// Copyright 2013 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. // // This file defines utility functions for working with strings. #ifndef BASE_STRINGS_STRING_UTIL_H_ #define BASE_STRINGS_STRING_UTIL_H_ #include #include // va_list #include #include #include #include #include #include #include #include "base/base_export.h" #include "base/check_op.h" #include "base/compiler_specific.h" #include "base/containers/span.h" #include "base/cxx20_to_address.h" #include "base/strings/string_piece.h" // For implicit conversions. #include "build/build_config.h" namespace base { // C standard-library functions that aren't cross-platform are provided as // "base::...", and their prototypes are listed below. These functions are // then implemented as inline calls to the platform-specific equivalents in the // platform-specific headers. // Wrapper for vsnprintf that always null-terminates and always returns the // number of characters that would be in an untruncated formatted // string, even when truncation occurs. int vsnprintf(char* buffer, size_t size, const char* format, va_list arguments) PRINTF_FORMAT(3, 0); // Some of these implementations need to be inlined. // We separate the declaration from the implementation of this inline // function just so the PRINTF_FORMAT works. inline int snprintf(char* buffer, size_t size, const char* format, ...) PRINTF_FORMAT(3, 4); inline int snprintf(char* buffer, size_t size, const char* format, ...) { va_list arguments; va_start(arguments, format); int result = vsnprintf(buffer, size, format, arguments); va_end(arguments); return result; } // BSD-style safe and consistent string copy functions. // Copies |src| to |dst|, where |dst_size| is the total allocated size of |dst|. // Copies at most |dst_size|-1 characters, and always NULL terminates |dst|, as // long as |dst_size| is not 0. Returns the length of |src| in characters. // If the return value is >= dst_size, then the output was truncated. // NOTE: All sizes are in number of characters, NOT in bytes. BASE_EXPORT size_t strlcpy(char* dst, const char* src, size_t dst_size); BASE_EXPORT size_t wcslcpy(wchar_t* dst, const wchar_t* src, size_t dst_size); // Scan a wprintf format string to determine whether it's portable across a // variety of systems. This function only checks that the conversion // specifiers used by the format string are supported and have the same meaning // on a variety of systems. It doesn't check for other errors that might occur // within a format string. // // Nonportable conversion specifiers for wprintf are: // - 's' and 'c' without an 'l' length modifier. %s and %c operate on char // data on all systems except Windows, which treat them as wchar_t data. // Use %ls and %lc for wchar_t data instead. // - 'S' and 'C', which operate on wchar_t data on all systems except Windows, // which treat them as char data. Use %ls and %lc for wchar_t data // instead. // - 'F', which is not identified by Windows wprintf documentation. // - 'D', 'O', and 'U', which are deprecated and not available on all systems. // Use %ld, %lo, and %lu instead. // // Note that there is no portable conversion specifier for char data when // working with wprintf. // // This function is intended to be called from base::vswprintf. BASE_EXPORT bool IsWprintfFormatPortable(const wchar_t* format); // Simplified implementation of C++20's std::basic_string_view(It, End). // Reference: https://wg21.link/string.view.cons template constexpr BasicStringPiece MakeBasicStringPiece(Iter begin, Iter end) { DCHECK_GE(end - begin, 0); return {base::to_address(begin), static_cast(end - begin)}; } // Explicit instantiations of MakeBasicStringPiece for the BasicStringPiece // aliases defined in base/strings/string_piece_forward.h template constexpr StringPiece MakeStringPiece(Iter begin, Iter end) { return MakeBasicStringPiece(begin, end); } template constexpr StringPiece16 MakeStringPiece16(Iter begin, Iter end) { return MakeBasicStringPiece(begin, end); } template constexpr WStringPiece MakeWStringPiece(Iter begin, Iter end) { return MakeBasicStringPiece(begin, end); } // ASCII-specific tolower. The standard library's tolower is locale sensitive, // so we don't want to use it