/* Appends the symbol statistics from the store. */
static void GetStatistics(ZopfliLZ77Store store, SymbolStats stats)
{
ulong i;
for (i = 0; i < store.size; i++)
{
if (store.dists[(int)i] == 0)
{
stats.litlens[store.litlens[(int)i]]++;
}
else
{
stats.litlens[Symbols.ZopfliGetLengthSymbol(store.litlens[(int)i])]++;
stats.dists[Symbols.ZopfliGetDistSymbol(store.dists[(int)i])]++;
}
}
stats.litlens[256] = 1; /* End symbol. */
stats.CalculateStatistics();
}
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;
}
}
