/* HUF_buildTree():
* Takes the huffNode array sorted by HUF_sort() and builds an unlimited-depth Huffman tree.
*
* @param huffNode The array sorted by HUF_sort(). Builds the Huffman tree in this array.
* @param maxSymbolValue The maximum symbol value.
* @return The smallest node in the Huffman tree (by count).
*/
private static int HUF_buildTree(nodeElt_s *huffNode, uint maxSymbolValue)
{
nodeElt_s *huffNode0 = huffNode - 1;
int nonNullRank;
int lowS, lowN;
int nodeNb = (255 + 1);
int n, nodeRoot;
nonNullRank = (int)(maxSymbolValue);
while (huffNode[nonNullRank].count == 0)
{
nonNullRank--;
}
lowS = nonNullRank;
nodeRoot = nodeNb + lowS - 1;
lowN = nodeNb;
huffNode[nodeNb].count = huffNode[lowS].count + huffNode[lowS - 1].count;
huffNode[lowS].parent = huffNode[lowS - 1].parent = (ushort)(nodeNb);
nodeNb++;
lowS -= 2;
for (n = nodeNb; n <= nodeRoot; n++)
{
huffNode[n].count = (uint)(1U << 30);
}
huffNode0[0].count = (uint)(1U << 31);
while (nodeNb <= nodeRoot)
{
int n1 = (huffNode[lowS].count < huffNode[lowN].count) ? lowS-- : lowN++;
int n2 = (huffNode[lowS].count < huffNode[lowN].count) ? lowS-- : lowN++;
huffNode[nodeNb].count = huffNode[n1].count + huffNode[n2].count;
huffNode[n1].parent = huffNode[n2].parent = (ushort)(nodeNb);
nodeNb++;
}
huffNode[nodeRoot].nbBits = 0;
for (n = nodeRoot - 1; n >= (255 + 1); n--)
{
huffNode[n].nbBits = (byte)(huffNode[huffNode[n].parent].nbBits + 1);
}
for (n = 0; n <= nonNullRank; n++)
{
huffNode[n].nbBits = (byte)(huffNode[huffNode[n].parent].nbBits + 1);
}
return(nonNullRank);
}
public static nuint HUF_buildCTable_wksp(HUF_CElt_s *tree, uint *count, uint maxSymbolValue, uint maxNbBits, void *workSpace, nuint wkspSize)
{
HUF_buildCTable_wksp_tables *wksp_tables = (HUF_buildCTable_wksp_tables *)(workSpace);
nodeElt_s *huffNode0 = (nodeElt_s *)wksp_tables->huffNodeTbl;
nodeElt_s *huffNode = huffNode0 + 1;
int nonNullRank;
if (((nuint)(workSpace) & 3) != 0)
{
return(unchecked ((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC)));
}
if (wkspSize < (nuint)(sizeof(HUF_buildCTable_wksp_tables)))
{
return(unchecked ((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_workSpace_tooSmall)));
}
if (maxNbBits == 0)
{
maxNbBits = 11;
}
if (maxSymbolValue > 255)
{
return(unchecked ((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_maxSymbolValue_tooLarge)));
}
memset((void *)(huffNode0), (0), ((nuint)(sizeof(nodeElt_s) * 512)));
HUF_sort(huffNode, count, maxSymbolValue, (rankPos *)wksp_tables->rankPosition);
nonNullRank = HUF_buildTree(huffNode, maxSymbolValue);
maxNbBits = HUF_setMaxHeight(huffNode, (uint)(nonNullRank), maxNbBits);
if (maxNbBits > 12)
{
return(unchecked ((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC)));
}
HUF_buildCTableFromTree(tree, huffNode, nonNullRank, maxSymbolValue, maxNbBits);
return(maxNbBits);
}
/**
* HUF_buildCTableFromTree():
* Build the CTable given the Huffman tree in huffNode.
*
* @param[out] CTable The output Huffman CTable.
* @param huffNode The Huffman tree.
* @param nonNullRank The last and smallest node in the Huffman tree.
* @param maxSymbolValue The maximum symbol value.
* @param maxNbBits The exact maximum number of bits used in the Huffman tree.
*/
private static void HUF_buildCTableFromTree(HUF_CElt_s *CTable, nodeElt_s *huffNode, int nonNullRank, uint maxSymbolValue, uint maxNbBits)
{
int n;
ushort *nbPerRank = stackalloc ushort[13];
memset(nbPerRank, 0, sizeof(ushort) * 13);
ushort *valPerRank = stackalloc ushort[13];
memset(valPerRank, 0, sizeof(ushort) * 13);
int alphabetSize = (int)(maxSymbolValue + 1);
for (n = 0; n <= nonNullRank; n++)
{
nbPerRank[huffNode[n].nbBits]++;
}
{
ushort min = 0;
for (n = (int)(maxNbBits); n > 0; n--)
{
valPerRank[n] = min;
min += (ushort)(nbPerRank[n]);
min >>= 1;
}
}
for (n = 0; n < alphabetSize; n++)
{
CTable[huffNode[n].@byte].nbBits = huffNode[n].nbBits;
}
for (n = 0; n < alphabetSize; n++)
{
CTable[n].val = valPerRank[CTable[n].nbBits]++;
}
}
/**
* HUF_sort():
* Sorts the symbols [0, maxSymbolValue] by count[symbol] in decreasing order.
*
* @param[out] huffNode Sorted symbols by decreasing count. Only members `.count` and `.byte` are filled.
* Must have (maxSymbolValue + 1) entries.
* @param[in] count Histogram of the symbols.
* @param[in] maxSymbolValue Maximum symbol value.
* @param rankPosition This is a scratch workspace. Must have RANK_POSITION_TABLE_SIZE entries.
