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| -rw-r--r-- | xpcom/string/nsTStringRepr.h | 546 |
1 files changed, 546 insertions, 0 deletions
diff --git a/xpcom/string/nsTStringRepr.h b/xpcom/string/nsTStringRepr.h new file mode 100644 index 0000000000..7e7fa53384 --- /dev/null +++ b/xpcom/string/nsTStringRepr.h @@ -0,0 +1,546 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim: set ts=8 sts=2 et sw=2 tw=80: */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#ifndef nsTStringRepr_h +#define nsTStringRepr_h + +#include <limits> +#include <string_view> +#include <type_traits> // std::enable_if + +#include "mozilla/Char16.h" +#include "mozilla/CheckedInt.h" +#include "mozilla/fallible.h" +#include "nsStringBuffer.h" +#include "nsStringFlags.h" +#include "nsStringFwd.h" +#include "nsStringIterator.h" +#include "nsCharTraits.h" + +template <typename T> +class nsTSubstringTuple; + +namespace mozilla { + +// This is mainly intended to be used in the context of nsTStrings where +// we want to enable a specific function only for a given character class. In +// order for this technique to work the member function needs to be templated +// on something other than `T`. We keep this in the `mozilla` namespace rather +// than `nsTStringRepr` as it's intentionally not dependent on `T`. +// +// The 'T' at the end of `Char[16]OnlyT` is refering to the `::type` portion +// which will only be defined if the character class is correct. This is similar +// to `std::enable_if_t` which is available in C++14, but not C++11. +// +// `CharType` is generally going to be a shadowed type of `T`. +// +// Example usage of a function that will only be defined if `T` == `char`: +// +// template <typename T> +// class nsTSubstring : public nsTStringRepr<T> { +// template <typename Q = T, typename EnableForChar = typename CharOnlyT<Q>> +// int Foo() { return 42; } +// }; +// +// Please note that we had to use a separate type `Q` for this to work. You +// will get a semi-decent compiler error if you use `T` directly. + +template <typename CharType> +using CharOnlyT = + typename std::enable_if<std::is_same<char, CharType>::value>::type; + +template <typename CharType> +using Char16OnlyT = + typename std::enable_if<std::is_same<char16_t, CharType>::value>::type; + +namespace detail { + +// nsTStringLengthStorage is a helper class which holds the string's length and +// provides getters and setters for converting to and from `size_t`. This is +// done to allow the length to be stored in a `uint32_t` using assertions. +template <typename T> +class nsTStringLengthStorage { + public: + // The maximum byte capacity for a `nsTString` must fit within an `int32_t`, + // with enough room for a trailing null, as consumers often cast `Length()` + // and `Capacity()` to smaller types like `int32_t`. + static constexpr size_t kMax = + size_t{std::numeric_limits<int32_t>::max()} / sizeof(T) - 1; + static_assert( + (kMax + 1) * sizeof(T) <= std::numeric_limits<int32_t>::max(), + "nsTString's maximum length, including the trailing null, must fit " + "within `int32_t`, as callers will cast to `int32_t` occasionally"); + static_assert(((CheckedInt<uint32_t>{kMax} + 1) * sizeof(T) + + sizeof(nsStringBuffer)) + .isValid(), + "Math required to allocate a nsStringBuffer for a " + "maximum-capacity string must not overflow uint32_t"); + + // Implicit conversion and assignment from `size_t` which assert that the + // value is in-range. + MOZ_IMPLICIT constexpr nsTStringLengthStorage(size_t aLength) + : mLength(static_cast<uint32_t>(aLength)) { + MOZ_RELEASE_ASSERT(aLength <= kMax, "string is too large"); + } + constexpr nsTStringLengthStorage& operator=(size_t aLength) { + MOZ_RELEASE_ASSERT(aLength <= kMax, "string is too large"); + mLength = static_cast<uint32_t>(aLength); + return *this; + } + MOZ_IMPLICIT constexpr operator size_t() const { return mLength; } + + private: + uint32_t mLength = 0; +}; + +// nsTStringRepr defines a string's memory layout and some accessor