base64是广为使用的一种编码及解码方式， 通常用于网络传输和邮件传输中，使用base64可以将标点符号以及多字节文字等特殊字符编码以便传输，以下是base64 编码解码的objective－c代码， 可以用于desktop和iphone程序当中.
/* base64.h */
extern size_t EstimateBas64EncodedDataSize(size_t inDataSize);
extern size_t EstimateBas64DecodedDataSize(size_t inDataSize);
extern bool Base64EncodeData(const void *inInputData, size_t inInputDataSize, char *, size_t *ioOutputDataSize, BOOL wrapped);
extern bool Base64DecodeData(const void *inInputData, size_t , void *ioOutputData, size_t *ioOutputDataSize);
/* base64.m*/
#include "base64.h"
#include <math.h>
const UInt8 kBase64EncodeTable[64] = {
/* 0 */ 'A', /* 1 */ 'B', /* 2 */ 'C', /* 3 */ 'D',
/* 4 */ 'E', /* 5 */ 'F', /* 6 */ 'G', /* 7 */ 'H',
/* 8 */ 'I', /* 9 */ 'J', /* 10 */ 'K', /* 11 */ 'L',
/* 12 */ 'M', /* 13 */ 'N', /* 14 */ 'O', /* 15 */ 'P',
/* 16 */ 'Q', /* 17 */ 'R', /* 18 */ 'S', /* 19 */ 'T',
/* 20 */ 'U', /* 21 */ 'V', /* 22 */ 'W', /* 23 */ 'X',
/* 24 */ 'Y', /* 25 */ 'Z', /* 26 */ 'a', /* 27 */ 'b',
/* 28 */ 'c', /* 29 */ 'd', /* 30 */ 'e', /* 31 */ 'f',
/* 32 */ 'g', /* 33 */ 'h', /* 34 */ 'i', /* 35 */ 'j',
/* 36 */ 'k', /* 37 */ 'l', /* 38 */ 'm', /* 39 */ 'n',
/* 40 */ 'o', /* 41 */ 'p', /* 42 */ 'q', /* 43 */ 'r',
/* 44 */ 's', /* 45 */ 't', /* 46 */ 'u', /* 47 */ 'v',
/* 48 */ 'w', /* 49 */ 'x', /* 50 */ 'y', /* 51 */ 'z',
/* 52 */ '0', /* 53 */ '1', /* 54 */ '2', /* 55 */ '3',
/* 56 */ '4', /* 57 */ '5', /* 58 */ '6', /* 59 */ '7',
/* 60 */ '8', /* 61 */ '9', /* 62 */ '+', /* 63 */ '/'
};
/*
-1 = Base64 end of data marker.
-2 = White space (tabs, cr, lf, space)
-3 = Noise (all non whitespace, non-base64 characters)
-4 = Dangerous noise
-5 = Illegal noise (null byte)
*/
const SInt8 kBase64DecodeTable[128] = {
/* 0x00 */ -5, /* 0x01 */ -3, /* 0x02 */ -3, /* 0x03 */ -3,
/* 0x04 */ -3, /* 0x05 */ -3, /* 0x06 */ -3, /* 0x07 */ -3,
/* 0x08 */ -3, /* 0x09 */ -2, /* 0x0a */ -2, /* 0x0b */ -2,
/* 0x0c */ -2, /* 0x0d */ -2, /* 0x0e */ -3, /* 0x0f */ -3,
/* 0x10 */ -3, /* 0x11 */ -3, /* 0x12 */ -3, /* 0x13 */ -3,
/* 0x14 */ -3, /* 0x15 */ -3, /* 0x16 */ -3, /* 0x17 */ -3,
/* 0x18 */ -3, /* 0x19 */ -3, /* 0x1a */ -3, /* 0x1b */ -3,
/* 0x1c */ -3, /* 0x1d */ -3, /* 0x1e */ -3, /* 0x1f */ -3,
/* ' ' */ -2, /* '!' */ -3, /* '"' */ -3, /* '#' */ -3,
/* '$' */ -3, /* '%' */ -3, /* '&' */ -3, /* ''' */ -3,
/* '(' */ -3, /* ')' */ -3, /* '*' */ -3, /* '+' */ 62,
/* ',' */ -3, /* '-' */ -3, /* '.' */ -3, /* '/' */ 63,
/* '0' */ 52, /* '1' */ 53, /* '2' */ 54, /* '3' */ 55,
/* '4' */ 56, /* '5' */ 57, /* '6' */ 58, /* '7' */ 59,
/* '8' */ 60, /* '9' */ 61, /* ':' */ -3, /* ';' */ -3,
/* '<' */ -3, /* '=' */ -1, /* '>' */ -3, /* '?' */ -3,
/* '@' */ -3, /* 'A' */ 0, /* 'B' */ 1, /* 'C' */ 2,
/* 'D' */ 3, /* 'E' */ 4, /* 'F' */ 5, /* 'G' */ 6,
