matiaslindgren / bitmatch

Search for bit patterns in standard input.

bitmatch

Search for bit patterns in standard input. Probably useless.

Example

Search for first 11 bits of f8c (1111 1000 110) in the input:

$ echo 'h>0?' | ./bitmatch f8c 11 || echo not found
$ echo 'h<0?' | ./bitmatch f8c 11 || echo not found
not found

Explanation

Input data h>0? as bits:

$ echo 'h>0?' | xxd -b
00000000: 01101000 00111110 00110000 00111111 00001010           h>0?.

First 11 bits of pattern f8c:

$ pattern="$(echo f8c | python3 -c 'print("".join(format(int(c, 16), "b") for c in input())[:11])')"
$ echo $pattern
11111000110

The bit pattern can be found in the input for example with grep:

$ echo 'h>0?' | xxd -b | tr -d ' ' | grep "$pattern" || echo not found
00000000:0110100000111110001100000011111100001010h>0?.
$ echo 'h<0?' | xxd -b | tr -d ' ' | grep "$pattern" || echo not found
not found

That's basically the only thing bitmatch does.

Usage

$ ./bitmatch
usage: bitmatch hex_pattern prefix_length
  hex_pattern: string in hexadecimal of the pattern to search for. E.g. hex_pattern f8c will search for 111110001100
  prefix_length: number of bits to use from the beginning of hex_pattern. E.g. prefix_length 9 would search for 111110001.

Build & test

make all
./test.sh ./build/target bitmatch

With GCC

make CC=gcc CXX=g++ all

Release

make BUILD=release all

C++ API

make dirs bitdump bitmatch_cpp
./test.sh ./build/target bitmatch_cpp

Shared library

make dirs bitdump bitmatch_dyn
export LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:./build
./test.sh ./build/target bitmatch_dyn