通信用リングバッファのサンプルその2。とりあえずモジュール化しといた。

main.c

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

#include "mystd.h"

#define RINGBUF_SIZE 8
#include "ringbuf.h"

RINGBUF rbuf;

void dump(void)
{
    u1 dpw[8], dpr[8];

    for(int i=0; i<8; i++) {
        dpw[i] = dpr[i] = ' ';
    }

    dpw[rbuf.pw] = 'w';
    dpr[rbuf.pr] = 'r';

    printf ("-------------------------------------------------\n");
    printf("[%1d] [%1d] [%1d] [%1d] [%1d] [%1d] [%1d] [%1d]\n", 0, 1, 2, 3, 4, 5, 6, 7);
    printf(" %1c   %1c   %1c   %1c   %1c   %1c   %1c   %1c \n", dpw[0], dpw[1], dpw[2], dpw[3], dpw[4], dpw[5], dpw[6], dpw[7]);
    printf("%2X  %2X  %2X  %2X  %2X  %2X  %2X  %2X\n", rbuf.buf[0], rbuf.buf[1], rbuf.buf[2], rbuf.buf[3], rbuf.buf[4], rbuf.buf[5], rbuf.buf[6], rbuf.buf[7]);
    printf(" %1c   %1c   %1c   %1c   %1c   %1c   %1c   %1c \n", dpr[0], dpr[1], dpr[2], dpr[3], dpr[4], dpr[5], dpr[6], dpr[7]);
}

int main(void)
{
    u1 v = 3;

    ringbuf_init(&rbuf);
    dump();

    for(int i=0; i<20; i++){
        u1 data;
        if(ringbuf_read(&rbuf, &data)) printf("read:%X\n", data);
    }
    dump();

    for(int i=0; i<20; i++) ringbuf_write(&rbuf, v++);
    dump();

    for(int i=0; i<20; i++){
        u1 data;
        if(ringbuf_read(&rbuf, &data)) printf("read:%X\n", data);
    }
    dump();

    for(int i=0; i<3; i++) ringbuf_write(&rbuf, v++);
    dump();
    
    for(int i=0; i<20; i++){
        u1 data;
        if(ringbuf_read(&rbuf, &data)) printf("read:%X\n", data);
    }
    dump();

    for(int i=0; i<20; i++) ringbuf_write(&rbuf, v++);
    dump();
    
    for(int i=0; i<20; i++){
        u1 data;
        if(ringbuf_read(&rbuf, &data)) printf("read:%X\n", data);
    }
    dump();

    return EXIT_SUCCESS;
}

mystd.h

/* mystd.h */
#ifndef __MYSTD_H__
#define __MYSTD_H__

/* types and values */
typedef unsigned char  u1;
typedef unsigned short u2;
typedef unsigned long  u4;

typedef signed char  s1;
typedef signed short s2;
typedef signed long  s4;

typedef unsigned char bool;
#define FALSE 0
#define TRUE  1

#define LO    0
#define HI    1

#define OFF   0
#define ON    1

#define NG    0
#define OK    1

#define EXIT_SUCCESS    0
#define EXIT_FAILURE    1


/* pseudo functions */
#define __ei()    sei()
#define __di()    cli()


#endif  /* __MYSTD_H__ */

result.txt

$gcc -std=c99 main.c && ./a.out 
-------------------------------------------------
[0] [1] [2] [3] [4] [5] [6] [7]
 w                             
FF  FF  FF  FF  FF  FF  FF  FF
 r                             
-------------------------------------------------
[0] [1] [2] [3] [4] [5] [6] [7]
 w                             
FF  FF  FF  FF  FF  FF  FF  FF
 r                             
-------------------------------------------------
[0] [1] [2] [3] [4] [5] [6] [7]
                             w 
FF   3   4   5   6   7   8   9
 r                             
read:3
read:4
read:5
read:6
read:7
read:8
read:9
-------------------------------------------------
[0] [1] [2] [3] [4] [5] [6] [7]
                             w 
FF   3   4   5   6   7   8   9
                             r 
-------------------------------------------------
[0] [1] [2] [3] [4] [5] [6] [7]
         w                     
17  18  19   5   6   7   8   9
                             r 
read:17
read:18
read:19
-------------------------------------------------
[0] [1] [2] [3] [4] [5] [6] [7]
         w                     
17  18  19   5   6   7   8   9
         r                     
-------------------------------------------------
[0] [1] [2] [3] [4] [5] [6] [7]
     w                         
1F  20  19  1A  1B  1C  1D  1E
         r                     
read:1A
read:1B
read:1C
read:1D
read:1E
read:1F
read:20
-------------------------------------------------
[0] [1] [2] [3] [4] [5] [6] [7]
     w                         
1F  20  19  1A  1B  1C  1D  1E
     r                         
$

ringbuf.h

/* ringbuf.h */
#ifndef __RINGBUF_H__
#define __RINGBUF_H__

#include "mystd.h"

#ifdef RINGBUF_SIZE
  #define SIZE RINGBUF_SIZE
#else
  #error "You need to define RINGBUF_SIZE"
#endif

/* types and values */
typedef struct {
    u1 buf[SIZE];
    u1 pr, pw;
} RINGBUF;


/* service functions */
void ringbuf_init(RINGBUF *r)
{
    for(u1 i=0; i<SIZE; i++)
        r->buf[i] = 0xFF;

    r->pr = r->pw = 0;
}

bool ringbuf_write(RINGBUF *r, u1 ch)
{
    u1 nextw = (r->pw+1) % SIZE;
    
    if(nextw == r->pr) return NG;

    r->pw = nextw;
    r->buf[nextw] = ch;
    return OK;
}

bool ringbuf_read(RINGBUF *r, u1 *ch)
{
    u1 nextw = (r->pw+1) % SIZE;
    u1 nextr = (r->pr+1) % SIZE;

    if(nextw == nextr) return NG;

    r->pr = nextr;
    *ch = r->buf[nextr];
    return OK;
}

#undef SIZE

#endif  /* __RINGBUF_H__ */