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      1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 //
      5 // This file defines utility functions for working with strings.
      6 
      7 #ifndef BASE_STRING_UTIL_H_
      8 #define BASE_STRING_UTIL_H_
      9 #pragma once
     10 
     11 #include <stdarg.h>   // va_list
     12 
     13 #include <string>
     14 #include <vector>
     15 
     16 #include "base/base_api.h"
     17 #include "base/basictypes.h"
     18 #include "base/compiler_specific.h"
     19 #include "base/string16.h"
     20 #include "base/string_piece.h"  // For implicit conversions.
     21 
     22 // TODO(brettw) remove this dependency. Previously StringPrintf lived in this
     23 // file. We need to convert the callers over to using stringprintf.h instead
     24 // and then remove this.
     25 #include "base/stringprintf.h"
     26 
     27 // Safe standard library wrappers for all platforms.
     28 
     29 namespace base {
     30 
     31 // C standard-library functions like "strncasecmp" and "snprintf" that aren't
     32 // cross-platform are provided as "base::strncasecmp", and their prototypes
     33 // are listed below.  These functions are then implemented as inline calls
     34 // to the platform-specific equivalents in the platform-specific headers.
     35 
     36 // Compares the two strings s1 and s2 without regard to case using
     37 // the current locale; returns 0 if they are equal, 1 if s1 > s2, and -1 if
     38 // s2 > s1 according to a lexicographic comparison.
     39 BASE_API int strcasecmp(const char* s1, const char* s2);
     40 
     41 // Compares up to count characters of s1 and s2 without regard to case using
     42 // the current locale; returns 0 if they are equal, 1 if s1 > s2, and -1 if
     43 // s2 > s1 according to a lexicographic comparison.
     44 BASE_API int strncasecmp(const char* s1, const char* s2, size_t count);
     45 
     46 // Same as strncmp but for char16 strings.
     47 BASE_API int strncmp16(const char16* s1, const char16* s2, size_t count);
     48 
     49 // Wrapper for vsnprintf that always null-terminates and always returns the
     50 // number of characters that would be in an untruncated formatted
     51 // string, even when truncation occurs.
     52 BASE_API int vsnprintf(char* buffer, size_t size, const char* format,
     53                        va_list arguments)
     54     PRINTF_FORMAT(3, 0);
     55 
     56 // vswprintf always null-terminates, but when truncation occurs, it will either
     57 // return -1 or the number of characters that would be in an untruncated
     58 // formatted string.  The actual return value depends on the underlying
     59 // C library's vswprintf implementation.
     60 BASE_API int vswprintf(wchar_t* buffer, size_t size,
     61                        const wchar_t* format, va_list arguments)
     62     WPRINTF_FORMAT(3, 0);
     63 
     64 // Some of these implementations need to be inlined.
     65 
     66 // We separate the declaration from the implementation of this inline
     67 // function just so the PRINTF_FORMAT works.
     68 inline int snprintf(char* buffer, size_t size, const char* format, ...)
     69     PRINTF_FORMAT(3, 4);
     70 inline int snprintf(char* buffer, size_t size, const char* format, ...) {
     71   va_list arguments;
     72   va_start(arguments, format);
     73   int result = vsnprintf(buffer, size, format, arguments);
     74   va_end(arguments);
     75   return result;
     76 }
     77 
     78 // We separate the declaration from the implementation of this inline
     79 // function just so the WPRINTF_FORMAT works.
     80 inline int swprintf(wchar_t* buffer, size_t size, const wchar_t* format, ...)
     81     WPRINTF_FORMAT(3, 4);
     82 inline int swprintf(wchar_t* buffer, size_t size, const wchar_t* format, ...) {
     83   va_list arguments;
     84   va_start(arguments, format);
     85   int result = vswprintf(buffer, size, format, arguments);
     86   va_end(arguments);
     87   return result;
     88 }
     89 
     90 // BSD-style safe and consistent string copy functions.
     91 // Copies |src| to |dst|, where |dst_size| is the total allocated size of |dst|.
     92 // Copies at most |dst_size|-1 characters, and always NULL terminates |dst|, as
     93 // long as |dst_size| is not 0.  Returns the length of |src| in characters.
     94 // If the return value is >= dst_size, then the output was truncated.
     95 // NOTE: All sizes are in number of characters, NOT in bytes.
