Find and Replace in Binary File

[mouac01]

Newbie here. How do I do a find and replace in a binary file? I need
to read in a binary file then replace a string "ABC" with another
string "XYZ" then write to a new file. Find string is the same length
as Replace string. Here's what I have so far. I spent many hours
googling for sample code but couldn't find much. Thanks...

public static void FindReplace(string OldFile, string NewFile)
{
string sFind = "ABC"; //I probably need to convert these
to a byte array
string sReplace = "XYZ"; //but I don't know how.
int i;
FileStream fin = new FileStream(OldFile, FileMode.Open);
FileStream fout = new FileStream(NewFile,
FileMode.Create);
do
{
i = fin.ReadByte();
if (i != -1)
{
//I think I need to compare the byte being read in
//to the 1st sFind byte array here. If it matches
then
//store the position and compare the next byte.
//If all 3 bytes match then replace with sReplace
byte array.
//I'm just not sure how to do it.
fout.WriteByte((byte)i);
}
} while (i != -1);
fin.Close();
fout.Close();
}

[Mufaka]

I have done this before. The approach I took was to read the file bytes
into memory (because the files I was working with were small), move the
file out of the way, and then write a new file replacing the "find"
bytes with the "replace" bytes. So similar to your approach.

Here's a snippet from what I wrote (it was in 1.1 and was just "quick
and dirty" code):

ArrayList newBytes = new ArrayList(bytes.Length);
int ndx = 0;

for (int x = 0; x < bytes.Length; x++) // bytes is the original files bytes
{
if (bytes[x] == findBytes[ndx]) // findBytes is a byte[] from the
"find" string
{
if (ndx == findBytes.Length - 1)
{
for (int y = 0; y < replaceBytes.Length; y++) //
replaceBytes is a byte[] from the "replace" string
{
newBytes.Add(replaceBytes[y]);
}
ndx = 0;
}
else
{
ndx++;
}
}
else
{
if (ndx 0)
{
for (int y = 0; y < ndx; y++)
{
newBytes.Add(findBytes[y]);
}
}
ndx = 0;
newBytes.Add(bytes[x]);
}
}

ndx is used to keep track of which byte in the findBytes should be
compared to the original files byte.

mo*****@yahoo.com wrote:

Newbie here. How do I do a find and replace in a binary file? I need
to read in a binary file then replace a string "ABC" with another
string "XYZ" then write to a new file. Find string is the same length
as Replace string. Here's what I have so far. I spent many hours
googling for sample code but couldn't find much. Thanks...

public static void FindReplace(string OldFile, string NewFile)
{
string sFind = "ABC"; //I probably need to convert these
to a byte array
string sReplace = "XYZ"; //but I don't know how.
int i;
FileStream fin = new FileStream(OldFile, FileMode.Open);
FileStream fout = new FileStream(NewFile,
FileMode.Create);
do
{
i = fin.ReadByte();
if (i != -1)
{
//I think I need to compare the byte being read in
//to the 1st sFind byte array here. If it matches
then
//store the position and compare the next byte.
//If all 3 bytes match then replace with sReplace
byte array.
//I'm just not sure how to do it.
fout.WriteByte((byte)i);
}
} while (i != -1);
fin.Close();
fout.Close();
}

[mouac01]

Thanks for all your comments. Here's what I'm trying to mimic in
VB6. I guess .NET is more restrictive in what type of file you can do
find/replace. Sounds too difficult in C# so I might just have to
revert back to VB6 for this one. Thanks...

Sub FindRplace()
Dim sBuffer As String
Dim ff As Integer
ff = FreeFile
Open txtFile.Text For Binary As #ff
sBuffer = Space$(LOF(ff))
Get #ff, 1, sBuffer
Close #ff
sBuffer = Replace(sBuffer, "ABC", "XYZ")
Open txtNew.Text For Binary As #ff
Put #ff, , sBuffer
Close #ff
End Sub

[Peter Duniho]

On Mon, 25 Feb 2008 11:56:50 -0800, <mo*****@yahoo.comwrote:

Thanks for all your comments. Here's what I'm trying to mimic in
VB6. I guess .NET is more restrictive in what type of file you can do
find/replace. Sounds too difficult in C# so I might just have to
revert back to VB6 for this one.

It's not difficult in C#. The code would not even be significantly
different from the VB6 code you posted, other than the lack of a
short-hand "replace" feature for dealing with byte arrays (which you
should be able to easily write yourself). And your VB6 code has all the
same problems we've warned that could come up doing it in C#.

But if you've already got VB6 code to do what you want, maybe you should
just stick with that if you'd rather not use the suggestions offered here.

Pete