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/*
* ex_file_slice - Use slices to pack many objects into a single file.
*
* This example packs two strings into a single file, and then uses a
* file slice to open them one at a time. While this usage is contrived,
* the same principle can be used to pack multiple images (for example)
* into a single file, and later read them back via Allegro's image loader.
*
*/
#include "allegro5/allegro.h"
#include "common.c"
#define BUFFER_SIZE 1024
static void pack_object(ALLEGRO_FILE *file, const void *object, size_t len)
{
/* First write the length of the object, so we know how big to make
the slice when it is opened later. */
al_fwrite32le(file, len);
al_fwrite(file, object, len);
}
static ALLEGRO_FILE *get_next_chunk(ALLEGRO_FILE *file)
{
/* Reads the length of the next chunk, and if not at end of file, returns a
slice that represents that portion of the file. */
const uint32_t length = al_fread32le(file);
return !al_feof(file) ? al_fopen_slice(file, length, "rw") : NULL;
}
int main(int argc, const char *argv[])
{
ALLEGRO_FILE *master, *slice;
ALLEGRO_PATH *tmp_path;
const char *first_string = "Hello, World!";
const char *second_string = "The quick brown fox jumps over the lazy dog.";
char buffer[BUFFER_SIZE];
(void) argc, (void) argv;
if (!al_init()) {
abort_example("Could not init Allegro.\n");
}
open_log();
master = al_make_temp_file("ex_file_slice_XXXX", &tmp_path);
if (!master) {
abort_example("Unable to create temporary file\n");
}
/* Pack both strings into the master file. */
pack_object(master, first_string, strlen(first_string));
pack_object(master, second_string, strlen(second_string));
/* Seek back to the beginning of the file, as if we had just opened it */
al_fseek(master, 0, ALLEGRO_SEEK_SET);
/* Loop through the main file, opening a slice for each object */
while ((slice = get_next_chunk(master))) {
/* Note: While the slice is open, we must avoid using the master file!
If you were dealing with packed images, this is where you would pass 'slice'
to al_load_bitmap_f(). */
if (al_fsize(slice) < BUFFER_SIZE) {
/* We could have used al_fgets(), but just to show that the file slice
is constrained to the string object, we'll read the entire slice. */
al_fread(slice, buffer, al_fsize(slice));
buffer[al_fsize(slice)] = 0;
log_printf("Chunk of size %d: '%s'\n", (int) al_fsize(slice), buffer);
}
/* The slice must be closed before the next slice is opened. Closing
the slice will advanced the master file to the end of the slice. */
al_fclose(slice);
}
al_fclose(master);
al_remove_filename(al_path_cstr(tmp_path, '/'));
close_log(true);
return 0;
}
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