static void ZopfliLZ77OptimalFixed(ZopfliBlockState s,
byte[] InFile,
ulong instart, ulong inend,
ZopfliLZ77Store store)
{
/* Dist to get to here with smallest cost. */
ulong blocksize = inend - instart;
ushort[] length_array = new ushort[blocksize + 1];
List <ushort> path = new List <ushort>();
path.Add(0);
ZopfliHash h = new ZopfliHash();
float[] costs = new float[blocksize + 1];
SymbolStats stats = new SymbolStats();
s.blockstart = (int)instart;
s.blockend = (int)inend;
/* Shortest path for fixed tree This one should give the shortest possible
* result for fixed tree, no repeated runs are needed since the tree is known. */
LZ77OptimalRun(s, InFile, (int)instart, (int)inend, path,
length_array, stats, store, h, costs, true);
}
/*
* Does a single run for ZopfliLZ77Optimal. For good compression, repeated runs
* with updated statistics should be performed.
* s: the block state
* in: the input data array
* instart: where to start
* inend: where to stop (not inclusive)
* path: pointer to dynamically allocated memory to store the path
* pathsize: pointer to the size of the dynamic path array
* length_array: array of size (inend - instart) used to store lengths
* costmodel: function to use as the cost model for this squeeze run
* costcontext: abstract context for the costmodel function
* store: place to output the LZ77 data
* returns the cost that was, according to the costmodel, needed to get to the end.
* This is not the actual cost.
*/
static double LZ77OptimalRun(ZopfliBlockState s,
byte[] InFile, int instart, int inend, List <ushort> path,
ushort[] length_array, SymbolStats stats, ZopfliLZ77Store store,
ZopfliHash h, float[] costs, bool fixedcosts)
{
double cost = GetBestLengths(s, InFile, instart, inend, stats, length_array, h, costs, fixedcosts);
ulong pathsize = 0;
path.Clear();
TraceBackwards((ulong)(inend - instart), length_array, path, ref pathsize);
FollowPath(s, InFile, instart, inend, path, pathsize, store, h);
Debug.Assert(cost < ZOPFLI_LARGE_FLOAT);
return(cost);
}
static void ZopfliLZ77Optimal(ZopfliBlockState s,
byte[] InFile, int instart, int inend,
int numiterations,
ZopfliLZ77Store store)
{
/* Dist to get to here with smallest cost. */
int blocksize = inend - instart;
ushort[] length_array = new ushort[blocksize + 1];
List <ushort> path = new List <ushort>();
ZopfliLZ77Store currentstore = new ZopfliLZ77Store(InFile);
ZopfliHash h = new ZopfliHash();
SymbolStats stats = new SymbolStats();
SymbolStats beststats = new SymbolStats();
SymbolStats laststats = new SymbolStats();
int i;
float[] costs = new float [blocksize + 1];
double cost;
double bestcost = ZOPFLI_LARGE_FLOAT;
double lastcost = 0;
/* Try randomizing the costs a bit once the size stabilizes. */
RanState ran_state = new RanState();
int lastrandomstep = -1;
/* Do regular deflate, then loop multiple shortest path runs, each time using
* the statistics of the previous run. */
/* Initial run. */
ZopfliLZ77Greedy(s, InFile, instart, inend, currentstore, h);
GetStatistics(currentstore, stats);
/* Repeat statistics with each time the cost model from the previous stat
* run. */
for (i = 0; i < numiterations; i++)
{
currentstore.ResetStore(InFile);
LZ77OptimalRun(s, InFile, instart, inend, path, length_array, stats,
currentstore, h, costs, false);
cost = ZopfliCalculateBlockSize(currentstore, 0, currentstore.size, 2);
if (Globals.verbose_more > 0 || (Globals.verbose > 0 && cost < bestcost))
{
Console.WriteLine("Iteration " + i + ": " + cost + " bit");
}
if (cost < bestcost)
{
/* Copy to the output store. */
ZopfliCopyLZ77Store(currentstore, store);
CopyStats(stats, ref beststats);
bestcost = cost;
}
CopyStats(stats, ref laststats);
ClearStatFreqs(stats);
GetStatistics(currentstore, stats);
if (lastrandomstep != -1)
{
/* This makes it converge slower but better. Do it only once the
* randomness kicks in so that if the user does few iterations, it gives a
* better result sooner. */
AddWeighedStatFreqs(stats, 1.0, laststats, 0.5, stats);
stats.CalculateStatistics();
}
if (i > 5 && cost == lastcost)
{
CopyStats(beststats, ref stats);
RandomizeStatFreqs(ran_state, stats);
stats.CalculateStatistics();
lastrandomstep = i;
}
lastcost = cost;
}
}
static void FollowPath(ZopfliBlockState s,
byte[] InFile, int instart, int inend,
List <ushort> path, ulong pathsize,
ZopfliLZ77Store store, ZopfliHash h)
{
int i, j, pos;
int windowstart = instart > ZopfliHash.ZOPFLI_WINDOW_SIZE
? instart - ZopfliHash.ZOPFLI_WINDOW_SIZE : 0;
ulong total_length_test = 0;
if (instart == inend)
{
return;
}
h.ZopfliResetHash();
h.ZopfliWarmupHash(InFile, windowstart, inend);
for (i = windowstart; i < instart; i++)
{
h.ZopfliUpdateHash(InFile, i, inend);
}
pos = instart;
for (i = 0; i < (int)pathsize; i++)
{
ushort length = path[i];
ushort dummy_length = 0;
ushort dist = 0;
Debug.Assert(pos < inend);
h.ZopfliUpdateHash(InFile, pos, inend);
/* Add to output. */
if (length >= ZOPFLI_MIN_MATCH)
{
/* Get the distance by recalculating longest match. The found length
* should match the length from the path. */
ZopfliFindLongestMatch(s, h, InFile, pos, inend, length, null,
ref dist, ref dummy_length);
Debug.Assert(!(dummy_length != length && length > 2 && dummy_length > 2));
ZopfliVerifyLenDist(InFile, inend, pos, dist, length);
ZopfliStoreLitLenDist(length, dist, pos, store);
total_length_test += length;
}
else
{
length = 1;
ZopfliStoreLitLenDist(InFile[pos], 0, pos, store);
total_length_test++;
}
Debug.Assert(pos + length <= inend);
for (j = 1; j < length; j++)
{
h.ZopfliUpdateHash(InFile, pos + j, inend);
}
pos += length;
}
}
/*
* Performs the forward pass for "squeeze". Gets the most optimal length to reach
* every byte from a previous byte, using cost calculations.
