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Diffstat (limited to 'src/System.Private.CoreLib/shared/System/String.Comparison.cs')
| -rw-r--r-- | src/System.Private.CoreLib/shared/System/String.Comparison.cs | 905 |
1 files changed, 905 insertions, 0 deletions
diff --git a/src/System.Private.CoreLib/shared/System/String.Comparison.cs b/src/System.Private.CoreLib/shared/System/String.Comparison.cs new file mode 100644 index 000000000..267bfe1fd --- /dev/null +++ b/src/System.Private.CoreLib/shared/System/String.Comparison.cs @@ -0,0 +1,905 @@ +// 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.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<char, byte>(ref strA.GetRawStringData()), + ref Unsafe.As<char, byte>(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) + { + if (culture == null) + { + throw new ArgumentNullException(nameof(culture)); + } + + return culture.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) + { + if (culture == null) + { + throw new ArgumentNullException(nameof(culture)); + } + + 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 culture.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<char> strA, ReadOnlySpan<char> 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; + } + + string other = value as string; + + if (other == null) + { + 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: + return this.Length < value.Length ? false : (CompareOrdinalHelper(this, this.Length - value.Length, value.Length, value, 0, value.Length) == 0); + + 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 thisLen = Length; + return thisLen != 0 && this[thisLen - 1] == value; + } + + // Determines whether two strings match. + public override bool Equals(object obj) + { + if (object.ReferenceEquals(this, obj)) + return true; + + string str = obj as string; + if (str == null) + 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)this == (object)value) + { + CheckStringComparison(comparisonType); + return true; + } + + if ((object)value == 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)a == (object)b) + { + return true; + } + + if ((object)a == null || (object)b == null || a.Length != b.Length) + { + return false; + } + + return EqualsHelper(a, b); + } + + public static bool Equals(string a, string b, StringComparison comparisonType) + { + if ((object)a == (object)b) + { + CheckStringComparison(comparisonType); + return true; + } + + if ((object)a == null || (object)b == 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. + public override int GetHashCode() + { +#if MONO + return LegacyStringGetHashCode(); +#else + return Marvin.ComputeHash32(ref Unsafe.As<char, byte>(ref _firstChar), _stringLength * 2, Marvin.DefaultSeed); +#endif + } + + // 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); + + // 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 = (((hash1 << 5) | (hash1 >> 27)) + hash1) ^ ptr[0]; + hash2 = (((hash2 << 5) | (hash2 >> 27)) + 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 = (((hash2 << 5) | (hash2 >> 27)) + 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 ((object)value == null) + { + throw new ArgumentNullException(nameof(value)); + } + return StartsWith(value, StringComparison.CurrentCulture); + } + + public bool StartsWith(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.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<char, byte>(ref this.GetRawStringData()), + ref Unsafe.As<char, byte>(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); + } + } +} |