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Top Forums Shell Programming and Scripting Extract sequences of bytes from binary for differents blocks Post 302843978 by ahamed101 on Friday 16th of August 2013 02:14:41 AM
Old 08-16-2013
Code:
#include <stdio.h>
#include <stdlib.h>

#define err(x) {printf("\nError: %s... Exiting...\n", x); exit(1);}

static unsigned char pat1[] = {0x99, 0x11, 0x45, 0x27};
static unsigned char pat2[] = {0x73, 0x49};
static unsigned char pat3[] = {0xff, 0x34};
static unsigned char intrim_pat1[][2] = { {0x03, 0x80}, {0x03, 0x81}, {0x03, 0x83}, {0x03, 0x86}, {0x03, 0x87} };
static unsigned char end[] = {0xff, 0x33};

void print_data(const unsigned char *ptr, int len)
{
        int i;
        for(i=0;i<=len;i++)
                printf("%02x ", ptr[i]);
        printf("\n");
        return;
}

int main(int argc, char **argv)
{
        if(argc < 2)
                err("File name missing");

        char found = 0, more = 0;
        unsigned char buf[32];
        unsigned char *ptr = buf;
        int pos = 0, i;
        int arr_size = (sizeof(intrim_pat1)/2);

        FILE *fp = fopen(argv[1], "rb");
        if(!fp) err("Unable to open the file");

        while(2 == fread(ptr, sizeof(char), 2, fp)){
                pos = ftell(fp);

                //check for end of file pattern
                if(found && !memcmp(buf, end, 2)){
                        found=0; //start over or stop??
                        continue;
                }

                //check for 0xff 0x34
                if(found && !(memcmp(buf, pat3, 2))){
                        more = 1;
                        continue;
                }

                if(found && more){
                        for(i=0; i< arr_size; i++){
                                if(!memcmp(buf, intrim_pat1[i], 2)){
                                        if(15 != fread(ptr+2, sizeof(char), 15, fp))
                                                err("Insufficient data");
                                        print_data(ptr, 16);
                                        more=0;
                                        continue;// start with the next byte
                                }
                        }
                }

                if(buf[0] == 0x32){
                        if(18 != fread(ptr+2, sizeof(char), 18, fp))
                                err("Insufficient data");
                        if(memcmp(buf+4, pat1, 4) && memcmp(buf+12, pat2, 2)){
                                fseek(fp, pos, SEEK_SET);
                        }else{
                                found = 1; //found the starting of the block with data
                                print_data(ptr, 19);
                        }
                        continue;
                }
                pos--;
                if(fseek(fp, pos, SEEK_SET))
                        err("Error in seeking");
        }

        return 0;
}

--ahamed

Last edited by ahamed101; 08-16-2013 at 03:24 AM..
 

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POSIX_FALLOCATE(3)					     Linux Programmer's Manual						POSIX_FALLOCATE(3)

NAME
posix_fallocate - allocate file space SYNOPSIS
#define _XOPEN_SOURCE 600 #include <fcntl.h> int posix_fallocate(int fd, off_t offset, off_t len); DESCRIPTION
The function posix_fallocate() ensures that disk space is allocated for the file referred to by the descriptor fd for the bytes in the range starting at offset and continuing for len bytes. After a successful call to posix_fallocate(), subsequent writes to bytes in the specified range are guaranteed not to fail because of lack of disk space. If the size of the file is less than offset+len, then the file is increased to this size; otherwise the file size is left unchanged. RETURN VALUE
posix_fallocate() returns zero on success, or an error number on failure. Note that errno is not set. ERRORS
EBADF fd is not a valid file descriptor, or is not opened for writing. EFBIG offset+len exceeds the maximum file size. EINVAL offset was less than 0, or len was less than or equal to 0. ENODEV fd does not refer to a regular file. ENOSPC There is not enough space left on the device containing the file referred to by fd. ESPIPE fd refers to a pipe of file descriptor. VERSIONS
posix_fallocate() is available since glibc 2.1.94. CONFORMING TO
POSIX.1-2001. POSIX.1-2008 says that an implementation shall give the EINVAL error if len was 0, or offset was less than 0. POSIX.1-2001 says that an implementation shall give the EINVAL error if len is less than 0, or offset was less than 0, and may give the error if len equals zero. SEE ALSO
fallocate(2), lseek(2), posix_fadvise(2), feature_test_macros(7) COLOPHON
This page is part of release 3.25 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. GNU
2009-09-30 POSIX_FALLOCATE(3)
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