`base64_decode`

Decode a base64 string to text or write decoded bytes to a file.

Parameters

inputstringone of input or source_key: Base64 string to decode; supports ${ctx.key} interpolation.
source_keystringsee above: Context key containing the base64 string to decode.
output_keystringdefault "base64_decoded": Context key for the decoded output.
output_filestring: File path to write decoded bytes to.
url_safebooldefault false: Expect URL-safe base64 alphabet.

Context Output

If no output_file: <output_key> (default base64_decoded) — the decoded string.
If output_file is set: <output_key>_path — the file path written to.

File safety

output_file streams the decoded bytes through the same atomic, tracked write path as write_file. The decoded length is derived from the encoded input and admitted against IRONFLOW_MAX_FILE_BYTES (default 50 MiB) before any worker or decoded-byte allocation. An oversized payload fails with exactly one message:

base64_decode: final payload is <decoded> bytes, exceeds the IRONFLOW_MAX_FILE_BYTES limit (<limit>)

Decoding then runs in bounded chunks directly into the staged file, so the decoded payload is never held in memory; only the text output path (no output_file) decodes in memory. File errors name the destination once, as <error>; output_file '<path>'.

Valid directory aliases (including macOS /tmp) are accepted, but destination file symlinks and special files are refused. Missing parent directories are created. An existing regular file is replaced only after a complete, synced write; malformed input, byte-limit, cancellation or write failure preserves it and removes temporary output.

Unix pins the resolved destination directory and uses handle-relative writes. Other platforms retain observed-path checks and atomic replacement; protect the parent namespace against concurrent hostile mutation. This does not impose a filesystem sandbox on a trusted flow's configured destination.

Example

local flow = Flow.new("decode_demo")

flow:step("decode", nodes.base64_decode({
    input = "SGVsbG8sIFdvcmxkIQ==",
    output_key = "decoded"
}))

flow:step("log", nodes.log({
    message = "Decoded: ${ctx.decoded}"
})):depends_on("decode")

return flow