/* bijou HTTP server for plan 9 by sean caron (scaron@umich.edu) */

#include "main.h"
#include "base64.h"

int base64_encode(char *ip, char **op) {
    unsigned long r = 0;

    int pi = 0;
    int po = 0;

    *op = malloc(5*sizeof(char));

    if (*op == 0) {
        exits("MALLOC");
    }

    for (pi = 0; pi < strlen(ip)+1; pi = pi + 3) {
        if (ip[pi] == '\0') {
            *(*op + (4*po)) = '\0';
            break;
        }

        else if (ip[pi+1] == '\0') {
            // two characters output, == pad
            r = (ip[pi] << 24);

            *(*op + (4*po)) = base64_lut[r >> 26];
            *(*op + ((4*po)+1)) = base64_lut[(r << 6) >> 26];
            *(*op + ((4*po)+2)) = '=';
            *(*op + ((4*po)+3)) = '=';

            *(*op + ((4*po)+4)) = '\0';

            break;
        }

        else if (ip[pi+2] == '\0') {
            // three characters output, = pad

            r = (ip[pi] << 24) | (ip[pi+1] << 16);

            *(*op + (4*po)) = base64_lut[r >> 26];
            *(*op + ((4*po)+1)) = base64_lut[(r << 6) >> 26];
            *(*op + ((4*po)+2)) = base64_lut[(r << 12) >> 26];
            *(*op + ((4*po)+3)) = '=';

            *(*op + ((4*po)+4)) = '\0';

            break;
        }

        else {
            // four characters output, no pad
            r = (ip[pi] << 24) | (ip[pi+1] << 16) | (ip[pi+2] << 8);

            *(*op + (4*po)) = base64_lut[r >> 26];
            *(*op + ((4*po)+1)) = base64_lut[(r << 6) >> 26];
            *(*op + ((4*po)+2)) = base64_lut[(r << 12) >> 26];
            *(*op + ((4*po)+3)) = base64_lut[(r << 18) >> 26];
        }

        po = po + 1;

        *op = realloc(*op, sizeof(char)*((4*po)+5) );

        if ( *op == 0 ) {
            exits("REALLOC");
        }
    }

    return strlen(*op);
}

int base64_decode(char *ip, char **op) {
    unsigned long r = 0;
    unsigned char t[4] = {0, 0, 0, 0};

    int pi = 0;
    int po = 0;

    /* return with -1 to signal malformed input */

    if ((strlen(ip) % 4) != 0 ) {
        return -1;
    }

    *op = malloc( 4*sizeof(char) );

    if (*op == 0) {
        exits("MALLOC");
    }

    for (pi = 0; pi < strlen(ip); pi = pi + 4) {
        t[0] = base64_ilut[ip[pi]] << 2;
        t[1] = base64_ilut[ip[pi+1]] << 2;
        t[2] = base64_ilut[ip[pi+2]] << 2;
        t[3] = base64_ilut[ip[pi+3]] << 2;

        r = t[0] << 24;
        r = r & 0xFC000000;

        r = r | (t[1] << 18);
        r = r & 0xFFF00000;

        r = r | (t[2] << 12);
        r = r & 0xFFFFC000;

        r = r | (t[3] << 6);
        r = r & 0xFFFFFF00;

	/* the characters are packed in the three high order bytes of long, r. the lower 8 bits of r are zero */

        *(*op + (3*po)) = (char)(r>>24);
        *(*op + ((3*po)+1)) = (char)((r<<8)>>24);
        *(*op + ((3*po)+2)) = (char)((r<<16)>>24);

        *(*op + ((3*po)+3)) = '\0';

        po = po + 1;

        *op = realloc(*op, sizeof(char)*((4*po)+5) );

        if (*op == 0) {
            exits("REALLOC");
        }
    }

    return strlen(*op);
}