// Licensed to the .NET Foundation under one or more agreements. // The .NET Foundation licenses this file to you under the MIT license. // See the LICENSE file in the project root for more information. using System.Diagnostics; using System.Globalization; using System.Numerics; using System.Runtime.CompilerServices; using System.Runtime.InteropServices; using Internal.Runtime.CompilerServices; #if BIT64 using nuint = System.UInt64; #else using nuint = System.UInt32; #endif namespace System { public partial class String { // // Search/Query methods // [MethodImpl(MethodImplOptions.AggressiveInlining)] private static bool EqualsHelper(string strA, string strB) { Debug.Assert(strA != null); Debug.Assert(strB != null); Debug.Assert(strA.Length == strB.Length); return SpanHelpers.SequenceEqual( ref Unsafe.As(ref strA.GetRawStringData()), ref Unsafe.As(ref strB.GetRawStringData()), ((nuint)strA.Length) * 2); } [MethodImpl(MethodImplOptions.AggressiveInlining)] private static int CompareOrdinalHelper(string strA, int indexA, int countA, string strB, int indexB, int countB) { Debug.Assert(strA != null); Debug.Assert(strB != null); Debug.Assert(indexA >= 0 && indexB >= 0); Debug.Assert(countA >= 0 && countB >= 0); Debug.Assert(indexA + countA <= strA.Length && indexB + countB <= strB.Length); return SpanHelpers.SequenceCompareTo(ref Unsafe.Add(ref strA.GetRawStringData(), indexA), countA, ref Unsafe.Add(ref strB.GetRawStringData(), indexB), countB); } private static bool EqualsOrdinalIgnoreCase(string strA, string strB) { Debug.Assert(strA.Length == strB.Length); return CompareInfo.EqualsOrdinalIgnoreCase(ref strA.GetRawStringData(), ref strB.GetRawStringData(), strB.Length); } private static unsafe int CompareOrdinalHelper(string strA, string strB) { Debug.Assert(strA != null); Debug.Assert(strB != null); // NOTE: This may be subject to change if eliminating the check // in the callers makes them small enough to be inlined Debug.Assert(strA._firstChar == strB._firstChar, "For performance reasons, callers of this method should " + "check/short-circuit beforehand if the first char is the same."); int length = Math.Min(strA.Length, strB.Length); fixed (char* ap = &strA._firstChar) fixed (char* bp = &strB._firstChar) { char* a = ap; char* b = bp; // Check if the second chars are different here // The reason we check if _firstChar is different is because // it's the most common case and allows us to avoid a method call // to here. // The reason we check if the second char is different is because // if the first two chars the same we can increment by 4 bytes, // leaving us word-aligned on both 32-bit (12 bytes into the string) // and 64-bit (16 bytes) platforms. // For empty strings, the second char will be null due to padding. // The start of the string is the type pointer + string length, which // takes up 8 bytes on 32-bit, 12 on x64. For empty strings the null // terminator immediately follows, leaving us with an object // 10/14 bytes in size. Since everything needs to be a multiple // of 4/8, this will get padded and zeroed out. // For one-char strings the second char will be the null terminator. // NOTE: If in the future there is a way to read the second char // without pinning the string (e.g. System.Runtime.CompilerServices.Unsafe // is exposed to mscorlib, or a future version of C# allows inline IL), // then do that and short-circuit before the fixed. if (*(a + 1) != *(b + 1)) goto DiffOffset1; // Since we know that the first two chars are the same, // we can increment by 2 here and skip 4 bytes. // This leaves us 8-byte aligned, which results // on better perf for 64-bit platforms. length -= 2; a += 2; b += 2; // unroll the loop #if BIT64 while (length >= 12) { if (*(long*)a != *(long*)b) goto DiffOffset0; if (*(long*)(a + 4) != *(long*)(b + 4)) goto DiffOffset4; if (*(long*)(a + 8) != *(long*)(b + 8)) goto DiffOffset8; length -= 12; a += 12; b += 12; } #else // BIT64 while (length >= 10) { if (*(int*)a != *(int*)b) goto DiffOffset0; if (*(int*)(a + 2) != *(int*)(b + 2)) goto DiffOffset2; if (*(int*)(a + 4) != *(int*)(b + 