* s: the ZopfliBlockState
* in: the input data array
* instart: where to start
* inend: where to stop (not inclusive)
* costmodel: function to calculate the cost of some lit/len/dist pair.
* costcontext: abstract context for the costmodel function
* length_array: output array of size (inend - instart) which will receive the best
* length to reach this byte from a previous byte.
* returns the cost that was, according to the costmodel, needed to get to the end.
*/
static double GetBestLengths(ZopfliBlockState s,
byte[] InFile,
int instart, int inend,
SymbolStats stats,
ushort[] length_array,
ZopfliHash h, float[] costs, bool fixedcosts)
{
/* Best cost to get here so far. */
ulong blocksize = (ulong)(inend - instart);
ulong i, k, kend;
ushort leng = 0; //bogus value
ushort dist = 0; //bogusvalue
ushort[] sublen = new ushort[259];
ulong windowstart = (ulong)(instart > ZopfliHash.ZOPFLI_WINDOW_SIZE
? instart - ZopfliHash.ZOPFLI_WINDOW_SIZE : 0);
double result;
double mincost = GetCostModelMinCost(stats);
double mincostaddcostj;
if (instart == inend)
{
return(0);
}
h.ZopfliResetHash();
h.ZopfliWarmupHash(InFile, (int)windowstart, inend);
for (i = windowstart; i < (ulong)instart; i++)
{
h.ZopfliUpdateHash(InFile, (int)i, inend);
}
Array.Fill(costs, (float)Compress.ZOPFLI_LARGE_FLOAT);
costs[0] = 0; /* Because it's the start. */
length_array[0] = 0;
for (i = (ulong)instart; i < (ulong)inend; i++)
{
ulong j = i - (ulong)instart; /* Index in the costs array and length_array. */
h.ZopfliUpdateHash(InFile, (int)i, inend);
/* If we're in a long repetition of the same character and have more than
* ZOPFLI_MAX_MATCH characters before and after our position. */
if (h.same[i & ZopfliHash.ZOPFLI_WINDOW_MASK] > ZOPFLI_MAX_MATCH * 2 &&
(int)i > instart + ZOPFLI_MAX_MATCH + 1 &&
i + ZOPFLI_MAX_MATCH * 2 + 1 < (ulong)inend &&
h.same[(i - ZOPFLI_MAX_MATCH) & ZopfliHash.ZOPFLI_WINDOW_MASK]
> ZOPFLI_MAX_MATCH)
{
double symbolcost;
if (fixedcosts)
{
symbolcost = GetCostFixed(ZOPFLI_MAX_MATCH, 1);
}
else
{
symbolcost = GetCostStat(ZOPFLI_MAX_MATCH, 1, stats);
}
/* Set the length to reach each one to ZOPFLI_MAX_MATCH, and the cost to
* the cost corresponding to that length. Doing this, we skip
* ZOPFLI_MAX_MATCH values to avoid calling ZopfliFindLongestMatch. */
for (k = 0; k < ZOPFLI_MAX_MATCH; k++)
{
costs[j + ZOPFLI_MAX_MATCH] = costs[j] + (float)symbolcost;
length_array[j + ZOPFLI_MAX_MATCH] = ZOPFLI_MAX_MATCH;
i++;
j++;
h.ZopfliUpdateHash(InFile, (int)i, inend);
}
}
ZopfliFindLongestMatch(s, h, InFile, (int)i, inend, ZOPFLI_MAX_MATCH, sublen,
ref dist, ref leng);
/* Literal. */
if (i + 1 <= (ulong)inend)
{
double newCost;
if (fixedcosts)
{
newCost = GetCostFixed(InFile[i], 0) + costs[j];
}
else
{
newCost = GetCostStat(InFile[i], 0, stats) + costs[j];
}
Debug.Assert(newCost >= 0);
if (newCost < costs[j + 1])
{
costs[j + 1] = (float)newCost;
length_array[j + 1] = 1;
}
}
/* Lengths. */
kend = zopfli_min(leng, (ulong)inend - i);
mincostaddcostj = mincost + costs[j];
for (k = 3; k <= kend; k++)
{
double newCost;
/* Calling the cost model is expensive, avoid this if we are already at
* the minimum possible cost that it can return. */
if (costs[j + k] <= mincostaddcostj)
{
continue;
}
if (fixedcosts)
{
newCost = GetCostFixed((int)k, sublen[k]) + costs[j];
}
else
{
newCost = GetCostStat((int)k, sublen[k], stats) + costs[j];
}
Debug.Assert(newCost >= 0);
if (newCost < costs[j + k])
{
Debug.Assert(k <= ZOPFLI_MAX_MATCH);
costs[j + k] = (float)newCost;
length_array[j + k] = (ushort)k;
}
}
}
Debug.Assert(costs[blocksize] >= 0);
result = costs[blocksize];
return(result);
}
