buffer

Buffer

Overview

• Buffer implementation for serializing data/protocol implementation.
• Works with binary data, 8/16/32/64-bit integers, double and strings.
• Strings are kept length prefixed and null ended. So, no need to copy string
  when you are reading, you just get the pointer. This is useful to avoid memory
  allocation overhead.
• Integer operations are compiled into bounds check + a single MOV instruction
  with a good compiler. Buffer keeps data in Little Endian format, so on big
  endian systems, integer put/get is bswap(byte swap) + MOV.

Usage

#include "sc_buf.h"
#include <stdio.h>

void basic(void)
{
    struct sc_buf buf;
    sc_buf_init(&buf, 1024);

    sc_buf_put_32(&buf, 16);
    sc_buf_put_str(&buf, "test");
    sc_buf_put_fmt(&buf, "value is %d", 3);

    printf("%d \n", sc_buf_get_32(&buf));
    printf("%s \n", sc_buf_get_str(&buf));
    printf("%s \n", sc_buf_get_str(&buf));

    sc_buf_term(&buf);
}

void error_check(void)
{
    uint32_t val, val2;
    struct sc_buf buf;

    sc_buf_init(&buf, 1024);
    sc_buf_put_32(&buf, 16);

    val = sc_buf_get_32(&buf);
    val2 = sc_buf_get_32(&buf); // This will set error flag in buffer;

    if (sc_buf_valid(&buf) == false) {
        printf("buffer is corrupt");
        exit(EXIT_FAILURE);
    }

    sc_buf_term(&buf);
}

int main(void)
{
    basic();
    error_check();

    return 0;
}

Lazy error check

• Rather than checking error code for each put(Out of memory/limit exceeded) or
  get operation(buffer underflow) , error check can be postponed until end of an
  operation batch.

#include "sc_buf.h"
#include <stdio.h>

int main(void)
{
    uint32_t val, val2;
    struct sc_buf buf;

    sc_buf_init(&buf, 0);
    sc_buf_put_32(&buf, 1);  // Even if we get OOM, it is safe to continue.
    sc_buf_put_32(&buf, 2);  
    sc_buf_put_32(&buf, 3);
    sc_buf_put_32(&buf, 4);

    if (sc_buf_valid(&buf) == false) {
        printf("OOM!.");
        exit(EXIT_FAILURE);
    }

    sc_buf_term(&buf);

    return 0;
}

#include "sc_buf.h"
#include <stdio.h>

int main(void)
{
    uint32_t val;
    struct sc_buf buf;

    sc_buf_init(&buf, 0);
    sc_buf_put_32(&buf, 1); 
    sc_buf_put_32(&buf, 2);
    
    val = sc_buf_get_32(&buf);
    val = sc_buf_get_32(&buf);
    val = sc_buf_get_32(&buf); // Buffer underflow here
    val = sc_buf_get_32(&buf); // Buffer underflow here
        
    if (sc_buf_valid(&buf) == false) {
        printf("Buffer underflow!.");
        exit(EXIT_FAILURE);
    }

    sc_buf_term(&buf);

    return 0;
}