149 lines
3.3 KiB
C
149 lines
3.3 KiB
C
/* HuffEnc.c -- functions for Huffman encoding
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2016-05-16 : Igor Pavlov : Public domain */
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#include "Precomp.h"
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#include "HuffEnc.h"
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#include "Sort.h"
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#define kMaxLen 16
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#define NUM_BITS 10
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#define MASK ((1 << NUM_BITS) - 1)
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#define NUM_COUNTERS 64
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#define HUFFMAN_SPEED_OPT
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void Huffman_Generate(const UInt32 *freqs, UInt32 *p, Byte *lens, UInt32 numSymbols, UInt32 maxLen)
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{
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UInt32 num = 0;
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/* if (maxLen > 10) maxLen = 10; */
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{
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UInt32 i;
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#ifdef HUFFMAN_SPEED_OPT
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UInt32 counters[NUM_COUNTERS];
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for (i = 0; i < NUM_COUNTERS; i++)
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counters[i] = 0;
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for (i = 0; i < numSymbols; i++)
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{
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UInt32 freq = freqs[i];
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counters[(freq < NUM_COUNTERS - 1) ? freq : NUM_COUNTERS - 1]++;
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}
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for (i = 1; i < NUM_COUNTERS; i++)
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{
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UInt32 temp = counters[i];
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counters[i] = num;
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num += temp;
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}
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for (i = 0; i < numSymbols; i++)
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{
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UInt32 freq = freqs[i];
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if (freq == 0)
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lens[i] = 0;
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else
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p[counters[((freq < NUM_COUNTERS - 1) ? freq : NUM_COUNTERS - 1)]++] = i | (freq << NUM_BITS);
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}
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counters[0] = 0;
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HeapSort(p + counters[NUM_COUNTERS - 2], counters[NUM_COUNTERS - 1] - counters[NUM_COUNTERS - 2]);
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#else
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for (i = 0; i < numSymbols; i++)
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{
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UInt32 freq = freqs[i];
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if (freq == 0)
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lens[i] = 0;
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else
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p[num++] = i | (freq << NUM_BITS);
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}
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HeapSort(p, num);
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#endif
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}
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if (num < 2)
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{
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unsigned minCode = 0;
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unsigned maxCode = 1;
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if (num == 1)
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{
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maxCode = (unsigned)p[0] & MASK;
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if (maxCode == 0)
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maxCode++;
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}
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p[minCode] = 0;
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p[maxCode] = 1;
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lens[minCode] = lens[maxCode] = 1;
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return;
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}
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{
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UInt32 b, e, i;
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i = b = e = 0;
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do
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{
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UInt32 n, m, freq;
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n = (i != num && (b == e || (p[i] >> NUM_BITS) <= (p[b] >> NUM_BITS))) ? i++ : b++;
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freq = (p[n] & ~MASK);
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p[n] = (p[n] & MASK) | (e << NUM_BITS);
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m = (i != num && (b == e || (p[i] >> NUM_BITS) <= (p[b] >> NUM_BITS))) ? i++ : b++;
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freq += (p[m] & ~MASK);
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p[m] = (p[m] & MASK) | (e << NUM_BITS);
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p[e] = (p[e] & MASK) | freq;
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e++;
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}
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while (num - e > 1);
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{
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UInt32 lenCounters[kMaxLen + 1];
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for (i = 0; i <= kMaxLen; i++)
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lenCounters[i] = 0;
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p[--e] &= MASK;
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lenCounters[1] = 2;
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while (e > 0)
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{
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UInt32 len = (p[p[--e] >> NUM_BITS] >> NUM_BITS) + 1;
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p[e] = (p[e] & MASK) | (len << NUM_BITS);
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if (len >= maxLen)
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for (len = maxLen - 1; lenCounters[len] == 0; len--);
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lenCounters[len]--;
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lenCounters[len + 1] += 2;
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}
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{
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UInt32 len;
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i = 0;
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for (len = maxLen; len != 0; len--)
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{
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UInt32 k;
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for (k = lenCounters[len]; k != 0; k--)
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lens[p[i++] & MASK] = (Byte)len;
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}
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}
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{
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UInt32 nextCodes[kMaxLen + 1];
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{
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UInt32 code = 0;
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UInt32 len;
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for (len = 1; len <= kMaxLen; len++)
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nextCodes[len] = code = (code + lenCounters[len - 1]) << 1;
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}
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/* if (code + lenCounters[kMaxLen] - 1 != (1 << kMaxLen) - 1) throw 1; */
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{
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UInt32 k;
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for (k = 0; k < numSymbols; k++)
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p[k] = nextCodes[lens[k]]++;
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}
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}
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}
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}
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}
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