xrCore: crc32 made thread safe

Author: Im-dex

code/engine.vc2008/xrCore/crc32.cpp

@@ -1,51 +1,63 @@
 #include "stdafx.h"
 #pragma hdrstop
 
-static BOOL crc32_ready		= FALSE;
 static u32	crc32_table		[256];					// Lookup table array 
 
-inline u32		Reflect		(u32 ref, char ch)		// Reflects CRC bits in the lookup table 
+class Crc32Initializer final
 {
-	// Used only by Init_CRC32_Table(). 
-
-	u32 value(0); 
-
-	// Swap bit 0 for bit 7 
-	// bit 1 for bit 6, etc. 
-	for(int i = 1; i < (ch + 1); i++) 
-	{ 
-		if(ref & 1) 
-			value |= 1 << (ch - i); 
-		ref >>= 1; 
-	} 
-	return value; 
-} 
-
-void			crc32_init	() 
-{
-	// Call this function only once to initialize the CRC table. 
-
-	// This is the official polynomial used by CRC-32 
-	// in PKZip, WinZip and Ethernet. 
-	u32 ulPolynomial = 0x04c11db7; 
-
-	// 256 values representing ASCII character codes. 
-	for(int i = 0; i <= 0xFF; i++) 
-	{ 
-		crc32_table[i]=Reflect(i, 8) << 24; 
-		for (int j = 0; j < 8; j++) 
-			crc32_table[i] = (crc32_table[i] << 1) ^ (crc32_table[i] & (1 << 31) ? ulPolynomial : 0); 
-		crc32_table[i] = Reflect(crc32_table[i], 32); 
-	} 
-} 
+public:
+
+    static void init() noexcept
+    {
+        static Crc32Initializer initializer;
+    }
+
+private:
+
+    Crc32Initializer() noexcept
+    {
+        crc32_init();
+    }
+
+    static u32 reflect(u32 ref, char ch) noexcept		// Reflects CRC bits in the lookup table 
+    {
+        // Used only by Init_CRC32_Table(). 
+
+        u32 value(0);
+
+        // Swap bit 0 for bit 7 
+        // bit 1 for bit 6, etc. 
+        for (int i = 1; i < (ch + 1); i++)
+        {
+            if (ref & 1)
+                value |= 1 << (ch - i);
+            ref >>= 1;
+        }
+        return value;
+    }
+
+    static void crc32_init() noexcept
+    {
+        // Call this function only once to initialize the CRC table. 
+
+        // This is the official polynomial used by CRC-32 
+        // in PKZip, WinZip and Ethernet. 
+        u32 ulPolynomial = 0x04c11db7;
+
+        // 256 values representing ASCII character codes. 
+        for (int i = 0; i <= 0xFF; i++)
+        {
+            crc32_table[i] = reflect(i, 8) << 24;
+            for (int j = 0; j < 8; j++)
+                crc32_table[i] = (crc32_table[i] << 1) ^ (crc32_table[i] & (1 << 31) ? ulPolynomial : 0);
+            crc32_table[i] = reflect(crc32_table[i], 32);
+        }
+    }
+};
 
 u32				crc32		(const void* P, u32 len) 
 {
-	if (!crc32_ready)	
-	{
-		crc32_init	();
-		crc32_ready	= TRUE;
-	}
+    Crc32Initializer::init();
 
 	// Pass a text string to this function and it will return the CRC. 
 
@@ -71,11 +83,7 @@ u32				crc32		(const void* P, u32 len)
 
 u32				crc32		(const void* P, u32 len, u32 starting_crc) 
 {
-	if (!crc32_ready)	
-	{
-		crc32_init	();
-		crc32_ready	= TRUE;
-	}
+    Crc32Initializer::init();
 
 	u32		ulCRC		= 0xffffffff ^ starting_crc; 
 	u8*		buffer		= (u8*)P;
@@ -88,11 +96,7 @@ u32				crc32		(const void* P, u32 len, u32 starting_crc)
 
 u32				path_crc32	(const char* path, u32 len) 
 {
-	if (!crc32_ready)	
-	{
-		crc32_init	();
-		crc32_ready	= TRUE;
-	}
+    Crc32Initializer::init();
 
 	u32		ulCRC		= 0xffffffff;
 	u8*		buffer		= (u8*)path;