protected override int DecodeClass(int i, CtxCache ctx)
{
int klass;
// Console.WriteLine("XXXXX i: {0}, offset: {1}", i, ctx.Offset);
if (ctx.Offset == -1 || ctx.prev_item + 1 != i) {
klass = this.LI.GetItem(i, ctx);
} else {
klass = this.LI.GetNext(ctx);
}
ctx.prev_item = i;
// var klass = this.Klasses[i];
// var klass = this.LI[i];
if ((0x1 & klass) == 0x1) { // check for odd
klass >>= 1; // removing encding as odd
klass = 15 - klass; // going right to left
}
else {
klass >>= 1; // removing
}
return klass;
}
int Rank1AccessBackend(int pos, out bool last_bit)
{
// in advance, we use pos as a simple counter of the remaining positions
int blockIndex = pos / 15 / this.BlockSize;
int classIndex = blockIndex * this.BlockSize;
int rank = this.AbsRank[blockIndex];
pos -= classIndex * 15;
int offset = this.AbsOffset[blockIndex];
int klass;
var ctx = new CtxCache (-1);
if (pos >= 15) {
for (; pos >= 15; pos -= 15) {
klass = this.DecodeClass (classIndex, ctx);
classIndex++;
rank += klass;
int numbits = NumBits[klass];
offset += numbits;
}
}
klass = this.DecodeClass (classIndex, ctx);
uint block = (uint)this.ReadBlock (klass, offset);
last_bit = BitAccess.GetBit ((int)block, pos);
rank += BitAccess.Rank1 (block, pos);
return rank;
}
protected virtual int DecodeClass(int i, CtxCache ctx)
{
var klass = this.Klasses[i];
return klass;
}
public override int Select1(int rank)
{
if (rank < 1) {
return -1;
}
int blockIndex = GenericSearch.FindFirst<int> (rank, this.AbsRank);
if (this.AbsRank[blockIndex] == rank) {
blockIndex--;
}
int classIndex = blockIndex * this.BlockSize;
rank -= this.AbsRank[blockIndex];
int pos = classIndex * 15;
int offset = this.AbsOffset[blockIndex];
int klass;
var ctx = new CtxCache (-1);
while (rank > 0) {
klass = this.DecodeClass (classIndex, ctx);
if (rank - klass <= 0) {
break;
}
classIndex++;
pos += 15;
rank -= klass;
int numbits = NumBits[klass];
offset += numbits;
}
if (rank > 0) {
klass = this.DecodeClass (classIndex, ctx);
uint block = (uint)this.ReadBlock (klass, offset);
// Console.WriteLine ("rank: {0}, pos: {1}, block: {2}, klass: {3}, offset: {4}",
// rank, pos, block, klass, offset);
pos += BitAccess.Select1 (block, rank);
}
return pos;
}