/* 'H' */ 7, /* 'I' */ 8, /* 'J' */ 9, /* 'K' */ 10,
/* 'L' */ 11, /* 'M' */ 12, /* 'N' */ 13, /* 'O' */ 14,
/* 'P' */ 15, /* 'Q' */ 16, /* 'R' */ 17, /* 'S' */ 18,
/* 'T' */ 19, /* 'U' */ 20, /* 'V' */ 21, /* 'W' */ 22,
/* 'X' */ 23, /* 'Y' */ 24, /* 'Z' */ 25, /* '[' */ -3,
/* '\' */ -3, /* ']' */ -3, /* '^' */ -3, /* '_' */ -3,
/* '`' */ -3, /* 'a' */ 26, /* 'b' */ 27, /* 'c' */ 28,
/* 'd' */ 29, /* 'e' */ 30, /* 'f' */ 31, /* 'g' */ 32,
/* 'h' */ 33, /* 'i' */ 34, /* 'j' */ 35, /* 'k' */ 36,
/* 'l' */ 37, /* 'm' */ 38, /* 'n' */ 39, /* 'o' */ 40,
/* 'p' */ 41, /* 'q' */ 42, /* 'r' */ 43, /* 's' */ 44,
/* 't' */ 45, /* 'u' */ 46, /* 'v' */ 47, /* 'w' */ 48,
/* 'x' */ 49, /* 'y' */ 50, /* 'z' */ 51, /* '{' */ -3,
/* '|' */ -3, /* '}' */ -3, /* '~' */ -3, /* 0x7f */ -3
};
const UInt8 kBits_00000011 = 0x03;
const UInt8 kBits_00001111 = 0x0F;
const UInt8 kBits_00110000 = 0x30;
const UInt8 kBits_00111100 = 0x3C;
const UInt8 kBits_00111111 = 0x3F;
const UInt8 kBits_11000000 = 0xC0;
const UInt8 kBits_11110000 = 0xF0;
const UInt8 kBits_11111100 = 0xFC;
size_t EstimateBas64EncodedDataSize(size_t inDataSize)
{
size_t theEncodedDataSize = (int)ceil(inDataSize / 3.0) * 4;
theEncodedDataSize = theEncodedDataSize / 72 * 74 + theEncodedDataSize % 72;
return(theEncodedDataSize);
}
size_t EstimateBas64DecodedDataSize(size_t inDataSize)
{
size_t theDecodedDataSize = (int)ceil(inDataSize / 4.0) * 3;
//theDecodedDataSize = theDecodedDataSize / 72 * 74 + theDecodedDataSize % 72;
return(theDecodedDataSize);
}
bool Base64EncodeData(const void *inInputData, size_t inInputDataSize, char *outOutputData, size_t *ioOutputDataSize, BOOL wrapped)
{
size_t theEncodedDataSize = EstimateBas64EncodedDataSize(inInputDataSize);
if (*ioOutputDataSize < theEncodedDataSize)
return(false);
*ioOutputDataSize = theEncodedDataSize;
const UInt8 *theInPtr = (const UInt8 *)inInputData;
UInt32 theInIndex = 0, theOutIndex = 0;
for (; theInIndex < (inInputDataSize / 3) * 3; theInIndex += 3)
{
outOutputData[theOutIndex++] = kBase64EncodeTable[(theInPtr[theInIndex] & kBits_11111100) >> 2];
outOutputData[theOutIndex++] = kBase64EncodeTable[(theInPtr[theInIndex] & kBits_00000011) << 4 | (theInPtr[theInIndex + 1] & kBits_11110000) >> 4];
outOutputData[theOutIndex++] = kBase64EncodeTable[(theInPtr[theInIndex + 1] & kBits_00001111) << 2 | (theInPtr[theInIndex + 2] & kBits_11000000) >> 6];
outOutputData[theOutIndex++] = kBase64EncodeTable[(theInPtr[theInIndex + 2] & kBits_00111111) >> 0];
if (wrapped && (theOutIndex % 74 == 72))
{
outOutputData[theOutIndex++] = '\r';
outOutputData[theOutIndex++] = '\n';
}
}
const size_t theRemainingBytes = inInputDataSize - theInIndex;
if (theRemainingBytes == 1)
{
outOutputData[theOutIndex++] = kBase64EncodeTable[(theInPtr[theInIndex] & kBits_11111100) >> 2];
