Mark ConsumePrefix, ConsumeSuffix, StripPrefix, and StripSuffix as co…

…nstexpr since they are all pure functions.

Previously this was not possible because StartsWith() and EndsWith() were not constexpr, but this has been fixed.

PiperOrigin-RevId: 702625650
Change-Id: I6b165efac8335a06257e17e2fc91e5ea7e153eb7

absl/strings/strip.h

@@ -44,8 +44,8 @@ ABSL_NAMESPACE_BEGIN
 //   absl::string_view input("abc");
 //   EXPECT_TRUE(absl::ConsumePrefix(&input, "a"));
 //   EXPECT_EQ(input, "bc");
-inline bool ConsumePrefix(absl::Nonnull<absl::string_view*> str,
-                          absl::string_view expected) {
+inline constexpr bool ConsumePrefix(absl::Nonnull<absl::string_view*> str,
+                                    absl::string_view expected) {
   if (!absl::StartsWith(*str, expected)) return false;
   str->remove_prefix(expected.size());
   return true;
@@ -61,8 +61,8 @@ inline bool ConsumePrefix(absl::Nonnull<absl::string_view*> str,
 //   absl::string_view input("abcdef");
 //   EXPECT_TRUE(absl::ConsumeSuffix(&input, "def"));
 //   EXPECT_EQ(input, "abc");
-inline bool ConsumeSuffix(absl::Nonnull<absl::string_view*> str,
-                          absl::string_view expected) {
+inline constexpr bool ConsumeSuffix(absl::Nonnull<absl::string_view*> str,
+                                    absl::string_view expected) {
   if (!absl::EndsWith(*str, expected)) return false;
   str->remove_suffix(expected.size());
   return true;
@@ -73,7 +73,7 @@ inline bool ConsumeSuffix(absl::Nonnull<absl::string_view*> str,
 // Returns a view into the input string `str` with the given `prefix` removed,
 // but leaving the original string intact. If the prefix does not match at the
 // start of the string, returns the original string instead.
-ABSL_MUST_USE_RESULT inline absl::string_view StripPrefix(
+ABSL_MUST_USE_RESULT inline constexpr absl::string_view StripPrefix(
     absl::string_view str, absl::string_view prefix) {
   if (absl::StartsWith(str, prefix)) str.remove_prefix(prefix.size());
   return str;
@@ -84,7 +84,7 @@ ABSL_MUST_USE_RESULT inline absl::string_view StripPrefix(
 // Returns a view into the input string `str` with the given `suffix` removed,
 // but leaving the original string intact. If the suffix does not match at the
 // end of the string, returns the original string instead.
-ABSL_MUST_USE_RESULT inline absl::string_view StripSuffix(
+ABSL_MUST_USE_RESULT inline constexpr absl::string_view StripSuffix(
     absl::string_view str, absl::string_view suffix) {
   if (absl::EndsWith(str, suffix)) str.remove_suffix(suffix.size());
   return str;