add huffman decoder

Author: fsasm

huff_dec.c

@@ -0,0 +1,106 @@
+/*
+ * @file huff_dec.c
+ * @author Fabjan Sukalia <[email protected]>
+ * @date 2016-02-03
+ */
+
+#include <stdlib.h>
+#include <assert.h>
+#include "bit_reader.h"
+#include "huff_dec.h"
+
+struct huff_dec {
+	uint8_t max_bits; /* num_entries = 1 << num_bits; */
+	uint8_t min_bits;
+
+	/* high byte: symbol; low byte: num_bits; invalid code if num_bits = 0 */
+	uint16_t *entries;
+};
+
+struct huff_dec *huff_gen_dec(uint8_t code_len[restrict 16], uint8_t symbols[restrict])
+{
+	assert(code_len != NULL);
+	assert(symbols  != NULL);
+
+	uint8_t num_sym = 0;
+	uint8_t max_bits = 0;
+	uint8_t min_bits = 0;
+
+	for (int i = 0; i < 16; i++) {
+		num_sym += code_len[i];
+		max_bits = (code_len[i] != 0) ? i + 1 : max_bits;
+		min_bits = (min_bits == 0 && code_len[i] != 0) ? i + 1 : min_bits;
+	}
+
+	uint8_t num_entries = 1 << max_bits;
+
+	struct huff_dec *dec = calloc(1, sizeof(*dec));
+	dec->max_bits = max_bits;
+	dec->min_bits = min_bits;
+	dec->entries = malloc(sizeof(uint16_t) * num_entries);
+
+	uint8_t sym_index = 0;
+	size_t index = 0;
+
+	uint16_t times = 1 << max_bits;
+	for (int i = 0; i < 16; i++) {
+		times >>= 1;
+
+		for (int j = 0; j < code_len[i]; j++) {
+			uint8_t symbol = symbols[sym_index];
+			sym_index++;
+
+			for (uint16_t t = 0; t < times; t++) {
+				dec->entries[index] = (symbol << 8) | (i + 1);
+				index++;
+			}
+		}
+	}
+
+	return dec;
+}
+
+bool huff_decode_all(struct huff_dec *dec, struct bit_reader *reader, FILE *out, uint32_t num_sym)
+{
+	assert(dec    != NULL);
+	assert(reader != NULL);
+	assert(out    != NULL);
+
+	uint16_t sym;
+	if (!bit_reader_next_bits(reader, &sym, dec->max_bits)) {
+		fprintf(stderr, "Error while reading input\n");
+		return false;
+	}
+
+	const uint16_t mask = (1 << dec->max_bits) - 1;
+
+	for (uint32_t i = 0; i < num_sym; i++) {
+		uint16_t entry = dec->entries[sym & mask];
+		uint8_t symbol = (entry >> 8) & 0xFF;
+		uint8_t len    = entry & 0xFF;
+		assert(len <= dec->max_bits);
+
+		fwrite(&symbol, 1, 1, out);
+		
+		if (i == num_sym - 1)
+			break;
+
+		uint16_t tmp;
+		if (!bit_reader_next_bits(reader, &tmp, len)) {
+			fprintf(stderr, "Error while reading input\n");
+			return false;
+		}
+		sym = ((sym << len) | tmp) & mask;
+	}
+
+	return true;
+}
+
+void huff_destroy(struct huff_dec *dec)
+{
+	assert(dec != NULL);
+
+	free(dec->entries);
+	free(dec);
+}
+

huff_dec.h

@@ -0,0 +1,23 @@
+/*
+ * @file huff_dec.h
+ * @author Fabjan Sukalia <[email protected]>
+ * @date 2016-02-03
+ * @brief Huffman tree generation and decoding.
+ */
+
+#ifndef HUFF_DEC_H
+#define HUFF_DEC_H
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include "bit_reader.h"
+
+struct huff_dec;
+
+struct huff_dec *huff_gen_dec(uint8_t code_len[restrict 16], uint8_t symbols[restrict]);
+bool huff_decode_all(struct huff_dec *tree, struct bit_reader *reader, FILE *out, uint32_t num_sym);
+void huff_destroy(struct huff_dec *tree);
+
+#endif
+