ihex: Add convertExtSegToLinAddressRecord() function.

Author: microbit-carlos

src/__tests__/ihex.spec.ts

@@ -1,3 +1,9 @@
+/**
+ * Tests for ihex module.
+ *
+ * (c) 2020 Micro:bit Educational Foundation and contributors.
+ * SPDX-License-Identifier: MIT
+ */
 import * as ihex from '../ihex';
 
 describe('Test createRecord() for standard records', () => {
@@ -397,6 +403,43 @@ describe('Test convertRecordTo()', () => {
   });
 });
 
+describe('Test convertExtSegToLinAddressRecord()', () => {
+  it('Converts valid Extended Segment Address Records into Linear', () => {
+    expect(ihex.convertExtSegToLinAddressRecord(':020000020000FC')).toEqual(
+      ':020000040000FA'
+    );
+    expect(ihex.convertExtSegToLinAddressRecord(':020000021000EC')).toEqual(
+      ':020000040001F9'
+    );
+    expect(ihex.convertExtSegToLinAddressRecord(':020000022000DC')).toEqual(
+      ':020000040002F8'
+    );
+    expect(ihex.convertExtSegToLinAddressRecord(':020000023000CC')).toEqual(
+      ':020000040003F7'
+    );
+    expect(ihex.convertExtSegToLinAddressRecord(':020000024000BC')).toEqual(
+      ':020000040004F6'
+    );
+    expect(ihex.convertExtSegToLinAddressRecord(':0200000270008C')).toEqual(
+      ':020000040007F3'
+    );
+  });
+
+  it('Throws error with an invalid Extended Segment Address', () => {
+    expect(() => {
+      ihex.convertExtSegToLinAddressRecord(':0200000270018C');
+    }).toThrow('Invalid Extended Segment Address record');
+
+    expect(() => {
+      ihex.convertExtSegToLinAddressRecord(':0300000271008C');
+    }).toThrow('Invalid Extended Segment Address record');
+
+    expect(() => {
+      ihex.convertExtSegToLinAddressRecord(':030000027000FF8C');
+    }).toThrow('Invalid Extended Segment Address record');
+  });
+});
+
 describe('Test iHexToRecordStrs()', () => {
   it('Normal hex file string', () => {
     expect(

src/ihex.ts

@@ -360,6 +360,28 @@ function convertRecordTo(iHexRecord: string, recordType: RecordType): string {
   return `${START_CODE_STR}${recordContentStr}${checksumStr}`;
 }
 
+/**
+ * Converts and Extended Segment Linear Address record to an Extended Linear
+ * Address record.
+ *
+ * @throws {Error} When the record does not contain exactly 2 bytes.
+ * @throws {Error} When the Segmented Address is not a multiple of 0x1000.
+ *
+ * @param iHexRecord Intel hex record line without line terminator.
+ */
+function convertExtSegToLinAddressRecord(iHexRecord: string): string {
+  const segmentAddress = getRecordData(iHexRecord);
+  if (
+    segmentAddress.length !== 2 ||
+    segmentAddress[0] & 0xf || // Only process multiples of 0x1000
+    segmentAddress[1] !== 0
+  ) {
+    throw new Error(`Invalid Extended Segment Address record ${iHexRecord}`);
+  }
+  const startAddress = segmentAddress[0] << 12;
+  return extLinAddressRecord(startAddress);
+}
+
 /**
  * Separates an Intel Hex file (string) into an array of Record strings.
  *
@@ -386,8 +408,8 @@ function iHexToRecordStrs(iHexStr: string): string[] {
  * This is useful to identify the expected max size of the data records for an
  * Intel Hex, and then be able to generate new custom records of the same size.
  *
- * @param iHexRecords Array of Intel Hex Records
- * @returns Number of data bytes th
+ * @param iHexRecords Array of Intel Hex Records.
+ * @returns Number of data bytes in a full record.
  */
 function findDataFieldLength(iHexRecords: string[]): number {
   let maxDataBytes = 16;
@@ -423,6 +445,7 @@ export {
   blockEndRecord,
   paddedDataRecord,
   convertRecordTo,
+  convertExtSegToLinAddressRecord,
   iHexToRecordStrs,
   findDataFieldLength,
 };