Diff: b64.cpp

Revision:

13:e76920d5e1ec

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/b64.cpp	Fri Apr 11 09:33:45 2014 +0000
@@ -0,0 +1,70 @@
+// Simple Base64 code
+// (c) Copyright 2010 MCQN Ltd.
+// Released under Apache License, version 2.0
+
+#include "b64.h"
+
+/* Simple test program
+#include <stdio.h>
+void main()
+{
+    char* in = "amcewen";
+    char out[22];
+
+    b64_encode(in, 15, out, 22);
+    out[21] = '\0';
+
+    printf(out);
+}
+*/
+
+int b64_encode(const unsigned char* aInput, int aInputLen, unsigned char* aOutput, int aOutputLen)
+{
+    // Work out if we've got enough space to encode the input
+    // Every 6 bits of input becomes a byte of output
+    if (aOutputLen < (aInputLen*8)/6)
+    {
+        // FIXME Should we return an error here, or just the length
+        return (aInputLen*8)/6;
+    }
+
+    // If we get here we've got enough space to do the encoding
+
+    const char* b64_dictionary = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+    if (aInputLen == 3)
+    {
+        aOutput[0] = b64_dictionary[aInput[0] >> 2];
+        aOutput[1] = b64_dictionary[(aInput[0] & 0x3)<<4|(aInput[1]>>4)];
+        aOutput[2] = b64_dictionary[(aInput[1]&0x0F)<<2|(aInput[2]>>6)];
+        aOutput[3] = b64_dictionary[aInput[2]&0x3F];
+    }
+    else if (aInputLen == 2)
+    {
+        aOutput[0] = b64_dictionary[aInput[0] >> 2];
+        aOutput[1] = b64_dictionary[(aInput[0] & 0x3)<<4|(aInput[1]>>4)];
+        aOutput[2] = b64_dictionary[(aInput[1]&0x0F)<<2];
+        aOutput[3] = '=';
+    }
+    else if (aInputLen == 1)
+    {
+        aOutput[0] = b64_dictionary[aInput[0] >> 2];
+        aOutput[1] = b64_dictionary[(aInput[0] & 0x3)<<4];
+        aOutput[2] = '=';
+        aOutput[3] = '=';
+    }
+    else
+    {
+        // Break the input into 3-byte chunks and process each of them
+        int i;
+        for (i = 0; i < aInputLen/3; i++)
+        {
+            b64_encode(&aInput[i*3], 3, &aOutput[i*4], 4);
+        }
+        if (aInputLen % 3 > 0)
+        {
+            // It doesn't fit neatly into a 3-byte chunk, so process what's left
+            b64_encode(&aInput[i*3], aInputLen % 3, &aOutput[i*4], aOutputLen - (i*4));
+        }
+    }
+}
+