[libc] Introduces localtime to LLVM libc, based on C99/C2X/Single Unix Sp.

[rtenneti]

Summary

This change doesn't handle TIMEZONE, tm_isdst and leap seconds.

localtime and gmtime share the same common code. They call update_from_seconds.
Thus added only validation tests for localtime.

[jeffbailey]

I don't think landing this without it having any way of displaying a different time than gmtime is a good idea. Happily, I started working on the TZ patch again, so this might be good to land early in the year.

[rtenneti]

Thanks Jeff. I have taken this CL off of reviewers.

[rtenneti]

Added locatime_r function and its tests.

libc/config/linux/aarch64/entrypoints.txt

list(APPEND TARGET_LIBC_ENTRYPOINTS
     libc.src.time.asctime
     libc.src.time.asctime_r
     libc.src.time.clock_gettime
     libc.src.time.clock
     libc.src.time.difftime
     libc.src.time.gettimeofday
     libc.src.time.gmtime
     libc.src.time.gmtime_r
+    libc.src.time.localtime
+    libc.src.time.localtime_r
     libc.src.time.mktime
     libc.src.time.nanosleep
     libc.src.time.time
 
     # unistd.h entrypoints
     libc.src.unistd.environ
     libc.src.unistd.execv
     libc.src.unistd.getopt

libc/config/linux/x86_64/entrypoints.txt

list(APPEND TARGET_LIBC_ENTRYPOINTS
     libc.src.time.asctime
     libc.src.time.asctime_r
     libc.src.time.clock_gettime
     libc.src.time.clock
     libc.src.time.difftime
     libc.src.time.gettimeofday
     libc.src.time.gmtime
     libc.src.time.gmtime_r
+    libc.src.time.localtime
+    libc.src.time.localtime_r
     libc.src.time.mktime
     libc.src.time.nanosleep
     libc.src.time.time
 
     # unistd.h entrypoints
     libc.src.unistd.environ
     libc.src.unistd.execv
     libc.src.unistd.fork

libc/docs/date_and_time.rst

 Function_Name C99
 ============= =======
 clock
 mktime        |check|
 time
 asctime       |check|
 ctime
 gmtime        |check|
-localtime
+localtime     |check|
 strftime
 ============= =======
 
 ===================   =======
 Function_Name         POSIX
 ===================   =======
 asctime               |check|
 asctime_r             |check|
 clock
 clock_getcpuclockid
 clock_getres
 clock_gettime         |check|
 clock_nanosleep
 clock_settime
 ctime
 ctime_r
 difftime              |check|
 getdate
 gettimeofday          |check|
 gmtime                |check|
 gmtime_r              |check|
-localtime
-localtime_r
+localtime             |check|
+localtime_r           |check|
 mktime                |check|
 nanosleep             |check|
 strftime
 strptime
 time
 timer_create
 timer_delete
 timer_gettime
 timer_getoverrun
 timer_settime
 tzset
 ===================   =======
 

libc/spec/stdc.td

HeaderSpec Time = HeaderSpec<
               "gmtime_r",
               RetValSpec<StructTmPtr>,
               [
                   ArgSpec<TimeTTypePtr>,
                   ArgSpec<StructTmPtr>,
               ]
           >,
           FunctionSpec<
+              "localtime",
+              RetValSpec<StructTmPtr>,
+              [ArgSpec<TimeTTypePtr>]
+          >,
+          FunctionSpec<
+              "localtime_r",
+              RetValSpec<StructTmPtr>,
+              [
+                  ArgSpec<TimeTTypePtr>,
+                  ArgSpec<StructTmPtr>,
+              ]
+          >,
+          FunctionSpec<
               "mktime",
               RetValSpec<TimeTType>,
               [ArgSpec<StructTmPtr>]
           >,
           FunctionSpec<
               "time",
               RetValSpec<TimeTType>,
               [ArgSpec<TimeTTypePtr>]

libc/src/time/CMakeLists.txt

add_entrypoint_object(
   HDRS
     gmtime_r.h
   DEPENDS
     .time_utils
     libc.include.time
 )
 
 add_entrypoint_object(
+  localtime
+  SRCS
+    localtime.cpp
+  HDRS
+    localtime.h
+  DEPENDS
+    .time_utils
+    libc.include.time
+)
+
+add_entrypoint_object(
+  localtime_r
+  SRCS
+    localtime_r.cpp
+  HDRS
+    localtime_r.h
+  DEPENDS
+    .time_utils
+    libc.include.time
+)
+
+add_entrypoint_object(
   mktime
   SRCS
     mktime.cpp
   HDRS
     mktime.h
   DEPENDS
     .time_utils
     libc.include.errno

