Function writeFileStreaming

packages/dofs/src/fs/writeFile.ts:140–268

(
  db: Database,
  path: string,
  source: ReadableStream<Uint8Array>,
  options: WriteFileOptions,
  now: () => number,
)

// Failure mid-stream leaves blob rows behind; gc() reaps orphans on
// its next pass since no node references them.
async function writeFileStreaming(
  db: Database,
  path: string,
  source: ReadableStream<Uint8Array>,
  options: WriteFileOptions,
  now: () => number,
): Promise<void> {
  const { parts, path: canonical } = canonicalizePath(path);
  if (parts.length === 0) {
    throw createWorkspaceError("EISDIR", "cannot write to the root directory", canonical);
  }
  // Reject before we stage any blob bytes so known failures do not grow
  // orphan blob rows that gc() then has to reap.
  assertNotReadOnly(db, canonical);
  if (options.exclusive) {
    const parentInode = resolveParent(db, parts, canonical);
    const existing = db.one(
      "SELECT 1 FROM vfs_dirents WHERE parent_inode = ? AND name = ?",
      parentInode,
      parts[parts.length - 1],
    );
    if (existing !== undefined) {
      throw createWorkspaceError("EEXIST", `path exists: ${canonical}`, canonical);
    }
  }
  const mode = (options.mode ?? 0o644) & 0o7777;
  const mtime = now();

  const chunkRefs: Array<{ hash: Uint8Array; size: number }> = [];
  // Carry-over buffer: bytes left over from the previous source chunk
  // that didn't fill a CHUNK_SIZE window.
  let carry: Uint8Array | undefined;

  const flush = (chunk: Uint8Array): void => {
    const hash = sha256(chunk);
    stageBlob(db, hash, chunk, mtime);
    chunkRefs.push({ hash, size: chunk.byteLength });
  };

  const reader = source.getReader();
  try {
    while (true) {
      const { value, done } = await reader.read();
      if (done) break;
      if (value === undefined || value.byteLength === 0) continue;
      let input = value;
      if (carry !== undefined) {
        // Splice carry-over onto the front of this source chunk so
        // we can re-window cleanly.
        const merged = new Uint8Array(carry.byteLength + input.byteLength);
        merged.set(carry, 0);
        merged.set(input, carry.byteLength);
        input = merged;
        carry = undefined;
      }
      let offset = 0;
      while (input.byteLength - offset >= CHUNK_SIZE) {
        // Copy the window so the staged blob doesn't alias a