outOutputData[theOutIndex++] = kBase64EncodeTable[(theInPtr[theInIndex] & kBits_00000011) << 4 | (0 & kBits_11110000) >> 4];
outOutputData[theOutIndex++] = '=';
outOutputData[theOutIndex++] = '=';
if (wrapped && (theOutIndex % 74 == 72))
{
outOutputData[theOutIndex++] = '\r';
outOutputData[theOutIndex++] = '\n';
}
}
else if (theRemainingBytes == 2)
{
outOutputData[theOutIndex++] = kBase64EncodeTable[(theInPtr[theInIndex] & kBits_11111100) >> 2];
outOutputData[theOutIndex++] = kBase64EncodeTable[(theInPtr[theInIndex] & kBits_00000011) << 4 | (theInPtr[theInIndex + 1] & kBits_11110000) >> 4];
outOutputData[theOutIndex++] = kBase64EncodeTable[(theInPtr[theInIndex + 1] & kBits_00001111) << 2 | (0 & kBits_11000000) >> 6];
outOutputData[theOutIndex++] = '=';
if (wrapped && (theOutIndex % 74 == 72))
{
outOutputData[theOutIndex++] = '\r';
outOutputData[theOutIndex++] = '\n';
}
}
return(true);
}
bool Base64DecodeData(const void *inInputData, size_t inInputDataSize, void *ioOutputData, size_t *ioOutputDataSize)
{
memset(ioOutputData, '.', *ioOutputDataSize);
size_t theDecodedDataSize = EstimateBas64DecodedDataSize(inInputDataSize);
if (*ioOutputDataSize < theDecodedDataSize)
return(false);
*ioOutputDataSize = 0;
const UInt8 *theInPtr = (const UInt8 *)inInputData;
UInt8 *theOutPtr = (UInt8 *)ioOutputData;
size_t theInIndex = 0, theOutIndex = 0;
UInt8 theOutputOctet;
size_t theSequence = 0;
for (; theInIndex < inInputDataSize; )
{
SInt8 theSextet = 0;
SInt8 theCurrentInputOctet = theInPtr[theInIndex];
theSextet = kBase64DecodeTable[theCurrentInputOctet];
if (theSextet == -1)
break;
while (theSextet == -2)
{
theCurrentInputOctet = theInPtr[++theInIndex];
theSextet = kBase64DecodeTable[theCurrentInputOctet];
}
while (theSextet == -3)
{
theCurrentInputOctet = theInPtr[++theInIndex];
theSextet = kBase64DecodeTable[theCurrentInputOctet];
}
if (theSequence == 0)
{
theOutputOctet = (theSextet >= 0 ? theSextet : 0) << 2 & kBits_11111100;
}
else if (theSequence == 1)
{
theOutputOctet |= (theSextet >- 0 ? theSextet : 0) >> 4 & kBits_00000011;
theOutPtr[theOutIndex++] = theOutputOctet;
}
else if (theSequence == 2)
{
theOutputOctet = (theSextet >= 0 ? theSextet : 0) << 4 & kBits_11110000;
}
else if (theSequence == 3)
{
theOutputOctet |= (theSextet >= 0 ? theSextet : 0) >> 2 & kBits_00001111;
theOutPtr[theOutIndex++] = theOutputOctet;
}
else if (theSequence == 4)
{
theOutputOctet = (theSextet >= 0 ? theSextet : 0) << 6 & kBits_11000000;
}
else if (theSequence == 5)
{
theOutputOctet |= (theSextet >= 0 ? theSextet : 0) >> 0 & kBits_00111111;
theOutPtr[theOutIndex++] = theOutputOctet;
}
theSequence = (theSequence + 1) % 6;
if (theSequence != 2 && theSequence != 4)
theInIndex++;
}
*ioOutputDataSize = theOutIndex;
return(true);
}