If you're in .NET 4.0 land then I'd do something similar to this:
public string ReplaceTokens(string src) { /* ... */ }
File.WriteAllLines(outputFileName,
File.ReadLines(inputFileName).Select(ReplaceTokens));
The ReadLines call (new to .NET 4.0) reads one line at a time and returns it
as you iterate over it so in theory you don't need to have the whole file in
memory. Don't use the ReadAllLines method on a 750MB file which DOES read
the whole thing in before you start.
--
Michael M. Minutillo
Indiscriminate Information Sponge
Blog: http://wolfbyte-net.blogspot.com
On Mon, Feb 7, 2011 at 7:58 AM, Grant Molloy <[email protected]> wrote:
> Bec,
>
> Read this article and download the demo..
> It goes through several different options for "find and replace" in large
> text strings..
>
> http://www.codeproject.com/KB/string/fastestcscaseinsstringrep.aspx
>
> Grant
>
>
> On Mon, Feb 7, 2011 at 9:43 AM, Bec Carter <[email protected]> wrote:
>
>> On Mon, Feb 7, 2011 at 10:35 AM, Noon Silk <[email protected]> wrote:
>> > On Mon, Feb 7, 2011 at 10:29 AM, Bec Carter <[email protected]>
>> wrote:
>> >> On Mon, Feb 7, 2011 at 10:25 AM, Noon Silk <[email protected]>
>> wrote:
>> >>> On Mon, Feb 7, 2011 at 10:21 AM, Bec Carter <[email protected]>
>> wrote:
>> >>>> Good mornin' all!
>> >>>>
>> >>>> I've a requirement to put certain values (after computing them) in
>> >>>> various spots in a very large text file. So basically the starting
>> >>>> text file can have placeholders where these computed values will end
>> >>>> up- like a template. Then my code will compute some values based on
>> >>>> user input and i need to fill in the placeholders.
>> >>>>
>> >>>> Is there a better way to do this besides a simple string replace?
>> >>>
>> >>> Well, no. You'll need to read the file in and find your tokens and
>> >>> replace them. Depending on how large the file it, you might need to do
>> >>> this line by line, or chunk by chunk, writing out as you read in, but
>> >>> inevitably it comes down to looking for a sequence and replacing it
>> >>> with another.
>> >>>
>> >>> How large is "very large"? Megs? Gigs?
>> >>>
>> >>
>> >> Yup reading all into a string right now and replacing. File is around
>> 750 megs
>> >
>> > Mm, in that case I would definitely think reading in chunk by chunk
>> > would be better.
>> >
>> > So, you read in chunks of chars in a char[], and then you must look
>> > for the start of your token. Taking care to note that you could end up
>> > in the middle of your token, something like:
>> >
>> > // Pseudocode
>> > char[] data = { "$te" }
>> > char[] nextData = { "st$" }
>> >
>> > Where the token is "$test$".
>> >
>> > Depending on your data, it might be that reading lines is enough, and
>> > do the replace on that basis. Hopefully this is somewhat clear. I had
>> > a quick search and couldn't find a nice example on doing this, but it
>> > should be easy enough using StreamReader or friends. If it's not clear
>> > I can show an example later on.
>> >
>>
>> That's fine thanks. Line by line would be ok as the data will never be
>> broken up and flow onto the next line.
>>
>> I was kinda hoping there'd be something specifically built for this-
>> seems like I'm creating mail merge all over again :-)
>>
>> > --
>> > Noon Silk
>> >
>> > http://dnoondt.wordpress.com/ (Noon Silk) |
>> http://www.mirios.com.au:8081 >
>> >
>> > Fancy a quantum lunch?
>> > http://www.mirios.com.au:8081/index.php?title=Quantum_Lunch
>> >
>> > "Every morning when I wake up, I experience an exquisite joy — the joy
>> > of being this signature."
>> >
>>
>
>
