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* Copyright (c) 1995 - 1999 Kungliga Tekniska Högskolan
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* (Royal Institute of Technology, Stockholm, Sweden).
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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/* (From RFC1521 and draft-ietf-dnssec-secext-03.txt)
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The following encoding technique is taken from RFC 1521 by Borenstein
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and Freed. It is reproduced here in a slightly edited form for
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A 65-character subset of US-ASCII is used, enabling 6 bits to be
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represented per printable character. (The extra 65th character, "=",
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is used to signify a special processing function.)
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The encoding process represents 24-bit groups of input bits as output
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strings of 4 encoded characters. Proceeding from left to right, a
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24-bit input group is formed by concatenating 3 8-bit input groups.
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These 24 bits are then treated as 4 concatenated 6-bit groups, each
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of which is translated into a single digit in the base64 alphabet.
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Each 6-bit group is used as an index into an array of 64 printable
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characters. The character referenced by the index is placed in the
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Table 1: The Base64 Alphabet
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Value Encoding Value Encoding Value Encoding Value Encoding
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14 O 31 f 48 w (pad) =
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Special processing is performed if fewer than 24 bits are available
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at the end of the data being encoded. A full encoding quantum is
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always completed at the end of a quantity. When fewer than 24 input
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bits are available in an input group, zero bits are added (on the
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right) to form an integral number of 6-bit groups. Padding at the
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end of the data is performed using the '=' character.
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Since all base64 input is an integral number of octets, only the
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-------------------------------------------------
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following cases can arise:
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(1) the final quantum of encoding input is an integral
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multiple of 24 bits; here, the final unit of encoded
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output will be an integral multiple of 4 characters
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(2) the final quantum of encoding input is exactly 8 bits;
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here, the final unit of encoded output will be two
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characters followed by two "=" padding characters, or
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(3) the final quantum of encoding input is exactly 16 bits;
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here, the final unit of encoded output will be three
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characters followed by one "=" padding character.
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/* $Id: base64.c,v 1.5 2001/05/28 17:33:41 joda Exp $ */
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* Code taken from Kerberos krb4-1.2.2
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/* Useful for encoding */
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static char base64_chars[] =
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"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
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/* For constant time lookups */
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is_base64_char(char c)
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return (('A' <= c && c <= 'Z') || ('a' <= c && c <= 'z') ||
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('0' <= c && c <= '9') || (c == '+' || c == '/'));
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for (p = base64_chars; *p; p++)
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return p - base64_chars;
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base64_encode(const void *data, int size, char **str)
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const unsigned char *q;
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p = s = (char *) malloc(size * 4 / 3 + 4);
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q = (const unsigned char *) data;
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for (i = 0; i < size;)
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p[0] = base64_chars[(c & 0x00fc0000) >> 18];
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p[1] = base64_chars[(c & 0x0003f000) >> 12];
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p[2] = base64_chars[(c & 0x00000fc0) >> 6];
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p[3] = base64_chars[(c & 0x0000003f) >> 0];
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#define DECODE_ERROR ((unsigned) -1)
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token_decode(const char *token, const size_t size)
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unsigned int val = 0;
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for (i = 0; i < 4; i++)
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val += pos(token[i]);
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return (marker << 24) | val;
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base64_decode(const char *str, void *data)
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for (p = str; *p && (*p == '=' || is_base64_char(*p)); p += 4, size -= 4)
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unsigned int val = token_decode(p, size);
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unsigned int marker = (val >> 24) & 0xff;
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if (val == DECODE_ERROR)
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*q++ = (val >> 16) & 0xff;
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*q++ = (val >> 8) & 0xff;
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return q - (unsigned char *) data;
added
removed
src/base64.c
