From 89f50deec7b37ff2c7c01cfa85ef487189ae7701 Mon Sep 17 00:00:00 2001
From: Yann Collet <cyan@fb.com>
Date: Fri, 28 Apr 2017 16:52:36 -0700
Subject: [PATCH] minor code refactoring

clearer tables
---
 lib/decompress/zstd_decompress.c | 252 ++++++++-----------------------
 1 file changed, 62 insertions(+), 190 deletions(-)

diff --git a/lib/decompress/zstd_decompress.c b/lib/decompress/zstd_decompress.c
index 7499b8ae..634e2152 100644
--- a/lib/decompress/zstd_decompress.c
+++ b/lib/decompress/zstd_decompress.c
@@ -177,30 +177,6 @@ void ZSTD_copyDCtx(ZSTD_DCtx* dstDCtx, const ZSTD_DCtx* srcDCtx)
     memcpy(dstDCtx, srcDCtx, sizeof(ZSTD_DCtx) - workSpaceSize);  /* no need to copy workspace */
 }
 
-#if 0
-/* deprecated */
-static void ZSTD_refDCtx(ZSTD_DCtx* dstDCtx, const ZSTD_DCtx* srcDCtx)
-{
-    ZSTD_decompressBegin(dstDCtx);  /* init */
-    if (srcDCtx) {   /* support refDCtx on NULL */
-        dstDCtx->dictEnd = srcDCtx->dictEnd;
-        dstDCtx->vBase = srcDCtx->vBase;
-        dstDCtx->base = srcDCtx->base;
-        dstDCtx->previousDstEnd = srcDCtx->previousDstEnd;
-        dstDCtx->dictID = srcDCtx->dictID;
-        dstDCtx->litEntropy = srcDCtx->litEntropy;
-        dstDCtx->fseEntropy = srcDCtx->fseEntropy;
-        dstDCtx->LLTptr = srcDCtx->entropy.LLTable;
-        dstDCtx->MLTptr = srcDCtx->entropy.MLTable;
-        dstDCtx->OFTptr = srcDCtx->entropy.OFTable;
-        dstDCtx->HUFptr = srcDCtx->entropy.hufTable;
-        dstDCtx->entropy.rep[0] = srcDCtx->entropy.rep[0];
-        dstDCtx->entropy.rep[1] = srcDCtx->entropy.rep[1];
-        dstDCtx->entropy.rep[2] = srcDCtx->entropy.rep[2];
-    }
-}
-#endif
-
 static void ZSTD_refDDict(ZSTD_DCtx* dstDCtx, const ZSTD_DDict* ddict);
 
 
@@ -431,7 +407,8 @@ typedef struct
 
 /*! ZSTD_getcBlockSize() :
 *   Provides the size of compressed block from block header `src` */
-size_t ZSTD_getcBlockSize(const void* src, size_t srcSize, blockProperties_t* bpPtr)
+size_t ZSTD_getcBlockSize(const void* src, size_t srcSize,
+                          blockProperties_t* bpPtr)
 {
     if (srcSize < ZSTD_blockHeaderSize) return ERROR(srcSize_wrong);
     {   U32 const cBlockHeader = MEM_readLE24(src);
@@ -446,7 +423,8 @@ size_t ZSTD_getcBlockSize(const void* src, size_t srcSize, blockProperties_t* bp
 }
 
 
-static size_t ZSTD_copyRawBlock(void* dst, size_t dstCapacity, const void* src, size_t srcSize)
+static size_t ZSTD_copyRawBlock(void* dst, size_t dstCapacity,
+                          const void* src, size_t srcSize)
 {
     if (srcSize > dstCapacity) return ERROR(dstSize_tooSmall);
     memcpy(dst, src, srcSize);
@@ -454,7 +432,9 @@ static size_t ZSTD_copyRawBlock(void* dst, size_t dstCapacity, const void* src,
 }
 
 
-static size_t ZSTD_setRleBlock(void* dst, size_t dstCapacity, const void* src, size_t srcSize, size_t regenSize)
+static size_t ZSTD_setRleBlock(void* dst, size_t dstCapacity,
+                         const void* src, size_t srcSize,
+                               size_t regenSize)
 {
     if (srcSize != 1) return ERROR(srcSize_wrong);
     if (regenSize > dstCapacity) return ERROR(dstSize_tooSmall);
@@ -595,176 +575,70 @@ typedef union {
     U32 alignedBy4;
 } FSE_decode_t4;
 
