added base64 encode decode

common.c

@@ -1,5 +1,18 @@
 #include "common.h"
 
+static const char base64_table[65] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+static const uint8_t base64_index[256] = { 
+  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
+  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
+  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 62, 63, 62, 62, 63,
+ 52, 53, 54, 55, 56, 57, 58, 59, 60, 61,  0,  0,  0,  0,  0,  0,
+  0,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 
+  15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 0,  0,  0,  0, 63,
+  0, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
+  41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 };
+
+
 void ecdaa_rand(void *buffer, size_t buflen) {
     getrandom(buffer, buflen, 0);
 }
@@ -35,3 +48,48 @@ void ecdaa_bintohex(const uint8_t *in_bin, char *out_hex, size_t inlen) {
     }
 }
 
+void ecdaa_encode(const uint8_t *in_dec, char *out_enc, size_t inlen) {
+    int outlen = 4 * ((inlen + 2) / 3);
+    int i = 0;
+    int j = 0;
+
+    while(i < inlen) {
+        uint32_t octet_a = i < inlen ? in_dec[i++] : 0;
+        uint32_t octet_b = i < inlen ? in_dec[i++] : 0;
+        uint32_t octet_c = i < inlen ? in_dec[i++] : 0;
+
+        uint32_t triple = (octet_a << 16) + (octet_b << 8) + octet_c;
+
+        out_enc[j++] = base64_table[(triple >> 18) & 0x3F];
+        out_enc[j++] = base64_table[(triple >> 12) & 0x3F];
+        out_enc[j++] = base64_table[(triple >> 6) & 0x3F];
+        out_enc[j++] = base64_table[(triple) & 0x3F];
+    }
+    switch (inlen % 3) {
+    case 1:
+        out_enc[j-2] = '=';
+    case 2:    
+        out_enc[j-1] = '=';
+    default:
+        break;
+    }
+}
+
+void ecdaa_decode(const uint8_t *in_enc, char *out_dec, size_t outlen) {
+    int inlen = 4 * ((outlen + 2) / 3); 
+    int i = 0;
+    int j = 0;
+    
+    while (i < inlen) {
+        uint32_t sextet_a = in_enc[i] == '=' ? 0 & i++ : base64_index[in_enc[i++]];
+        uint32_t sextet_b = in_enc[i] == '=' ? 0 & i++ : base64_index[in_enc[i++]];
+        uint32_t sextet_c = in_enc[i] == '=' ? 0 & i++ : base64_index[in_enc[i++]];
+        uint32_t sextet_d = in_enc[i] == '=' ? 0 & i++ : base64_index[in_enc[i++]];
+
+        uint32_t triple = (sextet_a << 18) + (sextet_b << 12) + (sextet_c << 6) + sextet_d;
+
+        if (j < outlen) out_dec[j++] = (triple >> 16) & 0xFF;
+        if (j < outlen) out_dec[j++] = (triple >> 8) & 0xFF;
+        if (j < outlen) out_dec[j++] = triple & 0xFF;
+    }
+}