A few notes on general pedagogical style here. In the interest of conciseness, all structure declarations here are incomplete --- the real ones have more slots that I'm not telling you about. For the most part, these are reserved to one component of the server core or another, and should be altered by modules with caution. However, in some cases, they really are things I just haven't gotten around to yet. Welcome to the bleeding edge.
Finally, here's an outline, to give you some bare idea of what's coming up, and in what order:
SetEnv, which don't really fit well
elsewhere.OK.DECLINED. In this case,
the server behaves in all respects as if the handler simply
hadn't been there.*/* (i.e., a
wildcard MIME type specification). However, wildcard handlers
are only invoked if the server has already tried and failed to
find a more specific response handler for the MIME type of the
requested object (either none existed, or they all declined).
The handlers themselves are functions of one argument (a
request_rec structure. vide infra), which returns
an integer, as above.
ScriptAlias config file command. It's actually a
great deal more complicated than most modules, but if we're
going to have only one example, it might as well be the one
with its fingers in every place.
Let's begin with handlers. In order to handle the CGI
scripts, the module declares a response handler for them.
Because of ScriptAlias, it also has handlers for
the name translation phase (to recognize
ScriptAliased URIs), the type-checking phase (any
ScriptAliased request is typed as a CGI
script).
The module needs to maintain some per (virtual) server
information, namely, the ScriptAliases in effect;
the module structure therefore contains pointers to a functions
which builds these structures, and to another which combines
two of them (in case the main server and a virtual server both
have ScriptAliases declared).
Finally, this module contains code to handle the
ScriptAlias command itself. This particular module
only declares one command, but there could be more, so modules
have command tables which declare their commands, and
describe where they are permitted, and how they are to be
invoked.
A final note on the declared types of the arguments of some
of these commands: a pool is a pointer to a
resource pool structure; these are used by the server
to keep track of the memory which has been allocated, files
opened, etc., either to service a particular request,
or to handle the process of configuring itself. That way, when
the request is over (or, for the configuration pool, when the
server is restarting), the memory can be freed, and the files
closed, en masse, without anyone having to write
explicit code to track them all down and dispose of them. Also,
a cmd_parms structure contains various information
about the config file being read, and other status information,
which is sometimes of use to the function which processes a
config-file command (such as ScriptAlias). With no
further ado, the module itself:
/* Declarations of handlers. */
int translate_scriptalias (request_rec *);
int type_scriptalias (request_rec *);
int cgi_handler (request_rec *);
/* Subsidiary dispatch table for response-phase handlers, by MIME type */
handler_rec cgi_handlers[] = {
{ "application/x-httpd-cgi", cgi_handler },
{ NULL }
};
/* Declarations of routines to manipulate the module's configuration
* info. Note that these are returned, and passed in, as void *'s;
* the server core keeps track of them, but it doesn't, and can't,
* know their internal structure.
*/
void *make_cgi_server_config (pool *);
void *merge_cgi_server_config (pool *, void *, void *);
/* Declarations of routines to handle config-file commands */
extern char *script_alias(cmd_parms *, void *per_dir_config, char *fake,
char *real);
command_rec cgi_cmds[] = {
{ "ScriptAlias", script_alias, NULL, RSRC_CONF, TAKE2,
"a fakename and a realname"},
{ NULL }
};
module cgi_module = {
STANDARD_MODULE_STUFF,
NULL, /* initializer */
NULL, /* dir config creator */
NULL, /* dir merger --- default is to override */
make_cgi_server_config, /* server config */
merge_cgi_server_config, /* merge server config */
cgi_cmds, /* command table */
cgi_handlers, /* handlers */
translate_scriptalias, /* filename translation */
NULL, /* check_user_id */
NULL, /* check auth */
NULL, /* check access */
type_scriptalias, /* type_checker */
NULL, /* fixups */
NULL, /* logger */
NULL /* header parser */
};
request_rec
structure. This structure describes a particular request which
has been made to the server, on behalf of a client. In most
cases, each connection to the client generates only one
request_rec structure.
request_recrequest_rec contains pointers to a resource
pool which will be cleared when the server is finished handling
the request; to structures containing per-server and
per-connection information, and most importantly, information
on the request itself.
