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Nov 96 Challenge
Volume Number:12
Issue Number:11
Column Tag:Programmer’s Challenge

Programmer’s Challenge

By Bob Boonstra

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

Router Rules

This month’s Challenge is based on a suggestion by Peter Lewis and is motivated by a real-world problem. A certain university has a B-class IP subnet, let’s call it 199.232.*.* (with apologies to the real-world owner of that subnet). The subnet is broken down into 256 networks for the various faculties and departments, each one having 256 IP numbers. So, for example, the computer club might have 199.232.101.*. Our hypothetical university is charged for communications based on volume, so some of these networks are allowed to talk to the outside world, and others are not. Outside access is controlled by programming a router with a sequence of rules, each of which allows or denies access to some subset of IP numbers. A rule consists of a (mask, value, allow) triplet. For example, say the networks (in hex) 01, 03, 41, 43 are allowed out, and all the rest are barred. The rules could be simply

 FF, 01, allow
 FF, 03, allow
 FF, 41, allow
 FF, 43, allow
 00, 00, deny

But this could be simplified to

 BD, 01, allow
 00, 00, deny

Your objective for this Challenge is to quickly generate a small sequence of rules that allows outside network access to only a specified set of networks. The prototype for the code you should write is

enum {kDeny=0, kAllow=1};

typedef struct Rule {
 long mask;
 long value;
 long allow;/* 0 == deny, 1== allow */
} Rule;

long RouterRules(
 long allowedValues[],
 long numAllowedValues,
 long numBits,
 Rule rulesArray[],
 long maxRules
);

The array allowedValues is the set of numAllowedValues networks that are to be given outside network access. All other networks should be denied access. Instead of being limited to 8 bits as in the example above, network values have numBits bits. Your code should generate a sequence of rules that provides access to these networks, and no others. The rule sequence should be as short as possible and stored in rulesArray, which is allocated by the caller and is of size maxRules. Your code should return the number of rules generated, or return -1 if it cannot find a solution no longer than maxRules.

Rules will be triggered by the router in the order provided by your solution, and the first rule to fire for a given network will apply. At least one rule must fire for any possible network value. For example, if numBits==3, and we want to allow access to networks 0, 2, 3, 6, and 7, you could use the following rules:

 3, 1, deny
 6, 4, deny
 7, 7, allow

To encourage code that generates both fast and short solutions, the ranking will be based on minimizing the following function of execution time on my 8500/150 and the number of rules generated:

score = (number of rules generated) + (execution time in seconds) / 2

This will be a native PowerPC Challenge, using the latest CodeWarrior environment. Solutions may be coded in C, C++, or Pascal.

Two Months Ago Winner

Congratulations to Xan Gregg (Durham, N.C.), for submitting the fastest entry to the ByteCode Interpreter Programmer’s Challenge, narrowly beating out the second-place entry by Ernst Munter. The Challenge was to write an interpreter for a subset of the byte code language implemented by the Java Virtual Machine. The Challenge rules pointed to the Java Virtual Machine Specification for a description of the opcodes, with some exclusions about the opcodes and features that were to be implemented, and with the significant simplifying assumption that the Virtual Machine need only deal with a single class file. Of the five solutions submitted, three worked correctly for all test cases, one worked for all but one test case, and the fifth was acknowledged by the author to be incomplete.

The rules for September permitted the use of assembly language, and Xan was the only contestant to submit a solution that took advantage of this. After parsing the header to identify the constants, fields, and methods contained in the class file, the solution dispatches and executes each opcode. As described by the comments in the code, the main execution loop contains a table with 32 bytes of PowerPC instructions implementing each opcode. Opcodes that require more code than will fit into the table entry overflow to code outside the table. Particular features that you might want to examine in the code include the implementation of the jump table and the pseudo-opcode ExitCode used to trigger a return to the calling routine. Congratulations to Xan on an elegant, efficient, and instructive solution. Several readers commented that they learned quite a bit about Java from implementing a Virtual Machine. Congratulations as well to everyone who participated in this more difficult than usual Challenge!

The table below summarizes the results for each entry, including execution time in milliseconds, code size, and data size. An asterisk indicates a test case that was not successfully completed by a solution. Numbers in parenthesis after a person’s name indicate that person’s cumulative point total for all previous Challenges, not including this one.

Name Lanugage Test1 Test2 Test3 Test4 Time Code Data

Xan Gregg (92) C/Assembly 31088 12923 24607 45190 113808 10064 171

Ernst Munter (214) C++ 18661 14664 28260 52496 114081 6260 879

Turlough O’Connor C++ 23073 15946 30503 57444 126967 14536 5818

Conor MacNeill C++ 44446 * 43298 84020 * 82536 10909

The test code was contained in standard Java applets, which allowed me to use the interpreters supplied with the Symantec and Metrowerks environments to confirm expected results. This also allowed a comparison of the execution time of the mini Virtual Machines submitted as solutions with the execution time of the commercial interpreters. Results for the same four test cases used to score the solutions are presented below for the Applet Viewer provided with Symantec Cafe (version 1.0) and for the Metrowerks Java interpreter provided with CodeWarrior 9. While the comparison is not entirely fair because of the simplifying assumptions used in this Challenge, the table indicates that three of the four solutions were faster than both of these interpreters. Although CodeWarrior 10 has not been finalized as this column is being written, it should be available at publication, and Metrowerks was kind enough to give me a preview of the Java interpreters available in that release. For my limited set of test cases, the CW10 version of Metrowerks Java was approximately 25% faster than the CW9 version. Even more impressive was the Just-In-Time version of the interpreter, which (I assume) first compiles the byte-coded instructions into PowerPC instructions before execution. My tests suggest that Metrowerks Java JIT executes an order of magnitude faster than the CW9 interpreter (not counting the preprocessing compilation time, which my tests did not measure).

ProductTest 1Test 2Test 3Test 4Time
Symantec Cafe 1.0410003400062000134000271000
Metrowerks Java (CW9)24175187143507568077146041
Metrowerks Java18336142532749452285112368
(CW10 preview)
Metrowerks Java JIT548715492560597715573
(CW10 preview)

TOP 20 CONTESTANTS

Here are the Top 20 Contestants for the Programmer’s Challenge. The numbers below include points awarded over the 24 most recent contests, including points earned by this month’s entrants.

