[libc] Add strlcat

[michaelrj]

libc/src/string/strlcat.cpp

19–20

this doesn't quite work because the return value always needs to be strlen(dst)+strlen(src). This means you always need to find the full length of dst.

libc/test/src/string/strlcat_test.cpp

34

as discussed above the return value of strlcat should always be strlen(dst)+strlen(src), so this should be 4.

[abrachet]

libc/src/string/strlcat.cpp

19–20

Described below

libc/test/src/string/strlcat_test.cpp

34

No because the buffer size was passed as 1, so strlcat only reads 1 char from buf and uses that as the size.

Per the man page "Note, however, that if strlcat() traverses size characters without finding a NUL, the length of the string is considered to be size and the destination string will not be NUL-terminated (since there was no space for the NUL)."

[michaelrj]

LGTM

libc/test/src/string/strlcat_test.cpp

34

oops, you're right. The source I was going off of was wrong, and this way matches the existing implementation.

[michaelrj]

libc/src/string/strlcat.cpp

23

nit: it looks like len is only used here, so you could move the call to string_length inside this if to save time on the other branch.

[sivachandra]

Just pointing out that the review thread is not getting copied to libc-commits.

libc/config/darwin/arm/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.string.memset
     libc.src.string.stpcpy
     libc.src.string.stpncpy
     libc.src.string.strcat
     libc.src.string.strchr
     libc.src.string.strcmp
     libc.src.string.strcpy
     libc.src.string.strcspn
+    libc.src.string.strlcat
     libc.src.string.strlcpy
     libc.src.string.strlen
     libc.src.string.strncat
     libc.src.string.strncmp
     libc.src.string.strncpy
     libc.src.string.strnlen
     libc.src.string.strpbrk
     libc.src.string.strrchr

libc/config/linux/aarch64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.string.memset
     libc.src.string.stpcpy
     libc.src.string.stpncpy
     libc.src.string.strcat
     libc.src.string.strchr
     libc.src.string.strcmp
     libc.src.string.strcpy
     libc.src.string.strcspn
+    libc.src.string.strlcat
     libc.src.string.strlcpy
     libc.src.string.strlen
     libc.src.string.strncat
     libc.src.string.strncmp
     libc.src.string.strncpy
     libc.src.string.strnlen
     libc.src.string.strpbrk
     libc.src.string.strrchr

libc/config/linux/x86_64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.string.memset
     libc.src.string.stpcpy
     libc.src.string.stpncpy
     libc.src.string.strcat
     libc.src.string.strchr
     libc.src.string.strcmp
     libc.src.string.strcpy
     libc.src.string.strcspn
+    libc.src.string.strlcat
     libc.src.string.strlcpy
     libc.src.string.strlen
     libc.src.string.strncat
     libc.src.string.strncmp
     libc.src.string.strncpy
     libc.src.string.strnlen
     libc.src.string.strpbrk
     libc.src.string.strrchr

libc/config/windows/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.string.memset
     libc.src.string.stpcpy
     libc.src.string.stpncpy
     libc.src.string.strcat
     libc.src.string.strchr
     libc.src.string.strcmp
     libc.src.string.strcpy
     libc.src.string.strcspn
+    libc.src.string.strlcat
     libc.src.string.strlcpy
     libc.src.string.strlen
     libc.src.string.strncat
     libc.src.string.strncmp
     libc.src.string.strncpy
     libc.src.string.strnlen
     libc.src.string.strpbrk
     libc.src.string.strrchr

libc/spec/bsd_ext.td

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

libc/src/string/CMakeLists.txt

 add_subdirectory(memory_utils)
 
 add_header_library(
   string_utils
   HDRS
     string_utils.h
   DEPENDS
     libc.src.__support.CPP.bitset
+    .memory_utils.memcpy_implementation
+    .memory_utils.memset_implementation
 )
 
 add_entrypoint_object(
   memccpy
   SRCS
     memccpy.cpp
   HDRS
     memccpy.h
HDRS
     strdup.h
   DEPENDS
     .memory_utils.memcpy_implementation
     .string_utils
     libc.include.stdlib
 )
 
 add_entrypoint_object(
+  strlcat
+  SRCS
+    strlcat.cpp
+  HDRS
+    strlcat.h
+  DEPENDS
+    .string_utils
+    libc.include.string
+)
+
+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
     strlen.cpp

libc/src/string/string_utils.h

 //===-- String utils --------------------------------------------*- 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 LIBC_SRC_STRING_STRING_UTILS_H
 #define LIBC_SRC_STRING_STRING_UTILS_H
 
