Replace base::str[n]casecmp with helper functions.

base/strings/string_util.h

Index: base/strings/string_util.h
diff --git a/base/strings/string_util.h b/base/strings/string_util.h
index c2316099c9484bfb24b11c1f9a49ab4fbe7e4164..d1cdcc54e2fb675d3895321c7b898890ea5c2051 100644
--- a/base/strings/string_util.h
+++ b/base/strings/string_util.h
@@ -21,20 +21,10 @@
 
 namespace base {
 
-// C standard-library functions like "strncasecmp" and "snprintf" that aren't
-// cross-platform are provided as "base::strncasecmp", and their prototypes
-// are listed below.  These functions are then implemented as inline calls
-// to the platform-specific equivalents in the platform-specific headers.
-
-// Compares the two strings s1 and s2 without regard to case using
-// the current locale; returns 0 if they are equal, 1 if s1 > s2, and -1 if
-// s2 > s1 according to a lexicographic comparison.
-int strcasecmp(const char* s1, const char* s2);
-
-// Compares up to count characters of s1 and s2 without regard to case using
-// the current locale; returns 0 if they are equal, 1 if s1 > s2, and -1 if
-// s2 > s1 according to a lexicographic comparison.
-int strncasecmp(const char* s1, const char* s2, size_t count);
+// 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.
 
 // Same as strncmp but for char16 strings.
 int strncmp16(const char16* s1, const char16* s2, size_t count);
@@ -105,6 +95,7 @@ template <class Char> inline Char ToUpperASCII(Char c) {
 
 // Function objects to aid in comparing/searching strings.
 
+// DO NOT USE. tolower() will given incorrect results for non-ASCII characters.

[Nico, 2015/07/08 21:58:23]

suggest what to do instead?

 template<typename Char> struct CaseInsensitiveCompare {
  public:
   bool operator()(Char x, Char y) const {
@@ -121,6 +112,22 @@ template<typename Char> struct CaseInsensitiveCompareASCII {
   }
 };
 
+// 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.
 //