Changes in uspace/srv/net/checksum.c [aadf01e:a64c64d] in mainline

File:

• uspace/srv/net/checksum.c (modified) (3 diffs)

uspace/srv/net/checksum.c

@@ -47 +47 @@
 #define CRC_DIVIDER_LE  0xEDB88320
 
-uint32_t compute_crc32_le(uint32_t seed, uint8_t * data, size_t length){
-        size_t index;
+uint16_t compact_checksum(uint32_t sum){
+        // shorten to the 16 bits
+        while(sum >> 16){
+                sum = (sum &0xFFFF) + (sum >> 16);
+        }
 
-        while(length >= 8){
-                seed ^= (*data);
-                for(index = 0; index < 8; ++ index){
-                        if(seed &1){
-                                seed = (seed >> 1) ^ ((uint32_t) CRC_DIVIDER_LE);
-                        }else{
-                                seed >>= 1;
-                        }
-                }
-                ++ data;
-                length -= 8;
-        }
-        if(length > 0){
-                seed ^= (*data) >> (8 - length);
-                for(index = 0; index < length; ++ index){
-                        if(seed &1){
-                                seed = (seed >> 1) ^ ((uint32_t) CRC_DIVIDER_LE);
-                        }else{
-                                seed >>= 1;
-                        }
-                }
-                length -= 8;
-        }
-        return seed;
-}
-
-uint32_t compute_crc32_be(uint32_t seed, uint8_t * data, size_t length){
-        size_t index;
-
-        while(length >= 8){
-                seed ^= (*data) << 24;
-                for(index = 0; index < 8; ++ index){
-                        if(seed &0x80000000){
-                                seed = (seed << 1) ^ ((uint32_t) CRC_DIVIDER_BE);
-                        }else{
-                                seed <<= 1;
-                        }
-                }
-                ++ data;
-                length -= 8;
-        }
-        if(length > 0){
-                seed ^= ((*data) &(0xFF << (8 - length))) << 24;
-                for(index = 0; index < length; ++ index){
-                        if(seed &0x80000000){
-                                seed = (seed << 1) ^ ((uint32_t) CRC_DIVIDER_BE);
-                        }else{
-                                seed <<= 1;
-                        }
-                }
-                length -= 8;
-        }
-        return seed;
+        return (uint16_t) sum;
 }
 
@@ -121 +72 @@
 }
 
-uint16_t compact_checksum(uint32_t sum){
-        // shorten to the 16 bits
-        while(sum >> 16){
-                sum = (sum &0xFFFF) + (sum >> 16);
+uint32_t compute_crc32_be(uint32_t seed, uint8_t * data, size_t length){
+        size_t index;
+
+        // process full bytes
+        while(length >= 8){
+                // add the data
+                seed ^= (*data) << 24;
+                // for each added bit
+                for(index = 0; index < 8; ++ index){
+                        // if the first bit is set
+                        if(seed &0x80000000){
+                                // shift and divide the checksum
+                                seed = (seed << 1) ^ ((uint32_t) CRC_DIVIDER_BE);
+                        }else{
+                                // shift otherwise
+                                seed <<= 1;
+                        }
+                }
+                // move to the next byte
+                ++ data;
+                length -= 8;
         }
 
-        return (uint16_t) sum;
+        // process the odd bits
+        if(length > 0){
+                // add the data with zero padding
+                seed ^= ((*data) &(0xFF << (8 - length))) << 24;
+                // for each added bit
+                for(index = 0; index < length; ++ index){
+                        // if the first bit is set
+                        if(seed &0x80000000){
+                                // shift and divide the checksum
+                                seed = (seed << 1) ^ ((uint32_t) CRC_DIVIDER_BE);
+                        }else{
+                                // shift otherwise
+                                seed <<= 1;
+                        }
+                }
+        }
+
+        return seed;
+}
+
+uint32_t compute_crc32_le(uint32_t seed, uint8_t * data, size_t length){
+        size_t index;
+
+        // process full bytes
+        while(length >= 8){
+                // add the data
+                seed ^= (*data);
+                // for each added bit
+                for(index = 0; index < 8; ++ index){
+                        // if the last bit is set
+                        if(seed &1){
+                                // shift and divide the checksum
+                                seed = (seed >> 1) ^ ((uint32_t) CRC_DIVIDER_LE);
+                        }else{
+                                // shift otherwise
+                                seed >>= 1;
+                        }
+                }
+                // move to the next byte
+                ++ data;
+                length -= 8;
+        }
+
+        // process the odd bits
+        if(length > 0){
+                // add the data with zero padding
+                seed ^= (*data) >> (8 - length);
+                for(index = 0; index < length; ++ index){
+                        // if the last bit is set
+                        if(seed &1){
+                                // shift and divide the checksum
+                                seed = (seed >> 1) ^ ((uint32_t) CRC_DIVIDER_LE);
+                        }else{
+                                // shift otherwise
+                                seed >>= 1;
+                        }
+                }
+        }
+
+        return seed;
 }
 
@@ -137 +164 @@
 
 uint16_t ip_checksum(uint8_t * data, size_t length){
+        // compute, compact and flip the data checksum
         return flip_checksum(compact_checksum(compute_checksum(0, data, length)));
 }