 #include "src/__support/CPP/Bitset.h"
 #include "src/__support/common.h"
+#include "src/string/memory_utils/memcpy_implementations.h"
+#include "src/string/memory_utils/memset_implementations.h"
 #include <stddef.h> // size_t
 
 namespace __llvm_libc {
 namespace internal {
 
 // Returns the length of a string, denoted by the first occurrence
 // of a null terminator.
 static inline size_t string_length(const char *src) {
if (delimiter_set.test(*src)) {
       ++src;
       break;
     }
   }
   *saveptr = src;
   return token;
 }
 
+static inline 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 internal
 } // namespace __llvm_libc
 
 #endif //  LIBC_SRC_STRING_STRING_UTILS_H

libc/src/string/strlcat.h

+//===-- Implementation header for strlcat -----------------------*- 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_STRLCAT_H
+#define LLVM_LIBC_SRC_STRING_STRLCAT_H
+
+#include <string.h>
+
+namespace __llvm_libc {
+
+size_t strlcat(char *__restrict dst, const char *__restrict src, size_t size);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_STRING_STRLCAT_H

libc/src/string/strlcat.cpp

-//===-- Implementation of strlcpy -----------------------------------------===//
+//===-- Implementation of strlcat -----------------------------------------===//
 //
 // 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/strlcat.h"
 #include "src/string/string_utils.h"
 
 #include "src/__support/common.h"
 
 namespace __llvm_libc {
 
-LLVM_LIBC_FUNCTION(size_t, strlcpy,
+LLVM_LIBC_FUNCTION(size_t, strlcat,
                    (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;
+  char *new_dst = reinterpret_cast<char *>(internal::find_first_character(
+      reinterpret_cast<unsigned char *>(dst), 0, size));
+  if (!new_dst)
+    return size + internal::string_length(src);
+  size_t first_len = new_dst - dst;
+  return first_len + internal::strlcpy(new_dst, src, size - first_len);
 }
 
 } // namespace __llvm_libc

libc/src/string/strlcpy.cpp

 //===-- 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;
+  return internal::strlcpy(dst, src, size);
 }
 
 } // namespace __llvm_libc

libc/test/src/string/CMakeLists.txt

add_libc_unittest(
   SRCS
     strdup_test.cpp
   DEPENDS
     libc.include.stdlib
     libc.src.string.strdup
 )
 
 add_libc_unittest(
+  strlcat_test
+  SUITE
+    libc_string_unittests
+  SRCS
+    strlcat_test.cpp
+  DEPENDS
+    libc.src.string.strlcat
+)
+
+add_libc_unittest(
   strlcpy_test
   SUITE
     libc_string_unittests
   SRCS
     strlcpy_test.cpp
   DEPENDS
     libc.src.string.strlcpy
 )

libc/test/src/string/strlcat_test.cpp

+//===-- Unittests for strlcat ---------------------------------------------===//
+//
+// 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/strlcat.h"
+#include "utils/UnitTest/Test.h"
+#include <stdlib.h>
+
+TEST(LlvmLibcStrlcatTest, TooBig) {
+  const char *str = "cd";
+  char buf[4]{"ab"};
+  EXPECT_EQ(__llvm_libc::strlcat(buf, str, 3), size_t(4));
+  EXPECT_STREQ(buf, "ab");
+  EXPECT_EQ(__llvm_libc::strlcat(buf, str, 4), size_t(4));
+  EXPECT_STREQ(buf, "abc");
+}
+
+TEST(LlvmLibcStrlcatTest, Smaller) {
+  const char *str = "cd";
+  char buf[7]{"ab"};
+
+  EXPECT_EQ(__llvm_libc::strlcat(buf, str, 7), size_t(4));
+  EXPECT_STREQ(buf, "abcd");
+}
+
+TEST(LlvmLibcStrlcatTest, No0) {
+  const char *str = "cd";
+  char buf[7]{"ab"};
+  EXPECT_EQ(__llvm_libc::strlcat(buf, str, 1), size_t(3));
+  EXPECT_STREQ(buf, "ab");
+  EXPECT_EQ(__llvm_libc::strlcat(buf, str, 2), size_t(4));
+  EXPECT_STREQ(buf, "ab");
+}