Add slice and bytelength to make our filetypes compatible with how hyparquet is accessing files

Author: rwblair

src/files/browser.ts

@@ -29,6 +29,10 @@ export class BIDSFileBrowser implements BIDSFile {
     return this.#file.size
   }
 
+  get size(): number {
+    return this.#file.size
+  }
+
   get stream(): ReadableStream<Uint8Array> {
     return this.#file.stream()
   }
@@ -44,6 +48,12 @@ export class BIDSFileBrowser implements BIDSFile {
   async readBytes(size: number, offset = 0): Promise<Uint8Array<ArrayBuffer>> {
     return new Uint8Array(await this.#file.slice(offset, size).arrayBuffer())
   }
+
+  async slice(start: number, end: number): Promise<ArrayBuffer> {
+    return (await this.readBytes(end - start, start)).buffer
+  }
+
+  /**
 }
 
 /**

src/files/deno.ts

@@ -45,6 +45,10 @@ export class BIDSFileDeno implements BIDSFile {
     return this.#fileInfo ? this.#fileInfo.size : -1
   }
 
+  get byteLength(): number {
+    return this.#fileInfo ? this.#fileInfo.size : -1
+  }
+
   get stream(): ReadableStream<Uint8Array> {
     const handle = this.#openHandle()
     return handle.readable
@@ -87,6 +91,9 @@ export class BIDSFileDeno implements BIDSFile {
     return buf.subarray(0, nbytes)
   }
 
+  async slice(start: number, end: number): Promise<ArrayBuffer> {
+    return (await this.readBytes(end - start, start)).buffer
+  }
   /**
    * Return a Deno file handle
    */

src/files/parquet.ts

@@ -6,7 +6,7 @@ import { createUTF8Stream } from './streams.ts'
 export async function loadParquet(file: BIDSFile, maxRows: number = -1): Promise<ColumnsMap> {
   let columnsMap = new ColumnsMap()
   const readOpts: ParquetReadOptions = {
-    file: (await file.readBytes(file.size)).buffer,
+    file: file,
     // @ts-expect-error
     onChunk: (data) => columnsMap[data.columnName] = data.columnData.map(entry => String(entry)), 
   }

src/types/filetree.ts

@@ -15,6 +15,10 @@ export interface BIDSFile {
   text: () => Promise<string>
   // Read a range of bytes
   readBytes: (size: number, offset?: number) => Promise<Uint8Array<ArrayBuffer>>
+  // Alternative to readBytes used for ArrayBuffer compatibility
+  slice: (start: number, end: number) => Promise<ArrayBuffer>
+  // Alternative to size used for ArrayBuffer compatibility
+  byteLength: number
   // Access the parent directory
   parent: FileTree
   // File has been viewed