Added performance chart

Author: tbartelmess

Package.swift

@@ -20,7 +20,10 @@ let package = Package(
     targets: [
         .target(
             name: "CRC32C",
-            dependencies: ["CIntelCRC"]),
+            dependencies: ["CIntelCRC"],
+            swiftSettings: [
+            .define("USE_HARDWARE")
+        ]),
         .target(name: "CIntelCRC",
                 dependencies: [],
                 cSettings: [

README.md

@@ -20,6 +20,15 @@ crc.finalize()
 crc.value
 ```
 
+## Performance
+
+When using an Intel CPU with a SSE 4.2 instruction set, the specialized `CRC` instruction is used. On other CPUs the calculation falls back to a generic software implemenation.
+
+With SSE 4.2 you can expect a speedup of about 5x.
+
+Below is a chart with the average runtime to calcluate the CRC32-C of a 1GB file on an 8th Gen "Coffee Lake" Intel Core i9 with 2.9 GHz.
+
+![performance graph](performance.png)
 
 ## License
 

Sources/CIntelCRC/include/CIntelCRC.h

@@ -1,4 +1,3 @@
 #include <stdlib.h>
 #include <stdint.h>
-unsigned int intel_crc(unsigned int c, const unsigned char* data, size_t length);
-uint32_t crc32c_append_hw(uint32_t crc, const uint8_t * buf, size_t len);
+uint32_t intel_crc(uint32_t crc, const uint8_t * buf, size_t len);

Sources/CRC32C/CRC32C.swift

@@ -32,7 +32,7 @@ public struct CRC32C {
 
     mutating private func crc32IntelSSE42(_ data: [UInt8]) {
         value = data.withUnsafeBytes { (ptr) in
-            crc32c_append_hw(value, ptr.bindMemory(to: UInt8.self).baseAddress, data.count)
+            intel_crc(value, ptr.bindMemory(to: UInt8.self).baseAddress, data.count)
         }
     }