# Bytecode interception infrastructure: Instrumentation and bytecode upgrades


## Abstract

This README describes the current state of bytecode interception infrastructure, used for configuration cache instrumentation and bytecode upgrades for property migration.


## Naming

The naming is hard.
That is the case also for this infrastructure.
In next section we will use next terms:

	End   uint64   // virtual address of last byte in sym (Start+size-1)
}

// A UI manages user interactions.
type UI interface {
	// ReadLine returns a line of text (a command) read from the user.
	// prompt is printed before reading the command.
	ReadLine(prompt string) (string, error)

	// Print shows a message to the user.
	// It formats the text as fmt.Print would and adds a final \n if not already present.

            JavaLanguageVersion javaVersion = JavaLanguageVersion.of(decoder.readSmallInt());
            File registryDir = new File(decoder.readString());
            Long pid = decoder.readBoolean() ? decoder.readLong() : null;
            Integer idle = decoder.readBoolean() ? decoder.readInt() : null;
            int daemonOptCount = decoder.readInt();
            List<String> daemonOpts = new ArrayList<String>(daemonOptCount);

	End   uint64   // virtual address of last byte in sym (Start+size-1)
}

// A UI manages user interactions.
type UI interface {
	// ReadLine returns a line of text (a command) read from the user.
	// prompt is printed before reading the command.
	ReadLine(prompt string) (string, error)

	// Print shows a message to the user.
	// It formats the text as fmt.Print would and adds a final \n if not already present.

        logDeprecation();
        BufferedReader reader = null;
        FileReader fileReader = null;
        try {
            fileReader = new FileReader(file);
            reader = new BufferedReader(fileReader);

            org.gradle.util.internal.LimitedDescription description = new org.gradle.util.internal.LimitedDescription(maxLines);
            String line = reader.readLine();
            while (line != null) {

	})
	if e != nil {
		return &LinkError{"symlink", oldname, newname, e}
	}
	return nil
}

func readlink(name string) (string, error) {
	for len := 128; ; len *= 2 {
		b := make([]byte, len)
		var (
			n int
			e error
		)
		for {
			n, e = fixCount(syscall.Readlink(name, b))
			if e != syscall.EINTR {
				break
			}
		}
		// buffer too small

            executor.execute(() -> {
                while (true) {
                    String input;
                    try {
                        input = reader.readLine();
                    } catch (IOException e) {
                        throw UncheckedException.throwAsUncheckedException(e);
                    }
                    if (input == null) {

                    String name;
                    if (args.length < 1) {
                        try (BufferedReader in = new BufferedReader(new InputStreamReader(System.in))) {
                            name = in.readLine();
                            if (name != null) {
                                name = name.trim();
                            }
                        }
                    } else {

        mainJavaFile.text = mainClass("""
            try {
                String location = System.getProperty("input.file");
                BufferedReader reader = new BufferedReader(new FileReader(location));
                String input = reader.readLine();
                reader.close();
                FileWriter out = new FileWriter(args[args.length - 1], false);
                out.write(input);
                out.close();

		return err
	}

	// (2)
	dataDirPath := filepath.Join(w.targetDir, dataDirName)
	oldTsDir, err := os.Readlink(dataDirPath)
	if err != nil {
		if !os.IsNotExist(err) {
			klog.Errorf("%s: error reading link for data directory: %v", w.logContext, err)
			return err
		}
		// although Readlink() returns "" on err, don't be fragile by relying on it (since it's not specified in docs)