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Commit 40347982 authored by Mike Iovine's avatar Mike Iovine
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Implement task 2.2 dynamic huffman codes

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inflate.c
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#include <stdio.h>
#include <assert.h>
#include <string.h>
#include <stdint.h>
#include <stdlib.h>
......@@ -83,6 +84,34 @@ huffman_t HUFFMAN_FIXED = {
NO_CODE, NO_CODE, NO_CODE, NO_CODE, NO_CODE}
};
/* Number of characters in the code-length alphabet */
#define N_CL_ALPHABET 19
int CL_ALPHABET[N_CL_ALPHABET] = {
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18
};
/* Number of characters in the distance alphabet */
#define N_DISTS 30
int DIST_ALPHABET[N_DISTS] = {
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
21, 22, 23, 24, 25, 26, 27, 28, 29
};
huffman_t HUFFMAN_FIXED_DISTS = {
.bl_counts = {0, 0, 0, 0, 0, 30, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
.alphabet = {NULL, NULL, NULL, NULL, NULL, DIST_ALPHABET, NULL, NULL,
NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL},
.min_codes = {NO_CODE, NO_CODE, NO_CODE, NO_CODE, NO_CODE, 0,
NO_CODE, NO_CODE, NO_CODE, NO_CODE, NO_CODE, NO_CODE,
NO_CODE, NO_CODE, NO_CODE, NO_CODE}
};
/* Conversion tables for lengths
* To index into lengths, use (value_read - LENGTH_OFFSET)
* We may have to read additional bits; check LEN_ADDITIONAL for how many
......@@ -92,6 +121,7 @@ int LEN_TABLE[29] = {
3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, 35, 43, 51,
59, 67, 83, 99, 115, 131, 163, 195, 227, 258
};
int LEN_ADDITIONAL[29] = {
0, 0, 0, 0, 0, 0, 0, 0,
1, 1, 1, 1, 2, 2, 2, 2,
......@@ -113,6 +143,42 @@ int DIST_ADDITIONAL[30] = {
9, 9, 10, 10, 11, 11, 12, 12, 13, 13
};
/*
* Constants for DYNAMIC code type
*/
/* Number of characters in the literal-length alphabet */
#define N_LITERALS 286
int LITERAL_ALPHABET[N_LITERALS] = {
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56,
57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74,
75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92,
93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108,
109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123,
124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138,
139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153,
154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168,
169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183,
184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198,
199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213,
214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228,
229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243,
244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258,
259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273,
274, 275, 276, 277, 278, 279, 280, 281, 282, 283, 284, 285
};
/* After the dynamic block header, a sequence of lengths
* occurs; the lengths correspond to characters in the
* code-length alphabet in this order.
*/
int CL_ORDER[N_CL_ALPHABET] = {
16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
};
/* Keep track of the bit we are at.
* DO NOT MODIFY ANYWHERE EXCEPT get_next_bit */
int _CUR_BIT = 0;
......@@ -163,19 +229,152 @@ int read_chunk(char *buf, huffman_t hf) {
return -1;
}
huffman_t *make_huffman(int *lens, int *alphabet, int n_symbols) {
huffman_t *hf = (huffman_t *) malloc(sizeof(huffman_t));
/* Initialize fields */
for (int i = 0; i < MAX_LENGTH + 1; i++) {
hf->bl_counts[i] = 0;
hf->alphabet[i] = NULL;
hf->min_codes[i] = NO_CODE;
}
/* Update bl_counts with the lens */
for (int i = 0; i < n_symbols; i++) {
int len = lens[i];
if (len != 0) {
hf->bl_counts[len] += 1;
}
}
/*
* Construct min_codes, the value of the smallest code for each
* code length
*/
int code = 0;
for (int i = 1; i < MAX_LENGTH + 1; i++) {
code = (code + hf->bl_counts[i - 1]) << 1;
if (hf->bl_counts[i] != 0) hf->min_codes[i] = code;
}
/*
* Start assigning codes to alphabet characters.