methods. +// This class exists so that nsTLiteralString can avoid inheriting +// nsTSubstring's destructor. All methods on this class must be const because +// literal strings are not writable. +// +// This class is an implementation detail and should not be instantiated +// directly, nor used in any way outside of the string code itself. It is +// buried in a namespace to discourage its use in function parameters. +// If you need to take a parameter, use [const] ns[C]Substring&. +// If you need to instantiate a string, use ns[C]String or descendents. +// +// NAMES: +// nsStringRepr for wide characters +// nsCStringRepr for narrow characters +template <typename T> +class nsTStringRepr { + public: + typedef mozilla::fallible_t fallible_t; + + typedef T char_type; + + typedef nsCharTraits<char_type> char_traits; + typedef typename char_traits::incompatible_char_type incompatible_char_type; + + typedef nsTStringRepr<T> self_type; + typedef self_type base_string_type; + + typedef nsTSubstring<T> substring_type; + typedef nsTSubstringTuple<T> substring_tuple_type; + + typedef nsReadingIterator<char_type> const_iterator; + typedef char_type* iterator; + + typedef nsTStringComparator<char_type> comparator_type; + + typedef const char_type* const_char_iterator; + + typedef std::basic_string_view<char_type> string_view; + + typedef size_t index_type; + typedef size_t size_type; + + // These are only for internal use within the string classes: + typedef StringDataFlags DataFlags; + typedef StringClassFlags ClassFlags; + typedef nsTStringLengthStorage<T> LengthStorage; + + // Reading iterators. + constexpr const_char_iterator BeginReading() const { return mData; } + constexpr const_char_iterator EndReading() const { return mData + mLength; } + + // Deprecated reading iterators. + const_iterator& BeginReading(const_iterator& aIter) const { + aIter.mStart = mData; + aIter.mEnd = mData + mLength; + aIter.mPosition = aIter.mStart; + return aIter; + } + + const_iterator& EndReading(const_iterator& aIter) const { + aIter.mStart = mData; + aIter.mEnd = mData + mLength; + aIter.mPosition = aIter.mEnd; + return aIter; + } + + const_char_iterator& BeginReading(const_char_iterator& aIter) const { + return aIter = mData; + } + + const_char_iterator& EndReading(const_char_iterator& aIter) const { + return aIter = mData + mLength; + } + + // Accessors. + template <typename U, typename Dummy> + struct raw_type { + typedef const U* type; + }; +#if defined(MOZ_USE_CHAR16_WRAPPER) + template <typename Dummy> + struct raw_type<char16_t, Dummy> { + typedef char16ptr_t type; + }; +#endif + + // Returns pointer to string data (not necessarily null-terminated) + constexpr typename raw_type<T, int>::type Data() const { return mData; } + + constexpr size_type Length() const { return static_cast<size_type>(mLength); } + + constexpr string_view View() const { return string_view(Data(), Length()); } + + constexpr operator string_view() const { return View(); } + + constexpr DataFlags GetDataFlags() const { return mDataFlags; } + + constexpr bool IsEmpty() const { return mLength == 0; } + + constexpr bool IsLiteral() const { + return !!(mDataFlags & DataFlags::LITERAL); + } + + constexpr bool IsVoid() const { return !!(mDataFlags & DataFlags::VOIDED); } + + constexpr bool IsTerminated() const { + return !!(mDataFlags & DataFlags::TERMINATED); + } + + constexpr char_type CharAt(index_type aIndex) const { + NS_ASSERTION(aIndex < Length(), "index exceeds allowable range"); + return mData[aIndex]; + } + + constexpr char_type operator[](index_type aIndex) const { + return CharAt(aIndex); + } + + char_type First() const; + + char_type Last() const; + + // Equality. + bool NS_FASTCALL Equals(const self_type&) const; + bool NS_FASTCALL Equals(const self_type&, comparator_type) const; + + bool NS_FASTCALL Equals(const substring_tuple_type& aTuple) const; + bool NS_FASTCALL Equals(const substring_tuple_type& aTuple, + comparator_type) const; + + bool NS_FASTCALL Equals(const