MasterPassword/core/c/base64.c

/* ====================================================================
* Copyright (c) 1995-1999 The Apache Group.  All rights reserved.
*
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* on public domain software written at the National Center for
* Supercomputing Applications, University of Illinois, Urbana-Champaign.
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*/

#include "base64.h"

/* aaaack but it's fast and const should make it shared text page. */
static const uint8_t b64ToBits[256] =
        {
                /* ASCII table */
                64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
                64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
                64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 62, 64, 64, 64, 63,
                52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 64, 64, 64, 64, 64, 64,
                64, 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, 64, 64, 64, 64, 64,
                64, 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, 64, 64, 64, 64, 64,
                64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
                64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
                64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
                64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
                64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
                64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
                64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
                64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64
        };

size_t mpw_base64_decode_max(const char *b64Text) {

    register const uint8_t *b64Cursor = (uint8_t *)b64Text;
    while (b64ToBits[*(b64Cursor++)] <= 63);
    int b64Size = (int)(b64Cursor - (uint8_t *)b64Text) - 1;

    // Every 4 b64 chars yield 3 plain bytes => len = 3 * ceil(b64Size / 4)
    return (size_t)(3 /*bytes*/ * ((b64Size + 4 /*chars*/ - 1) / 4 /*chars*/));
}

int mpw_base64_decode(uint8_t *plainBuf, const char *b64Text) {

    register const uint8_t *b64Cursor = (uint8_t *)b64Text;
    while (b64ToBits[*(b64Cursor++)] <= 63);
    int b64Remaining = (int)(b64Cursor - (uint8_t *)b64Text) - 1;

    b64Cursor = (uint8_t *)b64Text;
    register uint8_t *plainCursor = plainBuf;
    while (b64Remaining > 4) {
        *(plainCursor++) = (uint8_t)(b64ToBits[b64Cursor[0]] << 2 | b64ToBits[b64Cursor[1]] >> 4);
        *(plainCursor++) = (uint8_t)(b64ToBits[b64Cursor[1]] << 4 | b64ToBits[b64Cursor[2]] >> 2);
        *(plainCursor++) = (uint8_t)(b64ToBits[b64Cursor[2]] << 6 | b64ToBits[b64Cursor[3]]);
        b64Cursor += 4;
        b64Remaining -= 4;
    }

    /* Note: (b64Size == 1) would be an error, so just ingore that case */
    if (b64Remaining > 1)
        *(plainCursor++) = (uint8_t)(b64ToBits[b64Cursor[0]] << 2 | b64ToBits[b64Cursor[1]] >> 4);
    if (b64Remaining > 2)
        *(plainCursor++) = (uint8_t)(b64ToBits[b64Cursor[1]] << 4 | b64ToBits[b64Cursor[2]] >> 2);
    if (b64Remaining > 3)
        *(plainCursor++) = (uint8_t)(b64ToBits[b64Cursor[2]] << 6 | b64ToBits[b64Cursor[3]]);

    return (int)(plainCursor - plainBuf);
}

static const char basis_64[] =
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

size_t mpw_base64_encode_max(size_t plainSize) {

    // Every 3 plain bytes yield 4 b64 chars => len = 4 * ceil(plainSize / 3)
    return 4 /*chars*/ * (plainSize + 3 /*bytes*/ - 1) / 3 /*bytes*/;
}

int mpw_base64_encode(char *b64Text, const uint8_t *plainBuf, size_t plainSize) {

    size_t plainCursor = 0;
    char *b64Cursor = b64Text;
    for (; plainCursor < plainSize - 2; plainCursor += 3) {
        *b64Cursor++ = basis_64[((plainBuf[plainCursor] >> 2)) & 0x3F];
        *b64Cursor++ = basis_64[((plainBuf[plainCursor] & 0x3) << 4) |
                                ((plainBuf[plainCursor + 1] & 0xF0) >> 4)];
        *b64Cursor++ = basis_64[((plainBuf[plainCursor + 1] & 0xF) << 2) |
                                ((plainBuf[plainCursor + 2] & 0xC0) >> 6)];
        *b64Cursor++ = basis_64[plainBuf[plainCursor + 2] & 0x3F];
    }
    if (plainCursor < plainSize) {
        *b64Cursor++ = basis_64[(plainBuf[plainCursor] >> 2) & 0x3F];
        if (plainCursor == (plainSize - 1)) {
            *b64Cursor++ = basis_64[((plainBuf[plainCursor] & 0x3) << 4)];
            *b64Cursor++ = '=';
        }
        else {
            *b64Cursor++ = basis_64[((plainBuf[plainCursor] & 0x3) << 4) |
                                    ((plainBuf[plainCursor + 1] & 0xF0) >> 4)];
            *b64Cursor++ = basis_64[((plainBuf[plainCursor + 1] & 0xF) << 2)];
        }
        *b64Cursor++ = '=';
    }

    *b64Cursor = '\0';
    return (int)(b64Cursor - b64Text);
}