From 5797d570180013f62f75dbab23300d5de295a8a6 Mon Sep 17 00:00:00 2001
From: Yann Collet <cyan@fb.com>
Date: Fri, 29 Jul 2022 23:21:40 +0200
Subject: extend disabling checksum validation to normal lz4 CLI decompression

note : it's unlikely to improve speed, as in most cases I/O is slower than lz4 decompression,
but maybe in extreme scenarios, it might show a difference.
---
 programs/lz4io.c | 29 +++++++++++++++++++++++++----
 tests/Makefile   |  2 +-
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/programs/lz4io.c b/programs/lz4io.c
index 5644775..8b70b91 100644
--- a/programs/lz4io.c
+++ b/programs/lz4io.c
@@ -1072,13 +1072,22 @@ LZ4IO_decompressLZ4F(dRess_t ress,
     unsigned long long filesize = 0;
     LZ4F_errorCode_t nextToLoad;
     unsigned storedSkips = 0;
+    LZ4F_decompressOptions_t const dOpt_skipCrc = { 0, 1, 0, 0 };
+    const LZ4F_decompressOptions_t* const dOptPtr =
+        ((prefs->blockChecksum==0) && (prefs->streamChecksum==0)) ?
+        &dOpt_skipCrc : NULL;
 
     /* Init feed with magic number (already consumed from FILE* sFile) */
     {   size_t inSize = MAGICNUMBER_SIZE;
         size_t outSize= 0;
         LZ4IO_writeLE32(ress.srcBuffer, LZ4IO_MAGICNUMBER);
-        nextToLoad = LZ4F_decompress_usingDict(ress.dCtx, ress.dstBuffer, &outSize, ress.srcBuffer, &inSize, ress.dictBuffer, ress.dictBufferSize, NULL);
-        if (LZ4F_isError(nextToLoad)) END_PROCESS(62, "Header error : %s", LZ4F_getErrorName(nextToLoad));
+        nextToLoad = LZ4F_decompress_usingDict(ress.dCtx,
+                            ress.dstBuffer, &outSize,
+                            ress.srcBuffer, &inSize,
+                            ress.dictBuffer, ress.dictBufferSize,
+                            dOptPtr);  /* set it once, it's enough */
+        if (LZ4F_isError(nextToLoad))
+            END_PROCESS(62, "Header error : %s", LZ4F_getErrorName(nextToLoad));
     }
 
     /* Main Loop */
@@ -1096,8 +1105,13 @@ LZ4IO_decompressLZ4F(dRess_t ress,
             /* Decode Input (at least partially) */
             size_t remaining = readSize - pos;
             decodedBytes = ress.dstBufferSize;
-            nextToLoad = LZ4F_decompress_usingDict(ress.dCtx, ress.dstBuffer, &decodedBytes, (char*)(ress.srcBuffer)+pos, &remaining, ress.dictBuffer, ress.dictBufferSize, NULL);
-            if (LZ4F_isError(nextToLoad)) END_PROCESS(66, "Decompression error : %s", LZ4F_getErrorName(nextToLoad));
+            nextToLoad = LZ4F_decompress_usingDict(ress.dCtx,
+                                    ress.dstBuffer, &decodedBytes,
+                                    (char*)(ress.srcBuffer)+pos, &remaining,
+                                    ress.dictBuffer, ress.dictBufferSize,
+                                    NULL);
+            if (LZ4F_isError(nextToLoad))
+                END_PROCESS(66, "Decompression error : %s", LZ4F_getErrorName(nextToLoad));
             pos += remaining;
 
             /* Write Block */
@@ -1327,6 +1341,10 @@ LZ4IO_decompressDstFile(dRess_t ress,
 }
 
 
+/* Note : LZ4IO_decompressFilename()
+ * can provide total decompression time for the specified fileName.
+ * This information is not available with LZ4IO_decompressMultipleFilenames().
+ */
 int LZ4IO_decompressFilename(const char* input_filename, const char* output_filename, const LZ4IO_prefs_t* prefs)
 {
     dRess_t const ress = LZ4IO_createDResources(prefs);
@@ -1357,6 +1375,9 @@ int LZ4IO_decompressMultipleFilenames(
     dRess_t ress = LZ4IO_createDResources(prefs);
 
     if (outFileName==NULL) END_PROCESS(70, "Memory allocation error");
+    if (prefs->blockChecksum==0 && prefs->streamChecksum==0) {
+        DISPLAYLEVEL(4, "disabling checksum validation during decoding \n");
+    }
     ress.dstFile = LZ4IO_openDstFile(stdoutmark, prefs);
 
     for (i=0; i<ifntSize; i++) {
diff --git a/tests/Makefile b/tests/Makefile
index d266ae5..4b6ea48 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -380,7 +380,7 @@ test-lz4-basic: lz4 datagen unlz4 lz4cat
 	$(DATAGEN) -g6M -P99 | $(LZ4) -9BD   | $(LZ4) -t
 	$(DATAGEN) -g17M     | $(LZ4) -9v    | $(LZ4) -qt
 	$(DATAGEN) -g33M     | $(LZ4) --no-frame-crc | $(LZ4) -t
-	$(DATAGEN) -g256MB   | $(LZ4) -vqB4D | $(LZ4) -t
+	$(DATAGEN) -g256MB   | $(LZ4) -vqB4D | $(LZ4) -t --no-crc
 	@echo "hello world" > $(FPREFIX)-hw
 	$(LZ4) --rm -f $(FPREFIX)-hw $(FPREFIX)-hw.lz4
 	test ! -f $(FPREFIX)-hw                      # must fail (--rm)
-- 
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