4)) goto DiffOffset4; if (*(int*)(a + 6) != *(int*)(b + 6)) goto DiffOffset6; if (*(int*)(a + 8) != *(int*)(b + 8)) goto DiffOffset8; length -= 10; a += 10; b += 10; } #endif // BIT64 // Fallback loop: // go back to slower code path and do comparison on 4 bytes at a time. // This depends on the fact that the String objects are // always zero terminated and that the terminating zero is not included // in the length. For odd string sizes, the last compare will include // the zero terminator. while (length > 0) { if (*(int*)a != *(int*)b) goto DiffNextInt; length -= 2; a += 2; b += 2; } // At this point, we have compared all the characters in at least one string. // The longer string will be larger. return strA.Length - strB.Length; #if BIT64 DiffOffset8: a += 4; b += 4; DiffOffset4: a += 4; b += 4; #else // BIT64 // Use jumps instead of falling through, since // otherwise going to DiffOffset8 will involve // 8 add instructions before getting to DiffNextInt DiffOffset8: a += 8; b += 8; goto DiffOffset0; DiffOffset6: a += 6; b += 6; goto DiffOffset0; DiffOffset4: a += 2; b += 2; DiffOffset2: a += 2; b += 2; #endif // BIT64 DiffOffset0: // If we reached here, we already see a difference in the unrolled loop above #if BIT64 if (*(int*)a == *(int*)b) { a += 2; b += 2; } #endif // BIT64 DiffNextInt: if (*a != *b) return *a - *b; DiffOffset1: Debug.Assert(*(a + 1) != *(b + 1), "This char must be different if we reach here!"); return *(a + 1) - *(b + 1); } } // Provides a culture-correct string comparison. StrA is compared to StrB // to determine whether it is lexicographically less, equal, or greater, and then returns // either a negative integer, 0, or a positive integer; respectively. // public static int Compare(string? strA, string? strB) { return Compare(strA, strB, StringComparison.CurrentCulture); } // Provides a culture-correct string comparison. strA is compared to strB // to determine whether it is lexicographically less, equal, or greater, and then a // negative integer, 0, or a positive integer is returned; respectively. // The case-sensitive option is set by ignoreCase // public static int Compare(string? strA, string? strB, bool ignoreCase) { var comparisonType = ignoreCase ? StringComparison.CurrentCultureIgnoreCase : StringComparison.CurrentCulture; return Compare(strA, strB, comparisonType); } // Provides a more flexible function for string comparison. See StringComparison // for meaning of different comparisonType. public static int Compare(string? strA, string? strB, StringComparison comparisonType) { if (object.ReferenceEquals(strA, strB)) { CheckStringComparison(comparisonType); return 0; } // They can't both be null at this point. if (strA == null) { CheckStringComparison(comparisonType); return -1; } if (strB == null) { CheckStringComparison(comparisonType); return 1; } switch (comparisonType) { case StringComparison.CurrentCulture: case StringComparison.CurrentCultureIgnoreCase: return CultureInfo.CurrentCulture.CompareInfo.Compare(strA, strB, GetCaseCompareOfComparisonCulture(comparisonType)); case StringComparison.InvariantCulture: case StringComparison.InvariantCultureIgnoreCase: return CompareInfo.Invariant.Compare(strA, strB, GetCaseCompareOfComparisonCulture(comparisonType)); case StringComparison.Ordinal: // Most common case: first character is different. // Returns false for empty strings. if (strA._firstChar != strB._firstChar) { return strA._firstChar - strB._firstChar; } return CompareOrdinalHelper(strA, strB); case StringComparison.OrdinalIgnoreCase: return CompareInfo.CompareOrdinalIgnoreCase(strA, strB); default: throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType)); } } // Provides a culture-correct string comparison. strA is compared to strB // to determine whether it is lexicographically less, equal, or greater, and then a // negative integer, 0, or a positive integer is returned; respectively. // public static int Compare(string? strA, string? strB, CultureInfo? culture, CompareOptions options) { CultureInfo compareCulture = culture ?? CultureInfo.CurrentCulture; return