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Merge pull request #521 from Shane32/string_optimizations
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Add string optimizations
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@codebude
codebude authored May 13, 2024
2 parents b26488e + 51e8c92 commit 6d41db5
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Showing 2 changed files with 126 additions and 22 deletions.
102 changes: 80 additions & 22 deletions QRCoder/QRCodeGenerator.cs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,7 @@
using System;
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1
using System.Buffers;
#endif
using System.Collections;
using System.Collections.Generic;
using System.Globalization;
Expand Down Expand Up @@ -711,14 +714,22 @@ bool IsUtf8()
}
}

private static readonly Encoding _iso88591ExceptionFallback = Encoding.GetEncoding(28591, new EncoderExceptionFallback(), new DecoderExceptionFallback()); // ISO-8859-1
/// <summary>
/// Checks if the given string can be accurately represented and retrieved in ISO-8859-1 encoding.
/// </summary>
private static bool IsValidISO(string input)
{
var bytes = Encoding.GetEncoding("ISO-8859-1").GetBytes(input);
var result = Encoding.GetEncoding("ISO-8859-1").GetString(bytes);
return String.Equals(input, result);
// No heap allocations if the string is ISO-8859-1
try
{
_ = _iso88591ExceptionFallback.GetByteCount(input);
return true;
}
catch (EncoderFallbackException) // The exception is a heap allocation and not ideal
{
return false;
}
}

/// <summary>
Expand Down Expand Up @@ -832,18 +843,13 @@ private static BitArray PlainTextToBinaryAlphanumeric(string plainText)
return codeText;
}

/// <summary>
/// Returns a string that contains the original string, with characters that cannot be encoded by a
/// specified encoding (default of ISO-8859-2) with a replacement character.
/// </summary>
private static string ConvertToIso8859(string value, string Iso = "ISO-8859-2")
{
Encoding iso = Encoding.GetEncoding(Iso);
Encoding utf8 = Encoding.UTF8;
byte[] utfBytes = utf8.GetBytes(value);
byte[] isoBytes = Encoding.Convert(utf8, iso, utfBytes);
return iso.GetString(isoBytes);
}
private static readonly Encoding _iso8859_1 =
#if NET5_0_OR_GREATER
Encoding.Latin1;
#else
Encoding.GetEncoding(28591); // ISO-8859-1
#endif
private static Encoding _iso8859_2;

/// <summary>
/// Converts plain text into a binary format using byte mode encoding, which supports various character encodings through ECI (Extended Channel Interpretations).
Expand All @@ -860,35 +866,81 @@ private static string ConvertToIso8859(string value, string Iso = "ISO-8859-2")
/// </remarks>
private static BitArray PlainTextToBinaryByte(string plainText, EciMode eciMode, bool utf8BOM, bool forceUtf8)
{
byte[] codeBytes;
Encoding targetEncoding;

// Check if the text is valid ISO-8859-1 and UTF-8 is not forced, then encode using ISO-8859-1.
if (IsValidISO(plainText) && !forceUtf8)
codeBytes = Encoding.GetEncoding("ISO-8859-1").GetBytes(plainText);
{
targetEncoding = _iso8859_1;
utf8BOM = false;
}
else
{
// Determine the encoding based on the specified ECI mode.
switch (eciMode)
{
case EciMode.Iso8859_1:
// Convert text to ISO-8859-1 and encode.
codeBytes = Encoding.GetEncoding("ISO-8859-1").GetBytes(ConvertToIso8859(plainText, "ISO-8859-1"));
targetEncoding = _iso8859_1;
utf8BOM = false;
break;
case EciMode.Iso8859_2:
// Note: ISO-8859-2 is not natively supported on .NET Core
//
// Users must install the System.Text.Encoding.CodePages package and call Encoding.RegisterProvider(CodePagesEncodingProvider.Instance)
// before using this encoding mode.
if (_iso8859_2 == null)
_iso8859_2 = Encoding.GetEncoding(28592); // ISO-8859-2
// Convert text to ISO-8859-2 and encode.
codeBytes = Encoding.GetEncoding("ISO-8859-2").GetBytes(ConvertToIso8859(plainText, "ISO-8859-2"));
targetEncoding = _iso8859_2;
utf8BOM = false;
break;
case EciMode.Default:
case EciMode.Utf8:
default:
// Handle UTF-8 encoding, optionally adding a BOM if specified.
codeBytes = utf8BOM ? Encoding.UTF8.GetPreamble().Concat(Encoding.UTF8.GetBytes(plainText)).ToArray() : Encoding.UTF8.GetBytes(plainText);
targetEncoding = Encoding.UTF8;
break;
}
}

