SERVER-42034 Optimize ItoA

    (~13% faster, remove the 1kLoC static table)
    Reverts commit 7c9edfd4b931f3d3208142b411010b6b4afee21e.
    Python-generate table-emitting macro (compiler workaround).

1 files changed, 7 insertions, 10 deletions

diff --git a/src/mongo/util/itoa.h b/src/mongo/util/itoa.h
index 37451847a95..878bd62d3b6 100644
--- a/src/mongo/util/itoa.h
+++ b/src/mongo/util/itoa.h
@@ -41,23 +41,20 @@ namespace mongo {
  * and only really should be used in hot code paths.
  */
 class ItoA {
-    ItoA(const ItoA&) = delete;
-    ItoA& operator=(const ItoA&) = delete;
-
 public:
-    static constexpr size_t kBufSize = std::numeric_limits<uint64_t>::digits10  //
-        + 1   // digits10 is 1 less than the maximum number of digits.
-        + 1;  // NUL byte.
+    // digits10 is 1 less than the maximum number of digits.
+    static constexpr size_t kBufSize = std::numeric_limits<std::uint64_t>::digits10 + 1;
 
     explicit ItoA(std::uint64_t i);
+    ItoA(const ItoA&) = delete;
+    ItoA& operator=(const ItoA&) = delete;
 
-    operator StringData() {
-        return {_str, _len};
+    operator StringData() const {
+        return _str;
     }
 
 private:
-    const char* _str{nullptr};
-    std::size_t _len{0};
+    StringData _str;
     char _buf[kBufSize];
 };