April 2005 - Darwin-dev - lists.apple.com

Re: host to network byte order for floats, and float32_t?
by Derick Centeno 25 Apr '05

25 Apr '05

site_archiver(a)lists.apple.com Delivered-To: Darwin-dev(a)lists.apple.com On Apr 24, 2005, at 7:35 PM, Justin Walker wrote: On Apr 24, 2005, at 16:29, Warwick Hall wrote: Newbie question 1: Yes and no. Newbie question 2: HTH. Regards, Justin You'll be glad you did! _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… There are ntohl htonl ntohs htons functions that translate between host and network byte order for integer variables. Is there a need to worry about network byte ordering for floating point numbers such as float or double? Yes, because byte-order will certainly affect the value of a bit-string being interpreted as a floating point number. No, because what you are dealing with is a collection of macros used for low-level networking, where floating point numbers don't intrude. If you want to deal with floating point numbers in a higher-level protocol, you are in a pretty hairy problem domain. There are protocols (XDR, associated with Sun RPC, for one; Apollo's work, for another). Also there are commonly defined integer value types like uint32_t or int16_t (usually in stdint.h). Is there a float32_t (for float) or float64_t (for double)? Not really, AFAIK. Floats and doubles tend (in modern chip architectures) to be represented using an IEEE-standard format; so the commonly defined types *are* "float" (single-precision) and "double" (double-precision). These have precise meanings in the standards, and more-or-less common implementation limits in practice. -- In addition to what Justin noted regarding floats and doubles or rather what is defined as a float (single-precision) or double (double-precision) these values differ very greatly across computer languages and the libraries those languages use. It is not unheard of for many professionals to write their own libraries for these purposes as what is provided in common or commonly available is just not rigorous enough. This is something that becomes important when precision IS an issue to consider. Also of consideration is the fact that the media comprising the network can become a issue as well especially as poor quality media tend to scatter and confuse bit order and sometimes sequence, in different ways at different states of degradation depending upon the media used. This is also why the cheaper media requires more robust error correction routines versus optical media (such as fiber optic cables) with stronger data coherency can have error routines focussing upon the maintenance of the beam coherency as opposed to the details of bit order/sequence issues and the like. There exist several courses involving electronics, computer programming and other sciences including physics and mathematics all at very advanced levels discussing the details of these issues - separately. Just thought you should have a better idea of just how huge this subject is. If you do want to begin to approach these issues seriously for your own reasons, interests and projects. Feel free to access: www.fatbrain.com This email sent to site_archiver(a)lists.apple.com

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Re: host to network byte order for floats, and float32_t?
by Justin Walker 24 Apr '05

24 Apr '05

site_archiver(a)lists.apple.com Delivered-To: Darwin-dev(a)lists.apple.com On Apr 24, 2005, at 16:29, Warwick Hall wrote: Newbie question 1: Yes and no. Newbie question 2: HTH. Regards, Justin -- Justin C. Walker, Curmudgeon-At-Large Institute for General Semantics -------- Men are from Earth. Women are from Earth. Deal with it. -------- _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… There are ntohl htonl ntohs htons functions that translate between host and network byte order for integer variables. Is there a need to worry about network byte ordering for floating point numbers such as float or double? Yes, because byte-order will certainly affect the value of a bit-string being interpreted as a floating point number. No, because what you are dealing with is a collection of macros used for low-level networking, where floating point numbers don't intrude. If you want to deal with floating point numbers in a higher-level protocol, you are in a pretty hairy problem domain. There are protocols (XDR, associated with Sun RPC, for one; Apollo's work, for another). Also there are commonly defined integer value types like uint32_t or int16_t (usually in stdint.h). Is there a float32_t (for float) or float64_t (for double)? Not really, AFAIK. Floats and doubles tend (in modern chip architectures) to be represented using an IEEE-standard format; so the commonly defined types *are* "float" (single-precision) and "double" (double-precision). These have precise meanings in the standards, and more-or-less common implementation limits in practice. This email sent to site_archiver(a)lists.apple.com

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host to network byte order for floats, and float32_t?
by Warwick Hall 24 Apr '05

24 Apr '05

site_archiver(a)lists.apple.com Delivered-To: Darwin-dev(a)lists.apple.com Newbie question 1: Newbie question 2: Regards, Waz _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… There are ntohl htonl ntohs htons functions that translate between host and network byte order for integer variables. Is there a need to worry about network byte ordering for floating point numbers such as float or double? Also there are commonly defined integer value types like uint32_t or int16_t (usually in stdint.h). Is there a float32_t (for float) or float64_t (for double)? This email sent to site_archiver(a)lists.apple.com

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Re: Determining if a volume is a network volume from an absolute path?
by Stéphane Sudre 21 Apr '05

21 Apr '05

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com On jeudi, avril 21, 2005, at 12:19 AM, Justin Walker wrote: On Apr 20, 2005, at 14:33, Stéphane Sudre wrote: Perfect! It even contains the id of the user that mounted the filesystem. Cool... _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… Is it possible to determine from an absolute path if the file/folder described by the path is on a network volume or not? With the stat API I can get the inode's device (dev_t) but some grep in /usr/include are not very enlightening. The volume is "mounted" when I need to know this. man statfs This email sent to site_archiver(a)lists.apple.com

