/**
 * What an fopen-style mode string says about a handle.
 *
 * One vocabulary for every dialect that opens by mode: quickjs's
 * `std.open` passes these strings verbatim, and Python's preview1
 * oflags/rights/fdflags translate onto the same facts.
 */
export interface OpenMode {
    /** The handle may read (r, +). */
    readable: boolean;
    /** The handle may mutate its buffer (w, a, x, +). */
    writable: boolean;
    /** Opening discards existing content (w). */
    truncate: boolean;
    /** The position starts at the end (a). */
    append: boolean;
    /** A missing file is created (w, a, x). */
    create: boolean;
    /** An existing file refuses the open (x). */
    exclusive: boolean;
    /** The handle carries bytes, not text (b). */
    binary: boolean;
}
/**
 * Read an fopen-style mode string into its facts, validating it.
 *
 * The rule is CPython's, the stricter of the two parsers this
 * replaced — one base, at most one each of `+`, `b`, `t`, and never
 * `b` together with `t` — widened by one C-dialect spelling: `wx`,
 * fopen's exclusive create, which CPython spells as a bare `x`. Both
 * dialects open by mode through this one parser, so it accepts the
 * union. A guest engine that tolerates looser spellings still (C
 * fopen reads `rr` as `r`) renders this refusal in its own dialect at
 * its own boundary.
 *
 * Args:
 *   mode: the mode as the caller spelled it (`r`, `w+b`, `a`, `wx`, ...).
 *
 * Throws:
 *   Error: the mode does not parse, in CPython's own wording.
 */
export declare function parseMode(mode: string): OpenMode;
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