On Wed, Jul 27, 2005 at 05:07:23PM -0700, Stephan Mueller wrote: > "Igor Pechtchanski wrote: > " > " On Thu, 28 Jul 2005, Krzysztof Duleba wrote: > " > > > I've simplified the test case. It seems that Cygwin perl can't > " > > > handle too much memory. For instance: > " > > > > " > > > $ perl -e '$a="a"x(200 * 1024 * 1024); sleep 9' > " > > > > " > > > OK, this could have failed because $a might require 200 MB of > " > > > continuous space. > " > > > " > > Actually, $a requires *more* than 200MB of continuous space. Perl > " > > characters are 2 bytes, so you're allocating at least 400MB of > space! > " > > " > Right, UTF. I completely forgot about that. > " > " Unicode, actually. > > Unicode is a standard that defines 'code points' (numeric values) for a > whole lot of different characters. UTF-8 is a specific encoding of > Unicode. It has the nifty property that ASCII characters are encoded > just as in ASCII -- one byte, with the high bit clear, and the low seven > bits representing a character in the range 0..127. Characters above the > ASCII range require multiple bytes -- sometimes two, sometimes more. > The algorithm is quite clever; find it in The Unicode Standard or with a > quick Google search. > > Another popular encoding is UCS-2, which is roughly "16-bit words each > holding one Unicode character". > > The latter is frequently what people think of as "Unicode". The former > is what perl uses internally to encode characters. > > End result is that the perl internal representation in the example above > probably only needs about 200MB of space, and not double that, as > suggested.
Correct; perl uses UTF-8 (actually, an extension of UTF-8 which allows codepoints up to 2**72-1). However code like the above does end up using twice the space; it's allocated once to store the result of the x operation and again when it's copied to $a. -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/
