CLASSTemplate.bt

//-------------------------------------------------------------------------
//--- 010 Editor v2.1 Binary Template
//
//    File: CLASSTemplate.bt
//  Author: Kevin O. Grover <kevin@kevingrover.net>
// Purpose: A template for parsing Java Class (JVM) Files
// Version: 1.1   2014-08-13
// History:
// 2007-02-26  kog  Original Version
// 2014-08-13  kog  Updated for Java 7/8 Version number (and future)
//
// This template was written to the "The Java Virtual Machine
// Specification", Second Edition, by Tim Lindholm, Frank Yellin.
// It was later updated to include the provisio in that spec (and future
// specs).
//
// The details used to write this Template came mainly from Chapter 4:
// "The <code>class</code> File Format".
//
// You can get the document from the Oracle Java Pages or Wikipedia:
//   http://docs.oracle.com/javase/specs/
//   http://docs.oracle.com/javase/specs/jvms/se7/jvms7.pdf
//   http://docs.oracle.com/javase/specs/jvms/se8/jvms8.pdf
//   http://en.wikipedia.org/wiki/Class_file
//-------------------------------------------------------------------------

BigEndian();

// Types used in the JVM Spec.
// (To make this code as close to the text in the spec as possible.)
typedef uint32 u4;
typedef uint16 u2;
typedef ubyte  u1;

typedef enum <u2> eACCESS_FLAGS {
    ACC_PUBLIC =    0x0001,     // Declared public; may be accessed from outside its package.
    ACC_PRIVATE =   0x0002,     // Declared private; usable only within the defining class.
    ACC_PROTECTED = 0x0004,     // Declared protected; may be accessed within subclasses.
    ACC_STATIC =    0x0008,     // Declared static.
    ACC_FINAL =     0x0010,     // Declared final; no subclasses allowed.
    ACC_SUPER =     0x0020,     // Treat superclass methods specially when invoked by the invokespecial instruction.
    ACC_VOLATILE =  0x0040,     // Declared volatile; cannot be cached.
    ACC_TRANSIENT = 0x0080,     // Declared transient; not written or read by a persistent object manager.
    ACC_NATIVE =    0x0100,     // Declared native; implemented in a language other than Java.
    ACC_INTERFACE = 0x0200,     // Is an interface, not a class.
    ACC_ABSTRACT =  0x0400,     // Declared abstract; may not be instantiated.
    ACC_STRICT =    0x0800  // Declared strictfp; floating-point mode is FP-strict
} AF <read=read_AF>;

string read_AF (local AF &af) {
    local string s = "";
    local int commaNeeded = 0;
    local AF i = 1;

    SPrintf (s, "%d: ", af);

    // Iterate over all possible values the flags
    // if the given bit is set, add it's text representation to the
    // return string.
    // NOTE: There's probably a better way to do this. (More portable?)
    while (i < ACC_STRICT) {
        if (af && i) {
            if (commaNeeded) {
                s += ", ";
            }
            s += EnumToString(i);
            commaNeeded = 1;
        }
        i = i << 1;
    }
    return s;
}

// Constants for cp_info.tag ...
typedef enum <u1> eCP_CONST {
    CONSTANT_Utf8 =     1,
    CONSTANT_Integer =  3,
    CONSTANT_Float =    4,
    CONSTANT_Long = 5,
    CONSTANT_Double =   6,
    CONSTANT_Class =    7,
    CONSTANT_String =   8,
    CONSTANT_Fieldref = 9,
    CONSTANT_Methodref =    10,
    CONSTANT_InterfaceMethodref =   11,
    CONSTANT_NameAndType =  12,
} CP_CONST;

