[libc-commits] [libc] c6d03b5 - [libc] add strncmp to strings
Michael Jones via libc-commits
libc-commits at lists.llvm.org
Wed Jul 28 14:37:17 PDT 2021
Author: Michael Jones
Date: 2021-07-28T21:37:12Z
New Revision: c6d03b583b48c00171e79d3bcf61168c97f874b9
URL: https://github.com/llvm/llvm-project/commit/c6d03b583b48c00171e79d3bcf61168c97f874b9
DIFF: https://github.com/llvm/llvm-project/commit/c6d03b583b48c00171e79d3bcf61168c97f874b9.diff
LOG: [libc] add strncmp to strings
Add strncmp as a function to strings.h. Also adds unit tests, and adds
strncmp as an entrypoint for all current platforms.
Reviewed By: sivachandra
Differential Revision: https://reviews.llvm.org/D106901
Added:
libc/src/string/strncmp.cpp
libc/src/string/strncmp.h
libc/test/src/string/strncmp_test.cpp
Modified:
libc/config/linux/aarch64/entrypoints.txt
libc/config/linux/x86_64/entrypoints.txt
libc/config/windows/entrypoints.txt
libc/src/string/CMakeLists.txt
libc/test/src/string/CMakeLists.txt
Removed:
################################################################################
diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
index 95e8b8c637578..21bbaa466e4bb 100644
--- a/libc/config/linux/aarch64/entrypoints.txt
+++ b/libc/config/linux/aarch64/entrypoints.txt
@@ -34,6 +34,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.string.strcmp
libc.src.string.strcspn
libc.src.string.strlen
+ libc.src.string.strncmp
libc.src.string.strncpy
libc.src.string.strnlen
libc.src.string.strpbrk
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 5143864e013bf..6e9d991d25320 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -34,6 +34,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.string.strcpy
libc.src.string.strcspn
libc.src.string.strlen
+ libc.src.string.strncmp
libc.src.string.strncpy
libc.src.string.strnlen
libc.src.string.strpbrk
diff --git a/libc/config/windows/entrypoints.txt b/libc/config/windows/entrypoints.txt
index 38892340e915a..76c90e1f9bf0d 100644
--- a/libc/config/windows/entrypoints.txt
+++ b/libc/config/windows/entrypoints.txt
@@ -30,6 +30,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.string.strcmp
libc.src.string.strcspn
libc.src.string.strlen
+ libc.src.string.strncmp
libc.src.string.strncpy
libc.src.string.strnlen
libc.src.string.strpbrk
diff --git a/libc/src/string/CMakeLists.txt b/libc/src/string/CMakeLists.txt
index 4788baf1966e4..a7dbac375d2ea 100644
--- a/libc/src/string/CMakeLists.txt
+++ b/libc/src/string/CMakeLists.txt
@@ -48,6 +48,14 @@ add_entrypoint_object(
strcmp.h
)
+add_entrypoint_object(
+ strncmp
+ SRCS
+ strncmp.cpp
+ HDRS
+ strncmp.h
+)
+
add_entrypoint_object(
memchr
SRCS
diff --git a/libc/src/string/strncmp.cpp b/libc/src/string/strncmp.cpp
new file mode 100644
index 0000000000000..94960e509d635
--- /dev/null
+++ b/libc/src/string/strncmp.cpp
@@ -0,0 +1,32 @@
+//===-- Implementation of strncmp -----------------------------------------===//
+//
+// 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/strncmp.h"
+
+#include "src/__support/common.h"
+#include <stddef.h>
+
+namespace __llvm_libc {
+
+// TODO: Look at benefits for comparing words at a time.
