+ WIMStruct *wim = CALLOC(1, sizeof(WIMStruct));
+ if (wim) {
+ filedes_invalidate(&wim->in_fd);
+ filedes_invalidate(&wim->out_fd);
+ wim->out_pack_compression_type = wim_default_pack_compression_type();
+ wim->out_pack_chunk_size = wim_default_pack_chunk_size(
+ wim->out_pack_compression_type);
+ INIT_LIST_HEAD(&wim->subwims);
+ }
+ return wim;
+}
+
+/* Determine if the chunk size is valid for the specified compression type. */
+static bool
+wim_chunk_size_valid(u32 chunk_size, int ctype)
+{
+ u32 order;
+
+ /* Chunk size is meaningless for uncompressed WIMs --- any value is
+ * okay. */
+ if (ctype == WIMLIB_COMPRESSION_TYPE_NONE)
+ return true;
+
+ /* Chunk size must be power of 2. */
+ if (chunk_size == 0)
+ return false;
+ order = bsr32(chunk_size);
+ if (chunk_size != 1U << order)
+ return false;
+
+ /* Order Size
+ * ===== ====
+ * 15 32768
+ * 16 65536
+ * 17 131072
+ * 18 262144
+ * 19 524288
+ * 20 1048576
+ * 21 2097152
+ * 22 4194304
+ * 23 8388608
+ * 24 16777216
+ * 25 33554432
+ * 26 67108864
+ */
+
+ /* See the documentation for the --chunk-size option of `wimlib-imagex
+ * capture' for information about allowed chunk sizes. */
+ switch (ctype) {
+ case WIMLIB_COMPRESSION_TYPE_LZX:
+ return order >= 15 && order <= 21;
+
+ case WIMLIB_COMPRESSION_TYPE_XPRESS:
+ return order >= 12 && order <= 26;
+ case WIMLIB_COMPRESSION_TYPE_LZMS:
+ return order >= 15 && order <= 30;
+ }
+ return false;
+}
+
+/* Return the default chunk size to use for the specified compression type.
+ *
+ * See notes above in wim_chunk_size_valid(). */
+static u32
+wim_default_chunk_size(int ctype)
+{
+ switch (ctype) {
+ case WIMLIB_COMPRESSION_TYPE_LZMS:
+ return 1U << 17; /* 131072 */
+ default:
+ return 1U << 15; /* 32768 */