int t3f_save_animation_f(T3F_ANIMATION * ap, ALLEGRO_FILE * fp)
{
int i;
ani_header[11] = T3F_ANIMATION_REVISION; // put the version number in
al_fwrite(fp, ani_header, 12);
al_fwrite16le(fp, ap->bitmaps->count);
for(i = 0; i < ap->bitmaps->count; i++)
{
if(!t3f_save_bitmap_f(fp, ap->bitmaps->bitmap[i]))
{
printf("failed to save bitmap\n");
return 0;
}
}
al_fwrite16le(fp, ap->frames);
for(i = 0; i < ap->frames; i++)
{
al_fwrite16le(fp, ap->frame[i]->bitmap);
t3f_fwrite_float(fp, ap->frame[i]->x);
t3f_fwrite_float(fp, ap->frame[i]->y);
t3f_fwrite_float(fp, ap->frame[i]->z);
t3f_fwrite_float(fp, ap->frame[i]->width);
t3f_fwrite_float(fp, ap->frame[i]->height);
t3f_fwrite_float(fp, ap->frame[i]->angle);
al_fwrite32le(fp, ap->frame[i]->ticks);
al_fwrite32le(fp, ap->frame[i]->flags);
}
al_fwrite32le(fp, ap->flags);
return 1;
}
static size_t slice_fwrite(ALLEGRO_FILE *f, const void *ptr, size_t size)
{
SLICE_DATA *slice = al_get_file_userdata(f);
if (!(slice->mode & SLICE_WRITE)) {
/* no write permissions */
return 0;
}
if (!(slice->mode & SLICE_EXPANDABLE) && slice->pos + size > slice->size) {
/* don't write past the buffer size if not expandable */
size = slice->size - slice->pos;
}
if (!size) {
return 0;
}
else {
/* unbuffered, write directly to parent file */
size_t b = al_fwrite(slice->fp, ptr, size);
slice->pos += b;
if (slice->pos > slice->size)
slice->size = slice->pos;
return b;
}
}
bool t3f_save_vector_object_f(T3F_VECTOR_OBJECT * vp, ALLEGRO_FILE * fp)
{
unsigned char r, g, b, a;
char header[16] = {'T', '3', 'F', 'V'};
int i;
if(al_fwrite(fp, header, 16) != 16)
{
return false;
}
al_fwrite32le(fp, vp->segments);
for(i = 0; i < vp->segments; i++)
{
t3f_fwrite_float(fp, vp->segment[i]->point[0].x);
t3f_fwrite_float(fp, vp->segment[i]->point[0].y);
t3f_fwrite_float(fp, vp->segment[i]->point[0].z);
t3f_fwrite_float(fp, vp->segment[i]->point[1].x);
t3f_fwrite_float(fp, vp->segment[i]->point[1].y);
t3f_fwrite_float(fp, vp->segment[i]->point[1].z);
al_unmap_rgba(vp->segment[i]->color, &r, &g, &b, &a);
al_fputc(fp, r);
al_fputc(fp, g);
al_fputc(fp, b);
al_fputc(fp, a);
t3f_fwrite_float(fp, vp->segment[i]->thickness);
}
return true;
}
void CDisplay::UpdateHighScores()
{
for(int i = 0; i < numHighScores; i++) {
long tempScore = atol(highScores[i]);
if(score > tempScore) {
for(int j = numHighScores - 1; j > i; j--)
highScores[j] = highScores[j - 1];
highScores[i] = ltoa(score, new char[16], 10);
break;
}
}
ALLEGRO_FILE* file;
file = al_fopen("C:\\Users\\Chase\\Documents\\Visual Studio 2010\\Projects\\Tetris\\scores.scr", "w+b");
if(!file) {
printf("File scores.scr could not be opened\n");
return;
}
for(int i = 0; i < numHighScores; i++) {
long tempScore = atol(highScores[i]);
al_fwrite(file, &tempScore, 8);
}
al_fclose(file);
printf("File written to");
}
int t3f_save_tilemap_f(T3F_TILEMAP * tmp, ALLEGRO_FILE * fp)
{
int i, j, k;
char header[16] = {0};
strcpy(header, "T3F_TILEMAP");