compareCulture.CompareInfo.Compare(strA, strB, options); } // Provides a culture-correct string comparison. strA is compared to strB // to determine whether it is lexicographically less, equal, or greater, and then a // negative integer, 0, or a positive integer is returned; respectively. // The case-sensitive option is set by ignoreCase, and the culture is set // by culture // public static int Compare(string? strA, string? strB, bool ignoreCase, CultureInfo? culture) { var options = ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None; return Compare(strA, strB, culture, options); } // Determines whether two string regions match. The substring of strA beginning // at indexA of given length is compared with the substring of strB // beginning at indexB of the same length. // public static int Compare(string? strA, int indexA, string? strB, int indexB, int length) { // NOTE: It's important we call the boolean overload, and not the StringComparison // one. The two have some subtly different behavior (see notes in the former). return Compare(strA, indexA, strB, indexB, length, ignoreCase: false); } // Determines whether two string regions match. The substring of strA beginning // at indexA of given length is compared with the substring of strB // beginning at indexB of the same length. Case sensitivity is determined by the ignoreCase boolean. // public static int Compare(string? strA, int indexA, string? strB, int indexB, int length, bool ignoreCase) { // Ideally we would just forward to the string.Compare overload that takes // a StringComparison parameter, and just pass in CurrentCulture/CurrentCultureIgnoreCase. // That function will return early if an optimization can be applied, e.g. if // (object)strA == strB && indexA == indexB then it will return 0 straightaway. // There are a couple of subtle behavior differences that prevent us from doing so // however: // - string.Compare(null, -1, null, -1, -1, StringComparison.CurrentCulture) works // since that method also returns early for nulls before validation. It shouldn't // for this overload. // - Since we originally forwarded to CompareInfo.Compare for all of the argument // validation logic, the ArgumentOutOfRangeExceptions thrown will contain different // parameter names. // Therefore, we have to duplicate some of the logic here. int lengthA = length; int lengthB = length; if (strA != null) { lengthA = Math.Min(lengthA, strA.Length - indexA); } if (strB != null) { lengthB = Math.Min(lengthB, strB.Length - indexB); } var options = ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None; return CultureInfo.CurrentCulture.CompareInfo.Compare(strA, indexA, lengthA, strB, indexB, lengthB, options); } // Determines whether two string regions match. The substring of strA beginning // at indexA of length length is compared with the substring of strB // beginning at indexB of the same length. Case sensitivity is determined by the ignoreCase boolean, // and the culture is set by culture. // public static int Compare(string? strA, int indexA, string? strB, int indexB, int length, bool ignoreCase, CultureInfo? culture) { var options = ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None; return Compare(strA, indexA, strB, indexB, length, culture, options); } // Determines whether two string regions match. The substring of strA beginning // at indexA of length length is compared with the substring of strB // beginning at indexB of the same length. // public static int Compare(string? strA, int indexA, string? strB, int indexB, int length, CultureInfo? culture, CompareOptions options) { CultureInfo compareCulture = culture ?? CultureInfo.CurrentCulture; int lengthA = length; int lengthB = length; if (strA != null) { lengthA = Math.Min(lengthA, strA.Length - indexA); } if (strB != null) { lengthB = Math.Min(lengthB, strB.Length - indexB); } return compareCulture.CompareInfo.Compare(strA, indexA, lengthA, strB, indexB, lengthB, options); } public static int Compare(string? strA, int indexA, string? strB, int indexB, int length, StringComparison comparisonType) { CheckStringComparison(comparisonType); if (strA == null || strB == null) { if (object.ReferenceEquals(strA, strB)) { // They're both null return 0; } return strA == null ? -1 : 1; } if (length < 0) { throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_NegativeLength); } if (indexA < 0 || indexB < 0) { string paramName = indexA < 0 ? nameof(indexA) : nameof(indexB); throw new ArgumentOutOfRangeException(paramName, SR.ArgumentOutOfRange_Index); } if (strA.Length - indexA < 0 || strB.Length - indexB < 0) { string paramName = strA.Length - indexA < 0 ? nameof(indexA) : nameof(indexB); throw new ArgumentOutOfRangeException(paramName, SR.ArgumentOutOfRange_Index); } if (length == 0 || (object.ReferenceEquals(strA, strB) && indexA == indexB)) { return 0; } int lengthA = Math.Min(length, strA.Length - indexA); int lengthB = Math.Min(length, strB.Length - indexB); switch (comparisonType) { case StringComparison.CurrentCulture: case StringComparison.CurrentCultureIgnoreCase: return CultureInfo.CurrentCulture.CompareInfo.Compare(strA, indexA, lengthA, strB, indexB, lengthB, GetCaseCompareOfComparisonCulture(comparisonType)); case StringComparison.InvariantCulture: case StringComparison.InvariantCultureIgnoreCase: return CompareInfo.Invariant.Compare(strA, indexA, lengthA, strB, indexB, lengthB, GetCaseCompareOfComparisonCulture(comparisonType)); case StringComparison.Ordinal: return CompareOrdinalHelper(strA, indexA, lengthA, strB, indexB, lengthB); default: Debug.Assert(comparisonType == StringComparison.OrdinalIgnoreCase); // CheckStringComparison validated these earlier return CompareInfo.CompareOrdinalIgnoreCase(strA, indexA, lengthA, strB, indexB, lengthB); } } // Compares strA and strB using an ordinal (code-point) comparison. // public static int CompareOrdinal(string? strA, string? strB) { if (object.ReferenceEquals(strA, strB)) { return 0; } // They can't both be null at this point. if (strA == null) { return -1; } if (strB == null) { return 1; } // Most common case, first character is different. // This will return false for empty strings. if (strA._firstChar != strB._firstChar) { return strA._firstChar - strB._firstChar; } return CompareOrdinalHelper(strA, strB); } [MethodImpl(MethodImplOptions.AggressiveInlining)] internal static int CompareOrdinal(ReadOnlySpan strA, ReadOnlySpan strB) => SpanHelpers.SequenceCompareTo(ref MemoryMarshal.GetReference(strA), strA.Length, ref MemoryMarshal.GetReference(strB), strB.Length); // Compares strA and strB using an ordinal (code-point) comparison. // public static int CompareOrdinal(string? strA, int indexA, string? strB, int indexB, int length) { if (strA == null || strB == null) { if (object.ReferenceEquals(strA, strB)) { // They're both null return 0; } return strA == null ? -1 : 1; } // COMPAT: Checking for nulls should become before the arguments are validated, // but other optimizations which allow us to return early should come after. if (length < 0) { throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_NegativeCount); } if (indexA < 0 || indexB < 0) { string paramName = indexA < 0 ? nameof(indexA) : nameof(indexB); throw new ArgumentOutOfRangeException(paramName, SR.ArgumentOutOfRange_Index); } int lengthA = Math.Min(length, strA.Length - indexA); int lengthB = Math.Min(length, strB.Length - indexB); if (lengthA < 0 || lengthB < 0) { string paramName = lengthA < 0 ? nameof(indexA) : nameof(indexB); throw new ArgumentOutOfRangeException(paramName, SR.ArgumentOutOfRange_Index); } if (length == 0 || (object.ReferenceEquals(strA, strB) && indexA == indexB)) { return 0; } return CompareOrdinalHelper(strA, indexA, lengthA, strB, indexB, lengthB); } // Compares this String to another String (cast as object), returning an integer that // indicates the relationship. This method returns a value less than 0 if this is less than value, 0 // if this is equal to value, or a value greater than 0 if this is greater than value. // public int CompareTo(object? value) { if (value == null) { return 1; } if (!