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[ADT] Add 'consume_front' and 'consume_back' methods to StringRef which 

are very handy when parsing text.

They are essentially a combination of startswith and a self-modifying
drop_front, or endswith and drop_back respectively.

Differential Revision: https://reviews.llvm.org/D22723

llvm-svn: 277288
This commit is contained in:
Chandler Carruth 2016-07-31 02:19:13 +00:00
parent 5e5501861a
commit 974c67e7c6
2 changed files with 56 additions and 0 deletions
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24
llvm/include/llvm/ADT/StringRef.h
View File

@ -446,6 +446,30 @@ namespace llvm {
return substr(0, size()-N); return substr(0, size()-N);
} }
/// Returns true if this StringRef has the given prefix and removes that
/// prefix.
LLVM_ATTRIBUTE_ALWAYS_INLINE
LLVM_ATTRIBUTE_UNUSED_RESULT
bool consume_front(StringRef Prefix) {
if (!startswith(Prefix))
return false;
*this = drop_front(Prefix.size());
return true;
}
/// Returns true if this StringRef has the given suffix and removes that
/// suffix.
LLVM_ATTRIBUTE_ALWAYS_INLINE
LLVM_ATTRIBUTE_UNUSED_RESULT
bool consume_back(StringRef Suffix) {
if (!endswith(Suffix))
return false;
*this = drop_back(Suffix.size());
return true;
}
/// Return a reference to the substring from [Start, End). /// Return a reference to the substring from [Start, End).
/// ///
/// \param Start The index of the starting character in the substring; if /// \param Start The index of the starting character in the substring; if

32
llvm/unittests/ADT/StringRefTest.cpp
View File

@ -322,6 +322,22 @@ TEST(StringRefTest, StartsWithLower) {
EXPECT_FALSE(Str.startswith_lower("hi")); EXPECT_FALSE(Str.startswith_lower("hi"));
} }
TEST(StringRefTest, ConsumeFront) {
StringRef Str("hello");
EXPECT_TRUE(Str.consume_front(""));
EXPECT_EQ("hello", Str);
EXPECT_TRUE(Str.consume_front("he"));
EXPECT_EQ("llo", Str);
EXPECT_FALSE(Str.consume_front("lloworld"));
EXPECT_EQ("llo", Str);
EXPECT_FALSE(Str.consume_front("lol"));
EXPECT_EQ("llo", Str);
EXPECT_TRUE(Str.consume_front("llo"));
EXPECT_EQ("", Str);
EXPECT_FALSE(Str.consume_front("o"));
EXPECT_TRUE(Str.consume_front(""));
}
TEST(StringRefTest, EndsWith) { TEST(StringRefTest, EndsWith) {
StringRef Str("hello"); StringRef Str("hello");
EXPECT_TRUE(Str.endswith("")); EXPECT_TRUE(Str.endswith(""));
@ -341,6 +357,22 @@ TEST(StringRefTest, EndsWithLower) {
EXPECT_FALSE(Str.endswith_lower("hi")); EXPECT_FALSE(Str.endswith_lower("hi"));
} }
TEST(StringRefTest, ConsumeBack) {
StringRef Str("hello");
EXPECT_TRUE(Str.consume_back(""));
EXPECT_EQ("hello", Str);
EXPECT_TRUE(Str.consume_back("lo"));
EXPECT_EQ("hel", Str);
EXPECT_FALSE(Str.consume_back("helhel"));
EXPECT_EQ("hel", Str);
EXPECT_FALSE(Str.consume_back("hle"));
EXPECT_EQ("hel", Str);
EXPECT_TRUE(Str.consume_back("hel"));
EXPECT_EQ("", Str);
EXPECT_FALSE(Str.consume_back("h"));
EXPECT_TRUE(Str.consume_back(""));
}
TEST(StringRefTest, Find) { TEST(StringRefTest, Find) {
StringRef Str("hello"); StringRef Str("hello");
EXPECT_EQ(2U, Str.find('l')); EXPECT_EQ(2U, Str.find('l'));