header[15] = 0;
al_fwrite(fp, header, 16);
al_fwrite16le(fp, tmp->layers);
for(i = 0; i < tmp->layers; i++)
{
al_fwrite16le(fp, tmp->layer[i]->width);
al_fwrite16le(fp, tmp->layer[i]->height);
for(j = 0; j < tmp->layer[i]->height; j++)
{
for(k = 0; k < tmp->layer[i]->width; k++)
{
al_fwrite16le(fp, tmp->layer[i]->data[j][k]);
}
}
t3f_fwrite_float(fp, tmp->layer[i]->x);
t3f_fwrite_float(fp, tmp->layer[i]->y);
t3f_fwrite_float(fp, tmp->layer[i]->z);
t3f_fwrite_float(fp, tmp->layer[i]->scale);
t3f_fwrite_float(fp, tmp->layer[i]->speed_x);
t3f_fwrite_float(fp, tmp->layer[i]->speed_y);
al_fwrite32le(fp, tmp->layer[i]->flags);
}
al_fwrite32le(fp, tmp->flags);
return 1;
}
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 boolean empty_output_buffer(j_compress_ptr cinfo)
{
struct my_dest_mgr *dest = (void *)cinfo->dest;
al_fwrite(dest->fp, dest->buffer, BUFFER_SIZE);
dest->pub.next_output_byte = dest->buffer;
dest->pub.free_in_buffer = BUFFER_SIZE;
return 1;
}
int inf(ALLEGRO_FILE *source, ALLEGRO_FILE *dest)
{
int ret;
unsigned have;
z_stream strm;
unsigned char in[CHUNK];
unsigned char out[CHUNK];
/* allocate inflate state */
strm.zalloc = Z_NULL;
strm.zfree = Z_NULL;
strm.opaque = Z_NULL;
strm.avail_in = 0;
strm.next_in = Z_NULL;
ret = inflateInit(&strm);
if (ret != Z_OK)
return ret;
/* decompress until deflate stream ends or end of file */
do {
strm.avail_in = al_fread(source, in, CHUNK);
if (al_ferror(source)) {
(void)inflateEnd(&strm);
return Z_ERRNO;
}
if (strm.avail_in == 0)
break;
strm.next_in = in;
/* run inflate() on input until output buffer not full */
do {
strm.avail_out = CHUNK;
strm.next_out = out;
ret = inflate(&strm, Z_NO_FLUSH);
assert(ret != Z_STREAM_ERROR); /* state not clobbered */
switch (ret) {
case Z_NEED_DICT:
ret = Z_DATA_ERROR; /* and fall through */
case Z_DATA_ERROR:
case Z_MEM_ERROR:
(void)inflateEnd(&strm);
return ret;
}
have = CHUNK - strm.avail_out;
if (al_fwrite(dest, out, have) != have || al_ferror(dest)) {
(void)inflateEnd(&strm);
return Z_ERRNO;
}
} while (strm.avail_out == 0);
/* done when inflate() says it's done */
} while (ret != Z_STREAM_END);
/* clean up and return */
(void)inflateEnd(&strm);
return ret == Z_STREAM_END ? Z_OK : Z_DATA_ERROR;
}
int t3f_save_tileset_f(T3F_TILESET * tsp, ALLEGRO_FILE * fp)
{
int i, j;
char header[16] = {0};
strcpy(header, "T3F_TILESET");
header[15] = 0;
al_fwrite(fp, header, 16);
/* write tile data */
al_fwrite16le(fp, tsp->tiles);
for(i = 0; i < tsp->tiles; i++)
{
t3f_save_animation_f(tsp->tile[i]->ap, fp);
al_fwrite32le(fp, tsp->tile[i]->flags);
/* write user data */
if(tsp->tile[i]->flags & T3F_TILE_FLAG_USER_DATA)
{
for(j = 0; j < T3F_TILE_MAX_DATA; j++)
{
al_fwrite32le(fp, tsp->tile[i]->user_data[j]);
}
}
/* write animation frames */
al_fwrite32le(fp, tsp->tile[i]->frame_list_total);
for(j = 0; j < tsp->tile[i]->frame_list_total; j++)
{
al_fwrite16le(fp, tsp->tile[i]->frame_list[j]);