     96 BASE_API size_t strlcpy(char* dst, const char* src, size_t dst_size);
     97 BASE_API size_t wcslcpy(wchar_t* dst, const wchar_t* src, size_t dst_size);
     98 
     99 // Scan a wprintf format string to determine whether it's portable across a
    100 // variety of systems.  This function only checks that the conversion
    101 // specifiers used by the format string are supported and have the same meaning
    102 // on a variety of systems.  It doesn't check for other errors that might occur
    103 // within a format string.
    104 //
    105 // Nonportable conversion specifiers for wprintf are:
    106 //  - 's' and 'c' without an 'l' length modifier.  %s and %c operate on char
    107 //     data on all systems except Windows, which treat them as wchar_t data.
    108 //     Use %ls and %lc for wchar_t data instead.
    109 //  - 'S' and 'C', which operate on wchar_t data on all systems except Windows,
    110 //     which treat them as char data.  Use %ls and %lc for wchar_t data
    111 //     instead.
    112 //  - 'F', which is not identified by Windows wprintf documentation.
    113 //  - 'D', 'O', and 'U', which are deprecated and not available on all systems.
    114 //     Use %ld, %lo, and %lu instead.
    115 //
    116 // Note that there is no portable conversion specifier for char data when
    117 // working with wprintf.
    118 //
    119 // This function is intended to be called from base::vswprintf.
    120 BASE_API bool IsWprintfFormatPortable(const wchar_t* format);
    121 
    122 // ASCII-specific tolower.  The standard library's tolower is locale sensitive,
    123 // so we don't want to use it here.
    124 template <class Char> inline Char ToLowerASCII(Char c) {
    125   return (c >= 'A' && c <= 'Z') ? (c + ('a' - 'A')) : c;
    126 }
    127 
    128 // ASCII-specific toupper.  The standard library's toupper is locale sensitive,
    129 // so we don't want to use it here.
    130 template <class Char> inline Char ToUpperASCII(Char c) {
    131   return (c >= 'a' && c <= 'z') ? (c + ('A' - 'a')) : c;
    132 }
    133 
    134 // Function objects to aid in comparing/searching strings.
    135 
    136 template<typename Char> struct CaseInsensitiveCompare {
    137  public:
    138   bool operator()(Char x, Char y) const {
    139     // TODO(darin): Do we really want to do locale sensitive comparisons here?
    140     // See http://crbug.com/24917
    141     return tolower(x) == tolower(y);
    142   }
    143 };
    144 
    145 template<typename Char> struct CaseInsensitiveCompareASCII {
    146  public:
    147   bool operator()(Char x, Char y) const {
    148     return ToLowerASCII(x) == ToLowerASCII(y);
    149   }
    150 };
    151 
    152 }  // namespace base
    153 
    154 #if defined(OS_WIN)
    155 #include "base/string_util_win.h"
    156 #elif defined(OS_POSIX)
    157 #include "base/string_util_posix.h"
    158 #else
    159 #error Define string operations appropriately for your platform
    160 #endif
    161 
    162 // These threadsafe functions return references to globally unique empty
    163 // strings.
    164 //
    165 // DO NOT USE THESE AS A GENERAL-PURPOSE SUBSTITUTE FOR DEFAULT CONSTRUCTORS.
    166 // There is only one case where you should use these: functions which need to
    167 // return a string by reference (e.g. as a class member accessor), and don't
    168 // have an empty string to use (e.g. in an error case).  These should not be
    169 // used as initializers, function arguments, or return values for functions
    170 // which return by value or outparam.
    171 BASE_API const std::string& EmptyString();
    172 BASE_API const std::wstring& EmptyWString();
    173 BASE_API const string16& EmptyString16();
    174 
    175 extern const wchar_t kWhitespaceWide[];
    176 extern const char16 kWhitespaceUTF16[];
    177 extern const char kWhitespaceASCII[];
    178 
    179 extern const char kUtf8ByteOrderMark[];
    180 
    181 // Removes characters in remove_chars from anywhere in input.  Returns true if
    182 // any characters were removed.
    183 // NOTE: Safe to use the same variable for both input and output.
    184 BASE_API bool RemoveChars(const std::wstring& input,
    185                           const wchar_t remove_chars[],
    186                           std::wstring* output);
    187 BASE_API bool RemoveChars(const string16& input,
    188                           const char16 remove_chars[],
    189                           string16* output);
    190 BASE_API bool RemoveChars(const std::string& input,
    191                           const char remove_chars[],
    192                           std::string* output);
    193 
    194 // Removes characters in trim_chars from the beginning and end of input.
    195 // NOTE: Safe to use the same variable for both input and output.
