chemag / binstr

A generic language to define binary strings

binstr: a language to define binary strings

Copyright 2015 Google Inc.

This is not an official Google product.

Introduction

binstr is a generic language to define binary strings (char *) using a combination of decimal, hexadecimal, octal, and binary components, explicit lengths, and repeated items. The goal is to be able to define a binary string using a user-friendly language.

binstr also supports comments (any item starting with '#'), blank lines, and generic indentation.

For example, an IPv4 header could be defined as follows:

const char kIpHeader[] = R"(
  # version header_length service_type total_length
  {4}0x4 {4}20 0x00 {16}1500
  # identification evil dnf mf offset
  {16}0xcafe 0b0 0b0 0b0 {13}0
  # ttl protocol checksum
  {8}255 {8}17 {16}0
  # source addr
  {32}0x12345678
  # dst addr
  {32}0x9abcdef0
)";

And then read into an actual binary buffer using:

char binbuf[1024];
int bitlen = binstr_parse(kIpHeader, binbuf, sizeof(binbuf));

Note that bitlen is the number of bits read, which may not be a multiple of 8.

binstr_snprintf() adds a snprintf-like preprocessor.

See the design doc for more information.