+LLVM_LIBC_FUNCTION(int, strncmp,
+ (const char *left, const char *right, size_t n)) {
+
+ if (n == 0)
+ return 0;
+
+ for (; n > 1; --n, ++left, ++right) {
+ char lc = *left;
+ if (lc == '\0' || lc != *right)
+ break;
+ }
+ return *reinterpret_cast<const unsigned char *>(left) -
+ *reinterpret_cast<const unsigned char *>(right);
+}
+
+} // namespace __llvm_libc
diff --git a/libc/src/string/strncmp.h b/libc/src/string/strncmp.h
new file mode 100644
index 0000000000000..056fe78e6c85c
--- /dev/null
+++ b/libc/src/string/strncmp.h
@@ -0,0 +1,20 @@
+//===-- Implementation header for strncmp -----------------------*- 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_STRNCMP_H
+#define LLVM_LIBC_SRC_STRING_STRNCMP_H
+
+#include <stddef.h>
+
+namespace __llvm_libc {
+
+int strncmp(const char *left, const char *right, size_t n);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_STRING_STRNCMP_H
diff --git a/libc/test/src/string/CMakeLists.txt b/libc/test/src/string/CMakeLists.txt
index dbf390d561c02..ee9121094fea3 100644
--- a/libc/test/src/string/CMakeLists.txt
+++ b/libc/test/src/string/CMakeLists.txt
@@ -42,6 +42,16 @@ add_libc_unittest(
libc.src.string.strcmp
)
+add_libc_unittest(
+ strncmp_test
+ SUITE
+ libc_string_unittests
+ SRCS
+ strncmp_test.cpp
+ DEPENDS
+ libc.src.string.strncmp
+)
+
add_libc_unittest(
memchr_test
SUITE
diff --git a/libc/test/src/string/strncmp_test.cpp b/libc/test/src/string/strncmp_test.cpp
new file mode 100644
index 0000000000000..8855e0f59db0a
--- /dev/null
+++ b/libc/test/src/string/strncmp_test.cpp
@@ -0,0 +1,158 @@
+//===-- Unittests for strncmp ---------------------------------------------===//
+//
+// 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/strncmp.h"
+#include "utils/UnitTest/Test.h"
+
+// This group is just copies of the strcmp tests, since all the same cases still
+// need to be tested.
+
+TEST(LlvmLibcStrNCmpTest, EmptyStringsShouldReturnZeroWithSufficientLength) {
+ const char *s1 = "";
+ const char *s2 = "";
+ int result = __llvm_libc::strncmp(s1, s2, 1);
+ ASSERT_EQ(result, 0);
+
+ // Verify operands reversed.
+ result = __llvm_libc::strncmp(s2, s1, 1);
+ ASSERT_EQ(result, 0);
+}
+
+TEST(LlvmLibcStrNCmpTest,
+ EmptyStringShouldNotEqualNonEmptyStringWithSufficientLength) {
+ const char *empty = "";
+ const char *s2 = "abc";
+ int result = __llvm_libc::strncmp(empty, s2, 3);
+ // This should be '\0' - 'a' = -97
+ ASSERT_EQ(result, -97);
+
+ // Similar case if empty string is second argument.
+ const char *s3 = "123";
+ result = __llvm_libc::strncmp(s3, empty, 3);
+ // This should be '1' - '\0' = 49
+ ASSERT_EQ(result, 49);
+}
+
+TEST(LlvmLibcStrNCmpTest, EqualStringsShouldReturnZeroWithSufficientLength) {
+ const char *s1 = "abc";
+ const char *s2 = "abc";
+ int result = __llvm_libc::strncmp(s1, s2, 3);
+ ASSERT_EQ(result, 0);
+
+ // Verify operands reversed.
+ result = __llvm_libc::strncmp(s2, s1, 3);
+ ASSERT_EQ(result, 0);
+}
+
+TEST(LlvmLibcStrNCmpTest,
+ ShouldReturnResultOfFirstDifferenceWithSufficientLength) {
+ const char *s1 = "___B42__";
+ const char *s2 = "___C55__";
+ int result = __llvm_libc::strncmp(s1, s2, 8);
+ // This should return 'B' - 'C' = -1.
+ ASSERT_EQ(result, -1);
+
+ // Verify operands reversed.
+ result = __llvm_libc::strncmp(s2, s1, 8);
+ // This should return 'C' - 'B' = 1.
