/**
* Opt-in request body compression. Wraps an outgoing body in a
* `CompressionStream` so the wire payload is smaller and the server
* sees the matching `Content-Encoding` header.
*
* `CompressionStream` is supported on Node 22+, Bun, Deno, and Baseline
* 2024 browsers — but only for `gzip`, `deflate`, and `deflate-raw`.
* `br` / `zstd` are not in the WHATWG Compression Streams spec; we
* capability-test before encoding and refuse silently if a requested
* format isn't available.
*/
export type CompressFormat = "gzip" | "deflate" | "deflate-raw";
/**
* Resolve the user's `compressRequestBody` option to a concrete format,
* or null if compression should be skipped.
*
* - `false` / `undefined`: skip.
* - `true`: pick the first runtime-supported format, preferring `gzip`.
* - A specific format string: only used when supported on this runtime.
*/
export declare function resolveCompressFormat(option: boolean | CompressFormat | undefined): CompressFormat | null;
/**
* Wrap a body source in a `CompressionStream`. Returns a tuple of the
* compressed `ReadableStream<Uint8Array>` and the matching
* `Content-Encoding` value the caller should set on the request.
*
* - `string` and `Uint8Array` bodies are encoded into a one-shot
*   ReadableStream then piped through.
* - Existing `ReadableStream` bodies are piped through directly.
* - `null` / `undefined` skips entirely (caller falls back to the
*   original empty body).
*/
export declare function compressBody(body: BodyInit | null | undefined, format: CompressFormat): {
	stream: ReadableStream<Uint8Array>;
	encoding: CompressFormat;
} | null;