ECC code mismatch detection

QRCoder/PayloadGenerator.cs

@@ -15,7 +15,7 @@ public static class PayloadGenerator
         public abstract class Payload
         {
             public virtual int Version { get { return -1; } }
-            public virtual QRCodeGenerator.ECCLevel EccLevel { get { return QRCodeGenerator.ECCLevel.M; } }
+            public virtual QRCodeGenerator.ECCLevel EccLevel { get { return QRCodeGenerator.ECCLevel.Default; } }
             public virtual QRCodeGenerator.EciMode EciMode { get { return QRCodeGenerator.EciMode.Default; } }
             public abstract override string ToString();
         }

QRCoder/QRCodeGenerator.ECCLevel.cs

@@ -8,29 +8,35 @@ public partial class QRCodeGenerator
         /// </summary>
         public enum ECCLevel
         {
+            /// <summary>
+            /// Default error correction level, which will select Level M (Medium) unless otherwise specified by the payload.
+            /// Level M allows approximately 15% of data to be recovered, offering a balance between data capacity and error recovery.
+            /// </summary>
+            Default = -1,
+
             /// <summary>
             /// Level L: Low error correction (approximately 7% of data can be recovered).
             /// This level allows the highest data density.
             /// </summary>
-            L,
+            L = 0,
 
             /// <summary>
             /// Level M: Medium error correction (approximately 15% of data can be recovered).
             /// Offers a balance between data capacity and error recovery.
             /// </summary>
-            M,
+            M = 1,
 
             /// <summary>
             /// Level Q: Quartile error correction (approximately 25% of data can be recovered).
             /// More robust error correction at the cost of reduced data capacity.
             /// </summary>
-            Q,
+            Q = 2,
 
             /// <summary>
             /// Level H: High error correction (approximately 30% of data can be recovered).
             /// Provides the highest level of error recovery, ideal for environments with high risk of data loss.
             /// </summary>
-            H
+            H = 3
         }
     }
 }

QRCoder/QRCodeGenerator.cs

@@ -105,6 +105,10 @@ public static QRCodeData GenerateQrCode(PayloadGenerator.Payload payload)
         /// <returns>Returns the raw QR code data which can be used for rendering.</returns>
         public static QRCodeData GenerateQrCode(PayloadGenerator.Payload payload, ECCLevel eccLevel)
         {
+            if (eccLevel == ECCLevel.Default)
+                eccLevel = payload.EccLevel;
+            else if (payload.EccLevel != ECCLevel.Default && eccLevel != payload.EccLevel)
+                throw new ArgumentOutOfRangeException(nameof(eccLevel), $"The provided payload requires a ECC level of {eccLevel}.");
             return GenerateQrCode(payload.ToString(), eccLevel, false, false, payload.EciMode, payload.Version);
         }
 
@@ -121,6 +125,7 @@ public static QRCodeData GenerateQrCode(PayloadGenerator.Payload payload, ECCLev
         /// <returns>Returns the raw QR code data which can be used for rendering.</returns>
         public static QRCodeData GenerateQrCode(string plainText, ECCLevel eccLevel, bool forceUtf8 = false, bool utf8BOM = false, EciMode eciMode = EciMode.Default, int requestedVersion = -1)
         {
+            eccLevel = ValidateECCLevel(eccLevel);
             EncodingMode encoding = GetEncodingFromPlaintext(plainText, forceUtf8);
             var codedText = PlainTextToBinary(plainText, encoding, eciMode, utf8BOM, forceUtf8);
             var dataInputLength = GetDataLength(encoding, plainText, codedText, forceUtf8);
@@ -165,7 +170,6 @@ public static QRCodeData GenerateQrCode(string plainText, ECCLevel eccLevel, boo
             return GenerateQrCode(completeBitArray, eccLevel, version);
         }
 
-
         /// <summary>
         /// Calculates the QR code data which than can be used in one of the rendering classes to generate a graphical representation.
         /// </summary>
@@ -175,6 +179,7 @@ public static QRCodeData GenerateQrCode(string plainText, ECCLevel eccLevel, boo
         /// <returns>Returns the raw QR code data which can be used for rendering.</returns>
         public static QRCodeData GenerateQrCode(byte[] binaryData, ECCLevel eccLevel)
         {
+            eccLevel = ValidateECCLevel(eccLevel);
             int version = GetVersion(binaryData.Length, EncodingMode.Byte, eccLevel);
 
             int countIndicatorLen = GetCountIndicatorLength(version, EncodingMode.Byte);
@@ -187,6 +192,27 @@ public static QRCodeData GenerateQrCode(byte[] binaryData, ECCLevel eccLevel)
             return GenerateQrCode(bitArray, eccLevel, version);
         }
 