+/* Default FSE distribution table for Literal Lengths */
 static const FSE_decode_t4 LL_defaultDTable[(1<<LL_DEFAULTNORMLOG)+1] = {
     { { LL_DEFAULTNORMLOG, 1, 1 } }, /* header : tableLog, fastMode, fastMode */
-    { {  0,  0,  4 } },              /* 0 : base, symbol, bits */
-    { { 16,  0,  4 } },
-    { { 32,  1,  5 } },
-    { {  0,  3,  5 } },
-    { {  0,  4,  5 } },
-    { {  0,  6,  5 } },
-    { {  0,  7,  5 } },
-    { {  0,  9,  5 } },
-    { {  0, 10,  5 } },
-    { {  0, 12,  5 } },
-    { {  0, 14,  6 } },
-    { {  0, 16,  5 } },
-    { {  0, 18,  5 } },
-    { {  0, 19,  5 } },
-    { {  0, 21,  5 } },
-    { {  0, 22,  5 } },
-    { {  0, 24,  5 } },
-    { { 32, 25,  5 } },
-    { {  0, 26,  5 } },
-    { {  0, 27,  6 } },
-    { {  0, 29,  6 } },
-    { {  0, 31,  6 } },
-    { { 32,  0,  4 } },
-    { {  0,  1,  4 } },
-    { {  0,  2,  5 } },
-    { { 32,  4,  5 } },
-    { {  0,  5,  5 } },
-    { { 32,  7,  5 } },
-    { {  0,  8,  5 } },
-    { { 32, 10,  5 } },
-    { {  0, 11,  5 } },
-    { {  0, 13,  6 } },
-    { { 32, 16,  5 } },
-    { {  0, 17,  5 } },
-    { { 32, 19,  5 } },
-    { {  0, 20,  5 } },
-    { { 32, 22,  5 } },
-    { {  0, 23,  5 } },
-    { {  0, 25,  4 } },
-    { { 16, 25,  4 } },
-    { { 32, 26,  5 } },
-    { {  0, 28,  6 } },
-    { {  0, 30,  6 } },
-    { { 48,  0,  4 } },
-    { { 16,  1,  4 } },
-    { { 32,  2,  5 } },
-    { { 32,  3,  5 } },
-    { { 32,  5,  5 } },
-    { { 32,  6,  5 } },
-    { { 32,  8,  5 } },
-    { { 32,  9,  5 } },
-    { { 32, 11,  5 } },
-    { { 32, 12,  5 } },
-    { {  0, 15,  6 } },
-    { { 32, 17,  5 } },
-    { { 32, 18,  5 } },
-    { { 32, 20,  5 } },
-    { { 32, 21,  5 } },
-    { { 32, 23,  5 } },
-    { { 32, 24,  5 } },
-    { {  0, 35,  6 } },
-    { {  0, 34,  6 } },
-    { {  0, 33,  6 } },
-    { {  0, 32,  6 } },
+     /* base, symbol, bits */
+    { {  0,  0,  4 } }, { { 16,  0,  4 } }, { { 32,  1,  5 } }, { {  0,  3,  5 } },
+    { {  0,  4,  5 } }, { {  0,  6,  5 } }, { {  0,  7,  5 } }, { {  0,  9,  5 } },
+    { {  0, 10,  5 } }, { {  0, 12,  5 } }, { {  0, 14,  6 } }, { {  0, 16,  5 } },
+    { {  0, 18,  5 } }, { {  0, 19,  5 } }, { {  0, 21,  5 } }, { {  0, 22,  5 } },
+    { {  0, 24,  5 } }, { { 32, 25,  5 } }, { {  0, 26,  5 } }, { {  0, 27,  6 } },
+    { {  0, 29,  6 } }, { {  0, 31,  6 } }, { { 32,  0,  4 } }, { {  0,  1,  4 } },
+    { {  0,  2,  5 } }, { { 32,  4,  5 } }, { {  0,  5,  5 } }, { { 32,  7,  5 } },
+    { {  0,  8,  5 } }, { { 32, 10,  5 } }, { {  0, 11,  5 } }, { {  0, 13,  6 } },
+    { { 32, 16,  5 } }, { {  0, 17,  5 } }, { { 32, 19,  5 } }, { {  0, 20,  5 } },
+    { { 32, 22,  5 } }, { {  0, 23,  5 } }, { {  0, 25,  4 } }, { { 16, 25,  4 } },
+    { { 32, 26,  5 } }, { {  0, 28,  6 } }, { {  0, 30,  6 } }, { { 48,  0,  4 } },
+    { { 16,  1,  4 } }, { { 32,  2,  5 } }, { { 32,  3,  5 } }, { { 32,  5,  5 } },
+    { { 32,  6,  5 } }, { { 32,  8,  5 } }, { { 32,  9,  5 } }, { { 32, 11,  5 } },
+    { { 32, 12,  5 } }, { {  0, 15,  6 } }, { { 32, 17,  5 } }, { { 32, 18,  5 } },
+    { { 32, 20,  5 } }, { { 32, 21,  5 } }, { { 32, 23,  5 } }, { { 32, 24,  5 } },
+    { {  0, 35,  6 } }, { {  0, 34,  6 } }, { {  0, 33,  6 } }, { {  0, 32,  6 } },
 };   /* LL_defaultDTable */
 
