Function openWriteBufferForCreateSync

packages/dofs/src/fs/writeFile.ts:552–583

(
  db: Database,
  path: string,
  options: WriteFileOptions,
  now: () => number,
)

// Throws EEXIST if a path already resolves to a live node or to
// another pending buffer.
export function openWriteBufferForCreateSync(
  db: Database,
  path: string,
  options: WriteFileOptions,
  now: () => number,
): void {
  const { path: canonical } = canonicalizePath(path);
  assertNotReadOnly(db, canonical);
  if (getPendingWriteBufferByPath(db, canonical) !== undefined) {
    throw createWorkspaceError("EEXIST", `path exists: ${canonical}`, canonical);
  }
  const [parentInode, leafName] = parentAndNameForResolvedPath(db, path);
  const existing = db.one<{ child_inode: number }>(
    "SELECT child_inode FROM vfs_dirents WHERE parent_inode = ? AND name = ?",
    parentInode,
    leafName,
  );
  if (existing !== undefined) {
    throw createWorkspaceError("EEXIST", `path exists: ${canonical}`, canonical);
  }
  const mode = (options.mode ?? 0o644) & 0o7777;
  const mtime = now();
  const pendingInode = allocatePendingInode(db);
  setWriteBuffer(db, pendingInode, {
    buf: new Uint8Array(0),
    size: 0,
    dirty: true,
    openCount: 1,
    mode,
    pending: { parentInode, leafName, canonicalPath: canonical, pendingInode, mtime },
  });
}

// Release one open of an inode's write buffer. When the open count
// reaches zero, commit the buffered bytes to chunk rows and drop