377 lines
13 KiB
C
377 lines
13 KiB
C
#include <stdlib.h>
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#include <string.h>
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#include "heatshrink_decoder.h"
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/* States for the polling state machine. */
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typedef enum {
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HSDS_EMPTY, /* no input to process */
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HSDS_INPUT_AVAILABLE, /* new input, completely unprocessed */
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HSDS_YIELD_LITERAL, /* ready to yield literal byte */
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HSDS_BACKREF_INDEX_MSB, /* most significant byte of index */
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HSDS_BACKREF_INDEX_LSB, /* least significant byte of index */
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HSDS_BACKREF_COUNT_MSB, /* most significant byte of count */
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HSDS_BACKREF_COUNT_LSB, /* least significant byte of count */
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HSDS_YIELD_BACKREF, /* ready to yield back-reference */
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HSDS_CHECK_FOR_MORE_INPUT, /* check if input is exhausted */
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} HSD_state;
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#if HEATSHRINK_DEBUGGING_LOGS
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#include <stdio.h>
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#include <ctype.h>
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#include <assert.h>
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#define LOG(...) fprintf(stderr, __VA_ARGS__)
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#define ASSERT(X) assert(X)
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static const char *state_names[] = {
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"empty",
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"input_available",
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"yield_literal",
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"backref_index",
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"backref_count",
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"yield_backref",
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"check_for_more_input",
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};
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#else
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#define LOG(...) /* no-op */
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#define ASSERT(X) /* no-op */
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#endif
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typedef struct {
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uint8_t *buf; /* output buffer */
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size_t buf_size; /* buffer size */
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size_t *output_size; /* bytes pushed to buffer, so far */
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} output_info;
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#define NO_BITS ((uint32_t)-1)
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/* Forward references. */
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static uint32_t get_bits(heatshrink_decoder *hsd, uint8_t count);
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static void push_byte(heatshrink_decoder *hsd, output_info *oi, uint8_t byte);
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#if HEATSHRINK_DYNAMIC_ALLOC
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heatshrink_decoder *heatshrink_decoder_alloc(uint16_t input_buffer_size,
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uint8_t window_sz2,
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uint8_t lookahead_sz2) {
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if ((window_sz2 < HEATSHRINK_MIN_WINDOW_BITS) ||
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(window_sz2 > HEATSHRINK_MAX_WINDOW_BITS) ||
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(input_buffer_size == 0) ||
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(lookahead_sz2 < HEATSHRINK_MIN_LOOKAHEAD_BITS) ||
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(lookahead_sz2 > window_sz2)) {
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return NULL;
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}
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size_t buffers_sz = (1 << window_sz2) + input_buffer_size;
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size_t sz = sizeof(heatshrink_decoder) + buffers_sz;
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heatshrink_decoder *hsd = HEATSHRINK_MALLOC(sz);
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if (hsd == NULL) { return NULL; }
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hsd->input_buffer_size = input_buffer_size;
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hsd->window_sz2 = window_sz2;
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hsd->lookahead_sz2 = lookahead_sz2;
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heatshrink_decoder_reset(hsd);
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LOG("-- allocated decoder with buffer size of %zu (%zu + %u + %u)\n",
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sz, sizeof(heatshrink_decoder), (1 << window_sz2), input_buffer_size);
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return hsd;
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}
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void heatshrink_decoder_free(heatshrink_decoder *hsd) {
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size_t buffers_sz = (1 << hsd->window_sz2) + hsd->input_buffer_size;
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size_t sz = sizeof(heatshrink_decoder) + buffers_sz;
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HEATSHRINK_FREE(hsd, sz);
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(void)sz; /* may not be used by free */
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}
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#endif
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void heatshrink_decoder_reset(heatshrink_decoder *hsd) {
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size_t buf_sz = 1 << HEATSHRINK_DECODER_WINDOW_BITS(hsd);
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size_t input_sz = HEATSHRINK_DECODER_INPUT_BUFFER_SIZE(hsd);
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memset(hsd->buffers, 0, buf_sz + input_sz);
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hsd->state = HSDS_EMPTY;
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hsd->input_size = 0;
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hsd->input_index = 0;
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hsd->bit_index = 0x00;
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hsd->current_byte = 0x00;
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hsd->output_count = 0;
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hsd->output_index = 0;
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hsd->head_index = 0;
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hsd->bit_accumulator = 0x00000000;
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}
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/* Copy SIZE bytes into the decoder's input buffer, if it will fit. */
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HSD_sink_res heatshrink_decoder_sink(heatshrink_decoder *hsd,
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uint8_t *in_buf, size_t size, size_t *input_size) {
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if ((hsd == NULL) || (in_buf == NULL) || (input_size == NULL)) {
