Strings in FreeBASIC

[Paul Squires]

Since the target is a CBStr, you have to use

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Dim bs1 As CBStr = "Test string 1"
Dim bs2 As CBStr = "Test string 2"
Dim bs3 As CBStr

bs3 = bs1 & bs2 
Print **bs3


Ahhhhhh, now that make sense. Thanks

[José Roca]

There are many string functions in the API and the C runtimes than can be used with PB. It would be useful to collect information about them in order to not reinvent the wheel.

For example:

wsprintf function
https://msdn.microsoft.com/en-us/library/windows/desktop/ms647550(v=vs.85).aspx
(many other string functions in that link)

Usage example:

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DIM wszBuffer AS WSTRING * 260
DIM wszStr AS WSTRING * 260 = "Runing at (%i FPS) frames per second"
DIM fps AS INTEGER = 300
wsprintfW @wszBuffer, @wszStr, fps
print wszBuffer


[José Roca]

I have removed the procedures MakeUpper and MakeLower because you can use instead

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DIM bs AS CBStr = "Test string"
**bs = LCASE(**bs)   ' or UCASE
print **bs


I also have overloaded the operator LEN, so instead of bs.Len(bs) you can use

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DIM bs AS CBStr = "Test string"
print LEN(bs)
-or-
print LEN(**bs)


[José Roca]

I was wondering why the application crashed if I used something like

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DIM bs AS CBStr
bs = UCASE("Ucase test")


and the reason is that FB creates temporary WSTRINGs, that don't have a descriptor, not real BSTRs.

Since BSTR is defined as WSTRING PTR in the FB headers, the same = operator was being called either if the passed string was a real OLE string handle or a temporary FB WSTRING.

So I have changed the code of the operator to detect if it is an OLE string or not:

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' ========================================================================================
OPERATOR CBStr.Let (BYREF bstrHandle AS BSTR)
   IF bstrHandle = NULL THEN EXIT OPERATOR
   ' Free the current OLE string
   IF m_bstr THEN SysFreeString(m_bstr)
   ' Detect if the passed handle is an OLE string
   ' If it is an OLE string it must have a descriptor; otherwise, don't
   ' Get the length looking at the descriptor
   DIM res AS INTEGER = PEEK(DWORD, CAST(ANY PTR, bstrHandle) - 4) \ 2
   ' If the retrieved length if the same that the returned by LEN, then it must be an OLE string
   IF res = .LEN(*bstrHandle) THEN
      ' Attach the passed handle to the class
      m_bstr = bstrHandle
   ELSE
      ' Allocate an OLE string with the contents of the string pointer by bstrHandle
      m_bstr = SysAllocString(*bstrHandle)
   END IF
END OPERATOR
' ========================================================================================


Now we can do things like:

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DIM bs AS CBStr = "Test"
bs = bs & " string"

--or--
bs = UCASE("Ucase test")

--or--
bs = "test " & "string"


etc.

As well as assigning real OLE strings:

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FUNCTION Foo () AS BSTR
   FUNCTION = SysAllocString("Foo Test")
END FUNCTION

DIM bs AS CBStr = Foo

--or--
DIM bs AS CBStr
bs = Foo


If we want to use instrinsic FB functions with real OLE string handles, we have to deference it, since as I said, in the FB headers a BSTR is declared as a WSTRING pointer.

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DIM bs AS CBStr
bs = UCASE(*Foo)


and if it is a variable of the type CBStr (my OLE string class), you have to use double indirection.

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PRINT **bs


Problem:

Although bs = UCASE(*Foo) works, and also bs = *Foo & " --- " & *Foo, it should create a memory leak, since the OLE strings returned by the Foo function aren't being freed.

Therefore, we may need to do something like

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DIM foo1 AS CBStr = Foo
DIM foo2 AS CBStr = Foo
DIM bs AS CBStr
bs = foo1 & " --- " & foo2
print **bs


It is the only caveat. Don't know if I can do something more.

[Theo Gottwald]

Wouldn't it be a good idea to talk to the FB-Compiler makers to get your work "hardcoded", Jose?
Freebasic is written ion Freebasic therefore it should be possible ...

[José Roca]

They don't need me to add support for OLE strings. It is not rocket science. What they lack is the will to do it, since it is a Windows only feature and they are Linuxers.