The most important such information is a small set of character strings describing attributes of the object being requested, including its URI, filename, content-type and content-encoding (these being filled in by the translation and type-check handlers which handle the request, respectively).
Other commonly used data items are tables giving the MIME
headers on the client's original request, MIME headers to be
sent back with the response (which modules can add to at will),
and environment variables for any subprocesses which are
spawned off in the course of servicing the request. These
tables are manipulated using the ap_table_get and
ap_table_set routines.
Note that the Content-type header value cannot be set by module content-handlers using the ap_table_*() routines. Rather, it is set by pointing the content_type field in the request_rec structure to an appropriate string. E.g.,Finally, there are pointers to two data structures which, in turn, point to per-module configuration structures. Specifically, these hold pointers to the data structures which the module has built to describe the way it has been configured to operate in a given directory (viar->content_type = "text/html";
.htaccess
files or <Directory> sections), for private
data it has built in the course of servicing the request (so
modules' handlers for one phase can pass `notes' to their
handlers for other phases). There is another such configuration
vector in the server_rec data structure pointed to
by the request_rec, which contains per (virtual)
server configuration data.
Here is an abridged declaration, giving the fields most commonly used:
struct request_rec {
pool *pool;
conn_rec *connection;
server_rec *server;
/* What object is being requested */
char *uri;
char *filename;
char *path_info;
char *args; /* QUERY_ARGS, if any */
struct stat finfo; /* Set by server core;
* st_mode set to zero if no such file */
char *content_type;
char *content_encoding;
/* MIME header environments, in and out. Also, an array containing
* environment variables to be passed to subprocesses, so people can
* write modules to add to that environment.
*
* The difference between headers_out and err_headers_out is that
* the latter are printed even on error, and persist across internal
* redirects (so the headers printed for ErrorDocument handlers will
* have them).
*/
table *headers_in;
table *headers_out;
table *err_headers_out;
table *subprocess_env;
/* Info about the request itself... */
int header_only; /* HEAD request, as opposed to GET */
char *protocol; /* Protocol, as given to us, or HTTP/0.9 */
char *method; /* GET, HEAD, POST, etc. */
int method_number; /* M_GET, M_POST, etc. */
/* Info for logging */
char *the_request;
int bytes_sent;
/* A flag which modules can set, to indicate that the data being
* returned is volatile, and clients should be told not to cache it.
*/
int no_cache;
/* Various other config info which may change with .htaccess files
* These are config vectors, with one void* pointer for each module
* (the thing pointed to being the module's business).
*/
void *per_dir_config; /* Options set in config files, etc. */
void *request_config; /* Notes on *this* request */
};
request_rec structures are built by reading
an HTTP request from a client, and filling in the fields.
However, there are a few exceptions:
*.var file), or a CGI script
which returned a local `Location:', then the resource which
the user requested is going to be ultimately located by some
URI other than what the client originally supplied. In this
case, the server does an internal redirect,
constructing a new request_rec for the new URI,
and processing it almost exactly as if the client had
requested the new URI directly.ErrorDocument is in scope, the same internal
redirect machinery comes into play.Such handlers can construct a sub-request,
using the functions ap_sub_req_lookup_file,
ap_sub_req_lookup_uri, and
ap_sub_req_method_uri; these construct a new
request_rec structure and processes it as you
would expect, up to but not including the point of actually
sending a response. (These functions skip over the access
checks if the sub-request is for a file in the same
directory as the original request).
(Server-side includes work by building sub-requests and
then actually invoking the response handler for them, via
the function ap_run_sub_req).
request_rec, has to return an
int to indicate what happened. That can either be
REDIRECT,
then the module should put a Location in the
request's headers_out, to indicate where the
client should be redirected to.
request_rec structure (or, in the
case of access checkers, simply by returning the correct error
code). However, response handlers have to actually send a
request back to the client.
