upy-fs-builder: Add function to calculate a MicroPython fs total size.

Author: microbit-carlos

docs/quick-guide.md

@@ -31,6 +31,7 @@ var fileSizeInBytes = micropythonFs.size('filename.txt');
 var fileList = micropythonFs.ls();
 
 var intelHexWithFs = micropythonFs.getIntelHex();
+var MicroPythonFsSize = micropythonFs.getFsSize();
 ```
 
 Public interface can be found in the `src/fs-interface.ts` file.
@@ -41,7 +42,7 @@ To add and remove the Python code using the old format:
 ```js
 var finalHexStr = microbitFs.addIntelHexAppendedScript(originalIntelHexStr, 'print("hello world!")');
 if (microbitFs.isAppendedScriptPresent(finalHexStr)) {
-  var pythonCode = microbitFs.getIntelHexAppendedScript(finalHexStr)
+  var pythonCode = microbitFs.getIntelHexAppendedScript(finalHexStr);
 }
 ```
 

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

@@ -7,6 +7,7 @@ import {
   addIntelHexFile,
   addIntelHexFiles,
   getIntelHexFiles,
+  getIntelHexFsSize,
   testResetFileSystem,
 } from '../micropython-fs-builder';
 
@@ -562,5 +563,15 @@ describe('Reading files from the filesystem.', () => {
   // TODO: Read test with chunks that point to each other in an infinite loop
   // TODO: Read test with chunks that don't point to each other in Marker/Tail
   // TODO: Read test with chunks using the all the start file markers
+});
+
+describe('Calculate sizes.', () => {
+  it('Get how much available fs space there is in a MicroPython hex file.', () => {
+    const totalSize = getIntelHexFsSize(uPyHexFile);
+
+    // Calculated by hand from the uPyHexFile v1.0.1 release.
+    expect(totalSize).toEqual(27 * 1024);
+  });
+
   // TODO: Test calculateFileSize()
 });

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

@@ -500,6 +500,17 @@ describe('Test importing files from hex.', () => {
   });
 });
 
+describe('Test MicroPython hex filesystem size.', () => {
+  it('Get how much available fs space there is in a MicroPython hex file.', () => {
+    const micropythonFs = new MicropythonFsHex(uPyHexFile);
+
+    const totalSize = micropythonFs.getFsSize();
+
+    // Calculated by hand from the uPyHexFile v1.0.1 release.
+    expect(totalSize).toEqual(27 * 1024);
+  });
+});
+
 /*
 import { addIntelHexAppendedScript } from '../appended-script';
 

src/micropython-fs-builder.ts

@@ -400,6 +400,14 @@ function getIntelHexFiles(
   const startAddress: number = getStartAddress(hexMap);
   const endAddress: number = getLastPageAddress(hexMap);
 
+  // TODO: endAddress as the getLastPageAddress works now because this
+  // library uses the last page as the "persistent" page, so the filesystem does
+  // end there. In reality, the persistent page could be the first or the last
+  // page, so we should get the end address as the magnetometer page and then
+  // check if the persistent marker is present in the first of last page and take that
+  // into account in the memory range calculation.
+  // Note that the persistent marker is only present at the top of the page
+
   // Iterate through the filesystem to collect used chunks and file starts
   const usedChunks: { [index: number]: Uint8Array } = {};
   const startChunkIndexes: number[] = [];
@@ -480,9 +488,25 @@ function getIntelHexFiles(
   return files;
 }
 
+/**
+ * Calculate the MicroPython filesystem size.
+ *
+ * @param intelHex - The MicroPython Intel Hex string.
+ * @returns Size of the filesystem in bytes.
+ */
+function getIntelHexFsSize(intelHex: string): number {
+  const intelHexClean = cleanseOldHexFormat(intelHex);
+  const intelHexMap: MemoryMap = MemoryMap.fromHex(intelHexClean);
+  const startAddress: number = getStartAddress(intelHexMap);
+  const endAddress = getEndAddress(intelHexMap);
+  // Remember that one page is used as persistent page
+  return endAddress - startAddress - FLASH_PAGE_SIZE;
+}
+
 export {
   addIntelHexFile,
   addIntelHexFiles,
   calculateFileSize,
   getIntelHexFiles,
+  getIntelHexFsSize,
 };

src/micropython-fs-hex.ts

@@ -4,6 +4,7 @@ import {
   addIntelHexFiles,
   calculateFileSize,
   getIntelHexFiles,
+  getIntelHexFsSize,
 } from './micropython-fs-builder';
 import { SimpleFile } from './simple-file';
 
@@ -227,4 +228,13 @@ export class MicropythonFsHex implements FsInterface {
     });
     return addIntelHexFiles(finalHex, files);
   }
+
+  /**
+   * Calculate the MicroPython filesystem total size.
+   *
+   * @returns Size of the filesystem in bytes.
+   */
+  getFsSize(): number {
+    return getIntelHexFsSize(this._intelHex);
+  }
 }