The ReadStringAt$ function will read a text string from any position within an open file channel. The command expects the string it's reading to be terminated with carriage return characters of 10 & 13.
So ReadStringAt$ lets you randomly access any piece of data within the file.
FACTS:
* Reading none sequential pieces of data can be slow
* ReadStringAt$ only works with files opened with ReadFile
Mini Tutorial:
This example creates a file and reads the with some various bits of data store in it, then read it's back again using the random access file commands.
; Create a file name
File$=TempDir$()+"PB_TestFile.txt"
; Get a Free File Channel Index
MyFile=GetFreeFile()
; CReate a File for writing data to
WriteFile File$,MyFile
; Write some Byte data at a byte pos 100
WriteByteAt 1,100,255
; Write some Word data at a byte pos 200
WriteWordAt 1,200,64000
; Write some Integer data at a byte pos 300
WriteIntAt 1,300,111222
; Write some Float data at a byte pos 400
WriteFloatAt 1,400,123.456
; Write some Stringt data at a byte pos 500
WriteStringAt 1,500,"Play Basic"
; Write some Stringt data at a byte pos 600
WriteChrAt 1,600,"Hello World",11
; Close this file channel
CloseFile MyFile
Print "============================"
Print "Reading File Data:"+File$
Print "============================"
; Get a Free File Channel Index
MyFile=GetFreeFile()
; Open a file to READ with READFILE
ReadFile File$,MyFile
; Read and display byte from position 100 in this file
Print ReadByteAt(myFile,100)
; Read and display the Word from position 200 in this file
Print ReadWordAt(myFile,200)
; Read and display the Integer from position 300 in this file
Print ReadIntAt(myFile,300)
; Read and display the Float from position 400 in this file
Print ReadFloatAt(myFile,400)
; Read and display the String from position 500 in this file
Print ReadStringAt$(myFile,500)
; Read and display the String from position 600 in this file
Print ReadChrAt$(myFile,600,11)
; Close this file channel
CloseFile MyFile
; Display the Size of the FIle
Print "============================"
Print "File Size:"+Str$(FileSize(file$))
Print "============================"
If FileExist(file$) Then DeleteFile file$
; Display the screen and wait for a key press
Sync
WaitKey
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This example would output.
============================
Reading File:C:Windows\temp\Pb_TestFile.txt
============================
255
64000
111222
123.456
Play Basic
Hello World
============================
File Size:611
============================
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