Re: OffTopic: Base64 over HTTPS

[Aleix Conchillo]

hope this helps. i don't remember where i found it...

any way, here you are.

#include <stdio.h>

#include "base64.h"

unsigned char alphabet[64] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

int
base64_decode(unsigned char *outbuf, unsigned char *inbuf, int size)
{
    static unsigned char inalphabet[256], decoder[256];
    int j, i, bits, c, char_count, errors = 0;

    for (i = (sizeof alphabet) - 1; i >= 0 ; i--) {
        inalphabet[alphabet[i]] = 1;
        decoder[alphabet[i]] = i;
    }

    char_count = 0;
    bits = 0;
    i = 0;
    j = 0;
    while (i<size) {
        c = inbuf[i++];
        if (c == '=') break;
        if (c > 255 || ! inalphabet[c]) continue;
        bits += decoder[c];
        char_count++;
        if (char_count == 4) {
            outbuf[j++] = bits >> 16;
            outbuf[j++] = (bits >> 8) & 0xff;
            outbuf[j++] = bits & 0xff;
            bits = 0;
            char_count = 0;
        } else {
            bits <<= 6;
        }
    }
    if (c == EOF) {
        if (char_count) errors++;
    } else { /* c == '=' */
        switch (char_count) {
        case 1:
            errors++;
            break;
        case 2:
            outbuf[j++] = bits >> 10;
            break;
        case 3:
            outbuf[j++] = bits >> 16;
            outbuf[j++] = (bits >> 8) & 0xff;
            break;
        }
    }
    return (errors ? 0 : j);
}

int
base64_encode(unsigned char *outbuf, unsigned char *inbuf, int size)
{
    int i, j, cols, bits, c, char_count;

    char_count = 0;
    bits = 0;
    cols = 0;
    i = 0;
    j = 0;
    while (i<size) {
        c = inbuf[i++];
        bits += c;
        char_count++;
        if (char_count == 3) {
            outbuf[j++] = alphabet[bits >> 18];
            outbuf[j++] = alphabet[(bits >> 12) & 0x3f];
            outbuf[j++] = alphabet[(bits >> 6) & 0x3f];
            outbuf[j++] = alphabet[bits & 0x3f];
            cols += 4;
            if (cols == 72) {
                outbuf[j++] = '\n';
                cols = 0;
            }
            bits = 0;
            char_count = 0;
        } else {
            bits <<= 8;
        }
    }
    if (char_count != 0) {
        bits <<= 16 - (8 * char_count);
        outbuf[j++] = alphabet[bits >> 18];
        outbuf[j++] = alphabet[(bits >> 12) & 0x3f];
        if (char_count == 1) {
            outbuf[j++] = '=';
            outbuf[j++] = '=';
        } else {
            outbuf[j++] = alphabet[(bits >> 6) & 0x3f];
            outbuf[j++] = '=';
        }
        if (cols > 0) outbuf[j++] = '\n';
    }
    return j;
}