[squid-dev] How Squid parse the configuration file?

[Alex Rousskov]

On 02/21/2017 08:22 PM, 周书林 wrote:

> And one more question, is there any checking mechanism for validity of
> config value?

Sure, most parsers check the tokens/strings they parse. The checks are
specific to the directive type and are often not comprehensive (e.g.,
may miss garbage after a valid token).


> For example, if config option "maximum_object_size_in_memory" is set as
> 10000, how to check if this value is valid?

Sorry, I do not understand the question. To find how existing parsers
check values, just examine the corresponding parser code.

For example, my previous email shows how to find the
maximum_object_size_in_memory parsing function (called parse_b_size_t).
Examining that function will lead you to parseBytesLine() and the
functions/methods it calls, including syntax checking code.


HTH,

Alex.


> 2017-02-22 0:52 GMT+08:00 Alex Rousskov:
> 
>     On 02/21/2017 01:15 AM, 周书林 wrote:
>     > I found the src/cf.data.pre file, and read the content. But I still want
>     > to know how squid use this file to build the connection between the
>     > config file and the source code.
> 
>     As you already know, the parser is generated. The generated code either
>     places parsed values directly into the global Config object or calls
>     some helper functions that update the global state. (Updating global
>     state during parsing is very wrong but that is a different story.)
> 
>     If you want to see the actual generated parsing code for a given
>     squid.conf directive, just grep for it! For example,
> 
>       $ fgrep -A5 -RI maximum_object_size_in_memory src
> 
>     will point you to the following code in src/cf_parser.cci:
> 
>     > src/cf_parser.cci:    if (!strcmp(token,
>     "maximum_object_size_in_memory")) {
>     > src/cf_parser.cci:        cfg_directive =
>     "maximum_object_size_in_memory";
>     > src/cf_parser.cci-       
>     parse_b_size_t(&Config.Store.maxInMemObjSize);
>     > src/cf_parser.cci-        cfg_directive = NULL;
>     > src/cf_parser.cci-        return 1;
> 
> 
>     How was that code generated? Search for "cfg_directive = NULL" to find
>     the parser generator code in the repository:
> 
>       $ bzr grep 'cfg_directive = NULL'
> 
>     > src/cf_gen.cc:    fout << "        cfg_directive = NULL;" <<
>     std::endl;
> 
>     which will point you to the Entry::genParseAlias() method.
> 
> 
>     HTH,
> 
>     Alex.
> 
> 
> 
>     > 2017-01-13 22:14 GMT+08:00 Stuart Henderson:
>     >
>     >     On 2017-01-13, 周书林 <zhoushulin1992 at gmail.com
>     <mailto:zhoushulin1992 at gmail.com>
>     >     <mailto:zhoushulin1992 at gmail.com <mailto:zhoushulin1992 at gmail.com>>> wrote:
>     >     > Why some of the configuration directives in official website cannot find in
>     >     > the source code? Some could find a relevant program variable in Class
>     >     > SquidConfig, while majority of the configuration directives cannot be found
>     >     > in the source code, for example , directive "announce_port".
>     >     > So how does Squid parse the configuration file of Users, and use them in
>     >     > the source code?
>     >
>     >     The parser, sample config, etc, are all generated from src/cf.data.pre.
>     >