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    copied!<p>This is a good use case for Objective C <a href="http://en.wikipedia.org/wiki/Objective-C#Categories" rel="noreferrer">categories</a>.</p> <p>For Base64 encoding:</p> <pre><code>#import &lt;Foundation/NSString.h&gt; @interface NSString (NSStringAdditions) + (NSString *) base64StringFromData:(NSData *)data length:(int)length; @end ------------------------------------------- #import "NSStringAdditions.h" static char base64EncodingTable[64] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/' }; @implementation NSString (NSStringAdditions) + (NSString *) base64StringFromData: (NSData *)data length: (int)length { unsigned long ixtext, lentext; long ctremaining; unsigned char input[3], output[4]; short i, charsonline = 0, ctcopy; const unsigned char *raw; NSMutableString *result; lentext = [data length]; if (lentext &lt; 1) return @""; result = [NSMutableString stringWithCapacity: lentext]; raw = [data bytes]; ixtext = 0; while (true) { ctremaining = lentext - ixtext; if (ctremaining &lt;= 0) break; for (i = 0; i &lt; 3; i++) { unsigned long ix = ixtext + i; if (ix &lt; lentext) input[i] = raw[ix]; else input[i] = 0; } output[0] = (input[0] &amp; 0xFC) &gt;&gt; 2; output[1] = ((input[0] &amp; 0x03) &lt;&lt; 4) | ((input[1] &amp; 0xF0) &gt;&gt; 4); output[2] = ((input[1] &amp; 0x0F) &lt;&lt; 2) | ((input[2] &amp; 0xC0) &gt;&gt; 6); output[3] = input[2] &amp; 0x3F; ctcopy = 4; switch (ctremaining) { case 1: ctcopy = 2; break; case 2: ctcopy = 3; break; } for (i = 0; i &lt; ctcopy; i++) [result appendString: [NSString stringWithFormat: @"%c", base64EncodingTable[output[i]]]]; for (i = ctcopy; i &lt; 4; i++) [result appendString: @"="]; ixtext += 3; charsonline += 4; if ((length &gt; 0) &amp;&amp; (charsonline &gt;= length)) charsonline = 0; } return result; } @end </code></pre> <p>For Base64 decoding:</p> <pre><code>#import &lt;Foundation/Foundation.h&gt; @class NSString; @interface NSData (NSDataAdditions) + (NSData *) base64DataFromString:(NSString *)string; @end ------------------------------------------- #import "NSDataAdditions.h" @implementation NSData (NSDataAdditions) + (NSData *)base64DataFromString: (NSString *)string { unsigned long ixtext, lentext; unsigned char ch, inbuf[4], outbuf[3]; short i, ixinbuf; Boolean flignore, flendtext = false; const unsigned char *tempcstring; NSMutableData *theData; if (string == nil) { return [NSData data]; } ixtext = 0; tempcstring = (const unsigned char *)[string UTF8String]; lentext = [string length]; theData = [NSMutableData dataWithCapacity: lentext]; ixinbuf = 0; while (true) { if (ixtext &gt;= lentext) { break; } ch = tempcstring [ixtext++]; flignore = false; if ((ch &gt;= 'A') &amp;&amp; (ch &lt;= 'Z')) { ch = ch - 'A'; } else if ((ch &gt;= 'a') &amp;&amp; (ch &lt;= 'z')) { ch = ch - 'a' + 26; } else if ((ch &gt;= '0') &amp;&amp; (ch &lt;= '9')) { ch = ch - '0' + 52; } else if (ch == '+') { ch = 62; } else if (ch == '=') { flendtext = true; } else if (ch == '/') { ch = 63; } else { flignore = true; } if (!flignore) { short ctcharsinbuf = 3; Boolean flbreak = false; if (flendtext) { if (ixinbuf == 0) { break; } if ((ixinbuf == 1) || (ixinbuf == 2)) { ctcharsinbuf = 1; } else { ctcharsinbuf = 2; } ixinbuf = 3; flbreak = true; } inbuf [ixinbuf++] = ch; if (ixinbuf == 4) { ixinbuf = 0; outbuf[0] = (inbuf[0] &lt;&lt; 2) | ((inbuf[1] &amp; 0x30) &gt;&gt; 4); outbuf[1] = ((inbuf[1] &amp; 0x0F) &lt;&lt; 4) | ((inbuf[2] &amp; 0x3C) &gt;&gt; 2); outbuf[2] = ((inbuf[2] &amp; 0x03) &lt;&lt; 6) | (inbuf[3] &amp; 0x3F); for (i = 0; i &lt; ctcharsinbuf; i++) { [theData appendBytes: &amp;outbuf[i] length: 1]; } } if (flbreak) { break; } } } return theData; } @end </code></pre>
 

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