Re:Re: Puzzled at "method_t method". :-(

Thanks, Henrik pal!

You have clarified all my doubts. :-)

Best regards,
George, Ma

----- Original Message -----From: Henrik Nordstrom
To: maer727@sohu.com ;squid-dev@squid-cache.org
Cc: squid-dev@squid-cache.org
Subject: Re: Puzzled at "method_t method". :-(
Sent: Wed Apr 17 15:05:30 CST 2002

> method_t is an enum, defined in enums.h.
>
> MD5 calculates a 16 bytes hash of the provided data.
>
> In: Any amount of binary data (bytes)
> Out: 16 bytes hash almost guaranteed to be unique for the specific
> combination of input data.
>
> The cast of method_t to a "unsigned char" is to convert it into a
> form suitable as platform independent input to MD5.
>
>
> The store key in Squid is
>
> Public keys:
>
> MD5((byte)method, url)
>
> Private keys:
>
> MD5(request id, method, url)
>
>
> The private key is only ever used within the same Squid process, but
> the public keys are used in digest exchanges and need to have a
> format that is identical on all platforms regardless of how the
> platform stores enum types in memory. As the number of possible
> method_t values is small, a single byte (unsigned char) is
> sufficient.
>
> Regards
> Henrik
>
>
> On Wednesday 17 April 2002 08:06, maer727@sohu.com wrote:
> > Hi pals,
> >
> > I want to know the function and meaning of "method_t method", but
> > I meet with troubles. Here is my trouble,
> >
> > In storeGetPublic, storeKeyPublic(uri, method) is called. The
> > second parameter of storeKeyPublic is "method" whose type is
> > method_t. I trace the calling chain. I find storeKeyPublic is
> > defined in store_key_md5.c, line 111. In this function, method_t
> > is changed to "unsigned char", using the following statement,
> > unsigned char m = (unsigned char) method;
> >
> > Then MD5Update is called using m. I also trace in MD5Update.
> > It is defined in md5.c, line 148. Then MD5_memcpy is called with
> > the same parameter. MD5_memcpy simply copies "input"
> > to "context->buffer[index]". Then MD5Transform is called using
> > "context->buffer[index]". I am puzzled here. I can not
> > trace anymore because I am not familiar with MD5 algorithm.
> >
> > So, if anyone can give me a simple explanation about the function
> > and meaning of "method_t method", I will be very thankful. :-)
> >
> > Best regards,
> > George, Ma
Received on Wed Apr 17 2002 - 01:49:58 MDT