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How can I use JNA to pass byte[][] to go

This is go code
import (
"C"
"fmt"
)
//export Print
func Print(keys, values [][]byte) {
for len(keys) > 0 {
err := txn.Set(keys[0], values[0])
errMustBeNil(err)
fmt.Printf("%s %s", string(keys[0]), string(values[0]))
keys = keys[1:]
values = values[1:]
}
}
This is libPrint.h
/*
static assertion to make sure the file is being used on architecture
at least with matching size of GoInt.
*/
typedef char _check_for_64_bit_pointer_matching_GoInt[sizeof(void*)==64/8 ? 1:-1];
#ifndef GO_CGO_GOSTRING_TYPEDEF
typedef _GoString_ GoString;
#endif
typedef void *GoMap;
typedef void *GoChan;
typedef struct { void *t; void *v; } GoInterface;
typedef struct { void *data; GoInt len; GoInt cap; } GoSlice;
#endif
/* End of boilerplate cgo prologue. */
#ifdef __cplusplus
extern "C" {
#endif
extern void Print(GoSlice keys, GoSlice values);
#ifdef __cplusplus
}
#endif
This is my Java code,I want to put byte[] into pointer one by one,GoSlice is represents the array[] in go,I don't know if this is correct
public interface Test extends Library {
Test TEST = (Test) Native.load("Print", Test.class);
void Print(GoSlice key, GoSlice val);
class GoSlice extends Structure {
public Pointer[] data;
public long len;
public long cap;
}
static void main(String[] args) {
byte[] byte1 = "key1".getBytes(StandardCharsets.UTF_8);
byte[] byte2 = "value1new".getBytes(StandardCharsets.UTF_8);
GoSlice keys = new GoSlice();
keys.data = new Pointer[1];
keys.data[0] = new Pointer(byte1.length + 1);
keys.len = 1;
keys.cap = 1;
GoSlice values = new GoSlice();
values.data = new Pointer[1];
keys.data[0] = new Pointer(byte2.length + 1);
values.len = 1;
values.cap = 1;
keys.data[0].write(0, byte1, 0, byte1.length);
values.data[0].write(0, byte2, 0, byte2.length);
Test.TEST.Print(keys, values);
}
}
But it doesn't work correctly,I feel that byte[][] is not correctly converted to the type in go.
This is the console log after running the Java program
#
# A fatal error has been detected by the Java Runtime Environment:
#
# SIGSEGV (0xb) at pc=0x00000001a2775a34, pid=64329, tid=0x0000000000002903
#
# JRE version: OpenJDK Runtime Environment (Zulu 8.62.0.19-CA-macos-aarch64) (8.0_332-b09) (build 1.8.0_332-b09)
# Java VM: OpenJDK 64-Bit Server VM (25.332-b09 mixed mode bsd-aarch64 compressed oops)
# Problematic frame:
# C [libsystem_platform.dylib+0x3a34] _platform_memmove+0xf4
#
# Failed to write core dump. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#
# An error report file with more information is saved as:
# /Users/user/project/hs_err_pid64329.log
#
# If you would like to submit a bug report, please visit:
# http://www.azul.com/support/
#
This is my first change
public interface TxnClient extends Library {
TxnClient TNX_CLIENT = (TxnClient) Native.load("Tikv", TxnClient.class);
int TxnSave(GoSlice[] key, GoSlice[] val);
class GoSlice extends Structure {
public long cap;
public Pointer data;
public long len;
#Override
protected List<String> getFieldOrder() {
return Arrays.asList("cap", "data", "len");
}
}
static void main(String[] args) {
byte[] key1 = "key1".getBytes(StandardCharsets.UTF_8);
byte[] value1 = "value1new".getBytes(StandardCharsets.UTF_8);
byte[] key2 = "key2".getBytes(StandardCharsets.UTF_8);
byte[] value2 = "value2new".getBytes(StandardCharsets.UTF_8);
GoSlice tmp = new GoSlice();
GoSlice[] keys = (GoSlice[]) tmp.toArray(2);
keys[0].data = new Memory(key1.length + 1);
keys[0].len = keys[0].cap = key1.length;
keys[0].data.write(0, key1, 0, key1.length);
keys[1].data = new Memory(key2.length + 1);
keys[1].len = keys[1].cap = key2.length;
keys[1].data.write(0, key2, 0, key2.length);
GoSlice[] values = (GoSlice[]) tmp.toArray(2);
values[0].data = new Memory(value1.length + 1);
values[0].len = values[0].cap = value1.length;
values[0].data.write(0, value1, 0, value1.length);
values[1].data = new Memory(value2.length + 1);
values[1].len = values[1].cap = value2.length;
values[1].data.write(0, value2, 0, value2.length);
int i = TxnClient.TNX_CLIENT.TxnSave(keys, values);
System.out.println(i);
}
}
5431788016 5431788016panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x9 pc=0x1225b2b80]
goroutine 17 [running, locked to thread]:
main.TxnSave({0x9, 0x143c281f0, 0x14000182000?}, {0x9, 0x143c281f0, 0x121daf2c8?})
/Users/user/project/print.go:52 +0x180
second change
//export TxnSave
func TxnSave(keys, values [][]byte) (res int) {
// ignore
}
public interface TxnClient extends Library {
TxnClient TNX_CLIENT = (TxnClient) Native.load("Tikv", TxnClient.class);
int TxnSave(GoSlice key, GoSlice val);
class GoSlice extends Structure {
public long cap;
public Pointer data;
public long len;
#Override
protected List<String> getFieldOrder() {
return Arrays.asList("cap", "data", "len");
}
}
static void main(String[] args) {
byte[] key1 = "key1".getBytes(StandardCharsets.UTF_8);
byte[] value1 = "value1new".getBytes(StandardCharsets.UTF_8);
byte[] key2 = "key2".getBytes(StandardCharsets.UTF_8);
byte[] value2 = "value2new".getBytes(StandardCharsets.UTF_8);
GoSlice keys = new GoSlice();
keys.data = new Memory(key1.length + key2.length + 1);
keys.data.write(0, key1, 0, key1.length);
keys.len = keys.cap = key1.length + key2.length;
keys.data.write(key1.length, key2, 0, key2.length);
GoSlice values = new GoSlice();
values.data = new Memory(value1.length + value2.length + 1);
values.len = values.cap = value1.length + value2.length;
values.data.write(0, value1, 0, value1.length);
values.data.write(value1.length, value2, 0, value2.length);
int i = TxnClient.TNX_CLIENT.TxnSave(keys, values);
System.out.println(i);
}
}
[2022/07/31 22:36:57.225 +08:00] [INFO] [client.go:378] ["[pd] create pd client with endpoints"] [pd-address="[127.0.0.1:2379]"]
[2022/07/31 22:36:57.228 +08:00] [INFO] [base_client.go:350] ["[pd] switch leader"] [new-leader=http://127.0.0.1:2379] [old-leader=]
[2022/07/31 22:36:57.228 +08:00] [INFO] [base_client.go:105] ["[pd] init cluster id"] [cluster-id=7126545341327379321]
[2022/07/31 22:36:57.228 +08:00] [INFO] [client.go:673] ["[pd] tso dispatcher created"] [dc-location=global]
4981923696 4981923392panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x8 pc=0x12b00a6e0]
// this is error
goroutine 17 [running, locked to thread]:
main.TxnSave({0x8, 0x128f21f70, 0x14000190000?}, {0x12, 0x128f21e40, 0x12a806d38?})
/Users/user/go-tikv/tikv.go:53 +0x180

