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Diffstat (limited to 'base64.c')
| -rw-r--r-- | base64.c | 140 |
1 files changed, 140 insertions, 0 deletions
diff --git a/base64.c b/base64.c new file mode 100644 index 0000000..fcc7f5c --- /dev/null +++ b/base64.c @@ -0,0 +1,140 @@ +/* Part of publib. + + Copyright (c) 1994-2006 Lars Wirzenius. All rights reserved. + + Redistribution and use in source and binary forms, with or without + modification, are permitted provided that the following conditions + are met: + + 1. Redistributions of source code must retain the above copyright + notice, this list of conditions and the following disclaimer. + + 2. Redistributions in binary form must reproduce the above + copyright notice, this list of conditions and the following + disclaimer in the documentation and/or other materials provided + with the distribution. + + THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS + OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED + WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY + DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE + GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, + WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING + NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS + SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. +*/ +/* + * File: base64.c + * Purpose: Implementation of MIME's Base64 encoding and decoding. + * Author: Lars Wirzenius + * Version: $Id: base64.c,v 1.2 2003/11/15 18:24:10 liw Exp $ + */ + +#include <limits.h> +#include "base64.h" + +static const unsigned char sixtet_to_base64[] = + "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; + + +/* + * Function: base64_length + * Purpose: Compute minimum length of encoded output. + */ +size_t base64_length(size_t n) { + return 4*(n+3)/3 + 1; +} + + +/* + * Function: base64_encode + * Purpose: Convert octets to base64 + * Note: Output buffer must be at least base64_length(n) chars. + */ +size_t base64_encode(char *to, const char *from, size_t n) { + unsigned w; + char *to_start; + unsigned char *fromp; + + to_start = to; + + fromp = (unsigned char *) from; + for (; n >= 3; n -= 3, fromp += 3) { + w = (fromp[0] << 16) | (fromp[1] << 8) | fromp[2]; + *to++ = sixtet_to_base64[(w >> 18) & 0x3f]; + *to++ = sixtet_to_base64[(w >> 12) & 0x3f]; + *to++ = sixtet_to_base64[(w >> 6) & 0x3f]; + *to++ = sixtet_to_base64[w & 0x3f]; + } + + switch (n) { + case 0: + /* Nothing to do */ + break; + + case 1: + w = fromp[0]; + *to++ = sixtet_to_base64[(w >> 2) & 0x3f]; + *to++ = sixtet_to_base64[(w << 4) & 0x3f]; + *to++ = '='; + *to++ = '='; + break; + + case 2: + w = (fromp[0] << 8) | fromp[1]; + *to++ = sixtet_to_base64[(w >> 10) & 0x3f]; + *to++ = sixtet_to_base64[(w >> 4) & 0x3f]; + *to++ = sixtet_to_base64[(w << 2) & 0x3f]; + *to++ = '='; + break; + } + + return to - to_start; +} + + +/* + * Function: base64_decode + * Purpose: Convert base64 to octets. + * Note: Output buffer must be at least 3*n/4 chars. + * The output buffer does not get a '\0' appended. + */ +size_t base64_decode(char *to, const char *from, size_t len) { + static int base64_to_sixtet[UCHAR_MAX + 2]; + static int tab_init = 0; + int i; + unsigned bitbuf; + int nbits; + unsigned char *fromp; + char *to_start; + + if (!tab_init) { + tab_init = 1; + for (i = 0; i <= UCHAR_MAX + 1; ++i) + base64_to_sixtet[i] = -1; + for (i = 0; sixtet_to_base64[i] != '\0'; ++i) + base64_to_sixtet[sixtet_to_base64[i]] = i; + } + + to_start = to; + + bitbuf = 0; + nbits = 0; + fromp = (unsigned char *) from; + for (i = 0; i < len && fromp[i] != '='; ++i) { + if (base64_to_sixtet[fromp[i]] != -1) { + bitbuf = (bitbuf << 6) | base64_to_sixtet[fromp[i]]; + nbits += 6; + if (nbits >= 8) { + *to++ = (bitbuf >> (nbits - 8)) & 0xff; + bitbuf >>= 8; + nbits -= 8; + } + } + } + + return to - to_start; +} |