From: senhuang42 <senhuang96@fb.com>
Date: Tue, 27 Oct 2020 14:43:37 +0000 (-0400)
Subject: Improve documentation of seqStore_t
X-Git-Tag: v1.4.7~39^2~9
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9171f920cd790cc3f7b3ecc817efe88af7b063c7;p=thirdparty%2Fzstd.git

Improve documentation of seqStore_t
---

diff --git a/lib/common/zstd_internal.h b/lib/common/zstd_internal.h
index bfa98efaa..f9972766d 100644
--- a/lib/common/zstd_internal.h
+++ b/lib/common/zstd_internal.h
@@ -341,23 +341,28 @@ MEM_STATIC size_t ZSTD_limitCopy(void* dst, size_t dstCapacity, const void* src,
 *  Private declarations
 *********************************************/
 typedef struct seqDef_s {
-    U32 offset;
+    U32 offset;         /* Offset code of the sequence */
     U16 litLength;
     U16 matchLength;
 } seqDef;
 
 typedef struct {
     seqDef* sequencesStart;
-    seqDef* sequences;
+    seqDef* sequences;      /* ptr to end of sequences */
     BYTE* litStart;
-    BYTE* lit;
+    BYTE* lit;              /* ptr to end of literals */
     BYTE* llCode;
     BYTE* mlCode;
     BYTE* ofCode;
     size_t maxNbSeq;
     size_t maxNbLit;
-    U32   longLengthID;   /* 0 == no longLength; 1 == Lit.longLength; 2 == Match.longLength; */
-    U32   longLengthPos;
+
+    /* 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. 
+     */
+    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 */
 } seqStore_t;
 
 typedef struct {
diff --git a/lib/compress/zstd_compress.c b/lib/compress/zstd_compress.c
index b3ada04f4..9d5f20a61 100644
--- a/lib/compress/zstd_compress.c
+++ b/lib/compress/zstd_compress.c
@@ -2455,10 +2455,6 @@ static void ZSTD_copyBlockSequences(ZSTD_CCtx* zc)
         outSeqs[i].litLength = seqStoreSeqs[i].litLength;
         outSeqs[i].matchLength = seqStoreSeqs[i].matchLength + MINMATCH;
 
-        /* matchLength and litLength are stored with U16. longLengthPos
-         * and longLengthID to allow us to represent a single litLength or matchLength
-         * in the seqStore that has a value larger than U16 (if it exists).
-         */
         if (i == seqStore->longLengthPos) {
             if (seqStore->longLengthID == 1) {
                 outSeqs[i].litLength += 0x10000;
diff --git a/lib/zstd.h b/lib/zstd.h
index 7668729a1..1c61bd001 100644
--- a/lib/zstd.h
+++ b/lib/zstd.h
@@ -1115,24 +1115,24 @@ typedef struct ZSTD_CCtx_params_s ZSTD_CCtx_params;
 
 typedef struct {
     unsigned int offset;      /* The offset of the match.
-                              * If == 0, then represents a block of literals, determined by litLength
-                              */
+                               * If == 0, then represents a block of literals, determined by litLength
+                               */
 
     unsigned int litLength;   /* Literal length */
     unsigned int matchLength; /* Match length. */
     
     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.
-                              * Otherwise:
-                              *  If litLength != 0:
-                              *      rep == 1 --> offset == repeat offset 1
-                              *      rep == 2 --> offset == repeat offset 2
-                              *      rep == 3 --> offset == repeat offset 3
-                              *  If litLength == 0:
-                              *      rep == 1 --> offset == repeat offset 2
-                              *      rep == 2 --> offset == repeat offset 3
-                              *      rep == 3 --> offset == repeat offset 1 - 1
-                              */
+                               * If rep == 0, then this sequence does not contain a repeat offset.
+                               * Otherwise:
+                               *  If litLength != 0:
+                               *      rep == 1 --> offset == repeat offset 1
+                               *      rep == 2 --> offset == repeat offset 2
+                               *      rep == 3 --> offset == repeat offset 3
+                               *  If litLength == 0:
+                               *      rep == 1 --> offset == repeat offset 2
+                               *      rep == 2 --> offset == repeat offset 3
+                               *      rep == 3 --> offset == repeat offset 1 - 1
+                               */
 } ZSTD_Sequence;
 
 typedef struct {