How to shrink an area of reserved memory

Mrs Beanbag · 05 July 2013, 20:27

OK here's my problem, I have loaded in a file into Fast Mem that contains some data that needs to be in Chip, so I copy it out. The Chip data is at the end of this block of data, so I want to free it up and get that fast mem back, without freeing up the whole block because I still need the rest of the stuff. In other words to shrink the allocated space, keeping the first part and discarding the latter part.

I know this must be possible because AMOS has a Bank Shrink function that preserves the address of the data. But how do I do this with Exec calls? If I try to "freemem" half way into an allocated area it seems to work but eventually crashes. I tried freeing the whole block and then AllocAbs it again, that doesn't work either

hooverphonique · 05 July 2013, 21:02

free/allocabs should work as long as you surround them with forbid/permit.. what do you mean by "doesn't work" ?

Mrs Beanbag · 05 July 2013, 21:23

well it just seems to hang, AllocAbs doesn't clear the memory to zeroes does it?

Toni Wilen · 05 July 2013, 21:36

Ugly Forbid()+FreeMem()+AllocAbs()+Permit() is the only working method. (EDIT: only if mungwall or similar program is not active..)

Note that first 8 bytes of FreeMem()'d memory region will be modified (Replaced with struct MemChunk).

Mrs Beanbag · 05 July 2013, 22:35

Thanks Toni! That was just the tip I needed, those first 8 bytes were really important!

05 July 2013, 20:27	#1
Mrs Beanbag Glastonbridge Software Join Date: Jan 2012 Location: Edinburgh/Scotland Posts: 2,243	How to shrink an area of reserved memory OK here's my problem, I have loaded in a file into Fast Mem that contains some data that needs to be in Chip, so I copy it out. The Chip data is at the end of this block of data, so I want to free it up and get that fast mem back, without freeing up the whole block because I still need the rest of the stuff. In other words to shrink the allocated space, keeping the first part and discarding the latter part. I know this must be possible because AMOS has a Bank Shrink function that preserves the address of the data. But how do I do this with Exec calls? If I try to "freemem" half way into an allocated area it seems to work but eventually crashes. I tried freeing the whole block and then AllocAbs it again, that doesn't work either

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05 July 2013, 21:02	#2
hooverphonique ex. demoscener "Bigmama" Join Date: Jun 2012 Location: Fyn / Denmark Posts: 1,643	free/allocabs should work as long as you surround them with forbid/permit.. what do you mean by "doesn't work" ?

05 July 2013, 21:23	#3
Mrs Beanbag Glastonbridge Software Join Date: Jan 2012 Location: Edinburgh/Scotland Posts: 2,243	well it just seems to hang, AllocAbs doesn't clear the memory to zeroes does it?

05 July 2013, 21:36	#4
Toni Wilen WinUAE developer Join Date: Aug 2001 Location: Hämeenlinna/Finland Age: 49 Posts: 26,574	Ugly Forbid()+FreeMem()+AllocAbs()+Permit() is the only working method. (EDIT: only if mungwall or similar program is not active..) Note that first 8 bytes of FreeMem()'d memory region will be modified (Replaced with struct MemChunk).

05 July 2013, 22:35	#5
Mrs Beanbag Glastonbridge Software Join Date: Jan 2012 Location: Edinburgh/Scotland Posts: 2,243	Thanks Toni! That was just the tip I needed, those first 8 bytes were really important!

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