[Java] Add a task to verify the generated Ir codecs are in sync with the current version of the generator. If the generator changed then the build will fail unless codecs are updated first.

Author: vyazelenko

build.gradle

@@ -1,3 +1,8 @@
+import java.nio.file.Files
+import java.nio.file.Paths
+import java.nio.file.StandardOpenOption
+import java.security.MessageDigest
+
 /*
  * Copyright 2013-2021 Real Logic Limited.
  *
@@ -20,7 +25,7 @@ plugins {
     id "com.github.ben-manes.versions" version "0.39.0"
 }
 
-defaultTasks 'clean', 'build'
+defaultTasks 'clean', 'verifyJavaIrCodecsInSync', 'build'
 
 static def getBuildJavaVersion() {
     def buildJavaVersion = System.getenv('BUILD_JAVA_VERSION') ?: JavaVersion.current().getMajorVersion()
@@ -660,7 +665,7 @@ task generateCSharpCodecs {
         'generateCSharpCodecsWithXIncludes'
 }
 
-task generateJavaIrCodecs(type: JavaExec) {
+task generateJavaIrCodecs(type: JavaExec, dependsOn: 'computeOriginalIrHash') {
     mainClass = 'uk.co.real_logic.sbe.SbeTool'
     classpath = project(':sbe-all').sourceSets.main.runtimeClasspath
     systemProperties(
@@ -708,6 +713,32 @@ task testReport(type: TestReport) {
     reportOn subprojects*.test
 }
 
+final codecsDir = Paths.get('sbe-tool/src/main/java/uk/co/real_logic/sbe/ir/generated').toFile()
+final outputDir = Paths.get('sbe-tool/build')
+final originalHashFile = outputDir.resolve('original.sha256').toFile()
+final newHashFile = outputDir.resolve('new.sha256').toFile()
+
+task computeOriginalIrHash(type: ChecksumTask) {
+    inputDirectory = codecsDir
+    outputFile = originalHashFile
+}
+
+task computeUpdatedIrHash(type: ChecksumTask, dependsOn: 'generateJavaIrCodecs') {
+    inputDirectory = codecsDir
+    outputFile = newHashFile
+}
+
+task verifyJavaIrCodecsInSync(dependsOn: 'computeUpdatedIrHash') {
+    doLast {
+        final byte[] oldHash = Files.readAllBytes(originalHashFile.toPath())
+        final byte[] newHash = Files.readAllBytes(newHashFile.toPath())
+        if (!Arrays.equals(oldHash, newHash))
+        {
+            throw new GradleException("Java Ir codecs are out of sync!")
+        }
+    }
+}
+
 def isNonStable = { String version ->
     def stableKeyword = ['RELEASE', 'FINAL', 'GA'].any { it -> version.toUpperCase().contains(it) }
     def regex = /^[0-9,.v-]+(-r)?$/
@@ -725,3 +756,34 @@ wrapper {
     gradleVersion = '7.1.1'
     distributionType = 'ALL'
 }
+
+class ChecksumTask extends DefaultTask
+{
+    private static final MessageDigest SHA_256 = MessageDigest.getInstance("SHA-256");
+
+    @InputDirectory
+    File inputDirectory
+
+    @OutputFile
+    File outputFile
+
+    @TaskAction
+    def checksum() {
+        SHA_256.reset()
+
+        final File[] files = inputDirectory.listFiles();
+        for (final File f : files)
+        {
+            SHA_256.update(Files.readAllBytes(f.toPath()))
+        }
+
+        final byte[] hash = SHA_256.digest()
+
+        Files.write(
+            outputFile.toPath(),
+            hash,
+            StandardOpenOption.CREATE,
+            StandardOpenOption.WRITE,
+            StandardOpenOption.TRUNCATE_EXISTING)
+    }
+}