docs: add helia example

examples/helia.js

@@ -0,0 +1,49 @@
+import * as UnixFS from '@ipld/unixfs'
+import * as raw from 'multiformats/codecs/raw'
+
+/**
+ * Usage:
+ * 
+ * ```js
+ * const helia = await createHelia()
+ * await demo(helia)
+ * ```
+ */
+export const demo = async helia => {
+  const { readable, writable } = new TransformStream()
+
+  // Encode a UnixFS directory of files, writing them to the `writable` side of
+  // the transform stream.
+  const encodeDirectory = async () => {
+    // Create a writer with filesystem like API for encoding files and
+    // directories into IPLD blocks.
+    const writer = UnixFS.createWriter({
+      writable,
+      settings: UnixFS.configure({ fileChunkEncoder: raw, smallFileEncoder: raw })
+    })
+
+    const file = UnixFS.createFileWriter(writer)
+    file.write(new TextEncoder().encode('hello world'))
+    const fileLink = await file.close()
+
+    // Create directory and add the file we encoded above.
+    const dir = UnixFS.createDirectoryWriter(writer)
+    dir.set('hello.txt', fileLink)
+    const dirLink = await dir.close()
+
+    await writer.close()
+    return dirLink
+  }
+
+  // Read the blocks created by the UnixFS encoder from the `readable` side of
+  // the transform stream.
+  const writeBlocks = () => readable.pipeTo(new WritableStream({
+    async write (block) {
+      await helia.blockstore.put(block.cid, block.bytes)
+    }
+  }))
+
+  // Wait for encoding to complete and the root CID to be returned.
+  const [dir] = await Promise.all([encodeDirectory(), writeBlocks()])
+  console.log(`Root: ${dir.cid}`)
+}