How do I read this 4 specific hex data from a file in C#?

Question

I have a corrupted *.jpg file from where I am trying to read the stored jpg. I can open the file in a Hex Editor (using http://mh-nexus.de/en/hxd/) and do copy-paste but I wanted to copy the data directly using c# instead. Can someone please help me in my quest??

Here is the exact data that I am looking for in the file: FF D8 FF DB

Example: for example

What do you want to do? Its not clear in the question, see if a file contains those bytes? Remove those bytes or substitute those bytes? Is this about removing copyright information from image files? — Jodrell, Jun 16 '15 at 13:13
@Jodrell "FF D8 FF DB" marks the start of a jpeg image block — Deb, Jun 16 '15 at 13:17
Duplicate of this ?? : http://stackoverflow.com/questions/283456/byte-array-pattern-search — PaulF, Jun 16 '15 at 13:17
So, do you want to extract everything after and including `FF D8 FF DB`? — Jodrell, Jun 16 '15 at 13:19

score 2 · Accepted Answer · edited May 23 '17 at 10:30

2

The hex files you want to find are simply bytes. use the following:

byte[] toFind = new byte[]{0xFF, 0xD8, 0xFF, 0xDB};

Read the bytes:

byte[] fileContent = File.ReadAllBytes("your file");

now search the subarray in the array:

int loc = SearchBytes(fileContent,toFind);
if (loc != -1)
{
  //BINGO!
}

This is the code for 'SearchBytes' (from here):

static int SearchBytes( byte[] haystack, byte[] needle ) 
{
    var len = needle.Length;
    var limit = haystack.Length - len;
    for( var i = 0;  i <= limit;  i++ ) 
    {
        var k = 0;
        for( ;  k < len;  k++ ) 
        {
            if( needle[k] != haystack[i+k] ) break;
        }

        if( k == len ) return i;
    }

    return -1;
}

edited May 23 '17 at 10:30

Community

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answered Jun 16 '15 at 13:18

Nissim

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Just to add, it's called a file signature @Deb. – Carl Reid Jun 16 '15 at 13:24
@Deb If the solution works for you, mark it as 'accepted' so users will know it's been answered – Nissim Jun 16 '15 at 15:08

How do I read this 4 specific hex data from a file in C#?

1 Answers1