Add some predicated searching functions to StringRef.

This adds 4 new functions to StringRef, which can be used to
take or drop characters while a certain condition is met, or
until a certain condition is met.  They are:

take_while - Return characters until a condition is not met.
take_until - Return characters until a condition is met.
drop_while - Remove characters until a condition is not met.
drop_until - Remove characters until a condition is met.

Internally, all of these functions delegate to two additional
helper functions which can be used to search for the position
of a character meeting or not meeting a condition, which are:

find_if - Find the first character matching a predicate.
find_if_not - Find the first character not matching a predicate.

Differential Revision: https://reviews.llvm.org/D24842

llvm-svn: 282346

1 files changed, 56 insertions, 0 deletions

diff --git a/llvm/unittests/ADT/StringRefTest.cpp b/llvm/unittests/ADT/StringRefTest.cpp
index 39ed71b..e1f5496 100644
--- a/llvm/unittests/ADT/StringRefTest.cpp
+++ b/llvm/unittests/ADT/StringRefTest.cpp
@@ -864,4 +864,60 @@ TEST(StringRefTest, Take) {
   EXPECT_TRUE(Taken.empty());
 }
 
+TEST(StringRefTest, FindIf) {
+  StringRef Punct("Test.String");
+  StringRef NoPunct("ABCDEFG");
+  StringRef Empty;
+
+  auto IsPunct = [](char c) { return ::ispunct(c); };
+  auto IsAlpha = [](char c) { return ::isalpha(c); };
+  EXPECT_EQ(4, Punct.find_if(IsPunct));
+  EXPECT_EQ(StringRef::npos, NoPunct.find_if(IsPunct));
+  EXPECT_EQ(StringRef::npos, Empty.find_if(IsPunct));
+
+  EXPECT_EQ(4, Punct.find_if_not(IsAlpha));
+  EXPECT_EQ(StringRef::npos, NoPunct.find_if_not(IsAlpha));
+  EXPECT_EQ(StringRef::npos, Empty.find_if_not(IsAlpha));
+}
+
+TEST(StringRefTest, TakeWhileUntil) {
+  StringRef Test("String With 1 Number");
+
+  StringRef Taken = Test.take_while([](char c) { return ::isdigit(c); });
+  EXPECT_EQ("", Taken);
+
+  Taken = Test.take_until([](char c) { return ::isdigit(c); });
+  EXPECT_EQ("String With ", Taken);
+
+  Taken = Test.take_while([](char c) { return true; });
+  EXPECT_EQ(Test, Taken);
+
+  Taken = Test.take_until([](char c) { return true; });
+  EXPECT_EQ("", Taken);
+
+  Test = "";
+  Taken = Test.take_while([](char c) { return true; });
+  EXPECT_EQ("", Taken);
+}
+
+TEST(StringRefTest, DropWhileUntil) {
+  StringRef Test("String With 1 Number");
+
+  StringRef Taken = Test.drop_while([](char c) { return ::isdigit(c); });
+  EXPECT_EQ(Test, Taken);
+
+  Taken = Test.drop_until([](char c) { return ::isdigit(c); });
+  EXPECT_EQ("1 Number", Taken);
+
+  Taken = Test.drop_while([](char c) { return true; });
+  EXPECT_EQ("", Taken);
+
+  Taken = Test.drop_until([](char c) { return true; });
+  EXPECT_EQ(Test, Taken);
+
+  StringRef EmptyString = "";
+  Taken = EmptyString.drop_while([](char c) { return true; });
+  EXPECT_EQ("", Taken);
+}
+
 } // end anonymous namespace