Re: [avr-gcc-list] Struct problem

[Eric Fu]

I've tried that and I almost got the 500 bytes back. 
Thanks for all the help.  Happy coding everyone!

Eric Fu

----- Original Message ----- 
From: "Dave Hylands" <address@hidden>
To: "Eric Fu" <address@hidden>; <address@hidden>
Sent: Saturday, January 31, 2004 5:16 PM
Subject: RE: [avr-gcc-list] Struct problem


You don't need to use malloc. You could just put the pointers in you
UART struct and still use global variables.

byte rxBuf[ RX_BUFFER_SIZE0];
byte txBuf[ TX_BUFFER_SIZE0];

uart0.pRxBuf = rxBuf;
uart0.pTxBuf = txBuf;

If you don't need to use malloc, then this will save you the 500 bytes.

*(uart0.pRxBuf+TmpTail) is the same as uart0.pRxBuf[ TmpTail ];

Personally, I find the 2nd form easier to read.

--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/


> -----Original Message-----
> From: Eric Fu [mailto:address@hidden 
> Sent: Friday, January 30, 2004 9:44 PM
> To: address@hidden
> Subject: Re: [avr-gcc-list] Struct problem
> 
> 
> It works. That's great.
> But it added an unbelievable 500Bytes! It seems the code size 
> under AVR GCC varies a lot for different implementations of 
> the same task. In my case, what I changed was to access  UART 
> buffer from arrays to pointers with malloc. I redefined:
>     ...
>   byte *pTxBuf,*pRxBuf;
>      ...
> Allocated memory as:
> uart0.pRxBuf = malloc(RX_BUFFER_SIZE0);
>  uart0.pTxBuf = malloc(TX_BUFFER_SIZE0);
> 
> Used such as
> return *(uart0.pRxBuf+TmpTail);           // Return data
> There are no other changes apart from the change to access 
> the buffer. Is this normal?
> 
> Eric Fu
> 
> ----- Original Message ----- 
> From: "Brian Cuthie" <address@hidden>
> To: "'Eric Fu'" <address@hidden>; <address@hidden>
> Sent: Saturday, January 31, 2004 1:59 PM
> Subject: RE: [avr-gcc-list] Struct problem
> 
> 
> >
> > You can use malloc() to create your buffers and they'll still be 
> > globally accessible so long as the pointers you store them in are 
> > global.
> >
> > -brian
> >
> > > -----Original Message-----
> > > From: Eric Fu [mailto:address@hidden
> > > Sent: Friday, January 30, 2004 9:52 PM
> > > To: address@hidden; address@hidden
> > > Subject: Re: [avr-gcc-list] Struct problem
> > >
> > > Thanks for the tip.
> > > The buffers need to be Global, since it needs to be accessible in 
> > > different modules. My understanding is that malloc is for 
> allocating 
> > > dynamic memory. Anyway, I will read my C book for clue. 
> Thanks for 
> > > pointing the direction.
> > >
> > > Eric Fu
> > >
> > >
> > > ----- Original Message -----
> > > From: "Brian Cuthie" <address@hidden>
> > > To: "'Eric Fu'" <address@hidden>; <address@hidden>
> > > Sent: Saturday, January 31, 2004 12:22 PM
> > > Subject: RE: [avr-gcc-list] Struct problem
> > >
> > >
> > > >
> > > > The problem, quite simply, is that because the size of TxBuf[] 
> > > > isn't specified, the offset within the struct to 
> RxBuf[] can't be
> > > computed at
> > > > compile time (which it needs to be).
> > > >
> > > > To do what you want you'll need to change the struct so
> > > that instead of
> > > > arrays, TxBuf and RxBuf are pointers. Then malloc the
> > > memory you need and
> > > > store the addresses in TxBuf and RxBuf respectively.
> > > >
> > > > You might want to re-read a few chapters in your C book.
> > > >
> > > > -brian
> > > >
> > > > > -----Original Message-----
> > > > > From: address@hidden 
> > > > > [mailto:address@hidden On Behalf Of Eric Fu
> > > > > Sent: Friday, January 30, 2004 8:05 PM
> > > > > To: address@hidden
> > > > > Subject: [avr-gcc-list] Struct problem
> > > > >
> > > > > Hi All,
> > > > >
> > > > > I'm trying to declare a Structure for UART, so that it can be 
> > > > > used for more than one UARTs such as: typedef struct UART
> > > > > {
> > > > >  volatile byte RxHead;
> > > > >  volatile byte RxTail;
> > > > >  volatile byte TxHead;
> > > > >  volatile byte TxTail;
> > > > >  byte TxBuf[],RxBuf[];
> > > > > }UART;
> > > > > extern UART uart0;
> > > > > extern UART uart1;
> > > > >
> > > > > By doing this way, I can assign different buffer size to 
> > > > > different UART such as: byte uart0.RxBuf[RX_BUFFER_SIZE0];
> > > > > byte uart0.TxBuf[RX_BUFFER_SIZE0];
> > > > > byte uart1.RxBuf[RX_BUFFER_SIZE1];
> > > > > byte uart1.TxBuf[RX_BUFFER_SIZE1];
> > > > >
> > > > > However, I get the following compile error:
> > > > > UART.h:47: error: flexible array member not at end of struct
> > > > >
> > > > > Could anyone give me a hint on How to tell the compiler
> > > to do this?
> > > > > Thanks
> > > > >
> > > > > Eric Fu
> > > > > _______________________________________________
> > > > > avr-gcc-list mailing list
> > > > > address@hidden 
> > > > > http://www.avr1.org/mailman/listinfo/avr-gcc-list
> > > > >
> > > >
> > > >
> > >
> > >
> >
> >
> 
> 
> 
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