    196 BASE_API bool TrimString(const std::wstring& input,
    197                          const wchar_t trim_chars[],
    198                          std::wstring* output);
    199 BASE_API bool TrimString(const string16& input,
    200                          const char16 trim_chars[],
    201                          string16* output);
    202 BASE_API bool TrimString(const std::string& input,
    203                          const char trim_chars[],
    204                          std::string* output);
    205 
    206 // Truncates a string to the nearest UTF-8 character that will leave
    207 // the string less than or equal to the specified byte size.
    208 BASE_API void TruncateUTF8ToByteSize(const std::string& input,
    209                                      const size_t byte_size,
    210                                      std::string* output);
    211 
    212 // Trims any whitespace from either end of the input string.  Returns where
    213 // whitespace was found.
    214 // The non-wide version has two functions:
    215 // * TrimWhitespaceASCII()
    216 //   This function is for ASCII strings and only looks for ASCII whitespace;
    217 // Please choose the best one according to your usage.
    218 // NOTE: Safe to use the same variable for both input and output.
    219 enum TrimPositions {
    220   TRIM_NONE     = 0,
    221   TRIM_LEADING  = 1 << 0,
    222   TRIM_TRAILING = 1 << 1,
    223   TRIM_ALL      = TRIM_LEADING | TRIM_TRAILING,
    224 };
    225 BASE_API TrimPositions TrimWhitespace(const std::wstring& input,
    226                                       TrimPositions positions,
    227                                       std::wstring* output);
    228 BASE_API TrimPositions TrimWhitespace(const string16& input,
    229                                       TrimPositions positions,
    230                                       string16* output);
    231 BASE_API TrimPositions TrimWhitespaceASCII(const std::string& input,
    232                                            TrimPositions positions,
    233                                            std::string* output);
    234 
    235 // Deprecated. This function is only for backward compatibility and calls
    236 // TrimWhitespaceASCII().
    237 BASE_API TrimPositions TrimWhitespace(const std::string& input,
    238                                       TrimPositions positions,
    239                                       std::string* output);
    240 
    241 // Searches  for CR or LF characters.  Removes all contiguous whitespace
    242 // strings that contain them.  This is useful when trying to deal with text
    243 // copied from terminals.
    244 // Returns |text|, with the following three transformations:
    245 // (1) Leading and trailing whitespace is trimmed.
    246 // (2) If |trim_sequences_with_line_breaks| is true, any other whitespace
    247 //     sequences containing a CR or LF are trimmed.
    248 // (3) All other whitespace sequences are converted to single spaces.
    249 BASE_API std::wstring CollapseWhitespace(const std::wstring& text,
    250                                          bool trim_sequences_with_line_breaks);
    251 BASE_API string16 CollapseWhitespace(const string16& text,
    252                                      bool trim_sequences_with_line_breaks);
    253 BASE_API std::string CollapseWhitespaceASCII(
    254     const std::string& text, bool trim_sequences_with_line_breaks);
    255 
    256 // Returns true if the passed string is empty or contains only white-space
    257 // characters.
    258 BASE_API bool ContainsOnlyWhitespaceASCII(const std::string& str);
    259 BASE_API bool ContainsOnlyWhitespace(const string16& str);
    260 
    261 // Returns true if |input| is empty or contains only characters found in
    262 // |characters|.
    263 BASE_API bool ContainsOnlyChars(const std::wstring& input,
    264                                 const std::wstring& characters);
    265 BASE_API bool ContainsOnlyChars(const string16& input,
    266                                 const string16& characters);
    267 BASE_API bool ContainsOnlyChars(const std::string& input,
    268                                 const std::string& characters);
    269 
    270 // Converts to 7-bit ASCII by truncating. The result must be known to be ASCII
    271 // beforehand.
    272 BASE_API std::string WideToASCII(const std::wstring& wide);
    273 BASE_API std::string UTF16ToASCII(const string16& utf16);
    274 
    275 // Converts the given wide string to the corresponding Latin1. This will fail
    276 // (return false) if any characters are more than 255.
    277 BASE_API bool WideToLatin1(const std::wstring& wide, std::string* latin1);
    278 
    279 // Returns true if the specified string matches the criteria. How can a wide
    280 // string be 8-bit or UTF8? It contains only characters that are < 256 (in the
    281 // first case) or characters that use only 8-bits and whose 8-bit
    282 // representation looks like a UTF-8 string (the second case).
