[libc] Add ctime_s

Resolves llvm#110548

Definition:

```c++
int ctime_s(char *buffer, size_t buffer_size, const time_t *t_ptr);

```

Author: Rajveer100

libc/config/baremetal/arm/entrypoints.txt

@@ -205,6 +205,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.time.asctime_r
     libc.src.time.ctime
     libc.src.time.ctime_r
+    libc.src.time.ctime_s
     libc.src.time.difftime
     libc.src.time.gmtime
     libc.src.time.gmtime_r

libc/config/baremetal/riscv/entrypoints.txt

@@ -201,6 +201,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.time.asctime_r
     libc.src.time.ctime
     libc.src.time.ctime_r
+    libc.src.time.ctime_s
     libc.src.time.difftime
     libc.src.time.gmtime
     libc.src.time.gmtime_r

libc/config/linux/aarch64/entrypoints.txt

@@ -969,6 +969,7 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.time.asctime_r
     libc.src.time.ctime
     libc.src.time.ctime_r
+    libc.src.time.ctime_s
     libc.src.time.clock
     libc.src.time.clock_gettime
     libc.src.time.difftime

libc/config/linux/riscv/entrypoints.txt

@@ -901,6 +901,7 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.time.asctime_r
     libc.src.time.ctime
     libc.src.time.ctime_r
+    libc.src.time.ctime_s
     libc.src.time.clock
     libc.src.time.clock_gettime
     libc.src.time.difftime

libc/config/linux/x86_64/entrypoints.txt

@@ -1026,6 +1026,7 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.time.asctime_r
     libc.src.time.ctime
     libc.src.time.ctime_r
+    libc.src.time.ctime_s
     libc.src.time.clock
     libc.src.time.clock_gettime
     libc.src.time.difftime

libc/docs/date_and_time.rst

@@ -59,6 +59,8 @@ Implementation Status
 +---------------------+---------+---------+---------+-----------------+---------+---------+---------+---------+---------+---------+---------+---------+
 | ctime_r             | |check| | |check| |         |     |check|     |         |         |         |         |         |         |         |         |
 +---------------------+---------+---------+---------+-----------------+---------+---------+---------+---------+---------+---------+---------+---------+
+| ctime_s             | |check| | |check| |         |     |check|     |         |         |         |         |         |         |         |         |
++---------------------+---------+---------+---------+-----------------+---------+---------+---------+---------+---------+---------+---------+---------+
 | clock               | |check| | |check| |         |     |check|     |         |         |         |         |         |         |         |         |
 +---------------------+---------+---------+---------+-----------------+---------+---------+---------+---------+---------+---------+---------+---------+
 | clock_getcpuclockid |         |         |         |                 |         |         |         |         |         |         |         |         |

libc/include/llvm-libc-types/rsize_t.h

@@ -0,0 +1,16 @@
+//===-- Definition of rsize_t type ----------------------------------------===//
+//
+// 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_TYPES_RSIZE_T_H
+#define LLVM_LIBC_TYPES_RSIZE_T_H
+
+#include <stddef.h>
+
+typedef size_t rsize_t;
+
+#endif // LLVM_LIBC_TYPES_RSIZE_T_H

libc/newhdrgen/yaml/time.yaml

@@ -37,6 +37,14 @@ functions:
     arguments:
       - type: const time_t *
       - type: char *
+  - name: ctime_s
+    standard:
+      - stdc
+    return_type: int
+    arguments:
+      - type: char *
+      - type: size_t
+      - type: const time_t *
   - name: clock
     standard:
       - stdc

libc/spec/stdc.td

@@ -1630,6 +1630,15 @@ def StdC : StandardSpec<"stdc"> {
                   ArgSpec<CharPtr>,
               ]
           >,
+          FunctionSpec<
+              "ctime_s",
+              RetValSpec<IntType>,
+              [
+                  ArgSpec<CharPtr>,
+                  ArgSpec<SizeTType>,
+                  ArgSpec<ConstTimeTTypePtr>,
+              ]
+          >,
           FunctionSpec<
               "clock",
               RetValSpec<ClockT>,

libc/src/time/CMakeLists.txt

@@ -60,6 +60,18 @@ add_entrypoint_object(
     libc.include.time
 )
 
