// Decode side is specced and easier, because we don't need to find
// matches using different criteria; we simply read and map. There are
// two things we need to do 'depending':
//
// We may need to support interleave. We don't really, but it's
// convenient to do it here rather than rebuild the vector later.
//
// Cascades may be additive or multiplicitive; this is not inherent in
// the codebook, but set in the code using the codebook. Like
// interleaving, it's easiest to do it here.
// stage==0 -> declarative (set the value)
// stage==1 -> additive
// stage==2 -> multiplicitive
// returns the entry number or -1 on eof
internal int decode(NVorbis.Ogg.BBuffer b)
{
int ptr = 0;
DecodeAux t = decode_tree;
int lok = b.Look(t.tabn);
if (lok >= 0)
{
ptr = t.tab[lok];
b.adv(t.tabl[lok]);
if (ptr <= 0)
{
return(-ptr);
}
}
do
{
switch (b.Read1())
{
case 0:
ptr = t.ptr0[ptr];
break;
case 1:
ptr = t.ptr1[ptr];
break;
case -1:
default:
return(-1);
}
}while (ptr > 0);
return(-ptr);
}
internal int init_decode(StaticCodeBook s)
{
c = s;
entries = s.entries;
dim = s.dim;
valuelist = s.unquantize();
decode_tree = make_decode_tree();
if (decode_tree == null)
{
clear();
return(-1);
}
return(0);
}
// build the decode helper tree from the codewords
internal DecodeAux make_decode_tree()
{
int top = 0;
DecodeAux t = new DecodeAux();
int[] ptr0 = t.ptr0 = new int[entries * 2];
int[] ptr1 = t.ptr1 = new int[entries * 2];
int[] codelist = make_words(c.lengthlist, c.entries);
if (codelist == null)
{
return(null);
}
t.aux = entries * 2;
for (int i = 0; i < entries; i++)
{
if (c.lengthlist[i] > 0)
{
int ptr = 0;
int j;
for (j = 0; j < c.lengthlist[i] - 1; j++)
{
int bit = (int)(((uint)codelist[i] >> j) & 1);
if (bit == 0)
{
if (ptr0[ptr] == 0)
{
ptr0[ptr] = ++top;
}
ptr = ptr0[ptr];
}
else
{
if (ptr1[ptr] == 0)
{
ptr1[ptr] = ++top;
}
ptr = ptr1[ptr];
}
}
if (((((uint)codelist[i]) >> j) & 1) == 0)
{
ptr0[ptr] = -i;
}
else
{
ptr1[ptr] = -i;
}
}
}
t.tabn = Util.ilog(entries) - 4;
if (t.tabn < 5)
{
t.tabn = 5;
}
int n = 1 << t.tabn;
t.tab = new int[n];
t.tabl = new int[n];
for (int i = 0; i < n; i++)
{
int p = 0;
int j = 0;
for (j = 0; j < t.tabn && (p > 0 || j == 0); j++)
{
if ((i & (1 << j)) != 0)
{
p = ptr1[p];
}
else
{
p = ptr0[p];
}
}
t.tab[i] = p; // -code
t.tabl[i] = j; // length
}
return(t);
}
// build the decode helper tree from the codewords
internal DecodeAux make_decode_tree()
{
int top = 0;
DecodeAux t = new DecodeAux();
int[] ptr0 = t.ptr0 = new int[entries * 2];
int[] ptr1 = t.ptr1 = new int[entries * 2];
int[] codelist = make_words(c.lengthlist, c.entries);
if (codelist == null)
return (null);
t.aux = entries * 2;
for (int i = 0; i < entries; i++)
{
if (c.lengthlist[i] > 0)
{
int ptr = 0;
int j;
for (j = 0; j < c.lengthlist[i] - 1; j++)
{
int bit = (int)(((uint)codelist[i] >> j) & 1);
if (bit == 0)
{
if (ptr0[ptr] == 0)
{
ptr0[ptr] = ++top;
}
ptr = ptr0[ptr];
}
else
{
if (ptr1[ptr] == 0)
{
ptr1[ptr] = ++top;
}
ptr = ptr1[ptr];
}
}
if (((((uint)codelist[i]) >> j) & 1) == 0)
{
ptr0[ptr] = -i;
}
else
{
ptr1[ptr] = -i;
}
}
}
t.tabn = Util.ilog(entries) - 4;
if (t.tabn < 5)
t.tabn = 5;
int n = 1 << t.tabn;
t.tab = new int[n];
t.tabl = new int[n];
for (int i = 0; i < n; i++)
{
int p = 0;
int j = 0;
for (j = 0; j < t.tabn && (p > 0 || j == 0); j++)
{
if ((i & (1 << j)) != 0)
{
p = ptr1[p];
}
else
{
p = ptr0[p];
}
}
t.tab[i] = p; // -code
t.tabl[i] = j; // length
}
return (t);
}
internal int init_decode(StaticCodeBook s)
{
c = s;
entries = s.entries;
dim = s.dim;
valuelist = s.unquantize();
decode_tree = make_decode_tree();
if (decode_tree == null)
{
clear();
return (-1);
}
return (0);
}
