+/**
+ * @ingroup G_writing_and_overwriting_wims
+ *
+ * Set the compression chunk size of a WIM to use in subsequent calls to
+ * wimlib_write() or wimlib_overwrite().
+ *
+ * A compression chunk size will result in a greater compression ratio, but the
+ * speed of random access to the WIM will be reduced, and the effect of an
+ * increased compression chunk size is limited by the size of each file being
+ * compressed.
+ *
+ * <b>WARNING: Changing the compression chunk size to any value other than the
+ * default of 32768 bytes eliminates compatibility with Microsoft's software,
+ * except when increasing the XPRESS chunk size before Windows 8.</b>
+ *
+ * @param wim
+ * ::WIMStruct for a WIM.
+ * @param out_chunk_size
+ * The chunk size (in bytes) to set. The valid chunk sizes are dependent
+ * on the compression format. The XPRESS compression format supports chunk
+ * sizes that are powers of 2 with exponents between 15 and 26 inclusively,
+ * whereas the LZX compression format supports chunk sizes that are powers
+ * of 2 with exponents between 15 and 21 inclusively.
+ *
+ * @return 0 on success; nonzero on error.
+ *
+ * @retval ::WIMLIB_ERR_INVALID_CHUNK_SIZE
+ * @p ctype is not a supported chunk size.
+ */
+extern int
+wimlib_set_output_chunk_size(WIMStruct *wim, uint32_t chunk_size);
+
+/**
+ * @ingroup G_writing_and_overwriting_wims
+ *
+ * Set the compression type of a WIM to use in subsequent calls to
+ * wimlib_write() or wimlib_overwrite().
+ *
+ * @param wim
+ * ::WIMStruct for a WIM.
+ * @param ctype
+ * The compression type to set (one of ::wimlib_compression_type). If this
+ * compression type is incompatible with the current output chunk size
+ * (either the default or as set with wimlib_set_output_chunk_size()), the
+ * output chunk size is reset to the default for that compression type.
+ *
+ * @return 0 on success; nonzero on error.
+ *
+ * @retval ::WIMLIB_ERR_INVALID_PARAM
+ * @p ctype did not specify a valid compression type.
+ */
+extern int
+wimlib_set_output_compression_type(WIMStruct *wim, int ctype);
+