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added ability to remove error messages and dictionary support (#1975)

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for the benefit of smaller binary.
This commit is contained in:
Yann Collet 2020-01-27 11:39:29 -08:00 committed by GitHub
parent 5bcd6448b6
commit 9a71d07aa4
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GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 147 additions and 120 deletions
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3
doc/educational_decoder/Makefile
View File

@ -36,7 +36,7 @@ harness: $(HARNESS_FILES)
$(CC) $(FLAGS) $^ -o $@
clean:
@$(RM) harness
@$(RM) harness *.o
@$(RM) -rf harness.dSYM # MacOS specific
test: harness
@ -59,4 +59,3 @@ test: harness
@./harness tmp.zst tmp dictionary
@$(DIFF) -s tmp README.md
@$(RM) tmp* dictionary
@$(MAKE) clean

7
doc/educational_decoder/README.md
View File

@ -13,6 +13,13 @@ It also contains implementations of Huffman and FSE table decoding.
[Zstandard format specification]: https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md
[format specification]: https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md
While the library's primary objective is code clarity,
it also happens to compile into a small object file.
The object file can be made even smaller by removing error messages,
using the macro directive `ZDEC_NO_MESSAGE` at compilation time.
This can be reduced even further by foregoing dictionary support,
by defining `ZDEC_NO_DICTIONARY`.
`harness.c` provides a simple test harness around the decoder:
harness <input-file> <output-file> [dictionary]

5
doc/educational_decoder/harness.c
View File

@ -95,7 +95,12 @@ int main(int argc, char **argv)
dictionary_t* const parsed_dict = create_dictionary();
if (dict.size) {
#if defined (ZDEC_NO_DICTIONARY)
printf("dict.size = %zu \n", dict.size);
ERR_OUT("no dictionary support \n");
#else
parse_dictionary(parsed_dict, dict.address, dict.size);
#endif
}
size_t const decompressed_size =
ZSTD_decompress_with_dict(output, out_capacity,

