS ******************************************/
/******* HUFFMAN PRIMITIVES ***************************************************/
-static inline u8 HUF_decode_symbol(HUF_dtable *dtable, u16 *state,
- const u8 *src, i64 *offset) {
+static inline u8 HUF_decode_symbol(const HUF_dtable *const dtable,
+ u16 *const state, const u8 *const src,
+ i64 *const 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);
+ // Shift `bits` bits out of the state, keeping the low order bits that
+ // weren't necessary to determine this symbol. Then add in the new bits
+ // read from the stream.
*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
+static inline void HUF_init_state(const HUF_dtable *const dtable,
+ u16 *const state, const u8 *const src,
+ i64 *const offset) {
+ // Read in a full `dtable->max_bits` 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,
+static size_t HUF_decompress_1stream(const HUF_dtable *const dtable, u8 *dst,
+ const size_t dst_len, const u8 *src,
size_t src_len) {
- u8 *const dst_max = dst + dst_len;
- u8 *const odst = dst;
+ const u8 *const dst_max = dst + dst_len;
+ const 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]);
+ const 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) {
+ // Iterate over the stream, decoding one symbol at a time
*dst++ = HUF_decode_symbol(dtable, &state, src, &offset);
}
// If we stopped before consuming all the input, we didn't have enough space
OUT_SIZE();
}
- // The current state should be the `max_bits` preceding the start as
- // everything from `src` onward should be consumed
+ // When all symbols have been decoded, the final state value shouldn't have
+ // any data from the stream, so it should have "read" dtable->max_bits from
+ // before the start of `src`
+ // Therefore `offset`, the edge to start reading new bits at, should be
+ // dtable->max_bits before the start of the stream
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;
-
+static size_t HUF_decompress_4stream(const HUF_dtable *const dtable, u8 *dst,
+ const size_t dst_len, const u8 *const src,
+ const size_t src_len) {
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;
+ const u8 *const src1 = src + 6;
+ const u8 *const src2 = src1 + read_bits_LE(src, 16, 0);
+ const u8 *const src3 = src2 + read_bits_LE(src, 16, 16);
+ const u8 *const src4 = src3 + read_bits_LE(src, 16, 32);
+ const u8 *const 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
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;
+ const size_t segment_size = (dst_len + 3) / 4;
+ u8 *const dst1 = dst;
+ u8 *const dst2 = dst1 + segment_size;
+ u8 *const dst3 = dst2 + segment_size;
+ u8 *const dst4 = dst3 + segment_size;
+ u8 *const dst_end = dst + dst_len;
+
+ size_t total_out = 0;
- 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);
+ // 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
+ 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) {
+static void HUF_init_dtable(HUF_dtable *const table, const u8 *const bits,
+ const int num_symbs) {
memset(table, 0, sizeof(HUF_dtable));
if (num_symbs > HUF_MAX_SYMBS) {
ERROR("Too many symbols for Huffman");
rank_count[bits[i]]++;
}
- size_t table_size = 1 << max_bits;
+ const size_t table_size = 1 << max_bits;
table->max_bits = max_bits;
table->symbols = malloc(table_size);
table->num_bits = malloc(table_size);
if (bits[i] != 0) {
// Allocate a code for this symbol and set its range in the table
const u16 code = rank_idx[bits[i]];
+ // Since the code doesn't care about the bottom `max_bits - bits[i]`
+ // bits of state, it gets a range that spans all possible values of
+ // the lower bits
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) {
+static void HUF_init_dtable_usingweights(HUF_dtable *const table,
+ const u8 *const weights,
+ const 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");
}
// 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;
+ const int max_bits = log2inf(weight_sum) + 1;
+ const 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;
+ // left_over is used to find the last weight as it's not transmitted
+ // by inverting 2^(weight - 1) we can determine the value of last_weight
+ const 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
+ 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) {
+static void HUF_free_dtable(HUF_dtable *const 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) {
+static void HUF_copy_dtable(HUF_dtable *const dst,
+ const HUF_dtable *const src) {
if (src->max_bits == 0) {
memset(dst, 0, sizeof(HUF_dtable));
return;
}
- size_t size = (size_t)1 << src->max_bits;
+ const size_t size = (size_t)1 << src->max_bits;
dst->max_bits = src->max_bits;
dst->symbols = malloc(size);
/******* END HUFFMAN PRIMITIVES ***********************************************/
/******* FSE PRIMITIVES *******************************************************/
-static inline u8 FSE_peek_symbol(FSE_dtable *dtable, u16 state) {
+/// Allow a symbol to be decoded without updating state
+static inline u8 FSE_peek_symbol(const FSE_dtable *const dtable,
+ const u16 state) {
