File: ringbuff.c

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/*
 * This file has been modified for the cdrkit suite.
 *
 * The behaviour and appearence of the program code below can differ to a major
 * extent from the version distributed by the original author(s).
 *
 * For details, see Changelog file distributed with the cdrkit package. If you
 * received this file from another source then ask the distributing person for
 * a log of modifications.
 *
 */

/* @(#)ringbuff.c	1.8 02/11/21 Copyright 1998,1999,2000 Heiko Eissfeldt */
#include "config.h"

#include <stdxlib.h>
#include <stdio.h>
#include <standard.h>
#include <unixstd.h>

#if defined(HAVE_SEMGET) && defined(USE_SEMAPHORES)
#include <sys/ipc.h>
#include <sys/sem.h>
#endif

#include <usal/scsitransp.h>

#include "mytype.h"
#include "global.h"
#include "interface.h"
#include "ringbuff.h"
#include "semshm.h"
#include "exitcodes.h"

#undef WARN_INTERRUPT
#undef _DEBUG
#include <assert.h>

static void occupy_buffer(void);

myringbuff **he_fill_buffer;
myringbuff **last_buffer;
volatile unsigned long *total_segments_read;
volatile unsigned long *total_segments_written;
volatile int *child_waits;
volatile int *parent_waits;
volatile int *in_lendian;
volatile int *eorecording;

static myringbuff *previous_read_buffer;
static unsigned int total_buffers;

#define SEMS 2

#define defined_buffers() ((*total_segments_read) - (*total_segments_written))
#define free_buffers() (total_buffers - defined_buffers())
#define occupied_buffers() (defined_buffers())

/* ARGSUSED */
void set_total_buffers(unsigned int num_buffers, int mysem_id)
{
#if defined(HAVE_SEMGET) && defined(USE_SEMAPHORES)
  union my_semun mysemun;

  mysemun.val   = 0;
  if (semctl(mysem_id,(int) DEF_SEM,SETVAL,mysemun) < 0) {
    perror("semctl DEF_SEM");
  }

  mysemun.val   = num_buffers;
  if (semctl(mysem_id,(int) FREE_SEM,SETVAL,mysemun) < 0) {
    perror("semctl FREE_SEM");
  }
#endif

  total_buffers = num_buffers;

  /* initialize pointers */
  *he_fill_buffer = *last_buffer = previous_read_buffer = NULL;
#ifdef DEBUG_SHM
fprintf(stderr, "init: fill_b = %p,  last_b = %p\n", *he_fill_buffer, *last_buffer);
#endif
}

const myringbuff *get_previous_read_buffer()
{
  assert(previous_read_buffer != NULL);
  assert(previous_read_buffer != *he_fill_buffer);
  return previous_read_buffer;
}

const myringbuff *get_he_fill_buffer()
{
  assert(*he_fill_buffer != NULL);
  assert(previous_read_buffer != *he_fill_buffer);
  return *he_fill_buffer;
}

void define_buffer()
{
  assert(defined_buffers() < total_buffers);

#ifdef _DEBUG
#if 0
  fprintf(stderr,"stop  reading  %p - %p\n",
                 *he_fill_buffer, (char *)(*he_fill_buffer) + ENTRY_SIZE -1);
#endif
#endif

  if (*last_buffer == NULL)
    *last_buffer = *he_fill_buffer;
#ifdef DEBUG_SHM
fprintf(stderr, "define: fill_b = %p,  last_b = %p\n", *he_fill_buffer, *last_buffer);
#endif

  (*total_segments_read)++;
  semrelease(sem_id,DEF_SEM,1);
}

void drop_buffer()
{
  assert(free_buffers() < total_buffers);
  assert(occupied_buffers() > 0);

#ifdef _DEBUG
#if 0
  fprintf(stderr," stop  writing %p - %p ",
                 *last_buffer, (char *)(*last_buffer) + ENTRY_SIZE -1);
#endif
#endif

  if (*last_buffer == NULL)
    *last_buffer = *he_fill_buffer;
  else
    *last_buffer = INC(*last_buffer);
#ifdef DEBUG_SHM
fprintf(stderr, "drop: fill_b = %p,  last_b = %p\n", *he_fill_buffer, *last_buffer);
#endif
  (*total_segments_written)++;
  semrelease(sem_id,FREE_SEM, 1);
}

void drop_all_buffers()
{
  (*total_segments_written) = (*total_segments_read);
  semrelease(sem_id,FREE_SEM, total_buffers);
}

static void occupy_buffer()
{
  assert(occupied_buffers() <= total_buffers);

  previous_read_buffer = *he_fill_buffer;

  if (*he_fill_buffer == NULL) {
    *he_fill_buffer = RB_BASE;
  } else {
    *he_fill_buffer = INC(*he_fill_buffer);
  }
}

#if defined HAVE_FORK_AND_SHAREDMEM
myringbuff * get_next_buffer()
{
#ifdef WARN_INTERRUPT
  if (free_buffers() <= 0) {
    fprintf(stderr, "READER waits!! r=%lu, w=%lu\n", *total_segments_read,
*total_segments_written);
  }
#endif

  /* wait for a new buffer to become available */
  if (semrequest(sem_id,FREE_SEM) != 0) {
    /* semaphore operation failed.
       try again...
       */
    fprintf(stderr, "child reader sem request failed\n");
    exit(SEMAPHORE_ERROR);
  }
#if 0
  fprintf(stderr,"start reading  %p - %p\n",
                 *he_fill_buffer, (char *)(*fill_buffer) + ENTRY_SIZE -1);
#endif

  occupy_buffer();

#ifdef DEBUG_SHM
fprintf(stderr, "next: fill_b = %p,  last_b = %p, @last = %p\n", *he_fill_buffer, *last_buffer, last_buffer);
#endif
  return *he_fill_buffer;
}

myringbuff *get_oldest_buffer()
{
  myringbuff *retval;

#ifdef WARN_INTERRUPT
  if (free_buffers() == total_buffers) {
    fprintf(stderr, "WRITER waits!! r=%lu, w=%lu\n", *total_segments_read,
			*total_segments_written);
  }
#endif
  /* wait for buffer to be defined */
  if (semrequest(sem_id,DEF_SEM) != 0) {
    /* semaphore operation failed. */
    perror("request defined buff:");
    fprintf(stderr, "parent writer sem request failed\n");
  }

  retval = *last_buffer;

#if 0
  fprintf(stderr," begin writing %p - %p\n",
                  retval, (char *)retval + ENTRY_SIZE -1);
#endif

  return retval;
}
#else /* HAVE_FORK_AND_SHAREDMEM */
myringbuff * get_next_buffer()
{
  occupy_buffer();
  return *he_fill_buffer;
}

myringbuff * get_oldest_buffer()
{
  return *he_fill_buffer;
}
#endif /* HAVE_FORK_AND_SHAREDMEM */