/* longLengthPos and longLengthID to allow us to represent either a single litLength or matchLength
* in the seqStore that has a value larger than U16 (if it exists). To do so, we increment
- * the existing value of the literal or match by 0x10000.
+ * the existing value of the litLength or matchLength by 0x10000.
*/
U32 longLengthID; /* 0 == no longLength; 1 == Represent the long literal; 2 == Represent the long match; */
U32 longLengthPos; /* Index of the sequence to apply long length modification to */
}
}
assert(repIdx >= -3);
- /* Use default repcodes if repcode references an offset that doesn't exist yet
- * This can only occur within the first two sequences.
- */
outSeqs[i].offset = repIdx >= 0 ? outSeqs[repIdx].offset : repStartValue[-repIdx - 1];
if (outSeqs[i].rep == 3 && outSeqs[i].litLength == 0) {
--outSeqs[i].offset;
}
/* Insert last literals (if any exist) in the block as a sequence with ml == off == 0 */
+ assert(seqStoreLiteralsSize >= literalsRead);
lastLLSize = seqStoreLiteralsSize - literalsRead;
if (lastLLSize > 0) {
outSeqs[i].litLength = lastLLSize;
typedef struct ZSTD_CCtx_params_s ZSTD_CCtx_params;
typedef struct {
- unsigned int offset; /* The offset of the match.
- * If offset == 0 and matchLength == 0,
- * then this sequence represents last literals in the block of litLength size.
+ unsigned int offset; /* The offset of the match. (NOT the same as the offset code)
+ * If offset == 0 and matchLength == 0, this sequence represents the last
+ * literals in the block of litLength size.
*/
unsigned int litLength; /* Literal length of the sequence. */
unsigned int matchLength; /* Match length of the sequence. */
/* Note: Users of this API may provide a sequence with matchLength == litLength == offset == 0.
- * In this case, we will treat the "sequence" as a marker for a block boundary.
+ * In this case, we will treat the sequence as a marker for a block boundary.
*/
- unsigned int rep; /* Represents which repeat offset is used. Ranges from [0, 3].
- * If rep == 0, then this sequence does not contain a repeat offset.
+ unsigned int rep; /* Represents which repeat offset is represented by the field 'offset'.
+ * Ranges from [0, 3].
+ *
+ * Repeat offsets are essentially previous offsets from previous sequences sorted in
+ * recency order. For more detail, see doc/zstd_compression_format.md
+ *
+ * If rep == 0, then 'offset' does not contain a repeat offset.
* If rep > 0:
* If litLength != 0:
* rep == 1 --> offset == repeat_offset_1
* rep == 1 --> offset == repeat_offset_2
* rep == 2 --> offset == repeat_offset_3
* rep == 3 --> offset == repeat_offset_1 - 1
+ *
+ * Note: This field is optional. ZSTD_getSequence() will calculate the value of
+ * 'rep', but repeat offsets do not necessarily need to be calculated from an external
+ * sequence provider's perspective.
*/
} ZSTD_Sequence;