#include "encode.h"

#define PADDING '='

static
unsigned char b64toascii[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
                             "abcdefghijklmnopqrstuvwxyz" \
                             "0123456789" \
                             "+/";

static
unsigned char b64urltoascii[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
                                "abcdefghijklmnopqrstuvwxyz" \
                                "0123456789" \
                                "-_";

static
unsigned char asciitob64[] = {
     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
     0,  0,  0, 62,  0, 62,  0, 63, 52, 53,
    54, 55, 56, 57, 58, 59, 60, 61,  0,  0,
     0,  0,  0,  0,  0,  0,  1,  2,  3,  4,
     5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
    15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
    25,  0,  0,  0,  0, 63,  0, 26, 27, 28,
    29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
    39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
    49, 50, 51
};


int
encode(unsigned char *op, int olen, unsigned char *sp, int url)
{
    int tmp;
    unsigned char *table;
    unsigned char *sbeg;
    unsigned char *tend;

    table = (!url) ? b64toascii : b64urltoascii;

    sbeg = sp;
    tend = op + olen - (olen % 3);
    while (op < tend) {
        *sp++ = table[(*op & ~3) >> 2];
        tmp = (*op++ & 3) << 4;
        *sp++ = table[tmp + ((*op & ~15) >> 4)];
        tmp = (*op++ & 15) << 2;
        *sp++ = table[tmp + ((*op & 192) >> 6)];
        *sp++ = table[*op++ & ~192];
    }
    switch (olen % 3) {
        case 2:
            *sp++ = table[(*op & ~3) >> 2];
            tmp = (*op++ & 3) << 4;
            *sp++ = table[tmp + ((*op & ~15) >> 4)];
            *sp++ = table[(*op & 15) << 2];
            *sp++ = PADDING;
            break;
        case 1:
            *sp++ = table[(*op & ~3) >> 2];
            *sp++ = table[(*op & 3) << 4];
            *sp++ = PADDING;
            *sp++ = PADDING;
            break;
    }

    return sp-sbeg;
}

int
decode(unsigned char *sp, int slen, unsigned char *op)
{
    int tmp, b;
    unsigned char *obeg;
    unsigned char *qend;

    obeg = op;
    qend = sp + slen - (slen % 4);
    while (sp < qend) {
        tmp = asciitob64[*sp++] << 2;
        b = asciitob64[*sp++];
        *op++ = tmp + ((b & ~15) >> 4);
        tmp = (b & 15) << 4;
        b = asciitob64[*sp++];
        *op++ = tmp + ((b & ~3) >> 2);
        *op++ = ((b & 3) << 6) + asciitob64[*sp++];
    }
    switch (slen % 4) {
        case 3:
            tmp = asciitob64[*sp++] << 2;
            b = asciitob64[*sp++];
            *op++ = tmp + ((b & ~15) >> 4);
            tmp = (b & 15) << 4;
            *op++ = tmp + ((asciitob64[*sp++] & ~3) >> 2);
            break;
        case 2:
            tmp = asciitob64[*sp++] << 2;
            *op++ = tmp + ((asciitob64[*sp++] & ~15) >> 4);
            break;
    }

    return op-obeg;
}