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ringbuffy.c

/* 
    Ringbuffer Implementation for gtvscreen

    Copyright (C) 2000 Marcus Metzler (mocm@metzlerbros.de)

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "ringbuffy.h"
#include <string.h>

int ring_init (ringbuffy *rbuf, int size)
{
      if (size > 0){
            rbuf->size = size;
            if( !(rbuf->buffy = (char *) malloc(sizeof(char)*size)) ){
                  fprintf(stderr,"Not enough memory for ringbuffy\n");
                  return -1;
            }
      } else {
            fprintf(stderr,"Wrong size for ringbuffy\n");
            return -1;
      }
      rbuf->read_pos = 0;     
      rbuf->write_pos = 0;
      return 0;
}


void ring_destroy(ringbuffy *rbuf)
{
      free(rbuf->buffy);
}


int ring_write(ringbuffy *rbuf, char *data, int count)
{

      int diff, free, pos, rest;

      if (count <=0 ) return 0;
            pos  = rbuf->write_pos;
      rest = rbuf->size - pos;
      diff = rbuf->read_pos - pos;
      free = (diff > 0) ? diff-1 : rbuf->size+diff-1;

      if ( free <= 0 ) return FULL_BUFFER;
      if ( free < count ) count = free;
      
      if (count >= rest){
            memcpy (rbuf->buffy+pos, data, rest);
            if (count - rest)
                  memcpy (rbuf->buffy, data+rest, count - rest);
            rbuf->write_pos = count - rest;
      } else {
            memcpy (rbuf->buffy+pos, data, count);
            rbuf->write_pos += count;
      }

      return count;
}




int ring_peek(ringbuffy *rbuf, char *data, int count, long off)
{

      int diff, free, pos, rest;

      if (count <=0 ) return 0;
      pos  = rbuf->read_pos+off;
      rest = rbuf->size - pos ;
      diff = rbuf->write_pos - pos;
      free = (diff >= 0) ? diff : rbuf->size+diff;

      if ( free <= 0 ) return FULL_BUFFER;
      if ( free < count ) count = free;
      
      if ( count < rest ){
            memcpy(data, rbuf->buffy+pos, count);
      } else {
            memcpy(data, rbuf->buffy+pos, rest);
            if ( count - rest)
                  memcpy(data+rest, rbuf->buffy, count - rest);
      }

      return count;
}

int ring_read(ringbuffy *rbuf, char *data, int count)
{

      int diff, free, pos, rest;

      if (count <=0 ) return 0;
      pos  = rbuf->read_pos;
      rest = rbuf->size - pos;
      diff = rbuf->write_pos - pos;
      free = (diff >= 0) ? diff : rbuf->size+diff;

      if ( rest <= 0 ) return 0;
      if ( free < count ) count = free;
      
      if ( count < rest ){
            memcpy(data, rbuf->buffy+pos, count);
            rbuf->read_pos += count;
      } else {
            memcpy(data, rbuf->buffy+pos, rest);
            if ( count - rest)
                  memcpy(data+rest, rbuf->buffy, count - rest);
            rbuf->read_pos = count - rest;
      }

      return count;
}



int ring_write_file(ringbuffy *rbuf, int fd, int count)
{

      int diff, free, pos, rest, rr;

      if (count <=0 ) return 0;
            pos  = rbuf->write_pos;
      rest = rbuf->size - pos;
      diff = rbuf->read_pos - pos;
      free = (diff > 0) ? diff-1 : rbuf->size+diff-1;

      if ( rest <= 0 ) return 0;
      if ( free < count ) count = free;
      
      if (count >= rest){
            rr = read (fd, rbuf->buffy+pos, rest);
            if (rr == rest && count - rest)
                  rr += read (fd, rbuf->buffy, count - rest);
            if (rr >=0)
                  rbuf->write_pos = (pos + rr) % rbuf->size;
      } else {
            rr = read (fd, rbuf->buffy+pos, count);
            if (rr >=0)
                  rbuf->write_pos += rr;
      }

      return rr;
}



int ring_read_file(ringbuffy *rbuf, int fd, int count)
{

      int diff, free, pos, rest, rr;

      if (count <=0 ) return 0;
      pos  = rbuf->read_pos;
      rest = rbuf->size - pos;
      diff = rbuf->write_pos - pos;
      free = (diff >= 0) ? diff : rbuf->size+diff;

      if ( free <= 0 ) return FULL_BUFFER;
      if ( free < count ) count = free;

      if (count >= rest){
            rr = write (fd, rbuf->buffy+pos, rest);
            if (rr == rest && count - rest)
                  rr += write (fd, rbuf->buffy, count - rest);
            if (rr >=0)
                  rbuf->read_pos = (pos + rr) % rbuf->size;
      } else {
            rr = write (fd, rbuf->buffy+pos, count);
            if (rr >=0)
                  rbuf->read_pos += rr;
      }


      return rr;
}

int ring_rest(ringbuffy *rbuf){
            int diff, free, pos, rest;
      pos  = rbuf->read_pos;
      rest = rbuf->size - pos;
      diff = rbuf->write_pos - pos;
      free = (diff >= 0) ? diff : rbuf->size+diff;
      
      return free;
}

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