here. template ::value>> CharT ToLowerASCII(CharT c) { return (c >= 'A' && c <= 'Z') ? (c + ('a' - 'A')) : c; } // ASCII-specific toupper. The standard library's toupper is locale sensitive, // so we don't want to use it here. template ::value>> CharT ToUpperASCII(CharT c) { return (c >= 'a' && c <= 'z') ? static_cast(c + 'A' - 'a') : c; } // Converts the given string to it's ASCII-lowercase equivalent. BASE_EXPORT std::string ToLowerASCII(StringPiece str); BASE_EXPORT std::u16string ToLowerASCII(StringPiece16 str); // Converts the given string to it's ASCII-uppercase equivalent. BASE_EXPORT std::string ToUpperASCII(StringPiece str); BASE_EXPORT std::u16string ToUpperASCII(StringPiece16 str); // Functor for case-insensitive ASCII comparisons for STL algorithms like // std::search. // // Note that a full Unicode version of this functor is not possible to write // because case mappings might change the number of characters, depend on // context (combining accents), and require handling UTF-16. If you need // proper Unicode support, use base::i18n::ToLower/FoldCase and then just // use a normal operator== on the result. template struct CaseInsensitiveCompareASCII { public: bool operator()(Char x, Char y) const { return ToLowerASCII(x) == ToLowerASCII(y); } }; // Like strcasecmp for case-insensitive ASCII characters only. Returns: // -1 (a < b) // 0 (a == b) // 1 (a > b) // (unlike strcasecmp which can return values greater or less than 1/-1). For // full Unicode support, use base::i18n::ToLower or base::i18n::FoldCase // and then just call the normal string operators on the result. BASE_EXPORT int CompareCaseInsensitiveASCII(StringPiece a, StringPiece b); BASE_EXPORT int CompareCaseInsensitiveASCII(StringPiece16 a, StringPiece16 b); namespace internal { template inline bool EqualsCaseInsensitiveASCIIT(BasicStringPiece a, BasicStringPiece b) { return std::equal(a.begin(), a.end(), b.begin(), b.end(), [](auto lhs, auto rhs) { return ToLowerASCII(lhs) == ToLowerASCII(rhs); }); } } // namespace internal // Equality for ASCII case-insensitive comparisons. For full Unicode support, // use base::i18n::ToLower or base::i18n::FoldCase and then compare with either // == or !=. inline bool EqualsCaseInsensitiveASCII(StringPiece a, StringPiece b) { return internal::EqualsCaseInsensitiveASCIIT(a, b); } inline bool EqualsCaseInsensitiveASCII(StringPiece16 a, StringPiece16 b) { return internal::EqualsCaseInsensitiveASCIIT(a, b); } inline bool EqualsCaseInsensitiveASCII(StringPiece16 a, StringPiece b) { return internal::EqualsCaseInsensitiveASCIIT(a, b); } inline bool EqualsCaseInsensitiveASCII(StringPiece a, StringPiece16 b) { return internal::EqualsCaseInsensitiveASCIIT(a, b); } // These threadsafe functions return references to globally unique empty // strings. // // It is likely faster to construct a new empty string object (just a few // instructions to set the length to 0) than to get the empty string instance // returned by these functions (which requires threadsafe static access). // // Therefore, DO NOT USE THESE AS A GENERAL-PURPOSE SUBSTITUTE FOR DEFAULT // CONSTRUCTORS. There is only one case where you should use these: functions // which need to return a string by reference (e.g. as a class member // accessor), and don't have an empty string to use (e.g. in an error case). // These should not be used as initializers, function arguments, or return // values for functions which return by value or outparam. BASE_EXPORT const std::string& EmptyString(); BASE_EXPORT const std::u16string& EmptyString16(); // Contains the set of characters representing whitespace in the corresponding // encoding. Null-terminated. The ASCII versions are the whitespaces as defined // by HTML5, and don't include control characters. BASE_EXPORT extern const wchar_t kWhitespaceWide[]; // Includes Unicode. BASE_EXPORT extern const char16_t kWhitespaceUTF16[]; // Includes Unicode. BASE_EXPORT extern const char16_t kWhitespaceNoCrLfUTF16[]; // Unicode w/o CR/LF. BASE_EXPORT extern const char kWhitespaceASCII[]; BASE_EXPORT extern const char16_t kWhitespaceASCIIAs16[]; // No unicode. // Null-terminated string representing the UTF-8 byte order mark. BASE_EXPORT extern const