// Constant Pool Table Structure
// NOTE: These are NOT constant sized items.  Although referenced
//       like an array in the main structure, you can not use position
//       to directly infer a byte offset because you do not know the
//       sizes of the items preceeding it.
typedef struct {
    CP_CONST  tag;
    switch(tag)
    {
    case CONSTANT_Class:
        u2 name_index;
        break;
    case CONSTANT_Methodref:
    case CONSTANT_Fieldref:
    case CONSTANT_InterfaceMethodref:
        u2 class_index;
        u2 name_and_type_index;
        break;
    case CONSTANT_Utf8:
        u2 length;
        char bytes[length];
        break;
    case CONSTANT_Integer:
    case CONSTANT_Float:
        u4 bytes;
        break;
    case CONSTANT_Long:
    case CONSTANT_Double:
        u4 high_bytes;
        u4 low_bytes;
        break;
    case CONSTANT_String:
        u2 string_index;
        break;
    case CONSTANT_NameAndType:
        u2 name_index;
        u2 descriptor_index;
        break;
    default:
        local string s;
        SPrintf(s, "Unknown 'constant_pool' tag: %d", tag);
        Warning(s);
        return -3;
    }
} cp_info <read=read_cp_info, optimize=false>;

/**
 * Reader for 'cp_info'
 * @param  cp_info   Constant Pool info structure
 */
string read_cp_info (local cp_info &i)
{
    local string s = "";
    s = EnumToString(i.tag);
    if (i.tag == CONSTANT_Utf8) {
        s += ": " + i.bytes;
    }
    return s;
}

typedef struct {
    u2 attribute_name_index;
    u4 attribute_length;
    u1 info[attribute_length];
} attribute_info <optimize=false>;

typedef struct {
    AF access_flags;
    u2 name_index;
    u2 descriptor_index;
    u2 attributes_count;
    attribute_info attributes[attributes_count];
} field_info <optimize=false>;

typedef struct {
    AF access_flags;
    u2 name_index;
    u2 descriptor_index;
    u2 attributes_count;
    attribute_info attributes[attributes_count];
} method_info <optimize=false>;

// MAIN Structure

typedef struct {
    u4 magic <format=hex>;
    if (magic != 0xCAFEBABE) {         // Check that 'magic' is correct
        Warning("Incorrect Magic Number.  This is not a JVM Class.  Template Terminated.");
        return -1;
    }
    u2 minor_version;
    u2 major_version;
    u2 constant_pool_count;
    cp_info constant_pool[constant_pool_count-1];
    AF access_flags;
    u2 this_class;              // Reference into constant_pool table
    if (this_class < 1 || this_class > constant_pool_count-1) {
        local string s;
        SPrintf(s,"Bad 'this_class' reference (%d).  It should be in the range [1..%d]", this_class, constant_pool_count-1);
        Warning(s);
        return -2;
    }
    u2 super_class;             // Reference into constant_pool table
    if (super_class < 1 || super_class > constant_pool_count-1) {
        local string s;
        SPrintf(s,"Bad 'super_class' reference (%d).  It should be in the range [1..%d]", super_class, constant_pool_count-1);
        Warning(s);
        return -2;
    }
    u2 interfaces_count;
    u2 interfaces[interfaces_count];
    u2 fields_count;
    field_info fields[fields_count];
    u2 methods_count;
    method_info methods[methods_count];
    u2 attributes_count;
    attribute_info attributes[attributes_count];
} JVMClass <read=read_JVMClass, optimize=false>;

/**
 * Reader for 'JVMClass'
 * Returns  the JVM Version: major.minor and the Java version (if it can
 *          calculate it from the JVM Version.
 * @param   j JVMClass    The JVM Class Structure
 * @return  string        The version information
 */
string read_JVMClass (local JVMClass &j)
{
    // JVM Version (as stored in the class file)
    local string s;
    SPrintf (s, "JVM class v%d.%d", j.major_version, j.minor_version);

    // Java Runtime Version.  From the JVM Spec for class files
    local int major = 1;
    local int minor = 0;

    if (j.major_version == 45) {
        if (j.minor_version >= 3) minor = 1;
    } else {
        if (j.major_version >= 46) {
            minor = j.major_version - 44;
        } else {
            // Unknown: it's either newer or older than expected
            major = 0;
            minor = 0;
            Warning("Unexpected JVM major version number.");
        }
    }

    if (major || minor) {
        local string jre_v;
        SPrintf(jre_v, " (Java %d.%d)", major, minor);
        s += jre_v;
    } else {
        s += " (Unknown Java Version)";
    }

    return s;
}

// *****************************************
//  MAIN - Allocate data here...
// *****************************************

struct JVMClass jc;