[Pharo-project] OpenSSL - a couple of questions
Hello all, Do you have any thoughts on whether a wrapper for OpenSSL should be a plugin or based on FFI/Alien? Would blocking calls be best handled by using OS threads or non-blocking sockets? In either case, I would envision using semaphores to block only the calling Process instance. Loosely related, can you understand (and explain to me - perhaps the hard part<g>) the following syntax: void (*CRYPTO_get_locking_callback(void))(int mode,int type,const char *file,int line); It looks to me like a shotgun wedding of an incomplete typedef of a function pointer type and a function prototype. Any ideas? Bill
Schwab,Wilhelm K <bschwab@...> writes:
Hello all,
Do you have any thoughts on whether a wrapper for OpenSSL should be a plugin
or based on FFI/Alien? Would
blocking calls be best handled by using OS threads or non-blocking sockets? In either case, I would envision using semaphores to block only the calling Process instance.
Loosely related, can you understand (and explain to me - perhaps the hard part<g>) the following syntax:
void (*CRYPTO_get_locking_callback(void))(int mode,int type,const char *file,int line);
It looks to me like a shotgun wedding of an incomplete typedef of a function pointer type and a function prototype. Any ideas?
Bill
Doesn't the CRYPTO_get_locking_callback function returns a pointer to a function with no argument (void) and no return value (void), or something like that ? Nicolas
Nicolas, Fair enough, but it's the rest of the expression that bothers me - what does the second argument sequence do? Bill -----Original Message----- From: pharo-project-bounces@lists.gforge.inria.fr [mailto:pharo-project-bounces@lists.gforge.inria.fr] On Behalf Of Nicolas Cellier Sent: Tuesday, March 10, 2009 3:23 PM To: pharo-project@lists.gforge.inria.fr Subject: Re: [Pharo-project] OpenSSL - a couple of questions Schwab,Wilhelm K <bschwab@...> writes:
Hello all,
Do you have any thoughts on whether a wrapper for OpenSSL should be a plugin
or based on FFI/Alien? Would
blocking calls be best handled by using OS threads or non-blocking sockets? In either case, I would envision using semaphores to block only the calling Process instance.
Loosely related, can you understand (and explain to me - perhaps the hard part<g>) the following syntax:
void (*CRYPTO_get_locking_callback(void))(int mode,int type,const char *file,int line);
It looks to me like a shotgun wedding of an incomplete typedef of a function pointer type and a function prototype. Any ideas?
Bill
Doesn't the CRYPTO_get_locking_callback function returns a pointer to a function with no argument (void) and no return value (void), or something like that ? Nicolas _______________________________________________ Pharo-project mailing list Pharo-project@lists.gforge.inria.fr http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
Schwab,Wilhelm K <bschwab@...> writes:
Nicolas,
Fair enough, but it's the rest of the expression that bothers me - what does
the second argument sequence do?
Bill
I'm not sure I understand the question, but i'll tell how I read this syntax: CRYPTO_get_locking_callback is a function taking four arguments (int mode,int type,const char *file,int line). CRYPTO_get_locking_callback will return a pointer to a function, say F. This function F does take no argument and return no result. void F(void). Nicolas
-----Original Message----- From: pharo-project-bounces@... [mailto:pharo-project-bounces@...] On Behalf Of Nicolas Cellier Sent: Tuesday, March 10, 2009 3:23 PM To: pharo-project@... Subject: Re: [Pharo-project] OpenSSL - a couple of questions
Schwab,Wilhelm K <bschwab@...> writes:
gmane want me to snip...
Nicolas, I would read void (*CRYPTO_get_locking_callback)(int mode,int type,const char *file,int line) as a pointer to a function taking four arguments and returning nothing. That is _not_ what OpenSSL defines. With the added void argument, it looks to me like the callback takes no arguments and returns nothing. I would expect what you described to look more like (void* (*CRYPTO_get_locking_callback)(int mode,int type,const char *file,int line)) F(void); I prefer to "hide" function pointers using type definitions to make them clear. You mention a function named F, but the given syntax does not name it. It does look like any prototype I have seen, and it's not a typedef, unless that is happening implicitly?? Bill -----Original Message----- From: pharo-project-bounces@lists.gforge.inria.fr [mailto:pharo-project-bounces@lists.gforge.inria.fr] On Behalf Of Nicolas Cellier Sent: Tuesday, March 10, 2009 5:14 PM To: pharo-project@lists.gforge.inria.fr Subject: Re: [Pharo-project] OpenSSL - a couple of questions Schwab,Wilhelm K <bschwab@...> writes:
Nicolas,
Fair enough, but it's the rest of the expression that bothers me - what does
the second argument sequence do?
