private static void BackwardReferencesHashChainFollowChosenPath(ReadOnlySpan <uint> bgra, int cacheBits, Span <ushort> chosenPath, int chosenPathSize, Vp8LHashChain hashChain, Vp8LBackwardRefs backwardRefs)
{
bool useColorCache = cacheBits > 0;
var colorCache = new ColorCache();
int i = 0;
if (useColorCache)
{
colorCache.Init(cacheBits);
}
backwardRefs.Refs.Clear();
for (int ix = 0; ix < chosenPathSize; ix++)
{
int len = chosenPath[ix];
if (len != 1)
{
int offset = hashChain.FindOffset(i);
backwardRefs.Add(PixOrCopy.CreateCopy((uint)offset, (ushort)len));
if (useColorCache)
{
for (int k = 0; k < len; k++)
{
colorCache.Insert(bgra[i + k]);
}
}
i += len;
}
else
{
PixOrCopy v;
int idx = useColorCache ? colorCache.Contains(bgra[i]) : -1;
if (idx >= 0)
{
// useColorCache is true and color cache contains bgra[i]
// Push pixel as a color cache index.
v = PixOrCopy.CreateCacheIdx(idx);
}
else
{
if (useColorCache)
{
colorCache.Insert(bgra[i]);
}
v = PixOrCopy.CreateLiteral(bgra[i]);
}
backwardRefs.Add(v);
i++;
}
}
}
private static void AddSingleLiteral(uint pixel, bool useColorCache, ColorCache colorCache, Vp8LBackwardRefs refs)
{
PixOrCopy v;
if (useColorCache)
{
int key = colorCache.GetIndex(pixel);
if (colorCache.Lookup(key) == pixel)
{
v = PixOrCopy.CreateCacheIdx(key);
}
else
{
v = PixOrCopy.CreateLiteral(pixel);
colorCache.Set((uint)key, pixel);
}
}
else
{
v = PixOrCopy.CreateLiteral(pixel);
}
refs.Add(v);
}