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TvxHash

TvxHash = class(TObject)

Example​

procedure ScriptEvent(var Value: variant);
var
  Hasher: TvxHash;
begin
  Hasher := TvxHash.Create;
  try
    Value := Hasher.HashString('Customer reference');
  finally
    Hasher.Free;
  end;
end;

Usage​

TvxHash provides stateful SHA-384 hashing and exact digest change comparison over nonempty UTF-8 string data.

Additional Technical Info​

TvxHash wraps TurboPower LockBox3 SHA-384 for string hashing and stateful change detection.

The registered surface consists of Create, HashString, HasChanged and read-only RowHash.

Two acquisition modes

  • TvxHash.Create returns a caller-owned object that the script must Free.
  • The global Hash variable returns an action-owned object created lazily by TvxActionMan. Every scripter in that action receives the same object; do not free or retain it beyond the action.

Digest format

For nonempty input, LockBox converts the Delphi string to UTF-8 and applies SHA-384. The 48-byte digest is emitted by Velox as 96 uppercase hexadecimal characters with no prefix or separators.

SHA-384 is deterministic and unkeyed. It can identify ordinary content changes but is not an HMAC, signature, encryption or suitable password-storage scheme. The helpers compare strings normally, not in constant time.

State model and quirks

HashString returns a digest and burns the internal output but does not set RowHash. HasChanged sets RowHash to its newly computed digest, leaves the internal digest retained and compares the caller's hash exactly/case-sensitively.

The vendored LockBox string hasher skips hashing when the input string is empty. As a result, these APIs do not return the standard SHA-384 empty-message digest. On new/burned state, HashString('') returns ''; after a nonempty HasChanged, it can instead return that retained prior digest and then burn it. HasChanged(..., '') has the same retained-or-empty dependency. Treat empty as an unsupported hashing input unless this stateful behavior is explicitly desired.

Concurrency and lifetime

The object owns mutable hash/output/RowHash state and has no lock. Do not call one instance concurrently. This is especially important for the action-shared global Hash: copy RowHash immediately after the corresponding HasChanged call and do not assume it remains yours across another script callback.

Hashing is synchronous and allocates a UTF-8 byte array proportional to input size. Invalid/freed object state and allocation/algorithm errors can raise.

External references

Created 2026-07-15