Random File Access - Using Binary Sort Method To Find Record
Dec 24, 2011
I have a flat file that is sorted by account number. I am migrating an application that was in vb6 to .Net. The application uses Random file access and uses a binary sort method to find a record.
Here is the code
Do While (low < high Or low = high) And (f = 0) 'Checking for an account match
middle = (low + high) / 2
FileGet(FileNum, Record, middle)
If Account < Trim(Mid(Record.Data, Byte1Start, Byte1Len)) Then
[Code] .....
From reading up on this in .Net it seems that using the Binary Reader seek method would be the alternative to using old vb6 random access code. The problem is the Binary Reader Seek method goes by Byte position instead of record number. How to convert my code to use a binary reader.
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Jan 30, 2010
I am using Visual Basic 2009 to create a file of records to store students tests scores.Currently i can write to the file, create new records etc. However i cannot edit a particular record, im sure i have to use file seek function but i have no idea where to start.here is some of my source code to give you an idea of where im at
Do While (Not EOF(1)) And found = False 'loop until no more records or the record is found
nosrecords = nosrecords + 1
FileGet(1, onestudent, nosrecords)[code].....
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May 4, 2009
I need to write data to a file, preferably in binary format, but I am unaccustomed with the concept. Where's the easiest place to get the basics? I could come here with a specific need, but I'm at the point right now where I am more willing to work within the confines of keeping it simple.
Here's what I know:
1. how to open a new file
2. how to specify the record length
3. how to close the file
Some specific questions:
Does the record length have to be constant throughout the file?
Can I read the nth record without reading the whole file?
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Mar 6, 2011
I am trying to write data to a binary file using the Print() method, but when I run it I get the System.IO exception Bad File Mode.
Here's the code for the FileOpen declaration, that might have something to do with it?
FileOpen(filenumber, "path to file", OpenMode.Binary, OpenAccess.Write, OpenShare.LockReadWrite)
Print(filenumber, expression(variable))
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Nov 2, 2009
Recently I experiment with the binary file type. I have this structure[code]...
It works. And now, in the load event of the form I want to know, how many records (structures) are stored in the file.
Another question: how can I search and seek in the file (structure to structure, not byte to byte)?
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Oct 3, 2010
To read a record in a binary file in VB^ I would define a type with all the fields specifying strings as STRING * whatever the length of the field was.
For example:
Type Record
Field1 as string *15
Field2 to as string * 20
Field3 as String * 10
field4 as byte(10)
End Type
Dim filerecord as record
I would the open my binary fiel and do a Get#1,, filerecord
The record would be read and all the fielsd would be in place.
Now with the new Structure we cant dimension an array in the Structure And wjhen declaring strings we can't specify the length.
I tried to create structire and use a stream binary reader. and just read afixed number of bytes into the type, The program says it canvert bytes to my fiels.
So how do I do this. Or has Microsoft in their infinite wisdom left no way to do this.
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Apr 26, 2010
I used to read a binary file by formatting a record type and then using the Get command to get the data. What is the equivalent in VB.net?
Code:
'In Module.bas
Public Type recordtype
dist As Single
[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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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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Apr 28, 2009
I have an array of words that must be sorted alpabetically using selection sort, I must then be able to search the array with a binary search. I just can't get my head around how you would go about doing it. I know that the words must be first sorted into alphabetical order. Here is the code for selection sort with numbers:
Dim pass As Integer
Dim count As Integer
Dim minmax As Integer
Dim temp As Integer
[code]....
How would you apply that to an array of strings?
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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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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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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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Nov 13, 2011
1) a text document which has content like :
uber|uber|ultra
taxi|taxi|taxi cab|cab|minicab|airport taxi|airport transfer
genitalia|genitalia|genitals
[code].....
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May 11, 2010
i'm beginer in this forum and new in vb6.how to generate random number in vb6?
is it posible to represent variable in binary?
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Nov 2, 2009
how to read and write random access records in .NET. Now I know random access files are dead and the response on every query I found with google/bing/yahoo searches was don't use random access use Binary serialization but I can not. I have a situation where I need to read and modify 256 byte records in a file that is used by another application.
Now for a bit of background the file is made up of 27 fixed length records of 256 bytes. Each of the records has a separate structure consisting of 30-120 fields. The proplem I am having is I can create the record structures but when using the FileGet method I am receiving an error. Now I have found samples that showed the same format I am using that claim to work.
