ring.c

linux下 步进电机驱动

/* Copyright 1998,1999, Mark Whitis <[e-mail]> */
/* http://www.freelabs.com/~whitis/ */

#include "ring.h"

int ring_debug=1;

#ifdef TEST
#define printk printf
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#endif


void ring_buffer_init(ring_buffer_t *ring)
{
    ring->signature=RING_SIGNATURE;
    ring->head_p=ring->buffer;
    ring->tail_p=ring->buffer;
    ring->begin_p=ring->buffer;
    ring->end_p=&ring->buffer[sizeof(ring->buffer)];
    #if 0
       strcpy(ring->buffer,"This is a test.\n");
       ring->head_p +=16;
    #endif
}

/* returns number of bytes read */
/* will not block (blocking will be handled by calling routine if */
/* necessary).  If you request to read more bytes than are currently */
/* availible, it will return a count less than the value you passed in */
int ring_buffer_read(ring_buffer_t *ring, unsigned char *buf, int count) 
{
  #ifdef PARANOID
     if(ring_debug>5) printk("das1600: ring_buffer_read(%08X,%08X,%d)\n",ring,buf,count);
     if(ring->signature != RING_SIGNATURE) {
	printk("ring_buffer_read: signature corrupt\n");
	return(0);
     }
     if(ring->tail_p < ring->begin_p) {
	printk("ring_buffer_read: tail corrupt\n");
	return(0);
     }
     if(ring->tail_p > ring->end_p) {
	printk("ring_buffer_read: tail corrupt\n");
	return(0);
     }
     if(count != 1) {
	printk("ring_buffer_read: count must currently be 1\n");
	return(0);
     }
  #endif;
  if(ring->tail_p == ring->end_p) {
     ring->tail_p = ring->begin_p;
  }
  if(ring->tail_p == ring->head_p) {
     if(ring_debug>5) printk("ring_buffer_read: buffer underflow\n");
     return(0);
  }

  *buf = *ring->tail_p++;
  return(1);
}

/* returns number of bytes written */
/* will not block (blocking will be handled by calling routine if */
/* necessary).  If you request to read more bytes than are currently */
/* availible, it will return a count less than the value you passed in */
int ring_buffer_write(ring_buffer_t *ring, unsigned char *buf, int count) 
{
   unsigned char *tail_p;
  #ifdef PARANOID
     if(ring->signature != RING_SIGNATURE) {
	printk("ring_buffer_write: signature corrupt\n");
	return(0);
     }
     if(ring->head_p < ring->begin_p) {
	printk("ring_buffer_write: head corrupt\n");
	return(0);
     }
     if(ring->head_p > ring->end_p) {
	printk("ring_buffer_write: head corrupt\n");
	return(0);
     }
     if(count != 1) {
	printk("ring_buffer_write: count must currently be 1\n");
	return(0);
     }
  #endif
  /* Copy tail_p to a local variable in case it changes between comparisons */
  tail_p = ring->tail_p;


  if( (ring->head_p == (tail_p - 1) )
  || ((ring->head_p == (ring->end_p - 1)) && (tail_p==ring->begin_p)) ) {
     if(ring_debug>5) printk("ring_buffer_write: buffer overflow\n");
     return(0);
  }

  *ring->head_p++ = *buf;

  if(ring->head_p == ring->end_p ) {
     ring->head_p = ring->begin_p;
  }
  return(1);
}


#ifdef TEST



ring_buffer_t buffer;
main()
{ 
   char c;
   char c2;
   int child;
   int rc;
   int i;
   int j;
   char lastread;
   int errors;
   int reads;
   int writes;

   ring_buffer_init(&buffer);

   c=0;
   lastread=-1;
   errors=0;
   reads=0;
   writes=0;
   for(j=0; j<50000; j++) {
      for(i=0; i<31; i++) {
	 rc=ring_buffer_write(&buffer, &c, 1);
         writes++;
	 if(ring_debug>2) printf("ring_buffer_write returned %d, was passed %d\n",rc,c);
	 if(rc==1) c++;
      }

      for(i=0; i<47; i++) {
	 rc=ring_buffer_read(&buffer, &c2, 1);
         reads++;
	 if(ring_debug>2) printf("ring_buffer_read returned: rc=%d,c2=%d\n",rc,c2);
         if(rc==1) {
	   if(c2!=(char)(lastread+1)) {
              printf("ERROR: expected %d, got %d\n",(char)(lastread+1),c2);
              errors++;
           }
           lastread=c2;
         }
      }
   }
   printf("number of errors=%d\n",errors);
   printf("number of reads=%d\n",reads);
   printf("number of writes=%d\n",writes);


}
#endif