They should begin by sending an HTTP response header, using
the function ap_send_http_header. (You don't have
to do anything special to skip sending the header for HTTP/0.9
requests; the function figures out on its own that it shouldn't
do anything). If the request is marked
header_only, that's all they should do; they
should return after that, without attempting any further
output.
Otherwise, they should produce a request body which responds
to the client as appropriate. The primitives for this are
ap_rputc and ap_rprintf, for
internally generated output, and ap_send_fd, to
copy the contents of some FILE * straight to the
client.
At this point, you should more or less understand the
following piece of code, which is the handler which handles
GET requests which have no more specific handler;
it also shows how conditional GETs can be handled,
if it's desirable to do so in a particular response handler ---
ap_set_last_modified checks against the
If-modified-since value supplied by the client, if
any, and returns an appropriate code (which will, if nonzero,
be USE_LOCAL_COPY). No similar considerations apply for
ap_set_content_length, but it returns an error
code for symmetry.
int default_handler (request_rec *r)
{
int errstatus;
FILE *f;
if (r->method_number != M_GET) return DECLINED;
if (r->finfo.st_mode == 0) return NOT_FOUND;
if ((errstatus = ap_set_content_length (r, r->finfo.st_size)) {
return errstatus;
}
r->mtime = r->finfo.st_mtime;
ap_set_last_modified (r);
f = ap_pfopen (r->pool, r->filename, "r");
if (f == NULL) {
ap_log_rerror(APLOG_MARK, APLOG_ERR, r,
"file permissions deny server access: %s", r->filename);
return FORBIDDEN;
}
ap_soft_timeout ("send", r);
ap_send_http_header (r);
if (!r->header_only) ap_send_fd (f, r);
ap_pfclose (r->pool, f);
ap_kill_timeout (r);
return OK;
}
Finally, if all of this is too much of a challenge, there are a
few ways out of it. First off, as shown above, a response
handler which has not yet produced any output can simply return
an error code, in which case the server will automatically
produce an error response. Secondly, it can punt to some other
handler by invoking ap_internal_redirect, which is
how the internal redirection machinery discussed above is
invoked. A response handler which has internally redirected
should always return OK.
(Invoking ap_internal_redirect from handlers
which are not response handlers will lead to serious
confusion).
ap_auth_type,
ap_auth_name, and ap_requires.ap_get_basic_auth_pw, which sets the
connection->user structure field
automatically, and ap_note_basic_auth_failure,
which arranges for the proper WWW-Authenticate:
header to be sent back).request_rec
structures which are threaded through the
r->prev and r->next pointers.
The request_rec which is passed to the logging
handlers in such cases is the one which was originally built
for the initial request from the client; note that the
bytes_sent field will only be correct in the last request in
the chain (the one for which a response was actually sent).
One of the problems of writing and designing a server-pool server is that of preventing leakage, that is, allocating resources (memory, open files, etc.), without subsequently releasing them. The resource pool machinery is designed to make it easy to prevent this from happening, by allowing resource to be allocated in such a way that they are automatically released when the server is done with them.
The way this works is as follows: the memory which is allocated, file opened, etc., to deal with a particular request are tied to a resource pool which is allocated for the request. The pool is a data structure which itself tracks the resources in question.
When the request has been processed, the pool is cleared. At that point, all the memory associated with it is released for reuse, all files associated with it are closed, and any other clean-up functions which are associated with the pool are run. When this is over, we can be confident that all the resource tied to the pool have been released, and that none of them have leaked.
Server restarts, and allocation of memory and resources for per-server configuration, are handled in a similar way. There is a configuration pool, which keeps track of resources which were allocated while reading the server configuration files, and handling the commands therein (for instance, the memory that was allocated for per-server module configuration, log files and other files that were opened, and so forth). When the server restarts, and has to reread the configuration files, the configuration pool is cleared, and so the memory and file descriptors which were taken up by reading them the last time are made available for reuse.
