NSData와 NSString 의 Base64 Encoding / Decoding 메소드

- (NSData*)dataWithBase64EncodedString:(NSString *)string

{

static const char encodingTable[] ="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

if (string == nil) return [NSData data];

if ([string length] == 0)

return [NSData data];

static char *decodingTable = NULL;

if (decodingTable == NULL)

{

decodingTable = malloc(256);

if (decodingTable == NULL)

return nil;

memset(decodingTable, CHAR_MAX, 256);

NSUInteger i;

for (i = 0; i < 64; i++)

decodingTable[(short)encodingTable[i]] = i;

}

const char *characters = [string cStringUsingEncoding:NSASCIIStringEncoding];

if (characters == NULL)     //  Not an ASCII string!

return nil;

char *bytes = malloc((([string length] + 3) / 4) * 3);

if (bytes == NULL)

return nil;

NSUInteger length = 0;

    

NSUInteger i = 0;

while (YES)

{

char buffer[4];

short bufferLength;

for (bufferLength = 0; bufferLength < 4; i++)

{

if (characters[i] == '\0')

break;

if (isspace(characters[i]) || characters[i] == '=')

continue;

buffer[bufferLength] = decodingTable[(short)characters[i]];

if (buffer[bufferLength++] == CHAR_MAX)      //  Illegal character!

{

free(bytes);

return nil;

}

}

if (bufferLength == 0)

break;

if (bufferLength == 1)      //  At least two characters are needed to produce one byte!

{

free(bytes);

return nil;

}

//  Decode the characters in the buffer to bytes.

bytes[length++] = (buffer[0] << 2) | (buffer[1] >> 4);

if (bufferLength > 2)

bytes[length++] = (buffer[1] << 4) | (buffer[2] >> 2);

if (bufferLength > 3)

bytes[length++] = (buffer[2] << 6) | buffer[3];

}

realloc(bytes, length);

return [NSData dataWithBytesNoCopy:bytes length:length];

}

- (NSString*)base64forData:(NSData*)theData 

{

    const uint8_t* input = (const uint8_t*)[theData bytes]; 

    NSInteger length = [theData length]; 

    

    static char table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="; 

    

    NSMutableData* data = [NSMutableData dataWithLength:((length + 2) / 3) * 4]; 

    uint8_t* output = (uint8_t*)data.mutableBytes; 

    

    NSInteger i; 

    for (i=0; i < length; i += 3) { 

        NSInteger value = 0; 

        NSInteger j; 

        for (j = i; j < (i + 3); j++) { 

            value <<= 8; 

            

            if (j < length) { 

                value |= (0xFF & input[j]); 

            } 

        } 

        

        NSInteger theIndex = (i / 3) * 4; 

        output[theIndex + 0] =                    table[(value >> 18) & 0x3F]; 

        output[theIndex + 1] =                    table[(value >> 12) & 0x3F]; 

        output[theIndex + 2] = (i + 1) < length ? table[(value >> 6)  & 0x3F] : '='; 

        output[theIndex + 3] = (i + 2) < length ? table[(value >> 0)  & 0x3F] : '='; 

    } 

    

    return [[[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding] autorelease]; 

}