public void Build(IBitStream B, short blockSize)
{
this.N = (int)B.CountBits;
this.BlockSize = (short)blockSize;
this.InitClasses();
this.Offsets = new BitStream32 ();
IList<int> _L = new ListIFS (15, B);
IList<int> L;
if ((B.CountBits % 15) == 0) {
L = _L;
} else {
int D = _L.Count;
int C = 15 * D;
var ctx = new BitStreamCtx(0);
ctx.Seek(C);
int last_block = (int)B.Read(((int)B.CountBits) - C, ctx);
L = new ListGen<int>(delegate(int a) {
if (a == D) {
return last_block;
} else {
return _L[a];
}
}, D+1);
}
this.AbsRank = new int[(int)Math.Ceiling(((float)L.Count) / this.BlockSize)];
this.AbsOffset = new int[ this.AbsRank.Count ];
int I = 0;
int acc = 0;
for (int i = 0; i < L.Count; i++) {
var u = (short)L[i];
var klass = GetClass(u);
this.EncodeClass(klass);
if (i % this.BlockSize == 0) {
this.AbsRank[I] = acc;
this.AbsOffset[I] = (int)this.Offsets.CountBits;
I++;
}
var numbits = NumBits[klass];
if (numbits > 0) {
int offset = this.GetOffset (u, klass);
this.Offsets.Write (offset, numbits);
}
acc += klass;
}
}
/// <summary>
/// Locates ctx at index. Returns the remaining run_len value if any
/// </summary>
/// <returns>
protected int LocateAt(int index, BitStreamCtx ctx)
{
if (index == -1) {
ctx.Seek (0);
return 0;
}
int offset_index = index / this.BlockSize;
if (offset_index == 0) {
ctx.Seek (0);
} else {
ctx.Seek (this.Offsets [offset_index - 1]);
}
int left = 1 + index - offset_index * this.BlockSize;
int run_len = 0;
for (int i = 0; i < left;) {
if (run_len > 0) {
// run_len--;
i += run_len;
run_len = 0;
if (left < i) {
run_len = i - left;
i = left;
}
} else {
var res = this.GetNext (ctx);
if (res == 1) {
run_len = this.GetNext (ctx) - 1;
}
i++;
}
}
// Console.WriteLine ("** index: {0}, run_len: {1}, left: {2}", index, run_len, left);
return run_len;
}
public void PrintDebug()
{
var ctx = new BitStreamCtx ();
ctx.Seek (0);
int i = 0;
while (ctx.Offset < this.Stream.CountBits) {
var c = this.Coder.Decode (this.Stream, ctx);
Console.WriteLine ("=> i: {0}, c: {1}", i, c);
}
}
/// <summary>
/// Unlocked Select1 useful
/// </summary>
int BackendSelect1(int rank, BitStreamCtx ctx)
{
if (rank < 1) {
return -1;
}
this.ResetReader();
int start_index = (rank - 1) / this.B;
int acc;
int left;
if (start_index == 0) {
acc = AccStart;
ctx.Seek (0);
left = rank;
} else {
acc = this.Samples[start_index - 1];
ctx.Seek (this.Offsets[start_index - 1]);
left = rank - start_index * this.B;
}
// int start_acc = acc;
for (int i = 0; i < left; i++) {
int read = this.ReadNext(ctx);
acc += read;
}
return acc;
}
int BackendAccessRank1(int pos, out int found_pos, BitStreamCtx ctx)
{
if (pos < 0) {
found_pos = -1;
return 0;
}
this.ResetReader ();
int start_index = -1;
if (this.Samples.Count > 0) {
start_index = GenericSearch.FindFirst<int> (pos, this.Samples);
}
int count;
if (start_index < 0) {
ctx.Seek (0);
count = Math.Min (this.B, this.M);
return this.SeqAccessRank1 (AccStart, pos, count, out found_pos, ctx);
}
ctx.Seek (this.Offsets[start_index]);
int rel_rank = (start_index + 1) * this.B;
count = Math.Min (this.B, this.M - rel_rank);
return rel_rank + this.SeqAccessRank1 (this.Samples[start_index], pos, count, out found_pos, ctx);
}
/// <summary>
/// Extract 'count' differences starting from 'start_index', it saves the output in 'output'.
/// Returns the previous absolute value to start_index (start_index - 1), i.e. the reference
/// </summary>
public int ExtractFrom(int start_index, int count, IList<int> output)
{
int acc;
BitStreamCtx ctx = new BitStreamCtx ();
if (start_index == 0) {
this.ResetReader ();
acc = -1;
ctx.Seek (0);
} else {
acc = this.BackendSelect1 (start_index, ctx);
}
for (int i = 0; i < count; i++) {
int val = this.ReadNext (ctx);
if (i < output.Count) {
output[i] = val;
} else {
output.Add (val);
}
}
return acc;
}
