Extend the Mongoose-OS lib ili9341-spi and allows to draw DIFs driectly from memory

mgos_draw_dif_zipped.c

bool mgos_draw_dif_zipped(uint16_t x, uint16_t y, const char * difName) {
  struct mbuf *picRead = NULL;
  struct mbuf *picCache = NULL;
  char *bmpBuf = NULL;
  char *dif_hdr = NULL;
  char *dif_start = NULL;

  size_t bufLen = 0;
  size_t picLen = 0;
  size_t difhLen = 16;
  size_t w, h;

  bool doCache = true;
  doCache = doCache && (strstr(difName, "Heydo-Starting-0") == NULL);

  picRead = doCache ? (struct mbuf *) find_in_cache((char *) difName) : NULL;
  if (picRead != NULL) {
    LOG(LL_INFO, ("Found cache entry: pic size is <%ld>", (unsigned long) picRead->len));
    // just point to the start ...
    bmpBuf = picRead->buf;
    dif_hdr = bmpBuf;
    dif_start = (bmpBuf + difhLen);
    bufLen = picRead->len;
    picLen = bufLen - difhLen;
  } else {
    const char *archFile = mgos_sys_config_get_heydo_bmpArchFile();

    bufLen = mgos_get_zipped_buffer_size((char *) archFile, (char *) difName);
    if (doCache) {
      picCache = heap_caps_malloc(sizeof(struct mbuf), MALLOC_CAP_8BIT);
      picCache->buf = heap_caps_malloc (bufLen + 1, MALLOC_CAP_8BIT);
      picCache->len = bufLen;
      picCache->size = bufLen + 1;
      add_to_cache((char *) difName, (char *) picCache);
      //mbuf_init(picCache, bufLen);
      //mbuf_append(picCache, bmpBuf, bufLen);
      //mbuf_trim(picCache);
      bmpBuf = (char *) mgos_get_zipped_data(archFile, difName, picCache->buf, picCache->size);
    } else {
      bmpBuf = (char *) mgos_get_zipped_data(archFile, difName, NULL, 0);
    }
    if (!bmpBuf) {
      LOG(LL_ERROR, ("%s: Could not get zipped data from <%s>", difName, archFile));
      doCache = false;
      free(picCache->buf);
      free(picCache);
      picCache = NULL;
      return false;
    }

    if (doCache) {
      memcpy(picCache->buf, bmpBuf, bufLen);
    }

    // just point to the start ...
    dif_hdr = bmpBuf;
    dif_start = (bmpBuf + difhLen);
    picLen = bufLen - difhLen;

    if (dif_hdr[0] != 'D' || dif_hdr[1] != 'I' || dif_hdr[2] != 'F' || dif_hdr[3] != 1) {
      LOG(LL_ERROR, ("%s: Invalid DIF header", difName));
      mz_free(bmpBuf);
      return false;
    }
   
  }

  w = dif_hdr[7] + (dif_hdr[6] << 8) + (dif_hdr[5] << 16) + (dif_hdr[4] << 24);
  h = dif_hdr[11] + (dif_hdr[10] << 8) + (dif_hdr[9] << 16) + (dif_hdr[8] << 24);
  LOG(LL_INFO, ("%s: width=%d height=%d", difName, w, h));

  mgos_ili9341_sendPixels(x, y, w, h, (uint8_t *) dif_start, picLen);
  if (!doCache) {
    mz_free(bmpBuf);
  }

  return true;
}