feat(node): expose seek, tell, bounded read, readRanges and close on BlobFile (#4348)

Closes #4300.

The TypeScript `BlobFile` only had `size()`, `read()` and `readRange()`,
while the Rust `BlobFile` behind it also has `seek`, `tell`,
`read_up_to`, `read_ranges` and `close`. This exposes those on the Node
binding:

- `read(maxBytes?)` reads at most `maxBytes` from the cursor (Rust
`read_up_to`). Without the argument it reads to the end, as before.
- `readRanges([{ start, end }, ...])` reads several half-open ranges and
returns one buffer per range, in order. Like `readRange`, it does not
move the cursor.
- `seek(position)` and `tell()` move and report the cursor.
- `close()` releases the handle, and `isClosed()` reports it. Every
read, `seek` and `tell` after `close()` fails with "blob file is already
closed". A second `close()` does nothing. The binding keeps its own
`closed` flag, the same way the Python `BlobFile` does.

Offsets and lengths are `bigint`, like `readRange` and `size()`.
`BlobRange` is exported as a type.

The new tests in `table.test.ts` cover chunked reads with
`read(maxBytes)`, `seek` and `tell`, a negative seek position,
`readRanges` order and cursor, a `readRanges` end past the blob size,
and reads after `close()`. The Node docs under `docs/src/js` are
regenerated with `pnpm run docs`.

I left the `ReadableStream`/async iterator idea from the issue out of
this PR. The AbortSignal work in #4288 touches the same methods, so it
can follow on top of this.

nodejs/lancedb/blob.ts

@@ -141,13 +141,14 @@ export class BlobFile {
   }
 
   /**
-   * Reads from the cursor to the end and advances the cursor.
+   * Reads from the cursor and advances the cursor.
    *
-   * A second call returns an empty buffer. {@link BlobFile.readRange} does
-   * not move the cursor.
+   * Reads to the end when `maxBytes` is omitted, or at most `maxBytes` bytes
+   * otherwise. Returns an empty buffer at the end of the blob.
+   * {@link BlobFile.readRange} does not move the cursor.
    */
-  read(): Promise<Buffer> {
-    return this.inner.read();
+  read(maxBytes?: bigint): Promise<Buffer> {
+    return this.inner.read(maxBytes);
   }
 
   /**
@@ -158,8 +159,47 @@ export class BlobFile {
   readRange(start: bigint, end: bigint): Promise<Buffer> {
     return this.inner.readRange(start, end);
   }
+
+  /**
+   * Reads several half-open byte ranges. Returns one buffer per range, in
+   * the order given.
+   *
+   * Fails when any `end` is past the blob size. Does not move the cursor.
+   */
+  readRanges(ranges: BlobRange[]): Promise<Buffer[]> {
+    return this.inner.readRanges(ranges);
+  }
+
+  /** Moves the cursor to `position`, in bytes from the start of the blob. */
+  seek(position: bigint): Promise<void> {
+    return this.inner.seek(position);
+  }
+
+  /** Returns the cursor position in bytes. */
+  tell(): Promise<bigint> {
+    return this.inner.tell();
+  }
+
+  /**
+   * Releases the handle. Reads after `close()` fail. Calling it again does
+   * nothing.
+   */
+  close(): Promise<void> {
+    return this.inner.close();
+  }
+
+  /** Returns true after {@link BlobFile.close}. */
+  isClosed(): boolean {
+    return this.inner.isClosed();
+  }
 }
 
+/** A half-open byte range `[start, end)` for {@link BlobFile.readRanges}. */
+export type BlobRange = {
+  start: bigint;
+  end: bigint;
+};
+
 export function coerceBlobValue(value: unknown): BlobInput | null {
   if (value == null) {
     return null;

nodejs/lancedb/index.ts

@@ -84,7 +84,7 @@ export {
 } from "./arrow";
 
 export { blob, isBlobField, BlobFile } from "./blob";
-export type { BlobOptions } from "./blob";
+export type { BlobOptions, BlobRange } from "./blob";
 
 export {
   Connection,