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Re: Determining if a volume is a network volume from an absolute path?
by Justin Walker 20 Apr '05

20 Apr '05

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com On Apr 20, 2005, at 14:33, Stéphane Sudre wrote: man statfs Cheers, Justin -- Justin C. Walker, Curmudgeon-At-Large Institute for General Semantics -------- Men are from Earth. Women are from Earth. Deal with it. -------- _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… Is it possible to determine from an absolute path if the file/folder described by the path is on a network volume or not? With the stat API I can get the inode's device (dev_t) but some grep in /usr/include are not very enlightening. The volume is "mounted" when I need to know this. This email sent to site_archiver(a)lists.apple.com

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Re: Determining if a volume is a network volume from an absolute path?
by Jerry Pendergraft 20 Apr '05

20 Apr '05

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com One method is to also use stat to get the device for /, then if the device for the directory in question is different, it must be mounted. That may be too simple, because it does not tell you if it is a remote or local mount. -- Jerry Pendergraft jerry.pendergraft(a)endocardial.com St. Jude Medical voice: 651-523-6935 1350 Energy Lane, Suite 110 fax: 651-644-7897 St Paul, MN 55108-5254 mobile: 651-491-0163 On Wed, 20 Apr 2005, Stéphane Sudre wrote: > Is it possible to determine from an absolute path if the file/folder > described by the path is on a network volume or not? > > With the stat API I can get the inode's device (dev_t) but some grep in > /usr/include are not very enlightening. > > The volume is "mounted" when I need to know this. > > > _______________________________________________ > Do not post admin requests to the list. They will be ignored. > Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) > Help/Unsubscribe/Update your Subscription: > http://lists.apple.com/mailman/options/darwin-dev/jerry%40endocardial.com > > This email sent to jerry(a)endocardial.com > _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… This email sent to site_archiver(a)lists.apple.com

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Determining if a volume is a network volume from an absolute path?
by Stéphane Sudre 20 Apr '05

20 Apr '05

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com The volume is "mounted" when I need to know this. _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… Is it possible to determine from an absolute path if the file/folder described by the path is on a network volume or not? With the stat API I can get the inode's device (dev_t) but some grep in /usr/include are not very enlightening. This email sent to site_archiver(a)lists.apple.com

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Re: how to get the location of a program
by Finlay Dobbie 20 Apr '05

20 Apr '05

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com Domainkey-signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:reply-to:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=HYxpWOWA2t083iVVD3H+23naS/BlEAMNtNXYbX5YNg0tJn2Dw2mfoEQXZ5stLXz1Yb1ypKWg0PKKGLj6HfIjP6bk1TIPxszrz4D2PV4j4zNEar1vNbT1v0ezInEp0hFpJG1yxPV16A0w95yPlvZA1HIoAHIurMGuHjHFlG8Up24= On 4/20/05, Kevin Van Vechten <kevin(a)opendarwin.org> wrote: > To be pedantic, look at CFBundle, which is available in Darwin and > therefore on-topic for this list. Also _NSGetExecutablePath in sys/crt_externs.h (there is sample code from DTS which shows how to replicate its functionality on pre-10.2 systems if you require.) -- Finlay _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… This email sent to site_archiver(a)lists.apple.com

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Re: Can user A kill any root process that's seteuid(A)?
by Justin Walker 20 Apr '05

20 Apr '05

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com On Apr 19, 2005, at 15:29, Dan Bernstein wrote: This is the right list. It seems to be possible for user A to kill -9 a process whose saved set-user-ID is 0 (root) and effective user ID is A's. Yup. Check 'man 2 kill' for details. Is there any way for a process to avoid getting killed like that when doing, say, a seteuid(A)-fopen()-seteuid(0) sequence to access a file under A's permissions (like pppd does with ~/.ppprc)? Regards, Justin -- Justin C. Walker, Curmudgeon-At-Large Institute for General Semantics -------- When LuteFisk is outlawed, Only outlaws will have LuteFisk -------- _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… I hope the following is not too off-topic for darwin-dev. I am not aware of any way to do this. The only issue is permission, which is dictated by the uids of the sending and receiving processes. If they match, the signal is sent. Some signals can be caught or ignored, which may help somewhat, but some cannot be caught or ignored (e.g., SIGKILL). I can't say whether this will change in 10.4, but up through 10.3, this is my understanding of how things work. This email sent to site_archiver(a)lists.apple.com

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Re: how to get the location of a program
by Kevin Van Vechten 20 Apr '05

20 Apr '05

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com - Kevin On Apr 19, 2005, at 5:42 PM, Peter Bierman wrote: Hi, Is there a way in OS X to get the full path of a program where it's being executed? I need to know the location where the user stores my program (along with some configuration files), to set up its running environment. Look at NSBundle You can get your app bundle path with NSString *path = [[NSBundle mainBundle] bundlePath]; _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… To be pedantic, look at CFBundle, which is available in Darwin and therefore on-topic for this list. At 4:10 PM -0700 4/19/05, w.o.b wrote: http://developer.apple.com/documentation/Cocoa/Reference/Foundation/ ObjC_classic/Classes/NSBundle.html For resources, use the other NSBundle APIs to find them. NSBundle can handle finding things by name, file extension, and localization. -pmb This email sent to site_archiver(a)lists.apple.com

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