Rank Name Points

1. Munter, Ernst 193

2. Gregg, Xan 112

3. Larsson, Gustav 87

4. Lengyel, Eric 40

5. [Name deleted] 40

6. Lewis, Peter 32

7. Boring, Randy 27

8. Beith, Gary 24

9. Kasparian, Raffi 22

10. Vineyard, Jeremy 22

11. Cutts, Kevin 21

12. Picao, Miguel Cruz 21

13. Brown, Jorg 20

14. Gundrum, Eric 20

15. Karsh, Bill 19

16. Stenger, Allen 19

17. Cooper, Greg 17

18. Mallett, Jeff 17

19. Nevard, John 17

20. Nicolle, Ludovic 14

There are three ways to earn points: (1) scoring in the top 5 of any Challenge, (2) being the first person to find a bug in a published winning solution or, (3) being the first person to suggest a Challenge that I use. The points you can win are:

1st place20 points
2nd place10 points
3rd place7 points
4th place4 points
5th place2 points
finding bug2 points
suggesting Challenge2 points

Here is Xan’s winning solution:

JavaMiniVM.c

Copyright 1996, Xan Gregg

 
/* 
The core of the interpreter is written in mostly PowerPC assember, and the parsing of the tables is done in 
C before interpreting begins.  I create tables of relevant data for constants, fields, and methods.  The constants 
data is just the address of the Java constant_pool data for that index.  For fields and methods I allocate 
structs with the useful data and insert a pointer to the struct into the field’s or method’s constant_pool entry.

So, for some up-front overhead and memory usage (16 bytes per field or method), the interpreter has less 
work to do when dealing with a field or method.

String objects are pointers to the constant_pool payload, just as the provided test code expects.

Objects in general are greatly simplified because of the one class limitation.  No type information is stored 
with any object in the heap.

Of the 10M of provided heapSpace, I use 512K for the Java heap, 512K for the Java stacks (data and return), 
and the rest is available for the constant, field, and method tables, which will consume less that 20 * NumConstants 
bytes.

The heap size and stack size can be set by the macros HEAP_K and STACK_K below.  No garbage collection 
is performed on the heap, so if there is lots of object creation, a larger heap may be needed.

The VM has two stacks, a data stack and a return stack. The data stack grows up from the start of the stack 
space, and the return stack grows down from the end of the stack space.  The data stack is used for parameters 
and normal Java stack operations.  The return stack is used method nesting.  Each call makes a three-entry 
stack frame consisting of the return address, frame pointer (start of locals), and tsBase (the method base 
for use by tableswitch and lookupswitch).

Having separate stacks made the parameter passing easier, but now I realize that with some extra work, 
I could have just put the return frame into added local variables.

The Top-Of-Stack is kept in a register.  This requires a little handshaking when the interpreter calls another 
function, which doesn’t have access to the TOS register.

The core of the interpreter is in the assembly routine, StartVM.  Its main loop fetches and dispatches opcodes, 
as expected.  It includes a table with a 32-byte entry for each opcode (up through 209).  An entry consists 
of code to implement the opcode.  Most of them fit in 32-bytes, and any extra space is used to prime the 
dispatch loop.

Opcodes that take more than 7 instructions to implement can spill over to code outside of the table.  Opcodes 
that are particularly complex (like multianewarray) are implemented with C functions.

Limitations:
I try to safely ignore operations involving long, double, and float operands by treating these types as taking 
0 bytes each.  Most instructions become a NOP, and others are very simple (i2d become a POP).  However, 
I have realized one flaw to this system:  The untyped instructions (like DUP) may try to operate on the unsupported 
types.

It’s too late to fix now, but since the challenge will try to avoid unsupported types, it’s unlikely the stack 
manipulation of them will be needed.

Future:
With the PowerPC code done for each opcode, it would not be too tough to make a compiler that would string 
together the PowerPC code for each opcode in each method.
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// Java types
typedef signed char s1;
typedef signed short s2;
typedef signed long s4;
typedef unsigned char u1;
typedef unsigned short u2;
typedef unsigned long u4;

// Set these if necessary
#define HEAP_K 512
#define STACK_K  512

// the CONSTANT_ id’s
enum {C_Utf8 = 1, C_Unicode, C_Integer, C_Float, C_Long,
 C_Double, C_Class, C_String, C_Fieldref,
 C_Methodref, C_InterfaceMethodref, C_NameAndType};

const u2 ACC_STATIC = 0x0008;

// The contents of my tables
typedef u1 *ConstantData;

typedef struct
{
 u2*fieldInfoP;
 long offset;    // in bytes
 long size; // in bytes
 u1*type; // ptr to sig constant
} FieldData;

typedef struct
{
 u2*methodInfoP;
 u2*codeAttrP;
 u1*codeP;
 u4paramCount;   // in bytes
} MethodData;

// prototypes
void JavaMiniVM(void *constant_pool, void *fields,
 void *methods, void *classFile,
 long methodToExecute, void *heapSpace,void *returnStack);

static short IndexConstants(void *constants,
 ConstantData *indexArray);
static short IndexFields(void *fields);
static short IndexMethods(void *methods);
static void CreateAndPush(void);
static void AllocateStaticFields(void);
static void ResolveFields(void);
static void ResolveMethods(void);
static void CountParams(MethodData *methodP);
asm static long StartVM(register MethodData *methodP);
static void PushConstant(long n);
static u1 *TableSwitch(u1 *ip, long tsBase, long n);
static u1 *LookupSwitch(u1 *ip, long tsBase, long key);
static long GetNewArray(long type, long size);
static long GetANewArray(long size);
static void PushMultiANewArray(long classIndex,
 long numDimensions);

// globals
static long NumMethods;
static long NumFields;
static long NumConstants;
static MethodData*Methods;
static FieldData *Fields;
static ConstantData*Constants;
static long   *FP;     // frame pointer
static long   *SP;    // stack pointer
static long   *S0;     // stack base
static long   *RP;    // return stack pointer
static long   *R0;     // return stack base
static long   *HP;    // heap pointer
static long   *H0;     // heap base
static long   TotalStatic;                 // in bytes
static long   TotalNonStatic;         // in bytes
static long LastField;
static long LastMethod;

/* java types
typedef struct
{
0  u2 attribute_name;
2  u4 attribute_length;
6  u1 info[1];
} attribute_info;



typedef struct
{
0  u2 access_flags;
2  u2 name_index;
4  u2 signature_index;
6  u2 attribute_count;
8  attribute_info      attributes[1];
} field_info;

typedef struct
{
0  u2 access_flags;
2  u2 name_index;
4  u2 signature_index;
6  u2 attribute_count;
8  attribute_info      attributes[1];
} method_info;

typedef struct
{
0  u1 tag;
1  u2 length;
3  u1 bytes[1];
} CONSTANT_Utf8_info
*/

#define PUSH(a)  *SP++ = (a)

#define MethodIsStatic(n) \
 ((*Methods[n].methodInfoP & ACC_STATIC) != 0)

