Export of internal Abseil changes.

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ed4be0cb9a708158187a0628c1c2167ae6783274 by Greg Falcon <gfalcon@google.com>:

Refactor a string unit test into a template function for internal purposes.

PiperOrigin-RevId: 210798880

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e4c734be903ac7b3a88caf4b17909343c283a21a by Abseil Team <absl-team@google.com>:

Add a note that the RFC3339_* format specifiers use %Y, and so
do not produce 4-digit years on output nor require 4-digit years
on input, as a strict reading of RFC3339 might require.

PiperOrigin-RevId: 210785544

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cfb5e32f9397e49ddb731445a191b36652fe2f6d by Greg Falcon <gfalcon@google.com>:

Refactor a string unit test into a template function for internal purposes.

PiperOrigin-RevId: 210776525

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105ee700e62869cfda2a37e6f7c2ea483f8fc75e by Xiaoyi Zhang <zhangxy@google.com>:

Correctly define ABSL_HAVE_STD_STRING_VIEW for MSVC 2017. Currently the macro
is not defined even though MSVC 2017 provides `std::string_view`, and this
means both `absl::string_view` and `std::string_view` exist as distinct types.
A bunch of places relying on the false assumption that
`string_view::const_iterator` is `const char*` have to be fixed to build
successfully.

See related github issue https://github.com/abseil/abseil-cpp/issues/161.

PiperOrigin-RevId: 210764947
GitOrigin-RevId: ed4be0cb9a708158187a0628c1c2167ae6783274
Change-Id: I7a9658b3201aa669db9d3d90474feb08072718c7

absl/strings/internal/str_format/output.h

@@ -69,10 +69,10 @@ class FILERawSink {
 
 // Provide RawSink integration with common types from the STL.
 inline void AbslFormatFlush(std::string* out, string_view s) {
-  out->append(s.begin(), s.size());
+  out->append(s.data(), s.size());
 }
 inline void AbslFormatFlush(std::ostream* out, string_view s) {
-  out->write(s.begin(), s.size());
+  out->write(s.data(), s.size());
 }
 
 template <class AbslCord, typename = typename std::enable_if<

absl/strings/internal/str_format/parser.cc

@@ -81,8 +81,8 @@ static constexpr std::int8_t kIds[] = {
 template <bool is_positional>
 bool ConsumeConversion(string_view *src, UnboundConversion *conv,
                        int *next_arg) {
-  const char *pos = src->begin();
-  const char *const end = src->end();
+  const char *pos = src->data();
+  const char *const end = pos + src->size();
   char c;
   // Read the next char into `c` and update `pos`. Reads '\0' if at end.
   const auto get_char = [&] { c = pos == end ? '\0' : *pos++; };

absl/strings/internal/str_format/parser.h

@@ -90,7 +90,7 @@ bool ParseFormatString(string_view src, Consumer consumer) {
   int next_arg = 0;
   while (!src.empty()) {
     const char* percent =
-        static_cast<const char*>(memchr(src.begin(), '%', src.size()));
+        static_cast<const char*>(memchr(src.data(), '%', src.size()));
     if (!percent) {
       // We found the last substring.
       return consumer.Append(src);
@@ -98,7 +98,7 @@ bool ParseFormatString(string_view src, Consumer consumer) {
     // We found a percent, so push the text run then process the percent.
     size_t percent_loc = percent - src.data();
     if (!consumer.Append(string_view(src.data(), percent_loc))) return false;
-    if (percent + 1 >= src.end()) return false;
+    if (percent + 1 >= src.data() + src.size()) return false;
 
     UnboundConversion conv;
 
@@ -178,7 +178,8 @@ class ParsedFormatBase {
     const char* const base = data_.get();
     string_view text(base, 0);
     for (const auto& item : items_) {
-      text = string_view(text.end(), (base + item.text_end) - text.end());
+      const char* const end = text.data() + text.size();
+      text = string_view(end, (base + item.text_end) - end);
       if (item.is_conversion) {
         if (!consumer.ConvertOne(item.conv, text)) return false;
       } else {

absl/strings/internal/str_format/parser_test.cc

@@ -66,10 +66,10 @@ class ConsumeUnboundConversionTest : public ::testing::Test {
   typedef UnboundConversion Props;
   string_view Consume(string_view* src) {
     int next = 0;
-    const char* prev_begin = src->begin();
+    const char* prev_begin = src->data();
     o = UnboundConversion();  // refresh
     ConsumeUnboundConversion(src, &o, &next);
-    return {prev_begin, static_cast<size_t>(src->begin() - prev_begin)};
+    return {prev_begin, static_cast<size_t>(src->data() - prev_begin)};
   }
 
   bool Run(const char *fmt, bool force_positional = false) {