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I was looking at whether I could get a dynamic string into a type that I could use PB's routines against. Here's the result.
Essentially you declare a dword somewhere (such as in a type).
You do nothing, it's initially an empty string.
If you want to assign it a value you use the result of AllocateString( "my value" )
When you no longer want the string you call FreeString
If you want to use PB's string routines you call AquireString. When you're done using the routines you call ReleaseString.
You can get the length of the string calling StringLen without acquiring the string.
Could have some bugs in it, but the trivial example seemed to work...
ManualStrings.bas
Edit: Note, these strings should only be used as rval, never as lvals. what that means is you can use them, but you can't ask PB to alter them. You can assign to a pb string, alter the pb string, and then assign back. Some examples of where not to use acquired strings are:
aquiredString += value ' BAD
Replace "x" with "y" In aquiredString ' BAD
The basic rules are:
Any AquiredString must call ReleaseString when you are done with the string variable.
Any AssignString, AllocateString, CopyString must call FreeString when the string value is no longer needed.
I added SafeString which returns a native PB string and can be used in any context. It does not need to be released or freed. It's simpler to use at the cost of a string assignment (i.e. copy).
Essentially you declare a dword somewhere (such as in a type).
You do nothing, it's initially an empty string.
If you want to assign it a value you use the result of AllocateString( "my value" )
When you no longer want the string you call FreeString
If you want to use PB's string routines you call AquireString. When you're done using the routines you call ReleaseString.
You can get the length of the string calling StringLen without acquiring the string.
Could have some bugs in it, but the trivial example seemed to work...
ManualStrings.bas
Code:
#Compile Exe
#Dim All
#Include "windows.inc"
' Makes value be the string pointed to by p. These can only be used as RVAL's.
'Sub AquireString( ByVal p As Dword, value As String )
' Releases a string that was aquired
'Sub ReleaseString( value As String )
' Returns the length of a string without aquiring it
'Function StringLen( ByVal p As Dword Ptr ) As Long
'Assigns a value to a string
'Sub AssignString( p As Dword, value As String )
'Returns a pointer to a newly allocated string
'Function AllocateString( value As String ) As Dword
'Releases the memory for an Assigned or Allocated string
'Sub FreeString( p As Dword )
'Copies a string
'Sub CopyString( src As Dword, dst As Dword )
'Returns a safe PB string, can be safely used as an lval, does not need to be released
'Function SafeString( src As Dword ) As String
Type StringExample
name As Dword
other As Dword
End Type
Function PBMain () As Long
Local v As StringExample
v.name = AllocateString( "This is a test" )
Local b, a As String
AquireString v.name, a
b = a + " for sure"
ReleaseString a
AssignString v.name, b
? a ' s/b empty
AquireString v.name, a
? a ' s/b "This is a test for sure"
ReleaseString a
? Str$( StringLen( v.name ) )
CopyString v.name, v.other
AquireString v.other, a
? a
ReleaseString a
FreeString( v.name )
FreeString( v.other )
End Function
Sub AquireString( ByVal p As Dword, value As String )
value = "" ' Release whatever the string was pointing to
Poke Dword, VarPtr( value ), p
End Sub
Sub ReleaseString( value As String )
Poke Dword, VarPtr( value ), 0
End Sub
Function StringLen( ByVal p As Dword Ptr ) As Long
p-=4
Function = @p
End Function
Sub AssignString( p As Dword, value As String )
If p Then FreeString p
p = AllocateString( value )
End Sub
Function AllocateString( value As String ) As Dword
Local p As Dword Ptr
If Len(value)=0 Then
Function = 0
Exit Function
End If
p = GlobalAlloc( %GMEM_FIXED, Len(value)+5 )
Memory Copy StrPtr(value), p+4, Len(value)+1
@p = Len(value)
Function = p+4
End Function
Sub FreeString( p As Dword )
If p=0 Then Exit Sub
p -= 4
GlobalFree( p )
p = 0
End Sub
Sub CopyString( src As Dword, dst As Dword )
Local a As String
If src=dst Then Exit Sub ' Self copies are really quick!
If dst<>0 Then FreeString dst
AquireString src, a
dst = AllocateString( a )
ReleaseString a
End Sub
Function SafeString( src As Dword ) As String
Local a, b As String
AquireString src, a
b = a
ReleaseString a
Function = b
End Function
aquiredString += value ' BAD
Replace "x" with "y" In aquiredString ' BAD
The basic rules are:
Any AquiredString must call ReleaseString when you are done with the string variable.
Any AssignString, AllocateString, CopyString must call FreeString when the string value is no longer needed.
I added SafeString which returns a native PB string and can be used in any context. It does not need to be released or freed. It's simpler to use at the cost of a string assignment (i.e. copy).
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