locale independent http date header

webcc/request_builder.cc

@@ -104,7 +104,7 @@ RequestBuilder& RequestBuilder::AuthToken(const std::string& token) {
 
 RequestBuilder& RequestBuilder::Date() {
   headers_.push_back(headers::kDate);
-  headers_.push_back(utility::GetTimestamp());
+  headers_.push_back(utility::HttpDate());
   return *this;
 }
 

webcc/response_builder.cc

@@ -57,7 +57,7 @@ ResponseBuilder& ResponseBuilder::File(const std::filesystem::path& path,
 
 ResponseBuilder& ResponseBuilder::Date() {
   headers_.push_back(headers::kDate);
-  headers_.push_back(utility::GetTimestamp());
+  headers_.push_back(utility::HttpDate());
   return *this;
 }
 

webcc/utility.cc

@@ -15,15 +15,38 @@ namespace webcc {
 namespace utility {
 
 const std::string& UserAgent() {
-  static auto s_user_agent = std::string("Webcc/") + WEBCC_VERSION;
+  static const std::string s_user_agent = std::string("Webcc/") + WEBCC_VERSION;
   return s_user_agent;
 }
 
-std::string GetTimestamp() {
+std::string HttpDate() {
   std::time_t t = std::time(nullptr);
-  std::stringstream ss;
+  tm* gmt = std::gmtime(&t);
-  ss << std::put_time(std::gmtime(&t), "%a, %d %b %Y %H:%M:%S") << " GMT";
+
-  return ss.str();
+  // Either put_time() or strftime() could format the date as expected, but they
+  // are both locale dependent!
+  //
+  //   std::stringstream ss;
+  //   ss << std::put_time(gmt, "%a, %d %b %Y %H:%M:%S") << " GMT";
+  //   return ss.str();
+  // 
+  //   char buf[26];
+  //   std::strftime(buf, 26, "%a, %d %b %Y %H:%M:%S", gmt);
+
+  static const char* const kDays[7] = { "Sun", "Mon", "Tue", "Wed",
+                                        "Thu", "Fri", "Sat" };
+
+  static const char* const kMonths[12] = { "Jan", "Feb", "Mar", "Apr",
+                                           "May", "Jun", "Jul", "Aug",
+                                           "Sep", "Oct", "Nov", "Dec" };
+
+  char buf[26];
+
+  std::snprintf(buf, 26, "%s, %.2i %s %i %.2i:%.2i:%.2i", kDays[gmt->tm_wday],
+               gmt->tm_mday, kMonths[gmt->tm_mon], gmt->tm_year + 1900,
+               gmt->tm_hour, gmt->tm_min, gmt->tm_sec);
+
+  return std::string(buf) + " GMT";
 }
 
 std::size_t TellSize(const std::filesystem::path& path) {

webcc/utility.h

@@ -24,7 +24,7 @@ const std::string& UserAgent();
 // Get the timestamp for HTTP Date header field.
 // E.g., Wed, 21 Oct 2015 07:28:00 GMT
 // See: https://tools.ietf.org/html/rfc7231#section-7.1.1.2
-std::string GetTimestamp();
+std::string HttpDate();
 
 // Tell the size in bytes of the given file.
 // Return kInvalidLength (-1) on failure.