(value is string other)) { throw new ArgumentException(SR.Arg_MustBeString); } return CompareTo(other); // will call the string-based overload } // Determines the sorting relation of StrB to the current instance. // public int CompareTo(string? strB) { return string.Compare(this, strB, StringComparison.CurrentCulture); } // Determines whether a specified string is a suffix of the current instance. // // The case-sensitive and culture-sensitive option is set by options, // and the default culture is used. // public bool EndsWith(string value) { return EndsWith(value, StringComparison.CurrentCulture); } public bool EndsWith(string value, StringComparison comparisonType) { if ((object)value == null) { throw new ArgumentNullException(nameof(value)); } if ((object)this == (object)value) { CheckStringComparison(comparisonType); return true; } if (value.Length == 0) { CheckStringComparison(comparisonType); return true; } switch (comparisonType) { case StringComparison.CurrentCulture: case StringComparison.CurrentCultureIgnoreCase: return CultureInfo.CurrentCulture.CompareInfo.IsSuffix(this, value, GetCaseCompareOfComparisonCulture(comparisonType)); case StringComparison.InvariantCulture: case StringComparison.InvariantCultureIgnoreCase: return CompareInfo.Invariant.IsSuffix(this, value, GetCaseCompareOfComparisonCulture(comparisonType)); case StringComparison.Ordinal: int offset = this.Length - value.Length; return (uint)offset <= (uint)this.Length && this.AsSpan(offset).SequenceEqual(value); case StringComparison.OrdinalIgnoreCase: return this.Length < value.Length ? false : (CompareInfo.CompareOrdinalIgnoreCase(this, this.Length - value.Length, value.Length, value, 0, value.Length) == 0); default: throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType)); } } public bool EndsWith(string value, bool ignoreCase, CultureInfo? culture) { if (null == value) { throw new ArgumentNullException(nameof(value)); } if ((object)this == (object)value) { return true; } CultureInfo referenceCulture = culture ?? CultureInfo.CurrentCulture; return referenceCulture.CompareInfo.IsSuffix(this, value, ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None); } public bool EndsWith(char value) { int lastPos = Length - 1; return ((uint)lastPos < (uint)Length) && this[lastPos] == value; } // Determines whether two strings match. public override bool Equals(object? obj) { if (object.ReferenceEquals(this, obj)) return true; if (!(obj is string str)) return false; if (this.Length != str.Length) return false; return EqualsHelper(this, str); } // Determines whether two strings match. public bool Equals(string? value) { if (object.ReferenceEquals(this, value)) return true; // NOTE: No need to worry about casting to object here. // If either side of an == comparison between strings // is null, Roslyn generates a simple ceq instruction // instead of calling string.op_Equality. if (value == null) return false; if (this.Length != value.Length) return false; return EqualsHelper(this, value); } public bool Equals(string? value, StringComparison comparisonType) { if (object.ReferenceEquals(this, value)) { CheckStringComparison(comparisonType); return true; } if (value is null) { CheckStringComparison(comparisonType); return false; } switch (comparisonType) { case StringComparison.CurrentCulture: case StringComparison.CurrentCultureIgnoreCase: return (CultureInfo.CurrentCulture.CompareInfo.Compare(this, value, GetCaseCompareOfComparisonCulture(comparisonType)) == 0); case StringComparison.InvariantCulture: case StringComparison.InvariantCultureIgnoreCase: return (CompareInfo.Invariant.Compare(this, value, GetCaseCompareOfComparisonCulture(comparisonType)) == 0); case StringComparison.Ordinal: if (this.Length != value.Length) return false; return EqualsHelper(this, value); case StringComparison.OrdinalIgnoreCase: if (this.Length != value.Length) return false; return EqualsOrdinalIgnoreCase(this, value); default: throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType)); } } // Determines whether two Strings match. public static bool Equals(string? a, string? b) { if (object.ReferenceEquals(a,b)) { return true; } if (a is null || b is