@struktoai/mirage-core/dist/core/ram/truncate.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 { record, startOp } from "../../observe/context.js";
import { VFSName } from "../../types.js";
import { nowIso } from "../../utils/dates.js";
import { norm } from "../../utils/path.js";
import { einval } from "../../errors/fs.js";
import { activePipe } from "../dev/device.js";
import { checkCapacity, checkDestParents, checkWriteTarget } from "./dest.js";
/**
 * Set one key's length, padding with NULs or cutting it short. A live pipe
 * has no length to set: EINVAL, as ftruncate(2) answers for one (GNU:
 * `truncate -s 0 >(cat)` is "Invalid argument"), and for a length that is not
 * a whole, non-negative number of bytes. Mirrors Python's truncate.
 */
export async function truncate(accessor, path, length, noCreate = false) {
    const timer = startOp();
    const p = norm(path.mountPath);
    if (activePipe(accessor, p) !== null || !Number.isSafeInteger(length) || length < 0) {
        throw einval(path);
    }
    checkDestParents(accessor, path, p);
    checkWriteTarget(accessor, path, p);
    if (noCreate && !accessor.store.files.has(p))
        return;
    checkCapacity(accessor, path, p, length);
    const existing = accessor.store.files.get(p) ?? new Uint8Array();
    const out = new Uint8Array(length);
    out.set(existing.subarray(0, Math.min(existing.byteLength, length)));
    accessor.store.files.set(p, out);
    accessor.store.modified.set(p, nowIso());
    record('truncate', path.virtual, VFSName.RAM, 0, timer);
    return Promise.resolve();
}
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