methgen.java

java 到c的转换程序的原代码.对喜欢C程序而不懂JAVA程序的人很有帮助

//  MethGen.java -- generation of C code for Java methods

package toba.translator;

import toba.classfile.*;
import java.io.*;
import java.util.*;



class MethGen extends Opcode {



static boolean nullJump;	// flag, set by some InsGens



//  needSwitch(m) -- does method m generate a switch() statement?

static final boolean needSwitch(Method m) {
    return m.handlers.length > 0 || (m.oflags & JSRI) != 0;
}



//  minfo(d, method) -- generate info, even for native method.

static void minfo(PrintWriter d, Method m)
{
    Field f = m.fl;

    // generate comment giving hashed and unhashed names
    d.println();
    d.println("/*M " + f.cname + ": " +
	m.cl.name + "." + f.name + f.signature + " */");

    // generate list of thrown exceptions
    d.println();
    /* We'd like this thing to be static, since nobody else should care
     * about it, but the Irix C compiler won't let us get away with that
     * because we had to refer to the thing earlier in the file and it
     * made us declare it extern beforehand.  See CFile.java. */
    d.print("Class xt_" + f.cname + "[] = { ");
    for (int i = 0; i < m.exthrown.length; i++) {
	if (i % 3 == 2) 
	    d.print("\n    ");
	d.print("&cl_" + Names.hashclass(m.exthrown[i].name) + ".C, ");
	}
    d.println("0 };");
}



//  mgen(d, method) -- generate code for one method.

static void mgen(PrintWriter d, Method m)
{
    ClassData cls = m.cl;
    Field f = m.fl;
    int n;

    // dump the code as C comments, if requested
    if (Trans.debugging(Trans.dbgCode))
	Instr.dump(d, m.instrs);

    // generate the function header
    d.println();
    d.print(Repr.rettype(m.fl.signature) + " ");
    if ((f.access & ClassData.ACC_SYNCHRONIZED) != 0)
	d.print("sy_");
    d.println(f.cname + "(" + parmdecls(m) + ")");
    d.println("{");

    // generate the exception table, if any
    if (m.handlers.length > 0) {
	d.println("static struct handler htable[] = {");
	for (int i = 0; i < m.handlers.length; i++) {
	    Handler h = m.handlers[i];
	    if (h.type == null)
		d.print("    0, ");
	    else
		d.print("    &cl_" +
		    Names.hashclass(h.type.name) +
		    ".C, ");
	    d.println(h.start + ", " + h.end + ", " +
		m.instrs[m.pcmap[h.jump]].label + ",");
	}
	d.println("};");
    }

    // declare variables for exception handling and JSR
    if (m.handlers.length > 0) {
	d.println("struct mythread *tdata;");
	d.println("jmp_buf newbuf;");
	d.println("void *oldbuf;");
	d.println("volatile int pc;");
    }
    if (needSwitch(m))
	d.println("int tgt;");
    if (needSwitch(m) && m.rstack.length() > 0)
	d.println(Repr.rettype(m.fl.signature) + " rv;");

    // declare stack and local variables
    if ((m.oflags & Opcode.INST) != 0)		// need temps for ckinstance()?
	d.println("Class c0, c1;");
    for (int i = 0; i < Method.JVM_TYPES.length(); i++) {
	char c = Method.JVM_TYPES.charAt(i);
	dclstack(d, m, c);
	dclvars(d, m, c, m.handlers.length > 0);
    }

    /* Insert macro for generic function prologue. */
    d.println("PROLOGUE;");

    // generate initialization of local variables (from parameter list)
    d.println();
    lvinits(d, m);				

    // initialize class, if static function, and if class has initializer
    if ((f.access & ClassData.ACC_STATIC) != 0
	    && !f.name.equals("<clinit>")
	    && cls.getmethod("<clinit>",false) != null) {
	d.println();
	d.println("\tif (cl_" + cls.cname + ".C.needinit)");
	d.println("\t\tinitclass(&cl_" + cls.cname + ".C);");
    }

    // initialize exception handling
    if (m.handlers.length > 0) {
	d.println();
	d.println("\ttdata = mythread();");
	d.println("\toldbuf = tdata->jmpbuf;");
	d.println("\ttgt = 0;");
	d.println("\tif (setjmp(newbuf)) {");
	d.println("\t\tsthread_got_exception();");
	d.println("\t\ta1 = tdata->exception;");
	d.println("\t\tif ((tgt = findhandler(htable, " + m.handlers.length +
	    ", a1, pc)) < 0)");
	d.println("\t\t\tlongjmp(oldbuf, 1);");
	d.println("\t}");
	d.println("\ttdata->jmpbuf = newbuf;");
    } else if (needSwitch(m)) {
	d.println();
	d.println("\ttgt = 0;");
    }

