SERVER-68487 add BSONElement::isNaN()

(cherry picked from commit ed25ebe0d87dd2521fbfc5534ba7af7de69aad4d)

2 files changed, 39 insertions, 0 deletions

diff --git a/src/mongo/bson/bsonelement.h b/src/mongo/bson/bsonelement.h
index 86bd8ed9408..84230f95615 100644
--- a/src/mongo/bson/bsonelement.h
+++ b/src/mongo/bson/bsonelement.h
@@ -317,6 +317,11 @@ public:
     /** True if element is of a numeric type. */
     bool isNumber() const;
 
+    /**
+     * True if element is a NaN double or decimal.
+     */
+    bool isNaN() const;
+
     /** Return double value for this field. MUST be NumberDouble type. */
     double _numberDouble() const {
         return ConstDataView(value()).read<LittleEndian<double>>();
@@ -824,6 +829,21 @@ inline bool BSONElement::isNumber() const {
     }
 }
 
+inline bool BSONElement::isNaN() const {
+    switch (type()) {
+        case NumberDouble: {
+            double d = _numberDouble();
+            return std::isnan(d);
+        }
+        case NumberDecimal: {
+            Decimal128 d = _numberDecimal();
+            return d.isNaN();
+        }
+        default:
+            return false;
+    }
+}
+
 inline Decimal128 BSONElement::numberDecimal() const {
     switch (type()) {
         case NumberDouble:
diff --git a/src/mongo/bson/bsonelement_test.cpp b/src/mongo/bson/bsonelement_test.cpp
index f98ccf93894..d47e91dab9f 100644
--- a/src/mongo/bson/bsonelement_test.cpp
+++ b/src/mongo/bson/bsonelement_test.cpp
@@ -203,6 +203,25 @@ TEST(BSONElement, SafeNumberLongNegativeBound) {
     ASSERT_EQ(obj["negativeInfinity"].safeNumberLong(), std::numeric_limits<long long>::lowest());
 }
 
+TEST(BSONElement, IsNaN) {
+    ASSERT(BSON("" << std::numeric_limits<double>::quiet_NaN()).firstElement().isNaN());
+    ASSERT(BSON("" << -std::numeric_limits<double>::quiet_NaN()).firstElement().isNaN());
+    ASSERT(BSON("" << Decimal128::kPositiveNaN).firstElement().isNaN());
+    ASSERT(BSON("" << Decimal128::kNegativeNaN).firstElement().isNaN());
+
+    ASSERT_FALSE(BSON("" << std::numeric_limits<double>::infinity()).firstElement().isNaN());
+    ASSERT_FALSE(BSON("" << -std::numeric_limits<double>::infinity()).firstElement().isNaN());
+    ASSERT_FALSE(BSON("" << Decimal128::kPositiveInfinity).firstElement().isNaN());
+    ASSERT_FALSE(BSON("" << Decimal128::kNegativeInfinity).firstElement().isNaN());
+    ASSERT_FALSE(BSON("" << Decimal128{"9223372036854775808.5"}).firstElement().isNaN());
+    ASSERT_FALSE(BSON("" << Decimal128{"-9223372036854775809.99"}).firstElement().isNaN());
+    ASSERT_FALSE(BSON("" << 12345LL).firstElement().isNaN());
+    ASSERT_FALSE(BSON(""
+                      << "foo")
+                     .firstElement()
+                     .isNaN());
+}
+
 TEST(BSONElementIntegerParseTest, ParseIntegerElementToNonNegativeLongRejectsNegative) {
     BSONObj query = BSON("" << -2LL);
     ASSERT_NOT_OK(query.firstElement().parseIntegerElementToNonNegativeLong());