base64的c语言源代码

#include <stdio.h> #include <stdlib.h> #include <string.h> #include "base64.h" static char base64_chars[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; int base64_encode(const void *data, int size, char **str) { char *s, *p; int i; int c; const unsigned char *q; p = s = (char *) malloc(size * 4 / 3 + 4); if (p == NULL) return -1; q = (const unsigned char *) data; i = 0; for (i = 0; i < size;) { c = q[i++]; c *= 256; if (i < size) c += q[i]; i++; c *= 256; if (i < size) c += q[i]; i++; p[0] = base64_chars[(c & 0x00fc0000) >> 18]; p[1] = base64_chars[(c & 0x0003f000) >> 12]; p[2] = base64_chars[(c & 0x00000fc0) >> 6]; p[3] = base64_chars[(c & 0x0000003f) >> 0]; if (i > size) p[3] = '='; if (i > size + 1) p[2] = '='; p += 4; } *p = 0; *str = s; return strlen(s); } static int pos(char c) { char *p; for (p = base64_chars; *p; p++) if (*p == c) return p - base64_chars; return -1; } #define DECODE_ERROR 0xffffffff static unsigned int token_decode(const char *token) { int i; unsigned int val = 0; int marker = 0; if (strlen(token) < 4) return DECODE_ERROR; for (i = 0; i < 4; i++) { val *= 64; if (token[i] == '=') marker++; else if (marker > 0) return DECODE_ERROR; else val += pos(token[i]); } if (marker > 2) return DECODE_ERROR; return (marker << 24) | val; } int base64_decode(const char *str, void *data) { const char *p; unsigned char *q; q = (unsigned char *)data; for (p = str; *p && (*p == '=' || strchr(base64_chars, *p)); p += 4) { unsigned int val = token_decode(p); unsigned int marker = (val >> 24) & 0xff; if (val == DECODE_ERROR) return -1; *q++ = (val >> 16) & 0xff; if (marker < 2) *q++ = (val >> 8) & 0xff; if (marker < 1) *q++ = val & 0xff; } return q - (unsigned char *) data; }