ardupilot/libraries/AP_ROMFS/AP_ROMFS.cpp

/*
   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 3 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, see <http://www.gnu.org/licenses/>.
*/
/*
  implement a file store for embedded firmware images
 */

#include "AP_ROMFS.h"
#include "tinf.h"

#ifdef HAL_HAVE_AP_ROMFS_EMBEDDED_H
#include <ap_romfs_embedded.h>
#else
const AP_ROMFS::embedded_file AP_ROMFS::files[] = {};
#endif

/*
  find an embedded file
*/
const uint8_t *AP_ROMFS::find_file(const char *name, uint32_t &size)
{
    for (uint16_t i=0; i<ARRAY_SIZE_SIMPLE(files); i++) {
        if (strcmp(name, files[i].filename) == 0) {
            size = files[i].size;
            return files[i].contents;
        }
    }
    return nullptr;
}

/*
  find a compressed file and uncompress it. Space for decompressed
  data comes from malloc. Caller must be careful to free the resulting
  data after use.
*/
uint8_t *AP_ROMFS::find_decompress(const char *name, uint32_t &size)
{
    uint32_t compressed_size;
    const uint8_t *compressed_data = find_file(name, compressed_size);
    if (!compressed_data) {
        return nullptr;
    }

    // last 4 bytes of gzip file are length of decompressed data
    const uint8_t *p = &compressed_data[compressed_size-4];
    uint32_t decompressed_size = p[0] | p[1] << 8 | p[2] << 16 | p[3] << 24;
    
    uint8_t *decompressed_data = (uint8_t *)malloc(decompressed_size);
    if (!decompressed_data) {
        return nullptr;
    }

    TINF_DATA *d = (TINF_DATA *)malloc(sizeof(TINF_DATA));
    if (!d) {
        free(decompressed_data);
        return nullptr;
    }
    uzlib_uncompress_init(d, NULL, 0);

    d->source = compressed_data;
    d->source_limit = compressed_data + compressed_size - 4;

    // assume gzip format
    int res = uzlib_gzip_parse_header(d);
    if (res != TINF_OK) {
        free(decompressed_data);
        free(d);
        return nullptr;
    }

    d->dest = decompressed_data;
    d->destSize = decompressed_size;

    // we don't check CRC, as it just wastes flash space for constant
    // ROMFS data
    res = uzlib_uncompress(d);

    free(d);
    
    if (res != TINF_OK) {
        free(decompressed_data);
        return nullptr;
    }

    size = decompressed_size;
    return decompressed_data;
}