    283 //
    284 // Note that IsStringUTF8 checks not only if the input is structurally
    285 // valid but also if it doesn't contain any non-character codepoint
    286 // (e.g. U+FFFE). It's done on purpose because all the existing callers want
    287 // to have the maximum 'discriminating' power from other encodings. If
    288 // there's a use case for just checking the structural validity, we have to
    289 // add a new function for that.
    290 BASE_API bool IsStringUTF8(const std::string& str);
    291 BASE_API bool IsStringASCII(const std::wstring& str);
    292 BASE_API bool IsStringASCII(const base::StringPiece& str);
    293 BASE_API bool IsStringASCII(const string16& str);
    294 
    295 // Converts the elements of the given string.  This version uses a pointer to
    296 // clearly differentiate it from the non-pointer variant.
    297 template <class str> inline void StringToLowerASCII(str* s) {
    298   for (typename str::iterator i = s->begin(); i != s->end(); ++i)
    299     *i = base::ToLowerASCII(*i);
    300 }
    301 
    302 template <class str> inline str StringToLowerASCII(const str& s) {
    303   // for std::string and std::wstring
    304   str output(s);
    305   StringToLowerASCII(&output);
    306   return output;
    307 }
    308 
    309 // Converts the elements of the given string.  This version uses a pointer to
    310 // clearly differentiate it from the non-pointer variant.
    311 template <class str> inline void StringToUpperASCII(str* s) {
    312   for (typename str::iterator i = s->begin(); i != s->end(); ++i)
    313     *i = base::ToUpperASCII(*i);
    314 }
    315 
    316 template <class str> inline str StringToUpperASCII(const str& s) {
    317   // for std::string and std::wstring
    318   str output(s);
    319   StringToUpperASCII(&output);
    320   return output;
    321 }
    322 
    323 // Compare the lower-case form of the given string against the given ASCII
    324 // string.  This is useful for doing checking if an input string matches some
    325 // token, and it is optimized to avoid intermediate string copies.  This API is
    326 // borrowed from the equivalent APIs in Mozilla.
    327 BASE_API bool LowerCaseEqualsASCII(const std::string& a, const char* b);
    328 BASE_API bool LowerCaseEqualsASCII(const std::wstring& a, const char* b);
    329 BASE_API bool LowerCaseEqualsASCII(const string16& a, const char* b);
    330 
    331 // Same thing, but with string iterators instead.
    332 BASE_API bool LowerCaseEqualsASCII(std::string::const_iterator a_begin,
    333                                    std::string::const_iterator a_end,
    334                                    const char* b);
    335 BASE_API bool LowerCaseEqualsASCII(std::wstring::const_iterator a_begin,
    336                                    std::wstring::const_iterator a_end,
    337                                    const char* b);
    338 BASE_API bool LowerCaseEqualsASCII(string16::const_iterator a_begin,
    339                                    string16::const_iterator a_end,
    340                                    const char* b);
    341 BASE_API bool LowerCaseEqualsASCII(const char* a_begin,
    342                                    const char* a_end,
    343                                    const char* b);
    344 BASE_API bool LowerCaseEqualsASCII(const wchar_t* a_begin,
    345                                    const wchar_t* a_end,
    346                                    const char* b);
    347 BASE_API bool LowerCaseEqualsASCII(const char16* a_begin,
    348                                    const char16* a_end,
    349                                    const char* b);
    350 
    351 // Performs a case-sensitive string compare. The behavior is undefined if both
    352 // strings are not ASCII.
    353 BASE_API bool EqualsASCII(const string16& a, const base::StringPiece& b);
    354 
    355 // Returns true if str starts with search, or false otherwise.
    356 BASE_API bool StartsWithASCII(const std::string& str,
    357                               const std::string& search,
    358                               bool case_sensitive);
    359 BASE_API bool StartsWith(const std::wstring& str,
    360                          const std::wstring& search,
    361                          bool case_sensitive);
    362 BASE_API bool StartsWith(const string16& str,
    363                          const string16& search,
    364                          bool case_sensitive);
    365 
    366 // Returns true if str ends with search, or false otherwise.
    367 BASE_API bool EndsWith(const std::string& str,
    368                        const std::string& search,
    369                        bool case_sensitive);
    370 BASE_API bool EndsWith(const std::wstring& str,
    371                        const std::wstring& search,
    372                        bool case_sensitive);
    373 BASE_API bool EndsWith(const string16& str,
    374                        const string16& search,
    375                        bool case_sensitive);
    376 
    377 
    378 // Determines the type of ASCII character, independent of locale (the C
    379 // library versions will change based on locale).