It should be noted that use of the pool machinery isn't
generally obligatory, except for situations like logging
handlers, where you really need to register cleanups to make
sure that the log file gets closed when the server restarts
(this is most easily done by using the function ap_pfopen, which also arranges
for the underlying file descriptor to be closed before any
child processes, such as for CGI scripts, are
execed), or in case you are using the timeout
machinery (which isn't yet even documented here). However,
there are two benefits to using it: resources allocated to a
pool never leak (even if you allocate a scratch string, and
just forget about it); also, for memory allocation,
ap_palloc is generally faster than
malloc.
We begin here by describing how memory is allocated to pools, and then discuss how other resources are tracked by the resource pool machinery.
Memory is allocated to pools by calling the function
ap_palloc, which takes two arguments, one being a
pointer to a resource pool structure, and the other being the
amount of memory to allocate (in chars). Within
handlers for handling requests, the most common way of getting
a resource pool structure is by looking at the
pool slot of the relevant
request_rec; hence the repeated appearance of the
following idiom in module code:
int my_handler(request_rec *r)
{
struct my_structure *foo;
...
foo = (foo *)ap_palloc (r->pool, sizeof(my_structure));
}
Note that there is no ap_pfree ---
ap_palloced memory is freed only when the
associated resource pool is cleared. This means that
ap_palloc does not have to do as much accounting
as malloc(); all it does in the typical case is to
round up the size, bump a pointer, and do a range check.
(It also raises the possibility that heavy use of
ap_palloc could cause a server process to grow
excessively large. There are two ways to deal with this, which
are dealt with below; briefly, you can use malloc,
and try to be sure that all of the memory gets explicitly
freed, or you can allocate a sub-pool of the main
pool, allocate your memory in the sub-pool, and clear it out
periodically. The latter technique is discussed in the section
on sub-pools below, and is used in the directory-indexing code,
in order to avoid excessive storage allocation when listing
directories with thousands of files).
There are functions which allocate initialized memory, and
are frequently useful. The function ap_pcalloc has
the same interface as ap_palloc, but clears out
the memory it allocates before it returns it. The function
ap_pstrdup takes a resource pool and a char
* as arguments, and allocates memory for a copy of the
string the pointer points to, returning a pointer to the copy.
Finally ap_pstrcat is a varargs-style function,
which takes a pointer to a resource pool, and at least two
char * arguments, the last of which must be
NULL. It allocates enough memory to fit copies of
each of the strings, as a unit; for instance:
ap_pstrcat (r->pool, "foo", "/", "bar", NULL);
returns a pointer to 8 bytes worth of memory, initialized to
"foo/bar".
A pool is really defined by its lifetime more than anything else. There are some static pools in http_main which are passed to various non-http_main functions as arguments at opportune times. Here they are:
For almost everything folks do, r->pool is the pool to use. But you can see how other lifetimes, such as pchild, are useful to some modules... such as modules that need to open a database connection once per child, and wish to clean it up when the child dies.
You can also see how some bugs have manifested themself, such as setting connection->user to a value from r->pool -- in this case connection exists for the lifetime of ptrans, which is longer than r->pool (especially if r->pool is a subrequest!). So the correct thing to do is to allocate from connection->pool.
And there was another interesting bug in mod_include/mod_cgi. You'll see in those that they do this test to decide if they should use r->pool or r->main->pool. In this case the resource that they are registering for cleanup is a child process. If it were registered in r->pool, then the code would wait() for the child when the subrequest finishes. With mod_include this could be any old #include, and the delay can be up to 3 seconds... and happened quite frequently. Instead the subprocess is registered in r->main->pool which causes it to be cleaned up when the entire request is done -- i.e., after the output has been sent to the client and logging has happened.
As indicated above, resource pools are also used to track
other sorts of resources besides memory. The most common are
open files. The routine which is typically used for this is
ap_pfopen, which takes a resource pool and two
strings as arguments; the strings are the same as the typical
arguments to fopen, e.g.,
...
