[Android][libraries] TimeZoneInfo Android imp

src/libraries/Common/src/Interop/Unix/System.Native/Interop.GetDefaultTimeZone.Android.cs

@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        [DllImport(Interop.Libraries.SystemNative, EntryPoint = "SystemNative_GetDefaultTimeZone", CharSet = CharSet.Ansi, SetLastError = true)]
+        internal static extern string? GetDefaultTimeZone();
+    }
+}

src/libraries/Native/Unix/System.Native/pal_datetime.c

@@ -2,13 +2,15 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 #include "pal_config.h"
-
-#include <stdlib.h>
+#include "pal_datetime.h"
 #include <stdint.h>
-#include <time.h>
+#include <stdlib.h>
+#include <string.h>
 #include <sys/time.h>
-
-#include "pal_datetime.h"
+#if defined(TARGET_ANDROID)
+#include <sys/system_properties.h>
+#endif
+#include <time.h>
 
 static const int64_t TICKS_PER_SECOND = 10000000; /* 10^7 */
 #if HAVE_CLOCK_REALTIME
@@ -39,3 +41,18 @@ int64_t SystemNative_GetSystemTimeAsTicks()
     // in failure we return 00:00 01 January 1970 UTC (Unix epoch)
     return 0;
 }
+
+#if defined(TARGET_ANDROID)
+char* SystemNative_GetDefaultTimeZone()
+{
+    char defaulttimezone[PROP_VALUE_MAX];
+    if (__system_property_get("persist.sys.timezone", defaulttimezone))
+    {
+        return strdup(defaulttimezone);
+    }
+    else
+    {
+        return NULL;
+    }
+}
+#endif

src/libraries/Native/Unix/System.Native/pal_datetime.h

@@ -4,5 +4,10 @@
 #pragma once
 
 #include "pal_compiler.h"
+#include "pal_types.h"
 
 PALEXPORT int64_t SystemNative_GetSystemTimeAsTicks(void);
+
+#if defined(TARGET_ANDROID)
+PALEXPORT char* SystemNative_GetDefaultTimeZone(void);
+#endif

src/libraries/System.Private.CoreLib/src/Resources/Strings.resx

@@ -3796,4 +3796,16 @@
   <data name="Arg_MemberInfoNotFound" xml:space="preserve">
     <value>A MemberInfo that matches '{0}' could not be found.</value>
   </data>
+  <data name="InvalidOperation_BadTZHeader" xml:space="preserve">
+    <value>Bad magic in '{0}': Header starts with '{1}' instead of 'tzdata'</value>
+  </data>
+  <data name="InvalidOperation_ReadTZError" xml:space="preserve">
+    <value>Unable to fully read from file '{0}' at offset {1} length {2}; read {3} bytes expected {4}.</value>
+  </data>
+  <data name="InvalidOperation_BadIndexLength" xml:space="preserve">
+    <value>Length in index file less than AndroidTzDataHeader</value>
+  </data>
+  <data name="TimeZoneNotFound_ValidTimeZoneFileMissing" xml:space="preserve">
+    <value>Unable to properly load any time zone data files.</value>
+  </data>
 </root>

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

@@ -1953,6 +1953,9 @@
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.GetCwd.cs">
       <Link>Common\Interop\Unix\System.Native\Interop.GetCwd.cs</Link>
     </Compile>
+    <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.GetDefaultTimeZone.Android.cs" Condition="'$(TargetsAndroid)' == 'true'">
+      <Link>Common\Interop\Unix\System.Native\Interop.GetDefaultTimeZone.Android.cs</Link>
+    </Compile>
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.GetEGid.cs">
       <Link>Common\Interop\Unix\System.Native\Interop.GetHostName.cs</Link>
     </Compile>
@@ -2126,6 +2129,8 @@
     <Compile Include="$(MSBuildThisFileDirectory)System\Threading\LowLevelMonitor.Unix.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Threading\TimerQueue.Unix.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\TimeZoneInfo.Unix.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\TimeZoneInfo.Unix.Android.cs" Condition="'$(TargetsAndroid)' == 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\TimeZoneInfo.Unix.NonAndroid.cs" Condition="'$(TargetsAndroid)' != 'true'" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetsUnix)' == 'true'">
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.GetEUid.cs">