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copied!<p>A method in a <code>NSData</code> category</p> <pre><code>- (NSString*)encodeBase64 { static char* alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="; unsigned int length = self.length; unsigned const char* rawData = self.bytes; //empty data = empty output if (length == 0) { return @""; } unsigned int outputLength = (((length + 2) / 3) * 4); //let's allocate buffer for the output char* rawOutput = malloc(outputLength + 1); //with each step we get 3 bytes from the input and write 4 bytes to the output for (unsigned int i = 0, outputIndex = 0; i < length; i += 3, outputIndex += 4) { BOOL triple = NO; BOOL quad = NO; //get 3 bytes (or only 1 or 2 when we have reached the end of input) unsigned int value = rawData[i]; value <<= 8; if (i + 1 < length) { value |= rawData[i + 1]; triple = YES; } value <<= 8; if (i + 2 < length) { value |= rawData[i + 2]; quad = YES; } //3 * 8 bits written as 4 * 6 bits (indexing the 64 chars of the alphabet) //write = if end of input reached rawOutput[outputIndex + 3] = (quad) ? alphabet[value & 0x3F] : '='; value >>= 6; rawOutput[outputIndex + 2] = (triple) ? alphabet[value & 0x3F] : '='; value >>= 6; rawOutput[outputIndex + 1] = alphabet[value & 0x3F]; value >>= 6; rawOutput[outputIndex] = alphabet[value & 0x3F]; } rawOutput[outputLength] = 0; NSString* output = [NSString stringWithCString:rawOutput encoding:NSASCIIStringEncoding]; free(rawOutput); return output; } </code></pre>

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