src/aviwriter/avi_rw_iobuf.cpp

/*
 *  Copyright (C) 2018-2020 Jon Campbell
 *
 *  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.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */

#include <string.h>
#include <stdlib.h>
#include "rawint.h"
#include "avi_rw_iobuf.h"
#include <stdlib.h>
#include <unistd.h>
#include <ctype.h>

/* common index writing code.
 * This code originally wrote the index one struct at a type.
 * If you know anything about syscall overhead and disk I/O,
 * that's a VERY inefficent way to do it! So index read/write
 * code uses our buffer to batch the index entries into RAM
 * and write them to disk in one burst */
unsigned char*          avi_io_buf = NULL;
unsigned char*          avi_io_read = NULL;
unsigned char*          avi_io_write = NULL;
unsigned char*          avi_io_fence = NULL;
size_t                  avi_io_elemsize = 0;
size_t                  avi_io_next_adv = 0;
size_t                  avi_io_elemcount = 0;
unsigned char*          avi_io_readfence = NULL;

unsigned char *avi_io_buffer_init(size_t structsize) {
#define GROUPSIZE ((size_t)(65536*2))
        if (avi_io_buf == NULL) {
                avi_io_buf = (unsigned char*)malloc(GROUPSIZE);
                if (avi_io_buf == NULL) return NULL;
        }

        avi_io_elemcount = GROUPSIZE / structsize;
        avi_io_fence = avi_io_buf + (avi_io_elemcount * structsize);
        avi_io_readfence = avi_io_buf;
        avi_io_elemsize = structsize;
        avi_io_write = avi_io_buf;
        avi_io_read = avi_io_buf;
        return avi_io_buf;
#undef GROUPSIZE
}

void avi_io_buffer_free() {
        if (avi_io_buf) {
                free(avi_io_buf);
                avi_io_buf = NULL;
        }
        avi_io_readfence = avi_io_buf;
        avi_io_write = avi_io_buf;
        avi_io_read = avi_io_buf;
}