    380 template <typename Char>
    381 inline bool IsAsciiWhitespace(Char c) {
    382   return c == ' ' || c == '\r' || c == '\n' || c == '\t';
    383 }
    384 template <typename Char>
    385 inline bool IsAsciiAlpha(Char c) {
    386   return ((c >= 'A') && (c <= 'Z')) || ((c >= 'a') && (c <= 'z'));
    387 }
    388 template <typename Char>
    389 inline bool IsAsciiDigit(Char c) {
    390   return c >= '0' && c <= '9';
    391 }
    392 
    393 template <typename Char>
    394 inline bool IsHexDigit(Char c) {
    395   return (c >= '0' && c <= '9') ||
    396          (c >= 'A' && c <= 'F') ||
    397          (c >= 'a' && c <= 'f');
    398 }
    399 
    400 template <typename Char>
    401 inline Char HexDigitToInt(Char c) {
    402   DCHECK(IsHexDigit(c));
    403   if (c >= '0' && c <= '9')
    404     return c - '0';
    405   if (c >= 'A' && c <= 'F')
    406     return c - 'A' + 10;
    407   if (c >= 'a' && c <= 'f')
    408     return c - 'a' + 10;
    409   return 0;
    410 }
    411 
    412 // Returns true if it's a whitespace character.
    413 inline bool IsWhitespace(wchar_t c) {
    414   return wcschr(kWhitespaceWide, c) != NULL;
    415 }
    416 
    417 enum DataUnits {
    418   DATA_UNITS_BYTE = 0,
    419   DATA_UNITS_KIBIBYTE,
    420   DATA_UNITS_MEBIBYTE,
    421   DATA_UNITS_GIBIBYTE,
    422 };
    423 
    424 // Return the unit type that is appropriate for displaying the amount of bytes
    425 // passed in.
    426 BASE_API DataUnits GetByteDisplayUnits(int64 bytes);
    427 
    428 // Return a byte string in human-readable format, displayed in units appropriate
    429 // specified by 'units', with an optional unit suffix.
    430 // Ex: FormatBytes(512, DATA_UNITS_KIBIBYTE, true) => "0.5 KB"
    431 // Ex: FormatBytes(10*1024, DATA_UNITS_MEBIBYTE, false) => "0.1"
    432 BASE_API string16 FormatBytes(int64 bytes, DataUnits units, bool show_units);
    433 
    434 // As above, but with "/s" units.
    435 // Ex: FormatSpeed(512, DATA_UNITS_KIBIBYTE, true) => "0.5 KB/s"
    436 // Ex: FormatSpeed(10*1024, DATA_UNITS_MEBIBYTE, false) => "0.1"
    437 BASE_API string16 FormatSpeed(int64 bytes, DataUnits units, bool show_units);
    438 
    439 // Return a number formated with separators in the user's locale way.
    440 // Ex: FormatNumber(1234567) => 1,234,567
    441 BASE_API string16 FormatNumber(int64 number);
    442 
    443 // Starting at |start_offset| (usually 0), replace the first instance of
    444 // |find_this| with |replace_with|.
    445 BASE_API void ReplaceFirstSubstringAfterOffset(string16* str,
    446                                                string16::size_type start_offset,
    447                                                const string16& find_this,
    448                                                const string16& replace_with);
    449 BASE_API void ReplaceFirstSubstringAfterOffset(
    450     std::string* str,
    451     std::string::size_type start_offset,
    452     const std::string& find_this,
    453     const std::string& replace_with);
    454 
    455 // Starting at |start_offset| (usually 0), look through |str| and replace all
    456 // instances of |find_this| with |replace_with|.
    457 //
    458 // This does entire substrings; use std::replace in <algorithm> for single
    459 // characters, for example:
    460 //   std::replace(str.begin(), str.end(), 'a', 'b');
    461 BASE_API void ReplaceSubstringsAfterOffset(string16* str,
    462                                            string16::size_type start_offset,
    463                                            const string16& find_this,
    464                                            const string16& replace_with);
    465 BASE_API void ReplaceSubstringsAfterOffset(std::string* str,
    466                                            std::string::size_type start_offset,
    467                                            const std::string& find_this,
    468                                            const std::string& replace_with);
    469 
    470 // This is mpcomplete's pattern for saving a string copy when dealing with
    471 // a function that writes results into a wchar_t[] and wanting the result to
    472 // end up in a std::wstring.  It ensures that the std::wstring's internal
    473 // buffer has enough room to store the characters to be written into it, and
    474 // sets its .length() attribute to the right value.
