Binary files in java

hi
I am a bit new to java and am having some problems with binary files. What I need to do is search a binary file for any accurances of the data contained with in another set of binary files. I need to know if the first file contains any of the signatures in the set of files. any help would be great.
thanks very much
Colin

you take your file, you read in some bytes and you loop thru those bytes to find matching bytes that you are looking for. Here's some cdoe that's probably not as elegant as it could be, but you get what you pay for.
public static int indexOf(byte[] a, byte[] b) {
   return indexOf(a, b, 0);
public static int indexOf(byte[] a, byte[] b, int start) {
   if(a == null || b == null || a.length == 0 || b.length == 0 || a.length < b.length) {
      return -1;
outer:   for(int i = start; i < a.length-b.length; i++) {
      if(a[i] == b[0]) {
         for(int j = 0; j < b.length; j++) {
            if(a[i+j] != b[j]) {
               break outer;
         return i;
}

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Read binary file in java

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Thanks in advance!
Edited by: nikkj on Aug 7, 2010 7:36 PM

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DE PDP-1 binary file from Java

Can someone here help me, please!?
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This resurrected thread was first posted November 25, 1960 at 8:25AM
-------------------------------------------------------------------------

This resurrected thread was first posted November 25,
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Hey,
I need to recieve files from java Webdynpro and save them as a file on the backend
system. After that, the file will be loaded to the documentum.
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JNI Invocation: open file in Java, write file in CPP

Hello,
Warning: I am a dunce, bad CPP code ahead!
Using JNI invocation, I am trying to read a binary file in Java and write it in CPP.
Everything compiles and runs without error, but the input and output jpg files are of course different.
TIA to any help,
kirst
(begin ByteMe.java)
import java.io.*;
public class ByteMe
    // Returns the contents of the file in a byte array.
    public byte[] getBytesFromFile(String strInfo) throws IOException
        System.out.println("Testing:" + strInfo);
        File file = new File("1.jpg");
        InputStream is = new FileInputStream(file);
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        long length = file.length();
        // Create the byte array to hold the data
        byte[] bytes = new byte[(int)length];
        // Read in the bytes
        int offset = 0;
        int numRead = 0;
        while (offset < bytes.length
               && (numRead=is.read(bytes, offset, bytes.length-offset)) >= 0) {
            offset += numRead;
        // Ensure all the bytes have been read in
        if (offset < bytes.length)
            throw new IOException("Could not completely read file "+file.getName());
        // Close the input stream and return bytes
        is.close();
        return bytes;
    public ByteMe()
          //System.out.println("in constructor");
}(end ByteMe.java)
(begin ByteMe.cpp)
#include <stdlib.h>
#include <string.h>
#include <jni.h>
#include <windows.h>
// for file operations:
#include <fstream>
int main( int argc, char *argv[] )
     JNIEnv *env;
     JavaVM *jvm;
     JavaVMInitArgs vm_args;
     JavaVMOption options[5];
     jint res;
     jclass cls;
     jmethodID mid;
     jstring jstr;
     jobject obj_print;
     options[0].optionString = "-Xms4M";
     options[1].optionString = "-Xmx64M";
     options[2].optionString = "-Xss512K";
     options[3].optionString = "-Xoss400K";
     options[4].optionString = "-Djava.class.path=.";
     vm_args.version = JNI_VERSION_1_4;
     vm_args.options = options;
     vm_args.nOptions = 5;
     vm_args.ignoreUnrecognized = JNI_FALSE;
     // Create the Java VM
     res = JNI_CreateJavaVM(&jvm,(void**)&env,&vm_args);
     if (res < 0)
          printf("Can't create Java VM");
          goto destroy;
     cls = env->FindClass("ByteMe");
     if (cls == 0)
          printf("Can't find ByteMe class");
          goto destroy;
     jmethodID id_construct = env->GetMethodID(cls,"<init>","()V");
     jstr = env->NewStringUTF(" from C++\n");
     obj_print = env->NewObject(cls,id_construct);
     // signature obtained using javap -s -p ByteMe
     mid = env->GetMethodID(cls, "getBytesFromFile", "(Ljava/lang/String;)[B");
     if (mid == 0)
          printf("Can't find ByteMe.getBytesFromFile\n");
          goto destroy;
     else
          jbyteArray jbuf = (jbyteArray) env->CallObjectMethod(obj_print,mid,jstr);
          jlong size = jsize(jbuf);
          printf("size is: %d\n", size); // size shown in output is
          std::ofstream out("data.jpg", std::ios::binary);
          out.write ((const char *)jbuf, 100000);
     destroy:
         if (env->ExceptionOccurred())
            env->ExceptionDescribe();
    jvm->DestroyJavaVM();
}(end ByteMe.cpp)

