Define DDT2 header.

docs/spec/blocks/ddt2.adoc

@@ -4,7 +4,47 @@ The deduplication table is a multi-level table of pointers to LBAs contained in
 It starts with the following header.
 
 [source,c]
-/* Undefined */
+typedef struct DdtHeader2
+{
+    /**Identifier, <see cref="BlockType.DeDuplicationTable" /> */
+    uint32_t identifier;
+    /**Type of data pointed by this DDT */
+    uint16_t type;
+    /**Compression algorithm used to compress the DDT */
+    uint16_t compression;
+    /**How many levels of subtables are present */
+    uint8_t  levels;
+    /**Which level this table belongs to */
+    uint8_t  tableLevel;
+    /**Pointer to absolute byte offset in file where the previous level table is located */
+    uint64_t previousLevelOffset;
+    /**Negative displacement of LBAs */
+    uint16_t negative;
+    /**Number of blocks in media */
+    uint64_t blocks;
+    /**Positive overflow displacement of LBAs */
+    uint16_t overflow;
+    /**First LBA contained in this table */
+    uint64_t start;
+    /**Block alignment boundaries */
+    uint8_t  blockAlignmentShift;
+    /**Data shift */
+    uint8_t  dataShift;
+    /**Table shift */
+    uint8_t  tableShift;
+    /**Size type */
+    uint8_t  sizeType;
+    /**Entries in this table */
+    uint64_t entries;
+    /**Compressed length for the DDT */
+    uint64_t cmpLength;
+    /**Uncompressed length for the DDT */
+    uint64_t length;
+    /**CRC64-ECMA of the compressed DDT */
+    uint64_t cmpCrc64;
+    /**CRC64-ECMA of the uncompressed DDT */
+    uint64_t crc64;
+} DdtHeader2;
 
 ==== Field Descriptions