+        /// <summary>
+        /// Validates the specified error correction level.
+        /// Returns the provided level if it is valid, or the level M if the provided level is Default.
+        /// Throws an exception if an invalid level is provided.
+        /// </summary>
+        private static ECCLevel ValidateECCLevel(ECCLevel eccLevel)
+        {
+            switch (eccLevel)
+            {
+                case ECCLevel.L:
+                case ECCLevel.M:
+                case ECCLevel.Q:
+                case ECCLevel.H:
+                    return eccLevel;
+                case ECCLevel.Default:
+                    return ECCLevel.M;
+                default:
+                    throw new ArgumentOutOfRangeException(nameof(eccLevel), eccLevel, "Invalid error correction level.");
+            }
+        }
+
         private static readonly BitArray _repeatingPattern = new BitArray(
             new[] { true, true, true, false, true, true, false, false, false, false, false, true, false, false, false, true });
 
@@ -371,7 +397,7 @@ void WriteEccLevelAndVersion()
 #endif
         private static void TrimLeadingZeros(BitArray fStrEcc, ref int index, ref int count)
         {
-            while (!fStrEcc[index])
+            while (count > 0 && !fStrEcc[index])
             {
                 index++;
                 count--;

QRCoderApiTests/net35+net40+net50+net50-windows+netstandard20/QRCoder.approved.txt

@@ -895,6 +895,7 @@ namespace QRCoder
         public static QRCoder.QRCodeData GenerateQrCode(string plainText, QRCoder.QRCodeGenerator.ECCLevel eccLevel, bool forceUtf8 = false, bool utf8BOM = false, QRCoder.QRCodeGenerator.EciMode eciMode = 0, int requestedVersion = -1) { }
         public enum ECCLevel
         {
+            Default = -1,
             L = 0,
             M = 1,
             Q = 2,

QRCoderApiTests/net60-windows/QRCoder.approved.txt

@@ -903,6 +903,7 @@ namespace QRCoder
         public static QRCoder.QRCodeData GenerateQrCode(string plainText, QRCoder.QRCodeGenerator.ECCLevel eccLevel, bool forceUtf8 = false, bool utf8BOM = false, QRCoder.QRCodeGenerator.EciMode eciMode = 0, int requestedVersion = -1) { }
         public enum ECCLevel
         {
+            Default = -1,
             L = 0,
             M = 1,
             Q = 2,

QRCoderApiTests/net60/QRCoder.approved.txt

@@ -837,6 +837,7 @@ namespace QRCoder
         public static QRCoder.QRCodeData GenerateQrCode(string plainText, QRCoder.QRCodeGenerator.ECCLevel eccLevel, bool forceUtf8 = false, bool utf8BOM = false, QRCoder.QRCodeGenerator.EciMode eciMode = 0, int requestedVersion = -1) { }
         public enum ECCLevel
         {
+            Default = -1,
             L = 0,
             M = 1,
             Q = 2,

QRCoderApiTests/netstandard13/QRCoder.approved.txt

@@ -802,6 +802,7 @@ namespace QRCoder
         public static QRCoder.QRCodeData GenerateQrCode(string plainText, QRCoder.QRCodeGenerator.ECCLevel eccLevel, bool forceUtf8 = false, bool utf8BOM = false, QRCoder.QRCodeGenerator.EciMode eciMode = 0, int requestedVersion = -1) { }
         public enum ECCLevel
         {
+            Default = -1,
             L = 0,
             M = 1,
             Q = 2,

QRCoderTests/QRGeneratorTests.cs

@@ -7,6 +7,7 @@
 using System.Linq;
 using System.Collections;
 using System.Text;
+using System;
 
 namespace QRCoderTests
 {
@@ -191,6 +192,16 @@ public void can_generate_from_bytes()
             result.ShouldBe("0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001111111011001011111110000000010000010010010100000100000000101110101010101011101000000001011101010010010111010000000010111010111000101110100000000100000100000001000001000000001111111010101011111110000000000000000011000000000000000000111100101010010011101000000001011100001001001001110000000010101011111011111110100000000000101000000110000000000000001011001001010100110000000000000000000110001000101000000000111111100110011011110000000001000001001111110111010000000010111010011100100101100000000101110101110010010010000000001011101011010100011000000000010000010110110101000100000000111111101011100010000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000");
         }
 