+/* Default FSE distribution table for Match Lengths */
 static const FSE_decode_t4 ML_defaultDTable[(1<<ML_DEFAULTNORMLOG)+1] = {
     { { ML_DEFAULTNORMLOG, 1, 1 } }, /* header : tableLog, fastMode, fastMode */
-    { {  0,  0,  6 } },              /* 0 : base, symbol, bits */
-    { {  0,  1,  4 } },
-    { { 32,  2,  5 } },
-    { {  0,  3,  5 } },
-    { {  0,  5,  5 } },
-    { {  0,  6,  5 } },
-    { {  0,  8,  5 } },
-    { {  0, 10,  6 } },
-    { {  0, 13,  6 } },
-    { {  0, 16,  6 } },
-    { {  0, 19,  6 } },
-    { {  0, 22,  6 } },
-    { {  0, 25,  6 } },
-    { {  0, 28,  6 } },
-    { {  0, 31,  6 } },
-    { {  0, 33,  6 } },
-    { {  0, 35,  6 } },
-    { {  0, 37,  6 } },
-    { {  0, 39,  6 } },
-    { {  0, 41,  6 } },
-    { {  0, 43,  6 } },
-    { {  0, 45,  6 } },
-    { { 16,  1,  4 } },
-    { {  0,  2,  4 } },
-    { { 32,  3,  5 } },
-    { {  0,  4,  5 } },
-    { { 32,  6,  5 } },
-    { {  0,  7,  5 } },
-    { {  0,  9,  6 } },
-    { {  0, 12,  6 } },
-    { {  0, 15,  6 } },
-    { {  0, 18,  6 } },
-    { {  0, 21,  6 } },
-    { {  0, 24,  6 } },
-    { {  0, 27,  6 } },
-    { {  0, 30,  6 } },
-    { {  0, 32,  6 } },
-    { {  0, 34,  6 } },
-    { {  0, 36,  6 } },
-    { {  0, 38,  6 } },
-    { {  0, 40,  6 } },
-    { {  0, 42,  6 } },
-    { {  0, 44,  6 } },
-    { { 32,  1,  4 } },
-    { { 48,  1,  4 } },
-    { { 16,  2,  4 } },
-    { { 32,  4,  5 } },
-    { { 32,  5,  5 } },
-    { { 32,  7,  5 } },
-    { { 32,  8,  5 } },
-    { {  0, 11,  6 } },
-    { {  0, 14,  6 } },
-    { {  0, 17,  6 } },
-    { {  0, 20,  6 } },
-    { {  0, 23,  6 } },
-    { {  0, 26,  6 } },
-    { {  0, 29,  6 } },
-    { {  0, 52,  6 } },
-    { {  0, 51,  6 } },
-    { {  0, 50,  6 } },
-    { {  0, 49,  6 } },
-    { {  0, 48,  6 } },
-    { {  0, 47,  6 } },
-    { {  0, 46,  6 } },
+    /* base, symbol, bits */
+    { {  0,  0,  6 } }, { {  0,  1,  4 } }, { { 32,  2,  5 } }, { {  0,  3,  5 } },
+    { {  0,  5,  5 } }, { {  0,  6,  5 } }, { {  0,  8,  5 } }, { {  0, 10,  6 } },
+    { {  0, 13,  6 } }, { {  0, 16,  6 } }, { {  0, 19,  6 } }, { {  0, 22,  6 } },
+    { {  0, 25,  6 } }, { {  0, 28,  6 } }, { {  0, 31,  6 } }, { {  0, 33,  6 } },
+    { {  0, 35,  6 } }, { {  0, 37,  6 } }, { {  0, 39,  6 } }, { {  0, 41,  6 } },
+    { {  0, 43,  6 } }, { {  0, 45,  6 } }, { { 16,  1,  4 } }, { {  0,  2,  4 } },
+    { { 32,  3,  5 } }, { {  0,  4,  5 } }, { { 32,  6,  5 } }, { {  0,  7,  5 } },
+    { {  0,  9,  6 } }, { {  0, 12,  6 } }, { {  0, 15,  6 } }, { {  0, 18,  6 } },
+    { {  0, 21,  6 } }, { {  0, 24,  6 } }, { {  0, 27,  6 } }, { {  0, 30,  6 } },
+    { {  0, 32,  6 } }, { {  0, 34,  6 } }, { {  0, 36,  6 } }, { {  0, 38,  6 } },
+    { {  0, 40,  6 } }, { {  0, 42,  6 } }, { {  0, 44,  6 } }, { { 32,  1,  4 } },
+    { { 48,  1,  4 } }, { { 16,  2,  4 } }, { { 32,  4,  5 } }, { { 32,  5,  5 } },
+    { { 32,  7,  5 } }, { { 32,  8,  5 } }, { {  0, 11,  6 } }, { {  0, 14,  6 } },
+    { {  0, 17,  6 } }, { {  0, 20,  6 } }, { {  0, 23,  6 } }, { {  0, 26,  6 } },
+    { {  0, 29,  6 } }, { {  0, 52,  6 } }, { {  0, 51,  6 } }, { {  0, 50,  6 } },
+    { {  0, 49,  6 } }, { {  0, 48,  6 } }, { {  0, 47,  6 } }, { {  0, 46,  6 } },
 };   /* ML_defaultDTable */
 
