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OpenModem/Modem/compression/heatshrink_encoder.c

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#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include "heatshrink_encoder.h"
#include "cfg/debug.h" // Debug configuration from BertOS
typedef enum {
HSES_NOT_FULL, /* input buffer not full enough */
HSES_FILLED, /* buffer is full */
HSES_SEARCH, /* searching for patterns */
HSES_YIELD_TAG_BIT, /* yield tag bit */
HSES_YIELD_LITERAL, /* emit literal byte */
HSES_YIELD_BR_INDEX, /* yielding backref index */
HSES_YIELD_BR_LENGTH, /* yielding backref length */
HSES_SAVE_BACKLOG, /* copying buffer to backlog */
HSES_FLUSH_BITS, /* flush bit buffer */
HSES_DONE, /* done */
} HSE_state;
#if HEATSHRINK_DEBUGGING_LOGS
#include <stdio.h>
#include <ctype.h>
#include <assert.h>
#define LOG(...) fprintf(stderr, __VA_ARGS__)
#define ASSERT(X) assert(X)
static const char *state_names[] = {
"not_full",
"filled",
"search",
"yield_tag_bit",
"yield_literal",
"yield_br_index",
"yield_br_length",
"save_backlog",
"flush_bits",
"done",
};
#else
#define LOG(...) /* no-op */
#define ASSERT(X) /* no-op */
#endif
// Encoder flags
enum {
FLAG_IS_FINISHING = 0x01,
FLAG_HAS_LITERAL = 0x02,
FLAG_ON_FINAL_LITERAL = 0x04,
FLAG_BACKLOG_IS_PARTIAL = 0x08,
FLAG_BACKLOG_IS_FILLED = 0x10,
};
typedef struct {
uint8_t *buf; /* output buffer */
size_t buf_size; /* buffer size */
size_t *output_size; /* bytes pushed to buffer, so far */
} output_info;
#define MATCH_NOT_FOUND ((uint16_t)-1)
static uint16_t get_input_offset(heatshrink_encoder *hse);
static uint16_t get_input_buffer_size(heatshrink_encoder *hse);
static uint16_t get_lookahead_size(heatshrink_encoder *hse);
static void add_tag_bit(heatshrink_encoder *hse, output_info *oi, uint8_t tag);
static int can_take_byte(output_info *oi);
static int is_finishing(heatshrink_encoder *hse);
static int backlog_is_partial(heatshrink_encoder *hse);
static int backlog_is_filled(heatshrink_encoder *hse);
static int on_final_literal(heatshrink_encoder *hse);
static void save_backlog(heatshrink_encoder *hse);
static int has_literal(heatshrink_encoder *hse);
/* Push COUNT (max 8) bits to the output buffer, which has room. */
static void push_bits(heatshrink_encoder *hse, uint8_t count, uint8_t bits,
output_info *oi);
static uint8_t push_outgoing_bits(heatshrink_encoder *hse, output_info *oi);
static void push_literal_byte(heatshrink_encoder *hse, output_info *oi);
#if HEATSHRINK_DYNAMIC_ALLOC
heatshrink_encoder *heatshrink_encoder_alloc(uint8_t window_sz2,
uint8_t lookahead_sz2) {
if ((window_sz2 < HEATSHRINK_MIN_WINDOW_BITS) ||
(window_sz2 > HEATSHRINK_MAX_WINDOW_BITS) ||
(lookahead_sz2 < HEATSHRINK_MIN_LOOKAHEAD_BITS) ||
(lookahead_sz2 > window_sz2)) {
return NULL;
}
/* Note: 2 * the window size is used because the buffer needs to fit
* (1 << window_sz2) bytes for the current input, and an additional
* (1 << window_sz2) bytes for the previous buffer of input, which
* will be scanned for useful backreferences. */
size_t buf_sz = (2 << window_sz2);
kprintf("Trying to allocate: %d\n", buf_sz);
heatshrink_encoder *hse = HEATSHRINK_MALLOC(sizeof(*hse) + buf_sz);
