arrays of fixedlen strings

[Ralph Brereton]

I would have liked to do
DIM lines_of_text(139) as string * 50
and then fill the array with strings varying in length from 3 to 50.
I imagined this would allocate memory for the array only once.

However, I am only allowed to do
DIM lines_of_text(139) as string

Question 1 Will this cause lots of memory reallocation every time I insert a line ?

Question2 If so, can anyone think of a way to avoid all that memory reallocation ?

[Elias Montoya]

What compiler are you using? On My System,
Dimensioning "DIM lines_of_text(139) AS STRING * 50" IS possible.
and this example below takes around 0.3 seconds.

139 lines of 50 characters each is nothing. I dont think it will cause
lots of memory reallocation when you insert a new line.

#COMPILE EXE
#DIM ALL

FUNCTION PBMAIN () AS LONG
    
LOCAL Index AS LONG
LOCAL T AS SINGLE
DIM lines_of_text(139) AS STRING * 50

T = TIMER

FOR Index = 1 TO 139
 lines_of_text(Index) = "Example text: This is an example of a string." & FORMAT$(Index)
NEXT Index

FOR Index = 1 TO 5000
 REDIM PRESERVE lines_of_text(UBOUND(lines_of_text())+1)
 ARRAY INSERT lines_of_text(50), "Example text: This is an example of a string." & FORMAT$(Index)
NEXT Index

MSGBOX "All the process took: " & STR$(TIMER-T),,"Task Complete"
    

END FUNCTION

I

[Elias Montoya]

Doing it this way takes 0.00 seconds on my system.

#COMPILE EXE
#DIM ALL

FUNCTION PBMAIN () AS LONG
    
LOCAL Index AS LONG
LOCAL T AS SINGLE
DIM lines_of_text(139) AS STRING * 50

T = TIMER

FOR Index = 1 TO 139
 lines_of_text(Index) = "Example text: This is an example of a string." & FORMAT$(Index)
NEXT Index

REDIM PRESERVE lines_of_text(UBOUND(lines_of_text())+5000)

FOR Index = 140 TO 5139
 lines_of_text(Index) = "Example text: This is an example of a string." & FORMAT$(Index)
NEXT Index

MSGBOX "All the process took: " & STR$(TIMER-T),,"Task Complete"
    

END FUNCTION

[Ralph Brereton]

My compiler is PBWin 8.04
My reasons for saying that
dim myarray(139) as string * 50 was not allowed
were
1) that my compiler would not accept * 50
2) that I could find no such example in PBHelp

Thank you, both, for pointing out that it is possible to do what I want.
Clearly something else must be wrong with my code.
I shall now go and check everything again.

Thanks for the help, and I'm sorry to have troubled you.
With best regards, Ralph.

[Cliff Nichols]

What about ASCIIZ * 50
?

Unless I mis-read the docs, String*50 and ASCIIZ*50 are the same thing? (not sure about nulls though)

[Dale Yarker]

Ralph,

Try this:
LOCAL Index AS LONG
LOCAL T AS SINGLE
LOCAL lines_of_text() AS STRING * 50
DIM lines_of_text(139)

Cliff,

To have upto 50 characters in ASCIIZ would be:

LOCAL MyStr AS ASCIIZ * 51

because the last character is always NUL.

Cheers,

[Kev Peel]

The fixed STRING * [size] type auto-pads with spaces when you make an assignment, whereas the ASCIIZ type just NULL-terminates after the data. ASCIIZ is most compatible with the API, and the fixed STRING is backwards compatible with older code and for those situations where you might need the padding.

1) that my compiler would not accept * 50

All versions of PB/WIN should accept that syntax. Can you show us the failing code and compile error?

[Chris Holbrook]

You could always declare a string, use string$ to make it "of a length" and manage your own substring allocation within it, either using byte pointers or MID$. It would depend a bit on the context.

