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Base64DecodeBytes

Function Base64DecodeBytes( const Value : string) : TBytes

Example​

procedure ScriptEvent(var Value: variant);
var
  Decoded: TBytes;
begin
  Decoded := Base64DecodeBytes('AQID');
  Value := Length(Decoded);  // 3
end;

Usage​

Base64DecodeBytes decodes standard Base64 text to its exact binary byte sequence.

Parameters

NameTypeDescription
Valuestring, constStandard Base64 text to decode. Velox does not trim or normalise it first.

Returns

A dynamic byte array containing the decoded binary value. Empty input produces a zero-length byte array.

Behaviour

  • The expected alphabet is standard Base64 (A-Z, a-z, 0-9, + and /) with optional = padding.
  • Whitespace and other characters outside that alphabet are skipped by the Velox decoder.
  • Every decoded byte, including zero bytes, is retained in the returned TBytes value.
  • Velox does not inspect the file type, text encoding or structure of the result.

Errors

Do not expect malformed text to raise an exception consistently. Allocation and Velox exceptions are not caught and propagate to the script.

Additional Technical Info​

Base64DecodeBytes decodes standard Base64 text to a TBytes value without interpreting the result as text. It is the appropriate Base64 decoder for binary payloads, file content and data whose character encoding is unknown.

The example is source-reviewed and was not executed by the documentation workflow.

Implementation

The Velox wrapper creates a new Delphi TBase64Encoding with line length 0, calls DecodeStringToBytes, and frees the encoder in a finally block. No character-set conversion is applied to the decoded bytes.

Edge cases and quirks

  • The decoder is deliberately permissive rather than a strict Base64 validator. It can ignore invalid characters and decode a final two- or three-symbol fragment, so malformed or truncated input may return partial bytes.
  • URL-safe Base64 is not translated. Its - and _ symbols are skipped, which may silently produce the wrong bytes.
  • An empty array is a valid result and is indistinguishable from decoding an empty input unless the caller also validates the source.
  • Base64 provides neither confidentiality nor integrity.

Side effects

None beyond temporary allocation. The helper performs no file or network I/O.

Performance and concurrency

Memory use is proportional to the supplied text and decoded result. A fresh encoder is used for every call, with no Velox shared mutable state.

Remarks

Apply independent length, format or cryptographic-integrity checks when the decoded bytes cross a trust boundary. Successful decoding means only that some bytes could be reconstructed.

Related entries

External references

Created 2026-07-15