if (hse == NULL) { return NULL; }
hse->window_sz2 = window_sz2;
hse->lookahead_sz2 = lookahead_sz2;
heatshrink_encoder_reset(hse);
#if HEATSHRINK_USE_INDEX
size_t index_sz = buf_sz*sizeof(uint16_t);
hse->search_index = HEATSHRINK_MALLOC(index_sz + sizeof(struct hs_index));
if (hse->search_index == NULL) {
HEATSHRINK_FREE(hse, sizeof(*hse) + buf_sz);
return NULL;
}
hse->search_index->size = index_sz;
#endif
LOG("-- allocated encoder with buffer size of %zu (%u byte input size)\n",
buf_sz, get_input_buffer_size(hse));
return hse;
}
void heatshrink_encoder_free(heatshrink_encoder *hse) {
size_t buf_sz = (2 << HEATSHRINK_ENCODER_WINDOW_BITS(hse));
#if HEATSHRINK_USE_INDEX
size_t index_sz = sizeof(struct hs_index) + hse->search_index->size;
HEATSHRINK_FREE(hse->search_index, index_sz);
(void)index_sz;
#endif
HEATSHRINK_FREE(hse, sizeof(heatshrink_encoder) + buf_sz);
(void)buf_sz;
}
#endif
void heatshrink_encoder_reset(heatshrink_encoder *hse) {
size_t buf_sz = (2 << HEATSHRINK_ENCODER_WINDOW_BITS(hse));
memset(hse->buffer, 0, buf_sz);
hse->input_size = 0;
hse->state = HSES_NOT_FULL;
hse->match_scan_index = 0;
hse->flags = 0;
hse->bit_index = 0x80;
hse->current_byte = 0x00;
hse->match_length = 0;
hse->outgoing_bits = 0x0000;
hse->outgoing_bits_count = 0;
#ifdef LOOP_DETECT
hse->loop_detect = (uint32_t)-1;
#endif
}
HSE_sink_res heatshrink_encoder_sink(heatshrink_encoder *hse,
uint8_t *in_buf, size_t size, size_t *input_size) {
if ((hse == NULL) || (in_buf == NULL) || (input_size == NULL)) {
return HSER_SINK_ERROR_NULL;
}
/* Sinking more content after saying the content is done, tsk tsk */
if (is_finishing(hse)) { return HSER_SINK_ERROR_MISUSE; }
/* Sinking more content before processing is done */
if (hse->state != HSES_NOT_FULL) { return HSER_SINK_ERROR_MISUSE; }
uint16_t write_offset = get_input_offset(hse) + hse->input_size;
uint16_t ibs = get_input_buffer_size(hse);
uint16_t rem = ibs - hse->input_size;
uint16_t cp_sz = rem < size ? rem : size;
memcpy(&hse->buffer[write_offset], in_buf, cp_sz);
*input_size = cp_sz;
hse->input_size += cp_sz;
LOG("-- sunk %u bytes (of %zu) into encoder at %d, input buffer now has %u\n",
cp_sz, size, write_offset, hse->input_size);
if (cp_sz == rem) {
LOG("-- internal buffer is now full\n");
hse->state = HSES_FILLED;
}
return HSER_SINK_OK;
}
/***************
* Compression *
***************/
static uint16_t find_longest_match(heatshrink_encoder *hse, uint16_t start,
uint16_t end, const uint16_t maxlen, uint16_t *match_length);
static void do_indexing(heatshrink_encoder *hse);
static HSE_state st_step_search(heatshrink_encoder *hse);
static HSE_state st_yield_tag_bit(heatshrink_encoder *hse,
output_info *oi);
static HSE_state st_yield_literal(heatshrink_encoder *hse,
output_info *oi);
static HSE_state st_yield_br_index(heatshrink_encoder *hse,
output_info *oi);
static HSE_state st_yield_br_length(heatshrink_encoder *hse,
output_info *oi);
static HSE_state st_save_backlog(heatshrink_encoder *hse);
static HSE_state st_flush_bit_buffer(heatshrink_encoder *hse,
output_info *oi);
HSE_poll_res heatshrink_encoder_poll(heatshrink_encoder *hse,
uint8_t *out_buf, size_t out_buf_size, size_t *output_size) {
