base64.c

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/* This file is part of the YAZ toolkit.
 * Copyright (C) Index Data
 * See the file LICENSE for details.
 */
#if HAVE_CONFIG_H
#include <config.h>
#endif
 
#include <string.h>
#include <yaz/base64.h>
 
void yaz_base64encode(const char *in, char *out)
{
    static char encoding[] =
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
    unsigned char buf[3];
    long n;
 
    while (*in != 0)
    {
        const char *pad = 0;
        buf[0] = in[0];
        buf[1] = in[1];
        if (in[1] == 0)
        {
            buf[2] = 0;
            pad = "==";
        }
        else
        {
            buf[2] = in[2];
            if (in[2] == 0)
                pad = "=";
        }
 
        /* Treat three eight-bit numbers as on 24-bit number */
        n = (buf[0] << 16) + (buf[1] << 8) + buf[2];
 
        /* Write the six-bit chunks out as four encoded characters */
        *out++ = encoding[(n >> 18) & 63];
        *out++ = encoding[(n >> 12) & 63];
        if (in[1] != 0)
            *out++ = encoding[(n >> 6) & 63];
        if (in[1] != 0 && in[2] != 0)
            *out++ = encoding[n & 63];
 
        if (pad != 0) {
            while (*pad != 0)
                *out++ = *pad++;
            break;
        }
        in += 3;
    }
    *out++ = 0;
}
 
static int next_char(const char **in, size_t *len)
{
    const char *map = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
        "abcdefghijklmnopqrstuvwxyz0123456789+/";
    const char *p;
    while (*len > 0 && strchr("\r\n\t\f ", **in))
    {
        (*len)--;
        (*in)++;
    }
    if (*len > 0 && **in == '=')
        return -2;
    if (*len > 0 && (p = strchr(map, **in)))
    {
        (*len)--;
        (*in)++;
        return p - map;
    }
    return -1;
}
 
int yaz_base64decode(const char *in, char *out)
{
    size_t len = strlen(in);
 
    while (len >= 4)
    {
        int i0, i1, i2, i3;
 
        i0 = next_char(&in, &len);
        if (i0 < 0)
            return -1;
        i1 = next_char(&in, &len);
        if (i1 < 0)
            return -1;
        *(out++) = i0 << 2 | i1 >> 4;
        i2 = next_char(&in, &len);
        if (i2 == -2)
            break;
        if (i2 == -1)
            return -1;
        *(out++) = i1 << 4 | i2 >> 2;
        i3 = next_char(&in, &len);
        if (i3 == -2)
            break;
        if (i3 == -1)
            return -1;
        *(out++) = i2 << 6 | i3;
    }
    *out = '\0';
    return 0;
}
 
/*
 * Local variables:
 * c-basic-offset: 4
 * c-file-style: "Stroustrup"
 * indent-tabs-mode: nil
 * End:
 * vim: shiftwidth=4 tabstop=8 expandtab
 */