char kUtf8ByteOrderMark[]; // Removes characters in |remove_chars| from anywhere in |input|. Returns true // if any characters were removed. |remove_chars| must be null-terminated. // NOTE: Safe to use the same variable for both |input| and |output|. BASE_EXPORT bool RemoveChars(StringPiece16 input, StringPiece16 remove_chars, std::u16string* output); BASE_EXPORT bool RemoveChars(StringPiece input, StringPiece remove_chars, std::string* output); // Replaces characters in |replace_chars| from anywhere in |input| with // |replace_with|. Each character in |replace_chars| will be replaced with // the |replace_with| string. Returns true if any characters were replaced. // |replace_chars| must be null-terminated. // NOTE: Safe to use the same variable for both |input| and |output|. BASE_EXPORT bool ReplaceChars(StringPiece16 input, StringPiece16 replace_chars, StringPiece16 replace_with, std::u16string* output); BASE_EXPORT bool ReplaceChars(StringPiece input, StringPiece replace_chars, StringPiece replace_with, std::string* output); enum TrimPositions { TRIM_NONE = 0, TRIM_LEADING = 1 << 0, TRIM_TRAILING = 1 << 1, TRIM_ALL = TRIM_LEADING | TRIM_TRAILING, }; // Removes characters in |trim_chars| from the beginning and end of |input|. // The 8-bit version only works on 8-bit characters, not UTF-8. Returns true if // any characters were removed. // // It is safe to use the same variable for both |input| and |output| (this is // the normal usage to trim in-place). BASE_EXPORT bool TrimString(StringPiece16 input, StringPiece16 trim_chars, std::u16string* output); BASE_EXPORT bool TrimString(StringPiece input, StringPiece trim_chars, std::string* output); // StringPiece versions of the above. The returned pieces refer to the original // buffer. BASE_EXPORT StringPiece16 TrimString(StringPiece16 input, StringPiece16 trim_chars, TrimPositions positions); BASE_EXPORT StringPiece TrimString(StringPiece input, StringPiece trim_chars, TrimPositions positions); // Truncates a string to the nearest UTF-8 character that will leave // the string less than or equal to the specified byte size. BASE_EXPORT void TruncateUTF8ToByteSize(const std::string& input, const size_t byte_size, std::string* output); // Trims any whitespace from either end of the input string. // // The StringPiece versions return a substring referencing the input buffer. // The ASCII versions look only for ASCII whitespace. // // The std::string versions return where whitespace was found. // NOTE: Safe to use the same variable for both input and output. BASE_EXPORT TrimPositions TrimWhitespace(StringPiece16 input, TrimPositions positions, std::u16string* output); BASE_EXPORT StringPiece16 TrimWhitespace(StringPiece16 input, TrimPositions positions); BASE_EXPORT TrimPositions TrimWhitespaceASCII(StringPiece input, TrimPositions positions, std::string* output); BASE_EXPORT StringPiece TrimWhitespaceASCII(StringPiece input, TrimPositions positions); // Searches for CR or LF characters. Removes all contiguous whitespace // strings that contain them. This is useful when trying to deal with text // copied from terminals. // Returns |text|, with the following three transformations: // (1) Leading and trailing whitespace is trimmed. // (2) If |trim_sequences_with_line_breaks| is true, any other whitespace // sequences containing a CR or LF are trimmed. // (3) All other whitespace sequences are converted to single spaces. BASE_EXPORT std::u16string CollapseWhitespace( StringPiece16 text, bool trim_sequences_with_line_breaks); BASE_EXPORT std::string CollapseWhitespaceASCII( StringPiece text, bool trim_sequences_with_line_breaks); // Returns true if |input| is empty or contains only characters found in // |characters|. BASE_EXPORT bool ContainsOnlyChars(StringPiece input, StringPiece characters); BASE_EXPORT bool ContainsOnlyChars(StringPiece16 input, StringPiece16 characters); // Returns true if |str| is structurally valid UTF-8 and also doesn't // contain any non-character code point (e.g. U+10FFFE). Prohibiting // non-characters increases the likelihood of detecting non-UTF-8 in // real-world text, for callers which do not need to accept // non-characters in strings. BASE_EXPORT bool IsStringUTF8(StringPiece