+#define ISAMC_BLOCK_OFFSET_N (sizeof(int)+sizeof(short))
+#define ISAMC_BLOCK_OFFSET_1 (sizeof(int)+sizeof(short)+sizeof(int))
+
+int isc_alloc_block (ISAMC is, int cat);
+void isc_release_block (ISAMC is, int cat, int pos);
+int isc_read_block (ISAMC is, int cat, int pos, char *dst);
+int isc_write_block (ISAMC is, int cat, int pos, char *src);