text: // 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 <ctype.h>
  #include <stdarg.h>   // va_list
  #include <stddef.h>
  #include <stdint.h>
  
  #include <initializer_list>
  #include <string>
  #include <vector>
  
  #include "base/base_export.h"
  #include "base/compiler_specific.h"
  #include "base/strings/string16.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,
                      _Printf_format_string_ const char* format,
                      ...) PRINTF_FORMAT(3, 4);
  inline int snprintf(char* buffer,
                      size_t size,
                      _Printf_format_string_ 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);
  
  // ASCII-specific tolower.  The standard library's tolower is locale sensitive,
  // so we don't want to use it here.
  inline char ToLowerASCII(char c) {
    return (c >= 'A' && c <= 'Z') ? (c + ('a' - 'A')) : c;
  }
  inline char16 ToLowerASCII(char16 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.
  inline char ToUpperASCII(char c) {
    return (c >= 'a' && c <= 'z') ? (c + ('A' - 'a')) : c;
  }
  inline char16 ToUpperASCII(char16 c) {
    return (c >= 'a' && c <= 'z') ? (c + ('A' - 'a')) : c;
  }
  
  // Converts the given string to it's ASCII-lowercase equivalent.
  BASE_EXPORT std::string ToLowerASCII(StringPiece str);
  BASE_EXPORT string16 ToLowerASCII(StringPiece16 str);
  
  // Converts the given string to it's ASCII-uppercase equivalent.
  BASE_EXPORT std::string ToUpperASCII(StringPiece str);
  BASE_EXPORT string16 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<typename Char> 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::i18h::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);
  
  // Equality for ASCII case-insensitive comparisons. For full Unicode support,
  // use base::i18n::ToLower or base::i18h::FoldCase and then compare with either
  // == or !=.
  BASE_EXPORT bool EqualsCaseInsensitiveASCII(StringPiece a, StringPiece b);
  BASE_EXPORT bool EqualsCaseInsensitiveASCII(StringPiece16 a, StringPiece16 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 singleton
  // returned by these functions (which requires threadsafe singleton 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 string16& 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 kWhitespaceUTF16[];  // Includes Unicode.
  BASE_EXPORT extern const char kWhitespaceASCII[];
  BASE_EXPORT extern const char16 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(const string16& input,
                               const StringPiece16& remove_chars,
                               string16* output);
  BASE_EXPORT bool RemoveChars(const std::string& input,
                               const 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(const string16& input,
                                const StringPiece16& replace_chars,
                                const string16& replace_with,
                                string16* output);
  BASE_EXPORT bool ReplaceChars(const std::string& input,
                                const StringPiece& replace_chars,
                                const std::string& 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.
  //
  // 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(const string16& input,
                              StringPiece16 trim_chars,
                              string16* output);
  BASE_EXPORT bool TrimString(const std::string& 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,
                                       const StringPiece16& trim_chars,
                                       TrimPositions positions);
  BASE_EXPORT StringPiece TrimString(StringPiece input,
                                     const 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(const string16& input,
                                           TrimPositions positions,
                                           string16* output);
  BASE_EXPORT StringPiece16 TrimWhitespace(StringPiece16 input,
                                           TrimPositions positions);
  BASE_EXPORT TrimPositions TrimWhitespaceASCII(const std::string& 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 string16 CollapseWhitespace(
      const string16& text,
      bool trim_sequences_with_line_breaks);
  BASE_EXPORT std::string CollapseWhitespaceASCII(
      const std::string& text,
      bool trim_sequences_with_line_breaks);
  
  // Returns true if |input| is empty or contains only characters found in
  // |characters|.
  BASE_EXPORT bool ContainsOnlyChars(const StringPiece& input,
                                     const StringPiece& characters);
  BASE_EXPORT bool ContainsOnlyChars(const StringPiece16& input,
                                     const StringPiece16& characters);
  
  // Returns true if the specified string matches the criteria. How can a wide
  // string be 8-bit or UTF8? It contains only characters that are < 256 (in the
  // first case) or characters that use only 8-bits and whose 8-bit
  // representation looks like a UTF-8 string (the second case).
  //
  // Note that IsStringUTF8 checks not only if the input is structurally
  // valid but also if it doesn't contain any non-character codepoint
  // (e.g. U+FFFE). It's done on purpose because all the existing callers want
  // to have the maximum 'discriminating' power from other encodings. If
  // there's a use case for just checking the structural validity, we have to
  // add a new function for that.
  //
  // IsStringASCII assumes the input is likely all ASCII, and does not leave early
  // if it is not the case.
  BASE_EXPORT bool IsStringUTF8(const StringPiece& str);
  BASE_EXPORT bool IsStringASCII(const StringPiece& str);
  BASE_EXPORT bool IsStringASCII(const StringPiece16& str);
  BASE_EXPORT bool IsStringASCII(const string16& str);
  #if defined(WCHAR_T_IS_UTF32)
  BASE_EXPORT bool IsStringASCII(const std::wstring& str);
  #endif
  