libc/src/time/localtime.h

+//===-- Implementation header of localtime ----------------------*- 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_LOCALTIME_H
+#define LLVM_LIBC_SRC_TIME_LOCALTIME_H
+
+#include <time.h>
+
+namespace __llvm_libc {
+
+struct tm *localtime(const time_t *timer);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_TIME_LOCALTIME_H
+
+#include "include/time.h"

libc/src/time/localtime.cpp

+//===-- Implementation of localtime 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 "src/time/localtime.h"
+#include "src/__support/common.h"
+#include "src/time/time_utils.h"
+
+#include <limits.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(struct tm *, localtime, (const time_t *timer)) {
+  static struct tm tm_out;
+  return time_utils::localtime_internal(timer, &tm_out);
+}
+
+} // namespace __llvm_libc

libc/src/time/localtime_r.h

+//===-- Implementation header of localtime_r --------------------*- 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_LOCALTIME_R_H
+#define LLVM_LIBC_SRC_TIME_LOCALTIME_R_H
+
+#include <time.h>
+
+namespace __llvm_libc {
+
+struct tm *localtime_r(const time_t *timer, struct tm *result);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_TIME_LOCALTIME_R_H
+
+#include "include/time.h"

libc/src/time/localtime_r.cpp

+//===-- Implementation of localtime_r 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 "src/time/localtime_r.h"
+#include "src/__support/common.h"
+#include "src/time/time_utils.h"
+
+#include <limits.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(struct tm *, localtime_r,
+                   (const time_t *timer, struct tm *result)) {
+  return time_utils::localtime_internal(timer, result);
+}
+
+} // namespace __llvm_libc

libc/src/time/time_utils.h

 //===-- Collection of utils for mktime and friends --------------*- 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_TIME_UTILS_H
 #define LLVM_LIBC_SRC_TIME_TIME_UTILS_H
 
 #include <stddef.h> // For size_t.
+#include <time.h>
 
 #include "include/errno.h"
 
 #include "src/errno/llvmlibc_errno.h"
-#include "src/time/mktime.h"
 
 #include <stdint.h>
 
 namespace __llvm_libc {
 namespace time_utils {
 
 struct TimeConstants {
   static constexpr int SECONDS_PER_MIN = 60;
static inline struct tm *gmtime_internal(const time_t *timer,
   if (update_from_seconds(seconds, result) < 0) {
     out_of_range();
     return nullptr;
   }
 
   return result;
 }
 
+static inline struct tm *localtime_internal(const time_t *timer,
+                                            struct tm *result) {
+  // Unlike most C Library functions, localtime doesn't just die on bad input.
+  // TODO(rtenneti); Handle leap seconds, timezone and update of tm_isdst.
+  int64_t seconds = *timer;
+  // Update the tm structure's year, month, day, etc. from seconds.
+  if (update_from_seconds(seconds, result) < 0) {
+    out_of_range();
+    return nullptr;
+  }
+
+  return result;
+}
+
 } // namespace time_utils
 } // namespace __llvm_libc
 
 #endif // LLVM_LIBC_SRC_TIME_TIME_UTILS_H

libc/test/src/time/CMakeLists.txt

SRCS
     gmtime_r_test.cpp
   HDRS
     TmMatcher.h
   DEPENDS
     libc.src.time.gmtime_r
 )
 
 add_libc_unittest(
+  localtime
+  SUITE
+    libc_time_unittests
+  SRCS
+    localtime_test.cpp
+  HDRS
+    TmMatcher.h
+  DEPENDS
+    libc.src.time.localtime
+)
+
+add_libc_unittest(
+  localtime_r
+  SUITE
+    libc_time_unittests
+  SRCS
+    localtime_r_test.cpp
+  HDRS
+    TmMatcher.h
+  DEPENDS
+    libc.src.time.localtime_r
+)
+
+add_libc_unittest(
   mktime
   SUITE
     libc_time_unittests
   SRCS
     mktime_test.cpp
   HDRS
     TmHelper.h
     TmMatcher.h