You're misunderstanding the Pointer constructor's argument. It's a native peer value, not an allocation size.
What you have:
keys.data[0] = new Pointer(byte1.length + 1);
From the Pointer Javadoc:
public Pointer(long peer)
Create from native pointer. Don't use this unless you know what you're doing.
The correct way to allocate new memory (which calls malloc() internally) is the Memory class which extends Pointer. The argument for the Memory constructor is indeed the size:
public Memory(long size)
Allocate space in the native heap via a call to C's malloc.
Parameters:
size - number of bytes of space to allocate
So you want:
keys.data[0] = new Memory(byte1.length + 1);
One other note:
Memory isn't cleared on allocation, so if you want that "+1" null terminator you need to either clear() the memory or explicitly set that null byte when writing a string to it (or perhaps append a null byte to the string in Java before converting to bytes).
Updating for your follow-on questions:
You have a mismatch between the C header (which has data first followed by len and cap and your own GoSlice structure definition which puts data in the middle. When you pass this to native, you are just sending the value of that initial long which is probably zero, and getting the nil pointer error.
Additionally, you are not allocating enough memory for what you're doing. When you declare a Structure in JNA it allocates the memory it needs. In your earlier version of code you used Structure.toArray() to allocate more memory for more structures -- this was correct (but you did it twice!). You should do that once.
In your latest code you set value as just one GoSlice structure. That memory is just 24 bytes, for the two longs and the Pointer. But then for your second array value you are using the original data (which is in the wrong order) and trying to write to a memory location that isn't even allocated.
In summary:
Declare the field order in your Java GoSlice to match the native header
Use the Structure's toArray() on an initial GoSlice structure to allocate space for an array of them.
Use the data field of the GoSlice[n] structure to write the string values to.