  // Compare the lower-case form of the given string against the given
  // previously-lower-cased ASCII string (typically a constant).
  BASE_EXPORT bool LowerCaseEqualsASCII(StringPiece str,
                                        StringPiece lowecase_ascii);
  BASE_EXPORT bool LowerCaseEqualsASCII(StringPiece16 str,
                                        StringPiece lowecase_ascii);
  
  // 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);
  BASE_EXPORT bool StartsWith(StringPiece16 str,
                              StringPiece16 search_for,
                              CompareCase case_sensitivity);
  BASE_EXPORT bool EndsWith(StringPiece str,
                            StringPiece search_for,
                            CompareCase case_sensitivity);
  BASE_EXPORT bool EndsWith(StringPiece16 str,
                            StringPiece16 search_for,
                            CompareCase case_sensitivity);
  
  // Determines the type of ASCII character, independent of locale (the C
  // library versions will change based on locale).
  template <typename Char>
  inline bool IsAsciiWhitespace(Char c) {
    return c == ' ' || c == '\r' || c == '\n' || c == '\t';
  }
  template <typename Char>
  inline bool IsAsciiAlpha(Char c) {
    return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z');
  }
  template <typename Char>
  inline bool IsAsciiUpper(Char c) {
    return c >= 'A' && c <= 'Z';
  }
  template <typename Char>
  inline bool IsAsciiLower(Char c) {
    return c >= 'a' && c <= 'z';
  }
  template <typename Char>
  inline bool IsAsciiDigit(Char c) {
    return c >= '0' && c <= '9';
  }
  
  template <typename Char>
  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. DCHECKs in debug builds if not.
  BASE_EXPORT char HexDigitToInt(wchar_t c);
  
  // Returns true if it's a Unicode whitespace character.
  BASE_EXPORT bool IsUnicodeWhitespace(wchar_t c);
  
  // 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 string16 FormatBytesUnlocalized(int64_t bytes);
  
  // Starting at |start_offset| (usually 0), replace the first instance of
  // |find_this| with |replace_with|.
  BASE_EXPORT void ReplaceFirstSubstringAfterOffset(
      base::string16* 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 <algorithm> for single
  // characters, for example:
  //   std::replace(str.begin(), str.end(), 'a', 'b');
  BASE_EXPORT void ReplaceSubstringsAfterOffset(
      string16* 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.
  //
  // |length_with_null| must be at least 2, since otherwise the underlying string
  // would have size 0, and trying to access &((*str)[0]) in that case can result
  // in a number of problems.
  //
  // 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* WriteInto(string16* str, size_t length_with_null);
  #ifndef OS_WIN
  BASE_EXPORT wchar_t* WriteInto(std::wstring* str, size_t length_with_null);
  #endif
  
  // Does the opposite of SplitString()/SplitStringPiece(). Joins a vector or list
  // of strings into a single string, inserting |separator| (which may be empty)
  // in between all elements.
  //
  // 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.
  BASE_EXPORT std::string JoinString(const std::vector<std::string>& parts,
                                     StringPiece separator);
  BASE_EXPORT string16 JoinString(const std::vector<string16>& parts,
                                  StringPiece16 separator);
  BASE_EXPORT std::string JoinString(const std::vector<StringPiece>& parts,
                                     StringPiece separator);
  BASE_EXPORT string16 JoinString(const std::vector<StringPiece16>& 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<StringPiece> parts,
                                     StringPiece separator);
  BASE_EXPORT string16 JoinString(std::initializer_list<StringPiece16> 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 string16 ReplaceStringPlaceholders(
      const string16& format_string,
      const std::vector<string16>& subst,
      std::vector<size_t>* offsets);
  
  BASE_EXPORT std::string ReplaceStringPlaceholders(
      const StringPiece& format_string,
      const std::vector<std::string>& subst,
      std::vector<size_t>* offsets);
  
  // Single-string shortcut for ReplaceStringHolders. |offset| may be NULL.
  BASE_EXPORT string16 ReplaceStringPlaceholders(const string16& format_string,
                                                 const string16& a,
                                                 size_t* offset);
  
  }  // namespace base
  
  #if defined(OS_WIN)
  #include "base/strings/string_util_win.h"
  #elif defined(OS_POSIX)
  #include "base/strings/string_util_posix.h"
  #else
  #error Define string operations appropriately for your platform
  #endif
  
  #endif  // BASE_STRINGS_STRING_UTIL_H_
  