SkTime: return timezone information; format in ISO-8601

Motivation: PDF/A metadata will need the creation date embedded in it.

Also, GetDateTime returns local time in Win32.  This now behaves the
same as on Unix systems.

BUG=skia:3110

Review URL: https://codereview.chromium.org/1109593002

6 files changed, 63 insertions, 2 deletions

diff --git a/gyp/core.gypi b/gyp/core.gypi
index 1f062524ae..fef6fe45b3 100644
--- a/gyp/core.gypi
+++ b/gyp/core.gypi
@@ -208,6 +208,7 @@
         '<(skia_src_path)/core/SkTextBlob.cpp',
         '<(skia_src_path)/core/SkTextFormatParams.h',
         '<(skia_src_path)/core/SkTextMapStateProc.h',
+        '<(skia_src_path)/core/SkTime.cpp',
         '<(skia_src_path)/core/SkTDPQueue.h',
         '<(skia_src_path)/core/SkTLList.h',
         '<(skia_src_path)/core/SkTLS.cpp',
diff --git a/include/core/SkTime.h b/include/core/SkTime.h
index 51616d41c7..a8656347aa 100644
--- a/include/core/SkTime.h
+++ b/include/core/SkTime.h
@@ -12,12 +12,16 @@
 
 #include "SkTypes.h"
 
+class SkString;
+
 /** \class SkTime
     Platform-implemented utilities to return time of day, and millisecond counter.
 */
 class SkTime {
 public:
     struct DateTime {
+        int16_t  fTimeZoneMinutes;  // The number of minutes that GetDateTime()
+                                    // is ahead of or behind UTC.
         uint16_t fYear;          //!< e.g. 2005
         uint8_t  fMonth;         //!< 1..12
         uint8_t  fDayOfWeek;     //!< 0..6, 0==Sunday
@@ -25,6 +29,8 @@ public:
         uint8_t  fHour;          //!< 0..23
         uint8_t  fMinute;        //!< 0..59
         uint8_t  fSecond;        //!< 0..59
+
+        void toISO8601(SkString* dst) const;
     };
     static void GetDateTime(DateTime*);
 
diff --git a/src/core/SkTime.cpp b/src/core/SkTime.cpp
new file mode 100644
index 0000000000..b8e42365ef
--- /dev/null
+++ b/src/core/SkTime.cpp
@@ -0,0 +1,24 @@
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkString.h"
+#include "SkTime.h"
+
+void SkTime::DateTime::toISO8601(SkString* dst) const {
+    if (dst) {
+        int timeZoneMinutes = SkToInt(fTimeZoneMinutes);
+        char timezoneSign = timeZoneMinutes >= 0 ? '+' : '-';
+        int timeZoneHours = abs(timeZoneMinutes) / 60;
+        timeZoneMinutes = abs(timeZoneMinutes) % 60;
+        dst->printf("%04u-%02u-%02uT%02u:%02u:%02u%c%02d:%02d",
+                    static_cast<unsigned>(fYear), static_cast<unsigned>(fMonth),
+                    static_cast<unsigned>(fDay), static_cast<unsigned>(fHour),
+                    static_cast<unsigned>(fMinute),
+                    static_cast<unsigned>(fSecond), timezoneSign, timeZoneHours,
+                    timeZoneMinutes);
+    }
+}
diff --git a/src/ports/SkTime_Unix.cpp b/src/ports/SkTime_Unix.cpp
index 6e305a16f6..2d5fa279b4 100644
--- a/src/ports/SkTime_Unix.cpp
+++ b/src/ports/SkTime_Unix.cpp
@@ -16,11 +16,15 @@ void SkTime::GetDateTime(DateTime* dt)
 {
     if (dt)
     {
+        tzset();  // initialize timezone variable;
         time_t m_time;
         time(&m_time);
         struct tm* tstruct;
         tstruct = localtime(&m_time);
+        int offset = tstruct->tm_isdst == 1 ? 60 : 0;
+
         // http://pubs.opengroup.org/onlinepubs/009695399/basedefs/time.h.html
+        dt->fTimeZoneMinutes = SkToS16(offset - timezone / 60);
         dt->fYear       = tstruct->tm_year + 1900;
         dt->fMonth      = SkToU8(tstruct->tm_mon + 1);
         dt->fDayOfWeek  = SkToU8(tstruct->tm_wday);
diff --git a/src/ports/SkTime_win.cpp b/src/ports/SkTime_win.cpp
index bc0f8f0084..19f4695a86 100644
--- a/src/ports/SkTime_win.cpp
+++ b/src/ports/SkTime_win.cpp
@@ -14,8 +14,22 @@ void SkTime::GetDateTime(DateTime* dt)
     if (dt)
     {
         SYSTEMTIME      st;
-        GetSystemTime(&st);
-
+        TIME_ZONE_INFORMATION timeZoneInfo;
+        int tz_bias;
+        GetLocalTime(&st);
+        // https://gist.github.com/wrl/8924636
+        switch (GetTimeZoneInformation(&timeZoneInfo)) {
+            case TIME_ZONE_ID_STANDARD:
+                tz_bias = -timeZoneInfo.Bias - timeZoneInfo.StandardBias;
+                break;
+            case TIME_ZONE_ID_DAYLIGHT:
+                tz_bias = -timeZoneInfo.Bias - timeZoneInfo.DaylightBias;
+                break;
+            default:
+                tz_bias = -timeZoneInfo.Bias;
+                break;
+        }
+        dt->fTimeZoneMinutes = SkToS16(tz_bias);
         dt->fYear       = st.wYear;
         dt->fMonth      = SkToU8(st.wMonth);
         dt->fDayOfWeek  = SkToU8(st.wDayOfWeek);
diff --git a/tests/Time.cpp b/tests/Time.cpp
index 0139654e19..60dcd5527c 100644
--- a/tests/Time.cpp
+++ b/tests/Time.cpp
@@ -41,4 +41,16 @@ DEF_TEST(Time_GetDateTime, r) {
     REPORTER_ASSERT(r, dateTime.fMinute <= 59);
 
     REPORTER_ASSERT(r, dateTime.fSecond <= 60);  // leap seconds are 23:59:60
+
+    // The westernmost timezone is -12:00.
+    // The easternmost timezone is +14:00.
+    REPORTER_ASSERT(r, abs(SkToInt(dateTime.fTimeZoneMinutes)) <= 14 * 60);
+
+    SkString timeStamp;
+    dateTime.toISO8601(&timeStamp);
+    REPORTER_ASSERT(r, timeStamp.size() > 0);
+    if (r->verbose()) {  // `dm --veryVerbose`
+        SkDebugf("\nCurrent Time (ISO-8601 format): \"%s\"\n",
+                 timeStamp.c_str());
+    }
 }