}
}
/* write tileset data */
al_fwrite32le(fp, tsp->width);
al_fwrite32le(fp, tsp->height);
al_fwrite32le(fp, tsp->flags);
return 1;
}
bool t3f_save_vector_font_f(T3F_VECTOR_FONT * vfp, ALLEGRO_FILE * fp)
{
char header[16] = {'T', '3', 'F', 'V', 'F'};
int i;
if(al_fwrite(fp, header, 16) != 16)
{
return false;
}
for(i = 0; i < T3F_VECTOR_FONT_MAX_CHARACTERS; i++)
{
if(vfp->character[i])
{
al_fputc(fp, 1);
t3f_save_vector_object_f(vfp->character[i]->object, fp);
t3f_fwrite_float(fp, vfp->character[i]->width);
}
else
{
al_fputc(fp, 0);
}
}
return true;
}
static void mixer_pp_callback(void *buf, unsigned int samples, void *userdata)
{
ALLEGRO_MIXER *mixer = (ALLEGRO_MIXER *)userdata;
int nch;
int sample_size;
if (!saving)
return;
switch (al_get_mixer_channels(mixer)) {
case ALLEGRO_CHANNEL_CONF_1:
nch = 1;
break;
case ALLEGRO_CHANNEL_CONF_2:
nch = 2;
break;
default:
/* Not supported. */
return;
}
sample_size = al_get_audio_depth_size(al_get_mixer_depth(mixer));
al_fwrite(save_fp, buf, nch * samples * sample_size);
}
static void term_destination(j_compress_ptr cinfo)
{
struct my_dest_mgr *dest = (void *)cinfo->dest;
al_fwrite(dest->fp, dest->buffer, BUFFER_SIZE - dest->pub.free_in_buffer);
}
void mapSaver::writeData(ALLEGRO_FILE* fileStream) {
unsigned int offset_settings = 0;
unsigned int offset_collision = 0;
unsigned int offset_tile = 0;
unsigned int offset_background = 0;
//Reserve room for the header
for (unsigned int i=0; i<4*sizeof(unsigned int); i++) {
al_fputc(fileStream,0);
}
offset_settings = al_ftell(fileStream);
//Write map dimensions
al_fwrite(fileStream,&_mData.left,sizeof(int)); //Write position on map
al_fwrite(fileStream,&_mData.top,sizeof(int)); //Write position on map
al_fwrite(fileStream,&_mData.right,sizeof(int)); //Write position on map
al_fwrite(fileStream,&_mData.bottom,sizeof(int)); //Write position on map
offset_collision = al_ftell(fileStream);
int collisionLineList = _mData.getCollisionLineCount();
al_fwrite(fileStream,&collisionLineList, sizeof(int)); //Write number of collision lines
for (collisionLineListNode* i = _mData.getRootCollisionLine(); i!=NULL; i=i->next) { //Iterate through all the lines
int buffer;
buffer = i->line->p1.x;
al_fwrite(fileStream,&buffer,sizeof(int)); //Line beginning
buffer = i->line->p1.y;
al_fwrite(fileStream,&buffer,sizeof(int)); //Line beginning
buffer = i->line->p2.x;
al_fwrite(fileStream,&buffer,sizeof(int)); //Line end
buffer = i->line->p2.y;
al_fwrite(fileStream,&buffer,sizeof(int)); //line end
al_fwrite(fileStream,&i->line->jumpthrough,sizeof(bool)); //jumpthrough?
}
offset_tile = al_ftell(fileStream);
int layerList = _mData.tileLayers.size();
al_fwrite(fileStream,&layerList, sizeof(int)); //Write number of tile Layers
for (unsigned int i=0; i<_mData.tileLayers.size(); i++) {
int layoutList = _mData.tileLayers[i]->layouts.size();
al_fwrite(fileStream, &layoutList, sizeof(int)); //Write number of layouts.