null || a.Length != b.Length) { return false; } return EqualsHelper(a, b); } public static bool Equals(string? a, string? b, StringComparison comparisonType) { if (object.ReferenceEquals(a, b)) { CheckStringComparison(comparisonType); return true; } if (a is null || b is null) { CheckStringComparison(comparisonType); return false; } switch (comparisonType) { case StringComparison.CurrentCulture: case StringComparison.CurrentCultureIgnoreCase: return (CultureInfo.CurrentCulture.CompareInfo.Compare(a, b, GetCaseCompareOfComparisonCulture(comparisonType)) == 0); case StringComparison.InvariantCulture: case StringComparison.InvariantCultureIgnoreCase: return (CompareInfo.Invariant.Compare(a, b, GetCaseCompareOfComparisonCulture(comparisonType)) == 0); case StringComparison.Ordinal: if (a.Length != b.Length) return false; return EqualsHelper(a, b); case StringComparison.OrdinalIgnoreCase: if (a.Length != b.Length) return false; return EqualsOrdinalIgnoreCase(a, b); default: throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType)); } } public static bool operator ==(string? a, string? b) { return string.Equals(a, b); } public static bool operator !=(string? a, string? b) { return !string.Equals(a, b); } // Gets a hash code for this string. If strings A and B are such that A.Equals(B), then // they will return the same hash code. [MethodImpl(MethodImplOptions.AggressiveInlining)] public override int GetHashCode() { ulong seed = Marvin.DefaultSeed; // Multiplication below will not overflow since going from positive Int32 to UInt32. return Marvin.ComputeHash32(ref Unsafe.As(ref _firstChar), (uint)_stringLength * 2 /* in bytes, not chars */, (uint)seed, (uint)(seed >> 32)); } // Gets a hash code for this string and this comparison. If strings A and B and comparison C are such // that string.Equals(A, B, C), then they will return the same hash code with this comparison C. public int GetHashCode(StringComparison comparisonType) => StringComparer.FromComparison(comparisonType).GetHashCode(this); [MethodImpl(MethodImplOptions.AggressiveInlining)] internal int GetHashCodeOrdinalIgnoreCase() { ulong seed = Marvin.DefaultSeed; return Marvin.ComputeHash32OrdinalIgnoreCase(ref _firstChar, _stringLength /* in chars, not bytes */, (uint)seed, (uint)(seed >> 32)); } // A span-based equivalent of String.GetHashCode(). Computes an ordinal hash code. [MethodImpl(MethodImplOptions.AggressiveInlining)] public static int GetHashCode(ReadOnlySpan value) { ulong seed = Marvin.DefaultSeed; // Multiplication below will not overflow since going from positive Int32 to UInt32. return Marvin.ComputeHash32(ref Unsafe.As(ref MemoryMarshal.GetReference(value)), (uint)value.Length * 2 /* in bytes, not chars */, (uint)seed, (uint)(seed >> 32)); } // A span-based equivalent of String.GetHashCode(StringComparison). Uses the specified comparison type. public static int GetHashCode(ReadOnlySpan value, StringComparison comparisonType) { switch (comparisonType) { case StringComparison.CurrentCulture: case StringComparison.CurrentCultureIgnoreCase: return CultureInfo.CurrentCulture.CompareInfo.GetHashCode(value, GetCaseCompareOfComparisonCulture(comparisonType)); case StringComparison.InvariantCulture: case StringComparison.InvariantCultureIgnoreCase: return CultureInfo.InvariantCulture.CompareInfo.GetHashCode(value, GetCaseCompareOfComparisonCulture(comparisonType)); case StringComparison.Ordinal: return GetHashCode(value); case StringComparison.OrdinalIgnoreCase: return GetHashCodeOrdinalIgnoreCase(value); default: ThrowHelper.ThrowArgumentException(ExceptionResource.NotSupported_StringComparison, ExceptionArgument.comparisonType); Debug.Fail("Should not reach this point."); return default; } } [MethodImpl(MethodImplOptions.AggressiveInlining)] internal static int GetHashCodeOrdinalIgnoreCase(ReadOnlySpan value) { ulong seed = Marvin.DefaultSeed; return Marvin.ComputeHash32OrdinalIgnoreCase(ref MemoryMarshal.GetReference(value), value.Length /* in chars, not bytes */, (uint)seed, (uint)(seed >> 32)); } // Use this if and only if 'Denial of Service' attacks