libsr

A small helper for processing Sigrok .sr-files in C. Uses libzip. Useful for fast processing of big (or small) captures with custom code.

Licence and Disclaimer

This code is provided under AGPLv3+ and WITHOUT ANY WARRANTY! It is an early release and only sparsely tested.

Public API

#define LENGTH_NAME_MAX 20

void sr_open(char const * const filename);
uint_fast8_t sr_get_nb_channels(void);
uint_fast8_t sr_get_channel_bitpos(char const * const name);
uint64_t sr_get_nb_samples(void);
bool sr_get_sample(const uint_fast8_t pos_channel, const uint64_t sample);
void sr_close(void);

LENGTH_NAME_MAX is the maximum length of the name of each channel (excluding the '\0'). 20 characters is plenty but you can always change this and recompile.

The functions should be pretty self-explanatory i guess? Please call sr_close() once you're done to free internal memory.

How to compile

You will need libzip, on Debian 11 the package is called libzip-dev.
Compile with something like gcc -Wall -Wextra -Werror -O3 -o your_tool libsr.c main.c -lzip (adjust as needed, the important bit is the -lzip at the end)

Limitations

The current version will copy all the uncompressed (sr==zip basically) samples in memory, so you need enough RAM for big captures. I did this for speed, i might write a version that uses less RAM at some point.
The code works for digital channels only and up 2**64 bytes of captured data total. That should be enough i think...
If something goes wrong (for example if you call sr_get_channel_bitpos() with an invalid name, ...) the code will exit directly using errx(). This makes it non-suitable for stuff like GUI-applications.

Example

Here is a quick and dirty parallel bus-decoder (rising edge on CLK, data 8 bits):

#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>

#include "libsr.h"

int main(int argc, char ** argv)
{
	(void)argc;
	
	sr_open(argv[1]);
	
	uint_fast8_t channel_CLK;
	channel_CLK=sr_get_channel_bitpos("CLK");
	
	//caution: MSB/LSB?
	uint_fast8_t channel_DATA[8];
	channel_DATA[0]=sr_get_channel_bitpos("D0");
	channel_DATA[1]=sr_get_channel_bitpos("D1");
	channel_DATA[2]=sr_get_channel_bitpos("D2");
	channel_DATA[3]=sr_get_channel_bitpos("D3");
	channel_DATA[4]=sr_get_channel_bitpos("D4");
	channel_DATA[5]=sr_get_channel_bitpos("D5");
	channel_DATA[6]=sr_get_channel_bitpos("D6");
	channel_DATA[7]=sr_get_channel_bitpos("D7");
	
	uint64_t nb_samples=sr_get_nb_samples();
	uint64_t sample;
	bool clk, clk_old=0;
	uint_fast8_t bitcnt=0;
	uint_fast8_t i;
	uint8_t byte;
	
	for(sample=0; sample<nb_samples; sample++)
	{
		clk=sr_get_sample(channel_CLK, sample);
		
		if(clk && !clk_old)
		{
			if(++bitcnt==8)
			{
				bitcnt=0;
				byte=0;
				for(i=0; i<8; i++)
					byte|=sr_get_sample(channel_DATA[i], sample)<<i;
				printf("%02X\n", byte);
			}
		}
		clk_old=clk;
	}
	
	sr_close();
	
	return 0;
}