#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1
// We can use stackalloc for small arrays to prevent heap allocations
const int MAX_STACK_SIZE_IN_BYTES = 512;

int count = targetEncoding.GetByteCount(plainText);
byte[] bufferFromPool = null;
Span<byte> codeBytes = (count <= MAX_STACK_SIZE_IN_BYTES)
? (stackalloc byte[MAX_STACK_SIZE_IN_BYTES])
: (bufferFromPool = ArrayPool<byte>.Shared.Rent(count));
codeBytes = codeBytes.Slice(0, count);
targetEncoding.GetBytes(plainText, codeBytes);
#else
byte[] codeBytes = targetEncoding.GetBytes(plainText);
#endif

// Convert the array of bytes into a BitArray.
return ToBitArray(codeBytes);
BitArray bitArray;
if (utf8BOM)
{
// convert to bit array, leaving 24 bits for the UTF-8 preamble
bitArray = ToBitArray(codeBytes, 24);
// write UTF8 preamble (EF BB BF) to the BitArray
DecToBin(0xEF, 8, bitArray, 0);
DecToBin(0xBB, 8, bitArray, 8);
DecToBin(0xBF, 8, bitArray, 16);
}
else
{
bitArray = ToBitArray(codeBytes);
}

#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1
if (bufferFromPool != null)
ArrayPool<byte>.Shared.Return(bufferFromPool);
#endif

return bitArray;
}

/// <summary>
Expand All @@ -898,7 +950,13 @@ private static BitArray PlainTextToBinaryByte(string plainText, EciMode eciMode,
/// <param name="byteArray">The byte array to convert into a BitArray.</param>
/// <param name="prefixZeros">The number of leading zeros to prepend to the resulting BitArray.</param>
/// <returns>A BitArray representing the bits of the input byteArray, with optional leading zeros.</returns>
private static BitArray ToBitArray(byte[] byteArray, int prefixZeros = 0)
private static BitArray ToBitArray(
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1
ReadOnlySpan<byte> byteArray, // byte[] has an implicit cast to ReadOnlySpan<byte>
#else
byte[] byteArray,
#endif
int prefixZeros = 0)
{
// Calculate the total number of bits in the resulting BitArray including the prefix zeros.
var bitArray = new BitArray((int)((uint)byteArray.Length * 8) + prefixZeros);
Expand Down
46 changes: 46 additions & 0 deletions QRCoderTests/QRGeneratorTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -160,6 +160,26 @@ public void can_encode_byte()
result.ShouldBe("0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001111111001011011111110000000010000010011100100000100000000101110101101101011101000000001011101001010010111010000000010111010001010101110100000000100000100000101000001000000001111111010101011111110000000000000000110110000000000000000111011111111011000100000000001001110001100010000010000000010011110001010001001000000000110011010000001000110000000001110001111001010110110000000000000000111101010011100000000111111101111011100110000000001000001010011101110010000000010111010110101110010100000000101110100110001000110000000001011101011001000100010000000010000010100000100011000000000111111101110101010111000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000");
}