char_type* aData) const; + bool NS_FASTCALL Equals(const char_type* aData, comparator_type) const; + + /** + * Compare this string and another ASCII-case-insensitively. + * + * This method is similar to `LowerCaseEqualsASCII` however both strings are + * lowercased, meaning that `aString` need not be all lowercase. + * + * @param aString is the string to check + * @return boolean + */ + bool EqualsIgnoreCase(const std::string_view& aString) const; + +#if defined(MOZ_USE_CHAR16_WRAPPER) + template <typename Q = T, typename EnableIfChar16 = Char16OnlyT<Q>> + bool NS_FASTCALL Equals(char16ptr_t aData) const { + return Equals(static_cast<const char16_t*>(aData)); + } + template <typename Q = T, typename EnableIfChar16 = Char16OnlyT<Q>> + bool NS_FASTCALL Equals(char16ptr_t aData, comparator_type aComp) const { + return Equals(static_cast<const char16_t*>(aData), aComp); + } +#endif + + // An efficient comparison with ASCII that can be used even + // for wide strings. Call this version when you know the + // length of 'data'. + bool NS_FASTCALL EqualsASCII(const char* aData, size_type aLen) const; + // An efficient comparison with ASCII that can be used even + // for wide strings. Call this version when 'data' is + // null-terminated. + bool NS_FASTCALL EqualsASCII(const char* aData) const; + + // An efficient comparison with Latin1 characters that can be used even for + // wide strings. + bool EqualsLatin1(const char* aData, size_type aLength) const; + + // EqualsLiteral must ONLY be called with an actual literal string, or + // a char array *constant* declared without an explicit size and with an + // initializer that is a string literal or is otherwise null-terminated. + // Use EqualsASCII for other char array variables. + // (Although this method may happen to produce expected results for other + // char arrays that have bound one greater than the sequence of interest, + // such use is discouraged for reasons of readability and maintainability.) + // The template trick to acquire the array bound at compile time without + // using a macro is due to Corey Kosak, with much thanks. + template <int N> + inline bool EqualsLiteral(const char (&aStr)[N]) const { + return EqualsASCII(aStr, N - 1); + } + + // EqualsLiteral must ONLY be called with an actual literal string, or + // a char array *constant* declared without an explicit size and with an + // initializer that is a string literal or is otherwise null-terminated. + // Use EqualsASCII for other char array variables. + // (Although this method may happen to produce expected results for other + // char arrays that have bound one greater than the sequence of interest, + // such use is discouraged for reasons of readability and maintainability.) + // The template trick to acquire the array bound at compile time without + // using a macro is due to Corey Kosak, with much thanks. + template <size_t N, typename = std::enable_if_t<!std::is_same_v< + const char (&)[N], const char_type (&)[N]>>> + inline bool EqualsLiteral(const char_type (&aStr)[N]) const { + return *this == nsTLiteralString<char_type>(aStr); + } + + // The LowerCaseEquals methods compare the ASCII-lowercase version of + // this string (lowercasing only ASCII uppercase characters) to some + // ASCII/Literal string. The ASCII string is *not* lowercased for + // you. If you compare to an ASCII or literal string that contains an + // uppercase character, it is guaranteed to return false. We will + // throw assertions too. + bool NS_FASTCALL LowerCaseEqualsASCII(const char* aData, + size_type aLen) const; + bool NS_FASTCALL LowerCaseEqualsASCII(const char* aData) const; + + // LowerCaseEqualsLiteral must ONLY be called with an actual literal string, + // or a char array *constant* declared without an explicit size and with an + // initializer that is a string literal or is otherwise null-terminated. + // Use LowerCaseEqualsASCII for other char array variables. + // (Although this method may happen to produce expected results for other + // char arrays that have bound one greater than the sequence of interest, + // such use is discouraged for reasons of readability and maintainability.) + template <int N> + bool LowerCaseEqualsLiteral(const char (&aStr)[N]) const { + return LowerCaseEqualsASCII(aStr, N - 1); + } + + // Returns true if this string overlaps with the given string fragment. + bool IsDependentOn(const char_type* aStart, const char_type* aEnd) const { + // If it _isn't_ the case that one fragment starts after the other ends, + // or ends before the other starts, then, they conflict: + // + // !