TIP 1: Index Lines In Large Text File For Fast Random Access?
Jul 14, 2011
When you need to do random access to the lines of a text file, the regular solution is to put those lines in a list and access them in that list.But doing this if the text file is large creates a large memory overhead and may cause some memory stress on the application.This class maps the file and provide the ability to read any particular line in the file at a random position, without the need to read or put in memory any other line but the desired line. The only memory overhead involve is the 1024 bytes buffer of the base stream.Even if the file mapping can be a process that consume a noticable amount of time if the file is very large ( ~ 5 seconds for each 100,000,000 caracteres) , once the mapping is done the access to a particular line becomes instantaneous regardless of the size of the file. (The file mapping can always be done at a convenient time (ex when the process load) and can be done on a worker thread The class is base on a StreamReader to support the differents Text Encodings Example uf usage ( As I say, if the file is very large, dont do it like that, but declare the class at a convenient time)
Imports Reader = System.IO.MyStreams
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
[code]....
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Jan 31, 2010
basically ive tried a few different methods which i have come accross by searching but none seem to work.
code so far after removing everything that didnt work is as follows
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
End Sub
End Class
im makng a spelling test type application so that each word is on a different line and that are displayed in a random sequency.
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Jan 15, 2012
Im making a text based game that i need to randomly select different numbers of lines from a text file then pass them to a list box.[code]...
First the code needes to identify the 4th element then randomly select lines from lines that contain that element. The code needs to work out how many lines have a matching text to the 4th array then randomly select lines from that total no need for a maximum limit to that number.The same line must only been show the once at a time, but It can then be shown again on a different button click.[code]...
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Jan 12, 2012
Im making a text based game that i need to randomly select different numbers of lines from a text file then pass them to a list box. The text file is made in the following format:
20058,v,o,ED,95
20059,v,o,TI,95
20060,v,o,TI,95
20061,v,o,SL,95
First the code needes to identify the 4th element then randomly select lines from lines that contain that element. Im stuck on how to randomly select lines from that list.This is the code i have so far.
[Code]...
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Apr 25, 2010
I'm doing a Program for a Friend of mine, He Want to have a Console Program Running on his Computer.OK the problem i am having is With Stream Read, I have 3 test users inside Test File, if User 1 logs in his information is store in logged file with time and data.but if User 3 logs on user 1 2 and 3 are all saved on the logged file
i dont have read to end of file in my Code.i dont have my Program with me, so i going off the top of my head i have something like this what i want to be able to find out how to do is Right from any part of the file and out put it, I take it i need to use Random Access but how to i code Random Access for this type of file. All i can find is how to Randomly place Words in a text file with Length and size.
[Code]...
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Jan 7, 2009
I am writing a program to calculate Pi to several hundred billion decimal places and this will require lots of GB of memory. I wrote a test program in VB2008 that saved the first 16 digits of Pi (without the decimal point) to both a text file and a random access file, just to be sure it was outputting the numbers properly. For reference the first 16 digits of Pi are:
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Jan 12, 2010
how to proceed. One of our customers is going to be sending me a flat file (ASCII-Text) that I have to break down and scan. Every line ends in a CrLf - So I know I can use StreamReader and ReadLine(). I did get it to work on one of the test files they sent.(A very Short file) However, the file is not delimited at all and every field is padded to the full length they specified. Here's the format of the file:
[Code]....
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Nov 18, 2011
I had tested this code: [URL] It works, but a Word application is opened and each new paragraph added using VB code is seen one by one(with a small delay). If I want to open and write something using VB, what is the fastest way ? I do not want to view the changes made on word document live. I want to save the document. So will oWord.Visible = False makes it fast?
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Jan 16, 2010
I have this:
vb.net
Private Sub doWork_Tick(ByVal sender As Object, ByVal e As System.EventArgs) Handles doWork.Tick
Me.doWork.Stop()
For outer As Integer = 0 To Me.queriedDGV.Rows.Count - 1
For inner As Integer = 0 To Me.hebdataDGV.Rows.Count - 1
Application.DoEvents()
[Code] .....
It works fine when I step through it with F8, but when running normally, I guess it's going so fast that I get an Index out of range when the outer For loop increments to the second iteration. I tried putting a timer in there to give it a chance to update the UI, but that didn't work. I also tried "Application.DoEvents" as a last resort, and that didn't work either.
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Feb 5, 2009
I have a coma separated text file with loads of records. Usually when we read a text file we start from the first line and go towards the last. I know that there will be x comas per record.But I want to start reading from the last line and then towards the top. This enables me to stop before I reach the top (depending on the data).
What would be the fastest way to read a text file in VB.NET?. I am using VS2008. Basically I want to read from last line and go upwards and stop when I want. I may not need to read the entire file.
[Note: I want to store data in an array and not show it in some textbox]
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Jun 22, 2010
I have written a simple script to get a bunch of lines from a text file (they will be filenames eventually) which are split by new lines and puts each one into an array..
Dim ary() As String
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
If My.Computer.FileSystem.FileExists("C:MenuFiles.txt") Then
[code]....
The only thing I can do for now is either use the substring function to remove the first character from all array values after 0 but I don't like that because it's messy and what if the split "works" as I want it to one one of the lines and knocks of the first character when I don't want it to.
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Sep 15, 2009
I have a text file containing lines of data (File 1). I need to delete all the lines in another text file (File 2), which are found in file 1.So I could read file 2 line by line. And then once the line has been read, read file 1 line by line to search for a match. But that's going to be painfully slow.Or I could read file 2 into memory. And then read file 1 line by line and REPLACE the lines in file 2 with nothing, therefore deleting them. File 2 could be 100 mb, so I'm not sure about reading it all into memory.
