388 lines
11 KiB
C++
388 lines
11 KiB
C++
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// File: crn_huffman_codes.cpp
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// See Copyright Notice and license at the end of inc/crnlib.h
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#include "crn_core.h"
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#include "crn_huffman_codes.h"
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namespace crnlib
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{
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struct sym_freq
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{
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uint m_freq;
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uint16 m_left;
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uint16 m_right;
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inline bool operator< (const sym_freq& other) const
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{
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return m_freq > other.m_freq;
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}
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};
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static inline sym_freq* radix_sort_syms(uint num_syms, sym_freq* syms0, sym_freq* syms1)
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{
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const uint cMaxPasses = 2;
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uint hist[256 * cMaxPasses];
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memset(hist, 0, sizeof(hist[0]) * 256 * cMaxPasses);
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sym_freq* p = syms0;
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sym_freq* q = syms0 + (num_syms >> 1) * 2;
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for ( ; p != q; p += 2)
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{
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const uint freq0 = p[0].m_freq;
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const uint freq1 = p[1].m_freq;
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hist[ freq0 & 0xFF]++;
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hist[256 + ((freq0 >> 8) & 0xFF)]++;
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hist[ freq1 & 0xFF]++;
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hist[256 + ((freq1 >> 8) & 0xFF)]++;
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}
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if (num_syms & 1)
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{
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const uint freq = p->m_freq;
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hist[ freq & 0xFF]++;
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hist[256 + ((freq >> 8) & 0xFF)]++;
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}
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sym_freq* pCur_syms = syms0;
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sym_freq* pNew_syms = syms1;
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for (uint pass = 0; pass < cMaxPasses; pass++)
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{
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const uint* pHist = &hist[pass << 8];
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uint offsets[256];
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uint cur_ofs = 0;
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for (uint i = 0; i < 256; i += 2)
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{
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offsets[i] = cur_ofs;
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cur_ofs += pHist[i];
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offsets[i+1] = cur_ofs;
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cur_ofs += pHist[i+1];
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}
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const uint pass_shift = pass << 3;
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sym_freq* p = pCur_syms;
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sym_freq* q = pCur_syms + (num_syms >> 1) * 2;
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for ( ; p != q; p += 2)
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{
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uint c0 = p[0].m_freq;
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uint c1 = p[1].m_freq;
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if (pass)
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{
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c0 >>= 8;
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c1 >>= 8;
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}
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c0 &= 0xFF;
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c1 &= 0xFF;
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if (c0 == c1)
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{
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uint dst_offset0 = offsets[c0];
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offsets[c0] = dst_offset0 + 2;
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pNew_syms[dst_offset0] = p[0];
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pNew_syms[dst_offset0 + 1] = p[1];
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}
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else
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{
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uint dst_offset0 = offsets[c0]++;
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uint dst_offset1 = offsets[c1]++;
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pNew_syms[dst_offset0] = p[0];
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pNew_syms[dst_offset1] = p[1];
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}
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}
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if (num_syms & 1)
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{
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uint c = ((p->m_freq) >> pass_shift) & 0xFF;
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uint dst_offset = offsets[c];
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offsets[c] = dst_offset + 1;
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pNew_syms[dst_offset] = *p;
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}
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sym_freq* t = pCur_syms;
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pCur_syms = pNew_syms;
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pNew_syms = t;
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}
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#ifdef CRNLIB_ASSERTS_ENABLED
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uint prev_freq = 0;
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for (uint i = 0; i < num_syms; i++)
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{
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CRNLIB_ASSERT(!(pCur_syms[i].m_freq < prev_freq));
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prev_freq = pCur_syms[i].m_freq;
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}
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#endif
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return pCur_syms;
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}
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struct huffman_work_tables
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{
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enum { cMaxInternalNodes = cHuffmanMaxSupportedSyms };
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sym_freq syms0[cHuffmanMaxSupportedSyms + 1 + cMaxInternalNodes];
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sym_freq syms1[cHuffmanMaxSupportedSyms + 1 + cMaxInternalNodes];
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uint16 queue[cMaxInternalNodes];
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};
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void* create_generate_huffman_codes_tables()
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{
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return crnlib_new<huffman_work_tables>();
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}
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void free_generate_huffman_codes_tables(void* p)
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{
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crnlib_delete(static_cast<huffman_work_tables*>(p));
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}
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#if USE_CALCULATE_MINIMUM_REDUNDANCY
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/* calculate_minimum_redundancy() written by
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Alistair Moffat, alistair@cs.mu.oz.au,
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Jyrki Katajainen, jyrki@diku.dk
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November 1996.
