Skip to main content

varTypeMask

varTypeMask = 4095

Example​

function BaseVariantType(const Value: Variant): TVarType;
begin
  Result := VarType(Value) and varTypeMask;
end;

Usage​

varTypeMask selects the low 12 bits of a raw Variant type code so array and by-reference flags can be interpreted separately.

Additional Technical Info​

varTypeMask is the TVarType bit mask $0FFF. Applying it to VarType preserves the low 12-bit base/custom type number and removes the public representation flags varArray ($2000) and varByRef ($4000).

Use separate expressions for separate questions:

Code := VarType(Value);
Base := Code and varTypeMask;
IsArray := (Code and varArray) <> 0;
IsByRef := (Code and varByRef) <> 0;

Do not compare Code and varTypeMask to varArray or varByRef: the mask deliberately removes those flags. Conversely, exact Code = varInteger is false for an Integer array even though its element base type is Integer.

Interpretation limits

  • The base number can identify a built-in or custom Variant type; it does not prove that a malformed/borrowed payload is valid.
  • Masking a by-reference code does not dereference it. Current Delphi's FindVarData-based predicates resolve only the special Variant indirection path before testing.
  • For arrays, the base normally describes element storage but says nothing about dimensions, bounds, locks or size.
  • Do not persist masked numeric codes as a language-independent schema. Velox exposes a subset of current Delphi's constants, and providers can use custom type numbers.

The mask operation is constant-time and side-effect free. It cannot make concurrent mutation or an expired reference safe.

The example is source-reviewed only; no Variant representation was inspected.

External references

Created 2026-07-15