Hard coded the crc table into the crc32 object so it doesn't need to

spend time in its constructor computing it.

dlib/crc32/crc32_kernel_1.h

@@ -16,11 +16,9 @@ namespace dlib
         /*!
             INITIAL VALUE
                 checksum == 0xFFFFFFFF
-                table == crc table
 
             CONVENTION
                 get_checksum() == checksum ^ 0xFFFFFFFF
-                table == crc table
         !*/
 
     public:
@@ -70,12 +68,67 @@ namespace dlib
 
     private:
 
-        inline void fill_crc_table(
-        );
-
         unsigned long checksum;
-        unsigned long table[256];
 
+        inline unsigned long table (
+            unsigned int idx
+        ) const 
+        {
+            /*
+            // This code generates the crc_table used below.
+            unsigned long crc_table[256];
+            for (unsigned long i = 0; i < 256; ++i)
+            {
+                unsigned long temp = i;
+                for (unsigned long j = 0; j < 8; ++j)
+                {
+                    if (temp&1)
+                        temp = (temp>>1)^0xedb88320;
+                    else
+                        temp >>= 1;
+                }
+                crc_table[i] = temp;
+                std::cout << std::hex << crc_table[i] << std::endl;
+            }
+            */
+
+            const static unsigned long crc_table[256] = {
+                0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x76dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
+                0xedb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x9b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
+                0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
+                0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
+                0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
+                0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
+                0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
+                0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
+                0x76dc4190, 0x1db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x6b6b51f, 0x9fbfe4a5, 0xe8b8d433,
+                0x7807c9a2, 0xf00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x86d3d2d, 0x91646c97, 0xe6635c01,
+                0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
+                0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
+                0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
+                0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
+                0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
+                0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
+                0xedb88320, 0x9abfb3b6, 0x3b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x4db2615, 0x73dc1683,
+                0xe3630b12, 0x94643b84, 0xd6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0xa00ae27, 0x7d079eb1,
+                0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
+                0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
+                0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
+                0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
+                0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
+                0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
+                0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x26d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x5005713,
+                0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0xcb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0xbdbdf21,
+                0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
+                0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
+                0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
+                0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
+                0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
+                0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
+            };
+
+            return crc_table[idx];
+        }
 
     };    
 
@@ -88,29 +141,6 @@ namespace dlib
 // ----------------------------------------------------------------------------------------
     // member function definitions
 // ----------------------------------------------------------------------------------------
-// ----------------------------------------------------------------------------------------
-
-    void crc32::
-    fill_crc_table (
-    )
-    {
-        unsigned long temp;
-
-        // fill out the crc table
-        for (unsigned long i = 0; i < 256; ++i)
-        {
-            temp = i;
-            for (unsigned long j = 0; j < 8; ++j)
-            {
-                if (temp&1)
-                    temp = (temp>>1)^0xedb88320;
-                else
-                    temp >>= 1;
-            }
-            table[i] = temp;
-        }
-    }
-
 // ----------------------------------------------------------------------------------------
 
     crc32::
@@ -118,7 +148,6 @@ namespace dlib
     )
     {
         checksum = 0xFFFFFFFF;
-        fill_crc_table();
     }
 
 // ----------------------------------------------------------------------------------------
@@ -129,7 +158,6 @@ namespace dlib
     )
     {
         checksum = 0xFFFFFFFF;
-        fill_crc_table();
         add(item);
     }
 
@@ -141,7 +169,6 @@ namespace dlib
     )
     {
         checksum = 0xFFFFFFFF;
-        fill_crc_table();
         add(item);
     }
 
@@ -169,7 +196,7 @@ namespace dlib
         unsigned char item
     )
     {
-        checksum = (checksum>>8) ^ table[(checksum^item) & 0xFF];
+        checksum = (checksum>>8) ^ table((checksum^item) & 0xFF);
     }
 
 // ----------------------------------------------------------------------------------------
@@ -180,7 +207,7 @@ namespace dlib
     )
     {
         for (std::string::size_type i = 0; i < item.size(); ++i)
-            checksum = (checksum>>8) ^ table[(checksum^item[i]) & 0xFF];
+            checksum = (checksum>>8) ^ table((checksum^item[i]) & 0xFF);
     }
 
 // ----------------------------------------------------------------------------------------
@@ -191,7 +218,7 @@ namespace dlib
     )
     {
         for (unsigned long i = 0; i < item.size(); ++i)
-            checksum = (checksum>>8) ^ table[(checksum^item[i]) & 0xFF];
+            checksum = (checksum>>8) ^ table((checksum^item[i]) & 0xFF);
     }
 
 // ----------------------------------------------------------------------------------------