jinahya / bit-io Goto Github PK

Re:

https://github.com/jinahya/bit-io/blob/develop/src/main/java/com/github/jinahya/bit/io/AbstractBitInput.java#L116

There are a few places in the code base that use integer division and modular arithmetic. It may be possible to replace them with faster bit-shifting equivalents. Imagine a variable mPosition that points to a particular bit within a byte array. Retrieving the value of the bit can be accomplished as follows, where BYTE_INDEX_SHIFT equals 3 (i.e., log base 2 of 8):

final int byteIndex = (int) (mPosition >> BYTE_INDEX_SHIFT);
final int bitIndex = (int) (mPosition - (byteIndex << BYTE_INDEX_SHIFT));

final int bitShifts = Byte.SIZE - bitIndex - 1;
final int bit = (mSequence[byteIndex] & (1 << bitShifts)) >> bitShifts;

I suspect such calculations will be more efficient than using %, especially on older hardware.

Great stuff, but sadly I do now miss the "flush()" that basically writes through to byte buffer without advancing the position. As I do have a concurrent read on the ByteBuffer I need all Bits also in the last octet filled (padded with 0)

I don't want to call align(8) after every write as my data consumes only 2 bits in many cases.

Consider adding a method that skips ahead by n bits, such as:

       final byte[] bytes = { 0b01011001, 0b01100101 };
       final ArrayByteInput byteInput = new ArrayByteInput( bytes );
       final BitInput bitInput = new DefaultBitInput( byteInput );

       bitInput.skip( 5 );

       final int i = bitInput.readInt( true, 6 );
       final boolean bo = bitInput.readBoolean();
       final byte nibble = bitInput.readByte( true, 4 ); // Or bitInput.readNybble();?

Make AbstractBitInput#octet and AbstractBitOutput#octet private

https://github.com/raydac/java-binary-block-parser
https://github.com/preon/preon

Hi - nice library.

The docs show ByteInput being used with various methods like readBoolean or ints but v2.0.2 ByteInput only has a single read int method. Can you point me to the correct implementation to read bits from a byte array?

I can help with your readme once i get it working

Consider a convenience method that reads 4 bits into a byte:

final BitInput bitInput = new DefaultBitInput( ... );
final byte nybble = bitInput.readNybble();

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