FILE *f = ap_pfopen (r->pool, r->filename, "r");
if (f == NULL) { ... } else { ... }
There is also a ap_popenf routine, which
parallels the lower-level open system call. Both
of these routines arrange for the file to be closed when the
resource pool in question is cleared.
Unlike the case for memory, there are functions to
close files allocated with ap_pfopen, and
ap_popenf, namely ap_pfclose and
ap_pclosef. (This is because, on many systems, the
number of files which a single process can have open is quite
limited). It is important to use these functions to close files
allocated with ap_pfopen and
ap_popenf, since to do otherwise could cause fatal
errors on systems such as Linux, which react badly if the same
FILE* is closed more than once.
(Using the close functions is not mandatory,
since the file will eventually be closed regardless, but you
should consider it in cases where your module is opening, or
could open, a lot of files).
More text goes here. Describe the the cleanup primitives in
terms of which the file stuff is implemented; also,
spawn_process.
Pool cleanups live until clear_pool() is called: clear_pool(a) recursively calls destroy_pool() on all subpools of a; then calls all the cleanups for a; then releases all the memory for a. destroy_pool(a) calls clear_pool(a) and then releases the pool structure itself. i.e., clear_pool(a) doesn't delete a, it just frees up all the resources and you can start using it again immediately.
ap_palloc() and
the associated primitives may result in undesirably profligate
resource allocation. You can deal with such a case by creating
a sub-pool, allocating within the sub-pool rather than
the main pool, and clearing or destroying the sub-pool, which
releases the resources which were associated with it. (This
really is a rare situation; the only case in which it
comes up in the standard module set is in case of listing
directories, and then only with very large
directories. Unnecessary use of the primitives discussed here
can hair up your code quite a bit, with very little gain).
The primitive for creating a sub-pool is
ap_make_sub_pool, which takes another pool (the
parent pool) as an argument. When the main pool is cleared, the
sub-pool will be destroyed. The sub-pool may also be cleared or
destroyed at any time, by calling the functions
ap_clear_pool and ap_destroy_pool,
respectively. (The difference is that
ap_clear_pool frees resources associated with the
pool, while ap_destroy_pool also deallocates the
pool itself. In the former case, you can allocate new resources
within the pool, and clear it again, and so forth; in the
latter case, it is simply gone).
One final note --- sub-requests have their own resource
pools, which are sub-pools of the resource pool for the main
request. The polite way to reclaim the resources associated
with a sub request which you have allocated (using the
ap_sub_req_... functions) is
ap_destroy_sub_req, which frees the resource pool.
Before calling this function, be sure to copy anything that you
care about which might be allocated in the sub-request's
resource pool into someplace a little less volatile (for
instance, the filename in its request_rec
structure).
(Again, under most circumstances, you shouldn't feel obliged
to call this function; only 2K of memory or so are allocated
for a typical sub request, and it will be freed anyway when the
main request pool is cleared. It is only when you are
allocating many, many sub-requests for a single main request
that you should seriously consider the
ap_destroy_... functions).
However, just giving the modules command tables is not
enough to divorce them completely from the server core. The
server has to remember the commands in order to act on them
later. That involves maintaining data which is private to the
modules, and which can be either per-server, or per-directory.
Most things are per-directory, including in particular access
control and authorization information, but also information on
how to determine file types from suffixes, which can be
modified by AddType and DefaultType
directives, and so forth. In general, the governing philosophy
is that anything which can be made configurable by
directory should be; per-server information is generally used
in the standard set of modules for information like
Aliases and Redirects which come into
play before the request is tied to a particular place in the
underlying file system.
Another requirement for emulating the NCSA server is being
able to handle the per-directory configuration files, generally
called .htaccess files, though even in the NCSA
server they can contain directives which have nothing at all to
do with access control. Accordingly, after URI -> filename
translation, but before performing any other phase, the server
walks down the directory hierarchy of the underlying
filesystem, following the translated pathname, to read any
.htaccess files which might be present. The
information which is read in then has to be merged
with the applicable information from the server's own config
files (either from the <Directory> sections
in access.conf, or from defaults in
srm.conf, which actually behaves for most purposes
almost exactly like <Directory />).