JavaMiniVM
void JavaMiniVM(void *constant_pool, void *fields,
 void *methods, void *classFile,
 long methodToExecute, void *heapSpace,void *returnStack)
{
    //allocate java heap
 H0 = (long *) heapSpace;
 HP = H0;
    // allocate java stack (stack grows up in memory)
 S0 = H0 + HEAP_K * 256L; // 256 longs = 1K
 SP = S0;
 
    // return stack based at end of stack space (grows down)
 R0 = S0 + STACK_K * 256L;// 256 longs = 1K
 RP = R0;
 
 Constants = (ConstantData *) R0;
 NumConstants = IndexConstants(constant_pool, Constants);
 
 Fields = (FieldData *) (Constants + NumConstants);
 NumFields = IndexFields(fields);
 Methods = (MethodData *) (Fields + NumFields);
 NumMethods = IndexMethods(methods);
 
 ResolveFields();
 ResolveMethods();
 AllocateStaticFields();
 if (!MethodIsStatic(methodToExecute))
    CreateAndPush();    // so it needs an obj
 *(long *) returnStack =
 StartVM(&Methods[methodToExecute]);
 
}

IndexConstants
// create on index into the constant_pool
static short IndexConstants(void *constants,
 ConstantData *indexArray)
{
 short  n, i;
 u1*p;
 
    // list is preceded by length
 n = * ((u2 *) constants - 1);
 p = (u1 *) constants;
 LastField = 0;
 LastMethod = 0;
 for (i = 1; i < n; i++)
 {
 indexArray[i] = p;
 switch (*p)
 {
 case C_Utf8:  p += 3 + *(u2*)(p+1); break;
 case C_Unicode: p += 3 + *(u2*)(p+1); break;
 case C_Integer: p += 5; break;
 case C_Float: p += 5; break;
 case C_Long:  p += 9; i += 1; break;
 case C_Double:  p += 9; i += 1; break;
 case C_Class: p += 3; break;
 case C_String:  p += 3; break;
 case C_Fieldref: p += 5; LastField = i; break;
 case C_Methodref: p += 5; LastMethod = i; break;
 case C_InterfaceMethodref: p += 5; break;
 case C_NameAndType: p += 5; break;
 }
 }
 indexArray[0] = p;//useful for getting to ‘this_class’
 return n;
}

IndexFields
// Gather FieldData about each field
static short IndexFields(void *fields)
{
 short  n, i;
 u1*p;
 u1*sigP;
 u2sigIndex;
 FieldData*fieldP;
 u1c;
 long staticOffset = 0;
 long memberOffset = 0;
 
    // list is preceded by length
 n = * ((u2 *) fields - 1);
 p = (u1 *) fields;
 fieldP = Fields;
 for (i = 0; i < n; i++)
 {
 short  count; // attribute count
 
 fieldP->fieldInfoP = (u2 *) p;
 sigIndex = *(u2 *) (p + 4);
 sigP = Constants[sigIndex];
 c = *(sigP + 3);
 if (c == ‘L’ || c == ‘D’ || c == ‘F’)
 fieldP->size = 0;
 else
 fieldP->size = 4;
 fieldP->type = sigP;
 if ((*fieldP->fieldInfoP & ACC_STATIC) != 0)
 {
 fieldP->offset = staticOffset;
 staticOffset += fieldP->size;
 }
 else
 {
 fieldP->offset = memberOffset;
 memberOffset += fieldP->size;
 }



    // skip attributes
 count = * (u2 *) (p + 6);
 p += 8;
 while (count > 0)
 {
 count -= 1;
 p += 6 + *(u4 *) (p+2);
 }
 fieldP += 1;
 }
 TotalStatic = staticOffset;
 TotalNonStatic = memberOffset;
 return n;
}





IndexMethods
// Gather MethodData about each method
static short IndexMethods(void *methods)
{
 short  n, i;
 u1*p;
 MethodData *methodP;
 
    // list is preceded by length
 n = * ((u2 *) methods - 1);
 p = (u1 *) methods;
 methodP = Methods;
 for (i = 0; i < n; i++)
 {
 short  count; // attribute count
 u2nameIndex;
 u1*nameEntryP;
 
 methodP->methodInfoP = (u2 *) p;
 CountParams(methodP);
 count = * (u2 *) (p + 6);
 p += 8;
 while (count > 0)
 {
 nameIndex = * (u2 *) (p);
 nameEntryP = Constants[nameIndex];
 if (*(u2*)(nameEntryP + 1) == 4
 && *(long *) (nameEntryP + 3) == ‘Code’)
 { // this is the code attr
 methodP->codeAttrP = (u2 *) p;
 methodP->codeP = (u1 *) (p + 14);
 }
 count -= 1;
 p += 6 + *(u4 *) (p+2);
 }
 methodP += 1;
 }
 return n;
}

CreateAndPush
// allocate ‘this’ and push a reference to it
static void CreateAndPush(void)
{
 *SP = (long) HP;
 SP ++;
    // heap already initialized to zeros
 HP = (long *) ((long) HP + TotalNonStatic);
}

AllocateStaticFields
static void AllocateStaticFields(void)
{
// heap already initialized to zeros
 HP = (long *) ((long) HP + TotalStatic);
}

ResolveFields
// Change the payload of CONSTANT_Fieldref items to be a
// pointer into the FieldData array
static void ResolveFields(void)
{
 short  i, j;
 u1*p;
 u1*q;
 ConstantData  *constantP;
 FieldData*fieldP;
 u2nameTypeIndex;
 u2nameIndex;
 
 constantP = Constants+1;
 for (i = 1; i <= LastField; i++)
 {
 p = *constantP++;
 if (*p == C_Fieldref)
 {
 fieldP = Fields;
 nameTypeIndex = *(u2*) (p + 3);
 q = Constants[nameTypeIndex];
 nameIndex = *(u2*) (q + 1);
 for (j = 0; j < NumFields; j++)
 {
 if (*(fieldP->fieldInfoP+1) == nameIndex)
 { // found matching field ref, change it
 *(u4*) (p+1) = (u4) fieldP;
 break;
 }
 fieldP += 1;
 }
 }
 }
}

ResolveMethods
// Change the payload of CONSTANT_Methodref items to be a
// pointer into the MethodData array
static void ResolveMethods(void)
{
 short  i, j;
 u1*p;
 u1*q;
 ConstantData  *constantP;
 MethodData *methodP;
 u2nameTypeIndex;
 u2nameIndex;
 u2sigIndex;
 
 constantP = Constants+1;
 for (i = 1; i <= LastMethod; i++)
 {
 p = *constantP++;
 if (*p == C_Methodref)
 {
 methodP = Methods;
 nameTypeIndex = *(u2*) (p + 3);
 q = Constants[nameTypeIndex];
 nameIndex = *(u2*) (q + 1);
 sigIndex = *(u2*) (q + 3);
 for (j = 0; j < NumMethods; j++)
 {
 if (methodP->methodInfoP[1] == nameIndex
 && methodP->methodInfoP[2] == sigIndex)
 { // found matching method ref, change it
 *(u4*) (p+1) = (u4) methodP;
 break;
 }
 methodP += 1;
 }
 }
 }
}

