From 7b1b078dfcedd169332b0583d34daa65b2c585db Mon Sep 17 00:00:00 2001
From: Yann Collet <cyan@fb.com>
Date: Mon, 10 Aug 2020 11:03:27 -0700
Subject: fix #876

by introducing a max limit acceleration value
---
 lib/lz4.c | 19 ++++++++++++++-----
 lib/lz4.h |  3 ++-
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/lib/lz4.c b/lib/lz4.c
index ae50d54..239a3f4 100644
--- a/lib/lz4.c
+++ b/lib/lz4.c
@@ -45,10 +45,16 @@
 #endif
 
 /*
- * ACCELERATION_DEFAULT :
+ * LZ4_ACCELERATION_DEFAULT :
  * Select "acceleration" for LZ4_compress_fast() when parameter value <= 0
  */
-#define ACCELERATION_DEFAULT 1
+#define LZ4_ACCELERATION_DEFAULT 1
+/*
+ * LZ4_ACCELERATION_MAX :
+ * Any "acceleration" value higher than this threshold
+ * get treated as LZ4_ACCELERATION_MAX instead (fix #876)
+ */
+#define LZ4_ACCELERATION_MAX 65537
 
 
 /*-************************************
@@ -1200,7 +1206,8 @@ int LZ4_compress_fast_extState(void* state, const char* source, char* dest, int
 {
     LZ4_stream_t_internal* const ctx = & LZ4_initStream(state, sizeof(LZ4_stream_t)) -> internal_donotuse;
     assert(ctx != NULL);
-    if (acceleration < 1) acceleration = ACCELERATION_DEFAULT;
+    if (acceleration < 1) acceleration = LZ4_ACCELERATION_DEFAULT;
+    if (acceleration > LZ4_ACCELERATION_MAX) acceleration = LZ4_ACCELERATION_MAX;
     if (maxOutputSize >= LZ4_compressBound(inputSize)) {
         if (inputSize < LZ4_64Klimit) {
             return LZ4_compress_generic(ctx, source, dest, inputSize, NULL, 0, notLimited, byU16, noDict, noDictIssue, acceleration);
@@ -1230,7 +1237,8 @@ int LZ4_compress_fast_extState(void* state, const char* source, char* dest, int
 int LZ4_compress_fast_extState_fastReset(void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration)
 {
     LZ4_stream_t_internal* ctx = &((LZ4_stream_t*)state)->internal_donotuse;
-    if (acceleration < 1) acceleration = ACCELERATION_DEFAULT;
+    if (acceleration < 1) acceleration = LZ4_ACCELERATION_DEFAULT;
+    if (acceleration > LZ4_ACCELERATION_MAX) acceleration = LZ4_ACCELERATION_MAX;
 
     if (dstCapacity >= LZ4_compressBound(srcSize)) {
         if (srcSize < LZ4_64Klimit) {
@@ -1514,7 +1522,8 @@ int LZ4_compress_fast_continue (LZ4_stream_t* LZ4_stream,
 
     if (streamPtr->dirty) { return 0; } /* Uninitialized structure detected */
     LZ4_renormDictT(streamPtr, inputSize);   /* avoid index overflow */
-    if (acceleration < 1) acceleration = ACCELERATION_DEFAULT;
+    if (acceleration < 1) acceleration = LZ4_ACCELERATION_DEFAULT;
+    if (acceleration > LZ4_ACCELERATION_MAX) acceleration = LZ4_ACCELERATION_MAX;
 
     /* invalidate tiny dictionaries */
     if ( (streamPtr->dictSize-1 < 4-1)   /* intentional underflow */
diff --git a/lib/lz4.h b/lib/lz4.h
index 32108e2..54ec3fb 100644
--- a/lib/lz4.h
+++ b/lib/lz4.h
@@ -186,7 +186,8 @@ LZ4LIB_API int LZ4_compressBound(int inputSize);
     The larger the acceleration value, the faster the algorithm, but also the lesser the compression.
     It's a trade-off. It can be fine tuned, with each successive value providing roughly +~3% to speed.
     An acceleration value of "1" is the same as regular LZ4_compress_default()
-    Values <= 0 will be replaced by ACCELERATION_DEFAULT (currently == 1, see lz4.c).
+    Values <= 0 will be replaced by LZ4_ACCELERATION_DEFAULT (currently == 1, see lz4.c).
+    Values > LZ4_ACCELERATION_MAX will be replaced by LZ4_ACCELERATION_MAX (currently == 65537, see lz4.c).
 */
 LZ4LIB_API int LZ4_compress_fast (const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);
 
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