str); // Returns true if |str| contains valid UTF-8, allowing non-character // code points. BASE_EXPORT bool IsStringUTF8AllowingNoncharacters(StringPiece str); // Returns true if |str| contains only valid ASCII character values. // Note 1: IsStringASCII executes in time determined solely by the // length of the string, not by its contents, so it is robust against // timing attacks for all strings of equal length. // Note 2: IsStringASCII assumes the input is likely all ASCII, and // does not leave early if it is not the case. BASE_EXPORT bool IsStringASCII(StringPiece str); BASE_EXPORT bool IsStringASCII(StringPiece16 str); #if defined(WCHAR_T_IS_UTF32) BASE_EXPORT bool IsStringASCII(WStringPiece str); #endif // Performs a case-sensitive string compare of the given 16-bit string against // the given 8-bit ASCII string (typically a constant). The behavior is // undefined if the |ascii| string is not ASCII. BASE_EXPORT bool EqualsASCII(StringPiece16 str, StringPiece ascii); // Indicates case sensitivity of comparisons. Only ASCII case insensitivity // is supported. Full Unicode case-insensitive conversions would need to go in // base/i18n so it can use ICU. // // If you need to do Unicode-aware case-insensitive StartsWith/EndsWith, it's // best to call base::i18n::ToLower() or base::i18n::FoldCase() (see // base/i18n/case_conversion.h for usage advice) on the arguments, and then use // the results to a case-sensitive comparison. enum class CompareCase { SENSITIVE, INSENSITIVE_ASCII, }; BASE_EXPORT bool StartsWith( StringPiece str, StringPiece search_for, CompareCase case_sensitivity = CompareCase::SENSITIVE); BASE_EXPORT bool StartsWith( StringPiece16 str, StringPiece16 search_for, CompareCase case_sensitivity = CompareCase::SENSITIVE); BASE_EXPORT bool EndsWith( StringPiece str, StringPiece search_for, CompareCase case_sensitivity = CompareCase::SENSITIVE); BASE_EXPORT bool EndsWith( StringPiece16 str, StringPiece16 search_for, CompareCase case_sensitivity = CompareCase::SENSITIVE); // Determines the type of ASCII character, independent of locale (the C // library versions will change based on locale). template inline bool IsAsciiWhitespace(Char c) { return c == ' ' || c == '\r' || c == '\n' || c == '\t' || c == '\f'; } template inline bool IsAsciiAlpha(Char c) { return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z'); } template inline bool IsAsciiUpper(Char c) { return c >= 'A' && c <= 'Z'; } template inline bool IsAsciiLower(Char c) { return c >= 'a' && c <= 'z'; } template inline bool IsAsciiDigit(Char c) { return c >= '0' && c <= '9'; } template inline bool IsAsciiAlphaNumeric(Char c) { return IsAsciiAlpha(c) || IsAsciiDigit(c); } template inline bool IsAsciiPrintable(Char c) { return c >= ' ' && c <= '~'; } template inline bool IsHexDigit(Char c) { return (c >= '0' && c <= '9') || (c >= 'A' && c <= 'F') || (c >= 'a' && c <= 'f'); } // Returns the integer corresponding to the given hex character. For example: // '4' -> 4 // 'a' -> 10 // 'B' -> 11 // Assumes the input is a valid hex character. BASE_EXPORT char HexDigitToInt(char c); inline char HexDigitToInt(char16_t c) { DCHECK(IsHexDigit(c)); return HexDigitToInt(static_cast(c)); } // Returns true if it's a Unicode whitespace character. template inline bool IsUnicodeWhitespace(Char c) { // kWhitespaceWide is a NUL-terminated string for (const auto* cur = kWhitespaceWide; *cur; ++cur) { if (static_cast>(*cur) == static_cast>(c)) return true; } return false; }; // Return a byte string in human-readable format with a unit suffix. Not // appropriate for use in any UI; use of FormatBytes and friends in ui/base is // highly recommended instead. TODO(avi): Figure out how to get callers to use // FormatBytes instead; remove this. BASE_EXPORT std::u16string FormatBytesUnlocalized(int64_t bytes); // Starting at |start_offset| (usually 0), replace the first instance of // |find_this| with |replace_with|. BASE_EXPORT void ReplaceFirstSubstringAfterOffset(std::u16string* str, size_t start_offset, StringPiece16 find_this, StringPiece16 replace_with); BASE_EXPORT void ReplaceFirstSubstringAfterOffset( std::string* str, size_t start_offset, StringPiece find_this, StringPiece