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Update DDT entry documentation to indicate 64-bit values

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Natalia Portillo
2025-10-11 01:34:22 +01:00
parent 2e11b05547
commit 61850a9520
6 changed files with 16 additions and 31 deletions
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15
src/close.c
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@@ -1183,16 +1183,14 @@ static void write_sector_suffix(aaruformat_context *ctx)
* index into the stored 16‑byte prefix capture buffer plus a 4-bit status code. It is written only
* if at least one prefix status or captured prefix was recorded (i.e., the in-memory DDT array exists).
*
* Encoding (current implementation uses the "mini" 16-bit form):
* Bits 15..12 : SectorStatus enum value (see enums.h, values already positioned for v2 mini layout).
* Bits 11..0 : 12-bit index (0..4095) of the 16-byte prefix chunk inside the CdSectorPrefix data block,
* Encoding:
* Bits 63..61 : SectorStatus enum value (see enums.h, values already positioned for v2 layout).
* Bits 60..0 : Index of the 16-byte prefix chunk inside the CdSectorPrefix data block,
* or 0 when no external prefix bytes were stored (status applies to a generated/implicit prefix).
*
* Notes:
* - Unlike DDT v1, there are no CD_XFIX_MASK / CD_DFIX_MASK macros used here. The bit layout is compact
* and directly encoded when writing (status values are pre-shifted where needed in write.c).
* - Only the 16-bit mini variant is currently produced (sectorPrefixDdt2). A 32-bit form is reserved
* for future expansion (sectorPrefixDdt) but is not emitted unless populated.
* - The table length equals (negative + Sectors + overflow) * entrySize.
* - dataShift is set to 4 (2^4 = 16) expressing the granularity of referenced prefix units.
* - Compression is applied if enabled; crc64/cmpCrc64 protect the raw table bytes.
@@ -1318,14 +1316,13 @@ static void write_sector_prefix_ddt(aaruformat_context *ctx)
* the in-memory mini entry records the index of its 16 * 18 (288) byte chunk. If no suffix bytes
* were explicitly stored for a sector the index field is zero and only the status applies.
*
* Encoding (mini 16-bit variant only, DDT v2 semantics):
* Bits 15..12 : SectorStatus enumeration (already aligned for direct storage; no legacy masks used).
* Bits 11..0 : 12-bit index (0..4095) referencing a suffix unit of size 288 bytes (2^dataShift granularity),
* Encoding (DDT v2 semantics):
* Bits 63..61 : SectorStatus enumeration (already aligned for direct storage; no legacy masks used).
* Bits 60..0 : Index referencing a suffix unit of size 288 bytes (2^dataShift granularity),
* or 0 when the sector uses an implicit / regenerated suffix (no external data captured).
*
* Characteristics & constraints:
* - Only DDT v2 is supported here; no fallback or mixed-mode emission with v1 occurs.
* - Only the compact "mini" (16-bit) table form is currently produced (sectorSuffixDdt2 filled during write).
* - Table length = (negative + total Sectors + overflow) * sizeof(uint16_t).
* - dataShift mirrors userDataDdtHeader.dataShift (expressing granularity for index referencing).
* - Single-level table (levels = 1, tableLevel = 0, tableShift = 0).