are not a concern (i.e. never used for free-form user input), // or are otherwise mitigated internal unsafe int GetNonRandomizedHashCode() { fixed (char* src = &_firstChar) { Debug.Assert(src[this.Length] == '\0', "src[this.Length] == '\\0'"); Debug.Assert(((int)src) % 4 == 0, "Managed string should start at 4 bytes boundary"); uint hash1 = (5381 << 16) + 5381; uint hash2 = hash1; uint* ptr = (uint*)src; int length = this.Length; while (length > 2) { length -= 4; // Where length is 4n-1 (e.g. 3,7,11,15,19) this additionally consumes the null terminator hash1 = (BitOperations.RotateLeft(hash1, 5) + hash1) ^ ptr[0]; hash2 = (BitOperations.RotateLeft(hash2, 5) + hash2) ^ ptr[1]; ptr += 2; } if (length > 0) { // Where length is 4n-3 (e.g. 1,5,9,13,17) this additionally consumes the null terminator hash2 = (BitOperations.RotateLeft(hash2, 5) + hash2) ^ ptr[0]; } return (int)(hash1 + (hash2 * 1566083941)); } } // Determines whether a specified string is a prefix of the current instance // public bool StartsWith(string value) { if (value is null) { throw new ArgumentNullException(nameof(value)); } return StartsWith(value, StringComparison.CurrentCulture); } public bool StartsWith(string value, StringComparison comparisonType) { if (value is null) { throw new ArgumentNullException(nameof(value)); } if ((object)this == (object)value) { CheckStringComparison(comparisonType); return true; } if (value.Length == 0) { CheckStringComparison(comparisonType); return true; } switch (comparisonType) { case StringComparison.CurrentCulture: case StringComparison.CurrentCultureIgnoreCase: return CultureInfo.CurrentCulture.CompareInfo.IsPrefix(this, value, GetCaseCompareOfComparisonCulture(comparisonType)); case StringComparison.InvariantCulture: case StringComparison.InvariantCultureIgnoreCase: return CompareInfo.Invariant.IsPrefix(this, value, GetCaseCompareOfComparisonCulture(comparisonType)); case StringComparison.Ordinal: if (this.Length < value.Length || _firstChar != value._firstChar) { return false; } return (value.Length == 1) ? true : // First char is the same and thats all there is to compare SpanHelpers.SequenceEqual( ref Unsafe.As(ref this.GetRawStringData()), ref Unsafe.As(ref value.GetRawStringData()), ((nuint)value.Length) * 2); case StringComparison.OrdinalIgnoreCase: if (this.Length < value.Length) { return false; } return CompareInfo.EqualsOrdinalIgnoreCase(ref this.GetRawStringData(), ref value.GetRawStringData(), value.Length); default: throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType)); } } public bool StartsWith(string value, bool ignoreCase, CultureInfo? culture) { if (null == value) { throw new ArgumentNullException(nameof(value)); } if ((object)this == (object)value) { return true; } CultureInfo referenceCulture = culture ?? CultureInfo.CurrentCulture; return referenceCulture.CompareInfo.IsPrefix(this, value, ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None); } public bool StartsWith(char value) => Length != 0 && _firstChar == value; internal static void CheckStringComparison(StringComparison comparisonType) { // Single comparison to check if comparisonType is within [CurrentCulture .. OrdinalIgnoreCase] if ((uint)comparisonType > (uint)StringComparison.OrdinalIgnoreCase) { ThrowHelper.ThrowArgumentException(ExceptionResource.NotSupported_StringComparison, ExceptionArgument.comparisonType); } } internal static CompareOptions GetCaseCompareOfComparisonCulture(StringComparison comparisonType) { Debug.Assert((uint)comparisonType <= (uint)StringComparison.OrdinalIgnoreCase); // Culture enums can be & with CompareOptions.IgnoreCase 0x01 to extract if IgnoreCase or CompareOptions.None 0x00 // // CompareOptions.None 0x00 // CompareOptions.IgnoreCase 0x01 // // StringComparison.CurrentCulture: 0x00 // StringComparison.InvariantCulture: 0x02 // StringComparison.Ordinal 0x04 // // StringComparison.CurrentCultureIgnoreCase: 0x01 // StringComparison.InvariantCultureIgnoreCase: 0x03 // StringComparison.OrdinalIgnoreCase 0x05 return (CompareOptions)((int)comparisonType & (int)CompareOptions.IgnoreCase); } } }