if ((hse == NULL) || (out_buf == NULL) || (output_size == NULL)) {
return HSER_POLL_ERROR_NULL;
}
if (out_buf_size == 0) {
LOG("-- MISUSE: output buffer size is 0\n");
return HSER_POLL_ERROR_MISUSE;
}
*output_size = 0;
output_info oi;
oi.buf = out_buf;
oi.buf_size = out_buf_size;
oi.output_size = output_size;
while (1) {
LOG("-- polling, state %u (%s), flags 0x%02x\n",
hse->state, state_names[hse->state], hse->flags);
uint8_t in_state = hse->state;
switch (in_state) {
case HSES_NOT_FULL:
return HSER_POLL_EMPTY;
case HSES_FILLED:
do_indexing(hse);
hse->state = HSES_SEARCH;
break;
case HSES_SEARCH:
hse->state = st_step_search(hse);
break;
case HSES_YIELD_TAG_BIT:
hse->state = st_yield_tag_bit(hse, &oi);
break;
case HSES_YIELD_LITERAL:
hse->state = st_yield_literal(hse, &oi);
break;
case HSES_YIELD_BR_INDEX:
hse->state = st_yield_br_index(hse, &oi);
break;
case HSES_YIELD_BR_LENGTH:
hse->state = st_yield_br_length(hse, &oi);
break;
case HSES_SAVE_BACKLOG:
hse->state = st_save_backlog(hse);
break;
case HSES_FLUSH_BITS:
hse->state = st_flush_bit_buffer(hse, &oi);
case HSES_DONE:
return HSER_POLL_EMPTY;
default:
LOG("-- bad state %s\n", state_names[hse->state]);
return HSER_POLL_ERROR_MISUSE;
}
if (hse->state == in_state) {
/* Check if output buffer is exhausted. */
if (*output_size == out_buf_size) return HSER_POLL_MORE;
}
}
}
HSE_finish_res heatshrink_encoder_finish(heatshrink_encoder *hse) {
if (hse == NULL) { return HSER_FINISH_ERROR_NULL; }
LOG("-- setting is_finishing flag\n");
hse->flags |= FLAG_IS_FINISHING;
if (hse->state == HSES_NOT_FULL) { hse->state = HSES_FILLED; }
return hse->state == HSES_DONE ? HSER_FINISH_DONE : HSER_FINISH_MORE;
}
static HSE_state st_step_search(heatshrink_encoder *hse) {
uint16_t window_length = get_input_buffer_size(hse);
uint16_t lookahead_sz = get_lookahead_size(hse);
uint16_t msi = hse->match_scan_index;
LOG("## step_search, scan @ +%d (%d/%d), input size %d\n",
msi, hse->input_size + msi, 2*window_length, hse->input_size);
bool fin = is_finishing(hse);
if (msi >= hse->input_size - (fin ? 0 : lookahead_sz)) {
/* Current search buffer is exhausted, copy it into the
* backlog and await more input. */
LOG("-- end of search @ %d, saving backlog\n", msi);
return HSES_SAVE_BACKLOG;
}
uint16_t input_offset = get_input_offset(hse);
uint16_t end = input_offset + msi;
uint16_t start = 0;
if (backlog_is_filled(hse)) { /* last WINDOW_LENGTH bytes */
start = end - window_length + 1;
} else if (backlog_is_partial(hse)) { /* clamp to available data */
start = end - window_length + 1;
if (start < lookahead_sz) { start = lookahead_sz; }
} else { /* only scan available input */
start = input_offset;
}
uint16_t max_possible = lookahead_sz;
if (hse->input_size - msi < lookahead_sz) {
max_possible = hse->input_size - msi;
}
uint16_t match_length = 0;
uint16_t match_pos = find_longest_match(hse,
start, end, max_possible, &match_length);
if (match_pos == MATCH_NOT_FOUND) {
LOG("ss Match not found\n");
hse->match_scan_index++;
hse->flags |= FLAG_HAS_LITERAL;
hse->match_length = 0;
return HSES_YIELD_TAG_BIT;
} else {
LOG("ss Found match of %d bytes at %d\n", match_length, match_pos);
hse->match_pos = match_pos;