return dtable->symbols[state];
}
-static inline void FSE_update_state(FSE_dtable *dtable, u16 *state,
- const u8 *src, i64 *offset) {
+/// Consumes bits from the input and uses the current state to determine the
+/// next state
+static inline void FSE_update_state(const FSE_dtable *const dtable,
+ u16 *const state, const u8 *const src,
+ i64 *const 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) {
+/// Decodes a single FSE symbol and updates the offset
+static inline u8 FSE_decode_symbol(const FSE_dtable *const dtable,
+ u16 *const state, const u8 *const src,
+ i64 *const 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) {
+static inline void FSE_init_state(const FSE_dtable *const dtable,
+ u16 *const state, const u8 *const src,
+ i64 *const offset) {
+ // Read in a full `accuracy_log` bits to initialize the state
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) {
+static size_t FSE_decompress_interleaved2(const FSE_dtable *const dtable,
+ u8 *dst, const size_t dst_len,
+ const u8 *const src,
+ const size_t src_len) {
if (src_len == 0) {
INP_SIZE();
}
- u8 *dst_max = dst + dst_len;
- u8 *const odst = dst;
+ const u8 *const dst_max = dst + dst_len;
+ const u8 *const odst = dst;
// Find the last 1 bit
- int padding = 8 - log2inf(src[src_len - 1]);
+ const int padding = 8 - log2inf(src[src_len - 1]);
i64 offset = src_len * 8 - padding;
+ // The end of the stream contains the 2 states, in this order
u16 state1, state2;
FSE_init_state(dtable, &state1, src, &offset);
FSE_init_state(dtable, &state2, src, &offset);
*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);
+ *dst++ = FSE_peek_symbol(dtable, state2);
break;
}
*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);
+ *dst++ = FSE_peek_symbol(dtable, state1);
break;
}
}
- // number of symbols read
+ // 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) {
+static void FSE_init_dtable(FSE_dtable *const dtable,
+ const i16 *const norm_freqs, const int num_symbs,
+ const int accuracy_log) {
if (accuracy_log > FSE_MAX_ACCURACY_LOG) {
ERROR("FSE accuracy too large");
}
dtable->accuracy_log = accuracy_log;
- size_t size = (size_t)1 << accuracy_log;
+ const 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));
}
// Place the rest in the table
- u16 step = (size >> 1) + (size >> 3) + 3;
- u16 mask = size - 1;
+ const u16 step = (size >> 1) + (size >> 3) + 3;
+ const u16 mask = size - 1;
u16 pos = 0;
for (int s = 0; s < num_symbs; s++) {
if (norm_freqs[s] <= 0) {
state_desc[s] = norm_freqs[s];
for (int i = 0; i < norm_freqs[s]; i++) {
+ // Give `norm_freqs[s]` states to symbol s
dtable->symbols[pos] = s;
do {
pos = (pos + step) & mask;
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
+ // 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
+ // 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) {
+/// 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 *const dtable, const u8 *const src,
+ const size_t src_len,
+ const int max_accuracy_log) {
if (max_accuracy_log > FSE_MAX_ACCURACY_LOG) {
ERROR("FSE accuracy too large");
}
INP_SIZE();
}
- int accuracy_log = 5 + read_bits_LE(src, 4, 0);
+ const int accuracy_log = 5 + read_bits_LE(src, 4, 0);
if (accuracy_log > max_accuracy_log) {
ERROR("FSE accuracy too large");
}
i16 frequencies[FSE_MAX_SYMBS];
int symb = 0;
+ // Offset of 4 because 4 bits were already read in for accuracy
size_t offset = 4;
while (remaining > 1 && symb < FSE_MAX_SYMBS) {
- int bits = log2sup(remaining +
- 1); // the number of possible values we could read
+ // Log of the number of possible values we could read
+ int bits = log2inf(remaining) + 1;
+
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
+ // 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;
+ const u16 lower_mask = ((u16)1 << (bits - 1)) - 1;
+ const u16 threshold = ((u16)1 << bits) - 1 - remaining;
if ((val & lower_mask) < threshold) {
offset--;
val = val - threshold;
}
- i16 proba = (i16)val - 1;
- // a value of -1 is possible, and has special meaning
+ const i16 proba = (i16)val - 1;
+ // A value of -1 is possible, and has special meaning
remaining -= proba < 0 ? -proba : proba;
frequencies[symb] = proba;
// Handle the special probability = 0 case
if (proba == 0) {
- // read the next two bits to see how many more 0s
+ // Read the next two bits to see how many more 0s
int repeat = read_bits_LE(src, 2, offset);
offset += 2;
return (offset + 7) / 8;
}
-static void FSE_init_dtable_rle(FSE_dtable *dtable, u8 symb) {
+static void FSE_init_dtable_rle(FSE_dtable *const dtable, const u8 symb) {
dtable->symbols = malloc(sizeof(u8));
dtable->num_bits = malloc(sizeof(u8));
dtable->new_state_base = malloc(sizeof(u16));
dtable->accuracy_log = 0;
}
-static void FSE_free_dtable(FSE_dtable *dtable) {
+static void FSE_free_dtable(FSE_dtable *const 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) {
+static void FSE_copy_dtable(FSE_dtable *const dst, const FSE_dtable *const src) {
if (src->accuracy_log == 0) {
memset(dst, 0, sizeof(FSE_dtable));
return;
projects / thirdparty / zstd.git / commitdiff
