Initial release
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civ
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// gen_final.c: correct Huffman encoder table generator
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// The key insight: leaf>>8 is only the FINAL flush.
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// Total bits = sum of all intermediate flushes + leaf>>8.
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// Only the first peek (5 bits) is NOT flushed if we get a direct hit.
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#include <stdio.h>
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#include <stdint.h>
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#include <string.h>
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#include "tabs_data.h"
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static const int tmax[] = {
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0, 1, 2, 2, 0, 3, 3, 5, 5, 5, 7, 7, 7, 15, 0, 15,
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15,15,15,15,15,15,15,15, 15,15,15,15,15,15,15,15
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};
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typedef struct { uint32_t code; uint8_t len; } henc_t;
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static henc_t enc[16][16];
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// Walk the minimp3 tree and return {leaf, total_bits_consumed}
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// Returns -1 if cannot decode
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static int walk_tree(const int16_t *codebook, uint32_t bits, int nbits,
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int *total_consumed) {
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uint32_t cache = (nbits < 32) ? (bits << (32 - nbits)) : bits;
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int w = 5;
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int leaf = codebook[cache >> (32 - w)];
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int flushed = 0; // bits flushed so far
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if (leaf >= 0) {
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// Direct hit: only flush leaf>>8 bits (subset of the initial 5 peeked)
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*total_consumed = leaf >> 8;
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return leaf;
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}
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// Tree traversal: flush the initial 5 bits, then follow nodes
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cache <<= w;
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flushed = w;
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while (leaf < 0) {
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w = leaf & 7;
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if (w == 0) return -1;
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int peek = (int)(cache >> (32 - w));
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int idx = peek - (leaf >> 3);
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leaf = codebook[idx];
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if (leaf < 0) {
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// Not a leaf yet, flush these w bits and continue
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cache <<= w;
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flushed += w;
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if (flushed > 30) return -1;
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}
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}
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// leaf is positive: flush leaf>>8 more bits
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*total_consumed = flushed + (leaf >> 8);
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return leaf;
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}
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static void build_pair_table(int tab_num) {
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int mx = tmax[tab_num];
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memset(enc, 0, sizeof(enc));
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const int16_t *codebook = tabs + tabindex[tab_num];
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for (int len = 1; len <= 19; len++) {
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for (uint32_t code = 0; code < (1u << len); code++) {
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int total = 0;
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int leaf = walk_tree(codebook, code, len, &total);
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if (leaf < 0) continue;
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if (total != len) continue;
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int x = (leaf >> 4) & 0xF;
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int y = leaf & 0xF;
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if (x > mx || y > mx) continue;
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if (enc[x][y].len == 0) {
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enc[x][y].code = code;
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enc[x][y].len = (uint8_t)len;
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}
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}
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}
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}
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int main(void) {
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// Verify completeness first
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int ok = 1;
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for (int t = 1; t < 32; t++) {
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if (t == 0 || t == 4 || t == 14) continue;
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int mx = tmax[t]; if (mx == 0) continue;
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build_pair_table(t);
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int dim = mx + 1, found = 0;
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for (int x = 0; x < dim; x++)
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for (int y = 0; y < dim; y++)
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if (enc[x][y].len > 0) found++;
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int expected = dim * dim;
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if (found != expected) {
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fprintf(stderr, "Table %2d: %d/%d INCOMPLETE\n", t, found, expected);
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ok = 0;
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} else {
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fprintf(stderr, "Table %2d: %d/%d OK\n", t, found, expected);
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}
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}
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if (!ok) {
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fprintf(stderr, "WARNING: some tables incomplete\n");
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}
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// Generate output
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printf("// mp3 Huffman encoder lookup tables\n");
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printf("// Generated from minimp3 (CC0). ISO 11172-3 Table B.7.\n");
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printf("// code = MSB first bit pattern. len = number of bits.\n");
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printf("// Append sign bits for nonzero |x| and |y|.\n");
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printf("// Values >= 15 use linbits extension.\n\n");
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printf("static const uint8_t mp3enc_linbits[32] = {\n");
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printf(" 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,\n");
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printf(" 1,2,3,4,6,8,10,13,4,5,6,7,8,9,11,13\n};\n\n");
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for (int t = 1; t < 32; t++) {
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if (t == 0 || t == 4 || t == 14) continue;
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int mx = tmax[t]; if (mx == 0) continue;
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// Skip duplicate trees
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int skip = 0;
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for (int j = 1; j < t; j++) {
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if (j == 4 || j == 14) continue;
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if (tabindex[t] == tabindex[j] && tmax[t] == tmax[j]) {
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printf("// table %d: same tree as table %d (linbits=%d)\n\n", t, j, g_linbits[t]);
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skip = 1; break;
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}
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}
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if (skip) continue;
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build_pair_table(t);
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int dim = mx + 1;
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printf("static const uint16_t mp3enc_hcode_%d[%d][%d] = {\n", t, dim, dim);
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for (int x = 0; x < dim; x++) {
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printf(" {");
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for (int y = 0; y < dim; y++) {
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printf("0x%x", enc[x][y].code);
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if (y < dim-1) printf(",");
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}
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printf("}%s\n", x < dim-1 ? "," : "");
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}
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printf("};\nstatic const uint8_t mp3enc_hlen_%d[%d][%d] = {\n", t, dim, dim);
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for (int x = 0; x < dim; x++) {
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printf(" {");
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for (int y = 0; y < dim; y++) {
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printf("%d", enc[x][y].len);
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if (y < dim-1) printf(",");
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}
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printf("}%s\n", x < dim-1 ? "," : "");
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}
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printf("};\n\n");
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}
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// Count1 tables
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for (int tbl = 0; tbl < 2; tbl++) {
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const uint8_t *cb = tbl ? tab33 : tab32;
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printf("// count1 table %c (count1table_select=%d)\n", 'A'+tbl, tbl);
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printf("// index = v*8 + w*4 + x*2 + y\n");
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uint32_t codes[16]={0}; uint8_t lens[16]={0};
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for (int len = 1; len <= 10; len++) {
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for (uint32_t code = 0; code < (1u<<len); code++) {
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uint32_t cache = (len<32) ? (code<<(32-len)) : code;
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int peek4 = (int)(cache>>28);
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int leaf = cb[peek4];
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int consumed;
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if (leaf & 8) { consumed = leaf & 7; }
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else {
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int extra = leaf & 3, offset = leaf >> 3;
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cache <<= 4;
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int peek2 = (int)(cache >> (32-extra));
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leaf = cb[offset + peek2];
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consumed = leaf & 7;
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}
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if (consumed != len) continue;
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int v=(leaf>>7)&1, w=(leaf>>6)&1, x=(leaf>>5)&1, y=(leaf>>4)&1;
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int idx = v*8+w*4+x*2+y;
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if (lens[idx]==0) { codes[idx]=code; lens[idx]=(uint8_t)consumed; }
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}
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}
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printf("static const uint8_t mp3enc_count1%c_code[16] = {\n ", 'a'+tbl);
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for (int i=0;i<16;i++) { printf("%d",codes[i]); if(i<15) printf(","); if(i==7) printf("\n "); }
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printf("\n};\nstatic const uint8_t mp3enc_count1%c_len[16] = {\n ", 'a'+tbl);
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for (int i=0;i<16;i++) { printf("%d",lens[i]); if(i<15) printf(","); if(i==7) printf("\n "); }
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printf("\n};\n\n");
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}
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return 0;
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}
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