base64代码
关于base64的一种算法的代码，有一句话不太明白，望高手解答：
#include "StdAfx.h"
#include "Base64.h"
char base64EncodeChars[65] ="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";//编码后的字符集
int base64DecodeChars[128]={-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, 62, -1, -1, -1, 63,
52, 53, 54, 55, 56, 57, 58, 59,
60, 61, -1, -1, -1, -1, -1, -1,
-1, 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, -1, -1, -1, -1, -1,
-1, 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, -1, -1, -1, -1, -1 };//对应ASICC字符的位置
char* base64encode(LPCTSTR str)
{ //加密
char Out[260]={0};
int i = 0, len = strlen(str);
char c1, c2, c3;
while (i < len)
{
c1 = str[i++] & 0xff;
if (i == len)
{
sprintf(Out,"%s%c",Out,base64EncodeChars[c1 >> 2]);
sprintf(Out,"%s%c",Out,base64EncodeChars[(c1 & 0x3) << 4]);
sprintf(Out,"%s==",Out);
break;
}
c2 = str[i++];
if (i == len)
{
sprintf(Out,"%s%c",Out,base64EncodeChars[c1 >> 2]);
sprintf(Out,"%s%c",Out,base64EncodeChars[((c1 & 0x3) << 4) | ((c2 & 0xF0) >> 4)]);
sprintf(Out,"%s%c",Out,base64EncodeChars[(c2 & 0xF) << 2]);
sprintf(Out,"%s==",Out);
break;
}
c3 = str[i++];
sprintf(Out,"%s%c",Out,base64EncodeChars[c1 >> 2]);
sprintf(Out,"%s%c",Out,base64EncodeChars[((c1 & 0x3) << 4) | ((c2 & 0xF0) >> 4)]);
sprintf(Out,"%s%c",Out,base64EncodeChars[((c2 & 0xF) << 2) | ((c3 & 0xC0) >> 6)]);
sprintf(Out,"%s%c",Out,base64EncodeChars[c3 & 0x3F]);
}
return &(*Out);
}
char* utf16to8(LPCTSTR str)
{
char Out[260] ={0};
int i, len;
char c;//char为16位Unicode字符,范围0~0xffff,
len = strlen(str);
for (i = 0; i < len; i++)
{//根据字符的不同范围分别转化
c = str[i];
if ((c >= 0x0001) && (c <= 0x007F))
{
sprintf(Out,"%s%c",Out,str[i]);
}
else if (c > 0x07FF)
{
sprintf(Out,"%s%c",Out,(0xE0 | ((c >> 12) & 0x0F)));
sprintf(Out,"%s%c",Out,(0xE0 | ((c >> 12) & 0x0F)));
sprintf(Out,"%s%c",Out,(0x80 | ((c >> 6) & 0x3F)));
sprintf(Out,"%s%c",Out,(0x80 | ((c >> 0) & 0x3F)));
}
else
{
sprintf(Out,"%s%c",Out,(0xC0 | ((c >> 6) & 0x1F)));
sprintf(Out,"%s%c",Out,(0x80 | ((c >> 0) & 0x3F)));
}
}
return &(*Out);
}
char* base64decode(LPCTSTR str)
{//解密
int c1, c2, c3, c4;
int i=0, len;
char Out[260]={0};
len = strlen(str);
while (i < len)
{
do
{
c1 = base64DecodeChars[str[i++] & 0xff];
} while (i < len && c1 == -1);
if (c1 == -1) break;
do
{
c2 = base64DecodeChars[str[i++] & 0xff];
} while (i < len && c2 == -1);
if (c2 == -1) break;
sprintf(Out,"%s%c",Out,((c1 << 2) | ((c2 & 0x30) >> 4)));
do
{
c3 = str[i++] & 0xff;
if (c3 == 61) return Out;
c3 = base64DecodeChars[c3];
} while (i < len && c3 == -1);
if (c3 == -1) break;
sprintf(Out,"%s%c",Out,((c2 & 0XF) << 4) | ((c3 & 0x3C) >> 2));
do
{
c4 = str[i++] & 0xff;
if (c4 == 61) return Out;
c4 = base64DecodeChars[c4];
} while (i < len && c4 == -1);
if (c4 == -1) break;
sprintf(Out,"%s%c",Out,((c3 & 0x03) << 6) | c4);
}
return &(*Out);
}
char* utf8to16(LPCTSTR str)
{
char Out[260]={0};
int i=0, len;
char c, char2, char3;
len = strlen(str);
while (i < len)
{
c = str[i++];
switch (c >> 4)
{
case 0:
case 1:
case 2:
case 3:
case 4:
case 5:
case 6:
case 7:
sprintf(Out,"%s%c",Out,str[i - 1]);
break;
case 12:
case 13: char2 = str[i++];
sprintf(Out,"%s%c",Out,(((c & 0x1F) << 6) | (char2 & 0x3F)));
break;
case 14: char2 = str[i++];
char3 = str[i++];
sprintf(Out,"%s%c",Out,(((c & 0x0F) << 12) | ((char2 & 0x3F) << 6) | ((char3 & 0x3F) << 0)));
break;
}
}
return &(*Out);
}
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define BASE64_VALUE_SZ 256
int base64_value[BASE64_VALUE_SZ];
const unsigned char alphabet[65] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
