[libc] Add strlcpy

Differential Revision: https://reviews.llvm.org/D125806

libc/config/darwin/arm/entrypoints.txt

@@ -35,6 +35,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.string.strcmp
     libc.src.string.strcpy
     libc.src.string.strcspn
+    libc.src.string.strlcpy
     libc.src.string.strlen
     libc.src.string.strncat
     libc.src.string.strncmp

libc/config/linux/aarch64/entrypoints.txt

@@ -40,6 +40,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.string.strcmp
     libc.src.string.strcpy
     libc.src.string.strcspn
+    libc.src.string.strlcpy
     libc.src.string.strlen
     libc.src.string.strncat
     libc.src.string.strncmp

libc/config/linux/api.td

@@ -1,5 +1,6 @@
 include "config/public_api.td"
 
+include "spec/bsd_ext.td"
 include "spec/gnu_ext.td"
 include "spec/linux.td"
 include "spec/llvm_libc_ext.td"

libc/config/linux/x86_64/entrypoints.txt

@@ -40,6 +40,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.string.strcmp
     libc.src.string.strcpy
     libc.src.string.strcspn
+    libc.src.string.strlcpy
     libc.src.string.strlen
     libc.src.string.strncat
     libc.src.string.strncmp

libc/config/windows/entrypoints.txt

@@ -35,6 +35,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.string.strcmp
     libc.src.string.strcpy
     libc.src.string.strcspn
+    libc.src.string.strlcpy
     libc.src.string.strlen
     libc.src.string.strncat
     libc.src.string.strncmp

libc/spec/bsd_ext.td

@@ -0,0 +1,15 @@
+def BsdExtensions : StandardSpec<"BSDExtensions"> {
+  HeaderSpec String = HeaderSpec<
+      "string.h",
+      [], // Macros
+      [], // Types
+      [], // Enumerations
+      [ 
+        FunctionSpec<
+            "strlcpy",
+            RetValSpec<SizeTType>,
+            [ArgSpec<CharPtr>, ArgSpec<ConstCharPtr>, ArgSpec<SizeTType>]
+        >,
+      ]
+  >;
+}

libc/src/string/CMakeLists.txt

@@ -126,6 +126,19 @@ add_entrypoint_object(
     libc.include.stdlib
 )
 
+add_entrypoint_object(
+  strlcpy
+  SRCS
+    strlcpy.cpp
+  HDRS
+    strlcpy.h
+  DEPENDS
+    .memory_utils.memcpy_implementation
+    .memory_utils.memset_implementation
+    .string_utils
+    libc.include.string
+)
+
 add_entrypoint_object(
   strlen
   SRCS

libc/src/string/strlcpy.cpp

@@ -0,0 +1,31 @@
+//===-- Implementation of strlcpy -----------------------------------------===//
+//
+// 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/strlcpy.h"
+#include "src/string/bzero.h"
+#include "src/string/memory_utils/memcpy_implementations.h"
+#include "src/string/memory_utils/memset_implementations.h"
+#include "src/string/string_utils.h"
+
+#include "src/__support/common.h"
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(size_t, strlcpy,
+                   (char *__restrict dst, const char *__restrict src,
+                    size_t size)) {
+  size_t len = internal::string_length(src);
+  if (!size)
+    return len;
+  size_t n = len < size - 1 ? len : size - 1;
+  inline_memcpy(dst, src, n);
+  inline_memset(dst + n, 0, size - n);
+  return len;
+}
+
+} // namespace __llvm_libc

libc/src/string/strlcpy.h

@@ -0,0 +1,20 @@
+//===-- Implementation header for strlcpy -----------------------*- 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_STRLCPY_H
+#define LLVM_LIBC_SRC_STRING_STRLCPY_H
+
+#include <string.h>
+
+namespace __llvm_libc {
+
+size_t strlcpy(char *__restrict dst, const char *__restrict src, size_t size);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_STRING_STRLCPY_H

libc/test/src/string/CMakeLists.txt

@@ -123,6 +123,16 @@ add_libc_unittest(
     libc.src.string.strdup
 )
 
+add_libc_unittest(
+  strlcpy_test
+  SUITE
+    libc_string_unittests
+  SRCS
+    strlcpy_test.cpp
+  DEPENDS
+    libc.src.string.strlcpy
+)
+
 add_libc_unittest(
   strlen_test
   SUITE

libc/test/src/string/strlcpy_test.cpp

@@ -0,0 +1,30 @@
+//===-- Unittests for strlcpy ---------------------------------------------===//
+//
+// 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/strlcpy.h"
+#include "utils/UnitTest/Test.h"
+#include <stdlib.h>
+
+TEST(LlvmLibcStrlcpyTest, TooBig) {
+  const char *str = "abc";
+  char buf[2];
+  EXPECT_EQ(__llvm_libc::strlcpy(buf, str, 2), 3ul);
+  EXPECT_STREQ(buf, "a");
+
+  EXPECT_EQ(__llvm_libc::strlcpy(nullptr, str, 0), 3ul);
+}
+
+TEST(LlvmLibcStrlcpyTest, Smaller) {
+  const char *str = "abc";
+  char buf[7]{"111111"};
+
+  EXPECT_EQ(__llvm_libc::strlcpy(buf, str, 7), 3ul);
+  EXPECT_STREQ(buf, "abc");
+  for (const char *p = buf + 3; p < buf + 7; p++)
+    EXPECT_EQ(*p, '\0');
+}