[libc] Adds strrchr implementation.
Reviewed By: sivachandra
Differential Revision: https://reviews.llvm.org/D84875
GitOrigin-RevId: e8a2af28afd5b4370fb66d8810ff979d1cb4d45b
diff --git a/config/linux/aarch64/entrypoints.txt b/config/linux/aarch64/entrypoints.txt
index 5f058e6..8314df8 100644
--- a/config/linux/aarch64/entrypoints.txt
+++ b/config/linux/aarch64/entrypoints.txt
@@ -20,6 +20,7 @@
libc.src.string.strcpy
libc.src.string.strlen
libc.src.string.strnlen
+ libc.src.string.strrchr
libc.src.string.strstr
)
diff --git a/config/linux/x86_64/entrypoints.txt b/config/linux/x86_64/entrypoints.txt
index 5dc1d38..56a99d0 100644
--- a/config/linux/x86_64/entrypoints.txt
+++ b/config/linux/x86_64/entrypoints.txt
@@ -38,6 +38,7 @@
libc.src.string.strcpy
libc.src.string.strlen
libc.src.string.strnlen
+ libc.src.string.strrchr
libc.src.string.strstr
# sys/mman.h entrypoints
diff --git a/src/string/CMakeLists.txt b/src/string/CMakeLists.txt
index 99450d5..d0eab63 100644
--- a/src/string/CMakeLists.txt
+++ b/src/string/CMakeLists.txt
@@ -86,6 +86,14 @@
memrchr.h
)
+add_entrypoint_object(
+ strrchr
+ SRCS
+ strrchr.cpp
+ HDRS
+ strrchr.h
+)
+
# Helper to define a function with multiple implementations
# - Computes flags to satisfy required/rejected features and arch,
# - Declares an entry point,
diff --git a/src/string/strrchr.cpp b/src/string/strrchr.cpp
new file mode 100644
index 0000000..28716c2
--- /dev/null
+++ b/src/string/strrchr.cpp
@@ -0,0 +1,28 @@
+//===-- Implementation of strrchr------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/string/strrchr.h"
+
+#include "src/__support/common.h"
+
+namespace __llvm_libc {
+
+char *LLVM_LIBC_ENTRYPOINT(strrchr)(const char *src, int c) {
+ unsigned char *str =
+ const_cast<unsigned char *>(reinterpret_cast<const unsigned char *>(src));
+ const unsigned char ch = c;
+
+ unsigned char *last_occurrence = nullptr;
+ do {
+ if (*str == ch)
+ last_occurrence = str;
+ } while (*str++);
+ return reinterpret_cast<char *>(last_occurrence);
+}
+
+} // namespace __llvm_libc
diff --git a/src/string/strrchr.h b/src/string/strrchr.h
new file mode 100644
index 0000000..7b85929
--- /dev/null
+++ b/src/string/strrchr.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for strrchr -----------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_STRING_STRRCHR_H
+#define LLVM_LIBC_SRC_STRING_STRRCHR_H
+
+namespace __llvm_libc {
+
+char *strrchr(const char *src, int c);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_STRING_STRRCHR_H
diff --git a/test/src/string/CMakeLists.txt b/test/src/string/CMakeLists.txt
index a116eff..0fff250 100644
--- a/test/src/string/CMakeLists.txt
+++ b/test/src/string/CMakeLists.txt
@@ -92,6 +92,16 @@
libc.src.string.memrchr
)
+add_libc_unittest(
+ strrchr_test
+ SUITE
+ libc_string_unittests
+ SRCS
+ strrchr_test.cpp
+ DEPENDS
+ libc.src.string.strrchr
+)
+
# Tests all implementations that can run on the host.
function(add_libc_multi_impl_test name)
get_property(fq_implementations GLOBAL PROPERTY ${name}_implementations)
diff --git a/test/src/string/strrchr_test.cpp b/test/src/string/strrchr_test.cpp
new file mode 100644
index 0000000..18fddda
--- /dev/null
+++ b/test/src/string/strrchr_test.cpp
@@ -0,0 +1,81 @@
+//===-- Unittests for strrchr ---------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/string/strrchr.h"
+#include "utils/UnitTest/Test.h"
+
+TEST(StrRChrTest, FindsFirstCharacter) {
+ const char *src = "abcde";
+ const char *src_copy = src;
+
+ // Should return original string since 'a' is the first character.
+ ASSERT_STREQ(__llvm_libc::strrchr(src, 'a'), "abcde");
+ // Source string should not change.
+ ASSERT_STREQ(src, src_copy);
+}
+
+TEST(StrRChrTest, FindsMiddleCharacter) {
+ const char *src = "abcde";
+ const char *src_copy = src;
+
+ // Should return characters after (and including) 'c'.
+ ASSERT_STREQ(__llvm_libc::strrchr(src, 'c'), "cde");
+ // Source string should not change.
+ ASSERT_STREQ(src, src_copy);
+}
+
+TEST(StrRChrTest, FindsLastCharacterThatIsNotNullTerminator) {
+ const char *src = "abcde";
+ const char *src_copy = src;
+
+ // Should return 'e' and null-terminator.
+ ASSERT_STREQ(__llvm_libc::strrchr(src, 'e'), "e");
+ // Source string should not change.
+ ASSERT_STREQ(src, src_copy);
+}
+
+TEST(StrRChrTest, FindsNullTerminator) {
+ const char *src = "abcde";
+ const char *src_copy = src;
+
+ // Should return null terminator.
+ ASSERT_STREQ(__llvm_libc::strrchr(src, '\0'), "");
+ // Source string should not change.
+ ASSERT_STREQ(src, src_copy);
+}
+
+TEST(StrRChrTest, FindsLastNullTerminator) {
+ const char src[5] = {'a', '\0', 'b', '\0', 'c'};
+ // 'b' is behind a null terminator, so should not be found.
+ ASSERT_STREQ(__llvm_libc::strrchr(src, 'b'), nullptr);
+ // Same goes for 'c'.
+ ASSERT_STREQ(__llvm_libc::strrchr(src, 'c'), nullptr);
+}
+
+TEST(StrRChrTest, CharacterNotWithinStringShouldReturnNullptr) {
+ // Since 'z' is not within the string, should return nullptr.
+ ASSERT_STREQ(__llvm_libc::strrchr("123?", 'z'), nullptr);
+}
+
+TEST(StrRChrTest, ShouldFindLastOfDuplicates) {
+ // '1' is duplicated in the string, but it should find the last copy.
+ ASSERT_STREQ(__llvm_libc::strrchr("abc1def1ghi", '1'), "1ghi");
+
+ const char *dups = "XXXXX";
+ // Should return the last occurrence of 'X'.
+ ASSERT_STREQ(__llvm_libc::strrchr(dups, 'X'), "X");
+}
+
+TEST(StrRChrTest, EmptyStringShouldOnlyMatchNullTerminator) {
+ // Null terminator should match.
+ ASSERT_STREQ(__llvm_libc::strrchr("", '\0'), "");
+ // All other characters should not match.
+ ASSERT_STREQ(__llvm_libc::strrchr("", 'A'), nullptr);
+ ASSERT_STREQ(__llvm_libc::strrchr("", '2'), nullptr);
+ ASSERT_STREQ(__llvm_libc::strrchr("", '*'), nullptr);
+}