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*/
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static void calculate_minimum_redundancy(int A[], int n) {
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int root; /* next root node to be used */
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int leaf; /* next leaf to be used */
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int next; /* next value to be assigned */
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int avbl; /* number of available nodes */
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int used; /* number of internal nodes */
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int dpth; /* current depth of leaves */
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/* check for pathological cases */
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if (n==0) { return; }
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if (n==1) { A[0] = 0; return; }
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/* first pass, left to right, setting parent pointers */
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A[0] += A[1]; root = 0; leaf = 2;
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for (next=1; next < n-1; next++) {
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/* select first item for a pairing */
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if (leaf>=n || A[root]<A[leaf]) {
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A[next] = A[root]; A[root++] = next;
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} else
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A[next] = A[leaf++];
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/* add on the second item */
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if (leaf>=n || (root<next && A[root]<A[leaf])) {
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A[next] += A[root]; A[root++] = next;
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} else
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A[next] += A[leaf++];
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}
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/* second pass, right to left, setting internal depths */
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A[n-2] = 0;
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for (next=n-3; next>=0; next--)
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A[next] = A[A[next]]+1;
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/* third pass, right to left, setting leaf depths */
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avbl = 1; used = dpth = 0; root = n-2; next = n-1;
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while (avbl>0) {
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while (root>=0 && A[root]==dpth) {
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used++; root--;
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}
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while (avbl>used) {
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A[next--] = dpth; avbl--;
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}
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avbl = 2*used; dpth++; used = 0;
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}
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}
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#endif
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bool generate_huffman_codes(void* pContext, uint num_syms, const uint16* pFreq, uint8* pCodesizes, uint& max_code_size, uint& total_freq_ret)
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{
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if ((!num_syms) || (num_syms > cHuffmanMaxSupportedSyms))
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return false;
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huffman_work_tables& state = *static_cast<huffman_work_tables*>(pContext);;
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uint max_freq = 0;
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uint total_freq = 0;
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uint num_used_syms = 0;
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for (uint i = 0; i < num_syms; i++)
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{
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uint freq = pFreq[i];
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if (!freq)
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pCodesizes[i] = 0;
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else
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{
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total_freq += freq;
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max_freq = math::maximum(max_freq, freq);
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sym_freq& sf = state.syms0[num_used_syms];
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sf.m_left = (uint16)i;
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sf.m_right = cUINT16_MAX;
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sf.m_freq = freq;
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num_used_syms++;
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}
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}
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total_freq_ret = total_freq;
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if (num_used_syms == 1)
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{
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pCodesizes[state.syms0[0].m_left] = 1;
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return true;
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}
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sym_freq* syms = radix_sort_syms(num_used_syms, state.syms0, state.syms1);
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#if USE_CALCULATE_MINIMUM_REDUNDANCY
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int x[cHuffmanMaxSupportedSyms];
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for (uint i = 0; i < num_used_syms; i++)
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x[i] = state.syms0[i].m_freq;
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calculate_minimum_redundancy(x, num_used_syms);
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uint max_len = 0;
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for (uint i = 0; i < num_used_syms; i++)
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{
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uint len = x[i];
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max_len = math::maximum(len, max_len);
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pCodesizes[state.syms0[i].m_left] = static_cast<uint8>(len);
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}
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return true;
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#else
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// Dummy node
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sym_freq& sf = state.syms0[num_used_syms];
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sf.m_left = cUINT16_MAX;
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sf.m_right = cUINT16_MAX;
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sf.m_freq = UINT_MAX;
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uint next_internal_node = num_used_syms + 1;
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uint queue_front = 0;
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uint queue_end = 0;
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uint next_lowest_sym = 0;
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uint num_nodes_remaining = num_used_syms;
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do
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{
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uint left_freq = syms[next_lowest_sym].m_freq;
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uint left_child = next_lowest_sym;
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if ((queue_end > queue_front) && (syms[state.queue[queue_front]].m_freq < left_freq))
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{
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left_child = state.queue[queue_front];
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left_freq = syms[left_child].m_freq;
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queue_front++;
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}
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else
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next_lowest_sym++;
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uint right_freq = syms[next_lowest_sym].m_freq;
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uint right_child = next_lowest_sym;
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if ((queue_end > queue_front) && (syms[state.queue[queue_front]].m_freq < right_freq))
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{
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right_child = state.queue[queue_front];
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right_freq = syms[right_child].m_freq;
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queue_front++;
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}
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else
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next_lowest_sym++;
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const uint internal_node_index = next_internal_node;
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next_internal_node++;
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CRNLIB_ASSERT(next_internal_node < CRNLIB_ARRAYSIZE(state.syms0));
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syms[internal_node_index].m_freq = left_freq + right_freq;
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syms[internal_node_index].m_left = static_cast<uint16>(left_child);
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syms[internal_node_index].m_right = static_cast<uint16>(right_child);
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CRNLIB_ASSERT(queue_end < huffman_work_tables::cMaxInternalNodes);
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state.queue[queue_end] = static_cast<uint16>(internal_node_index);
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queue_end++;
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num_nodes_remaining--;
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} while (num_nodes_remaining > 1);
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CRNLIB_ASSERT(next_lowest_sym == num_used_syms);
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CRNLIB_ASSERT((queue_end - queue_front) == 1);
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uint cur_node_index = state.queue[queue_front];
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uint32* pStack = (syms == state.syms0) ? (uint32*)state.syms1 : (uint32*)state.syms0;
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uint32* pStack_top = pStack;
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uint max_level = 0;
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for ( ; ; )
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{
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uint level = cur_node_index >> 16;
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uint node_index = cur_node_index & 0xFFFF;
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uint left_child = syms[node_index].m_left;
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uint right_child = syms[node_index].m_right;
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uint next_level = (cur_node_index + 0x10000) & 0xFFFF0000;
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if (left_child < num_used_syms)
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{
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max_level = math::maximum(max_level, level);
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pCodesizes[syms[left_child].m_left] = static_cast<uint8>(level + 1);
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if (right_child < num_used_syms)
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{
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pCodesizes[syms[right_child].m_left] = static_cast<uint8>(level + 1);
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if (pStack == pStack_top) break;
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cur_node_index = *--pStack;
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}
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else
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{
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cur_node_index = next_level | right_child;
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}
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}
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else
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{
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if (right_child < num_used_syms)
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{
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max_level = math::maximum(max_level, level);
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pCodesizes[syms[right_child].m_left] = static_cast<uint8>(level + 1);
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cur_node_index = next_level | left_child;
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}
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else
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{
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*pStack++ = next_level | left_child;
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cur_node_index = next_level | right_child;
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}
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}
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}
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max_code_size = max_level + 1;
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#endif
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||
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return true;
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||
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}
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||
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} // namespace crnlib
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||
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