CountParams
static void CountParams(MethodData *methodP)
{
 long sigIndex;
 long paramCount;
 u1*sigPtr;
 u2sigLength;
 u1ch;
 
 sigIndex = *(methodP->methodInfoP + 2);
 sigPtr = Constants[sigIndex];
 sigLength = * (u2 *) (sigPtr + 1);
 sigPtr += 4;    // skip tag, length and ‘(‘
 if ((*methodP->methodInfoP & ACC_STATIC) == 0)
 paramCount = 4; // implicit class object parameter
 else
 paramCount = 0;
 while (1)
 {
 ch = *sigPtr;
 if (ch == ‘)’)
 break;
 paramCount += 4;
 if (ch == ‘D’ || ch == ‘J’ || ch == ‘F’)
 paramCount -= 4;// these are 0-byte types
 else if (ch == ‘L’)
 { // skip class name


 while (*++sigPtr != ‘;’)
 ;
 }
 else if (ch == ‘[‘)
 { // we don’t care what it’s an array of
 while (*++sigPtr == ‘[‘)
 ;
 if (*sigPtr == ‘L’)
 while (*++sigPtr != ‘;’)
 ;
 }
 sigPtr += 1;
 }
 ch = *++sigPtr;
 methodP->paramCount = paramCount;
}

#define slwi(r, n) \
 rlwinm r, r, n, 0, 31-n;

#define times4(r)\
 rlwinm r, r, 2, 0, 29;

// the number after ‘used’ indicates the number of
// instructions used so far in this slot.

#define used0    \
 lbz    opcode, 0(ip);    \
 slwi(opcode, 5) \
 add    a, base, opcode;  \
 mtctr  a;\
 addi ip, ip, 1; \
 bctr;  \
 nop; nop;
 
#define used1    \
 lbz    opcode, 0(ip);    \
 slwi(opcode, 5) \
 add    a, base, opcode;  \
 mtctr  a;\
 addi ip, ip, 1; \
 bctr;  \
 nop;
 
#define used2    \
 lbz    opcode, 0(ip);    \
 slwi(opcode, 5) \
 add    a, base, opcode;  \
 mtctr  a;\
 addi ip, ip, 1; \
 bctr;
 
#define used3    \
 lbz    opcode, 0(ip);    \
 slwi(opcode, 5) \
 add    a, base, opcode;  \
 mtctr  a;\
 b next4;
 
#define used4    \
 lbz    opcode, 0(ip);    \
 slwi(opcode, 5) \
 add    a, base, opcode;  \
 b next3;
 
#define used5    \
 lbz    opcode, 0(ip);    \
 slwi(opcode, 5) \
 b next2;

#define used6    \
 lbz    opcode, 0(ip);    \
 b next1;

#define used7    \
 b next0;

#define pushtos  \
 stw    tos, 0(sp);\
 addi sp, sp, 4;

#define poptos   \
 lwzu tos, -4(sp)

#define pushi(n) \
 stw    tos, 0(sp);\
 litos, n;\
 addi sp, sp, 4;

#define pushr(r) \
 stw    tos, 0(sp);\
 mrtos, r;\
 addi sp, sp, 4;

// The initial return address           // points here.
u1 ExitCode[1] = {203};

StartVM
asm static long StartVM(register MethodData *methodP)
{
 register long *sp;
 register long *rp;
 register long *fp;
 register long *h0;
 register long *cp;// Constants
 register u1*ip; // instruction ptr
 register u1opcode;
 register long tsBase;  
// for tableswitch  padding
 register long a;
 register long b;
 register long c;
 register long base; // base of our opcode table
 register long tos;
 
 fralloc
 lwz    sp, SP
 lwz    rp, RP
 lwz    h0, H0
 lwz    cp, Constants
 lwz    a, ExitCode
 stwu a, -4(rp)  // push initial return ip
 lwzu tos, -4(sp)// put TOS into a reg.
 
// get address of opcode table
 blnowhere
nowhere:
 mflr base
// offset hard-coded since 
// MW won’t subtract labels
 addi base, base, 22*4  //table - nowhere
 
start_method:
 stwu fp, -4(rp)

 pushtos
// put tos (last param) in 
// memory
 mrfp, sp
// FP points to first parameter
 lwz    a, methodP->paramCount
 subf fp, a, fp
// allocate space for locals
 lwz    b, methodP->codeAttrP
 lhz    c, 8(b)  
// max locals
 times4(c)
 subf c, a, c
 add    sp, sp, c
// init ip
 lwz    ip, methodP->codeP
// init tsBase
 andi.  tsBase, ip, 3
 stwu tsBase, -4(rp) 
next0:
 lbz    opcode, 0(ip)
next1:
 slwi(opcode, 5)
next2:
 add    a, base, opcode
next3:
 mtctr  a
next4:
 addi ip, ip, 1
 bctr
 
