upy-fs-hex: Add method to configure the available stoagra size.

Author: microbit-carlos

docs/quick-guide.md

@@ -38,6 +38,9 @@ var fsSize = micropythonFs.getStorageSize();
 var fsAvailableSize = micropythonFs.getStorageUsed();
 var fsUsedSize = micropythonFs.getStorageRemaining();
 
+// You can also provide an artificial storage size
+micropythonFs.setStorageSize(20 * 1024);
+
 // Generate a new hex string or Uint8Array with MicroPython and the files
 var intelHexStrWithFs = micropythonFs.getIntelHex();
 var intelHexBytesWithFs = micropythonFs.getIntelHexBytes();

src/__tests__/micropython-fs-hex.spec.ts

@@ -122,6 +122,75 @@ describe('Test size operations.', () => {
     expect(microbitFs.getStorageUsed()).toEqual(27648);
     expect(microbitFs.getStorageRemaining()).toEqual(0);
   });
+
+  it('Sets a maximum filesystem size via constructor', () => {
+    const microbitFs = new MicropythonFsHex(uPyHexFile, { maxFsSize: 1024 });
+
+    expect(microbitFs.getStorageUsed()).toEqual(0);
+    expect(microbitFs.getStorageRemaining()).toEqual(1024);
+
+    microbitFs.create('chunk1.py', 'first 128 byte chunk');
+    microbitFs.create('chunk2.py', 'second 128 byte chunk');
+    microbitFs.create('chunk3.py', 'thrid 128 byte chunk');
+    microbitFs.create('chunk4.py', 'fouth 128 byte chunk');
+    microbitFs.create('chunk5.py', 'fifth 128 byte chunk');
+    microbitFs.create('chunk6.py', 'sixth 128 byte chunk');
+    microbitFs.create('chunk7.py', 'seventh 128 byte chunk');
+    microbitFs.create('chunk8.py', 'eighth 128 byte chunk');
+    microbitFs.getIntelHex();
+
+    expect(microbitFs.getStorageUsed()).toEqual(1024);
+    expect(microbitFs.getStorageRemaining()).toEqual(0);
+
+    microbitFs.create('chunk9.py', 'This file will not fit');
+    const failCase = () => {
+      microbitFs.getIntelHex();
+    };
+
+    expect(failCase).toThrow(Error);
+  });
+
+  it('Sets a maximum filesystem size via constructor', () => {
+    const microbitFs = new MicropythonFsHex(uPyHexFile);
+    microbitFs.setStorageSize(1024);
+
+    expect(microbitFs.getStorageUsed()).toEqual(0);
+    expect(microbitFs.getStorageRemaining()).toEqual(1024);
+
+    microbitFs.create('chunk1.py', 'first 128 byte chunk');
+    microbitFs.create('chunk2.py', 'second 128 byte chunk');
+    microbitFs.create('chunk3.py', 'thrid 128 byte chunk');
+    microbitFs.create('chunk4.py', 'fouth 128 byte chunk');
+    microbitFs.create('chunk5.py', 'fifth 128 byte chunk');
+    microbitFs.create('chunk6.py', 'sixth 128 byte chunk');
+    microbitFs.create('chunk7.py', 'seventh 128 byte chunk');
+    microbitFs.create('chunk8.py', 'eighth 128 byte chunk');
+    microbitFs.getIntelHex();
+    microbitFs.getIntelHexBytes();
+
+    expect(microbitFs.getStorageUsed()).toEqual(1024);
+    expect(microbitFs.getStorageRemaining()).toEqual(0);
+
+    microbitFs.create('chunk9.py', 'This file will not fit');
+    const failCase1 = () => microbitFs.getIntelHex();
+    const failCase2 = () => microbitFs.getIntelHexBytes();
+
+    expect(failCase1).toThrow(Error);
+    expect(failCase2).toThrow(Error);
+  });
+
+  it('The maximum filesystem size cannot be larger than space available', () => {
+    const failCase1 = () => {
+      const microbitFs = new MicropythonFsHex(uPyHexFile, {
+        maxFsSize: 1024 * 1024,
+      });
+    };
+    const microbitFs = new MicropythonFsHex(uPyHexFile);
+    const failCase2 = () => microbitFs.setStorageSize(1024 * 1024);
+
+    expect(failCase1).toThrow(Error);
+    expect(failCase2).toThrow(Error);
+  });
 });
 
 describe('Test write method.', () => {

src/micropython-fs-hex.ts

@@ -11,6 +11,7 @@ import { SimpleFile } from './simple-file';
 export class MicropythonFsHex implements FsInterface {
   private _intelHex: string;
   private _files: { [id: string]: SimpleFile } = {};
+  private _storageSize: number = 0;
 
   /**
    * File System manager constructor.
@@ -20,14 +21,18 @@ export class MicropythonFsHex implements FsInterface {
    *
    * @param intelHex - MicroPython Intel Hex string.
    */
-  constructor(intelHex: string) {
+  constructor(
+    intelHex: string,
+    { maxFsSize = 0 }: { maxFsSize?: number } = {}
+  ) {
     this._intelHex = intelHex;
     this.importFilesFromIntelHex(this._intelHex);
     if (this.ls().length) {
       throw new Error(
         'There are files in the MicropythonFsHex constructor hex file input.'
       );
     }
+    this.setStorageSize(maxFsSize);
   }
 
   /**
@@ -169,13 +174,31 @@ export class MicropythonFsHex implements FsInterface {
     return files;
   }
 
+  /**
+   * Sets a storage size limit. Must be smaller than available space in
+   * MicroPython.
+   *
+   * @param {number} size - Size in bytes for the filesystem.
+   */
+  setStorageSize(size: number): void {
+    if (size > getIntelHexFsSize(this._intelHex)) {
+      throw new Error(
+        'Storage size limit provided is larger than size available in the MicroPython hex.'
+      );
+    }
+    this._storageSize = size;
+  }
+
   /**
    * Calculate the MicroPython filesystem total size.
+   * If an max storage size limit has been set, it returns this number.
    *
    * @returns Size of the filesystem in bytes.
    */
   getStorageSize(): number {
-    return getIntelHexFsSize(this._intelHex);
+    return this._storageSize
+      ? this._storageSize
+      : getIntelHexFsSize(this._intelHex);
   }
 
   /**
@@ -255,6 +278,9 @@ export class MicropythonFsHex implements FsInterface {
    * @returns A new string with MicroPython and the filesystem included.
    */
   getIntelHex(intelHex?: string): string {
+    if (this.getStorageRemaining() < 0) {
+      throw new Error('There is no storage space left.');
+    }
     const finalHex = intelHex || this._intelHex;
     const files: { [filename: string]: Uint8Array } = {};
     Object.values(this._files).forEach((file) => {
@@ -275,6 +301,9 @@ export class MicropythonFsHex implements FsInterface {
    * @returns A Uint8Array with MicroPython and the filesystem included.
    */
   getIntelHexBytes(intelHex?: string): Uint8Array {
+    if (this.getStorageRemaining() < 0) {
+      throw new Error('There is no storage space left.');
+    }
     const finalHex = intelHex || this._intelHex;
     const files: { [filename: string]: Uint8Array } = {};
     Object.values(this._files).forEach((file) => {