acooks/jittertrap

#define _POSIX_C_SOURCE 200809L
#include <sys/time.h>
#include <stdlib.h>
#include <assert.h>
#include <stdint.h>
#include <stdio.h>
#include <pthread.h>

#include "jittertrap.h"
#include "iface_stats.h"
#include "sample_buf.h"

/* a circular buffer with one element of separation */
#define CIRC_BUF_SIZE 3
#define BUF_BYTE_LEN (CIRC_BUF_SIZE * sizeof(struct iface_stats))

static pthread_mutex_t pc_mutex = PTHREAD_MUTEX_INITIALIZER;

static struct iface_stats *sample_buf;
static struct iface_stats *produce_ptr;
static struct iface_stats *consume_ptr;

void raw_sample_buf_init(void)
{
    sample_buf = malloc(BUF_BYTE_LEN);
    assert(sample_buf);
    produce_ptr = sample_buf;
    consume_ptr = sample_buf;
}

struct iface_stats *raw_sample_buf_produce_next(void)
{
    pthread_mutex_lock(&pc_mutex);
    produce_ptr++;
    if ((uint8_t *)produce_ptr == ((uint8_t *)sample_buf + BUF_BYTE_LEN)) {
        /* end of buffer, wrap around */
        produce_ptr = sample_buf;
    }

    /* check one element of separation */
    /* FIXME: needs some kind of lock instead */
    assert(produce_ptr != consume_ptr);
    pthread_mutex_unlock(&pc_mutex);
    assert((uint8_t *)produce_ptr < ((uint8_t *)sample_buf + BUF_BYTE_LEN));
    return produce_ptr;
}

struct iface_stats *raw_sample_buf_consume_next(void)
{
    pthread_mutex_lock(&pc_mutex);
    consume_ptr++;
    if ((uint8_t *)consume_ptr == ((uint8_t *)sample_buf + BUF_BYTE_LEN)) {
        consume_ptr = sample_buf;
    }

    assert(consume_ptr != produce_ptr);
    pthread_mutex_unlock(&pc_mutex);
    return consume_ptr;
}