Repurpose two unused header fields to store biggest image sector size.

include/aaruformat/structs/header.h

@@ -117,8 +117,7 @@ typedef struct AaruHeaderV2
     int64_t  lastWrittenTime;  ///< Last modification FILETIME (100 ns since 1601-01-01 UTC).
     uint8_t  guid[GUID_SIZE];  ///< 128-bit image GUID (binary, not text); stable across children.
     uint8_t  blockAlignmentShift;  ///< log2 block alignment (block size alignment = 2^blockAlignmentShift bytes).
-    uint8_t  dataShift;            ///< log2 sectors/items per block-index increment in DDT entries (2^dataShift).
-    uint8_t  tableShift;           ///< log2 sectors spanned by each primary DDT entry (0 = single-level).
+    uint16_t biggestSectorSize;    ///< size of biggest sector in the image (in bytes).
     uint64_t featureCompatible;    ///< Feature bits: unimplemented bits are ignorable (still R/W safe).
     uint64_t featureCompatibleRo;  ///< Feature bits: unimplemented -> degrade to read-only access.
     uint64_t featureIncompatible;  ///< Feature bits: any unimplemented -> abort (cannot open safely).

src/write.c

@@ -16,6 +16,7 @@
  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  */
 #include <errno.h>
+#include <limits.h>
 #include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
@@ -146,6 +147,8 @@ AARU_EXPORT int32_t AARU_CALL aaruf_write_sector(void *context, uint64_t sector_
         return AARUF_ERROR_SECTOR_OUT_OF_BOUNDS;
     }
 
+    if(length > ctx->header.biggestSectorSize) ctx->header.biggestSectorSize = (uint16_t)length;
+
     if(!ctx->rewinded)
     {
         if(sector_address <= ctx->last_written_block)

templates/aaruformat.bt

@@ -784,8 +784,7 @@ typedef struct
     {
         GUID               guid;
         byte               blockAlignmentShift;
-        byte               dataShift;
-        byte               tableShift;
+        uint16             biggestSectorSize;
         FeaturesCompatible featureCompatible;
         uint64             featureCompatibleRo;
         uint64             featureIncompatible;

templates/aaruformat.hexpat

@@ -811,8 +811,7 @@ struct AaruHeader
     {
         type::GUID  guid;
         u8          blockAlignmentShift;
-        u8          dataShift;
-        u8          tableShift;
+        u16         biggestSectorSize;
         u64         featureCompatible;
         u64         featureCompatibleRo;
         u64         featureIncompatible;

tool/upgrade_ddt_to_alpha21.c

@@ -106,8 +106,7 @@ int upgrade_ddt_to_alpha21(const char *path)
     printf("  Index offset: %llu bytes\n", (unsigned long long)header.indexOffset);
     printf("  Media type: %u (%s)\n", header.mediaType, media_type_to_string(header.mediaType));
     printf("  Block alignment shift: %u\n", header.blockAlignmentShift);
-    printf("  Data shift: %u\n", header.dataShift);
-    printf("  Table shift: %u\n", header.tableShift);
+    printf("  Biggest sector size: %u bytes\n", header.biggestSectorSize);
 
     // Display important warnings
     printf("\n");