for (unsigned int j=0; j<layoutList; j++) {
int tileList = _mData.tileLayers[i]->layouts[j]->tilePositions.size();
al_fwrite(fileStream,&_mData.tileLayers[i]->layouts[j]->tilesetData->tilesetID, sizeof(short)); //Write ID of tileset
al_fwrite(fileStream,&tileList, sizeof(int)); //Number of tiles
for (unsigned int c=0; c<tileList; c++) {
al_fwrite(fileStream,&_mData.tileLayers[i]->layouts[j]->tilePositions[c]->mapX,sizeof(int)); //Write position on map
al_fwrite(fileStream,&_mData.tileLayers[i]->layouts[j]->tilePositions[c]->mapY,sizeof(int)); //Write position on map
al_fwrite(fileStream,&_mData.tileLayers[i]->layouts[j]->tilePositions[c]->tileSetX,sizeof(short)); //Write position on tileset (pos*width)
al_fwrite(fileStream,&_mData.tileLayers[i]->layouts[j]->tilePositions[c]->tileSetY,sizeof(short)); //Write position on tileset (pos*height)
}
}
}
offset_background = al_ftell(fileStream);
//Background layers
int LayerCount = _mData.backgroundLayers.size();
al_fwrite(fileStream,&LayerCount, sizeof(int)); //Write number of background layers
for (int i=0; i<_mData.backgroundLayers.size(); i++) {
int buffer;
buffer = _mData.backgroundLayers[i]->bgHandle->id;
al_fwrite(fileStream,&buffer,sizeof(int)); //BG ID
buffer = _mData.backgroundLayers[i]->xPos;
al_fwrite(fileStream,&buffer,sizeof(int)); //x position
buffer = _mData.backgroundLayers[i]->yPos;
al_fwrite(fileStream,&buffer,sizeof(int)); //Y position
}
al_fseek(fileStream,0,ALLEGRO_SEEK_SET);
al_fwrite(fileStream,&offset_settings,sizeof(int)); //Write position on map
al_fwrite(fileStream,&offset_collision,sizeof(int)); //Write position on map
al_fwrite(fileStream,&offset_tile,sizeof(int)); //Write position on map
al_fwrite(fileStream,&offset_background,sizeof(int)); //Write position on map
}
int main(int argc, char **argv)
{
ALLEGRO_AUDIO_RECORDER *r;
ALLEGRO_AUDIO_STREAM *s;
ALLEGRO_EVENT_QUEUE *q;
ALLEGRO_DISPLAY *d;
ALLEGRO_FILE *fp = NULL;
ALLEGRO_PATH *tmp_path = NULL;
int prev = 0;
bool is_recording = false;
int n = 0; /* number of samples written to disk */
(void) argc;
(void) argv;
if (!al_init()) {
abort_example("Could not init Allegro.\n");
}
if (!al_init_primitives_addon()) {
abort_example("Unable to initialize primitives addon");
}
if (!al_install_keyboard()) {
abort_example("Unable to install keyboard");
}
if (!al_install_audio()) {
abort_example("Unable to initialize audio addon");
}
if (!al_init_acodec_addon()) {
abort_example("Unable to initialize acodec addon");
}
/* Note: increasing the number of channels will break this demo. Other
* settings can be changed by modifying the constants at the top of the
* file.
*/
r = al_create_audio_recorder(1000, samples_per_fragment, frequency,
audio_depth, ALLEGRO_CHANNEL_CONF_1);
if (!r) {
abort_example("Unable to create audio recorder");
}
s = al_create_audio_stream(playback_fragment_count,
playback_samples_per_fragment, frequency, audio_depth,
ALLEGRO_CHANNEL_CONF_1);
if (!s) {
abort_example("Unable to create audio stream");
}
al_reserve_samples(0);
al_set_audio_stream_playing(s, false);
al_attach_audio_stream_to_mixer(s, al_get_default_mixer());
q = al_create_event_queue();
/* Note: the following two options are referring to pixel samples, and have
* nothing to do with audio samples. */
al_set_new_display_option(ALLEGRO_SAMPLE_BUFFERS, 1, ALLEGRO_SUGGEST);
al_set_new_display_option(ALLEGRO_SAMPLES, 8, ALLEGRO_SUGGEST);
d = al_create_display(320, 256);
if (!d) {
abort_example("Error creating display\n");
}
al_set_window_title(d, "SPACE to record. P to playback.");
al_register_event_source(q, al_get_audio_recorder_event_source(r));
al_register_event_source(q, al_get_audio_stream_event_source(s));
al_register_event_source(q, al_get_display_event_source(d));
al_register_event_source(q, al_get_keyboard_event_source());
al_start_audio_recorder(r);
while (true) {
ALLEGRO_EVENT e;
al_wait_for_event(q, &e);
if (e.type == ALLEGRO_EVENT_AUDIO_RECORDER_FRAGMENT) {
/* We received an incoming fragment from the microphone. In this
* example, the recorder is constantly recording even when we aren't
* saving to disk. The display is updated every time a new fragment
* comes in, because it makes things more simple. If the fragments
* are coming in faster than we can update the screen, then it will be
* a problem.
