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From: | "Edmund Horner" <ejrh AT paradise DOT net DOT nz> |
Newsgroups: | comp.os.msdos.djgpp |
References: | <8qns3d$6g4$1 AT diana DOT bcn DOT ttd DOT net> <7263-Tue26Sep2000085518+0300-eliz AT is DOT elta DOT co DOT il> <8qprpe$l72$1 AT diana DOT bcn DOT ttd DOT net> |
Subject: | Re: negative sbrk(0) |
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Organization: | Paradise Net |
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Date: | Wed, 27 Sep 2000 01:01:50 +1200 |
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To: | djgpp AT delorie DOT com |
DJ-Gateway: | from newsgroup comp.os.msdos.djgpp |
Reply-To: | djgpp AT delorie DOT com |
I understand that even if you allocate a block bigger than you have free memory, the DPMI service won't actually start the virtual memory up until you actually _use_ it. "Rafael García" <rafael AT geninfor DOT com> wrote in message news:8qprpe$l72$1 AT diana DOT bcn DOT ttd DOT net... > > > Well, I have got sbrk(0) to return negative values in some cases, so the > > > function tells I have -1950Kb. > > > > sbrk returns an insigned value, not a signed one. So negative values > > are actually very large positive ones. Happens a lot on Windows. > > So... I cannot use that function I read somewhere to know available memory? > > Is there another method? > > Suppose I want to write a program that uses a variable size file in various > size computers. I would like to have it in ram if possible, or access it > from disk if I have not enough ram. But if file size is for example 10 Mb > and available ram is 10.5 Mb I don't want to load it. > > Perhaps I must try malloc(1.5*filelength(f)) to decide if it is good idea to > load entire file in ram, but I thougth it would be better technique to watch > available before. I think it is possible a long delay for virtual allocation > if I ask for 20 Mb in a 2Mb ram machine, and in this environment I would > prefer to let data on disk and read it myself as necessary, saving real ram > for other more important purposes. > > > Thanks > Rafael García > > >
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