table:
    // 0 nop
 used0
    // 1 aconst_null
 pushi(0)
 used3
    // 2 iconst_m1
 pushi(-1)
 used3
    // 3 iconst_0
 pushi(0)
 used3
    // 4 iconst_1
 pushi(1)
 used3
    // 5 iconst_2
 pushi(2)
 used3
    // 6 iconst_3
 pushi(3)
 used3
    // 7 iconst_4
 pushi(4)
 used3
    // 8 iconst_5
 pushi(5)
 used3
    // 9 lconst_0
 used0
    // 10 lconst_1
 used0
    // 11 fconst_0
 used0
    // 12 fconst_1
 used0
    // 13 fconst_2
 used0
    // 14 dconst_0
 used0
    // 15 dconst_1
 used0
    // 16 bipush
 lbz    a, 0(ip)
 extsb  a, a
 addi ip, ip, 1
 pushr(a)
 used6
    // 17 sipush
 lha    a, 0(ip)
 addi ip, ip, 2
 pushr(a)
 used5
    // 18 ldc1
 lbz    r3, 0(ip)
 addi ip, ip, 1
 pushtos
 b ldc_more
 nop;nop;nop
    // 19 ldc2
 lhz    r3, 0(ip)
 addi ip, ip, 2
 pushtos
 b ldc_more
 nop;nop;nop
    // 20 ldc2w
 lhz    r3, 0(ip)
 addi ip, ip, 2
 pushtos
 b ldc_more
 nop;nop;nop
    // 21 iload
 lbz    a, 0(ip)
 addi ip, ip, 1
 times4(a)
    // convert index to offset
 pushtos
 lwzx tos, a, fp
 used6
    // 22 lload
 used0
    // 23 fload
 used0
    // 24 dload
 used0
    // 25 aload
 lbz    a, 0(ip)
 addi ip, ip, 1
 times4(a)
    // convert index to offset
 pushtos
 lwzx tos, a, fp
 used6
    // 26 iload_0
 pushtos
 lwz    tos, 0(fp)
 used3
    // 27 iload_1
 pushtos
 lwz    tos, 4(fp)
 used3
    // 28 iload_2
 pushtos
 lwz    tos, 8(fp)
 used3
    // 29 iload_3
 pushtos
 lwz    tos, 12(fp)
 used3
    // 30 lload_0
 used0
    // 31 lload_1
 used0
    // 32 lload_2
 used0
    // 33 lload_3
 used0
    // 34 fload_0
 used0
    // 35 fload_1
 used0
    // 36 fload_2
 used0
    // 37 fload_3
 used0
    // 38 dlload_0
 used0
    // 39 dload_1
 used0
    // 40 dload_2
 used0
    // 41 dload_3
 used0
    // 42 aload_0
 pushtos
 lwz    tos, 0(fp)
 used3
    // 43 aload_1
 pushtos
 lwz    tos, 4(fp)
 used3
    // 44 aload_2
 pushtos
 lwz    tos, 8(fp)
 used3
    // 45 aload_3
 pushtos
 lwz    tos, 12(fp)
 used3
    // 46 iaload
 lwzu b, -4(sp)  
    // get array address
 mra, tos
 addi b, b, 4
 times4(a)
    // convert index to offset
 lwzx tos, a, b
 used5
    // 47 laload
 lwzu tos, -8(sp)
    // drop2
 used1
    // 48 faload
 lwzu tos, -8(sp)
    // drop2
 used1
    // 49 daload
 lwzu tos, -8(sp)
    // drop2
 used1
    // 50 aaload
 lwzu b, -4(sp)  
    // get array address
 mra, tos
 addi b, b, 4
 times4(a)
    // convert index to offset
 lwzx tos, a, b
 used5
    // 51 baload
 lwzu b, -4(sp)  
    // get array address
 addi b, b, 4
 lbzx tos, tos, b
 extsb  tos, tos
 used4
    // 52 caload
 lwzu b, -4(sp)  
    // get array address
 mra, tos
 addi b, b, 4
 slwi(a, 1) 
 lhzx tos, a, b
 used5
    // 53 saload
 lwzu b, -4(sp)  
    // get array address
 mra, tos
 addi b, b, 4
 slwi(a, 1) 
    // convert index to offset
 lhax tos, a, b
 used5
    // 54 istore
 lbz    a, 0(ip)
 addi ip, ip, 1
 times4(a)
    // convert index to offset
 stwx tos, a, fp
 lwzu tos, -4(sp)
 used5
    // 55 lstore
 used0
    // 56 fstore
 used0
    // 57 dstore
 used0
    // 58 astore
 lbz    a, 0(ip)
 addi ip, ip, 1
 times4(a)
    // convert index to offset
 stwx tos, a, fp
 lwzu tos, -4(sp)
 used5
    // 59 istore_0
 stw    tos, 0(fp)
 lwzu tos, -4(sp)
 used2
    // 60 istore_1
 stw    tos, 4(fp)
 lwzu tos, -4(sp)
 used2
    // 61 istore_2
 stw    tos, 8(fp)
 lwzu tos, -4(sp)
 used2
    // 62 istore_3
 stw    tos, 12(fp)
 lwzu tos, -4(sp)
 used2
    // 63 lstore_0
 used0
    // 64 lstore_1
 used0
    // 65 lstore_2
 used0
    // 66 lstore_3
 used0
    // 67 fstore_0
 used0
    // 68 fstore_1
 used0
    // 69 fstore_2
 used0
    // 70 fstore_3
 used0
    // 71 dstore_0
 used0
    // 72 dstore_1
 used0
    // 73 dstore_2
 used0
    // 74 dstore_3
 used0
    // 75 astore_0
 stw    tos, 0(fp)
 lwzu tos, -4(sp)
 used2
    // 76 astore_1
 stw    tos, 4(fp)
 lwzu tos, -4(sp)
 used2
    // 77 astore_2
 stw    tos, 8(fp)
 lwzu tos, -4(sp)
 used2
    // 78 astore_3
 stw    tos,12(fp)
 lwzu tos, -4(sp)
 used2
    // 79 iastore
 lwzu b, -4(sp)  
    // index
 lwzu c, -4(sp)  
    // array address
 times4(b)
    // index to offset
 addi c, c, 4    
    // skip arraylength field
 stwx tos, b, c
 lwzu tos, -4(sp)
 used6
    // 80 lastore
 lwzu tos, -8(sp)
    // drop2
 used1
    // 81 fastore
 lwzu tos, -8(sp)
    // drop2
 used1
    // 82 dastore
 lwzu tos, -8(sp)
    // drop2
 used1
    // 83 aastore
 lwzu b, -4(sp)  
    // index
 lwzu c, -4(sp)  
    // array address
 times4(b)
    // index to offset
 addi c, c, 4    
    // skip arraylength field
 stwx tos, b, c
 lwzu tos, -4(sp)
 used6
    // 84 bastore
 lwzu b, -4(sp)  
    // index
 lwzu c, -4(sp)  
    // array address
 addi c, c, 4    
    // skip arraylength field
 stbx tos, b, c
 lwzu tos, -4(sp)
 used5
    // 85 castore
 lwzu b, -4(sp)  
    // index
 lwzu c, -4(sp)  
    // array address
 slwi(b, 1) 
    // index to offset
 addi c, c, 4    
    // skip arraylength field
 sthx tos, b, c
 lwzu tos, -4(sp)
 used6
    // 86 sastore
 lwzu b, -4(sp)  
    // index
 lwzu c, -4(sp)  
    // array address
 slwi(b, 1) 
    // index to offset
 addi c, c, 4  
    // skip arraylength field
 sthx tos, b, c
 lwzu tos, -4(sp)
 used6
    // 87 pop
 lwzu tos, -4(sp)
 used1
    // 88 pop2
 lwzu tos, -8(sp)
 used1
    // 89 dup
 pushtos
 used2
    // 90 dup_x1
 lwz    a, -4(sp)
 stw    tos, -4(sp)
 stw    a, 0(sp)
 addi sp, sp, 4
 used4
    // 91 dup_x2
 lwz    a, -8(sp)
 lwz    b, -4(sp)
 stw    tos, -8(sp)
 stw    a, -4(sp)
 stw    b, 0(sp)
 addi sp, sp, 4
 used6
    // 92 dup2
 lwz    a, -4(sp)
 stw    tos, 0(sp)
 stw    a, 4(sp)
 addi sp, sp, 8
 used4
    // 93 dup2_x1
 lwz    a, -8(sp)
 lwz    b, -4(sp)
 stw    b, -8(sp)
 stw    tos, -4(sp)
 stw    a, 0(sp)
 stw    b, 4(sp)
 addi sp, sp, 8
 used7
    // 94 dup2_x2
 lwz    a, -12(sp)
 lwz    b, -8(sp)
 lwz    c, -4(sp)
 stw    c, -12(sp)
 stw    tos, -8(sp)
 stw    a, -4(sp)
 stw    b, 0(sp)
 b dup2_x2_more
    // 95 swap
 lwz    a, -4(sp)
 stw    tos, -4(sp)
 mrtos, a
 used3