+/* Default FSE distribution table for Offset Codes */
 static const FSE_decode_t4 OF_defaultDTable[(1<<OF_DEFAULTNORMLOG)+1] = {
     { { OF_DEFAULTNORMLOG, 1, 1 } }, /* header : tableLog, fastMode, fastMode */
-    { {  0,  0,  5 } },              /* 0 : base, symbol, bits */
-    { {  0,  6,  4 } },
-    { {  0,  9,  5 } },
-    { {  0, 15,  5 } },
-    { {  0, 21,  5 } },
-    { {  0,  3,  5 } },
-    { {  0,  7,  4 } },
-    { {  0, 12,  5 } },
-    { {  0, 18,  5 } },
-    { {  0, 23,  5 } },
-    { {  0,  5,  5 } },
-    { {  0,  8,  4 } },
-    { {  0, 14,  5 } },
-    { {  0, 20,  5 } },
-    { {  0,  2,  5 } },
-    { { 16,  7,  4 } },
-    { {  0, 11,  5 } },
-    { {  0, 17,  5 } },
-    { {  0, 22,  5 } },
-    { {  0,  4,  5 } },
-    { { 16,  8,  4 } },
-    { {  0, 13,  5 } },
-    { {  0, 19,  5 } },
-    { {  0,  1,  5 } },
-    { { 16,  6,  4 } },
-    { {  0, 10,  5 } },
-    { {  0, 16,  5 } },
-    { {  0, 28,  5 } },
-    { {  0, 27,  5 } },
-    { {  0, 26,  5 } },
-    { {  0, 25,  5 } },
-    { {  0, 24,  5 } },
+    /* base, symbol, bits */
+    { {  0,  0,  5 } }, { {  0,  6,  4 } },
+    { {  0,  9,  5 } }, { {  0, 15,  5 } },
+    { {  0, 21,  5 } }, { {  0,  3,  5 } },
+    { {  0,  7,  4 } }, { {  0, 12,  5 } },
+    { {  0, 18,  5 } }, { {  0, 23,  5 } },
+    { {  0,  5,  5 } }, { {  0,  8,  4 } },
+    { {  0, 14,  5 } }, { {  0, 20,  5 } },
+    { {  0,  2,  5 } }, { { 16,  7,  4 } },
+    { {  0, 11,  5 } }, { {  0, 17,  5 } },
+    { {  0, 22,  5 } }, { {  0,  4,  5 } },
+    { { 16,  8,  4 } }, { {  0, 13,  5 } },
+    { {  0, 19,  5 } }, { {  0,  1,  5 } },
+    { { 16,  6,  4 } }, { {  0, 10,  5 } },
+    { {  0, 16,  5 } }, { {  0, 28,  5 } },
+    { {  0, 27,  5 } }, { {  0, 26,  5 } },
+    { {  0, 25,  5 } }, { {  0, 24,  5 } },
 };   /* OF_defaultDTable */
 
 /*! ZSTD_buildSeqTable() :
@@ -927,8 +801,6 @@ size_t ZSTD_execSequenceLast7(BYTE* op,
 }
 
 
-
-
 static seq_t ZSTD_decodeSequence(seqState_t* seqState)
 {
     seq_t seq;
@@ -1031,7 +903,7 @@ size_t ZSTD_execSequence(BYTE* op,
 
     /* copy Match */
     if (sequence.offset > (size_t)(oLitEnd - base)) {
-        /* offset beyond prefix */
+        /* offset beyond prefix -> go into extDict */
         if (sequence.offset > (size_t)(oLitEnd - vBase)) return ERROR(corruption_detected);
         match = dictEnd + (match - base);
         if (match + sequence.matchLength <= dictEnd) {