add cache to idb

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@picovoice/web-utils",
-  "version": "1.4.0",
+  "version": "1.4.1",
   "description": "Picovoice web utility functions",
   "author": "Picovoice",
   "license": "Apache-2.0",

src/pv_file_idb.ts

@@ -38,20 +38,55 @@ export function getDB(): Promise<IDBDatabase> {
   });
 }
 
+/**
+ * Cache Settings
+ */
+class PvCache {
+  private _pos: number;
+  private _data: Uint8Array;
+
+  constructor() {
+    this._pos = 0;
+    this._data = new Uint8Array();
+  }
+
+  public get(bytes: number): Uint8Array | undefined {
+    if (this._pos >= this._data.length) {
+      return undefined;
+    }
+
+    const res = this._data.slice(this._pos, this._pos + bytes);
+    this._pos += bytes;
+    return res;
+  }
+
+  public set(pos: number, data: Uint8Array) {
+    this._pos = pos;
+    this._data = data;
+  }
+
+  public clear() {
+    this._pos = 0;
+    this._data = new Uint8Array();
+  }
+}
+
 /**
  * PvFile Class
  * This class mocks the file system using IndexedDB.
  * IndexedDB is REQUIRED.
  */
 export class PvFileIDB extends PvFile {
-  private readonly _pageSize = 65536;
+  private _pageSize = 65536;
 
   private readonly _db: IDBDatabase;
   private readonly _mode: IDBTransactionMode;
 
   private _pagePtr = 0;
   private _pageOffset = 0;
 
+  private _cache: PvCache;
+
   /**
    * Constructor of PvFile instance.
    * @param path The path of a file.
@@ -65,6 +100,8 @@ export class PvFileIDB extends PvFile {
     this._meta = meta;
     this._db = db;
     this._mode = mode;
+
+    this._cache = new PvCache();
   }
 
   /**
@@ -155,9 +192,27 @@ export class PvFileIDB extends PvFile {
       const totalElems = maxToCopy - (maxToCopy % size);
       const buffer = new Uint8Array(totalElems);
 
+      // check if there's data in cache
+      const res = this._cache.get(totalElems);
+      if (res) {
+        copied += res.length;
+        this._pageOffset += res.length;
+        if (this._pageOffset === this._pageSize) {
+          this._pagePtr += 1;
+          this._pageOffset = 0;
+        }
+
+        if (maxToCopy === copied) {
+          resolve(res);
+          return;
+        }
+
+        buffer.set(res);
+      }
+
       const keyRange = IDBKeyRange.bound(
         `${this._path}-${PvFileIDB.createPage(this._pagePtr)}`,
-        `${this._path}-${PvFileIDB.createPage(this._meta!.numPages)}`
+        `${this._path}-${PvFileIDB.createPage(this._pagePtr + Math.floor(totalElems / this._pageSize) + 1)}`
       );
 
       const store = this._store;
@@ -178,12 +233,23 @@ export class PvFileIDB extends PvFile {
         }
         if (copied < totalElems) {
           cursor.continue();
+        } else {
+          if (this._pageOffset !== 0) {
+            this._cache.set(this._pageOffset, cursor.value);
+          } else {
+            this._cache.clear();
+          }
+
+          if (store.transaction?.commit) {
+            store.transaction?.commit();
+          }
         }
       };
 
-      store.transaction.onerror = () => {
+      req.onerror = () => {
         reject(store.transaction.error);
       };
+
       store.transaction.oncomplete = () => {
         resolve(buffer.slice(0, copied));
       };
@@ -247,6 +313,10 @@ export class PvFileIDB extends PvFile {
         store.delete(keyRange);
       }
 
+      if (store.transaction?.commit) {
+        store.transaction?.commit();
+      }
+
       store.transaction.onerror = () => {
         reject(store.transaction.error);
       };
@@ -296,6 +366,8 @@ export class PvFileIDB extends PvFile {
 
     this._pageOffset = newOffset % this._pageSize;
     this._pagePtr = Math.floor(newOffset / this._pageSize);
+
+    this._cache.clear();
   }
 
   /**
@@ -349,6 +421,13 @@ export class PvFileIDB extends PvFile {
     return (this._pagePtr >= (this._meta!.numPages - 1)) && (this._pageOffset >= (this._meta!.size % this._pageSize));
   }
 
+  /**
+   * Set page size.
+   */
+  public setPageSize(size: number) {
+    this._pageSize = size;
+  }
+
   /**
    * Creates an index which as a key to save page data to IndexedDB.
    * This formats the file into 0000, 0001, 0002 ...