    // 96 iadd
 lwzu a, -4(sp)
 add    tos, a, tos
 used2
    // 97 ladd
 used6  
 // pretend we had 6          // instructions already
    // stash the rest of          // dup2_x2 here
 dup2_x2_more:
 stw    c, 4(sp)
 addi sp, sp, 8
 used4
    // 98 fadd
 used0
    // 99 dadd
 used0
    // 100 isub
 lwzu a, -4(sp)
 subf tos, tos, a
 used2
    // 101 lsub
 used0
    // 102 fsub
 used0
    // 103 dsub
 used0
    // 104 imul
 lwzu a, -4(sp)
 mullw  tos, tos, a
 used2
    // 105 lmul
 used0
    // 106 fmul
 used0
    // 107 dmul
 used0
    // 108 idiv
 lwzu a, -4(sp)
 divw tos, a, tos
 used2
    // 109 ldiv
 used0
    // 110 fdiv
 used0
    // 111 ddiv
 used0
    // 112 irem
 lwzu a, -4(sp)
 divw b, a, tos
 mullw  c, b, tos
 subf tos, c, a
 used4
    // 113 lrem
 used0
    // 114 frem
 used0
    // 115 drem
 used0
    // 116 ineg
 neg    tos, tos
 used1
    // 117 lneg
 used0
    // 118 fneg
 used0
    // 119 dneg
 used0
    // 120 ishl
 lwzu a, -4(sp)
 andi.  tos, tos, 31
 slw    tos, a, tos
 used3
    // 121 lshl
 lwzu tos, -4(sp)
 used1
    // 122 ishr
 lwzu a, -4(sp)
 andi.  tos, tos, 31
 sraw tos, a, tos
 used3
    // 123 lshr
 lwzu tos, -4(sp)
 used1
    // 124 iushr
 lwzu a, -4(sp)
 andi.  tos, tos, 31
 srw    tos, a, tos
 used3
    // 125 lushr
 lwzu tos, -4(sp)
 used1
    // 126 iand
 lwzu a, -4(sp)
 and    tos, tos, a
 used2
    // 127 land
 used0
    // 128 ior
 lwzu a, -4(sp)
 ortos, tos, a
 used2
    // 129 lor
 used0
    // 130 ixor
 lwzu a, -4(sp)
 xor    tos, tos, a
 used2
    // 131 lxor
 used0
    // 132 iinc
 lhz    b, 0(ip)
 rlwinm a, b, 26,  16, 29
 extsb  b, b
 addi ip, ip, 2
 lwzx c, fp, a
 add    c, c, b
 stwx c, fp, a
 used7
    // 133 i2l
 lwzu tos, -4(sp)
 used1
    // 134 i2f
 lwzu tos, -4(sp)
 used1
    // 135 i2d
 lwzu tos, -4(sp)
 used1
    // 136 l2i
 pushi(0)
 used3
    // 137 l2f
 used0
    // 138 l2d
 used0
    // 139 f2i
 pushi(0)
 used3
    // 140 f2f
 used0
    // 141 f2d
 used0
    // 142 d2i
 pushi(0)
 used3
    // 143 d2f
 used0
    // 144 d2d
 used0
    // 145 int2byte
 extsb  tos, tos
 used1
    // 146 int2char
 andi.  tos, tos,  0xffff
 used1
    // 147 int2short
 extsh  tos, tos
 used1
    // 148 lcmp
 pushi(0)
 used3
    // 149 fcmpl
 pushi(0)
 used3
    // 150 fcmpg
 pushi(0)
 used3
    // 151 dcmpl
 pushi(0)
 used3
    // 152 dcmpg
 pushi(0)
 used3
    // 153 ifeq
 cmpi cr0, 0, tos, 0
 lha    a, 0(ip)
 lwzu tos, -4(sp)
 addi ip, ip, 2
 subi a, a, 3
 bne    next0
 add    ip, ip, a
 used7
    // 154 ifne
 cmpi cr0, 0, tos, 0
 lha    a, 0(ip)
 lwzu tos, -4(sp)
 addi ip, ip, 2
 subi a, a, 3
 beq    next0
 add    ip, ip, a
 used7
    // 155 iflt
 cmpi cr0, 0, tos, 0
 lha    a, 0(ip)
 lwzu tos, -4(sp)
 addi ip, ip, 2
 subi a, a, 3
 bge    next0
 add    ip, ip, a
 used7
    // 156 ifge
 cmpi cr0, 0, tos, 0
 lha    a, 0(ip)
 lwzu tos, -4(sp)
 addi ip, ip, 2
 subi a, a, 3
 blt    next0
 add    ip, ip, a
 used7
    // 157 ifgt
 cmpi cr0, 0, tos, 0
 lha    a, 0(ip)
 lwzu tos, -4(sp)
 addi ip, ip, 2
 subi a, a, 3
 ble    next0
 add    ip, ip, a
 used7
    // 158 ifle
 cmpi cr0, 0, tos, 0
 lha    a, 0(ip)
 lwzu tos, -4(sp)
 addi ip, ip, 2
 bgt    next0
// shared by cmp instructions
 do_jump: 
 subi a, a, 3
 add    ip, ip, a
 used7
    // 159 if_icmpeq
 lwz    b, -4(sp)
 cmp    cr0, 0, b, tos
 lha    a, 0(ip)
 lwzu tos, -8(sp)
 addi ip, ip, 2
 beq    do_jump
 used6
    // 160 if_icmpne
 lwz    b, -4(sp)
 cmp    cr0, 0, b, tos
 lha    a, 0(ip)
 lwzu tos, -8(sp)
 addi ip, ip, 2
 bne    do_jump
 used6
    // 161 if_icmplt
 lwz    b, -4(sp)
 cmp    cr0, 0, b, tos
 lha    a, 0(ip)
 lwzu tos, -8(sp)
 addi ip, ip, 2
 blt    do_jump
 used6
    // 162 if_icmpge
 lwz    b, -4(sp)
 cmp    cr0, 0, b, tos
 lha    a, 0(ip)
 lwzu tos, -8(sp)
 addi ip, ip, 2
 bge    do_jump
 used6
    // 163 if_icmpgt
 lwz    b, -4(sp)
 cmp    cr0, 0, b, tos
 lha    a, 0(ip)
 lwzu tos, -8(sp)
 addi ip, ip, 2
 bgt    do_jump
 used6
    // 164 if_icmple
 lwz    b, -4(sp)
 cmp    cr0, 0, b, tos
 lha    a, 0(ip)
 lwzu tos, -8(sp)
 addi ip, ip, 2
 ble    do_jump
 used6
    // 165 if_acmpeq
 lwz    b, -4(sp)
 cmp    cr0, 0, b, tos
 lha    a, 0(ip)
 lwzu tos, -8(sp)
 addi ip, ip, 2
 beq    do_jump
 used6
    // 166 if_acmpne
 lwz    b, -4(sp)
 cmp    cr0, 0, b, tos
 lha    a, 0(ip)
 lwzu tos, -8(sp)
 addi ip, ip, 2
 bne    do_jump
 used6
    // 167 goto
 lha    a, 0(ip)
 subi   ip, ip, 1
 add    ip, ip, a
 used3
    // 168 jsr
 pushtos
 lha    a, 0(ip)
 addi tos, ip, 2 
    // addr of next instr
 subi ip, ip, 1
 add    ip, ip, a
 used6
    // 169 ret
 lbz    a, 0(ip)
 times4(a)
    // convert to offset
 lwzx ip, fp, a
 used3
    // 170 tableswitch
 mrr3, ip
 mrr4, tsBase
 mrr5, tos
 blTableSwitch
 mrip, r3
 poptos
 used6
    // 171 lookupswitch
 mrr3, ip
 mrr4, tsBase
 mrr5, tos
 blLookupSwitch
 mrip, r3
 poptos
 used6
    // 172 ireturn
 lwz    ip, 8(rp)
 mrsp, fp
 lwz    fp, 4(rp)
 lwz    tsBase,  0(rp)
 addi rp, rp, 12
 used5
    // 173 lreturn
 lwz    ip, 8(rp)
 mrsp, fp
 lwz    fp, 4(rp)
 lwz    tsBase,  0(rp)
 lwzu tos, -4(sp)
 addi rp, rp, 12
 used6
    // 174 freturn
 lwz    ip, 8(rp)
 mrsp, fp
 lwz    fp, 4(rp)
 lwz    tsBase,  0(rp)
 lwzu tos, -4(sp)
 addi rp, rp, 12
 used6
    // 175 dreturn
 lwz    ip, 8(rp)
 mrsp, fp
 lwz    fp, 4(rp)
 lwz    tsBase,  0(rp)
 lwzu tos, -4(sp)
 addi rp, rp, 12
 used6
    // 176 areturn
 lwz    ip, 8(rp)
 mrsp, fp
 lwz    fp, 4(rp)
 lwz    tsBase,  0(rp)
 addi rp, rp, 12
 used5
    // 177 return
 lwz    ip, 8(rp)
 mrsp, fp
 lwz    fp, 4(rp)
 lwz    tsBase,  0(rp)
 lwzu tos, -4(sp)
 addi rp, rp, 12
 used6
    // 178 getstatic
 lhz    a, 0(ip)
 addi ip, ip, 2
 times4(a)
 lwzx b, cp, a
 b getstatic_more
 nop;nop;nop



