Add StrContainsIgnoreCase() to strings/match.h; all the other case-sensitive methods in this file have corresponding case-insensitive ones.

PiperOrigin-RevId: 516933773
Change-Id: Iaec41afd923b10bc493ad864c0ecfe85a1fe2db8

3 files changed, 75 insertions, 0 deletions

diff --git a/absl/strings/match.cc b/absl/strings/match.cc
index 2d672509..b65cbc67 100644
--- a/absl/strings/match.cc
+++ b/absl/strings/match.cc
@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include "absl/strings/match.h"
+#include "absl/strings/ascii.h"
 
 #include "absl/strings/internal/memutil.h"
 
@@ -27,6 +28,27 @@ bool EqualsIgnoreCase(absl::string_view piece1,
   // memcasecmp uses absl::ascii_tolower().
 }
 
+bool StrContainsIgnoreCase(absl::string_view haystack,
+                           absl::string_view needle) noexcept {
+  while (haystack.size() >= needle.size()) {
+    if (StartsWithIgnoreCase(haystack, needle)) return true;
+    haystack.remove_prefix(1);
+  }
+  return false;
+}
+
+bool StrContainsIgnoreCase(absl::string_view haystack,
+                           char needle) noexcept {
+  char upper_needle = absl::ascii_toupper(static_cast<unsigned char>(needle));
+  char lower_needle = absl::ascii_tolower(static_cast<unsigned char>(needle));
+  if (upper_needle == lower_needle) {
+    return StrContains(haystack, needle);
+  } else {
+    const char both_cstr[3] = {lower_needle, upper_needle, '\0'};
+    return haystack.find_first_of(both_cstr) != absl::string_view::npos;
+  }
+}
+
 bool StartsWithIgnoreCase(absl::string_view text,
                           absl::string_view prefix) noexcept {
   return (text.size() >= prefix.size()) &&
diff --git a/absl/strings/match.h b/absl/strings/match.h
index 038cbb3f..1dc0beaf 100644
--- a/absl/strings/match.h
+++ b/absl/strings/match.h
@@ -72,6 +72,15 @@ inline bool EndsWith(absl::string_view text,
           memcmp(text.data() + (text.size() - suffix.size()), suffix.data(),
                  suffix.size()) == 0);
 }
+// StrContainsIgnoreCase()
+//
+// Returns whether a given ASCII string `haystack` contains the ASCII substring
+// `needle`, ignoring case in the comparison.
+bool StrContainsIgnoreCase(absl::string_view haystack,
+                           absl::string_view needle) noexcept;
+
+bool StrContainsIgnoreCase(absl::string_view haystack,
+                           char needle) noexcept;
 
 // EqualsIgnoreCase()
 //
diff --git a/absl/strings/match_test.cc b/absl/strings/match_test.cc
index 5841bc1b..f063b4ea 100644
--- a/absl/strings/match_test.cc
+++ b/absl/strings/match_test.cc
@@ -124,4 +124,48 @@ TEST(MatchTest, EndsWithIgnoreCase) {
   EXPECT_FALSE(absl::EndsWithIgnoreCase("", "fo"));
 }
 
+TEST(MatchTest, ContainsIgnoreCase) {
+  EXPECT_TRUE(absl::StrContainsIgnoreCase("foo", "foo"));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase("FOO", "Foo"));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase("--FOO", "Foo"));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase("FOO--", "Foo"));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase("BAR", "Foo"));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase("BAR", "Foo"));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase("123456", "123456"));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase("123456", "234"));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase("", ""));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase("abc", ""));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase("", "a"));
+}
+
+TEST(MatchTest, ContainsCharIgnoreCase) {
+  absl::string_view a("AaBCdefg!");
+  absl::string_view b("AaBCd!");
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(a, 'a'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(a, 'A'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(a, 'b'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(a, 'B'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(a, 'e'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(a, 'E'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase(a, 'h'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase(a, 'H'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(a, '!'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase(a, '?'));
+
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(b, 'a'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(b, 'A'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(b, 'b'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(b, 'B'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase(b, 'e'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase(b, 'E'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase(b, 'h'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase(b, 'H'));
+  EXPECT_TRUE(absl::StrContainsIgnoreCase(b, '!'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase(b, '?'));
+
+  EXPECT_FALSE(absl::StrContainsIgnoreCase("", 'a'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase("", 'A'));
+  EXPECT_FALSE(absl::StrContainsIgnoreCase("", '0'));
+}
+
 }  // namespace