🚀 Add xdelta3 support

src/ssn/getPatch.ts

@@ -11,6 +11,7 @@ import readSsnFile from './reader/readSsnFile';
 import getFileFromDisks from './streams/getFileFromDisks';
 import verifyPatch from './verify/verifyPatch';
 import verifyProductName from './verify/verifyProductName';
+import performDiffing from './xdelta3/performDiffing';
 
 interface IGetPatchArgs {
   /** The product that should be patched. */
@@ -103,9 +104,31 @@ export default async function getPatch({ product, from, to, sourceDirectory, tar
       const fileStream = await getFileFromDisks(diskFilenames, { diskStart: file.diskNumberStart, offset: file.offset, length: file.compressedSize });
       const fileContents = await extractFileAsStream(file, fileStream);
 
-      //TODO: need to apply xdelta3 diffing, then write to disk
-      //if source === target, need to create .temp file, and when it's done, delete source file and rename .temp to actual name
-      console.warn(`Could not extract "${file.name}"; xdelta3 diffing is not yet implemented.`);
+      //need to apply xdelta3 diffing, then write to disk
+      const sourceFile = path.join(sourceDir, file.name);
+      const outputName = path.join(targetDir, file.name);
+      const outputNameTemp = `${outputName}.tmp`;
+      await performDiffing(sourceFile, fileContents, outputNameTemp);
+
+      //clean up: delete source file if necessary, and remove .tmp file extension
+      if (sourceDir === targetDir) {
+        fs.unlink(sourceFile, (deleteError) => {
+          if (deleteError) {
+            throw new Error(`Could not delete old source file "${sourceFile}": ${deleteError.name}`);
+          }
+          fs.rename(outputNameTemp, outputName, (renameError) => {
+            if (renameError) {
+              throw new Error(`Could not rename output file "${outputNameTemp}": ${renameError.name}`);
+            }
+          });
+        });
+      } else {
+        fs.rename(outputNameTemp, outputName, (renameError) => {
+          if (renameError) {
+            throw new Error(`Could not rename output file "${outputNameTemp}": ${renameError.name}`);
+          }
+        });
+      }
     } catch (error) {
       console.error(`Could not extract file "${file.name}"`, error);
     }

src/ssn/xdelta3/performDiffing.ts

@@ -0,0 +1,26 @@
+import * as childProcess from 'child_process';
+import * as fs from 'fs';
+import * as stream from 'stream';
+
+export default function performDiffing(sourceFile: string, diffStream: stream.Readable, targetFile: string): Promise<void> {
+  return new Promise((resolve, reject) => {
+    //const sourceStream = fs.createReadStream(sourceFile);
+    const targetStream = fs.createWriteStream(targetFile);
+
+    //spawn xdelta3 process, set up listeners
+    const process = childProcess.spawn('xdelta3', ['-d', '-s', sourceFile]);
+    diffStream.pipe(process.stdin);
+    process.stdout.pipe(targetStream);
+    process.stderr.on('data', (chunk) => {
+      reject(`Error during xdelta3: ${chunk}`);
+    });
+
+    process.on('exit', (code, signal) => {
+      if (code === 0) {
+        resolve();
+      } else {
+        reject(`xdelta3 exited with code "${code}" due to signal "${signal}".`);
+      }
+    });
+  });
+}