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87 lines
1.8 KiB
Plaintext
87 lines
1.8 KiB
Plaintext
=== Index Block (`INDX`) *_DEPRECATED_*
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The index block stores references to all blocks present in the file.
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It is composed of a header, followed by a sequence of entries, the count of which is defined within the header.
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Multiple index blocks may exist within a file to represent previous states or historical versions; however, only the final index block must be referenced by the main file header.
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*Deprecation Notice*: This block is deprecated and *MUST NOT* be used in new image files.
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==== Structure Definition
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[source,c]
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#define INDEX_MAGIC 0x58444E49
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/**Header for the index, followed by entries */
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typedef struct IndexHeader
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{
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/**Identifier, <see cref="BlockType.Index" /> */
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uint32_t identifier;
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/**How many entries follow this header */
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uint16_t entries;
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/**CRC64-ECMA of the index */
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uint64_t crc64;
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} IndexHeader;
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==== Field Descriptions
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[cols="2,2,2,6",options="header"]
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|===
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|Type
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|Size
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|Name
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|Description
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|uint32_t
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|4 bytes
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|identifier
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|The index block identifier, always `INDX`
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|uint16_t
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|2 bytes
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|entries
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|The number of entries following this header
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|uint64_t
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|8 bytes
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|crc64
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|CRC64-ECMA checksum of the entries following this header
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|===
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==== Index entries
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[source,c]
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/**Index entry */
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typedef struct IndexEntry
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{
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/**Type of item pointed by this entry */
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uint32_t blockType;
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/**Type of data contained by the block pointed by this entry */
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uint16_t dataType;
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/**Offset in file where item is stored */
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uint64_t offset;
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} IndexEntry;
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==== Field Descriptions
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[cols="2,2,2,6",options="header"]
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|===
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|Type
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|Size
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|Name
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|Description
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|uint32_t
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|4 bytes
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|blockType
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|The type of block this entry points to.
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|uint16_t
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|2 bytes
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|dataType
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|The type of data the block pointed by this entry contains.
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|uint64_t
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|8 bytes
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|offset
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|The offset in bytes from the start of the file where the block pointed by this entry starts.
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|=== |