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return HSDR_SINK_ERROR_NULL;
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}
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size_t rem = HEATSHRINK_DECODER_INPUT_BUFFER_SIZE(hsd) - hsd->input_size;
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if (rem == 0) {
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*input_size = 0;
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return HSDR_SINK_FULL;
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}
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size = rem < size ? rem : size;
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LOG("-- sinking %zd bytes\n", size);
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/* copy into input buffer (at head of buffers) */
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memcpy(&hsd->buffers[hsd->input_size], in_buf, size);
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hsd->input_size += size;
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if (hsd->state == HSDS_EMPTY) {
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hsd->state = HSDS_INPUT_AVAILABLE;
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hsd->input_index = 0;
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}
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*input_size = size;
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return HSDR_SINK_OK;
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}
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/*****************
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* Decompression *
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*****************/
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#define BACKREF_COUNT_BITS(HSD) (HEATSHRINK_DECODER_LOOKAHEAD_BITS(HSD))
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#define BACKREF_INDEX_BITS(HSD) (HEATSHRINK_DECODER_WINDOW_BITS(HSD))
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// States
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static HSD_state st_input_available(heatshrink_decoder *hsd);
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static HSD_state st_yield_literal(heatshrink_decoder *hsd,
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output_info *oi);
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static HSD_state st_backref_index_msb(heatshrink_decoder *hsd);
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static HSD_state st_backref_index_lsb(heatshrink_decoder *hsd);
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static HSD_state st_backref_count_msb(heatshrink_decoder *hsd);
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static HSD_state st_backref_count_lsb(heatshrink_decoder *hsd);
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static HSD_state st_yield_backref(heatshrink_decoder *hsd,
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output_info *oi);
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static HSD_state st_check_for_input(heatshrink_decoder *hsd);
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HSD_poll_res heatshrink_decoder_poll(heatshrink_decoder *hsd,
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uint8_t *out_buf, size_t out_buf_size, size_t *output_size) {
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if ((hsd == NULL) || (out_buf == NULL) || (output_size == NULL)) {
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return HSDR_POLL_ERROR_NULL;
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}
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*output_size = 0;
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output_info oi;
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oi.buf = out_buf;
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oi.buf_size = out_buf_size;
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oi.output_size = output_size;
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while (1) {
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LOG("-- poll, state is %d (%s), input_size %d\n",
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hsd->state, state_names[hsd->state], hsd->input_size);
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uint8_t in_state = hsd->state;
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switch (in_state) {
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case HSDS_EMPTY:
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return HSDR_POLL_EMPTY;
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case HSDS_INPUT_AVAILABLE:
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hsd->state = st_input_available(hsd);
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break;
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case HSDS_YIELD_LITERAL:
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hsd->state = st_yield_literal(hsd, &oi);
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break;
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case HSDS_BACKREF_INDEX_MSB:
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hsd->state = st_backref_index_msb(hsd);
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break;
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case HSDS_BACKREF_INDEX_LSB:
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hsd->state = st_backref_index_lsb(hsd);
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break;
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case HSDS_BACKREF_COUNT_MSB:
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hsd->state = st_backref_count_msb(hsd);
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break;
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case HSDS_BACKREF_COUNT_LSB:
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hsd->state = st_backref_count_lsb(hsd);
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break;
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case HSDS_YIELD_BACKREF:
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hsd->state = st_yield_backref(hsd, &oi);
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break;
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case HSDS_CHECK_FOR_MORE_INPUT:
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hsd->state = st_check_for_input(hsd);
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break;
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default:
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return HSDR_POLL_ERROR_UNKNOWN;
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}
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/* If the current state cannot advance, check if input or output
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* buffer are exhausted. */
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if (hsd->state == in_state) {
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if (*output_size == out_buf_size) { return HSDR_POLL_MORE; }
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return HSDR_POLL_EMPTY;
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}
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}
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}
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static HSD_state st_input_available(heatshrink_decoder *hsd) {
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uint32_t bits = get_bits(hsd, 1); // get tag bit
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if (bits) {
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return HSDS_YIELD_LITERAL;
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} else if (HEATSHRINK_DECODER_WINDOW_BITS(hsd) > 8) {
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return HSDS_BACKREF_INDEX_MSB;
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} else {
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hsd->output_index = 0;
