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FileHash

property FileHash: String read write;

Example​

procedure ScriptEvent(var Value: Variant);
begin
  if FileCon <> nil then
    Value := FileCon.FileHash <> ''
  else
    Value := False;
end;

Usage​

FileHash gets or replaces FileCon's cached hash string, calculated on first access from nonempty legacy FileData when blank.

Freshness and scope limitations

  • A nonempty FileData assignment recomputes the hash; an empty assignment leaves the previous hash.
  • Reset does not clear FileData or FileHash.
  • Disk content changes do not invalidate/recompute the cache. The hash is over the in-memory Velox string representation, not an independently re-read file byte stream.
  • A hash match is not authenticity, digital signature, authorisation or proof that I/O succeeded. SHA-384 alone has no secret key.
  • Velox log/database code can persist/copy this value, so arbitrary/stale script writes can contaminate audit comparison data.

Additional Technical Info​

FileHash exposes FileCon's cached content-hash string.

Getter/setter implementation

If the cached hash is empty and FileData is nonempty, the getter hashes that Delphi string through Velox's LockBox SHA-384 wrapper, stores the hexadecimal result and returns it. Otherwise it returns the cached string unchanged.

The scripting setter directly replaces the cache. It does not validate format/length, hash data or compare anything. A caller can therefore store arbitrary text that later reads return as though it were a hash.

Performance, security and concurrency

Cached reads are cheap; a lazy hash scans all FileData and allocates cryptographic state. Hashes can still identify/signal sensitive content and should not be broadly exposed. The content/cache pair is unsynchronised.

Related entries

Created 2026-07-15