Hello,
Me again. Well, not such a dunce after all. Here is code that works correctly, and compiles with no errors and no warnings.
Will much appreciate help with clean-up code.
TIA,
kirst
(begin ByteMe.java)
import java.io.*;
public class ByteMe
    public long getFilezize(String strInfo) throws IOException
          // demonstrates String parameter passed from CPP to Java:
          System.out.println("(getFilesize) Hello world" + strInfo);
          File file = new File("1.bmp");
          InputStream is = new FileInputStream(file);
          // Get the size of the file
          long length = file.length();
          is.close();
          return length;
    // Returns the contents of the file in a byte array.
    public byte[] getBytesFromFile(String strInfo) throws IOException
        System.out.println("(getBytesFromFile) Hello world" + strInfo);
        File file = new File("1.bmp");
        InputStream is = new FileInputStream(file);
        // Get the size of the file
        long length = file.length();
        System.out.println("length is: " + String.valueOf(length));
        // Create the byte array to hold the data
        byte[] bytes = new byte[(int)length];
        // Read in the bytes
        int offset = 0;
        int numRead = 0;
        while (offset < bytes.length && (numRead=is.read(bytes, offset, bytes.length-offset)) >= 0)
            offset += numRead;
        // Ensure all the bytes have been read in
        if (offset < bytes.length)
            throw new IOException("Could not completely read file "+ file.getName());
        // Close the input stream and return bytes
        is.close();
        return bytes;
    public ByteMe()
          //System.out.println("in constructor");
}(end ByteMe.java)
(begin ByteMe.cpp)
          Signature obtained with command:
               "C:\Program Files\Java\jdk1.5.0_15\bin\javap.exe" -s -p ByteMe
               Compiled from "ByteMe.java"
               public class ByteMe extends java.lang.Object{
               public long getFilezize(java.lang.String)   throws java.io.IOException;
                 Signature: (Ljava/lang/String;)J
               public byte[] getBytesFromFile(java.lang.String)   throws java.io.IOException;
                 Signature: (Ljava/lang/String;)[B
               public ByteMe();
                 Signature: ()V
     Compiled VC++ 2005 Express, run on Vista
#include <stdlib.h>
#include <string.h>
#include <jni.h>
// file operations
#include <fstream>
int main( int argc, char *argv[] )
     JNIEnv *env;
     JavaVM *jvm;
     JavaVMInitArgs vm_args;
     JavaVMOption options[5];
     jint res;
     jclass cls;
     jmethodID mid;
     jmethodID sizeid;
     jstring jstr;
     jobject obj_print;
     jlong filesize;
     options[0].optionString = "-Xms4M";
     options[1].optionString = "-Xmx64M";
     options[2].optionString = "-Xss512K";
     options[3].optionString = "-Xoss400K";
     options[4].optionString = "-Djava.class.path=.";
     vm_args.version = JNI_VERSION_1_4;
     vm_args.options = options;
     vm_args.nOptions = 5;
     vm_args.ignoreUnrecognized = JNI_FALSE;
     // Create the Java VM
     res = JNI_CreateJavaVM(&jvm,(void**)&env,&vm_args);
     if (res < 0)
          printf("Can't create Java VM");
          goto destroy;
     cls = env->FindClass("ByteMe");
     if (cls == 0)
          printf("Can't find ByteMe class");
          goto destroy;
     jmethodID id_construct = env->GetMethodID(cls,"<init>","()V");
     printf("%s\n",id_construct);
     jstr = env->NewStringUTF(" from C++!\n");
     if (jstr == 0)
          // Normally not useful
          printf("Out of memory (could not instantiate new string jstr)\n");
          goto destroy;
     obj_print = env->NewObject(cls,id_construct);
     //BEGIN BLOCK to get file size
     sizeid = env->GetMethodID(cls, "getFilezize", "(Ljava/lang/String;)J");
     if (sizeid == 0)
          printf("Can't find ByteMe.getFilezize\n");
          goto destroy;
     else
          printf("got here\n");
          filesize =(jlong) env->CallObjectMethod(obj_print,sizeid,jstr);
          printf("got filesize\n");
     // END BLOCK to get file size
     // BEGIN BLOCK to write file
     mid = env->GetMethodID(cls, "getBytesFromFile", "(Ljava/lang/String;)[B");
     if (mid == 0)
          printf("Can't find ByteMe.getBytesFromFile\n");
          goto destroy;
     else
          jbyteArray ret =(jbyteArray) env->CallObjectMethod(obj_print,mid,jstr);
          // Access the bytes:
          jbyte *retdata = env->GetByteArrayElements(ret, NULL);
          // write the file
          std::ofstream out("data.bmp", std::ios::binary);
          //out.write ((const char *)retdata, 921654);
          out.write ((const char *)retdata, (long)filesize);
     // END BLOCK to write file
     destroy:
         if (env->ExceptionOccurred())
            env->ExceptionDescribe();
    jvm->DestroyJavaVM();
}(end ByteMe.cpp)

Binary file text file

I need to read binary file (actualy text file was saved in binary format) and convert to text file. After finished program, I must store this text file to binary format for use in next time. Anyone have any idea or suggestion will be usefull and great thanks

I need to read binary file (actualy text file was
saved in binary format) and convert to text file.
After finished program, I must store this text file
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any idea or suggestion will be usefull and great
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import re
dat = 'c:/projects/test.dat'
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Hi infraray.
Check my post out: Cyclomatic Complexity Using Regex .
This will help.
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.io.*;
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Hi,
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int high = data_in.readByte() & 0xff;
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Hi All,
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õgëÓÌ©ÿÿ ABC õgëÓÌ©ÿÿ
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Regards,
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paulcw wrote:
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http://www.ej-technologies.com/products/exe4j/overview.html
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http://forum.java.sun.com/thread.jspa?messageID=9455793

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