[jcfuller]

Another alternative is have an array of ASCIIZ PTRS and use

DIM MyszArray(10) AS ASCIIZ PTR

MyszArray(0) = SysAllocStringByteLen(szString,LEN(szString))

Dont forget to deallocate

SysFreeString MyszArray(0)

James

[Chris Holbrook]

MyszArray(0) = SysAllocStringByteLen(szString,LEN(szString))

like it!

[John Gleason]

Doing it this way takes 0.00 seconds on my system.

Here's yet another fast way. The kewl timer is thanks to Dave Roberts!

#COMPILE EXE
#DIM ALL

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Dave Roberts' timer macros--best used in an include file so available any time.
DECLARE FUNCTION QueryPerformanceCounter LIB "KERNEL32.DLL" ALIAS "QueryPerformanceCounter" (lpPerformanceCount AS QUAD) AS LONG
DECLARE FUNCTION QueryPerformanceFrequency LIB "KERNEL32.DLL" ALIAS "QueryPerformanceFrequency" (lpFrequency AS QUAD) AS LONG

MACRO onTimer
  LOCAL qFreq, qOverhead, qStart, qStop AS QUAD
  LOCAL f AS STRING
  f = "#.###"
  QueryPerformanceFrequency qFreq
  QueryPerformanceCounter qStart ' Intel suggestion. First use may be suspect
  QueryPerformanceCounter qStart ' So, wack it twice <smile>
  QueryPerformanceCounter qStop
  qOverhead = qStop - qStart     ' Relatively small
END MACRO

MACRO goTimer = QueryPerformanceCounter qStart
MACRO stopTimer = QueryPerformanceCounter qStop

MACRO showTimer = USING$(f,(qStop - qStart - qOverhead)*1000000/qFreq /1000) + " milliseconds"
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

FUNCTION PBMAIN () AS LONG

LOCAL Index AS LONG
LOCAL T AS SINGLE
LOCAL preString AS STRING
onTimer      'ready timer for use
goTimer      'start timing

DIM lines_of_text(5139) AS STRING * 50
FOR Index = 1 TO 139
 lines_of_text(Index) = "Example text: This is an example of a string." & FORMAT$(Index)
NEXT Index

REDIM PRESERVE lines_of_text(UBOUND(lines_of_text())+5000)

FOR Index = 140 TO 5139
 lines_of_text(Index) = "Example text: This is an example of a string." & FORMAT$(Index)
NEXT Index

stopTimer
MSGBOX "Original process took: " & showTimer  'STR$(TIMER-T),,"Task Complete"

goTimer

preString = REPEAT$(5139, "Example text: This is an example of a string.     ")
REDIM lines_of_text(1 TO 5139) AS STRING * 50 AT STRPTR(preString)

stopTimer
MSGBOX "Absolute array process took: " & showTimer                                    

END FUNCTION

[jcfuller]

like it!

Yeah. I use it all the time primarily for strings in udts. No need to preallocate with ASCIIZ * xxx to make sure you have enough room for all eventual sizes.

If I'm not mistaken it's the same call PB uses for STRING allocation.

James

[jcfuller]

Another neat feature is you have the length available too.

James

#COMPILE EXE
#DIM ALL
#INCLUDE "WIN32API.INC"
FUNCTION PBMAIN () AS LONG

    LOCAL szPtr AS ASCIIZ PTR
    LOCAL dwPtr AS DWORD PTR

    szPtr = SysAllocStringByteLen("James",LEN("James"))
    dwPtr = szPtr
    DECR dwPtr
    PRINT @szPtr
    PRINT "Len = ";FORMAT$(@dwPtr)
    WAITKEY$
    SysFreeString szPtr

END FUNCTION

[Ralph Brereton]

"Can you show us the failing code and compile error"

Problem was solved after Elias Montoya said it should work.
Code shown on this site:-
DIM lines_of_text(139) as string * 50
was a simplified version of my actual code.
The actual code was much more complicated and it had a syntax error.