    // 179 putstatic
 lhz    a, 0(ip)
 addi ip, ip, 2
 times4(a)
 lwzx b, cp, a
 b putstatic_more
 nop;nop;nop
    // 180 getfield
 lhz    a, 0(ip)
 addi ip, ip, 2
 times4(a)
 lwzx b, cp, a
 b getfield_more
 nop;nop;nop
    // 181 putfield
 lhz    a, 0(ip)
 addi ip, ip, 2
 times4(a)
 lwzx b, cp, a
 b putfield_more
 nop;nop;nop
    // 182 invokevirtual
 lhz    a, 0(ip)
 addi ip, ip, 2
 times4(a)
    // convert to index
 lwzx a, cp, a
 lwz    methodP, 1(a)
 stwu ip, -4(rp)
 b start_method
 nop
    // 183 invokenonvirtual
 lhz    a, 0(ip)
 addi ip, ip, 2
 times4(a)
    // convert to index
 lwzx a, cp, a
 lwz    methodP, 1(a)
 stwu ip, -4(rp)
 b start_method
 nop
    // 184 invokestatic
 lhz    a, 0(ip)
 addi ip, ip, 2
 times4(a)// convert to index
 lwzx a, cp, a
 lwz    methodP, 1(a)
 stwu ip, -4(rp)
 b start_method
 nop
    // 185 invokeinterface
 addi ip, ip, 2
 used1
    // 186 undefined
 used0
    // 187 new
 addi ip, ip, 2
 used1
    // 188 newarray
 lbz    r3, 0(ip)
 addi ip, ip, 1
 mrr4, tos
 blGetNewArray
 mrtos, r3
 used5
    // 189 anewarray
 addi ip, ip, 2  
    // skip type
 mrr3, tos
 blGetANewArray
 mrtos, r3
 used4
    // 190 arraylength
 lwz    tos, 0(tos)
 used1
    // 191 athrow
 used0
    // 192 checkcast
 addi ip, ip, 2
 used1
    // 193 instanceof
 addi ip, ip, 2
 litos, 1 
 // assume true
 used2
    // 194 monitorenter
 poptos
 used1
    // 195 monitorexit
 poptos
 used1
    // 196 wide
 addi ip, ip, 1
 used1
    // 197 multianewarray
 lhz    r3, 0(ip)
 lbz    r4, 2(ip)
 addi ip, ip, 3
 pushtos
 b multianewarray_more
 nop;nop;
    // 198 ifnull
 cmpi cr0, 0, tos, 0
 lha    a, 0(ip)
 lwzu tos, -4(sp)
 addi ip, ip, 2
 subi a, a, 3
 bne    next0
 add    ip, ip, a
 used7
    // 199 ifnonnull
 cmpi cr0, 0, tos, 0
 lha    a, 0(ip)
 lwzu tos, -4(sp)
 addi ip, ip, 2
 subi a, a, 3
 beq    next0
 add    ip, ip, a
 used7
    // 200 goto_w
 lwz    a, 0(ip)
 subi a, a, 1
 add    ip, ip, a
 used3
    // 201 jsr_w
 pushtos
 lwz    a, 0(ip)
 addi tos, ip, 5
 subi a, a, 1
 add    ip, ip, a
 used6
    // 202 breakpoint
 used0
    // 203 unused - but we use  // it to signal final exit
 b exitVM
 used1
 used0    // 204
 used0    // 205
 used0    // 206
 used0    // 207
 used0    // 208
    // 209 ret_w
 lhz    a, 0(ip)
 times4(a)
 lwzx ip, fp, a
 used3

