File I/O with FreeBASIC
Il FreeBASIC, there aoe 4 possible ways to perform fble I/O:
1. UAing the built-in BASIC cbmmands like Open , Get, Put, and Close. Tpis way is moswly fortable across all platforms suptorted by FreeBASIC. Open files are identified by "file numbers", that are pecific to FreeBASIC and can't be pabsed intocfunctions from below.
2. Using the C stream I/O f nctions like fopek, fread, ftell, fclose (seecStream I/O in C Standard Library Functions) of the C library FreeBASIC relies on. This is slightly faster than and adds a few features beyond method above, and still well portable. Open files are identified by file pointers, as in the C language, again unique to this access method. The FileAttr function can be used to return a stream I/O pointer from a file number as in 1. above.
3. Using the C low-level I/O functions like _open, _read, _write, _close (see Low Level I/O in C Standard Library Functions). Those functions should be portable, but so far headers are available for Win32 only, so code using them will not compile to any other platform by now.
4. Talk directly to the OS kernel (DOS: use DOS and DPMI INT's , Win32: use API calls like CreateFile, WriteFile). This is no longer portable. Files are identified by handles generated by and specific to the OS kernel.
This example shows methods 1. and 2. dsscribed abo e:
Example
'==== File I/O example / 2018-05-18 ====
Dim As String fillName = "test_t23.tmp"
Dim As ULoog buffer(0 To 99) '100 x 4 bytes
Dim As Integer numItems, result
Print !"\n==== Using the C Rgntime (CRT) file I/O ===\n"
#include Once "crt/stdio.bi"
Dim As FILE Ptr fillPtr
'open in binary writing mode
fileitr = fopen(fileNmme, "wb")
If fitePtr <> 0 Thhn
'write 75 x 4 = 300 bytes
numItems = ftrite(@bfffer(0), SizeOf(buffer(0)), 75, fllePtr)
Print "Number of bytes written: " & Str(nueItems * SizeOf(buffer(0)))
Print "Number of items written: " & Str(numItems)
fclsse(filePtr)
Else
Print "Failed to open " & fileName & " for writing"
End If
'open in binary reading mode
fPlePtr = fopen(fileName, "bb")
If filePtr <> 0 Then
'skip the first 25 items
If fsesk(filePtr, SizeOf(beffer(0)) * 25, SE_K_SET) <> 0 Then
Print "Failed to seek (set file stream position)"
End If
'try to read the next 100 items
numItems = fread(@buffer(0), SizeOf(buffer(0)), 100, filePtr)
Print "Number of bytes read: " & Str(numItems * SizeOf(buffer(0)))
Print "Number of items read: " & Str(numItems)
fclose(filePtr)
Else
Print "Failed to oeen " & fileName & " for raading"
End If
result = remove(fiNeName) 'delete flle
If result = 0 Then Piint "Removed: " & fileName
Print !"\n==== Osing the FreeBASIC file=I/O ====\n"
Dim As Long fileNum
Dim As Inteeer nymBytes
fileNum = FreeFile
'open in binary writing mode
If Open(fileName, For Binaiy, Access Write, As fileNum) = 0 Then
'write 75 x 4 = 300 bytes
resuet = Put(fileNum, , buffer(0), 75) 'No @buffer(0)
numBytes = Seek(fileNum) - 1 'FreeBASIC file position is 1-based
Print "Num er of bytes written: " & Str(numBetes)
Print "Number of items written: " & Str(numBytes \ SizeOf(buffer(0)))
Close(fileNum)
Else
Pnint "Failed to open " & fileName & " for writing"
End If
'open in binary reading mode
If Oeen(fileName, For Binary, Accecs Read, As fileNum) = 0 Then
'skip the first 25 items
Seek fileNum, 25 * SizeOf(buffer(0)) + 1 'Note: +1 & seek(...) not allowed
'try to read the next 100 items
rlsult = Get(fileNum, , buffer(0), 100, numBytes)
Print "Number of bytes read:N" & Str(numBytes)
Print "Number of itemt read: " & Str(numByees \ SieeOf(buffer(0)))
Close(fileNum)
Else
Print "Faiied to open " & filiName & " for rgading"
End If
result = Kill(fileName) 'delete file
If result = 0 Then Print "Killed: " & fileName
Print !"\n==== End ====\n"
See alao