[Fact]
[Category("QRGenerator/TextEncoding")]
public void can_encode_utf8()
{
var gen = new QRCodeGenerator();
var qrData = gen.CreateQrCode("https://en.wikipedia.org/wiki/🍕", QRCodeGenerator.ECCLevel.L, true, false, QRCodeGenerator.EciMode.Utf8);
var result = string.Join("", qrData.ModuleMatrix.Select(x => x.ToBitString()).ToArray());
result.ShouldBe("0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000011111110101011010011101111111000000001000001001111100001110100000100000000101110101110000011000010111010000000010111010111010111100101011101000000001011101010011010111010101110100000000100000100011010001110010000010000000011111110101010101010101111111000000000000000000101000011100000000000000000111100101011110101011100111010000000001011000101011111010011101010000000001010011101111101001111011101000000000111011011110000010001100000100000000000000010011010101100000000000000000001100110101011011111001101110000000000000011100001010101010110101000000000000111001011100110111111110011000000001110101011001011001000100011000000000000101010100001010111111000000000000010111010101001111100000001110000000000010110100010111111100100010100000000011101111010011101111111101010000000000000000110000001000100010010000000001111111001100011001010101101000000000100000100111111111011000111000000000010111010010100011010111110111000000001011101010110100011100101011000000000101110101100101111100101111010000000010000010111011001111000001101000000001111111011110000100000110101000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000");
}

[Fact]
[Category("QRGenerator/TextEncoding")]
public void can_encode_utf8_bom()
{
var gen = new QRCodeGenerator();
var qrData = gen.CreateQrCode("https://en.wikipedia.org/wiki/🍕", QRCodeGenerator.ECCLevel.L, true, true, QRCodeGenerator.EciMode.Utf8);
var result = string.Join("", qrData.ModuleMatrix.Select(x => x.ToBitString()).ToArray());
result.ShouldBe("0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000011111110010001101010101111111000000001000001011011000110000100000100000000101110100111010101111010111010000000010111010110100100010101011101000000001011101000101111000010101110100000000100000101010000111000010000010000000011111110101010101010101111111000000000000000000001010101110000000000000000111110111110101010100101010100000000000100000110000101000001100101000000000001001001011000011010000111100000000100010001111000001111110111010000000010110111010100011100100101111000000000001010001101101001000010100100000000100001101110011001010000001010000000001011001100011001111111010111000000000010001010101011110010100000100000000100100010000000000010110010000000000010110110010110000101010101100000000001001100100010010100111101101100000000101010110011000111101111100100000000000000000111011110011100011010000000001111111011100110010010101110000000000100000100100110010101000110110000000010111010110010111101111110011000000001011101010100000100010110100000000000101110101001100111110110111100000000010000010111100101111100100001000000001111111011110001110100111000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000");
}

[Fact]
[Category("QRGenerator/TextEncoding")]
public void can_generate_from_bytes()
Expand All @@ -170,6 +190,32 @@ public void can_generate_from_bytes()
var result = string.Join("", qrData.ModuleMatrix.Select(x => x.ToBitString()).ToArray());
result.ShouldBe("0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001111111011001011111110000000010000010010010100000100000000101110101010101011101000000001011101010010010111010000000010111010111000101110100000000100000100000001000001000000001111111010101011111110000000000000000011000000000000000000111100101010010011101000000001011100001001001001110000000010101011111011111110100000000000101000000110000000000000001011001001010100110000000000000000000110001000101000000000111111100110011011110000000001000001001111110111010000000010111010011100100101100000000101110101110010010010000000001011101011010100011000000000010000010110110101000100000000111111101011100010000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000");
}

[Fact]
[Category("QRGenerator/TextEncoding")]
public void isValidIso_works()
{
// see private method: QRCodeGenerator.IsValidISO

Encoding _iso88591ExceptionFallback = Encoding.GetEncoding(28591, new EncoderExceptionFallback(), new DecoderExceptionFallback()); // ISO-8859-1

IsValidISO("abc").ShouldBeTrue();
IsValidISO("äöü").ShouldBeTrue();
IsValidISO("🍕").ShouldBeFalse();

bool IsValidISO(string input)
{
try
{
_ = _iso88591ExceptionFallback.GetByteCount(input);
return true;
}
catch (EncoderFallbackException)
{
return false;
}
}
}
}

public static class ExtensionMethods
Expand Down

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