replace_with); // Starting at |start_offset| (usually 0), look through |str| and replace all // instances of |find_this| with |replace_with|. // // This does entire substrings; use std::replace in for single // characters, for example: // std::replace(str.begin(), str.end(), 'a', 'b'); BASE_EXPORT void ReplaceSubstringsAfterOffset(std::u16string* str, size_t start_offset, StringPiece16 find_this, StringPiece16 replace_with); BASE_EXPORT void ReplaceSubstringsAfterOffset( std::string* str, size_t start_offset, StringPiece find_this, StringPiece replace_with); // Reserves enough memory in |str| to accommodate |length_with_null| characters, // sets the size of |str| to |length_with_null - 1| characters, and returns a // pointer to the underlying contiguous array of characters. This is typically // used when calling a function that writes results into a character array, but // the caller wants the data to be managed by a string-like object. It is // convenient in that is can be used inline in the call, and fast in that it // avoids copying the results of the call from a char* into a string. // // Internally, this takes linear time because the resize() call 0-fills the // underlying array for potentially all // (|length_with_null - 1| * sizeof(string_type::value_type)) bytes. Ideally we // could avoid this aspect of the resize() call, as we expect the caller to // immediately write over this memory, but there is no other way to set the size // of the string, and not doing that will mean people who access |str| rather // than str.c_str() will get back a string of whatever size |str| had on entry // to this function (probably 0). BASE_EXPORT char* WriteInto(std::string* str, size_t length_with_null); BASE_EXPORT char16_t* WriteInto(std::u16string* str, size_t length_with_null); // Joins a list of strings into a single string, inserting |separator| (which // may be empty) in between all elements. // // Note this is inverse of SplitString()/SplitStringPiece() defined in // string_split.h. // // If possible, callers should build a vector of StringPieces and use the // StringPiece variant, so that they do not create unnecessary copies of // strings. For example, instead of using SplitString, modifying the vector, // then using JoinString, use SplitStringPiece followed by JoinString so that no // copies of those strings are created until the final join operation. // // Use StrCat (in base/strings/strcat.h) if you don't need a separator. BASE_EXPORT std::string JoinString(span parts, StringPiece separator); BASE_EXPORT std::u16string JoinString(span parts, StringPiece16 separator); BASE_EXPORT std::string JoinString(span parts, StringPiece separator); BASE_EXPORT std::u16string JoinString(span parts, StringPiece16 separator); // Explicit initializer_list overloads are required to break ambiguity when used // with a literal initializer list (otherwise the compiler would not be able to // decide between the string and StringPiece overloads). BASE_EXPORT std::string JoinString(std::initializer_list parts, StringPiece separator); BASE_EXPORT std::u16string JoinString( std::initializer_list parts, StringPiece16 separator); // Replace $1-$2-$3..$9 in the format string with values from |subst|. // Additionally, any number of consecutive '$' characters is replaced by that // number less one. Eg $$->$, $$$->$$, etc. The offsets parameter here can be // NULL. This only allows you to use up to nine replacements. BASE_EXPORT std::u16string ReplaceStringPlaceholders( StringPiece16 format_string, const std::vector& subst, std::vector* offsets); BASE_EXPORT std::string ReplaceStringPlaceholders( StringPiece format_string, const std::vector& subst, std::vector* offsets); // Single-string shortcut for ReplaceStringHolders. |offset| may be NULL. BASE_EXPORT std::u16string ReplaceStringPlaceholders( const std::u16string& format_string, const std::u16string& a, size_t* offset); } // namespace base #if BUILDFLAG(IS_WIN) #include "base/strings/string_util_win.h" #elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) #include "base/strings/string_util_posix.h" #else #error Define string operations appropriately for your platform #endif #endif // BASE_STRINGS_STRING_UTIL_H_