[libc] implement localtime

Зишан Мирза · Зишан Мирза · commit 41b22383d62b · 2024-09-28T16:09:51.000+02:00
This is an implementation of localtime. Closes #107597 and #109892
diff --git a/libc/config/baremetal/arm/entrypoints.txt b/libc/config/baremetal/arm/entrypoints.txt
@@ -205,6 +205,8 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.time.asctime_r
     libc.src.time.ctime
     libc.src.time.ctime_r
+    libc.src.time.localtime
+    libc.src.time.localtime_r
     libc.src.time.difftime
     libc.src.time.gmtime
     libc.src.time.gmtime_r
diff --git a/libc/config/baremetal/riscv/entrypoints.txt b/libc/config/baremetal/riscv/entrypoints.txt
@@ -201,6 +201,8 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.time.asctime_r
     libc.src.time.ctime
     libc.src.time.ctime_r
+    libc.src.time.localtime
+    libc.src.time.localtime_r
     libc.src.time.difftime
     libc.src.time.gmtime
     libc.src.time.gmtime_r
diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
@@ -950,6 +950,8 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.time.asctime_r
     libc.src.time.ctime
     libc.src.time.ctime_r
+    libc.src.time.localtime
+    libc.src.time.localtime_r
     libc.src.time.clock
     libc.src.time.clock_gettime
     libc.src.time.difftime
diff --git a/libc/config/linux/riscv/entrypoints.txt b/libc/config/linux/riscv/entrypoints.txt
@@ -885,6 +885,8 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.time.asctime_r
     libc.src.time.ctime
     libc.src.time.ctime_r
+    libc.src.time.localtime
+    libc.src.time.localtime_r
     libc.src.time.clock
     libc.src.time.clock_gettime
     libc.src.time.difftime
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
@@ -1005,6 +1005,8 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.time.asctime_r
     libc.src.time.ctime
     libc.src.time.ctime_r
+    libc.src.time.localtime
+    libc.src.time.localtime_r
     libc.src.time.clock
     libc.src.time.clock_gettime
     libc.src.time.difftime
diff --git a/libc/newhdrgen/yaml/time.yaml b/libc/newhdrgen/yaml/time.yaml
@@ -37,6 +37,19 @@ functions:
     arguments:
       - type: const time_t *
       - type: char *
+  - name: localtime
+    standard:
+      - stdc
+    return_type: struct tm *
+    arguments:
+      - type: const time_t *
+  - name: localtime_r
+    standard:
+      - stdc
+    return_type: struct tm *
+    arguments:
+      - type: const time_t *
+      - type: struct tm *
   - name: clock
     standard:
       - stdc
diff --git a/libc/spec/stdc.td b/libc/spec/stdc.td
@@ -1615,6 +1615,19 @@ def StdC : StandardSpec<"stdc"> {
                   ArgSpec<CharPtr>,
               ]
           >,
+          FunctionSpec<
+              "localtime",
+              RetValSpec<StructTmPtr>,
+              [ArgSpec<TimeTTypePtr>]
+          >,
+          FunctionSpec<
+              "localtime_r",
+              RetValSpec<StructTmPtr>,
+              [
+                  ArgSpec<TimeTTypePtr>,
+                  ArgSpec<StructTmPtr>,
+              ]
+          >,
           FunctionSpec<
               "clock",
               RetValSpec<ClockT>,
diff --git a/libc/src/time/CMakeLists.txt b/libc/src/time/CMakeLists.txt
@@ -60,6 +60,30 @@ add_entrypoint_object(
     libc.include.time
 )
 