+ ASSERT_EQ(result, 1);
+}
+
+TEST(LlvmLibcStrNCmpTest,
+ CapitalizedLetterShouldNotBeEqualWithSufficientLength) {
+ const char *s1 = "abcd";
+ const char *s2 = "abCd";
+ int result = __llvm_libc::strncmp(s1, s2, 4);
+ // 'c' - 'C' = 32.
+ ASSERT_EQ(result, 32);
+
+ // Verify operands reversed.
+ result = __llvm_libc::strncmp(s2, s1, 4);
+ // 'C' - 'c' = -32.
+ ASSERT_EQ(result, -32);
+}
+
+TEST(LlvmLibcStrNCmpTest,
+ UnequalLengthStringsShouldNotReturnZeroWithSufficientLength) {
+ const char *s1 = "abc";
+ const char *s2 = "abcd";
+ int result = __llvm_libc::strncmp(s1, s2, 4);
+ // '\0' - 'd' = -100.
+ ASSERT_EQ(result, -100);
+
+ // Verify operands reversed.
+ result = __llvm_libc::strncmp(s2, s1, 4);
+ // 'd' - '\0' = 100.
+ ASSERT_EQ(result, 100);
+}
+
+TEST(LlvmLibcStrNCmpTest, StringArgumentSwapChangesSignWithSufficientLength) {
+ const char *a = "a";
+ const char *b = "b";
+ int result = __llvm_libc::strncmp(b, a, 1);
+ // 'b' - 'a' = 1.
+ ASSERT_EQ(result, 1);
+
+ result = __llvm_libc::strncmp(a, b, 1);
+ // 'a' - 'b' = -1.
+ ASSERT_EQ(result, -1);
+}
+
+// This group is actually testing strncmp functionality
+
+TEST(LlvmLibcStrNCmpTest, NonEqualStringsEqualWithLengthZero) {
+ const char *s1 = "abc";
+ const char *s2 = "def";
+ int result = __llvm_libc::strncmp(s1, s2, 0);
+ ASSERT_EQ(result, 0);
+
+ // Verify operands reversed.
+ result = __llvm_libc::strncmp(s2, s1, 0);
+ ASSERT_EQ(result, 0);
+}
+
+TEST(LlvmLibcStrNCmpTest, NonEqualStringsNotEqualWithLengthOne) {
+ const char *s1 = "abc";
+ const char *s2 = "def";
+ int result = __llvm_libc::strncmp(s1, s2, 1);
+ ASSERT_EQ(result, -3);
+
+ // Verify operands reversed.
+ result = __llvm_libc::strncmp(s2, s1, 1);
+ ASSERT_EQ(result, 3);
+}
+
+TEST(LlvmLibcStrNCmpTest, NonEqualStringsEqualWithShorterLength) {
+ const char *s1 = "___B42__";
+ const char *s2 = "___C55__";
+ int result = __llvm_libc::strncmp(s1, s2, 3);
+ ASSERT_EQ(result, 0);
+
+ // This should return 'B' - 'C' = -1.
+ result = __llvm_libc::strncmp(s1, s2, 4);
+ ASSERT_EQ(result, -1);
+
+ // Verify operands reversed.
+ result = __llvm_libc::strncmp(s2, s1, 3);
+ ASSERT_EQ(result, 0);
+
+ // This should return 'C' - 'B' = 1.
+ result = __llvm_libc::strncmp(s2, s1, 4);
+ ASSERT_EQ(result, 1);
+}
+
+TEST(LlvmLibcStrNCmpTest, StringComparisonEndsOnNullByteEvenWithLongerLength) {
+ const char *s1 = "abc\0def";
+ const char *s2 = "abc\0abc";
+ int result = __llvm_libc::strncmp(s1, s2, 7);
+ ASSERT_EQ(result, 0);
+
+ // Verify operands reversed.
+ result = __llvm_libc::strncmp(s2, s1, 7);
+ ASSERT_EQ(result, 0);
+}
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