base64.c

#include "base64.h"

//
//  NSData+Base64.m
//  base64
//
//  Created by Matt Gallagher on 2009/06/03.
//  Copyright 2009 Matt Gallagher. All rights reserved.
//
//  Permission is given to use this source code file, free of charge, in any
//  project, commercial or otherwise, entirely at your risk, with the condition
//  that any redistribution (in part or whole) of source code must retain
//  this copyright and permission notice. Attribution in compiled projects is
//  appreciated but not required.

//
// Mapping from 6 bit pattern to ASCII character.
//
static unsigned char base64EncodeLookup[65] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

//
// Definition for "masked-out" areas of the base64DecodeLookup mapping
//
#define xx 65

//
// Mapping from ASCII character to 6 bit pattern.
//
static unsigned char base64DecodeLookup[256] =
{
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 62, xx, xx, xx, 63, 
    52, 53, 54, 55, 56, 57, 58, 59, 60, 61, xx, xx, xx, xx, xx, xx, 
    xx,  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, xx, xx, xx, xx, xx, 
    xx, 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, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
};

//
// Fundamental sizes of the binary and base64 encode/decode units in bytes
//
#define BINARY_UNIT_SIZE 3
#define BASE64_UNIT_SIZE 4

//
// NewBase64Decode
//
// Decodes the base64 ASCII string in the inputBuffer to a newly malloced
// output buffer.
//
//  inputBuffer - the source ASCII string for the decode
//	length - the length of the string or -1 (to specify strlen should be used)
//	outputLength - if not-NULL, on output will contain the decoded length
//
// returns the decoded buffer. Must be free'd by caller. Length is given by
//	outputLength.
//
void *NewBase64Decode(
					  const char *inputBuffer,
					  size_t length,
					  size_t *outputLength)
{
	if ((int) length == -1)
	{
		length = strlen(inputBuffer);
	}
	
	size_t outputBufferSize =
	((length+BASE64_UNIT_SIZE-1) / BASE64_UNIT_SIZE) * BINARY_UNIT_SIZE;
	unsigned char *outputBuffer = (unsigned char *)malloc(outputBufferSize);
	
	size_t i = 0;
	size_t j = 0;
	while (i < length)
	{
		//
		// Accumulate 4 valid characters (ignore everything else)
		//
		unsigned char accumulated[BASE64_UNIT_SIZE];
		size_t accumulateIndex = 0;
		while (i < length)
		{
			unsigned char decode = base64DecodeLookup[(unsigned char)inputBuffer[i++]];
			if (decode != xx)
			{
				accumulated[accumulateIndex] = decode;
				accumulateIndex++;
				
				if (accumulateIndex == BASE64_UNIT_SIZE)
				{
					break;
				}
			}
		}
		
		//
		// Store the 6 bits from each of the 4 characters as 3 bytes
		//
		outputBuffer[j] = (accumulated[0] << 2) | (accumulated[1] >> 4);
		outputBuffer[j + 1] = (accumulated[1] << 4) | (accumulated[2] >> 2);
		outputBuffer[j + 2] = (accumulated[2] << 6) | accumulated[3];
		j += accumulateIndex - 1;
	}
	
	if (outputLength)
	{
		*outputLength = j;
	}
	return outputBuffer;
}

//
// NewBase64Decode
//
// Encodes the arbitrary data in the inputBuffer as base64 into a newly malloced
// output buffer.
//
//  inputBuffer - the source data for the encode
//	length - the length of the input in bytes
//  separateLines - if zero, no CR/LF characters will be added. Otherwise
//		a CR/LF pair will be added every 64 encoded chars.
//	outputLength - if not-NULL, on output will contain the encoded length
//		(not including terminating 0 char)
//
// returns the encoded buffer. Must be free'd by caller. Length is given by
//	outputLength.
//
char *NewBase64Encode(
					  const void *buffer,
					  size_t length,
					  int separateLines,
					  size_t *outputLength)
{
	const unsigned char *inputBuffer = (const unsigned char *)buffer;
	
#define MAX_NUM_PADDING_CHARS 2
#define OUTPUT_LINE_LENGTH 64
#define INPUT_LINE_LENGTH ((OUTPUT_LINE_LENGTH / BASE64_UNIT_SIZE) * BINARY_UNIT_SIZE)
#define CR_LF_SIZE 2
	
	//
	// Byte accurate calculation of final buffer size
	//
	size_t outputBufferSize =
	((length / BINARY_UNIT_SIZE)
	 + ((length % BINARY_UNIT_SIZE) ? 1 : 0))
	* BASE64_UNIT_SIZE;
	if (separateLines)
	{
		outputBufferSize +=
		(outputBufferSize / OUTPUT_LINE_LENGTH) * CR_LF_SIZE;
	}
	
	//
	// Include space for a terminating zero
	//
	outputBufferSize += 1;
	
	//
	// Allocate the output buffer
	//
	char *outputBuffer = (char *)malloc(outputBufferSize);
	if (!outputBuffer)
	{
		return NULL;
	}
	
	size_t i = 0;
	size_t j = 0;
	const size_t lineLength = separateLines ? INPUT_LINE_LENGTH : length;
	size_t lineEnd = lineLength;
	
	while (TRUE)
	{
		if (lineEnd > length)
		{
			lineEnd = length;
		}
		
		for (; i + BINARY_UNIT_SIZE - 1 < lineEnd; i += BINARY_UNIT_SIZE)
		{
			//
			// Inner loop: turn 48 bytes into 64 base64 characters
			//
			outputBuffer[j++] = base64EncodeLookup[(inputBuffer[i] & 0xFC) >> 2];
			outputBuffer[j++] = base64EncodeLookup[((inputBuffer[i] & 0x03) << 4)
												   | ((inputBuffer[i + 1] & 0xF0) >> 4)];
			outputBuffer[j++] = base64EncodeLookup[((inputBuffer[i + 1] & 0x0F) << 2)
												   | ((inputBuffer[i + 2] & 0xC0) >> 6)];
			outputBuffer[j++] = base64EncodeLookup[inputBuffer[i + 2] & 0x3F];
		}
		
		if (lineEnd == length)
		{
			break;
		}
		
		//
		// Add the newline
		//
		outputBuffer[j++] = '\r';
		outputBuffer[j++] = '\n';
		lineEnd += lineLength;
	}
	
	if (i + 1 < length)
	{
		//
		// Handle the single '=' case
		//
		outputBuffer[j++] = base64EncodeLookup[(inputBuffer[i] & 0xFC) >> 2];
		outputBuffer[j++] = base64EncodeLookup[((inputBuffer[i] & 0x03) << 4)
											   | ((inputBuffer[i + 1] & 0xF0) >> 4)];
		outputBuffer[j++] = base64EncodeLookup[(inputBuffer[i + 1] & 0x0F) << 2];
		outputBuffer[j++] =	'=';
	}
	else if (i < length)
	{
		//
		// Handle the double '=' case
		//
		outputBuffer[j++] = base64EncodeLookup[(inputBuffer[i] & 0xFC) >> 2];
		outputBuffer[j++] = base64EncodeLookup[(inputBuffer[i] & 0x03) << 4];
		outputBuffer[j++] = '=';
		outputBuffer[j++] = '=';
	}
	outputBuffer[j] = 0;
	
	//
	// Set the output length and return the buffer
	//
	if (outputLength)
	{
		*outputLength = j;
	}
	return outputBuffer;
}