hse->match_length = match_length;
ASSERT(match_pos < 1 << hse->window_sz2 /*window_length*/);
return HSES_YIELD_TAG_BIT;
}
}
static HSE_state st_yield_tag_bit(heatshrink_encoder *hse,
output_info *oi) {
if (can_take_byte(oi)) {
if (hse->match_length == 0) {
add_tag_bit(hse, oi, HEATSHRINK_LITERAL_MARKER);
return HSES_YIELD_LITERAL;
} else {
add_tag_bit(hse, oi, HEATSHRINK_BACKREF_MARKER);
hse->outgoing_bits = hse->match_pos - 1;
hse->outgoing_bits_count = HEATSHRINK_ENCODER_WINDOW_BITS(hse);
return HSES_YIELD_BR_INDEX;
}
} else {
return HSES_YIELD_TAG_BIT; /* output is full, continue */
}
}
static HSE_state st_yield_literal(heatshrink_encoder *hse,
output_info *oi) {
if (can_take_byte(oi)) {
push_literal_byte(hse, oi);
hse->flags &= ~FLAG_HAS_LITERAL;
if (on_final_literal(hse)) { return HSES_FLUSH_BITS; }
return hse->match_length > 0 ? HSES_YIELD_TAG_BIT : HSES_SEARCH;
} else {
return HSES_YIELD_LITERAL;
}
}
static HSE_state st_yield_br_index(heatshrink_encoder *hse,
output_info *oi) {
if (can_take_byte(oi)) {
LOG("-- yielding backref index %u\n", hse->match_pos);
if (push_outgoing_bits(hse, oi) > 0) {
return HSES_YIELD_BR_INDEX; /* continue */
} else {
hse->outgoing_bits = hse->match_length - 1;
hse->outgoing_bits_count = HEATSHRINK_ENCODER_LOOKAHEAD_BITS(hse);
return HSES_YIELD_BR_LENGTH; /* done */
}
} else {
return HSES_YIELD_BR_INDEX; /* continue */
}
}
static HSE_state st_yield_br_length(heatshrink_encoder *hse,
output_info *oi) {
if (can_take_byte(oi)) {
LOG("-- yielding backref length %u\n", hse->match_length);
if (push_outgoing_bits(hse, oi) > 0) {
return HSES_YIELD_BR_LENGTH;
} else {
hse->match_scan_index += hse->match_length;
hse->match_length = 0;
return HSES_SEARCH;
}
} else {
return HSES_YIELD_BR_LENGTH;
}
}
static HSE_state st_save_backlog(heatshrink_encoder *hse) {
if (is_finishing(hse)) {
/* copy remaining literal (if necessary) */
if (has_literal(hse)) {
hse->flags |= FLAG_ON_FINAL_LITERAL;
return HSES_YIELD_TAG_BIT;
} else {
return HSES_FLUSH_BITS;
}
} else {
LOG("-- saving backlog\n");
save_backlog(hse);
return HSES_NOT_FULL;
}
}
static HSE_state st_flush_bit_buffer(heatshrink_encoder *hse,
output_info *oi) {
if (hse->bit_index == 0x80) {
LOG("-- done!\n");
return HSES_DONE;
} else if (can_take_byte(oi)) {
LOG("-- flushing remaining byte (bit_index == 0x%02x)\n", hse->bit_index);
oi->buf[(*oi->output_size)++] = hse->current_byte;
LOG("-- done!\n");
return HSES_DONE;
} else {
return HSES_FLUSH_BITS;
}
}
static void add_tag_bit(heatshrink_encoder *hse, output_info *oi, uint8_t tag) {
LOG("-- adding tag bit: %d\n", tag);
push_bits(hse, 1, tag, oi);
}
static uint16_t get_input_offset(heatshrink_encoder *hse) {
return get_input_buffer_size(hse);
}
static uint16_t get_input_buffer_size(heatshrink_encoder *hse) {
return (1 << HEATSHRINK_ENCODER_WINDOW_BITS(hse));
(void)hse;
}
static uint16_t get_lookahead_size(heatshrink_encoder *hse) {
return (1 << HEATSHRINK_ENCODER_LOOKAHEAD_BITS(hse));
(void)hse;
}
static void do_indexing(heatshrink_encoder *hse) {
#if HEATSHRINK_USE_INDEX
/* Build an index array I that contains flattened linked lists
* for the previous instances of every byte in the buffer.