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return HSDS_BACKREF_INDEX_LSB;
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}
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}
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static HSD_state st_yield_literal(heatshrink_decoder *hsd,
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output_info *oi) {
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/* Emit a repeated section from the window buffer, and add it (again)
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* to the window buffer. (Note that the repetition can include
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* itself.)*/
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if (*oi->output_size < oi->buf_size) {
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uint32_t byte = get_bits(hsd, 8);
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if (byte == NO_BITS) { return HSDS_YIELD_LITERAL; } /* out of input */
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uint8_t *buf = &hsd->buffers[HEATSHRINK_DECODER_INPUT_BUFFER_SIZE(hsd)];
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uint16_t mask = (1 << HEATSHRINK_DECODER_WINDOW_BITS(hsd)) - 1;
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uint8_t c = byte & 0xFF;
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LOG("-- emitting literal byte 0x%02x ('%c')\n", c, isprint(c) ? c : '.');
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buf[hsd->head_index++ & mask] = c;
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push_byte(hsd, oi, c);
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return HSDS_CHECK_FOR_MORE_INPUT;
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} else {
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return HSDS_YIELD_LITERAL;
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}
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}
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static HSD_state st_backref_index_msb(heatshrink_decoder *hsd) {
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uint8_t bit_ct = BACKREF_INDEX_BITS(hsd);
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ASSERT(bit_ct > 8);
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uint32_t bits = get_bits(hsd, bit_ct - 8);
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LOG("-- backref index (msb), got 0x%04x (+1)\n", bits);
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if (bits == NO_BITS) { return HSDS_BACKREF_INDEX_MSB; }
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hsd->output_index = bits << 8;
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return HSDS_BACKREF_INDEX_LSB;
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}
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static HSD_state st_backref_index_lsb(heatshrink_decoder *hsd) {
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uint8_t bit_ct = BACKREF_INDEX_BITS(hsd);
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uint32_t bits = get_bits(hsd, bit_ct < 8 ? bit_ct : 8);
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LOG("-- backref index (lsb), got 0x%04x (+1)\n", bits);
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if (bits == NO_BITS) { return HSDS_BACKREF_INDEX_LSB; }
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hsd->output_index |= bits;
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hsd->output_index++;
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uint8_t br_bit_ct = BACKREF_COUNT_BITS(hsd);
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hsd->output_count = 0;
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return (br_bit_ct > 8) ? HSDS_BACKREF_COUNT_MSB : HSDS_BACKREF_COUNT_LSB;
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}
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static HSD_state st_backref_count_msb(heatshrink_decoder *hsd) {
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uint8_t br_bit_ct = BACKREF_COUNT_BITS(hsd);
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ASSERT(br_bit_ct > 8);
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uint32_t bits = get_bits(hsd, br_bit_ct - 8);
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LOG("-- backref count (msb), got 0x%04x (+1)\n", bits);
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if (bits == NO_BITS) { return HSDS_BACKREF_COUNT_MSB; }
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hsd->output_count = bits << 8;
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return HSDS_BACKREF_COUNT_LSB;
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}
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static HSD_state st_backref_count_lsb(heatshrink_decoder *hsd) {
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uint8_t br_bit_ct = BACKREF_COUNT_BITS(hsd);
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uint32_t bits = get_bits(hsd, br_bit_ct < 8 ? br_bit_ct : 8);
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LOG("-- backref count (lsb), got 0x%04x (+1)\n", bits);
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if (bits == NO_BITS) { return HSDS_BACKREF_COUNT_LSB; }
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hsd->output_count |= bits;
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hsd->output_count++;
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return HSDS_YIELD_BACKREF;
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}
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static HSD_state st_yield_backref(heatshrink_decoder *hsd,
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output_info *oi) {
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size_t count = oi->buf_size - *oi->output_size;
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if (count > 0) {
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if (hsd->output_count < count) count = hsd->output_count;
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uint8_t *buf = &hsd->buffers[HEATSHRINK_DECODER_INPUT_BUFFER_SIZE(hsd)];
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uint16_t mask = (1 << HEATSHRINK_DECODER_WINDOW_BITS(hsd)) - 1;
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uint16_t neg_offset = hsd->output_index;
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LOG("-- emitting %zu bytes from -%u bytes back\n", count, neg_offset);
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ASSERT(neg_offset < mask + 1);
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ASSERT(count <= 1 << BACKREF_COUNT_BITS(hsd));
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for (size_t i=0; i<count; i++) {
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uint8_t c = buf[(hsd->head_index - neg_offset) & mask];
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push_byte(hsd, oi, c);
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buf[hsd->head_index & mask] = c;
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hsd->head_index++;
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LOG(" -- ++ 0x%02x\n", c);
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}
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hsd->output_count -= count;
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if (hsd->output_count == 0) { return HSDS_CHECK_FOR_MORE_INPUT; }
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}
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return HSDS_YIELD_BACKREF;
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}
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static HSD_state st_check_for_input(heatshrink_decoder *hsd) {
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return (hsd->input_size == 0) ? HSDS_EMPTY : HSDS_INPUT_AVAILABLE;
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}
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/* Get the next COUNT bits from the input buffer, saving incremental progress.
