void VP8Shift()
{
// range_ is in [0..127] interval here.
int idx = (int)((uint)this.range_ >> (BITS));
int shift = kVP8Log2Range[idx];
this.range_ = kVP8NewRange[idx];
this.value_ = (bit_t)((uint)this.value_ << shift);
this.missing_ += shift;
}
void VP8LoadNewBytes()
{
Global.assert(this.buf_ != null);
// Read 'BITS' bits at a time if possible.
if (this.buf_ + sizeof(lbit_t) <= this.buf_end_)
{
// convert memory type to register type (with some zero'ing!)
bit_t bits;
lbit_t in_bits = *(lbit_t*)this.buf_;
this.buf_ += (BITS) >> 3;
#if !BIG_ENDIAN
bits = (bit_t)(in_bits >> 24) | ((in_bits >> 8) & 0xff00) | ((in_bits << 8) & 0xff0000) | (in_bits << 24);
#else
//#error Not Implemented
throw(new NotImplementedException());
#endif
this.value_ |= bits << this.missing_;
this.missing_ -= (BITS);
}
else
{
this.VP8LoadFinalBytes(); // no need to be inlined
}
}
//------------------------------------------------------------------------------
// VP8BitReader
// Initialize the bit reader and the boolean decoder.
void VP8InitBitReader(byte* start, byte* end)
{
Global.assert(start != null);
Global.assert((start <= end) != null);
this.range_ = MK(255 - 1);
this.buf_ = start;
this.buf_end_ = end;
this.value_ = 0;
this.missing_ = 8; // to load the very first 8bits
this.eof_ = 0;
}
/// <summary>
/// Special case for the tail
/// </summary>
void VP8LoadFinalBytes()
{
Global.assert(this.buf_ != null);
// Only read 8bits at a time
if (this.buf_ < this.buf_end_)
{
this.value_ |= (bit_t)(*this.buf_++) << ((BITS) - 8 + this.missing_);
this.missing_ -= 8;
}
else
{
this.eof_ = 1;
}
}
bool VP8BitUpdate(bit_t split)
{
bit_t value_split = split | (MASK);
if (this.missing_ > 0)
{ // Make sure we have a least BITS bits in 'value_'
this.VP8LoadNewBytes();
}
if (this.value_ > value_split)
{
this.range_ -= value_split + 1;
this.value_ -= value_split + 1;
return true;
}
else
{
this.range_ = value_split;
return false;
}
}