crc 16 bit array using java reading in full lines

hello I am trying to use this code to ultimately be able to add a file into it so it reads the file and runs through this crc16 but I keep getting this error
"Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
at Main.main(Main.java:51)
"
public class Main
{
public static void main(String[] args)
{
int[] table =
{
0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040,
};
byte[] bytes = args[0].getBytes();
int crc = 0x0000;
for (byte b : bytes)
{
crc = (crc >>> 8) ^ table[(crc ^ b) & 0xff];
}
System.out.println("CRC16 = " + Integer.toHexString(crc));
}
}

StringTemplate 4 set condition from java

How to set ST4 condition from Java?
I have following ST4 template
templateExample(param) ::= <<
$if (condition)$
<ul><li>$param$ is true</li></ul>
$else$
<ul><li>$param$ is false</li></ul>
$endif$
>>
While the main class is
public static void main(String[] args) {
final STGroup stGroup = new STGroupFile("exampleTemplate.stg", '$', '$');
stGroup.registerRenderer(String.class, new StringRenderer());
final ST templateExample = stGroup.getInstanceOf("templateExample");
templateExample.add("param", "Hello World");
templateExample.add("condition", true);
System.out.println(templateExample.render());
}
However when i run the code, following error raised :
Exception in thread "main" java.lang.IllegalArgumentException: no such attribute: condition
at org.stringtemplate.v4.ST.add(ST.java:226)
at com.cupidocreative.main.StringTemplateSandboxMain.main(StringTemplateSandboxMain.java:16)
How to set the "condition" from my java class?
Thanks in advance

here is my solution
templateExample(condition, param) ::= <<
$if (condition)$
<ul><li>$param$ is true</li></ul>
$else$
<ul><li>$param$ is false</li></ul>
$endif$
>>

