Optionally allow fractional seconds in timestamps

Fixes #267

Author: joto

include/osmium/osm/object.hpp

@@ -307,8 +307,9 @@ namespace osmium {
          */
         OSMObject& set_timestamp(const char* timestamp) {
             assert(timestamp);
-            m_timestamp = detail::parse_timestamp(timestamp);
-            if (timestamp[20] != '\0') {
+            const char** str = &timestamp;
+            m_timestamp = detail::parse_timestamp(str);
+            if (**str != '\0') {
                 throw std::invalid_argument{"can not parse timestamp: garbage after timestamp"};
             }
             return *this;

include/osmium/osm/timestamp.hpp

@@ -79,7 +79,30 @@ namespace osmium {
             out += static_cast<char>('0' + value);
         }
 
-        inline std::time_t parse_timestamp(const char* str) {
+        inline bool fractional_seconds(const char** s) noexcept {
+            const char* str = *s;
+
+            if (*str != '.' && *str != ',') {
+                return false;
+            }
+
+            ++str;
+            if (*str < '0' || *str > '9') {
+                return false;
+            }
+
+            do {
+                ++str;
+            } while (*str >= '0' && *str <= '9');
+
+            *s = str;
+            return *str == 'Z';
+        }
+
+        inline std::time_t parse_timestamp(const char** s) {
+            const char* str = *s;
+            *s += 19;
+
             static const std::array<int, 12> mon_lengths = {{
                 31, 29, 31, 30, 31, 30,
                 31, 31, 30, 31, 30, 31
@@ -104,7 +127,8 @@ namespace osmium {
                 str[16] == ':' &&
                 str[17] >= '0' && str[17] <= '9' &&
                 str[18] >= '0' && str[18] <= '9' &&
-                str[19] == 'Z') {
+                (str[19] == 'Z' || fractional_seconds(s))) {
+                ++(*s);
                 std::tm tm; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init)
                 tm.tm_year = (str[ 0] - '0') * 1000 +
                              (str[ 1] - '0') *  100 +
@@ -134,6 +158,11 @@ namespace osmium {
             throw std::invalid_argument{std::string{"can not parse timestamp: '"} + str + "'"};
         }
 
+        inline std::time_t parse_timestamp(const char* s) {
+            const char** str = &s;
+            return parse_timestamp(str);
+        }
+
     } // namespace detail
 
     /**

test/t/osm/test_timestamp.cpp

@@ -126,6 +126,39 @@ TEST_CASE("Valid timestamps") {
     }
 }
 
+TEST_CASE("Valid timestamps with fractional seconds") {
+    const std::vector<std::string> test_cases = {
+        "2016-03-31T23:59:59.123Z",
+        "2016-03-31T23:59:59,4Z",
+        "2016-03-31T23:59:59,000000000000000001Z",
+        "2016-03-31T23:59:59.99Z"
+    };
+
+    for (const auto& tc : test_cases) {
+        const osmium::Timestamp t{tc};
+        REQUIRE("2016-03-31T23:59:59Z" == t.to_iso());
+        REQUIRE("2016-03-31T23:59:59Z" == t.to_iso_all());
+    }
+}
+
+TEST_CASE("Timestamp parsing leaves pointer after timestamp") {
+    const std::vector<std::string> test_cases = {
+        "2016-03-31T23:59:59Z#",
+        "2016-03-31T23:59:59.123Z#",
+        "2016-03-31T23:59:59,4Z#",
+        "2016-03-31T23:59:59,000000000000000001Z#",
+        "2016-03-31T23:59:59.99Z#"
+    };
+
+    for (const auto& tc : test_cases) {
+        const char *s = tc.data();
+        const char **str = &s;
+        auto const timestamp = osmium::detail::parse_timestamp(str);
+        REQUIRE(**str == '#');
+        REQUIRE(osmium::Timestamp(timestamp).to_iso() == "2016-03-31T23:59:59Z");
+    }
+}
+
 TEST_CASE("Invalid timestamps") {
     REQUIRE_THROWS_AS(osmium::Timestamp{""}, std::invalid_argument);
     REQUIRE_THROWS_AS(osmium::Timestamp{"x"}, std::invalid_argument);
@@ -149,5 +182,11 @@ TEST_CASE("Invalid timestamps") {
     REQUIRE_THROWS_AS(osmium::Timestamp{"2000-01-32T00:00:00Z"}, std::invalid_argument);
     REQUIRE_THROWS_AS(osmium::Timestamp{"2000-02-30T00:00:00Z"}, std::invalid_argument);
     REQUIRE_THROWS_AS(osmium::Timestamp{"2000-03-32T00:00:00Z"}, std::invalid_argument);
+    REQUIRE_THROWS_AS(osmium::Timestamp{"2000-03-01T00:00:00"}, std::invalid_argument);
+    REQUIRE_THROWS_AS(osmium::Timestamp{"2000-03-01T00:00:00,Z"}, std::invalid_argument);
+    REQUIRE_THROWS_AS(osmium::Timestamp{"2000-03-01T00:00:00,xZ"}, std::invalid_argument);
+    REQUIRE_THROWS_AS(osmium::Timestamp{"2000-03-01T00:00:00,123mZ"}, std::invalid_argument);
+    REQUIRE_THROWS_AS(osmium::Timestamp{"2000-03-01T00:00:00.@Z"}, std::invalid_argument);
+    REQUIRE_THROWS_AS(osmium::Timestamp{"2000-03-01T00:00:00.@"}, std::invalid_argument);
 }