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Why filters?. Very flexible design Allows one module to modify the data that another module produces Finally, CGI's that output SSI tags A module that puts header and footer information on each page Many many more possibilities. Basic filters in 2.0. Core - PowerPoint PPT Presentation
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Why filters?
Very flexible design
Allows one module to modify the data that another module produces Finally, CGI's that output SSI tags A module that puts header and footer
information on each page Many many more possibilities
Basic filters in 2.0
Core core_input_filter (read from network) core_output_filter (write to network) byterange_filter (send partial result) content_length_filter (compute C-L) sub-request_filter (remove extra EOS) OLD_WRITE (buffer for ap_r* funcs)
Basic filters in 2.0
HTTPD HTTP_IN (header/body determination) HTTP_HEADER (send headers) CHUNK (send data in chunks) DECHUNK (read chunked body from
client)
Modules SSI_filter (parse files for SSI tags)
Basic filters in 2.0
Modules SSI_filter (parse files for SSI tags) External (run external programs) Charset-encoding (translate between
charsets)
Possible Additional Filters
SSL (in process of being written, input and output)
Header/Footer (basic attempt in presentation and handouts)
Cache (cache data in output filter, send it later from cache_handler, basic attempt in CVS)
Handlers and filters
Handlers are the first filter in the chain Filters use functions like ap_fwrite Handlers use ap_rwrite
Handlers Generate data from nothing
Filters modify data passed to them from handlers, and other filters
Buckets and brigades
Bucket
File_bucket
socket_bucketshared_bucket
Bucket Flush
EOS
Brigade
BucketBucketBucketBucket
Types of buckets
Heap
Transient
Immortal
Pipe
Socket
File
Pool
MMAP
EOS
Flush
Error
Assumptions
All data can be broken into chunks Each chunk of data must come from the
same source
All HTTP data can be represented as strings of characters, even if not human readable
Filters must allow for optimal performance, even if they don't enforce it If files are in the output stream, then we
should use sendfile
Bucket Functions
apr_bucket_*_create Different arguments for each bucket type
apr_bucket_split
apr_bucket_destroy
apr_bucket_copy
apr_bucket_setaside
Bucket Creation
Bucket
File_bucket socket_bucket
Bucket
Flush
EOS
Bucket
Bucket
Bucket Split
Bucket
File
Bucket
bucket
Bucket
File_bucket
Bucket copy
socket_bucket
Bucket
socket_bucket
Bucket Bucket
Brigade Functions
apr_brigade_create
apr_brigade_split Splits based on buckets
apr_brigade_partition Splits based on offset
apr_brigade_destroy
apr_brigade_write, putstrs, vputstrs, putc, etc Write into a brigade with buffering
apr_brigade_write
Bucket brigade
file_bucket
apr_brigade_write("foo")
Bucket brigade
file_bucket "foo"
apr_brigade_write("bar")
Bucket brigade
file_bucket "foobar"
Input Filter flow
Input processor
Filter 2
Filter 1
HTTP_IN
Core input filter
Empty brigadeFull brigade
apcon_filter_in
Bucket- brigade
GET /foo bar.html HTTP/1.0ap_get_brigade(f- >next, b, mode);e = APR_BRIGADE_FIRST(b);
if (e- >type == NULL) { return NULL;}apr_bucket_read(e, &str, &length, 1);
if ((strncmp("GET ", str, strlen("GET "))) { return APR_SUCCESS;}
apcon_filter_in
Bucket- brigade
GET /foo bar.html HTTP/1.0
apr_bucket_split(e, strlen("GET ") + 1); e = APR_BUCKET_NEXT(e); apr_bucket_read(e, &str, &length, 1); /* this should work, because we are just searching for HTTP/1.0 or HTTP/1.1 */
begin = str + (strlen(str) - 3); do { begin- - ; } while (strncmp("HTTP", begin, 4) && (begin > str));
apcon_filter_in
Bucket- brigade
GET /foo bar.html HTTP/1.0
apr_bucket_split(e, begin - str - 1);
apr_bucket_read(e, &str, &length,1);
replace(" ", "%20");replace("\", "/");
generator/filter flow
Generate content
Filter 1
Filter 2
core_output_filter
Sub_request
Sr filter1
Sr filter 2
HTTP header filter
Header/Footer Filter
Bucket- brigade
File:/home/rbb/test.html
if (ctx- >state == 0) { ctx- >state = 1; if (conf- >headerf) { rr = ap_sub_request_uri(conf- >headerf, f- >r, f- >next); if (rr- >status == HTTP_OK) ap_run_sub_req(rr); } if (conf- >headert) { e = apr_bucket_immortal_create(conf- >headert, strlen(conf- >headert); APR_BRIGADE_INSERT_HEAD(e, bb); }}
Header/Footer Filter
Bucket- brigade
File:/home/rbb/test.html"This is a test"
ap_pass_brigade(f- >next, bb);return APR_SUCCESS;
More Information
Slides on-line Http://www.ntrnet.net/~rbb/presentations
Articles http://www.apachetoday.com http://www.covalent.net/
General Information http://www.apache.org [email protected]
