// Called with number of bytes left to write in window at least 258
// (the maximum string length) and number of input bytes available
// at least ten. The ten bytes are six bytes for the longest length/
// distance pair plus four bytes for overloading the bit buffer.
internal static int InflateFast(int bl, int bd, int[] tl, int tl_index, int[] td, int td_index, InflateBlocks s,
ZlibCodec z)
{
int t; // temporary pointer
int[] tp; // temporary pointer
int tp_index; // temporary pointer
int e; // extra bits or operation
int b; // bit buffer
int k; // bits in bit buffer
int p; // input data pointer
int n; // bytes available there
int q; // output window write pointer
int m; // bytes to end of window or read pointer
int ml; // mask for literal/length tree
int md; // mask for distance tree
int c; // bytes to copy
int d; // distance back to copy from
int r; // copy source pointer
int tp_index_t_3; // (tp_index+t)*3
// load input, output, bit values
p = z.NextIn;
n = z.AvailableBytesIn;
b = s.bitb;
k = s.bitk;
q = s.writeAt;
m = q < s.readAt ? s.readAt - q - 1 : s.end - q;
// initialize masks
ml = InternalInflateConstants.InflateMask[bl];
md = InternalInflateConstants.InflateMask[bd];
// do until not enough input or output space for fast loop
do
{
// assume called with m >= 258 && n >= 10
// get literal/length code
while (k < 20)
{
// max bits for literal/length code
n--;
b |= (z.InputBuffer[p++] & 0xff) << k;
k += 8;
}
t = b & ml;
tp = tl;
tp_index = tl_index;
tp_index_t_3 = (tp_index + t) * 3;
if ((e = tp[tp_index_t_3]) == 0)
{
b >>= tp[tp_index_t_3 + 1];
k -= tp[tp_index_t_3 + 1];
s.window[q++] = (byte)tp[tp_index_t_3 + 2];
m--;
continue;
}
do
{
b >>= tp[tp_index_t_3 + 1];
k -= tp[tp_index_t_3 + 1];
if ((e & 16) != 0)
{
e &= 15;
c = tp[tp_index_t_3 + 2] + (b & InternalInflateConstants.InflateMask[e]);
b >>= e;
k -= e;
// decode distance base of block to copy
while (k < 15)
{
// max bits for distance code
n--;
b |= (z.InputBuffer[p++] & 0xff) << k;
k += 8;
}
t = b & md;
tp = td;
tp_index = td_index;
tp_index_t_3 = (tp_index + t) * 3;
e = tp[tp_index_t_3];
do
{
b >>= tp[tp_index_t_3 + 1];
k -= tp[tp_index_t_3 + 1];
if ((e & 16) != 0)
{
// get extra bits to add to distance base
e &= 15;
while (k < e)
{
// get extra bits (up to 13)
n--;
b |= (z.InputBuffer[p++] & 0xff) << k;
k += 8;
}
d = tp[tp_index_t_3 + 2] + (b & InternalInflateConstants.InflateMask[e]);
b >>= e;
k -= e;
// do the copy
m -= c;
if (q >= d)
{
// offset before dest
// just copy
r = q - d;
if (q - r > 0 && 2 > q - r)
{
s.window[q++] = s.window[r++]; // minimum count is three,
s.window[q++] = s.window[r++]; // so unroll loop a little
c -= 2;
}
else
{
Array.Copy(s.window, r, s.window, q, 2);
q += 2;
r += 2;
c -= 2;
}
}
else
{
// else offset after destination
r = q - d;
do
{
r += s.end; // force pointer in window
} while (r < 0); // covers invalid distances
e = s.end - r;
if (c > e)
{
// if source crosses,
c -= e; // wrapped copy
if (q - r > 0 && e > q - r)
{
do
{
s.window[q++] = s.window[r++];
} while (--e != 0);
}
else
{
Array.Copy(s.window, r, s.window, q, e);
q += e;
}
r = 0; // copy rest from start of window
}
}
// copy all or what's left
if (q - r > 0 && c > q - r)
{
do
{
s.window[q++] = s.window[r++];
} while (--c != 0);
}
else
{
Array.Copy(s.window, r, s.window, q, c);
q += c;
}
break;
}
if ((e & 64) == 0)
{
t += tp[tp_index_t_3 + 2];
t += b & InternalInflateConstants.InflateMask[e];
tp_index_t_3 = (tp_index + t) * 3;
e = tp[tp_index_t_3];
}
else
{
z.Message = "invalid distance code";
c = z.AvailableBytesIn - n;
c = k >> 3 < c ? k >> 3 : c;
n += c;
p -= c;
k -= c << 3;
s.bitb = b;
s.bitk = k;
z.AvailableBytesIn = n;
z.TotalBytesIn += p - z.NextIn;
z.NextIn = p;
s.writeAt = q;
return(ZlibConstants.Z_DATA_ERROR);
}
} while (true);
break;
}
if ((e & 64) == 0)
{
t += tp[tp_index_t_3 + 2];
t += b & InternalInflateConstants.InflateMask[e];
tp_index_t_3 = (tp_index + t) * 3;
if ((e = tp[tp_index_t_3]) == 0)
{
b >>= tp[tp_index_t_3 + 1];
k -= tp[tp_index_t_3 + 1];
s.window[q++] = (byte)tp[tp_index_t_3 + 2];
m--;
break;
}
}
else if ((e & 32) != 0)
{
c = z.AvailableBytesIn - n;
c = k >> 3 < c ? k >> 3 : c;
n += c;
p -= c;
k -= c << 3;
s.bitb = b;
s.bitk = k;
z.AvailableBytesIn = n;
z.TotalBytesIn += p - z.NextIn;
z.NextIn = p;
s.writeAt = q;
return(ZlibConstants.Z_STREAM_END);
}
else
{
z.Message = "invalid literal/length code";
c = z.AvailableBytesIn - n;
c = k >> 3 < c ? k >> 3 : c;
n += c;
p -= c;
k -= c << 3;
s.bitb = b;
s.bitk = k;
z.AvailableBytesIn = n;
z.TotalBytesIn += p - z.NextIn;
z.NextIn = p;
s.writeAt = q;
return(ZlibConstants.Z_DATA_ERROR);
}
} while (true);
} while (m >= 258 && n >= 10);
// not enough input or output--restore pointers and return
c = z.AvailableBytesIn - n;
c = k >> 3 < c ? k >> 3 : c;
n += c;
p -= c;
k -= c << 3;
s.bitb = b;
s.bitk = k;
z.AvailableBytesIn = n;
z.TotalBytesIn += p - z.NextIn;
z.NextIn = p;
s.writeAt = q;
return(ZlibConstants.Z_OK);
}