    // generate switch top
    if (needSwitch(m)) {
	d.println();
	d.println("TOP: switch(tgt) {");
    }

    // generate code for individual instructions
    d.println();
    nullJump = false;			// assume we won't need a null jump

    for (int i = 0; i < m.instrs.length; i++) {
	Instr ins = m.instrs[i];
	if (ins.isTarget) {
	    d.print("L" + ins.label + ":");	// generate label
	    if (needSwitch(m))			// and also case label if needed
		d.println("  case " + ins.label + ":");
	}
	if (ins.isBoundary && m.handlers.length > 0)
	    d.println("\tpc = " + ins.pc + ";");
	if (Trans.debugging(Trans.dbgInstrs))
	    d.println("\t\t\t/* " + ins.opcode.name + " */");
	InsGen.igen(d, m, ins);			// generate code for instruction
	if ((ins.opcode.flags & Opcode.NFT) != 0)
	    d.println();		// if no fallthrough, add visual break
    }

    // terminate switch
    if (needSwitch(m)) {
	d.println("}");
	d.println("RETURN:");
	d.println("\ttdata->jmpbuf = oldbuf;");
	if (m.rstack.length() > 0)
	    d.println("\treturn rv;");
	else
	    d.println("\treturn;");
    }

    // null pointer exceptions need a jump target
    if (nullJump) {
	d.println("NULLX:");
	d.println("\tthrowNullPointerException(0);");
    }

    // To shut up the Irix C compiler, let's make it clear that we don't
    // actually ever get here. */
    d.println("\t/*NOTREACHED*/");
    d.println("}");
}



//  parmdecls(m) -- return string of C parameter declarations for Java method m.

private static String parmdecls(Method m)
{
    String s = m.fl.signature;			// signature being scanned
    int i = 1;					// current position (skip "(")
    String t;

    StringBuffer b = new StringBuffer();	// parm list being built
    int lv = 0;					// local variable count

    if ((m.fl.access & ClassData.ACC_STATIC) == 0) {  // instance function?
	b.append("Object p0, ");		// "self" parameter
    }

loop:
    for (int n = 1; ; n++) {
	char c = s.charAt(i);
	switch (c) {

	    case 'L':				// object
	    default:				// not used, keeps javac happy
		t = "Object";
		i = s.indexOf(';', i);
		break;

	    case '[':				// array
		t = "Object";
		while (s.charAt(i) == '[')
		    i++;
		if (s.charAt(i) == 'L')
		    i = s.indexOf(';', i);
		break;

	    // primitive types
	    case 'B':  t = "Byte";     break;
	    case 'C':  t = "Char";     break;
	    case 'D':  t = "Double";   break;
	    case 'F':  t = "Float";    break;
	    case 'I':  t = "Int";      break;
	    case 'J':  t = "Long";     break;
	    case 'S':  t = "Short";    break;
	    case 'Z':  t = "Boolean";  break;

	    case ')':  break loop;		// end of parameters
	}
	b.append(t).append(" p").append(n).append(", ");
	i++;
    }

    if (b.length() == 0)
	return "void";				// no parameters
    else {
	b.setLength(b.length() - 2);		// trim final ", " from string
	return b.toString();			// return param declarations
    }
}



//  dclstack(d, m, jtype) -- declare stack variables for a JVM type

static private void dclstack(PrintWriter d, Method m, char jtype)
{
    if (!m.stktypes.get((int)jtype))
	return;

    d.print(Repr.ctype(jtype) + " ");
    for (int i = 0; i < m.max_stack; i++) {
	if (i > 0 && i % Repr.DECLS_PER_LINE == 0)
	    d.print("\n    ");
	d.print(jtype + Integer.toString(i) + ", ");
    }
    d.println(jtype + Integer.toString(m.max_stack) + ";");
}



//  dclvars(d, m, jtype, volatile) -- declare local variables marked in bitset

static private void dclvars(PrintWriter d, Method m, char jtype, boolean vol)
{
    int max = m.maxvar[(int)jtype];
    if (max < 0)
	return;

    BitSet bs = m.varused[(int)jtype];
    String s;
    int n = 0;

    for (int i = 0; i <= max; i++) {
	if (bs.get(i)) {
	    s = " " + jtype + "v" + i;
	    if (n % Repr.DECLS_PER_LINE == 0) {
		if (n == 0) {
		    if (vol)
			d.print("volatile ");
    		    d.print(Repr.ctype(jtype) + s);
		} else
	    	    d.print(",\n   " + s);
	    } else
		d.print("," + s);
	    n++;
	}
    }
    d.println(";");
}



