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FRead3 Function

Read characters from a file into an allocated buffer.

Namespace:  XSharp.Core
Assembly:  XSharp.Core (in XSharp.Core.dll) Version: 2.6
Syntax
 FUNCTION FRead3(
	ptrHandle AS IntPtr,
	ptrBufferVar AS BYTE[],
	dwBytes AS DWORD
) AS DWORD
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Parameters

ptrHandle
Type: IntPtr
The handle of the file to read from.
ptrBufferVar
Type: Byte
Pointer to an allocated buffer used to store data read from the specified file.
The length of this variable must be greater than or equal to <dwBytes>. An array of bytes to store the data read from the specified file. The length of this variable must be greater than or equal to the number of bytes in the next parameter.
dwBytes
Type: UInt32
The number of bytes to read into the buffer.

Return Value

Type: UInt32
The number of bytes successfully read.
A return value less than <dwBytes> or 0 indicates end-of-file or some other read error.  FError() can be used to determine the specific error.
Remarks
FRead3() is the same as FRead(), except that the name of the buffer variable is a pointer and is not passed by reference. See FRead() for details. This function is assumed to handle raw binary data and is not dependent upon the status of SetAnsi().  FReadText() and FRead4(), on the other hand, are dependent upon SetAnsi().
Remarks
Tip Tip
The low level File IO functions in the X# runtime are using .Net filestreams in the background.
That means that the file handles returned by FOpen() and FCreate() are not 'normal' file handles, but unique identifiers that are used to find the underlying stream object in a collection of streams in the runtime.
That also means that you can't use file handles for functions such as FRead() and FWrite() that were not created in the X# runtime.
If you want to access the underlying FileStream, then you should call the function FGetStream()
Examples
This example uses FRead3() after successfully opening a file to read 128 bytes into a buffer area:
X#
 1DEFINE F_BLOCK := 128
 2Function Start()
 3    LOCAL cBuffer AS PTR
 4    cBuffer := MemAlloc(F_BLOCK)
 5    IF cBuffer = NULL PTR
 6        RETURN FALSE
 7    ENDIF
 8    ptrHandle := FOpen2("temp.txt", FO_READ)
 9    IF ptrHandle = F_ERROR
10        ? DOSErrString(FError())
11        RETURN FALSE
12    ELSE
13        IF FRead3(ptrHandle, cBuffer, F_BLOCK) <> F_BLOCK
14            ? DOSErrString(FError())
15            RETURN FALSE
16        ENDIF
17        FClose(ptrHandle)
18    ENDIF
19    MemFree(cBuffer)
20    RETURN TRUE
See Also