*/
ALLEGRO_AUDIO_RECORDER_EVENT *re = al_get_audio_recorder_event(&e);
audio_buffer_t input = (audio_buffer_t) re->buffer;
int sample_count = re->samples;
const int R = sample_count / 320;
int i, gain = 0;
/* Calculate the volume, and display it regardless if we are actively
* recording to disk. */
for (i = 0; i < sample_count; ++i) {
if (gain < abs(input[i] - sample_center))
gain = abs(input[i] - sample_center);
}
al_clear_to_color(al_map_rgb(0,0,0));
if (is_recording) {
/* Save raw bytes to disk. Assumes everything is written
* succesfully. */
if (fp && n < frequency / (float) samples_per_fragment *
max_seconds_to_record) {
al_fwrite(fp, input, sample_count * sample_size);
++n;
}
/* Draw a pathetic visualization. It draws exactly one fragment
* per frame. This means the visualization is dependent on the
* various parameters. A more thorough implementation would use this
* event to copy the new data into a circular buffer that holds a
* few seconds of audio. The graphics routine could then always
* draw that last second of audio, which would cause the
* visualization to appear constant across all different settings.
*/
for (i = 0; i < 320; ++i) {
int j, c = 0;
/* Take the average of R samples so it fits on the screen */
for (j = i * R; j < i * R + R && j < sample_count; ++j) {
c += input[j] - sample_center;
}
c /= R;
/* Draws a line from the previous sample point to the next */
al_draw_line(i - 1, 128 + ((prev - min_sample_val) /
(float) sample_range) * 256 - 128, i, 128 +
((c - min_sample_val) / (float) sample_range) * 256 - 128,
al_map_rgb(255,255,255), 1.2);
prev = c;
}
}
/* draw volume bar */
al_draw_filled_rectangle((gain / (float) max_sample_val) * 320, 251,
0, 256, al_map_rgba(0, 255, 0, 128));
al_flip_display();
}
else if (e.type == ALLEGRO_EVENT_AUDIO_STREAM_FRAGMENT) {
/* This event is received when we are playing back the audio clip.
* See ex_saw.c for an example dedicated to playing streams.
*/
if (fp) {
audio_buffer_t output = al_get_audio_stream_fragment(s);
if (output) {
/* Fill the buffer from the data we have recorded into the file.
* If an error occurs (or end of file) then silence out the
* remainder of the buffer and stop the playback.
*/
const size_t bytes_to_read =
playback_samples_per_fragment * sample_size;
size_t bytes_read = 0, i;
do {
bytes_read += al_fread(fp, (uint8_t *)output + bytes_read,
bytes_to_read - bytes_read);
} while (bytes_read < bytes_to_read && !al_feof(fp) &&
!al_ferror(fp));
/* silence out unused part of buffer (end of file) */
for (i = bytes_read / sample_size;
i < bytes_to_read / sample_size; ++i) {
output[i] = sample_center;
}
al_set_audio_stream_fragment(s, output);
if (al_ferror(fp) || al_feof(fp)) {
al_drain_audio_stream(s);
al_fclose(fp);
fp = NULL;
}
}
}
}
else if (e.type == ALLEGRO_EVENT_DISPLAY_CLOSE) {
break;
}
else if (e.type == ALLEGRO_EVENT_KEY_CHAR) {
if (e.keyboard.unichar == 27) {
/* pressed ESC */
break;
}
else if (e.keyboard.unichar == ' ') {
if (!is_recording) {
/* Start the recording */
is_recording = true;
if (al_get_audio_stream_playing(s)) {
al_drain_audio_stream(s);
}
/* Reuse the same temp file for all recordings */
if (!tmp_path) {
fp = al_make_temp_file("alrecXXX.raw", &tmp_path);
}
else {
if (fp) al_fclose(fp);
fp = al_fopen(al_path_cstr(tmp_path, '/'), "w");
}
n = 0;
}
else {
is_recording = false;
if (fp) {
al_fclose(fp);
fp = NULL;
}
}
}
else if (e.keyboard.unichar == 'p') {
/* Play the previously recorded wav file */