The error I am getting is Option Strict On disallows narrowing from type 'System.ValueType' to type 'ProgramName.ModuleName.Record' in copying the value of 'ByRef' paramater 'Value' back to the matching argument.
The basic layout (simplified) is as follows:
Code:
Structure Record
<VBFixedString(6)> Public SomeParam as String
Public SomeNumber as Short
[Code]....
Now the overloads for FileGet show all of the data types including Object. But I have tried various methods to retreive the 256 byte record but without success. Do I have to actually read each of the several hundred fields of the structure one by one? Or am i overlooking something (I have been known for this in the past)
Or (and I'll kick myself if this is the only way) do I just have to set option strict Off in the module and the code as above will actually work.
I would love to be able to just ditch the random access file but I have to keep it for compatibility with several other applications at this time.
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Sep 3, 2010
The application reads information similar to a DXF file. For purposes of discussion, the data consists of lines, those lines have endpoints, x1,y1,x2,y2. Within the file those lines create "paths", in other words, they are connected. There can be many separate paths within a single file. However in the original file, the geometry is not in any particular order, the paths are not indicated.
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Nov 17, 2010
I'm tasked with the job of creating a javascript version of a units conversion application written in vb6. I have the source code but I don't have vb 6. The source code uses a dat file to hold a conversion array (unit type, unit, xfactor, plusfactor). Getting the data out of this file would be good to me. I tried creating a little app in vb 2010 to write the data from that dat file to a txt file using essentially the same code as the source code. And that has been somewhat successful (took a while to figure out the fixed string business). Now I can pull the data out as an array. The math elements of this array look fine but the strings are somewhat read-able but too garbled to use. I can't seem to fix that by changing the character set/encoding.
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Feb 24, 2010
This time, basically, i'm working with Random Access Files.I have this et of code to read data from a form a save it into a .dat file. This works fine.
Public Class frmDramaClub
Structure MemberRecord
Dim ID As Integer[code].....
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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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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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Aug 29, 2011
Current S/W Access 2010 and Windows 7 (all up to date) also using VS2008 When I was using Access 2003 & 2007 the following VB.Net code line worked fine:
dbs.Execute("SELECT * INTO TrialBOYTbl FROM [Text;FMT=CSVDelimited;HDR=Yes;DATABASE=" & myPath & ";].[TrialBOYDtl#csv];")
But when I use Access 2010 the first data record is missing in every file that I upload - there are no other errors.The SCHEMA.INI file is:
[TrialBOYDtl.csv]
ColNameHeader = True
Format=CSVDelimited
MaxScanRows = 25
[code]...
NOTE: This code line is executed in VB.Net (Interop) in conjunction with Access Automation. Therefore, I believe that I must use DAO
as that is how MS Access is based.My guess is "[Text;FMT=CSVDelimited;HDR=Yes;DATABASE=" looks like an ADO (not DAO???) Extended Properties specification which worked fine until Access 2010.
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Mar 17, 2010
I've seen many examples in LINQ but i'm not able to reproduce the same result in vb.net.
I have following code: Dim context As New MyModel.Entities()
Dim rnd As New System.Random()Dim gardens As List(Of Tuin) = (From t In context.Gardens Where _
t.Approved = True And _
Not t.Famous = True _
Order By rnd.Next() _
Select t).ToList()
[Code]...
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Apr 9, 2011
I have a delete method for a binary search tree. It only deletes the last two entered values. When trying to delete the root or anything to left of it it returns a null pointer exception.
PublicFunction Delete(ByVal key AsInteger) AsBoolean Dim current AsNode = root Dim parent AsNode = root Dim isLeftChild AsBoolean = True While (current.value <> key)
parent = current If (key < current.value) Then isLeftChild = True current = current.rightNode Else
[code].....
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Sep 2, 2010
I am trying to serialize object in method binary mode. However, I would like to get a file in human-unreadable format. which means i want to encrypt file. In my memory, if i want to write text into binary file in C, when I set writing mode as binary, I will get a file in human-unreadable format, but in .net, I can't get that.
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Feb 26, 2010
I made this tiny program that pulls in a text file data with StreamReader method. Okay how can I sort the text file alpahbetically A - Z while it comes in is this possible? [code]
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Feb 25, 2010
Just a litte about me. Well, I am not intermediate but I am not a beginner either. And I like to try to do my own work as much as I can. I am not a mooch just to let you know.
I made this tiny program that pulls in a text file data with StreamReader method. Okay how can I sort the text file alpahbetically A - Z while it comes in is this possible? and how do I do it, I have no clue.
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