initial

.eslintrc.js

@@ -0,0 +1,16 @@
+module.exports = {
+  env: {
+    browser: true,
+    node: true,
+    es2021: true,
+    jest: true
+  },
+  extends: 'eslint:recommended',
+  parserOptions: {
+    ecmaVersion: 12,
+    sourceType: 'module'
+  },
+  rules: {
+    'no-unused-vars': 'off'
+  }
+};

babel.config.js

@@ -1 +1 @@
-module.exports = {presets: ['@babel/preset-env']}
+module.exports = { plugins: ['@babel/plugin-transform-modules-commonjs'] };

backend-indexeddb.js

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+export class IndexedDBBackend {
+  readChunks(fileName, positions, chunkSize) {
+    // TODO:
+    // * Sort positions and find contiguous chunks
+    // * Run a query for each contiguous chunk
+    // * Do all this in another syncify worker!
+
+    // return this.syncWorker.readChunks(fileName, positions, chunkSize);
+
+    return [];
+  }
+
+  writeChunks(writes) {
+    // Call out to idb (sync!)
+
+    // return this.syncWorker.writeChunks(fileName, positions, chunkSize);
+
+    return [];
+  }
+}

backend-memory.js

@@ -0,0 +1,80 @@
+export default class MemoryBackend {
+  constructor(files, defaultChunkSize) {
+    this.files = Object.fromEntries(
+      Object.entries(files).map(([name, data]) => {
+        return [name, { data, size: data.byteLength }];
+      })
+    );
+    this.defaultChunkSize = defaultChunkSize;
+  }
+
+  getFile(fileName) {
+    return this.files[fileName];
+  }
+
+  getOrCreateFile(fileName) {
+    if (this.files[fileName] == null) {
+      this.files[fileName] = { data: new ArrayBuffer(0), size: 0 };
+    }
+    return this.files[fileName];
+  }
+
+  deleteFile(fileName) {
+    this.files[fileName] = null;
+  }
+
+  readMeta(fileName, defaultMeta) {
+    let exists = this.getFile(fileName) != null;
+    let file = this.getOrCreateFile(fileName);
+    return exists
+      ? { size: file.data.byteLength, chunkSize: this.defaultChunkSize }
+      : defaultMeta;
+  }
+
+  writeMeta(fileName, meta) {
+    let file = this.getOrCreateFile(fileName);
+    file.size = meta.size;
+  }
+
+  readChunks(fileName, positions, chunkSize) {
+    console.log('_reading', fileName, positions);
+    // if (positions.length > 0) {
+    //   console.log('reading', positions);
+    // }
+    let data = this.files[fileName].data;
+
+    return positions.map(pos => {
+      let buffer = new ArrayBuffer(chunkSize);
+
+      if (pos < data.byteLength) {
+        new Uint8Array(buffer).set(
+          new Uint8Array(data, pos, Math.min(chunkSize, data.byteLength - pos))
+        );
+      }
+
+      return { pos, data: buffer };
+    });
+  }
+
+  writeChunks(fileName, writes) {
+    console.log('_writing', fileName, writes);
+    // if (writes.length > 0) {
+    //   console.log('writing', writes.map(w => w.pos));
+    // }
+    let file = this.getOrCreateFile(fileName);
+    let data = file.data;
+
+    for (let write of writes) {
+      let fullLength = write.pos + write.data.byteLength;
+
+      if (fullLength > data.byteLength) {
+        // Resize file
+        let buffer = new ArrayBuffer(fullLength);
+        new Uint8Array(buffer).set(new Uint8Array(data));
+        this.files[fileName].data = data = buffer;
+      }
+
+      new Uint8Array(data).set(new Uint8Array(write.data), write.pos);
+    }
+  }
+}