*
* For example, if buf[200] == 'x', then index[200] will either
* be an offset i such that buf[i] == 'x', or a negative offset
* to indicate end-of-list. This significantly speeds up matching,
* while only using sizeof(uint16_t)*sizeof(buffer) bytes of RAM.
*
* Future optimization options:
* 1. Since any negative value represents end-of-list, the other
* 15 bits could be used to improve the index dynamically.
*
* 2. Likewise, the last lookahead_sz bytes of the index will
* not be usable, so temporary data could be stored there to
* dynamically improve the index.
* */
struct hs_index *hsi = HEATSHRINK_ENCODER_INDEX(hse);
uint16_t last[256];
memset(last, 0xFF, sizeof(last));
uint8_t * const data = hse->buffer;
int16_t * const index = hsi->index;
const uint16_t input_offset = get_input_offset(hse);
const uint16_t end = input_offset + hse->input_size;
for (uint16_t i=0; i<end; i++) {
uint8_t v = data[i];
uint16_t lv = last[v];
index[i] = lv;
last[v] = i;
}
#else
(void)hse;
#endif
}
static int is_finishing(heatshrink_encoder *hse) {
return hse->flags & FLAG_IS_FINISHING;
}
static int backlog_is_partial(heatshrink_encoder *hse) {
return hse->flags & FLAG_BACKLOG_IS_PARTIAL;
}
static int backlog_is_filled(heatshrink_encoder *hse) {
return hse->flags & FLAG_BACKLOG_IS_FILLED;
}
static int on_final_literal(heatshrink_encoder *hse) {
return hse->flags & FLAG_ON_FINAL_LITERAL;
}
static int has_literal(heatshrink_encoder *hse) {
return (hse->flags & FLAG_HAS_LITERAL);
}
static int can_take_byte(output_info *oi) {
return *oi->output_size < oi->buf_size;
}
/* Return the longest match for the bytes at buf[end:end+maxlen] between
* buf[start] and buf[end-1]. If no match is found, return -1. */
static uint16_t find_longest_match(heatshrink_encoder *hse, uint16_t start,
uint16_t end, const uint16_t maxlen, uint16_t *match_length) {
LOG("-- scanning for match of buf[%u:%u] between buf[%u:%u] (max %u bytes)\n",
end, end + maxlen, start, end + maxlen - 1, maxlen);
uint8_t *buf = hse->buffer;
uint16_t match_maxlen = 0;
uint16_t match_index = MATCH_NOT_FOUND;
const uint16_t break_even_point = 3;
uint16_t len = 0;
uint8_t * const needlepoint = &buf[end];
#if HEATSHRINK_USE_INDEX
struct hs_index *hsi = HEATSHRINK_ENCODER_INDEX(hse);
int16_t pos = hsi->index[end];
while (pos >= start) {
uint8_t * const pospoint = &buf[pos];
len = 0;
for (len = 1; len < maxlen; len++) {
if (pospoint[len] != needlepoint[len]) break;
}
if (len > match_maxlen) {
match_maxlen = len;
match_index = pos;
if (len == maxlen) { break; } /* won't find better */
}
pos = hsi->index[pos];
}
#else
for (int16_t pos=end - 1; pos >= start; pos--) {
for (len=0; len<maxlen; len++) {
if (0) {
LOG(" --> cmp buf[%d] == 0x%02x against %02x (start %u)\n",
pos + len, buf[pos + len], needlepoint[len], start);
}
if (buf[pos + len] != needlepoint[len]) { break; }
}
if (len > match_maxlen) {
match_maxlen = len;
match_index = pos;