*/
for (int len = 0; len < MAX_LENGTH + 1; len++) {
if (hf->bl_counts[len] != 0) {
int *symbols = (int *) malloc(hf->bl_counts[len] * sizeof(int));
int cur = 0;
for (int sym = 0; sym < n_symbols; sym++) {
if (lens[sym] == len) {
symbols[cur] = sym;
cur += 1;
}
}
hf->alphabet[len] = symbols;
}
}
return hf;
}
void destroy_huffman(huffman_t *hf) {
for (int i = 0; i < MAX_LENGTH + 1; i++) {
if (hf->alphabet[i] != NULL) free(hf->alphabet[i]);
}
free(hf);
}
int *read_lens(char *buf, huffman_t *hf_codes, int num_symbols, int num_codes) {
int *lens = (int *) malloc(num_symbols * sizeof(int));
for (int i = 0; i < num_symbols; i++) lens[i] = 0;
int cur_lit = 0;
while (cur_lit < num_codes) {
int len = read_chunk(buf, *hf_codes);
if (len <= 15) {
lens[cur_lit] = len;
cur_lit += 1;
} else if (len == 16) {
int rep = get_n_bits(buf, 2, true) + 3;
int prev = lens[cur_lit - 1];
for (int j = 0; j < rep; j++) {
lens[cur_lit] = prev;
cur_lit += 1;
}
} else if (len == 17) {
int rep = get_n_bits(buf, 3, true) + 3;
for (int j = 0; j < rep; j++) {
lens[cur_lit] = 0;
cur_lit += 1;
}
} else if (len == 18) {
int rep = get_n_bits(buf, 7, true) + 11;
for (int j = 0; j < rep; j++) {
lens[cur_lit] = 0;
cur_lit += 1;
}
} else {
fprintf(stderr, "error: invalid length");
exit(1);
}
}
return lens;
}
/* Read the block starting at the n-th bit */
void read_block(char *buf, FILE *out) {
/* First bit is the BFINAL flag */
bool bfinal = get_next_bit(buf);
/* Next two bits are BTYPE */
int btype = get_n_bits(buf, 2, true);
/* By default, use fixed mapping */
huffman_t hf = HUFFMAN_FIXED;
huffman_t *hf = &HUFFMAN_FIXED;
huffman_t *hf_dist = &HUFFMAN_FIXED_DISTS;
if (btype == DYNAMIC) {
// TODO update hf if dynamic
/* Read dynamic block header */
int hlit = get_n_bits(buf, 5, true);
int hdist = get_n_bits(buf, 5, true);
int hclen = get_n_bits(buf, 4, true);
/* Read in the code lengths for the code-length alphabet */
int *lens_cl = (int *) malloc(N_CL_ALPHABET * sizeof(int));
for (int i = 0; i < N_CL_ALPHABET; i++) lens_cl[i] = 0;
for (int i = 0; i < hclen + 4; i++) {
int len = get_n_bits(buf, 3, true);
int cl = CL_ORDER[i];
lens_cl[cl] = len;
}
huffman_t *hf_codes = make_huffman(lens_cl, CL_ALPHABET, N_CL_ALPHABET);
/* Now read in the code lengths for the literal alphabet */
int *lens_lit = read_lens(buf, hf_codes, N_LITERALS, hlit + 257);
/* Huffman mapping for the length-literal alphabet */
huffman_t *hf_lit = make_huffman(lens_lit, LITERAL_ALPHABET, N_LITERALS);
/* Read in the lengths for the distance alphabet */
int *lens_dist = read_lens(buf, hf_codes, N_DISTS, hdist + 1);
/* Huffman mapping for the distance code alphabet */
huffman_t *hf_dist_new = make_huffman(lens_dist, DIST_ALPHABET, N_DISTS);
/* Cleanup */
destroy_huffman(hf_codes);
free(lens_cl);
free(lens_lit);
free(lens_dist);
hf = hf_lit;
hf_dist = hf_dist_new;
} else if (btype != FIXED) {
fprintf(stderr, "error: unrecognized btype\n");
exit(1);
......@@ -187,23 +386,23 @@ void read_block(char *buf, FILE *out) {
do
{
/* Match a huffman code */
chunk_val = read_chunk(buf, hf);
chunk_val = read_chunk(buf, *hf);
/* Literal, just write to output buffer */
if (chunk_val < 256) {
fwrite(&chunk_val, 1, sizeof(char), out);
fwrite(&chunk_val, 1, sizeof(char), out);
/* We read a length */
} else if (chunk_val > 256) {
int length = LEN_TABLE[chunk_val - LENGTH_OFFSET];
int addit_len = LEN_ADDITIONAL[chunk_val - LENGTH_OFFSET];
length += get_n_bits(buf, addit_len, true);
/* Next 5 bits are the distance code */
int dist_code = get_n_bits(buf, 5, false);
/* Read in the distance code */
int dist_code = read_chunk(buf, *hf_dist);
assert(dist_code != -1);
int dist = DIST_TABLE[dist_code];
int addit_dist = DIST_ADDITIONAL[dist_code];
dist += get_n_bits(buf, addit_dist, true);
for (int i = 0; i < length; i++) {
fseek(out, -dist, SEEK_CUR);
int val = fgetc(out);
......@@ -217,6 +416,11 @@ void read_block(char *buf, FILE *out) {
/* Skip over filler at the end of the block */
while (_CUR_BIT % 8 != 0) {
_CUR_BIT += 1;
}
if (btype == DYNAMIC) {
destroy_huffman(hf);
destroy_huffman(hf_dist);
}
}
......@@ -237,6 +441,7 @@ void inflate(FILE *fp) {
while (_CUR_BIT < 8 * size) {
read_block(buf, out);
break;
}
fclose(out);
......@@ -257,7 +462,7 @@ int main(int argc, char *argv[]) {
fprintf(stderr, "error: file not found\n");
return 1;
}
inflate(fp);
fclose(fp);
......
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