Bill
I'm not sure I understand the question, but i'll tell how I read this syntax: CRYPTO_get_locking_callback is a function taking four arguments (int mode,int type,const char *file,int line). CRYPTO_get_locking_callback will return a pointer to a function, say F. This function F does take no argument and return no result. void F(void). Nicolas
-----Original Message----- From: pharo-project-bounces@... [mailto:pharo-project-bounces@...] On Behalf Of Nicolas Cellier Sent: Tuesday, March 10, 2009 3:23 PM To: pharo-project@... Subject: Re: [Pharo-project] OpenSSL - a couple of questions
Schwab,Wilhelm K <bschwab@...> writes:
gmane want me to snip... _______________________________________________ Pharo-project mailing list Pharo-project@lists.gforge.inria.fr http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
Schwab,Wilhelm K <bschwab@...> writes:
Nicolas,
I would read
void (*CRYPTO_get_locking_callback)(int mode,int type,const char *file,int line)
as a pointer to a function taking four arguments and returning nothing. That is _not_ what OpenSSL defines. With the added void argument, it looks to
me like the callback takes no
arguments and returns nothing.
I would expect what you described to look more like
(void* (*CRYPTO_get_locking_callback)(int mode,int type,const char *file,int line)) F(void);
I prefer to "hide" function pointers using type definitions to make them clear. You mention a function named F, but the given syntax does not name it. It does look like any prototype I have seen, and it's not a typedef, unless that is happening implicitly??
Bill
I introduced a named return value F just for trying to explain. F is the return value, so it is anonymous. This is a valid syntax for a function returning a pointer to a function. But of course my explanation was plain wrong... Sorry. I inverted the arguments... So here is a better explanation. 0) CRYPTO_get_locking_callback is the name of the function. It is not a typedef. 1) CRYPTO_get_locking_callback is a function taking no argument (void) 2) it returns a pointer to a function which 2.a) return nothing (void) 2.b) takes four arguments int mode,int type,const char *file,int line)) I can read C, but const and function pointer are ones I will fail to parse 50% of time... Feel like I must not be alone... This is C anyway... It's not that easy to speak to a dumb compiler, so that he finally understands how to optimize that code! And not to optimize that code is of course not an option... Nicolas
-----Original Message----- From: pharo-project-bounces@... [mailto:pharo-project-bounces@...] On Behalf Of Nicolas Cellier Sent: Tuesday, March 10, 2009 5:14 PM To: pharo-project@... Subject: Re: [Pharo-project] OpenSSL - a couple of questions
Schwab,Wilhelm K <bschwab@...> writes:
Nicolas,
Fair enough, but it's the rest of the expression that bothers me - what does
the second argument sequence do?
Bill
I'm not sure I understand the question, but i'll tell how I read this syntax:
CRYPTO_get_locking_callback is a function taking four arguments (int mode,int type,const char *file,int line).
CRYPTO_get_locking_callback will return a pointer to a function, say F. This function F does take no argument and return no result. void F(void).
Nicolas
-----Original Message----- From: pharo-project-bounces@... [mailto:pharo-project-bounces@...] On Behalf Of Nicolas Cellier Sent: Tuesday, March 10, 2009 3:23 PM To: pharo-project@... Subject: Re: [Pharo-project] OpenSSL - a couple of questions
Schwab,Wilhelm K <bschwab@...> writes:
gmane want me to snip...
_______________________________________________ Pharo-project mailing list Pharo-project@... http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
Nicolas, I think I am starting to get it. It is a prototype for CRYPTO_get_locking_callback() ?? It appears that ( *funcName(args) ) signifies that funcName() returns a pointer to the function type "wrapped around" it? In this case void NoName(int mode, int type, const char* file, int line). I think I just found this described on pg 169-170 of my copy of Lippman's C++ Primer. Why people do not consistently use typedefs for this type of thing is beyond me ~:( Thanks! Bill
void (*CRYPTO_get_locking_callback(void))(int mode,int type,const char *file,int line);
-----Original Message----- From: pharo-project-bounces@lists.gforge.inria.fr [mailto:pharo-project-bounces@lists.gforge.inria.fr] On Behalf Of Nicolas Cellier Sent: Tuesday, March 10, 2009 7:23 PM To: pharo-project@lists.gforge.inria.fr Subject: Re: [Pharo-project] OpenSSL - a couple of questions So here is a better explanation. 0) CRYPTO_get_locking_callback is the name of the function. It is not a typedef. 1) CRYPTO_get_locking_callback is a function taking no argument (void) 2) it returns a pointer to a function which 2.a) return nothing (void) 2.b) takes four arguments int mode,int type,const char *file,int line)) I can read C, but const and function pointer are ones I will fail to parse 50% of time... Feel like I must not be alone... This is C anyway... It's not that easy to speak to a dumb compiler, so that he finally understands how to optimize that code! And not to optimize that code is of course not an option... Nicolas
participants (2)
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Nicolas Cellier -
Schwab,Wilhelm K