if (len == maxlen) { break; } /* don't keep searching */
}
}
#endif
if (match_maxlen >= break_even_point) {
LOG("-- best match: %u bytes at -%u\n",
match_maxlen, end - match_index);
*match_length = match_maxlen;
return end - match_index;
}
LOG("-- none found\n");
return MATCH_NOT_FOUND;
}
static uint8_t push_outgoing_bits(heatshrink_encoder *hse, output_info *oi) {
uint8_t count = 0;
uint8_t bits = 0;
if (hse->outgoing_bits_count > 8) {
count = 8;
bits = hse->outgoing_bits >> (hse->outgoing_bits_count - 8);
} else {
count = hse->outgoing_bits_count;
bits = hse->outgoing_bits;
}
if (count > 0) {
LOG("-- pushing %d outgoing bits: 0x%02x\n", count, bits);
push_bits(hse, count, bits, oi);
hse->outgoing_bits_count -= count;
}
return count;
}
/* Push COUNT (max 8) bits to the output buffer, which has room.
* Bytes are set from the lowest bits, up. */
static void push_bits(heatshrink_encoder *hse, uint8_t count, uint8_t bits,
output_info *oi) {
ASSERT(count <= 8);
LOG("++ push_bits: %d bits, input of 0x%02x\n", count, bits);
/* If adding a whole byte and at the start of a new output byte,
* just push it through whole and skip the bit IO loop. */
if (count == 8 && hse->bit_index == 0x80) {
oi->buf[(*oi->output_size)++] = bits;
} else {
for (int i=count - 1; i>=0; i--) {
bool bit = bits & (1 << i);
if (bit) { hse->current_byte |= hse->bit_index; }
if (0) {
LOG(" -- setting bit %d at bit index 0x%02x, byte => 0x%02x\n",
bit ? 1 : 0, hse->bit_index, hse->current_byte);
}
hse->bit_index >>= 1;
if (hse->bit_index == 0x00) {
hse->bit_index = 0x80;
LOG(" > pushing byte 0x%02x\n", hse->current_byte);
oi->buf[(*oi->output_size)++] = hse->current_byte;
hse->current_byte = 0x00;
}
}
}
}
static void push_literal_byte(heatshrink_encoder *hse, output_info *oi) {
uint16_t processed_offset = hse->match_scan_index - 1;
uint16_t input_offset = get_input_offset(hse) + processed_offset;
uint8_t c = hse->buffer[input_offset];
LOG("-- yielded literal byte 0x%02x ('%c') from +%d\n",
c, isprint(c) ? c : '.', input_offset);
push_bits(hse, 8, c, oi);
}
static void save_backlog(heatshrink_encoder *hse) {
size_t input_buf_sz = get_input_buffer_size(hse);
uint16_t msi = hse->match_scan_index;
/* Copy processed data to beginning of buffer, so it can be
* used for future matches. Don't bother checking whether the
* input is less than the maximum size, because if it isn't,
* we're done anyway. */
uint16_t rem = input_buf_sz - msi; // unprocessed bytes
uint16_t shift_sz = input_buf_sz + rem;
memmove(&hse->buffer[0],
&hse->buffer[input_buf_sz - rem],
shift_sz);
if (backlog_is_partial(hse)) {
/* The whole backlog is filled in now, so include it in scans. */
hse->flags |= FLAG_BACKLOG_IS_FILLED;
} else {
/* Include backlog, except for the first lookahead_sz bytes, which
* are still undefined. */
hse->flags |= FLAG_BACKLOG_IS_PARTIAL;
}
hse->match_scan_index = 0;
hse->input_size -= input_buf_sz - rem;
}
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