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base64.c

/***
  This file is part of PulseAudio.

  Copyright 2008 Colin Guthrie

  PulseAudio is free software; you can redistribute it and/or modify
  it under the terms of the GNU Lesser General Public License as published
  by the Free Software Foundation; either version 2.1 of the License,
  or (at your option) any later version.

  PulseAudio is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with PulseAudio; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  USA.
***/

/*
  This file was originally inspired by a file developed by
    Kungliga Tekniska H�gskolan
*/

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdlib.h>
#include <string.h>

#include <pulse/xmalloc.h>

#include "base64.h"

static const char base64_chars[] =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

static int pos(char c)
{
    if (c >= 'A' && c <= 'Z') return c - 'A' + 0;
    if (c >= 'a' && c <= 'z') return c - 'a' + 26;
    if (c >= '0' && c <= '9') return c - '0' + 52;
    if (c == '+') return 62;
    if (c == '/') return 63;
    return -1;
}

int pa_base64_encode(const void *data, int size, char **str)
{
    char *s, *p;
    int i;
    int c;
    const unsigned char *q;

    p = s = pa_xnew(char, size * 4 / 3 + 4);
    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);
}

#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 {
            int lpos = pos(token[i]);
            if (lpos < 0)
                return DECODE_ERROR;
            val += lpos;
        }
    }
    if (marker > 2)
        return DECODE_ERROR;
    return (marker << 24) | val;
}

int pa_base64_decode(const char *str, void *data)
{
    const char *p;
    unsigned char *q;

    q = 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;
}

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