+        [Fact]
+        [Category("QRGenerator/TextEncoding")]
+        public void trim_leading_zeros_works()
+        {
+            var gen = new QRCodeGenerator();
+            var qrData = gen.CreateQrCode("this is a test", QRCodeGenerator.ECCLevel.M);
+            var result = string.Join("", qrData.ModuleMatrix.Select(x => x.ToBitString()).ToArray());
+            result.ShouldBe("0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001111111001101011111110000000010000010010000100000100000000101110101101101011101000000001011101010001010111010000000010111010101010101110100000000100000101010101000001000000001111111010101011111110000000000000000110010000000000000000101111100011101111100000000001110100011110001100010000000001100011010110010011000000000100111000011010011100000000001001011001101011000100000000000000000100100001001100000000111111100111110001110000000001000001010011000011010000000010111010101110111101100000000101110101000000110100000000001011101011111000010000000000010000010010011010010000000000111111101101111100010000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000");
+        }
+
         [Fact]
         [Category("QRGenerator/TextEncoding")]
         public void isValidIso_works()
@@ -216,6 +227,78 @@ bool IsValidISO(string input)
                 }
             }
         }
+
+        [Fact]
+        [Category("QRGenerator/EccLevel")]
+        public void ecc_level_from_payload_works()
+        {
+            var stringValue = "this is a test";
+
+            // set up baselines
+            var expectedL = Encode(QRCodeGenerator.GenerateQrCode(stringValue, QRCodeGenerator.ECCLevel.L));
+            var expectedM = Encode(QRCodeGenerator.GenerateQrCode(stringValue, QRCodeGenerator.ECCLevel.M));
+            var expectedQ = Encode(QRCodeGenerator.GenerateQrCode(stringValue, QRCodeGenerator.ECCLevel.Q));
+            var expectedH = Encode(QRCodeGenerator.GenerateQrCode(stringValue, QRCodeGenerator.ECCLevel.H));
+
+            // ensure that the baselines are different from each other
+            expectedL.ShouldNotBe(expectedM);
+            expectedL.ShouldNotBe(expectedQ);
+            expectedL.ShouldNotBe(expectedH);
+            expectedM.ShouldNotBe(expectedQ);
+            expectedM.ShouldNotBe(expectedH);
+            expectedQ.ShouldNotBe(expectedH);
+
+            // validate that any ECC level can be used when the payload specifies a default ECC level
+            var payloadDefault = new SamplePayload(stringValue, QRCodeGenerator.ECCLevel.Default);
+            Encode(QRCodeGenerator.GenerateQrCode(payloadDefault)).ShouldBe(expectedM);
+            Encode(QRCodeGenerator.GenerateQrCode(payloadDefault, QRCodeGenerator.ECCLevel.Default)).ShouldBe(expectedM);
+            Encode(QRCodeGenerator.GenerateQrCode(payloadDefault, QRCodeGenerator.ECCLevel.L)).ShouldBe(expectedL);
+            Encode(QRCodeGenerator.GenerateQrCode(payloadDefault, QRCodeGenerator.ECCLevel.M)).ShouldBe(expectedM);
+            Encode(QRCodeGenerator.GenerateQrCode(payloadDefault, QRCodeGenerator.ECCLevel.Q)).ShouldBe(expectedQ);
+            Encode(QRCodeGenerator.GenerateQrCode(payloadDefault, QRCodeGenerator.ECCLevel.H)).ShouldBe(expectedH);
+
+            // validate that the ECC level specified in the payload is used when default is specified,
+            //   or checks that the selected ECC level matches the payload ECC level, throwing an exception otherwise
+            Verify(QRCodeGenerator.ECCLevel.L, expectedL);
+            Verify(QRCodeGenerator.ECCLevel.M, expectedM);
+            Verify(QRCodeGenerator.ECCLevel.Q, expectedQ);
+            Verify(QRCodeGenerator.ECCLevel.H, expectedH);
+
+
+            void Verify(QRCodeGenerator.ECCLevel eccLevel, string expected)
+            {
+                var payload = new SamplePayload(stringValue, eccLevel);
+                Encode(QRCodeGenerator.GenerateQrCode(payload)).ShouldBe(expected);
+                foreach (var ecc in Enum.GetValues(typeof(QRCodeGenerator.ECCLevel)).Cast<QRCodeGenerator.ECCLevel>())
+                {
+                    if (ecc == eccLevel || ecc == QRCodeGenerator.ECCLevel.Default)
+                        Encode(QRCodeGenerator.GenerateQrCode(payload, ecc)).ShouldBe(expected);
+                    else
+                        Should.Throw<ArgumentOutOfRangeException>(() => Encode(QRCodeGenerator.GenerateQrCode(payload, ecc)));
+                }
+            }
+
+            string Encode(QRCodeData qrData)
+            {
+                return string.Join("", qrData.ModuleMatrix.Select(x => x.ToBitString()).ToArray());
+            }
+        }
+
+        private class SamplePayload : PayloadGenerator.Payload
+        {
+            private string _data;
+            private QRCodeGenerator.ECCLevel _eccLevel;
+
+            public SamplePayload(string data, QRCodeGenerator.ECCLevel eccLevel)
+            {
+                _data = data;
+                _eccLevel = eccLevel;
+            }
+
+            public override QRCodeGenerator.ECCLevel EccLevel => _eccLevel;
+
+            public override string ToString() => _data;
+        }
     }
 
     public static class ExtensionMethods