[C#} Loop byte by byte comparing short value

Jay S

I am trying to loop through some bytes using the binaryreader class, I want to compare a short value to each short value, but rather than moving 2 bytes within the stream, move 1 byte and re-compare the short value.

As it stands I can currently compare byte for byte:

byte b0 = (byte)num9; //get single byte value from volume. num9 = short

//loop through remaining bytes until we find value *should* be the only occurance eek.

{

binaryReader.ReadByte();

}

while (binaryReader.ReadByte() != b0);

While this kinda works it doesn't always return what I expect. If I use binaryReader.ReadInt16() then I will miss possible matches.

Ideally I dont want to read the bytes into the array,find the index and move the base stream position...I really want to check each possible short value in the remaining bytes...

The way I see it is something like this (on the basis that a short is 2 bytes):

byte1
byte2
byte3
byte4
byte5

[byte1, byte2]...[byte2, byte3]...[byte3, byte4]...[byte4, byte5]

Any help would be great..I just can't seem to visualise what to do.

3 Replies

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Vulpes12y ago
Yes, you'll need to use:

if (s == value) break;

to exit the while loop when the first match is detected.

The BaseStream position will then, of course, be on the second byte of the short.
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Jay S12y ago
This does look like what I need, but I want the loop to stop when it finds the first match so my base stream position is there?

EDIT:

I ended up using a break; as part of the If statement...not sure if this is the most efficent way..
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Vulpes12y ago
This code should work.

When you say 'short' I assume you mean a signed 2 byte integer and not a 'ushort':

using System;
using System.Collections.Generic;
using System.IO;

class Program
{
static void Main()
{
List matches = new List();
short s = 16000; // or whatever
long index = 0;

using(FileStream fs = new FileStream("jay.bin", FileMode.Open))
{
using(BinaryReader br = new BinaryReader(fs))
{
long len = br.BaseStream.Length;
byte first = br.ReadByte();

while(br.BaseStream.Position < len)
{
byte second = br.ReadByte();
byte[] temp = {first, second};
short value = BitConverter.ToInt16(temp, 0);
if (s == value) matches.Add(index);
first = second;
index++;
}
}
}

if (matches.Count == 0)
{
Console.WriteLine("No matches were found");
}
else
{
Console.WriteLine("Matches were found of the bytes at the following indices");
foreach(long m in matches) Console.WriteLine("{0} : {1}", m, m +1);
}

Console.ReadKey();
}
}

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