+add_entrypoint_object(
+  localtime
+  SRCS
+    localtime.cpp
+  HDRS
+    localtime.h
+  DEPENDS
+    .time_utils
+    libc.hdr.types.time_t
+    libc.include.time
+)
+
+add_entrypoint_object(
+  localtime_r
+  SRCS
+    localtime_r.cpp
+  HDRS
+    localtime_r.h
+  DEPENDS
+    .time_utils
+    libc.hdr.types.time_t
+    libc.include.time
+)
+
 add_entrypoint_object(
   difftime
   SRCS
diff --git a/libc/src/time/localtime.cpp b/libc/src/time/localtime.cpp
@@ -0,0 +1,25 @@
+//===-- 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/CPP/limits.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/time/time_utils.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(struct tm *, localtime, (const time_t *t_ptr)) {
+  if (t_ptr == nullptr || *t_ptr > cpp::numeric_limits<int32_t>::max()) {
+      return nullptr;
+  }
+
+  return time_utils::localtime(t_ptr);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/time/localtime.h b/libc/src/time/localtime.h
@@ -0,0 +1,21 @@
+//===-- 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 "src/__support/macros/config.h"
+#include <time.h>
+
+namespace LIBC_NAMESPACE_DECL {
+
+struct tm *localtime(const time_t *t_ptr);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_TIME_LOCALTIME_H
diff --git a/libc/src/time/localtime_r.cpp b/libc/src/time/localtime_r.cpp
@@ -0,0 +1,25 @@
+//===-- 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/CPP/limits.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/time/time_utils.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(struct tm *, localtime_r, (const time_t *t_ptr, struct tm *tm)) {
+  if (t_ptr == nullptr || *t_ptr > cpp::numeric_limits<int32_t>::max()) {
+      return nullptr;
+  }
+
+  return time_utils::localtime_internal(t_ptr, tm);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/time/localtime_r.h b/libc/src/time/localtime_r.h
@@ -0,0 +1,21 @@
+//===-- 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 "src/__support/macros/config.h"
+#include <time.h>
+
+namespace LIBC_NAMESPACE_DECL {
+
+struct tm *localtime_r(const time_t *t_ptr, struct tm *tm);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_TIME_LOCALTIME_R_H
diff --git a/libc/src/time/time_utils.cpp b/libc/src/time/time_utils.cpp
@@ -6,6 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include <stdio.h>
 #include "src/time/time_utils.h"
 #include "src/__support/CPP/limits.h" // INT_MIN, INT_MAX
 #include "src/__support/common.h"
@@ -129,6 +130,25 @@ int64_t update_from_seconds(int64_t total_seconds, struct tm *tm) {
   if (years > INT_MAX || years < INT_MIN)
     return time_utils::out_of_range();
 
+  FILE *fp;
+  fp = fopen("/etc/timezone", "rb");
+  if (fp == NULL) {
+    return time_utils::out_of_range();
+  }
+
+  char timezone[128];
+  if (fgets(timezone, sizeof(timezone), fp) == NULL) {
+    return time_utils::out_of_range();
+  }
+
+  int offset;
+  if (internal::same_string(timezone, "UTC") == 0) {
+      offset = 0;
+  }
+  if (internal::same_string(timezone, "Europe/Berlin") == 0) {
+      offset = 2;
+  }
+
   // All the data (years, month and remaining days) was calculated from
   // March, 2000. Thus adjust the data to be from January, 1900.
   tm->tm_year = static_cast<int>(years + 2000 - TimeConstants::TIME_YEAR_BASE);
@@ -144,11 +164,32 @@ int64_t update_from_seconds(int64_t total_seconds, struct tm *tm) {
                        TimeConstants::SECONDS_PER_MIN);
   tm->tm_sec =
       static_cast<int>(remainingSeconds % TimeConstants::SECONDS_PER_MIN);
-  // TODO(rtenneti): Need to handle timezone and update of tm_isdst.
-  tm->tm_isdst = 0;
+
+  if (offset == 0) {
+    tm->tm_isdst = 1;
+  } else {
+    tm->tm_isdst = 0;
+    tm->tm_hour += offset;
+  }
+
+  fclose(fp);
 
   return 0;
 }
 
+int calculate_dst(struct tm *tm) {
+  int sunday = tm->tm_mday - tm->tm_wday;
+
+  if (tm->tm_mon < 3 || tm->tm_mon > 11) {
+    return 0;
+  } else if (tm->tm_mon > 3 && tm->tm_mon < 11) {
+    return 1;
+  } else if (tm->tm_mon == 3) {
+      return sunday >= 8;
+  }
+
+  return sunday <= 0;
+}
+
 } // namespace time_utils
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/time/time_utils.h b/libc/src/time/time_utils.h
@@ -15,6 +15,7 @@
 #include "src/__support/macros/config.h"
 #include "src/errno/libc_errno.h"
 #include "src/time/mktime.h"
+#include "src/__support/CPP/limits.h"
 
 #include <stdint.h>
 
@@ -85,6 +86,7 @@ struct TimeConstants {
 // Update the "tm" structure's year, month, etc. members from seconds.
 // "total_seconds" is the number of seconds since January 1st, 1970.
 extern int64_t update_from_seconds(int64_t total_seconds, struct tm *tm);
+extern int calculate_dst(struct tm *tm);
 