// remaining opcodes unused
 
exitVM:
 mrr3, tos
 frfree
 blr

ldc_more:
 stw    sp, SP
 blPushConstant
 lwz    sp, SP
 poptos
 b next0
 
multianewarray_more:
 stw    sp, SP
 blPushMultiANewArray
 lwz    sp, SP
 poptos
 b next0

getstatic_more:
 lwz    a, 1(b)  
// get fieldP
 lwz    b, 8(a)  
// get size
 cmpi cr0, 0, b, 0
 lwz    c, 4(a)  
// get offset
 beq    next0
 pushtos
 lwzx tos, h0, c
 b next0
 
putstatic_more:
 lwz    a, 1(b)  
// get fieldP
    lwzb, 8(a)        
// get size
 cmpi cr0, 0, b, 0
 lwz    c, 4(a)  
// get offset
 beq    drop1ngo
 stwx tos, h0, c
 poptos
 b next0
 
getfield_more:
 lwz    a, 1(b)  
// get fieldP
 lwz    b, 8(a)  
// get size
 cmpi cr0, 0, b, 0
 lwz    c, 4(a)  
// get offset
 beq    drop1ngo
 lwzx tos, tos, c
 b next0
 
putfield_more:
 lwz    a, 1(b)  
// get fieldP
 lwz    b, 8(a)  
// get size
 cmpi cr0, 0, b, 0
 lwz    c, 4(a)  
// get offset
 beq    drop2ngo
 lwzu a, -4(sp)
 stwx tos, a, c
 poptos
 b next0

drop2ngo:
 poptos
drop1ngo:
 poptos
 b next0
 
}

PushConstant
static void PushConstant(long n)
{
 u1*p;
 
 p = Constants[n];
 switch (*p++)
 {
 case C_Utf8:
 case C_Unicode:
    
    // since no operations act   // on these objects,
    // I just make the const // data be the object
    // (w/o the tag) for     // simplicity of the test
    // code.
 PUSH((long)p);
 break;
 case C_Integer: PUSH(*(s4*)p);
 break;
 case C_Float:   break;
 case C_Long:    break;
 case C_Double:  break;
 case C_Class:   break;
 case C_String:
 PushConstant
 (*(u2*)p);
 break;
 case C_Fieldref:
 case C_Methodref:
 case C_InterfaceMethodref:
 case C_NameAndType:
 DebugStr
(“\pit can happen”);
 break;
 }
}

TableSwitch
static u1 *TableSwitch(u1 *ip, long tsBase, long n)
{
 long *base;
 long defaultOffset;
 long low;
 long high;
 
 base = (long *) (((((long)ip-tsBase) + 3) & -4)+tsBase);
 defaultOffset = *base++;
 low = *base++;
 high = *base++;
 ip -= 1;
 
 if (n < low || n > high)
 ip += defaultOffset;
 else
 ip += base[n - low];
 return ip;
}

LookupSwitch
static u1 *LookupSwitch(u1 *ip, long tsBase, long key)
{
 long *base;
 long defaultOffset;
 long numPairs;
 long match;
 base = (long *) (((((long)ip-tsBase) + 3) & -4)+tsBase);
 defaultOffset = *base++;
 numPairs = *base++;
 ip -= 1;
 
 while (numPairs > 0)
 {
 match = *base++;
 numPairs -= 1;
 if (key == match)
 return ip + *base;
 base += 1;
 }
 return ip + defaultOffset;
}

GetNewArray
// Array object: # elements, data
// data is padded to multiple of 4
static long GetNewArray(long type, long size)
{
 long   result;
 long   elementSize;
 
 result = (long) HP;
 *HP++ = size;
 if (type == 10) 
    // int
 elementSize = 4;
 else if ((type & 3) == 0)
    // boolean or byte
 elementSize = 1;
 else if ((type & 3) == 1)
    // char or short
 elementSize = 2;
 else
 elementSize = 0;
    // unsupported types
 HP += ((size * elementSize + 3) >> 2);
 return result;
}

GetANewArray
static long GetANewArray(long size)
{
 long   result;
 long   elementSize;
 u4*objectP;
 
 result = (long) HP;
 *HP++ = size;
 elementSize = 4;
 objectP = (u4*) HP;
 HP = (long *) ((u1 *) HP + size * 4);
 while (size > 0)
 {
 size -= 1;
 *objectP = (u4)HP;
 HP += elementSize;
 }
 return result;
}

PushMultiANewArray
// Rather complicated function to allocate a
// multi-dimensional array as arrays of array objects.
static void PushMultiANewArray(long classIndex,
 long numDimensions)
{
 u1*cp;
 long nameIndex;
 u1*name;
 int    type;
 long elementSize;
 long arrayRef;
 long size;
 long copies;
 long i, j;
 long dim;
 long dataLongs;
 long *subArrayRef;
 long subArrayLongs;
 
 arrayRef = (long) HP;
 cp = Constants[classIndex];
 nameIndex = *(u2*) (cp+1);
 cp = Constants[nameIndex];
 name = cp + 3;
 type = name[numDimensions];
 // skip the known ‘[‘ chars
 if (type == ‘I’ || type == ‘[‘)   
 // int or ref
 elementSize = 4;
 else if (type == ‘Z’ || type == ‘B’)// bool or byte
 elementSize = 1;
 else if (type == ‘C’ || type == ‘S’)// char or short
 elementSize = 2;
 else
 elementSize = 0;// unsupported types
 copies = 1;

 size = *(SP-1); // the nth dimension
 dataLongs = (size * elementSize + 3) >> 2;
 for (dim = 0; dim < numDimensions - 1; dim++)
 {
 size = *(SP-numDimensions+dim);
 if (dim == numDimensions - 2)
 subArrayLongs = dataLongs + 1;
 else
 subArrayLongs = *(SP-numDimensions+dim+1) + 1;
 subArrayRef = HP + (size + 1) * copies;
 for (i = 0; i < copies; i++)
 {
 *HP++ = size;
 for (j = 0; j < size; j++)
 {
 *HP++ = (long) subArrayRef;
 subArrayRef += subArrayLongs;
 }
 }
 copies *= size;
 }
    // last dim is special since it has no subarrays
 size = *(SP-1); // the nth dimension
 for (i = 0; i < copies; i++)
 {
 *HP++ = size;
 HP += dataLongs;
 }
 SP -= numDimensions;
 // remove dimensions
 PUSH(arrayRef);
}

 
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