string base64_encode(string data); 这个在php当中的具体算法是怎么实现的？

appreciatewo 2009-03-03 10:07:21

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grass_12 2009-03-09

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/*
+----------------------------------------------------------------------+
| PHP Version 5 |
+----------------------------------------------------------------------+
| Copyright (c) 1997-2008 The PHP Group |
+----------------------------------------------------------------------+
| This source file is subject to version 3.01 of the PHP license, |
| that is bundled with this package in the file LICENSE, and is |
| available through the world-wide-web at the following url: |
| http://www.php.net/license/3_01.txt |
| If you did not receive a copy of the PHP license and are unable to |
| obtain it through the world-wide-web, please send a note to |
| license@php.net so we can mail you a copy immediately. |
+----------------------------------------------------------------------+
| Author: Jim Winstead <jimw@php.net> |
+----------------------------------------------------------------------+
*/
/* $Id: base64.c,v 1.43.2.2.2.4 2007/12/31 07:20:12 sebastian Exp $ */

#include <string.h>

#include "php.h"
#include "base64.h"

/* {{{ */
static const char base64_table[] =
{ 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/', '\0'
};

static const char base64_pad = '=';

static const short base64_reverse_table[256] = {
-2, -2, -2, -2, -2, -2, -2, -2, -2, -1, -1, -2, -2, -1, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-1, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, 62, -2, -2, -2, 63,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -2, -2, -2, -2, -2, -2,
-2, 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, -2, -2, -2, -2, -2,
-2, 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, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2
};
/* }}} */

/* {{{ php_base64_encode */
PHPAPI unsigned char *php_base64_encode(const unsigned char *str, int length, int *ret_length)
{
const unsigned char *current = str;
unsigned char *p;
unsigned char *result;

if ((length + 2) < 0 || ((length + 2) / 3) >= (1 << (sizeof(int) * 8 - 2))) {
if (ret_length != NULL) {
*ret_length = 0;
}
return NULL;
}

result = (unsigned char *)safe_emalloc(((length + 2) / 3) * 4, sizeof(char), 1);
p = result;

while (length > 2) { /* keep going until we have less than 24 bits */
*p++ = base64_table[current[0] >> 2];
*p++ = base64_table[((current[0] & 0x03) << 4) + (current[1] >> 4)];
*p++ = base64_table[((current[1] & 0x0f) << 2) + (current[2] >> 6)];
*p++ = base64_table[current[2] & 0x3f];

current += 3;
length -= 3; /* we just handle 3 octets of data */
}

/* now deal with the tail end of things */
if (length != 0) {
*p++ = base64_table[current[0] >> 2];
if (length > 1) {
*p++ = base64_table[((current[0] & 0x03) << 4) + (current[1] >> 4)];
*p++ = base64_table[(current[1] & 0x0f) << 2];
*p++ = base64_pad;
} else {
*p++ = base64_table[(current[0] & 0x03) << 4];
*p++ = base64_pad;
*p++ = base64_pad;
}
}
if (ret_length != NULL) {
*ret_length = (int)(p - result);
}
*p = '\0';
return result;
}
/* }}} */

/* {{{ */
/* generate reverse table (do not set index 0 to 64)
static unsigned short base64_reverse_table[256];
#define rt base64_reverse_table
void php_base64_init(void)
{
char *s = emalloc(10240), *sp;
char *chp;
short idx;

for(ch = 0; ch < 256; ch++) {
chp = strchr(base64_table, ch);
if(ch && chp) {
idx = chp - base64_table;
if (idx >= 64) idx = -1;
rt[ch] = idx;
} else {
rt[ch] = -1;
}
}
sp = s;
sprintf(sp, "static const short base64_reverse_table[256] = {\n");
for(ch =0; ch < 256;) {
sp = s+strlen(s);
sprintf(sp, "\t% 3d,% 3d,% 3d,% 3d,% 3d,% 3d,% 3d,% 3d,% 3d,% 3d,% 3d,% 3d,% 3d,% 3d,% 3d,% 3d,\n", rt[ch+0], rt[ch+1], rt[ch+2], rt[ch+3], rt[ch+4], rt[ch+5], rt[ch+6], rt[ch+7], rt[ch+8], rt[ch+9], rt[ch+10], rt[ch+11], rt[ch+12], rt[ch+13], rt[ch+14], rt[ch+15]);
ch += 16;
}
sprintf(sp, "};");
php_error_docref(NULL TSRMLS_CC, E_NOTICE, "Reverse_table:\n%s", s);
efree(s);
}
*/
/* }}} */

PHPAPI unsigned char *php_base64_decode(const unsigned char *str, int length, int *ret_length)
{
return php_base64_decode_ex(str, length, ret_length, 0);
}

/* {{{ php_base64_decode */
/* as above, but backwards. :) */
PHPAPI unsigned char *php_base64_decode_ex(const unsigned char *str, int length, int *ret_length, zend_bool strict)
{
const unsigned char *current = str;
int ch, i = 0, j = 0, k;
/* this sucks for threaded environments */
unsigned char *result;

result = (unsigned char *)emalloc(length + 1);

/* run through the whole string, converting as we go */
while ((ch = *current++) != '\0' && length-- > 0) {
if (ch == base64_pad) break;

ch = base64_reverse_table[ch];
if ((!strict && ch < 0) || ch == -1) { /* a space or some other separator character, we simply skip over */
continue;
} else if (ch == -2) {
efree(result);
return NULL;
}

switch(i % 4) {
case 0:
result[j] = ch << 2;
break;
case 1:
result[j++] |= ch >> 4;
result[j] = (ch & 0x0f) << 4;
break;
case 2:
result[j++] |= ch >>2;
result[j] = (ch & 0x03) << 6;
break;
case 3:
result[j++] |= ch;
break;
}
i++;
}

k = j;
/* mop things up if we ended on a boundary */
if (ch == base64_pad) {
switch(i % 4) {
case 1:
efree(result);
return NULL;
case 2:
k++;
case 3:
result[k++] = 0;
}
}
if(ret_length) {
*ret_length = j;
}
result[j] = '\0';
return result;
}
/* }}} */

/* {{{ proto string base64_encode(string str)
Encodes string using MIME base64 algorithm */
PHP_FUNCTION(base64_encode)
{
char *str;
unsigned char *result;
int str_len, ret_length;

if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s", &str, &str_len) == FAILURE) {
return;
}
result = php_base64_encode(str, str_len, &ret_length);
if (result != NULL) {
RETVAL_STRINGL(result, ret_length, 0);
} else {
RETURN_FALSE;
}
}
/* }}} */

/* {{{ proto string base64_decode(string str[, bool strict])
Decodes string using MIME base64 algorithm */
PHP_FUNCTION(base64_decode)
{
char *str;
unsigned char *result;
zend_bool strict = 0;
int str_len, ret_length;

if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s|b", &str, &str_len, &strict) == FAILURE) {
return;
}
result = php_base64_decode_ex(str, str_len, &ret_length, strict);
if (result != NULL) {
RETVAL_STRINGL(result, ret_length, 0);
} else {
RETURN_FALSE;
}
}
/* }}} */

/*
* Local variables:
* tab-width: 4
* c-basic-offset: 4
* End:
* vim600: sw=4 ts=4 fdm=marker
* vim<600: sw=4 ts=4
*/