@struktoai/mirage-core/dist/workspace/session/rng.js

A Unified Virtual Filesystem For AI Agents

// ========= Copyright 2026 @ Strukto.AI All Rights Reserved. =========
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ========= Copyright 2026 @ Strukto.AI All Rights Reserved. =========
import { RANDOM_A, RANDOM_M, RANDOM_MAX, RANDOM_Q, RANDOM_R, RANDOM_ZERO_SEED, } from "../../shell/constants.js";
/** A first seed for a generator never assigned one, drawn from the
 * workspace's id source, so every generator starts somewhere else, as
 * bash's mixes in the time and each shell's own pid, and a seeded
 * workspace replays it. */
export function initialSeed(ids) {
    return ids.randomU32();
}
/** One step of bash's RANDOM generator: Park-Miller through
 * Schrage's method, a zero state stepping from the fixed seed. */
export function stepState(state) {
    const ret = state === 0 ? RANDOM_ZERO_SEED : state;
    const high = Math.floor(ret / RANDOM_Q);
    const low = ret - RANDOM_Q * high;
    const step = RANDOM_A * low - RANDOM_R * high;
    return step < 0 ? step + RANDOM_M : step;
}
/** The `$RANDOM` value a state renders as in bash: the two 16-bit
 * halves folded, keeping 15 bits. */
export function valueOf(state) {
    return ((state >>> 16) ^ (state & 0xffff)) & RANDOM_MAX;
}
/** One `$RANDOM` draw: step until the value differs from the last one,
 * as bash does, and return the new state with it. `last`
 * is 0 after a seed. */
export function draw(state, last) {
    for (;;) {
        state = stepState(state);
        const value = valueOf(state);
        if (value !== last)
            return [state, value];
    }
}
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