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* Returns NO_BITS on end of input, or if more than 31 bits are requested. */
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static uint32_t get_bits(heatshrink_decoder *hsd, uint8_t count) {
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if (count > 31) { return NO_BITS; }
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LOG("-- popping %u bit(s)\n", count);
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/* If we aren't able to get COUNT bits, suspend immediately, because we
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* don't track how many bits of COUNT we've accumulated before suspend. */
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if (hsd->input_size == 0) {
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if (hsd->bit_index < (1 << (count - 1))) { return NO_BITS; }
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}
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for (int i = 0; i < count; i++) {
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if (hsd->bit_index == 0x00) {
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if (hsd->input_size == 0) {
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LOG(" -- out of bits, suspending w/ accumulator of %u (0x%02x)\n",
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hsd->bit_accumulator, hsd->bit_accumulator);
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return NO_BITS;
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}
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hsd->current_byte = hsd->buffers[hsd->input_index++];
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LOG(" -- pulled byte 0x%02x\n", hsd->current_byte);
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if (hsd->input_index == hsd->input_size) {
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hsd->input_index = 0; /* input is exhausted */
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hsd->input_size = 0;
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}
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hsd->bit_index = 0x80;
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}
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hsd->bit_accumulator <<= 1;
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if (hsd->current_byte & hsd->bit_index) {
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hsd->bit_accumulator |= 0x01;
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if (0) {
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LOG(" -- got 1, accumulator 0x%04x, bit_index 0x%02x\n",
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hsd->bit_accumulator, hsd->bit_index);
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}
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} else {
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if (0) {
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LOG(" -- got 0, accumulator 0x%04x, bit_index 0x%02x\n",
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hsd->bit_accumulator, hsd->bit_index);
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}
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}
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hsd->bit_index >>= 1;
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}
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uint32_t res = 0;
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res = hsd->bit_accumulator;
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hsd->bit_accumulator = 0x00000000;
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if (count > 1) { LOG(" -- accumulated %08x\n", res); }
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return res;
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}
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HSD_finish_res heatshrink_decoder_finish(heatshrink_decoder *hsd) {
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if (hsd == NULL) { return HSDR_FINISH_ERROR_NULL; }
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switch (hsd->state) {
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case HSDS_EMPTY:
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return HSDR_FINISH_DONE;
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/* If we want to finish with no input, but are in these states, it's
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* because the 0-bit padding to the last byte looks like a backref
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* marker bit followed by all 0s for index and count bits. */
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case HSDS_BACKREF_INDEX_LSB:
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case HSDS_BACKREF_INDEX_MSB:
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case HSDS_BACKREF_COUNT_LSB:
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case HSDS_BACKREF_COUNT_MSB:
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return hsd->input_size == 0 ? HSDR_FINISH_DONE : HSDR_FINISH_MORE;
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/* fall through */
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default:
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return HSDR_FINISH_MORE;
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}
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}
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static void push_byte(heatshrink_decoder *hsd, output_info *oi, uint8_t byte) {
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LOG(" -- pushing byte: 0x%02x ('%c')\n", byte, isprint(byte) ? byte : '.');
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oi->buf[(*oi->output_size)++] = byte;
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(void)hsd;
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}
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