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Spec: Simplify DecodeTaggedSymbols function

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- Addresses a comment in KhronosGroup/glTF#1114
This commit is contained in:
Frank Galligan 2017-10-20 11:55:08 -07:00
parent 3164f693e6
commit cf02c772fe
1 changed files with 1 additions and 31 deletions
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32
docs/spec/rans.decoding.md
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@ -16,47 +16,17 @@ void DecodeSymbols(num_symbols, num_components, out_values) {
{:.draco-syntax } {:.draco-syntax }
### ComputeRAnsUnclampedPrecision
~~~~~
int ComputeRAnsUnclampedPrecision(max_bit_length) {
return (3 * max_bit_length) / 2;
}
~~~~~
{:.draco-syntax }
### ComputeRAnsPrecisionFromMaxSymbolBitLength
~~~~~
int ComputeRAnsPrecisionFromMaxSymbolBitLength(max_bit_length) {
return ComputeRAnsUnclampedPrecision(max_bit_length) < 12
? 12
: ComputeRAnsUnclampedPrecision(max_bit_length) > 20
? 20
: ComputeRAnsUnclampedPrecision(max_bit_length);
}
~~~~~
{:.draco-syntax }
### DecodeTaggedSymbols ### DecodeTaggedSymbols
~~~~~ ~~~~~
void DecodeTaggedSymbols(num_values, num_components, out_values) { void DecodeTaggedSymbols(num_values, num_components, out_values) {
max_symbol_bit_length_t = 5;
rans_precision_bits_t =
ComputeRAnsPrecisionFromMaxSymbolBitLength(max_symbol_bit_length_t);
rans_precision = 1 << rans_precision_bits_t;
l_rans_base = rans_precision * 4;
num_symbols_ varUI32 num_symbols_ varUI32
BuildSymbolTables(num_symbols_, lut_table_, probability_table_); BuildSymbolTables(num_symbols_, lut_table_, probability_table_);
size varUI64 size varUI64
encoded_data UI8[size] encoded_data UI8[size]
RansInitDecoder(ans_, &encoded_data[0], size, l_rans_base); RansInitDecoder(ans_, &encoded_data[0], size, l_rans_base);
for (i = 0; i < num_values; i += num_components) { for (i = 0; i < num_values; i += num_components) {
RansRead(ans_, l_rans_base, rans_precision, RansRead(ans_, L_RANS_BASE, rans_precision,
lut_table_, probability_table_, &size); lut_table_, probability_table_, &size);
for (j = 0; j < num_components; ++j) { for (j = 0; j < num_components; ++j) {
val f[size] val f[size]