(f2.begin >= f1.aEnd || f2.aEnd <= f1.begin) + // + // Simplified, that gives us (To avoid relying on Undefined Behavior + // from comparing pointers from different allocations (which in + // principle gives the optimizer the permission to assume elsewhere + // that the pointers are from the same allocation), the comparisons + // are done on integers, which merely relies on implementation-defined + // behavior of converting pointers to integers. std::less and + // std::greater implementations don't actually provide the guarantees + // that they should.): + return (reinterpret_cast<uintptr_t>(aStart) < + reinterpret_cast<uintptr_t>(mData + mLength) && + reinterpret_cast<uintptr_t>(aEnd) > + reinterpret_cast<uintptr_t>(mData)); + } + + /** + * Search for the given substring within this string. + * + * @param aString is substring to be sought in this + * @param aOffset tells us where in this string to start searching + * @return offset in string, or kNotFound + */ + int32_t Find(const string_view& aString, index_type aOffset = 0) const; + + // Previously there was an overload of `Find()` which took a bool second + // argument. Avoid issues by explicitly preventing that overload. + // TODO: Remove this at some point. + template <typename I, + typename = std::enable_if_t<!std::is_same_v<I, index_type> && + std::is_convertible_v<I, index_type>>> + int32_t Find(const string_view& aString, I aOffset) const { + static_assert(!std::is_same_v<I, bool>, "offset must not be `bool`"); + return Find(aString, static_cast<index_type>(aOffset)); + } + + /** + * Search for the given ASCII substring within this string, ignoring case. + * + * @param aString is substring to be sought in this + * @param aOffset tells us where in this string to start searching + * @return offset in string, or kNotFound + */ + int32_t LowerCaseFindASCII(const std::string_view& aString, + index_type aOffset = 0) const; + + /** + * Scan the string backwards, looking for the given substring. + * + * @param aString is substring to be sought in this + * @return offset in string, or kNotFound + */ + int32_t RFind(const string_view& aString) const; + + size_type CountChar(char_type) const; + + bool Contains(char_type aChar) const { return FindChar(aChar) != kNotFound; } + + /** + * Search for the first instance of a given char within this string + * + * @param aChar is the character to search for + * @param aOffset tells us where in this string to start searching + * @return offset in string, or kNotFound + */ + int32_t FindChar(char_type aChar, index_type aOffset = 0) const; + + /** + * Search for the last instance of a given char within this string + * + * @param aChar is the character to search for + * @param aOffset tells us where in this string to start searching + * @return offset in string, or kNotFound + */ + int32_t RFindChar(char_type aChar, int32_t aOffset = -1) const; + + /** + * This method searches this string for the first character found in + * the given string. + * + * @param aSet contains set of chars to be found + * @param aOffset tells us where in this string to start searching + * (counting from left) + * @return offset in string, or kNotFound + */ + + int32_t FindCharInSet(const string_view& aSet, index_type aOffset = 0) const; + + /** + * This method searches this string for the last character found in + * the given string. + * + * @param aSet contains set of chars to be found + * @param