@struktoai/mirage-core/dist/core/ram/pwrite.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 { spliceWindow } from "../../utils/ranges.js";
import { activeDevice, activePipe } from "../dev/device.js";
import { checkCapacity, checkDestParents, checkWriteTarget } from "./dest.js";
/**
 * Write bytes at an offset of one key. A live pipe has no offset: its bytes
 * go into the pipe, in the order they are written, which is how an open
 * descriptor delivers to a FIFO (`exec >"$1"` and a link to a substitution
 * write through here). A device that discards writes (`/dev/null`) keeps
 * nothing, so windows written into it pad nothing up to their offset. Mirrors
 * Python's pwrite.
 */
export async function pwrite(accessor, path, data, offset, signal) {
    const timer = startOp();
    const p = norm(path.mountPath);
    const pipe = activePipe(accessor, p);
    if (pipe !== null) {
        await pipe.write(data, path, signal);
        record('pwrite', path.virtual, VFSName.RAM, data.byteLength, timer);
        return;
    }
    checkDestParents(accessor, path, p);
    checkWriteTarget(accessor, path, p);
    if (activeDevice(accessor, p) === null) {
        const existing = accessor.store.files.get(p) ?? new Uint8Array();
        if (data.byteLength > 0) {
            const end = Math.max(existing.byteLength, offset + data.byteLength);
            checkCapacity(accessor, path, p, end);
        }
        accessor.store.files.set(p, spliceWindow(existing, offset, data));
    }
    accessor.store.modified.set(p, nowIso());
    record('pwrite', path.virtual, VFSName.RAM, data.byteLength, timer);
}
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