Module reader 

Class File Reader

The reader module provides high-performance parsing of JVM .class binary files into the structured JvmProgram model.

Features

• On-demand Reading: Supports partial reading of class components for better performance when only specific information (like class metadata) is needed.
• Robust Error Handling: Provides detailed diagnostics and error reporting for malformed or unsupported class files.
• Version Support: Compatible with all major JVM class file versions (Java 1.1 to latest).
• Constant Pool Resolution: Automatically resolves constant pool indices into human-readable strings and symbolic references.

Usage Example

use jvm_assembler::formats::class::ClassReadConfig;
use jvm_assembler::formats::class::reader::ClassReader;
use std::fs::File;
use std::io::BufReader;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    // 1. Open the .class file
    let file = File::open("MyClass.class")?;
    let reader = BufReader::new(file);

    // 2. Configure the reader
    let config = ClassReadConfig::default();
    let class_reader = ClassReader::new(reader, &config);

    // 3. Parse the class into a JvmProgram
    let diagnostics = class_reader.read();
    
    if let Ok(program) = diagnostics.result {
        println!("Successfully parsed class: {}", program.name);
        for method in &program.methods {
            println!("Method: {} {}", method.name, method.descriptor);
        }
    } else {
        eprintln!("Failed to parse class file");
        for diag in diagnostics.diagnostics {
            eprintln!("Error: {:?}", diag);
        }
    }

    Ok(())
}

Internal Workflow

1. Header Parsing: Validates the 0xCAFEBABE magic number and reads version info.
2. Constant Pool Loading: Parses all entries in the constant pool.
3. Metadata Extraction: Reads class access flags, name, superclass, and interfaces.
4. Member Parsing: Iteratively parses fields and methods, including their attributes (like Code and Signature).
5. Model Construction: Maps the low-level binary structures to the high-level JvmProgram IR.

Structs

ClassReader

JVM Class 文件读取器