aOffset tells us where in this string to start searching + * (counting from left) + * @return offset in string, or kNotFound + */ + + int32_t RFindCharInSet(const string_view& aSet, int32_t aOffset = -1) const; + + /** + * Perform locale-independent string to double-precision float conversion. + * + * Leading spaces in the string will be ignored. The returned value will be + * finite unless aErrorCode is set to a failed status. + * + * @param aErrorCode will contain error if one occurs + * @return double-precision float rep of string value + */ + double ToDouble(nsresult* aErrorCode) const; + + /** + * Perform locale-independent string to single-precision float conversion. + * + * Leading spaces in the string will be ignored. The returned value will be + * finite unless aErrorCode is set to a failed status. + * + * @param aErrorCode will contain error if one occurs + * @return single-precision float rep of string value + */ + float ToFloat(nsresult* aErrorCode) const; + + /** + * Similar to above ToDouble and ToFloat but allows trailing characters that + * are not converted. + */ + double ToDoubleAllowTrailingChars(nsresult* aErrorCode) const; + float ToFloatAllowTrailingChars(nsresult* aErrorCode) const; + + protected: + nsTStringRepr() = delete; // Never instantiate directly + + constexpr nsTStringRepr(char_type* aData, size_type aLength, + DataFlags aDataFlags, ClassFlags aClassFlags) + : mData(aData), + mLength(aLength), + mDataFlags(aDataFlags), + mClassFlags(aClassFlags) {} + + static constexpr size_type kMaxCapacity = LengthStorage::kMax; + + /** + * Checks if the given capacity is valid for this string type. + */ + [[nodiscard]] static constexpr bool CheckCapacity(size_type aCapacity) { + return aCapacity <= kMaxCapacity; + } + + char_type* mData; + LengthStorage mLength; + DataFlags mDataFlags; + ClassFlags const mClassFlags; +}; + +extern template class nsTStringRepr<char>; +extern template class nsTStringRepr<char16_t>; + +} // namespace detail +} // namespace mozilla + +template <typename T> +int NS_FASTCALL Compare(const mozilla::detail::nsTStringRepr<T>& aLhs, + const mozilla::detail::nsTStringRepr<T>& aRhs, + nsTStringComparator<T> = nsTDefaultStringComparator<T>); + +extern template int NS_FASTCALL Compare<char>( + const mozilla::detail::nsTStringRepr<char>&, + const mozilla::detail::nsTStringRepr<char>&, nsTStringComparator<char>); + +extern template int NS_FASTCALL +Compare<char16_t>(const mozilla::detail::nsTStringRepr<char16_t>&, + const mozilla::detail::nsTStringRepr<char16_t>&, + nsTStringComparator<char16_t>); + +template <typename T> +inline constexpr bool operator!=( + const mozilla::detail::nsTStringRepr<T>& aLhs, + const mozilla::detail::nsTStringRepr<T>& aRhs) { + return !aLhs.Equals(aRhs); +} + +template <typename T> +inline constexpr bool operator!=(const mozilla::detail::nsTStringRepr<T>& aLhs, + const T* aRhs) { + return !aLhs.Equals(aRhs); +} + +template <typename T> +inline bool operator<(const mozilla::detail::nsTStringRepr<T>& aLhs, + const mozilla::detail::nsTStringRepr<T>& aRhs) { + return Compare(aLhs, aRhs) < 0; +} + +template <typename T> +inline bool operator<=(const mozilla::detail::nsTStringRepr<T>& aLhs, + const mozilla::detail::nsTStringRepr<T>& aRhs) { + return Compare(aLhs, aRhs) <= 0; +} + +template <typename T> +inline bool operator==(const mozilla::detail::nsTStringRepr<T>& aLhs, + const mozilla::detail::nsTStringRepr<T>& aRhs) { + return aLhs.Equals(aRhs); +} + +template <typename T> +inline bool operator==(const mozilla::detail::nsTStringRepr<T>& aLhs, + const T* aRhs) { + return aLhs.Equals(aRhs); +} + +template <typename T> +inline bool operator>=(const mozilla::detail::nsTStringRepr<T>& aLhs, + const mozilla::detail::nsTStringRepr<T>& aRhs) { + return Compare(aLhs, aRhs) >= 0; +} + +template <typename T> +inline bool operator>(const mozilla::detail::nsTStringRepr<T>& aLhs, + const mozilla::detail::nsTStringRepr<T>& aRhs) { + return Compare(aLhs, aRhs) > 0; +} + +#endif |