protected override (MetaBlock, BrotliGlobalState) Transform(MetaBlock.Compressed original, BrotliGlobalState state, BrotliCompressionParameters parameters)
{
if (original.Data.InsertCopyCommands.Count <= 1 || original.Data.BlockSwitchCommands[Category.InsertCopy].Count > 0)
{
return(original, state);
}
var builder = new CompressedMetaBlockBuilder(original, state);
var icBlocks = builder.BlockTypes[Category.InsertCopy];
var icCommands = builder.GetTotalBlockLength(Category.InsertCopy);
icBlocks.SetInitialLength(icCommands / 2)
.AddFinalBlock(1);
return(builder.Build(parameters));
}
protected override (MetaBlock, BrotliGlobalState) Transform(MetaBlock.Compressed original, BrotliGlobalState state, BrotliCompressionParameters parameters)
{
var builder = new CompressedMetaBlockBuilder(original, state);
var literals = new List <Literal>(builder.GetTotalBlockLength(Category.Literal));
var lengthCodes = new List <InsertCopyLengthCode>(builder.GetTotalBlockLength(Category.InsertCopy));
var distanceCodes = new List <DistanceCode>(builder.GetTotalBlockLength(Category.Distance));
var distanceFreq = new FrequencyList <DistanceCode>();
var validDistanceCodes = new List <DistanceCode>(5);
foreach (var command in original.Data.InsertCopyCommands)
{
literals.AddRange(command.Literals);
state.OutputLiterals(command.Literals);
if (command.CopyDistance == DistanceInfo.EndsAfterLiterals)
{
lengthCodes.Add(command.Lengths.MakeCode(ImplicitDistanceCodeZero.PreferEnabled));
break;
}
if (!command.CopyDistance.FindCodes(original.Header.DistanceParameters, state, validDistanceCodes))
{
lengthCodes.Add(command.Lengths.MakeCode(ImplicitDistanceCodeZero.ForceEnabled));
}
else
{
DistanceCode distanceCode;
if (command.CopyDistance == DistanceInfo.ExplicitCodeZero)
{
distanceCode = DistanceCode.Zero;
}
else
{
distanceCode = validDistanceCodes.Count > 1 ? parameters.DistanceCodePicker(validDistanceCodes, distanceFreq) : validDistanceCodes[0];
}
distanceFreq.Add(distanceCode);
distanceCodes.Add(distanceCode);
lengthCodes.Add(command.Lengths.MakeCode(ImplicitDistanceCodeZero.Disable));
}
}
var origLitCtxMap = builder.LiteralCtxMap;
if (origLitCtxMap.TreeCount == 1)
{
Split(builder, Category.Literal, literals, 512, 400.0);
builder.UseSameLiteralContextMode(LiteralContextMode.UTF8);
builder.LiteralCtxMap = new ContextMapBuilder.Literals(builder).RepeatFirstBlockType(true).Build();
}
else
{
var literalContextMap = Enumerable.Range(0, origLitCtxMap.ContextsPerBlockType).Select(index => origLitCtxMap.DetermineTreeID(0, index)).ToArray();
var literalContextMode = builder.LiteralContextModes[0];
var literalBuffer = RingBufferFast <byte> .From(0, 0);
Split(builder, Category.Literal, literals, 512, 400.0, new BlockSplitter <Literal> .ContextInfo(literalContextMap, literal => {
literalBuffer.Push(literal.Value);
return(literalContextMode.DetermineContextID(literalBuffer.Front, literalBuffer.Back));
}));
builder.UseSameLiteralContextMode(literalContextMode);
builder.LiteralCtxMap = new ContextMapBuilder.Literals(builder).Set(0, literalContextMap).RepeatFirstBlockType(true).Build();
}
Split(builder, Category.InsertCopy, lengthCodes, 1024, 500.0);
Split(builder, Category.Distance, distanceCodes, 512, 100.0);
builder.DistanceCtxMap = new ContextMapBuilder.Distances(builder).RepeatFirstBlockType(true).Build();
return(builder.Build(parameters));
}
private void TestBlockSplits(CompressedMetaBlockBuilder builder, BrotliCompressionParameters parameters, MetaBlockSizeTracker tracker, Category category)
{
int totalBlockLength = builder.GetTotalBlockLength(category);
if (totalBlockLength == 0)
{
return;
}
int step = Math.Max(1, (int)Math.Floor(Math.Log(totalBlockLength, 1.15)));
int stepTwice = step * 2;
if (totalBlockLength < stepTwice)
{
return;
}
var lengths = new List <int> {
totalBlockLength
};
var queue = new Queue <int>();
queue.Enqueue(0);
while (queue.TryDequeue(out int leftIndex))
{
if (lengths[leftIndex] < stepTwice)
{
continue;
}
int rightIndex = leftIndex + 1;
lengths.Insert(rightIndex, lengths[leftIndex] - step);
lengths[leftIndex] = step;
ApplyBlockSplit(builder.BlockTypes[category], lengths);
PrepareContextMap(builder, category, lengths.Count);
tracker.Test(builder, parameters);
while (lengths[leftIndex] + step < lengths[rightIndex] && lengths[rightIndex] >= stepTwice)
{
lengths[leftIndex] += step;
lengths[rightIndex] -= step;
ApplyBlockSplit(builder.BlockTypes[category], lengths);
PrepareContextMap(builder, category, lengths.Count);
tracker.Test(builder, parameters);
}
var smallest = tracker.Smallest;
if (smallest == null)
{
return;
}
var mb = smallest.Value.Item1;
int prev = lengths.Count;
lengths.Clear();
lengths.Add(mb.Header.BlockTypes[category].InitialLength);
lengths.AddRange(mb.Data.BlockSwitchCommands[category].Select(command => command.Length));
var finalLength = totalBlockLength - lengths.Sum();
if (finalLength > 0)
{
lengths.Add(totalBlockLength - lengths.Sum());
}
if (lengths.Count >= prev)
{
queue.Enqueue(leftIndex);
queue.Enqueue(rightIndex);
}
}
}
