linuxaudio.org

just wondered if any more-experienced-than-i devs might comment on

this. written in c for c (obviously). i realize it's not portable

outside of GNU GCC (regarding the GCC atomic builtin funcs

__sync_***). meant for a single reader thread and a single writer

thread. comments regarding thread safety very much welcome. thanks in

advance.
james.
#include "rng_buf.h" /* only prototypes the public functions and

typedefs the struct */
#include

#include

#include "debug.h"
struct _RingBuffer

{

    size_t count;
    void** buf;

    void** bufend;
    void** volatile w;

    void** volatile r;

};
RngBuf* rng_buf_new(size_t count)

{

    size_t sz = 1;

    RngBuf* mb = malloc(sizeof(RngBuf));
    if (!mb)

    {

        return 0;

    }
    for (sz = 1; sz < count; sz <<= 1)

        ;
    mb->buf = calloc(sz, sizeof(void*));
    if (!mb->buf)

    {

        free(mb);

        return 0;

    }
    mb->count = sz;

    mb->bufend = mb->buf + mb->count - 1;

    mb->w = mb->buf;

    mb->r = mb->buf;
    return mb;

}
void rng_buf_free(RngBuf* mb)

{

    free(mb->buf);

    free(mb);

}
size_t rng_buf_write(RngBuf* mb, const void* data)

{

    if (__sync_bool_compare_and_swap(mb->w, 0, data))

    {

        if (!(__sync_bool_compare_and_swap(&mb->w, mb->bufend, mb->buf)))

            __sync_add_and_fetch(&mb->w, sizeof(void*));
        return (size_t)1;

    }
    return (size_t)0;

}
void* rng_buf_read(RngBuf* mb)

{

    void* data;
    if ((data = __sync_fetch_and_and(mb->r, 0)))

    {

        if (!__sync_bool_compare_and_swap(&mb->r, mb->bufend, mb->buf))

            __sync_add_and_fetch(&mb->r, sizeof(void*));
        return data;

    }
    return NULL;

}
void rng_buf_reset(RngBuf* mb)

{ /* needs work */

    mb->r = mb->w = mb->buf;

}

_______________________________________________

Linux-audio-dev mailing list

Linux-audio-dev@lists.linuxaudio.org

http://lists.linuxaudio.org/listinfo/linux-audio-dev