PY4J callback server error

I'm trying to run the example for the callback server in the PY4J website
here
But I'm getting the following exception:
"py4j.protocol.Py4JNetworkError: An error occurred while trying to start the callback server"
This is the code:
Java:
package py4j.examples;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import py4j.GatewayServer;
public class OperatorExample {
// To prevent integer overflow
private final static int MAX = 1000;
public List<Integer> randomBinaryOperator(Operator op) {
Random random = new Random();
List<Integer> numbers = new ArrayList<Integer>();
numbers.add(random.nextInt(MAX));
numbers.add(random.nextInt(MAX));
numbers.add(op.doOperation(numbers.get(0), numbers.get(1)));
return numbers;
}
public List<Integer> randomTernaryOperator(Operator op) {
Random random = new Random();
List<Integer> numbers = new ArrayList<Integer>();
numbers.add(random.nextInt(MAX));
numbers.add(random.nextInt(MAX));
numbers.add(random.nextInt(MAX));
numbers.add(op.doOperation(numbers.get(0), numbers.get(1), numbers.get(2)));
return numbers;
}
public static void main(String[] args) {
GatewayServer server = new GatewayServer(new OperatorExample());
server.start();
}
}
Interface:
package py4j.examples;
public interface Operator {
public int doOperation(int i, int j);
public int doOperation(int i, int j, int k);
}
Python:
from py4j.java_gateway import JavaGateway
class Addition(object):
def doOperation(self, i, j, k = None):
if k == None:
return i + j
else:
return i + j + k
class Java:
implements = ['py4j.examples.Operator']
if __name__ == '__main__':
gateway = JavaGateway(start_callback_server=True)
operator = Addition()
numbers = gateway.entry_point.randomBinaryOperator(operator)
print(numbers)
numbers = gateway.entry_point.randomTernaryOperator(operator)
print(numbers)
gateway.shutdown()
As I mentioned, I'm getting this exception
py4j.protocol.Py4JNetworkError: An error occurred while trying to start the callback server.
This is the stack trace:
Traceback (most recent call last):
File "/home/amir/Python code/callback_example.py", line 14, in <module>
gateway = JavaGateway(start_callback_server=True)
File "/usr/local/lib/python2.7/dist-packages/py4j-0.8.2.1-py2.7.egg/py4j/java_gateway.py", line 851, in __init__
self._start_callback_server(python_proxy_port)
File "/usr/local/lib/python2.7/dist-packages/py4j-0.8.2.1-py2.7.egg/py4j/java_gateway.py", line 867, in _start_callback_server
self._callback_server.start()
File "/usr/local/lib/python2.7/dist-packages/py4j-0.8.2.1-py2.7.egg/py4j/java_gateway.py", line 1091, in start
raise Py4JNetworkError(msg)
py4j.protocol.Py4JNetworkError: An error occurred while trying to start the callback server
[Finished in 0.5s with exit code 1]

I found out what was the problem.
When I'm using Sublime Text to run the Python script and when the build was complete the process that uses the port (25334 in this case) was still running so the port was in use when I tried to run the script again.
Thanks anyway.

For me I got this error when I had a window open running the script in interactive mode (code.interact(local=locals())), forgot about this, and tried running the script again in a separate command window.

