From 47286536db70f48f09d9080d6b946dad5647e5ff Mon Sep 17 00:00:00 2001
From: Ivan G <aloneguid@outlook.com>
Date: Thu, 3 Aug 2023 13:05:42 +0100
Subject: [PATCH] Fixing LZ4 compression levels (#19)

---
 native/api.cpp  | 43 ++++++++++++++++++++++++++++---------------
 native/api.h    |  8 +++++++-
 native/test.cpp |  8 ++++----
 3 files changed, 39 insertions(+), 20 deletions(-)

diff --git a/native/api.cpp b/native/api.cpp
index 1eef63b..f5bfa85 100644
--- a/native/api.cpp
+++ b/native/api.cpp
@@ -13,6 +13,20 @@ using namespace std;
 
 bool lzo_initialised{ false };
 
+// taken from https://github.com/lz4/lz4/blob/839edadd09bd653b7e9237a2fbf405d9e8bfc14e/lib/lz4.c#L48C1-L58C35
+/*
+ * LZ4_ACCELERATION_DEFAULT :
+ * Select "acceleration" for LZ4_compress_fast() when parameter value <= 0
+ */
+#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
+
+
 bool compress_snappy(
    bool compress,
    char* input_buffer,
@@ -52,7 +66,7 @@ bool compress_zstd(
     int input_buffer_size,
     char* output_buffer,
     int* output_buffer_size,
-	int compression_level) {
+	compression_level compression_level) {
     if(output_buffer == nullptr) {
         if(compress) {
             *output_buffer_size = ZSTD_compressBound(input_buffer_size);
@@ -64,9 +78,9 @@ bool compress_zstd(
 
     if(compress) {
 		auto level = ZSTD_btultra2;
-		if(compression_level == 1){
+		if(compression_level == compression_level::fastest){
 			level = ZSTD_fast;
-		} else if(compression_level == 2){
+		} else if(compression_level == compression_level::balanced){
 			level = ZSTD_btopt;
 		}
 		
@@ -84,7 +98,7 @@ bool compress_brotli(
     int input_buffer_size,
     char* output_buffer,
     int* output_buffer_size,
-	int compression_level) {
+	compression_level compression_level) {
 
     if(output_buffer == nullptr) {
 
@@ -98,9 +112,9 @@ bool compress_brotli(
 
     if(compress) {
 		auto level = BROTLI_MAX_QUALITY;
-		if(compression_level == 1){
+		if(compression_level == compression_level::fastest){
 			level = BROTLI_MIN_QUALITY;
-		} else if(compression_level == 2){
+		} else if(compression_level == compression_level::balanced){
 			level = BROTLI_MAX_QUALITY/2;
 		}
         size_t compressed_size = *output_buffer_size;
@@ -197,7 +211,7 @@ bool compress_lz4(
     int input_buffer_size,
     char* output_buffer,
     int* output_buffer_size,
-	int compression_level) {
+    compression_level compression_level) {
     if(output_buffer == nullptr) {
         if(compress) {
             *output_buffer_size = LZ4_compressBound(input_buffer_size);
@@ -209,14 +223,13 @@ bool compress_lz4(
     }
 
     if(compress) {
-		auto level = 65537;
-		if(compression_level == 1){
-			level = 1;
-		} else if(compression_level == 2){
-			level = 32768;
-		}
+        int acceleration = LZ4_ACCELERATION_DEFAULT;
+        if(compression_level == compression_level::fastest)
+            acceleration = LZ4_ACCELERATION_MAX;
+        else if(compression_level == compression_level::balanced)
+            acceleration = LZ4_ACCELERATION_MAX / 2;
 
-        *output_buffer_size = LZ4_compress_fast(input_buffer, output_buffer, input_buffer_size, *output_buffer_size, level);
+        *output_buffer_size = LZ4_compress_fast(input_buffer, output_buffer, input_buffer_size, *output_buffer_size, acceleration);
         return *output_buffer_size != 0;
     } else {
         *output_buffer_size = LZ4_decompress_safe(input_buffer, output_buffer, input_buffer_size, *output_buffer_size);
@@ -227,7 +240,7 @@ bool compress_lz4(
 }
 
 bool compress(bool compress, int32_t codec, char* input_buffer, int32_t input_buffer_size,
-    char* output_buffer, int32_t* output_buffer_size, int32_t compression_level) {
+    char* output_buffer, int32_t* output_buffer_size, compression_level compression_level) {
     switch(codec) {
         case 1:
             return compress_snappy(compress, input_buffer, input_buffer_size, output_buffer, output_buffer_size);
diff --git a/native/api.h b/native/api.h
index 1ad0d81..24b508e 100644
--- a/native/api.h
+++ b/native/api.h
@@ -12,6 +12,12 @@
 # define EXPORTED
 #endif
 
+enum class compression_level : int32_t {
+    fastest = 1,
+    balanced = 2,
+    best = 3
+};
+
 extern "C"
 {
    /**
@@ -32,7 +38,7 @@ extern "C"
       int32_t input_buffer_size,
       char* output_buffer,
       int32_t* output_buffer_size,
-      int32_t compression_level);
+      compression_level compression_level);
 
    /**
     * @brief Used to just ping the library to test it's available at all
diff --git a/native/test.cpp b/native/test.cpp
index d8fba2a..c8141f4 100644
--- a/native/test.cpp
+++ b/native/test.cpp
@@ -5,19 +5,19 @@ using namespace std;
 
 bool run(int method, char* buffer, size_t buffer_length) {
     int32_t len{0};
-    bool ok = compress(true, method, buffer, buffer_length, nullptr, &len, 2);
+    bool ok = compress(true, method, buffer, buffer_length, nullptr, &len, compression_level::best);
 
     vector<char> compressed;
     compressed.resize(len);
 
     ok = compress(true, method, buffer, buffer_length,
-        &compressed[0], &len, 2);
+        &compressed[0], &len, compression_level::best);
 
     vector<byte> decompressed;
     int32_t bl1 = buffer_length;
     decompressed.resize(buffer_length);
     ok = compress(false, method, &compressed[0], len,
-       (char*)&decompressed[0], &bl1, 2);
+       (char*)&decompressed[0], &bl1, compression_level::best);
 
     return ok;
 }
@@ -27,7 +27,7 @@ int main() {
 
     //run(1, bytes, 3);
     //run(2, bytes, 3);
-    run(4, bytes, 3);
+    run(6, bytes, 3);
 
     return 0;
 }
\ No newline at end of file