    475 //
    476 // The reserve() call allocates the memory required to hold the string
    477 // plus a terminating null.  This is done because resize() isn't
    478 // guaranteed to reserve space for the null.  The resize() call is
    479 // simply the only way to change the string's 'length' member.
    480 //
    481 // XXX-performance: the call to wide.resize() takes linear time, since it fills
    482 // the string's buffer with nulls.  I call it to change the length of the
    483 // string (needed because writing directly to the buffer doesn't do this).
    484 // Perhaps there's a constant-time way to change the string's length.
    485 template <class string_type>
    486 inline typename string_type::value_type* WriteInto(string_type* str,
    487                                                    size_t length_with_null) {
    488   str->reserve(length_with_null);
    489   str->resize(length_with_null - 1);
    490   return &((*str)[0]);
    491 }
    492 
    493 //-----------------------------------------------------------------------------
    494 
    495 // Splits a string into its fields delimited by any of the characters in
    496 // |delimiters|.  Each field is added to the |tokens| vector.  Returns the
    497 // number of tokens found.
    498 BASE_API size_t Tokenize(const std::wstring& str,
    499                          const std::wstring& delimiters,
    500                          std::vector<std::wstring>* tokens);
    501 BASE_API size_t Tokenize(const string16& str,
    502                          const string16& delimiters,
    503                          std::vector<string16>* tokens);
    504 BASE_API size_t Tokenize(const std::string& str,
    505                          const std::string& delimiters,
    506                          std::vector<std::string>* tokens);
    507 BASE_API size_t Tokenize(const base::StringPiece& str,
    508                          const base::StringPiece& delimiters,
    509                          std::vector<base::StringPiece>* tokens);
    510 
    511 // Does the opposite of SplitString().
    512 BASE_API string16 JoinString(const std::vector<string16>& parts, char16 s);
    513 BASE_API std::string JoinString(const std::vector<std::string>& parts, char s);
    514 
    515 // Replace $1-$2-$3..$9 in the format string with |a|-|b|-|c|..|i| respectively.
    516 // Additionally, any number of consecutive '$' characters is replaced by that
    517 // number less one. Eg $$->$, $$$->$$, etc. The offsets parameter here can be
    518 // NULL. This only allows you to use up to nine replacements.
    519 BASE_API string16 ReplaceStringPlaceholders(const string16& format_string,
    520                                             const std::vector<string16>& subst,
    521                                             std::vector<size_t>* offsets);
    522 
    523 BASE_API std::string ReplaceStringPlaceholders(
    524     const base::StringPiece& format_string,
    525     const std::vector<std::string>& subst,
    526     std::vector<size_t>* offsets);
    527 
    528 // Single-string shortcut for ReplaceStringHolders. |offset| may be NULL.
    529 BASE_API string16 ReplaceStringPlaceholders(const string16& format_string,
    530                                             const string16& a,
    531                                             size_t* offset);
    532 
    533 // Returns true if the string passed in matches the pattern. The pattern
    534 // string can contain wildcards like * and ?
    535 // The backslash character (\) is an escape character for * and ?
    536 // We limit the patterns to having a max of 16 * or ? characters.
    537 // ? matches 0 or 1 character, while * matches 0 or more characters.
    538 BASE_API bool MatchPattern(const base::StringPiece& string,
    539                            const base::StringPiece& pattern);
    540 BASE_API bool MatchPattern(const string16& string, const string16& pattern);
    541 
    542 // Hack to convert any char-like type to its unsigned counterpart.
    543 // For example, it will convert char, signed char and unsigned char to unsigned
    544 // char.
    545 template<typename T>
    546 struct ToUnsigned {
    547   typedef T Unsigned;
    548 };
    549 
    550 template<>
    551 struct ToUnsigned<char> {
    552   typedef unsigned char Unsigned;
    553 };
    554 template<>
    555 struct ToUnsigned<signed char> {
    556   typedef unsigned char Unsigned;
    557 };
    558 template<>
    559 struct ToUnsigned<wchar_t> {
    560 #if defined(WCHAR_T_IS_UTF16)
    561   typedef unsigned short Unsigned;
    562 #elif defined(WCHAR_T_IS_UTF32)
    563   typedef uint32 Unsigned;
    564 #endif
    565 };
    566 template<>
    567 struct ToUnsigned<short> {
    568   typedef unsigned short Unsigned;
    569 };
    570 
    571 #endif  // BASE_STRING_UTIL_H_
    572