/*
* Copyright 2007 ZXing authors
*
* 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.
*/
using System;
namespace com.google.zxing.qrcode.decoder
{
/// <summary> <p>Encapsulates a QR Code's format information, including the data mask used and
/// error correction level.</p>
///
/// </summary>
/// <author> Sean Owen
/// </author>
/// <author>www.Redivivus.in (suraj.supekar@redivivus.in) - Ported from ZXING Java Source
/// </author>
/// <seealso cref="DataMask">
/// </seealso>
/// <seealso cref="ErrorCorrectionLevel">
/// </seealso>
sealed class FormatInformation
{
internal ErrorCorrectionLevel ErrorCorrectionLevel
{
get
{
return errorCorrectionLevel;
}
}
internal sbyte DataMask
{
get
{
return dataMask;
}
}
private const int FORMAT_INFO_MASK_QR = 0x5412;
/// <summary> See ISO 18004:2006, Annex C, Table C.1</summary>
//UPGRADE_NOTE: Final was removed from the declaration of 'FORMAT_INFO_DECODE_LOOKUP'. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
private static readonly int[][] FORMAT_INFO_DECODE_LOOKUP = new int[][]{new int[]{0x5412, 0x00}, new int[]{0x5125, 0x01}, new int[]{0x5E7C, 0x02}, new int[]{0x5B4B, 0x03}, new int[]{0x45F9, 0x04}, new int[]{0x40CE, 0x05}, new int[]{0x4F97, 0x06}, new int[]{0x4AA0, 0x07}, new int[]{0x77C4, 0x08}, new int[]{0x72F3, 0x09}, new int[]{0x7DAA, 0x0A}, new int[]{0x789D, 0x0B}, new int[]{0x662F, 0x0C}, new int[]{0x6318, 0x0D}, new int[]{0x6C41, 0x0E}, new int[]{0x6976, 0x0F}, new int[]{0x1689, 0x10}, new int[]{0x13BE, 0x11}, new int[]{0x1CE7, 0x12}, new int[]{0x19D0, 0x13}, new int[]{0x0762, 0x14}, new int[]{0x0255, 0x15}, new int[]{0x0D0C, 0x16}, new int[]{0x083B, 0x17}, new int[]{0x355F, 0x18}, new int[]{0x3068, 0x19}, new int[]{0x3F31, 0x1A}, new int[]{0x3A06, 0x1B}, new int[]{0x24B4, 0x1C}, new int[]{0x2183, 0x1D}, new int[]{0x2EDA, 0x1E}, new int[]{0x2BED, 0x1F}};
/// <summary> Offset i holds the number of 1 bits in the binary representation of i</summary>
//UPGRADE_NOTE: Final was removed from the declaration of 'BITS_SET_IN_HALF_BYTE'. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
private static readonly int[] BITS_SET_IN_HALF_BYTE = new int[]{0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4};
//UPGRADE_NOTE: Final was removed from the declaration of 'errorCorrectionLevel '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
private ErrorCorrectionLevel errorCorrectionLevel;
//UPGRADE_NOTE: Final was removed from the declaration of 'dataMask '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
private sbyte dataMask;
private FormatInformation(int formatInfo)
{
// Bits 3,4
errorCorrectionLevel = ErrorCorrectionLevel.forBits((formatInfo >> 3) & 0x03);
// Bottom 3 bits
dataMask = (sbyte) (formatInfo & 0x07);
}
internal static int numBitsDiffering(int a, int b)
{
a ^= b; // a now has a 1 bit exactly where its bit differs with b's
// Count bits set quickly with a series of lookups:
return BITS_SET_IN_HALF_BYTE[a & 0x0F] + BITS_SET_IN_HALF_BYTE[(SupportClass.URShift(a, 4) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(SupportClass.URShift(a, 8) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(SupportClass.URShift(a, 12) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(SupportClass.URShift(a, 16) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(SupportClass.URShift(a, 20) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(SupportClass.URShift(a, 24) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(SupportClass.URShift(a, 28) & 0x0F)];
}
/// <param name="maskedFormatInfo">format info indicator, with mask still applied
/// </param>
/// <returns> information about the format it specifies, or <code>null</code>
/// if doesn't seem to match any known pattern
/// </returns>
internal static FormatInformation decodeFormatInformation(int maskedFormatInfo)
{
FormatInformation formatInfo = doDecodeFormatInformation(maskedFormatInfo);
if (formatInfo != null)
{
return formatInfo;
}
// Should return null, but, some QR codes apparently
// do not mask this info. Try again by actually masking the pattern
// first
return doDecodeFormatInformation(maskedFormatInfo ^ FORMAT_INFO_MASK_QR);
}
private static FormatInformation doDecodeFormatInformation(int maskedFormatInfo)
{
// Find the int in FORMAT_INFO_DECODE_LOOKUP with fewest bits differing
int bestDifference = System.Int32.MaxValue;
int bestFormatInfo = 0;
for (int i = 0; i < FORMAT_INFO_DECODE_LOOKUP.Length; i++)
{
int[] decodeInfo = FORMAT_INFO_DECODE_LOOKUP[i];
int targetInfo = decodeInfo[0];
if (targetInfo == maskedFormatInfo)
{
// Found an exact match
return new FormatInformation(decodeInfo[1]);
}
int bitsDifference = numBitsDiffering(maskedFormatInfo, targetInfo);
if (bitsDifference < bestDifference)
{
bestFormatInfo = decodeInfo[1];
bestDifference = bitsDifference;
}
}
// Hamming distance of the 32 masked codes is 7, by construction, so <= 3 bits
// differing means we found a match
if (bestDifference <= 3)
{
return new FormatInformation(bestFormatInfo);
}
return null;
}
public override int GetHashCode()
{
return (errorCorrectionLevel.ordinal() << 3) | (int) dataMask;
}
public override bool Equals(System.Object o)
{
if (!(o is FormatInformation))
{
return false;
}
FormatInformation other = (FormatInformation) o;
return this.errorCorrectionLevel == other.errorCorrectionLevel && this.dataMask == other.dataMask;
}
}
}