*/
private static void HUF_sort(nodeElt_s *huffNode, uint *count, uint maxSymbolValue, rankPos *rankPosition)
{
int n;
int maxSymbolValue1 = (int)(maxSymbolValue) + 1;
memset((void *)(rankPosition), (0), ((nuint)(sizeof(rankPos)) * 32));
for (n = 0; n < maxSymbolValue1; ++n)
{
uint lowerRank = BIT_highbit32(count[n] + 1);
rankPosition[lowerRank].@base++;
}
assert(rankPosition[32 - 1].@base == 0);
for (n = 32 - 1; n > 0; --n)
{
rankPosition[n - 1].@base += rankPosition[n].@base;
rankPosition[n - 1].curr = rankPosition[n - 1].@base;
}
for (n = 0; n < maxSymbolValue1; ++n)
{
uint c = count[n];
uint r = BIT_highbit32(c + 1) + 1;
uint pos = rankPosition[r].curr++;
while ((pos > rankPosition[r].@base) && (c > huffNode[pos - 1].count))
{
huffNode[pos] = huffNode[pos - 1];
pos--;
}
huffNode[pos].count = c;
huffNode[pos].@byte = (byte)(n);
}
}
/**
* HUF_setMaxHeight():
* Enforces maxNbBits on the Huffman tree described in huffNode.
*
* It sets all nodes with nbBits > maxNbBits to be maxNbBits. Then it adjusts
* the tree to so that it is a valid canonical Huffman tree.
*
* @pre The sum of the ranks of each symbol == 2^largestBits,
* where largestBits == huffNode[lastNonNull].nbBits.
* @post The sum of the ranks of each symbol == 2^largestBits,
* where largestBits is the return value <= maxNbBits.
*
* @param huffNode The Huffman tree modified in place to enforce maxNbBits.
* @param lastNonNull The symbol with the lowest count in the Huffman tree.
* @param maxNbBits The maximum allowed number of bits, which the Huffman tree
* may not respect. After this function the Huffman tree will
* respect maxNbBits.
* @return The maximum number of bits of the Huffman tree after adjustment,
* necessarily no more than maxNbBits.
*/
private static uint HUF_setMaxHeight(nodeElt_s *huffNode, uint lastNonNull, uint maxNbBits)
{
uint largestBits = huffNode[lastNonNull].nbBits;
if (largestBits <= maxNbBits)
{
return(largestBits);
}
{
int totalCost = 0;
uint baseCost = (uint)(1 << (int)(largestBits - maxNbBits));
int n = (int)(lastNonNull);
while (huffNode[n].nbBits > maxNbBits)
{
totalCost += (int)((int)(baseCost - (uint)((1 << (int)(largestBits - huffNode[n].nbBits)))));
huffNode[n].nbBits = (byte)(maxNbBits);
n--;
}
assert(huffNode[n].nbBits <= maxNbBits);
while (huffNode[n].nbBits == maxNbBits)
{
--n;
}
assert(((uint)totalCost & (baseCost - 1)) == 0);
totalCost >>= (int)(largestBits - maxNbBits);
assert(totalCost > 0);
{
uint noSymbol = 0xF0F0F0F0;
uint *rankLast = stackalloc uint[14];
memset((void *)(rankLast), (0xF0), ((nuint)(sizeof(uint) * 14)));
{
uint currentNbBits = maxNbBits;
int pos;
for (pos = n; pos >= 0; pos--)
{
if (huffNode[pos].nbBits >= currentNbBits)
{
continue;
}
currentNbBits = huffNode[pos].nbBits;
rankLast[maxNbBits - currentNbBits] = (uint)(pos);
}
}
while (totalCost > 0)
{
uint nBitsToDecrease = BIT_highbit32((uint)(totalCost)) + 1;
for (; nBitsToDecrease > 1; nBitsToDecrease--)
{
uint highPos = rankLast[nBitsToDecrease];
uint lowPos = rankLast[nBitsToDecrease - 1];
if (highPos == noSymbol)
{
continue;
}
if (lowPos == noSymbol)
{
break;
}
{
uint highTotal = huffNode[highPos].count;
uint lowTotal = 2 * huffNode[lowPos].count;
if (highTotal <= lowTotal)
{
break;
}
}
}
assert(rankLast[nBitsToDecrease] != noSymbol || nBitsToDecrease == 1);
while ((nBitsToDecrease <= 12) && (rankLast[nBitsToDecrease] == noSymbol))
{
nBitsToDecrease++;
}
assert(rankLast[nBitsToDecrease] != noSymbol);
totalCost -= 1 << (int)(nBitsToDecrease - 1);
huffNode[rankLast[nBitsToDecrease]].nbBits++;
if (rankLast[nBitsToDecrease - 1] == noSymbol)
{
rankLast[nBitsToDecrease - 1] = rankLast[nBitsToDecrease];
}
if (rankLast[nBitsToDecrease] == 0)
{
rankLast[nBitsToDecrease] = noSymbol;
}
else
{
rankLast[nBitsToDecrease]--;
if (huffNode[rankLast[nBitsToDecrease]].nbBits != maxNbBits - nBitsToDecrease)
{
rankLast[nBitsToDecrease] = noSymbol;
}
}
}
while (totalCost < 0)
{
if (rankLast[1] == noSymbol)
{
while (huffNode[n].nbBits == maxNbBits)
{
n--;
}
huffNode[n + 1].nbBits--;
assert(n >= 0);
rankLast[1] = (uint)(n + 1);
totalCost++;
continue;
}
huffNode[rankLast[1] + 1].nbBits--;
rankLast[1]++;
totalCost++;
}
}
}
return(maxNbBits);
}