if (!is_recording) {
if (tmp_path) {
fp = al_fopen(al_path_cstr(tmp_path, '/'), "r");
if (fp) {
al_set_audio_stream_playing(s, true);
}
}
}
}
}
}
/* clean up */
al_destroy_audio_recorder(r);
al_destroy_audio_stream(s);
if (fp)
al_fclose(fp);
if (tmp_path) {
al_remove_filename(al_path_cstr(tmp_path, '/'));
al_destroy_path(tmp_path);
}
return 0;
}
/*
* Decodes map data from a <data> node
*/
static void decode_layer_data(xmlNode *data_node, ALLEGRO_MAP_LAYER *layer)
{
char *str = g_strstrip((char *)data_node->children->content);
int datalen = layer->width * layer->height;
layer->data = (char *)calloc(datalen, sizeof(char));
char *encoding = get_xml_attribute(data_node, "encoding");
if (!encoding) {
int i = 0;
GSList *tiles = get_children_for_name(data_node, "tile");
GSList *tile_item = tiles;
while (tile_item) {
xmlNode *tile_node = (xmlNode*)tile_item->data;
tile_item = g_slist_next(tile_item);
char *gid = get_xml_attribute(tile_node, "gid");
layer->data[i] = atoi(gid);
i++;
}
g_slist_free(tiles);
}
else if (!strcmp(encoding, "base64")) {
// decompress
gsize rawlen;
unsigned char *rawdata = g_base64_decode(str, &rawlen);
// check the compression
char *compression = get_xml_attribute(data_node, "compression");
if (compression != NULL) {
if (strcmp(compression, "zlib") && strcmp(compression, "gzip")) {
fprintf(stderr, "Error: unknown compression format '%s'\n", compression);
return;
}
// set up files used by zlib to decompress the data
ALLEGRO_PATH *srcpath;
ALLEGRO_FILE *datasrc = al_make_temp_file("XXXXXX", &srcpath);
al_fwrite(datasrc, rawdata, rawlen);
al_fseek(datasrc, 0, ALLEGRO_SEEK_SET);
//al_fclose(datasrc);
//datasrc = al_fopen(al_path_cstr(srcpath, ALLEGRO_NATIVE_PATH_SEP), "rb");
ALLEGRO_FILE *datadest = al_make_temp_file("XXXXXX", NULL);
// decompress and print an error if it failed
int status = inf(datasrc, datadest);
if (status)
zerr(status);
// flush data and get the file length
al_fflush(datadest);
int len = al_fsize(datadest);
// read in the file
al_fseek(datadest, 0, ALLEGRO_SEEK_SET);
char *data = (char *)calloc(len, sizeof(char));
if (al_fread(datadest, data, len) != len) {
fprintf(stderr, "Error: failed to read in map data\n");
return;
}
// every tile id takes 4 bytes
int i;
for (i = 0; i<len; i += 4) {
int tileid = 0;
tileid |= data[i];
tileid |= data[i+1] << 8;
tileid |= data[i+2] << 16;
tileid |= data[i+3] << 24;
layer->data[i/4] = tileid;
}
/* printf("layer dimensions: %dx%d, data length = %d\n",
layer->width, layer->height, len); */
al_destroy_path(srcpath);
al_fclose(datasrc);
al_fclose(datadest);
al_free(data);
}
else {
// TODO: verify that this still works
int i;
for (i = 0; i<rawlen; i += 4) {
int tileid = 0;
tileid |= rawdata[i];
tileid |= rawdata[i+1] << 8;
tileid |= rawdata[i+2] << 16;
tileid |= rawdata[i+3] << 24;
layer->data[i/4] = tileid;
}
}
g_free(rawdata);
}
else if (!strcmp(encoding, "csv")) {
int i;
for (i = 0; i<datalen; i++) {
char *id = strtok((i == 0 ? str : NULL), ",");
layer->data[i] = atoi(id);
}
}
else {
fprintf(stderr, "Error: unknown encoding format '%s'\n", encoding);
}
}
/* write_data:
* Custom write function to use Allegro packfile routines,
* rather than C streams.
*/
static void write_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
{
ALLEGRO_FILE *f = (ALLEGRO_FILE *)png_get_io_ptr(png_ptr);
if ((png_uint_32) al_fwrite(f, data, length) != length)
png_error(png_ptr, "write error (loadpng calling al_fs_entry_write)");
}