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Feb 17, 2011
Say I want to remove all lines that contain "hello". One way to do it is to read the whole files into memory and then operate. Often my files are big, 500MB. If I load them I got no memory. Will upgrading to a 64 bit computer helps? I have a big page file. Also I wonder how in the earth windows 7 and xp 32 bits can have very large page files anyway.
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May 12, 2009
i have 5 textboxes in a form. I have a streamwriter that writes all of their text to on text file like this:
Code:
Dim xfile As String = Application.StartupPath & "/Set.txt"
If File.Exists(xfile) = True Then
Dim writex As StreamWriter = New StreamWriter(xfile)
[code]....
I was wondering how to get the text under the each number and place it in the corresponding textbox.
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Oct 19, 2011
Years ago when coding with VB6 and earlier, I used a file open command to create, read, and write a file that made it easy to store useful information.I believe it was binary and you wrote/read the data to a specific line in the file. When you opened the file with something like notepad, it just showed random ascii chars. When I needed a line of data, I could specify what line to load it from.
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Jan 30, 2012
My problem is I have very large text files (approx 2GBs+).They have records in them based in one per line.Each line is not the same length and the data can be different lengths all the time.I am currently reading the file line by line, then splitting the data by common characters in the records. To process the full file it currently takes 3hours. This is way too slow for its purpose.
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Jul 6, 2011
I've a problem reading text file using StreamReader. The file have between 500 000 and 1 000 000 lines.When I try to read it in a cycle, I get an error. That's why I've tried the StreamReader.ReadToEnd method. It worked fine. I've get the entire contents of the file in one string. So far everything is okay, but I've a small problem searching this huge string. I have to reformat the string to my desired format. I'll try to be more specific: The format of the input file is as follows:
50471100 8 2 6 5 0<LF><CR>
00000016 365442 12231<LF><CR>
00000026 112166 31133<LF><CR>
<end>
[Code]...
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Jan 4, 2012
I want to read each line from a txt file, but instead of using a for, while etc loop i will let the web browser do it (document completed). I want to increment the next line and let the loop continue till its finished.
Just say the data was inside a textbox, i'd do Textbox1.Lines(count) for line one, then i'd do count += 1 and when the web browser has completed, it would start again and repeat the process.
So how do i read the lines from a txt file into an array without looping? And allows me to specify the line number?
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Dec 10, 2011
I am faced with a rather large text file (200-400 lines)The file displays a lot of data however the problem is that it is not lined up. The data at the moment resembles this
Column1 Column2 Column3 Column4
Bobby Fisher Virginia Rural
Willis Johnson Oklahoma City
[code].....
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Apr 3, 2010
How to Use of Backgroundworker while open a large text file
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Feb 1, 2009
The following code suppose to:
1. Read line-by-line a txt file with more than 500,000 lines, (each line 521 characters long)
2. extract an ID No from the line
3. query from a database for LCCIStatus
4. concatenate the value of LCCIStatus to the line
5. write the line to sample.txt
My problem is, this code works perfectly with the test file of 8000 lines but fail with the actual files which have over 500,000 lines. FYI, the test file contains data which I cut and paste from the actual file.
[Code]...
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Jul 1, 2010
I need an example of how to create and use a random access file
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May 20, 2010
Created Structure
opened file using FileOpen(1, "filename.dat", OpenMode.Random, , , bytes in structure)
used structure .ID = record number
FilePut(1, structure)
FileClose(1)
The program enters the first record but although when I enter more records it still shows only one record in the file.
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Jan 15, 2010
I am moving all of the prgrams that I have written, to VS2008. However, I use Random Access File Foemat for the databases that have been used for over a decade. I need to be able to read and write to a Random access file.I have multiple fields in the database and cannot lose access to this information.VS2008 doesn't use the following type of code to define the Fields that will be used in the Database. I did what it suggested, using the Structure / End Structure, but that was as close to a solution that I could find in the Help Files.
Type EquipType
EquipName As String * 32
Location As String * 28[code].......
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Jun 23, 2011
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
FileNum = FreeFile()
[Code].....
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Mar 2, 2010
I achieved reading and writing data to a random access file, buthow do I write and read data from a certain position in the *.txtfile? Would it be better if I created multiple file modes to
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Oct 6, 2010
Currently we have a large DataTable (~152k rows) and are doing a for each over this to find a sub set of distinct entries (~124K rows). This is currently taking about 14 minutes to run which is just far too long.
As we are stuck in .NET 2.0 as our reporting won't work with VS 2008+ I can't use linq, though I don't know if this will be any faster in fairness.
Is there a better way to find the distinct lines (invoice numbers in this case) other than this for each loop?[code]....
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Feb 28, 2012
Some of my users are collecting data files this size and wish to load it in to my tool. Is there a way to load large files of string data w/o getting a OutOfMemoryException? I have tried many different storage methods (Array, List, etc) but always without success.Before anyone asks 'why load it all at once', let me say the nature of my app is speed critical and it must be so.
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Jan 8, 2010
If there is any way to open large rtf files in rich text text box ?when i try to open a large rtf file in rich text box it halt the system unlike windows word pad . win word pad open file smoothly may be read line by line how it possible in vb.net?
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Feb 22, 2009
I am trying to parse a very large text file for certain strings. The text file is part of a level-making software for an old game I play. The text file basically contains all the information the level designer software needs, but the only important bit is the 'texture information'. Basically what I'm trying to create is a little program that parses the text files and shows the user a list of every texture in that text file. The problem is, the strings denoting textures are not really easy to find, and I can't think of any sensible and fast way to get them...
[Code]...
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