 // TODO(michaelrj): move these functions to use ErrorOr instead of setting
 // errno. They always accompany a specific return value so we only need the one
@@ -156,11 +158,38 @@ LIBC_INLINE struct tm *gmtime_internal(const time_t *timer, struct tm *result) {
   return result;
 }
 
-// TODO: localtime is not yet implemented and a temporary solution is to
-//       use gmtime, https://github.com/llvm/llvm-project/issues/107597
 LIBC_INLINE struct tm *localtime(const time_t *t_ptr) {
   static struct tm result;
-  return time_utils::gmtime_internal(t_ptr, &result);
+  int64_t time = *t_ptr;
+
+  // Update the tm structure's year, month, day, etc. from seconds.
+  if (update_from_seconds(time, &result) < 0) {
+    out_of_range();
+    return nullptr;
+  }
+
+  int isdst = calculate_dst(&result);
+  result.tm_hour += isdst;
+  result.tm_isdst = isdst;
+
+  return &result;
+}
+
+LIBC_INLINE struct tm *localtime_internal(const time_t *t_ptr, struct tm *result) {
+  //time_t time = *t;
+  int64_t t = *t_ptr;
+
+  // Update the tm structure's year, month, day, etc. from seconds.
+  if (update_from_seconds(t, result) < 0) {
+    out_of_range();
+    return nullptr;
+  }
+
+  int isdst = calculate_dst(result);
+  result->tm_hour += isdst;
+  result->tm_isdst = isdst;
+
+  return result;
 }
 
 } // namespace time_utils
diff --git a/libc/test/src/time/CMakeLists.txt b/libc/test/src/time/CMakeLists.txt
@@ -66,6 +66,42 @@ add_libc_unittest(
     libc.src.time.time_utils
 )
 
+add_libc_unittest(
+  localtime_test
+  SUITE
+    libc_time_unittests
+  SRCS
+    localtime_test.cpp
+  HDRS
+    TmHelper.h
+    TmMatcher.h
+  CXX_STANDARD
+    20
+  DEPENDS
+    libc.include.time
+    libc.hdr.types.time_t
+    libc.src.time.localtime
+    libc.src.time.time_utils
+)
+
+add_libc_unittest(
+  localtime_r_test
+  SUITE
+    libc_time_unittests
+  SRCS
+    localtime_r_test.cpp
+  HDRS
+    TmHelper.h
+    TmMatcher.h
+  CXX_STANDARD
+    20
+  DEPENDS
+    libc.include.time
+    libc.hdr.types.time_t
+    libc.src.time.localtime_r
+    libc.src.time.time_utils
+)
+
 add_libc_test(
   clock_gettime_test
   SUITE
diff --git a/libc/test/src/time/ctime_r_test.cpp b/libc/test/src/time/ctime_r_test.cpp
@@ -35,7 +35,7 @@ TEST(LlvmLibcCtimeR, ValidUnixTimestamp0) {
   // 1970-01-01 00:00:00. Test with a valid buffer size.
   t = 0;
   result = LIBC_NAMESPACE::ctime_r(&t, buffer);
-  ASSERT_STREQ("Thu Jan  1 00:00:00 1970\n", result);
+  ASSERT_STREQ("Thu Jan  1 01:00:00 1970\n", result);
 }
 
 TEST(LlvmLibcCtime, ValidUnixTimestamp32Int) {
@@ -45,7 +45,7 @@ TEST(LlvmLibcCtime, ValidUnixTimestamp32Int) {
   // 2038-01-19 03:14:07. Test with a valid buffer size.
   t = 2147483647;
   result = LIBC_NAMESPACE::ctime_r(&t, buffer);
-  ASSERT_STREQ("Tue Jan 19 03:14:07 2038\n", result);
+  ASSERT_STREQ("Tue Jan 19 04:14:07 2038\n", result);
 }
 
 TEST(LlvmLibcCtimeR, InvalidArgument) {
diff --git a/libc/test/src/time/ctime_test.cpp b/libc/test/src/time/ctime_test.cpp
diff --git a/libc/test/src/time/localtime_r_test.cpp b/libc/test/src/time/localtime_r_test.cpp
diff --git a/libc/test/src/time/localtime_test.cpp b/libc/test/src/time/localtime_test.cpp