//  lvinits(d, m) -- generate local variable initializations for method m

static private void lvinits(PrintWriter d, Method m)
{
    String s = m.astack;				// entry "stack"
    int pnum = 0;					// parameter number
    int vnum = 0;					// variable number

    if ((m.fl.access & ClassData.ACC_STATIC) != 0)	// if static function
    	pnum++;						//    no "this" param

    for (int i = 0; i < s.length(); i++) {		// for each entry val
    	char c = s.charAt(i);
	if (c == 'x') {					// if double-wide 
	    c = s.charAt(++i);
	    d.println("\t" + c + "v" + vnum + " = p" + pnum++ + ";");
	    vnum += 2;
	} else {
	    d.println("\t" + c + "v" + vnum++ + " = p" + pnum++ + ";");
	}
    }
}


//  syncwrap(d, m) -- generate wrapper function for synchronized method

static void syncwrap(PrintWriter d, Method m)
{
    int i, j;
    String p;

    // generate header
    p = parmdecls(m);
    d.println("\n\n");
    d.println("/* wrapper for synchronized method */");
    d.println(Repr.rettype(m.fl.signature) + " " + m.fl.cname + "(" + p + ")");
    d.println("{");

    // declare underlying function, if native
    if ((m.fl.access & ClassData.ACC_NATIVE) != 0)
	d.println("\t" + Repr.rettype(m.fl.signature) +
	    " sy_" + m.fl.cname + "();");

    // declare return value, if not void method
    if (m.rstack.length() > 0)
	d.println("\t" + Repr.rettype(m.fl.signature) + " rv;");

    // declare data pointer, sigsetjmp buffer, and variable
    d.println("\tstruct mythread *tdata;");
    d.println("\tjmp_buf newbuf;");
    d.println("\tvoid *oldbuf;");
    d.println("\tvolatile int monitor_held = 0;");
    d.println("\t");

    // set exception catcher
    d.println("\ttdata = mythread();");
    d.println("\toldbuf = tdata->jmpbuf;");
    d.println("\tif (setjmp(newbuf)) {");
    d.println("\t\tsthread_got_exception();");

    // on exception: exit monitor, if held, and rethrow exception
    d.println("\t\tif (monitor_held)");
    if ((m.fl.access & ClassData.ACC_STATIC) != 0) {
        d.println("\t\t\texitclass(&cl_" +
	    m.cl.cname + ".C, tdata, 0, &monitor_held);");
    } else {
        d.println("\t\t\tmonitorexit(p0, tdata, 0, &monitor_held);");
    }
    d.println("\t\ttdata->jmpbuf = oldbuf;");
    d.println("\t\tathrow(tdata->exception);");
    d.println("\t}");

    // point exception handling to this jump buffer
    d.println("\ttdata->jmpbuf = newbuf;");

    // enter the monitor now that the exception handler is prepared
    if ((m.fl.access & ClassData.ACC_STATIC) != 0) {
        // for static functions, the class is locked
        d.println("\tenterclass(&cl_" + 
	    m.cl.cname + ".C, tdata, 1, &monitor_held);");
    } else {
        // for instance functions, the instance (p0) is locked.
        d.println("\tmonitorenter(p0, tdata, 1, &monitor_held);");
    }

    // call underlying function
    if (m.rstack.length() > 0)
	d.print("\trv = ");		// assign return value, if any
    else
	d.print("\t");
    d.print("sy_" + m.fl.cname + "(");	// underlying function name
    i = -1;
    while ((i = p.indexOf('p', i + 1)) >= 0) {
	j = p.indexOf(',', i + 1) + 1;	// parameters are pnnn through comma
	if (j <= 0)
	    j = p.length();
	d.print(p.substring(i, j));
    }
    d.println(");");

    // exit monitor
    if ((m.fl.access & ClassData.ACC_STATIC) != 0) {
        d.println("\texitclass(&cl_" 
	    + m.cl.cname + ".C, tdata, 0, &monitor_held);");
    } else {
        d.println("\tmonitorexit(p0, tdata, 0, &monitor_held);");
    }

    // restore old exception handler and return
    d.println("\ttdata->jmpbuf= oldbuf;");
    if (m.rstack.length() > 0)
	d.println("\treturn rv;");
    d.println("}");
}



} // class MethGen