bool generate_huffman_codes(void* pContext, uint num_syms, const uint16* pFreq, uint8* pCodesizes, uint& max_code_size, uint& total_freq_ret, code_size_histogram &code_size_hist)
{
if ((!num_syms) || (num_syms > cHuffmanMaxSupportedSyms))
return false;
huffman_work_tables& state = *static_cast<huffman_work_tables*>(pContext);;
uint max_freq = 0;
uint total_freq = 0;
uint num_used_syms = 0;
for (uint i = 0; i < num_syms; i++)
{
uint freq = pFreq[i];
if (!freq)
pCodesizes[i] = 0;
else
{
total_freq += freq;
max_freq = math::maximum(max_freq, freq);
sym_freq& sf = state.syms0[num_used_syms];
sf.m_left = (uint16)i;
sf.m_right = cUINT16_MAX;
sf.m_freq = freq;
num_used_syms++;
}
}
total_freq_ret = total_freq;
if (num_used_syms == 1)
{
pCodesizes[state.syms0[0].m_left] = 1;
return true;
}
sym_freq* syms = radix_sort_syms(num_used_syms, state.syms0, state.syms1);
int x[cHuffmanMaxSupportedSyms];
for (uint i = 0; i < num_used_syms; i++)
x[i] = syms[i].m_freq;
calculate_minimum_redundancy(x, num_used_syms);
uint max_len = 0;
for (uint i = 0; i < num_used_syms; i++)
{
uint len = x[i];
max_len = math::maximum(len, max_len);
code_size_hist.m_num_codes[LZHAM_MIN(len, (uint)code_size_histogram::cMaxUnlimitedHuffCodeSize)]++;
pCodesizes[syms[i].m_left] = static_cast<uint8>(len);
}
max_code_size = max_len;
return true;
}
bool generate_huffman_codes(void* pContext, uint num_syms, const uint16* pFreq, uint8* pCodesizes, uint& max_code_size, uint& total_freq_ret)
{
if ((!num_syms) || (num_syms > cHuffmanMaxSupportedSyms))
return false;
huffman_work_tables& state = *static_cast<huffman_work_tables*>(pContext);;
uint max_freq = 0;
uint total_freq = 0;
uint num_used_syms = 0;
for (uint i = 0; i < num_syms; i++)
{
uint freq = pFreq[i];
if (!freq)
pCodesizes[i] = 0;
else
{
total_freq += freq;
max_freq = math::maximum(max_freq, freq);
sym_freq& sf = state.syms0[num_used_syms];
sf.m_left = (uint16)i;
sf.m_right = LZHAM_UINT16_MAX;
sf.m_freq = freq;
num_used_syms++;
}
}
total_freq_ret = total_freq;
if (num_used_syms == 1)
{
pCodesizes[state.syms0[0].m_left] = 1;
return true;
}
sym_freq* syms = radix_sort_syms(num_used_syms, state.syms0, state.syms1);
#if USE_CALCULATE_MINIMUM_REDUNDANCY
int x[cHuffmanMaxSupportedSyms];
for (uint i = 0; i < num_used_syms; i++)
x[i] = syms[i].m_freq;
calculate_minimum_redundancy(x, num_used_syms);
uint max_len = 0;
for (uint i = 0; i < num_used_syms; i++)
{
uint len = x[i];
max_len = math::maximum(len, max_len);
pCodesizes[syms[i].m_left] = static_cast<uint8>(len);
}
max_code_size = max_len;
#else
// Computes Huffman codelengths in linear time. More readable than calculate_minimum_redundancy(), and approximately the same speed, but not in-place.
// Dummy node
sym_freq& sf = state.syms0[num_used_syms];
sf.m_left = LZHAM_UINT16_MAX;
sf.m_right = LZHAM_UINT16_MAX;
sf.m_freq = UINT_MAX;
uint next_internal_node = num_used_syms + 1;
uint queue_front = 0;
uint queue_end = 0;
uint next_lowest_sym = 0;
uint num_nodes_remaining = num_used_syms;
do
{
uint left_freq = syms[next_lowest_sym].m_freq;
uint left_child = next_lowest_sym;
if ((queue_end > queue_front) && (syms[state.queue[queue_front]].m_freq < left_freq))
{
left_child = state.queue[queue_front];
left_freq = syms[left_child].m_freq;
queue_front++;
}
else
next_lowest_sym++;
uint right_freq = syms[next_lowest_sym].m_freq;
uint right_child = next_lowest_sym;
if ((queue_end > queue_front) && (syms[state.queue[queue_front]].m_freq < right_freq))
{
right_child = state.queue[queue_front];
right_freq = syms[right_child].m_freq;
queue_front++;
}
else
next_lowest_sym++;
LZHAM_ASSERT(next_internal_node < huffman_work_tables::cMaxInternalNodes);
const uint internal_node_index = next_internal_node;
next_internal_node++;
syms[internal_node_index].m_freq = left_freq + right_freq;
syms[internal_node_index].m_left = static_cast<uint16>(left_child);
syms[internal_node_index].m_right = static_cast<uint16>(right_child);
LZHAM_ASSERT(queue_end < huffman_work_tables::cMaxInternalNodes);
state.queue[queue_end] = static_cast<uint16>(internal_node_index);
queue_end++;
num_nodes_remaining--;
} while (num_nodes_remaining > 1);
LZHAM_ASSERT(next_lowest_sym == num_used_syms);
LZHAM_ASSERT((queue_end - queue_front) == 1);
uint cur_node_index = state.queue[queue_front];
uint32* pStack = (syms == state.syms0) ? (uint32*)state.syms1 : (uint32*)state.syms0;
uint32* pStack_top = pStack;
uint max_level = 0;
for ( ; ; )
{
uint level = cur_node_index >> 16;
uint node_index = cur_node_index & 0xFFFF;
uint left_child = syms[node_index].m_left;
uint right_child = syms[node_index].m_right;
uint next_level = (cur_node_index + 0x10000) & 0xFFFF0000;
if (left_child < num_used_syms)
{
max_level = math::maximum(max_level, level);
pCodesizes[syms[left_child].m_left] = static_cast<uint8>(level + 1);
if (right_child < num_used_syms)
{
pCodesizes[syms[right_child].m_left] = static_cast<uint8>(level + 1);
if (pStack == pStack_top) break;
cur_node_index = *--pStack;
}
else
{
cur_node_index = next_level | right_child;
}
}
else
{
if (right_child < num_used_syms)
{
max_level = math::maximum(max_level, level);
pCodesizes[syms[right_child].m_left] = static_cast<uint8>(level + 1);
cur_node_index = next_level | left_child;
}
else
{
*pStack++ = next_level | left_child;
cur_node_index = next_level | right_child;
}
}
}
max_code_size = max_level + 1;
#endif
return true;
}