class Base64Utility {
public:
Base64Utility();
int base64_encode(char *src, int srclen, char *dst, int tail);
int base64_decode(char *src, int srclen, char *dst);
private:
void base_64_init(void);
};
Base64Utility::Base64Utility() {
base_64_init();
}
void Base64Utility::base_64_init(void) {
int i;
for (i = 0; i < BASE64_VALUE_SZ; i++) base64_value[i] = -1;
for (i = 0; i < 64; i++) base64_value[(int) alphabet[i]] = i;
base64_value['='] = 0;
}
int Base64Utility::base64_encode(char *src, int srclen, char *dst, int tail) {
int bits, char_count, len;
char *o_char, *lim, *o_lim;
unsigned char c;
if ( !src
[解决办法]
!dst) return 0;
len = srclen;
lim = src + len;
o_char = dst;
o_lim = dst + (len*4)/3 + 1;
char_count = 0;
bits = 0;
while ( (src < lim) && (o_char < o_lim)) {
c = *(src++);
bits += c;
char_count++;
if (char_count == 3) {
*(o_char++) = alphabet[bits >> 18];
*(o_char++) = alphabet[(bits >> 12) & 0x3f];
*(o_char++) = alphabet[(bits >> 6) & 0x3f];
*(o_char++) = alphabet[bits & 0x3f];
bits = 0;
char_count = 0;
} else {
bits <<= 8;
}
}
if (char_count != 0) {
bits <<= 16 - (8 * char_count);
*(o_char++) = alphabet[bits >> 18];
*(o_char++) = alphabet[(bits >> 12) & 0x3f];
if (char_count == 1) {
if (tail) {
*(o_char++) = '=';
*(o_char++) = '=';
}
} else {
*(o_char++) = alphabet[(bits >> 6) & 0x3f];
if (tail) {
*(o_char++) = '=';
}
}
}
*(o_char) = 0;
return strlen(dst);
}
int Base64Utility::base64_decode(char *src, int srclen, char *dst) {
int j;
unsigned int k;
int c, base_result_sz;
long val;
if (!src
[解决办法]
!dst) return 0;
base_result_sz = srclen;
val = c = 0;
for (j = 0; *src; src++) {
k = (int) *src % BASE64_VALUE_SZ;
if (base64_value[k] < 0) continue;
val <<= 6;
val += base64_value[k];
if (++c < 4) continue;
dst[j++] = (char) (val >> 16);
dst[j++] = (val >> 8) & 0xff;
dst[j++] = val & 0xff;
val = c = 0;
}
switch (c) {
case 2://xxxxxx xx0000
dst[j++] = (val >> 4) & 0xff;
break;
case 3://XXXXXX XXxxxx xxxx00
dst[j++] = (char) (val >> 10);
dst[j++] = (val >> 2) & 0xff;
break;
}
return j;
}
Base64Utility b64u;
#define MAXLENS 1024768
#define MAXLEND 1366360
char bufd[MAXLEND];
char bufs[MAXLENS];
FILE *fs,*fd;
int fsize;
int main(int argc,char *argv[]) {
if (argc<4) {
USE:
printf("%s <-e
[解决办法]
-E
[解决办法]
-d> srcfile desfile\n",argv[0]);
return 1;
}
if (stricmp(argv[1],"-e") && stricmp(argv[1],"-d")) goto USE;
if (0==stricmp(argv[1],"-e")) {
fs=fopen(argv[2],"rb");
if (NULL==fs) {
printf("Can not open file %s!\n",argv[2]);
return 2;
}
fsize=fread(bufs,1,MAXLENS,fs);
if (fsize<=0) {
fclose(fs);
printf("Can not read file %s!\n",argv[2]);
return 3;
}
if (MAXLENS==fsize) printf("Warning: Up to %d bytes.\n",MAXLENS);
fclose(fs);
b64u.base64_encode(bufs,fsize,bufd,('E'==argv[2][1]));
fd=fopen(argv[3],"w");
if (NULL==fd) {
printf("Can not create file %s!\n",argv[3]);
return 4;
}
fprintf(fd,"%s",bufd);
fclose(fd);
} else {//0==stricmp(argv[1],"-d")
fd=fopen(argv[2],"rb");
if (NULL==fd) {
printf("Can not open file %s!\n",argv[2]);
return 2;
}
fsize=fread(bufd,1,MAXLEND,fd);
if (fsize<=0) {
fclose(fd);
printf("Can not read file %s!\n",argv[2]);
return 3;
}
if (MAXLEND==fsize) printf("Warning: Up to %d bytes.\n",MAXLEND);
fclose(fd);
fsize=b64u.base64_decode(bufd,fsize,bufs);
fs=fopen(argv[3],"wb");
if (NULL==fs) {
printf("Can not create file %s!\n",argv[3]);
return 4;
}
if (fsize!=(int)fwrite(bufs,1,fsize,fs)) {
printf("Write %s error!\n",argv[3]);
fclose(fs);
return 5;
}
fclose(fs);
}
return 0;
}
