buffer.c

网络端口的服务程序

/*
    Portserver - Use RTERM protocol to serve serial ports over a network
    Copyright (C) 1998 Kenn Humborg

    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 <stdlib.h>
#include <string.h>
#include "buffer.h"

/* Adds data to a buffer.  Returns TRUE when buffer is full */

int BufferAdd(struct Buffer *buf, char *data, int data_len, int *bytes_added)
{
   int space_remaining;
   int bytes_to_copy;

   space_remaining = buf->length - buf->data_length;

   if (space_remaining >= data_len) {
      bytes_to_copy = data_len;
   } else {
      bytes_to_copy = space_remaining;
   }

   memcpy(buf->data + buf->data_length, data, bytes_to_copy);

   buf->data_length += bytes_to_copy;

   *bytes_added = bytes_to_copy;

   return (buf->data_length == buf->length);
}


/* Removes data from a buffer.  Returns TRUE when the buffer is empty */

int BufferRemove(struct Buffer *buf, int data_len)
{
   int bytes_to_move;

   if (data_len >= buf->data_length) {
      buf->data_length = 0;
   } else {
      bytes_to_move = buf->data_length - data_len;
      memmove(buf->data, buf->data + data_len, bytes_to_move);
      buf->data_length -= data_len;
   }

   return (buf->data_length == 0);
}


/* Create a buffer, returns NULL if error */
STATUS BufferCreate(int buffer_size, struct Buffer **new_buffer)
{
   struct Buffer *buf;

   buf = malloc(sizeof(struct Buffer));
   if (buf == NULL) {
      return ERR_NOMEMORY;
   }

   buf->data = malloc(buffer_size);

   if (buf->data == NULL) {
      free(buf);
      return ERR_NOMEMORY;
   }

   buf->length = buffer_size;
   buf->data_length = 0;

   *new_buffer = buf;

   return SUCCESS;
}

void BufferDelete(struct Buffer *buf)
{
   free(buf->data);
   free(buf);
}