libc/test/src/time/localtime_r_test.cpp

+//===-- Unittests for localtime_r -----------------------------------------===//
+//
+// 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/time/localtime_r.h"
+#include "src/time/time_utils.h"
+#include "test/src/time/TmMatcher.h"
+#include "utils/UnitTest/Test.h"
+
+using __llvm_libc::time_utils::TimeConstants;
+
+// localtime_r shares the same code as gmtime_r and thus didn't repeat all the
+// tests from gmtime. Added couple of validation tests (which are same as
+// gmtime_r's).
+//
+// TODO(rtenneti): Add tests for timezone and update the following tests for
+// timezone testing.
+
+TEST(LlvmLibcLocalTimeR, EndOf32BitEpochYear) {
+  // Test for maximum value of a signed 32-bit integer.
+  // Test implementation can encode time for Tue 19 January 2038 03:14:07 UTC.
+  time_t seconds = 0x7FFFFFFF;
+  struct tm tm_data;
+  struct tm *tm_data_ptr;
+  tm_data_ptr = __llvm_libc::localtime_r(&seconds, &tm_data);
+  EXPECT_TM_EQ((tm{7,  // sec
+                   14, // min
+                   3,  // hr
+                   19, // day
+                   0,  // tm_mon starts with 0 for Jan
+                   2038 - TimeConstants::TIME_YEAR_BASE, // year
+                   2,                                    // wday
+                   7,                                    // yday
+                   0}),
+               *tm_data_ptr);
+  EXPECT_TM_EQ(*tm_data_ptr, tm_data);
+}
+
+TEST(LlvmLibcLocalTimeR, Max64BitYear) {
+  if (sizeof(time_t) == 4)
+    return;
+  // Test for Tue Jan 1 12:50:50 in 2,147,483,647th year.
+  time_t seconds = 67767976202043050;
+  struct tm tm_data;
+  struct tm *tm_data_ptr;
+  tm_data_ptr = __llvm_libc::localtime_r(&seconds, &tm_data);
+  EXPECT_TM_EQ((tm{50, // sec
+                   50, // min
+                   12, // hr
+                   1,  // day
+                   0,  // tm_mon starts with 0 for Jan
+                   2147483647 - TimeConstants::TIME_YEAR_BASE, // year
+                   2,                                          // wday
+                   50,                                         // yday
+                   0}),
+               *tm_data_ptr);
+  EXPECT_TM_EQ(*tm_data_ptr, tm_data);
+}

libc/test/src/time/localtime_test.cpp

+//===-- Unittests for localtime -------------------------------------------===//
+//
+// 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/time/localtime.h"
+#include "src/time/time_utils.h"
+#include "test/src/time/TmMatcher.h"
+#include "utils/UnitTest/Test.h"
+
+using __llvm_libc::time_utils::TimeConstants;
+
+// localtime shares the same code as gmtime and thus didn't repeat all the tests
+// from gmtime. Added couple of validation tests (which are same as gmtime's).
+//
+// TODO(rtenneti): Add tests for timezone and update the following tests for
+// timezone testing.
+
+TEST(LlvmLibcLocalTime, EndOf32BitEpochYear) {
+  // Test for maximum value of a signed 32-bit integer.
+  // Test implementation can encode time for Tue 19 January 2038 03:14:07 UTC.
+  time_t seconds = 0x7FFFFFFF;
+  struct tm *tm_data = __llvm_libc::localtime(&seconds);
+  EXPECT_TM_EQ((tm{7,  // sec
+                   14, // min
+                   3,  // hr
+                   19, // day
+                   0,  // tm_mon starts with 0 for Jan
+                   2038 - TimeConstants::TIME_YEAR_BASE, // year
+                   2,                                    // wday
+                   7,                                    // yday
+                   0}),
+               *tm_data);
+}
+
+TEST(LlvmLibcLocalTime, Max64BitYear) {
+  if (sizeof(time_t) == 4)
+    return;
+  // Mon Jan 1 12:50:50 2170 (200 years from 1970),
+  time_t seconds = 6311479850;
+  struct tm *tm_data = __llvm_libc::localtime(&seconds);
+  EXPECT_TM_EQ((tm{50, // sec
+                   50, // min
+                   12, // hr
+                   1,  // day
+                   0,  // tm_mon starts with 0 for Jan
+                   2170 - TimeConstants::TIME_YEAR_BASE, // year
+                   1,                                    // wday
+                   50,                                   // yday
+                   0}),
+               *tm_data);
+
+  // Test for Tue Jan 1 12:50:50 in 2,147,483,647th year.
+  seconds = 67767976202043050;
+  tm_data = __llvm_libc::localtime(&seconds);
+  EXPECT_TM_EQ((tm{50, // sec
+                   50, // min
+                   12, // hr
+                   1,  // day
+                   0,  // tm_mon starts with 0 for Jan
+                   2147483647 - TimeConstants::TIME_YEAR_BASE, // year
+                   2,                                          // wday
+                   50,                                         // yday
+                   0}),
+               *tm_data);
+}