Finally, after having served a request which involved
reading .htaccess files, we need to discard the
storage allocated for handling them. That is solved the same
way it is solved wherever else similar problems come up, by
tying those structures to the per-transaction resource
pool.
mod_mime.c, which defines the file typing handler
which emulates the NCSA server's behavior of determining file
types from suffixes. What we'll be looking at, here, is the
code which implements the AddType and
AddEncoding commands. These commands can appear in
.htaccess files, so they must be handled in the
module's private per-directory data, which in fact, consists of
two separate tables for MIME types and encoding
information, and is declared as follows:
typedef struct {
table *forced_types; /* Additional AddTyped stuff */
table *encoding_types; /* Added with AddEncoding... */
} mime_dir_config;
When the server is reading a configuration file, or
<Directory> section, which includes one of
the MIME module's commands, it needs to create a
mime_dir_config structure, so those commands have
something to act on. It does this by invoking the function it
finds in the module's `create per-dir config slot', with two
arguments: the name of the directory to which this
configuration information applies (or NULL for
srm.conf), and a pointer to a resource pool in
which the allocation should happen.
(If we are reading a .htaccess file, that
resource pool is the per-request resource pool for the request;
otherwise it is a resource pool which is used for configuration
data, and cleared on restarts. Either way, it is important for
the structure being created to vanish when the pool is cleared,
by registering a cleanup on the pool if necessary).
For the MIME module, the per-dir config creation function
just ap_pallocs the structure above, and a creates
a couple of tables to fill it. That looks like
this:
void *create_mime_dir_config (pool *p, char *dummy)
{
mime_dir_config *new =
(mime_dir_config *) ap_palloc (p, sizeof(mime_dir_config));
new->forced_types = ap_make_table (p, 4);
new->encoding_types = ap_make_table (p, 4);
return new;
}
Now, suppose we've just read in a .htaccess file.
We already have the per-directory configuration structure for
the next directory up in the hierarchy. If the
.htaccess file we just read in didn't have any
AddType or AddEncoding commands, its
per-directory config structure for the MIME module is still
valid, and we can just use it. Otherwise, we need to merge the
two structures somehow.
To do that, the server invokes the module's per-directory config merge function, if one is present. That function takes three arguments: the two structures being merged, and a resource pool in which to allocate the result. For the MIME module, all that needs to be done is overlay the tables from the new per-directory config structure with those from the parent:
void *merge_mime_dir_configs (pool *p, void *parent_dirv, void *subdirv)
{
mime_dir_config *parent_dir = (mime_dir_config *)parent_dirv;
mime_dir_config *subdir = (mime_dir_config *)subdirv;
mime_dir_config *new =
(mime_dir_config *)ap_palloc (p, sizeof(mime_dir_config));
new->forced_types = ap_overlay_tables (p, subdir->forced_types,
parent_dir->forced_types);
new->encoding_types = ap_overlay_tables (p, subdir->encoding_types,
parent_dir->encoding_types);
return new;
}
As a note --- if there is no per-directory merge function
present, the server will just use the subdirectory's
configuration info, and ignore the parent's. For some modules,
that works just fine (e.g., for the includes module,
whose per-directory configuration information consists solely
of the state of the XBITHACK), and for those
modules, you can just not declare one, and leave the
corresponding structure slot in the module itself
NULL.
