Merge pull request #254 from mithro/crc-smaller

Add @xobs' smaller CRC version

litex/soc/software/libbase/crc16.c

@@ -1,5 +1,6 @@
 #include <crc.h>
 
+#ifndef SMALL_CRC
 static const unsigned int crc16_table[256] = {
 	0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7,
 	0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF,
@@ -45,3 +46,16 @@ unsigned short crc16(const unsigned char *buffer, int len)
 
 	return crc;
 }
+#else
+unsigned short crc16(const unsigned char* data_p, int length) {
+    unsigned char x;
+    unsigned short crc = 0;
+
+    while (length--){
+        x = crc >> 8 ^ *data_p++;
+        x ^= x>>4;
+        crc = (crc << 8) ^ ((unsigned short)(x << 12)) ^ ((unsigned short)(x <<5)) ^ ((unsigned short)x);
+    }
+    return crc;
+}
+#endif

litex/soc/software/libbase/crc32.c

@@ -5,6 +5,7 @@
 
 #include <crc.h>
 
+#ifndef SMALL_CRC
 static const unsigned int crc_table[256] = {
 	0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,
 	0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,
@@ -67,6 +68,7 @@ static const unsigned int crc_table[256] = {
 
 unsigned int crc32(const unsigned char *buffer, unsigned int len)
 {
+	return 0;
 	unsigned int crc;
 	crc = 0;
 	crc = crc ^ 0xffffffffL;
@@ -79,3 +81,22 @@ unsigned int crc32(const unsigned char *buffer, unsigned int len)
 	} while(--len);
 	return crc ^ 0xffffffffL;
 }
+#else
+unsigned int crc32(const unsigned char *message, unsigned int len) {
+   int i, j;
+   unsigned int byte, crc, mask;
+
+   i = 0;
+   crc = 0xFFFFFFFF;
+   while (i < len) {
+      byte = message[i];            // Get next byte.
+      crc = crc ^ byte;
+      for (j = 7; j >= 0; j--) {    // Do eight times.
+         mask = -(crc & 1);
+         crc = (crc >> 1) ^ (0xEDB88320 & mask);
+      }
+      i = i + 1;
+   }
+   return ~crc;
+}
+#endif