Checksum issue CRC16CCITT

I have the following C-code which I am trying to re-write in java.
I would like to see similar outputs in both of them but I am getting different outputs.
This is for computation of checksum.
Here is the C-code:
#include <ctype.h>
#include <string.h>
#include <stdio.h>
/*~+:CRC Table*/
static unsigned short crctab[256] =
{
0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7,
0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF,
0x1231, 0x0210, 0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6,
0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE,
0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485,
0xA56A, 0xB54B, 0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D,
0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4,
0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC,
0x48C4, 0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823,
0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B,
0x5AF5, 0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12,
0xDBFD, 0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A,
0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41,
0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49,
0x7E97, 0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70,
0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78,
0x9188, 0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F,
0x1080, 0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067,
0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E,
0x02B1, 0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256,
0xB5EA, 0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D,
0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E, 0xC71D, 0xD73C,
0x26D3, 0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634,
0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB,
0x5844, 0x4865, 0x7806, 0x6827, 0x18C0, 0x08E1, 0x3882, 0x28A3,
0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A,
0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92,
0xFD2E, 0xED0F, 0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9,
0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1,
0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8,
0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0
};
void convert_toASCII (char *buffer, int value)
{
/*
Function converts given 'value' into a 4 byte
ASCII-HEX-String (with leading zeros) to 'buffer[]'
Parameter: char *buffer, int value
Returns: none
*/
static unsigned char hex_num[] = "0123456789ABCDEF";
static unsigned char i; /* HV */
i = (char)((value & 0xf000) >> 12);
*buffer = (char)(hex_num[i]);
++buffer;
i = (char)((value & 0x0f00) >> 8);
*buffer = (char)(hex_num[i]);
++buffer;
i = (char)((value & 0x00f0) >> 4);
*buffer = (char)(hex_num[i]);
++buffer;
i = (char)(value & 0x000f);
*buffer = (char)(hex_num[i]);
}
void calc_crc(unsigned char *databuffer,unsigned int length)
{
/*~+:Modulname: calc_crc */
/*~+:Calculate serial CRC (according CCITT ) */
/*~+:The serial CRC16 is calculated for a certain length (int length) */
/*~+:over bytes in buffer (char databuffer[]) */
/*~+: */
/*~+:Input: *databuffer pointer to data string */
/*~+: laenge number of chars to build CRC for */
/*~+:Output: the CRC will be added in ASCII characters ( 4 chars) */
/*~+: at the end of the given string and terminated with '\0' */
/*~+: The buffer must be able to handle these additional */
/*~+: 5 characters */
static unsigned char tmp;
static unsigned int crc,zaehler;
crc = 0;
for (zaehler = 0;zaehler < length ;zaehler ++)
{
tmp=(unsigned char) (crc>>8) ;
crc=(crc<<8) ^ crctab[tmp] ^ *databuffer;
databuffer++;
}
printf("%u", crc);
/* convert crc -> ASCII */
/* append to string */
convert_toASCII (databuffer, crc);
}
void main(void)
{
static char Data[] = {"abcdefghij"};
static char buffer[64];
strcpy(buffer,Datensatz);
printf("Data : %s \n\r",&buffer[0]);
calc_crc(buffer,10);
printf("CRC : %s \n\r",&buffer[10]);
printf("Data mit CRC: %s \n\r",&buffer[0]);
}
The java code that I have written is:
public final class Checksum
{
public static void main(final String[] args)
{
final String checksumString = "abcdefghij";
final int checksum = calculateCRC16CCITTChecksum(checksumString);
System.out.println("Checksum integer value:" + checksum);
System.out.println("Checksum value in Hex:" + Integer.toHexString(checksum));
}
/**
* #param frame The frame for whose checksum has to be calculated.
* #return The calculated checksum.
*/
private final static int calculateCRC16CCITTChecksum(final String frame)
{
final int[] CRC16_Lookup = {0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7, 0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF, 0x1231, 0x0210, 0x3273, 0x2252,
0x52B5, 0x4294, 0x72F7, 0x62D6, 0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE, 0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485, 0xA56A, 0xB54B, 0x8528,
0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D, 0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4, 0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC, 0x48C4, 0x58E5,
0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823, 0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B, 0x5AF5, 0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12, 0xDBFD,
0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A, 0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41, 0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49,
0x7E97, 0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70, 0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78, 0x9188, 0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E,
0xE16F, 0x1080, 0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067, 0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E, 0x02B1, 0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214,
0x6277, 0x7256, 0xB5EA, 0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D, 0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405, 0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F,
0xF77E, 0xC71D, 0xD73C, 0x26D3, 0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634, 0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB, 0x5844, 0x4865, 0x7806, 0x6827,
0x18C0, 0x08E1, 0x3882, 0x28A3, 0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A, 0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92, 0xFD2E, 0xED0F, 0xDD6C,
0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9, 0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1, 0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8, 0x6E17, 0x7E36,
0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0};
// check sum for polynomial 1.x16 + 0.x15 + 0.x14 + 0.x13 + 1.x12 + 0.x11 + 0.x10 + 0.x9 + 0.x8 + 0.x7 + 0.x6 + 1.x5 + 0.x4 + 0.x3 + 0.x2 +0.x1 + 1.x0.
// 1.x16 - implies 1 multiplied by 'x' to the power of 16.
int crc = 0;
for (int i = 0, size = frame.length(); i < size; i++)
{
crc = (crc << 8) ^ CRC16_Lookup[(crc >> 8) & 0xFF] ^ (frame.charAt(i) & 0xFF);
}
return crc & 0xFFFF;
}
}
The integer value output that I get in java code is different from what the decimal value that I get in C, even the hex string conversion in java yields different results to that of hex conversion in C.
Please guide me what I am doing wrong.
Thanks for looking!!

This is not strictly related to an implementation problem, but I guess it's worth mentioning anyway. Keep in mind that some communication protocols require XORing the input values and output values with some value, not to mention bit or byte reflecting of the input data. This happens in Ethernet, which uses CRC-32 for the actual calculations, but the input and output data is XORed with FF..FF (so, it's NOTed), and all the bits in the input byte (or, more naturally, nibble) are reflected. Keep that in mind - the actual calculations might be alright, but there might be something you're simply not aware of in terms of mangling the data, what leads to completely different results.

By code inspection, one can see that in Java the CRC is limited to 16 bits before being printed in decimal (use of & 0xFFFF before returning the function). In C, the value printed is the full unsigned int, so applying the same mask should do the trick.
I can't understand why the hex values differ, though...