AddType and AddEncoding commands. To
find commands, the server looks in the module's command
table. That table contains information on how many
arguments the commands take, and in what formats, where it is
permitted, and so forth. That information is sufficient to
allow the server to invoke most command-handling functions with
pre-parsed arguments. Without further ado, let's look at the
AddType command handler, which looks like this
(the AddEncoding command looks basically the same,
and won't be shown here):
char *add_type(cmd_parms *cmd, mime_dir_config *m, char *ct, char *ext)
{
if (*ext == '.') ++ext;
ap_table_set (m->forced_types, ext, ct);
return NULL;
}
This command handler is unusually simple. As you can see, it
takes four arguments, two of which are pre-parsed arguments,
the third being the per-directory configuration structure for
the module in question, and the fourth being a pointer to a
cmd_parms structure. That structure contains a
bunch of arguments which are frequently of use to some, but not
all, commands, including a resource pool (from which memory can
be allocated, and to which cleanups should be tied), and the
(virtual) server being configured, from which the module's
per-server configuration data can be obtained if required.
Another way in which this particular command handler is
unusually simple is that there are no error conditions which it
can encounter. If there were, it could return an error message
instead of NULL; this causes an error to be
printed out on the server's stderr, followed by a
quick exit, if it is in the main config files; for a
.htaccess file, the syntax error is logged in the
server error log (along with an indication of where it came
from), and the request is bounced with a server error response
(HTTP error status, code 500).
The MIME module's command table has entries for these commands, which look like this:
command_rec mime_cmds[] = {
{ "AddType", add_type, NULL, OR_FILEINFO, TAKE2,
"a mime type followed by a file extension" },
{ "AddEncoding", add_encoding, NULL, OR_FILEINFO, TAKE2,
"an encoding (e.g., gzip), followed by a file extension" },
{ NULL }
};
The entries in these tables are:
(void *) pointer, which is passed in the
cmd_parms structure to the command handler ---
this is useful in case many similar commands are handled by
the same function.AllowOverride option, and an additional mask
bit, RSRC_CONF, indicating that the command may
appear in the server's own config files, but not in
any .htaccess file.TAKE2 indicates two pre-parsed arguments. Other
options are TAKE1, which indicates one
pre-parsed argument, FLAG, which indicates that
the argument should be On or Off,
and is passed in as a boolean flag, RAW_ARGS,
which causes the server to give the command the raw, unparsed
arguments (everything but the command name itself). There is
also ITERATE, which means that the handler looks
the same as TAKE1, but that if multiple
arguments are present, it should be called multiple times,
and finally ITERATE2, which indicates that the
command handler looks like a TAKE2, but if more
arguments are present, then it should be called multiple
times, holding the first argument constant.NULL).request_rec's per-directory configuration
vector by using the ap_get_module_config function.
int find_ct(request_rec *r)
{
int i;
char *fn = ap_pstrdup (r->pool, r->filename);
mime_dir_config *conf = (mime_dir_config *)
ap_get_module_config(r->per_dir_config, &mime_module);
char *type;
if (S_ISDIR(r->finfo.st_mode)) {
r->content_type = DIR_MAGIC_TYPE;
return OK;
}
if((i=ap_rind(fn,'.')) < 0) return DECLINED;
++i;
if ((type = ap_table_get (conf->encoding_types, &fn[i])))
{
r->content_encoding = type;
/* go back to previous extension to try to use it as a type */
fn[i-1] = '\0';
if((i=ap_rind(fn,'.')) < 0) return OK;
++i;
}
if ((type = ap_table_get (conf->forced_types, &fn[i])))
{
r->content_type = type;
}
return OK;
}
The only substantial difference is that when a command needs
to configure the per-server private module data, it needs to go
to the cmd_parms data to get at it. Here's an
example, from the alias module, which also indicates how a
syntax error can be returned (note that the per-directory
configuration argument to the command handler is declared as a
dummy, since the module doesn't actually have per-directory
config data):
char *add_redirect(cmd_parms *cmd, void *dummy, char *f, char *url)
{
server_rec *s = cmd->server;
alias_server_conf *conf = (alias_server_conf *)
ap_get_module_config(s->module_config,&alias_module);
alias_entry *new = ap_push_array (conf->redirects);
if (!ap_is_url (url)) return "Redirect to non-URL";
new->fake = f; new->real = url;
return NULL;
}