+add_entrypoint_object(
+  ctime_s
+  SRCS
+    ctime_s.cpp
+  HDRS
+    ctime_s.h
+  DEPENDS
+    .time_utils
+    libc.hdr.types.time_t
+    libc.include.time
+)
+
 add_entrypoint_object(
   difftime
   SRCS

libc/src/time/ctime_s.cpp

@@ -0,0 +1,43 @@
+//===-- Implementation of ctime_s function --------------------------------===//
+//
+// 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 "ctime_s.h"
+#include "hdr/errno_macros.h"
+#include "src/__support/CPP/limits.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "time_utils.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+using LIBC_NAMESPACE::time_utils::TimeConstants;
+
+LLVM_LIBC_FUNCTION(int, ctime_s,
+                   (char *buffer, rsize_t buffer_size, const time_t *t_ptr)) {
+  if (t_ptr == nullptr || buffer == nullptr ||
+      *t_ptr > cpp::numeric_limits<int32_t>::max()) {
+    if (buffer != nullptr)
+      buffer[0] = '\0';
+    return EINVAL;
+  }
+
+  if (buffer_size < TimeConstants::ASCTIME_MAX_BYTES) {
+    buffer[0] = '\0';
+    return ERANGE;
+  }
+
+  if (time_utils::asctime(time_utils::localtime(t_ptr), buffer, buffer_size) ==
+      nullptr) {
+    buffer[0] = '\0';
+    return EINVAL;
+  }
+
+  return 0;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/time/ctime_s.h

@@ -0,0 +1,23 @@
+//===-- Implementation header of ctime_s ------------------------*- 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_TIME_CTIME_S_H
+#define LLVM_LIBC_SRC_TIME_CTIME_S_H
+
+#include "hdr/types/time_t.h"
+#include "include/llvm-libc-types/rsize_t.h"
+#include "src/__support/macros/config.h"
+#include <stddef.h>
+
+namespace LIBC_NAMESPACE_DECL {
+
+int ctime_s(char *buffer, rsize_t buffer_size, const time_t *t_ptr);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_TIME_CTIME_S_H

libc/test/src/time/CMakeLists.txt

@@ -66,6 +66,24 @@ add_libc_unittest(
     libc.src.time.time_utils
 )
 
+add_libc_unittest(
+  ctime_s_test
+  SUITE
+    libc_time_unittests
+  SRCS
+    ctime_s_test.cpp
+  HDRS
+    TmHelper.h
+    TmMatcher.h
+  CXX_STANDARD
+    20
+  DEPENDS
+    libc.include.time
+    libc.hdr.types.time_t
+    libc.src.time.ctime_s
+    libc.src.time.time_utils
+)
+
 add_libc_test(
   clock_gettime_test
   SUITE

libc/test/src/time/ctime_s_test.cpp

@@ -0,0 +1,61 @@
+//===-- Unittests for ctime_s ---------------------------------------------===//
+//
+// 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 "hdr/errno_macros.h"
+#include "src/errno/libc_errno.h"
+#include "src/time/ctime_s.h"
+#include "src/time/time_utils.h"
+#include "test/UnitTest/Test.h"
+#include "test/src/time/TmHelper.h"
+
+using LIBC_NAMESPACE::time_utils::TimeConstants;
+
+TEST(LlvmLibcCtimeS, Nullptr) {
+  int result;
+  result = LIBC_NAMESPACE::ctime_s(nullptr, 0, nullptr);
+  ASSERT_EQ(EINVAL, result);
+
+  char buffer[TimeConstants::ASCTIME_BUFFER_SIZE];
+  result = LIBC_NAMESPACE::ctime_s(buffer, sizeof(buffer), nullptr);
+  ASSERT_EQ(EINVAL, result);
+
+  time_t t;
+  result = LIBC_NAMESPACE::ctime_s(nullptr, 0, &t);
+  ASSERT_EQ(EINVAL, result);
+}
+
+TEST(LlvmLibcCtimeS, ValidUnixTimestamp0) {
+  char buffer[TimeConstants::ASCTIME_BUFFER_SIZE];
+  time_t t;
+  int result;
+  // 1970-01-01 00:00:00. Test with a valid buffer size.
+  t = 0;
+  result = LIBC_NAMESPACE::ctime_s(buffer, sizeof(buffer), &t);
+  ASSERT_STREQ("Thu Jan  1 00:00:00 1970\n", buffer);
+  ASSERT_EQ(0, result);
+}
+
+TEST(LlvmLibcCtimeS, ValidUnixTimestamp32Int) {
+  char buffer[TimeConstants::ASCTIME_BUFFER_SIZE];
+  time_t t;
+  int result;
+  // 2038-01-19 03:14:07. Test with a valid buffer size.
+  t = 2147483647;
+  result = LIBC_NAMESPACE::ctime_s(buffer, sizeof(buffer), &t);
+  ASSERT_STREQ("Tue Jan 19 03:14:07 2038\n", buffer);
+  ASSERT_EQ(0, result);
+}
+
+TEST(LlvmLibcCtimeS, InvalidArgument) {
+  char buffer[TimeConstants::ASCTIME_BUFFER_SIZE];
+  time_t t;
+  int result;
+  t = 2147483648;
+  result = LIBC_NAMESPACE::ctime_s(buffer, sizeof(buffer), &t);
+  ASSERT_EQ(EINVAL, result);
+}