252
doc/educational_decoder/zstd_decompress.c
View File

@ -10,25 +10,42 @@
/// 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>
#include <stdint.h> // uint8_t, etc.
#include <stdlib.h> // malloc, free, exit
#include <stdio.h> // fprintf
#include <string.h> // memset, memcpy
#include "zstd_decompress.h"
/******* UTILITY MACROS AND TYPES *********************************************/
// Max block size decompressed size is 128 KB and literal blocks can't be
// larger than their block
#define MAX_LITERALS_SIZE ((size_t)128 * 1024)
/******* IMPORTANT CONSTANTS *********************************************/
// Zstandard frame
// "Magic_Number
// 4 Bytes, little-endian format. Value : 0xFD2FB528"
#define ZSTD_MAGIC_NUMBER 0xFD2FB528U
// The size of `Block_Content` is limited by `Block_Maximum_Size`,
#define ZSTD_BLOCK_SIZE_MAX ((size_t)128 * 1024)
// literal blocks can't be larger than their block
#define MAX_LITERALS_SIZE ZSTD_BLOCK_SIZE_MAX
/******* UTILITY MACROS AND TYPES *********************************************/
#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#if defined(ZDEC_NO_MESSAGE)
#define MESSAGE(...)
#else
#define MESSAGE(...) fprintf(stderr, "" __VA_ARGS__)
#endif
/// This decoder calls exit(1) when it encounters an error, however a production
/// library should propagate error codes
#define ERROR(s) \
do { \
fprintf(stderr, "Error: %s\n", s); \
MESSAGE("Error: %s\n", s); \
exit(1); \
} while (0)
#define INP_SIZE() \
@ -39,12 +56,12 @@
#define BAD_ALLOC() ERROR("Memory allocation error")
#define IMPOSSIBLE() ERROR("An impossibility has occurred")
typedef uint8_t u8;
typedef uint8_t u8;
typedef uint16_t u16;
typedef uint32_t u32;
typedef uint64_t u64;
typedef int8_t i8;
typedef int8_t i8;
typedef int16_t i16;
typedef int32_t i32;
typedef int64_t i64;
@ -176,10 +193,6 @@ static void HUF_init_dtable_usingweights(HUF_dtable *const table,
/// Free the malloc'ed parts of a decoding table
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 *const dst, const HUF_dtable *const src);
/*** END HUFFMAN PRIMITIVES ***********/
/*** FSE PRIMITIVES *******************/
@ -241,10 +254,6 @@ 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 *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 *const dst, const FSE_dtable *const src);
/*** END FSE PRIMITIVES ***************/
/******* END IMPLEMENTATION PRIMITIVE PROTOTYPES ******************************/
@ -373,7 +382,7 @@ static void execute_match_copy(frame_context_t *const ctx, size_t offset,
size_t ZSTD_decompress(void *const dst, const size_t dst_len,
const void *const src, const size_t src_len) {
dictionary_t* uninit_dict = create_dictionary();
dictionary_t* const uninit_dict = create_dictionary();
size_t const decomp_size = ZSTD_decompress_with_dict(dst, dst_len, src,
src_len, uninit_dict);
free_dictionary(uninit_dict);
@ -417,12 +426,7 @@ static void decompress_data(frame_context_t *const ctx, ostream_t *const out,
static void decode_frame(ostream_t *const out, istream_t *const in,
const dictionary_t *const dict) {
const u32 magic_number = (u32)IO_read_bits(in, 32);
// Zstandard frame
//
// "Magic_Number
//
// 4 Bytes, little-endian format. Value : 0xFD2FB528"
if (magic_number == 0xFD2FB528U) {
if (magic_number == ZSTD_MAGIC_NUMBER) {
// ZSTD frame
decode_data_frame(out, in, dict);
@ -576,43 +580,6 @@ static void parse_frame_header(frame_header_t *const header,
}
}
/// 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 *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;
// If the requested dictionary_id is non-zero, the correct dictionary must
// be present
if (ctx->header.dictionary_id != 0 &&
ctx->header.dictionary_id != dict->dictionary_id) {
ERROR("Wrong dictionary provided");
}
// Copy the dict content to the context for references during sequence
// execution
ctx->dict_content = dict->content;
ctx->dict_content_len = 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);
// Copy the repeated offsets
memcpy(ctx->previous_offsets, dict->previous_offsets,
sizeof(ctx->previous_offsets));
}
}
/// Decompress the data from a frame block by block
static void decompress_data(frame_context_t *const ctx, ostream_t *const out,
istream_t *const in) {
@ -1411,7 +1378,7 @@ size_t ZSTD_get_decompressed_size(const void *src, const size_t src_len) {
{
const u32 magic_number = (u32)IO_read_bits(&in, 32);
if (magic_number == 0xFD2FB528U) {
if (magic_number == ZSTD_MAGIC_NUMBER) {
// ZSTD frame
frame_header_t header;
parse_frame_header(&header, &in);
@ -1431,17 +1398,33 @@ size_t ZSTD_get_decompressed_size(const void *src, const size_t src_len) {
/******* END OUTPUT SIZE COUNTING *********************************************/
/******* DICTIONARY PARSING ***************************************************/
#define DICT_SIZE_ERROR() ERROR("Dictionary size cannot be less than 8 bytes")
#define NULL_SRC() ERROR("Tried to create dictionary with pointer to null src");
dictionary_t* create_dictionary() {
dictionary_t* dict = calloc(1, sizeof(dictionary_t));
dictionary_t* const dict = calloc(1, sizeof(dictionary_t));
if (!dict) {
BAD_ALLOC();
}
return dict;
}
/// Free an allocated dictionary
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);
FSE_free_dtable(&dict->ml_dtable);
free(dict->content);
memset(dict, 0, sizeof(dictionary_t));
free(dict);
}
#if !defined(ZDEC_NO_DICTIONARY)
#define DICT_SIZE_ERROR() ERROR("Dictionary size cannot be less than 8 bytes")
#define NULL_SRC() ERROR("Tried to create dictionary with pointer to null src");
static void init_dictionary_content(dictionary_t *const dict,
istream_t *const in);
@ -1513,19 +1496,93 @@ static void init_dictionary_content(dictionary_t *const dict,
memcpy(dict->content, content, dict->content_size);
}
/// Free an allocated dictionary
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);
FSE_free_dtable(&dict->ml_dtable);
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;
}
free(dict->content);
const size_t size = (size_t)1 << src->max_bits;
dst->max_bits = src->max_bits;
memset(dict, 0, sizeof(dictionary_t));
dst->symbols = malloc(size);
dst->num_bits = malloc(size);
if (!dst->symbols || !dst->num_bits) {
BAD_ALLOC();
}
free(dict);
memcpy(dst->symbols, src->symbols, size);
memcpy(dst->num_bits, src->num_bits, size);
}
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;
}
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));
}
/// 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 *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;
// If the requested dictionary_id is non-zero, the correct dictionary must
// be present
if (ctx->header.dictionary_id != 0 &&
ctx->header.dictionary_id != dict->dictionary_id) {
ERROR("Wrong dictionary provided");
}
// Copy the dict content to the context for references during sequence
// execution
ctx->dict_content = dict->content;
ctx->dict_content_len = 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);
// Copy the repeated offsets
memcpy(ctx->previous_offsets, dict->previous_offsets,
sizeof(ctx->previous_offsets));
}
}
#else // ZDEC_NO_DICTIONARY is defined
static void frame_context_apply_dict(frame_context_t *const ctx,
const dictionary_t *const dict) {
(void)ctx;
if (dict && dict->content) ERROR("dictionary not supported");
}
#endif
/******* END DICTIONARY PARSING ***********************************************/
/******* IO STREAM OPERATIONS *************************************************/
@ -1945,26 +2002,6 @@ static void HUF_free_dtable(HUF_dtable *const dtable) {
free(dtable->num_bits);
memset(dtable, 0, sizeof(HUF_dtable));
}
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;
}
const 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 *******************************************************/
@ -2279,25 +2316,4 @@ static void FSE_free_dtable(FSE_dtable *const dtable) {
free(dtable->new_state_base);
memset(dtable, 0, sizeof(FSE_dtable));
}
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;
}
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 ***************************************************/