Avoid header processing in my Virtual FS module

Question

I want to write a module that serves a huge virtual .wav file (also plan to add a virtual .ogg file in the future).

I know the size of the file (2Gb) and its fake modification time (2000-01-01 0:00:00) and I have a function to read portion of the file:

void virtwav_read(void *buf, ssize_t bufsz, uint32_t virtofs);

I want to hook the low-level file operations like stat, read, seek, etc. The standard apache code should take care of parsing the headers (including range requests, cache-related stuff) and generate Content-Type, Content-Length, ETag, Last-Modified, etc.

Parsing the request_rec.range is not a big deal. What worries me more is sending the right cache-related headers and HTTP 206 and 304 when approprate. I'm sure apache would do that better than my code.

I thought that setting request_rec.mtime and request_rec.clength would do the trick, but they don't seem to be output fields.

Lastly, VFS is surprisingly unpopular topic. I found only one ancient project http://apvfs.sourceforge.net/ dated 2003.

Here's my minimal module and its config. The right Content-Type is added by apache, but no ETag

LoadModule virtwav_module     modules/mod_virtwav.so
AddHandler virtwav-handler .wav

_

#include "apr_hash.h"
#include "ap_config.h"
#include "ap_provider.h"
#include "httpd.h"
#include "http_core.h"
#include "http_config.h"
#include "http_log.h"
#include "http_protocol.h"
#include "http_request.h"

#include <unistd.h> /* for sleep() */

static int example_handler(request_rec *r)
{
    if (!r->handler || strcmp(r->handler, "virtwav-handler")) return (DECLINED);

    //r->clength = 42;
    //r->mtime = apr_time_now();
    ap_rprintf(r, "clength: %" APR_INT64_T_FMT "\n", (apr_int64_t)r->clength);
    ap_rprintf(r, "mtime: %" APR_INT64_T_FMT "\n", (apr_int64_t)r->mtime);
    ap_rwrite("dummy", 5, r);
    ap_rflush(r);
    sleep(50);

    return OK;
}

static void register_hooks(apr_pool_t *pool)
{
    /* Create a hook in the request handler, so we get called when a request arrives */
    ap_hook_handler(example_handler, NULL, NULL, APR_HOOK_LAST);

    // ap_hook_dirwalk_stat ?
    // This hook allows modules to handle/emulate the apr_stat()

    // ap_hook_map_to_storage ?
    // This hook allow modules to set the per_dir_config based on their own
}

module AP_MODULE_DECLARE_DATA   virtwav_module =
{
    STANDARD20_MODULE_STUFF,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    register_hooks   /* Our hook registering function */
};

Avoid header processing in my Virtual FS module

0 Answers0