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decoding performance

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This commit is contained in:
Arndt Brenschede 2019-06-29 10:11:59 +02:00
parent 7b4db81c78
commit 828227f59d
6 changed files with 65 additions and 46 deletions
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33
brouter-util/src/main/java/btools/util/BitCoderContext.java
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@ -13,6 +13,8 @@ public class BitCoderContext
private static final int[] vl_values = new int[4096];
private static final int[] vl_length = new int[4096];
private static final int[] reverse_byte = new int[256];
static
{
// fill varbits lookup table
@ -28,6 +30,15 @@ public class BitCoderContext
vl_values[i] = bc.decodeVarBits2();
vl_length[i] = bc.getReadingBitPosition() - b0;
}
for( int b=0; b<256; b++ )
{
int r = 0;
for( int i=0; i<8; i++ )
{
if ( (b & (1<<i) ) != 0 ) r |= 1 << (7-i);
}
reverse_byte[b] = r;
}
}
@ -190,10 +201,6 @@ public class BitCoderContext
public final int decodeBits( int count )
{
if ( count == 0 )
{
return 0;
}
fillBuffer();
int mask = 0xffffffff >>> ( 32 - count );
int value = b & mask;
@ -202,6 +209,24 @@ public class BitCoderContext
return value;
}
public final int decodeBitsReverse( int count )
{
fillBuffer();
int value = 0;
while( count > 8 )
{
value = (value << 8) | reverse_byte[ b & 0xff ];
b >>=8;
count -=8;
bits -=8;
fillBuffer();
}
value = (value << count) | reverse_byte[ b & 0xff ] >> (8-count);
bits -= count;
b >>= count;
return value;
}
private void fillBuffer()
{
while (bits < 24)