authenticator-ios-v2/FreeOTP/base32.c

	base32.c revision 917bf5a50ae184ad61d48442e7f256ca286f688a
// Base32 implementation
//
// Copyright 2010 Google Inc.
// Author: Markus Gutschke
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#import <string.h>
#import "base32.h"

int
base32_decode(const char *encoded, uint8_t *result, int bufSize)
{
    int buffer = 0;
    int bitsLeft = 0;
    int count = 0;

    for (const char *ptr = encoded; count < bufSize && *ptr; ++ptr) {
        char ch = *ptr;
        if (ch == ' ' || ch == '\t' || ch == '\r' || ch == '\n' || ch == '-')
            continue;
        buffer <<= 5;

        // Deal with commonly mistyped characters
        if (ch == '0')
            ch = 'O';
        else if (ch == '1')
            ch = 'L';
        else if (ch == '8')
            ch = 'B';

        // Look up one base32 digit
        if ((ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z'))
            ch = (ch & 0x1F) - 1;
        else if (ch >= '2' && ch <= '7')
            ch -= '2' - 26;
        else
            return -1;

        buffer |= ch;
        bitsLeft += 5;
        if (bitsLeft >= 8) {
            result[count++] = buffer >> (bitsLeft - 8);
            bitsLeft -= 8;
        }
    }

    if (count < bufSize)
        result[count] = '\000';

    return count;
}

int
base32_encode(const uint8_t *data, int length, char *result, int bufSize)
{
    int count = 0;

    if (length < 0 || length > (1 << 28))
        return -1;

    if (length > 0) {
        int buffer = data[0];
        int next = 1;
        int bitsLeft = 8;

        while (count < bufSize && (bitsLeft > 0 || next < length)) {
            if (bitsLeft < 5) {
                if (next < length) {
                    buffer <<= 8;
                    buffer |= data[next++] & 0xFF;
                    bitsLeft += 8;
                } else {
                    int pad = 5 - bitsLeft;
                    buffer <<= pad;
                    bitsLeft += pad;
                }
            }

            int index = 0x1F & (buffer >> (bitsLeft - 5));
            bitsLeft -= 5;
            result[count++] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567"[index];
        }
    }

    if (count < bufSize)
        result[count] = '\000';

    return count;
}