[multiple] employ ck_calloc, ck_malloc shared code

employ ck_calloc(), ck_malloc() shared code to slightly reduce code size
(centralize the ck_assert() to check that memory allocation succeeded)

[multiple] mark mod_*_plugin_init() funcs cold

[core] allocate one fewer cond_match_t, if needed

allocate one fewer cond_match_t in r->cond_match_data, if any are needed

[core] use stack w/ pcre_exec unless save captures

use stack w/ pcre_exec unless saving captures from config conditions

reduce memory allocations per request where lighttpd.conf does not
contain ur

[core] use stack w/ pcre_exec unless save captures

use stack w/ pcre_exec unless saving captures from config conditions

reduce memory allocations per request where lighttpd.conf does not
contain url.redirect or url.rewrite rules where replacements reference
a match of the enclosing lighttpd.conf condition (e.g. %0, %1, %2 ...)

move cond_cache_t 'patterncount' to cond_match_t 'captures'
While cond_match_t is no longer sized power-2, it is generally expected
to be used much less frequently than before (which was all the time),
since it is now used only with url.redirect or url.rewrite with
references %0, %1, %2, ...

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[core] save config regex captures only if used

save config regex captures separately only if used by url.redirect
or url.rewrite replacement directives within the condition
(or for conditions contai

[core] save config regex captures only if used

save config regex captures separately only if used by url.redirect
or url.rewrite replacement directives within the condition
(or for conditions containing directives from any other module
which calls config_capture() for its directives during init)

keep pointer to match data (cond_match_t *) in r->cond_match[]
rather than cond_match_t to reduce data copying in h2_init_stream().
h2_init_stream() copies the results for already-evaluated conditions
to avoid re-evaluating connection-level conditions for each and every
stream. When conditions are reset, then the pointer in r->cond_match[]
is updated when the condition is re-evaluated. (This all assumes that
HTTP/2 connection-level conditions are not unset or re-evaluated once
HTTP/2 streams begin.)

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[multiple] check feature flags funcs; code reuse

config_feature_bool()
config_feature_int()

[multiple] reduce redundant NULL buffer checks

This commit is a large set of code changes and results in removal of
hundreds, perhaps thousands, of CPU instructions, a portion of which
are on hot co

[multiple] reduce redundant NULL buffer checks

This commit is a large set of code changes and results in removal of
hundreds, perhaps thousands, of CPU instructions, a portion of which
are on hot code paths.

Most (buffer *) used by lighttpd are not NULL, especially since buffers
were inlined into numerous larger structs such as request_st and chunk.

In the small number of instances where that is not the case, a NULL
check is often performed earlier in a function where that buffer is
later used with a buffer_* func. In the handful of cases that remained,
a NULL check was added, e.g. with r->http_host and r->conf.server_tag.

- check for empty strings at config time and set value to NULL if blank
string will be ignored at runtime; at runtime, simple pointer check
for NULL can be used to check for a value that has been set and is not
blank ("")
- use buffer_is_blank() instead of buffer_string_is_empty(),
and use buffer_is_unset() instead of buffer_is_empty(),
where buffer is known not to be NULL so that NULL check can be skipped
- use buffer_clen() instead of buffer_string_length() when buffer is
known not to be NULL (to avoid NULL check at runtime)
- use buffer_truncate() instead of buffer_string_set_length() to
truncate string, and use buffer_extend() to extend

Examples where buffer known not to be NULL:
- cpv->v.b from config_plugin_values_init is not NULL if T_CONFIG_BOOL
(though we might set it to NULL if buffer_is_blank(cpv->v.b))
- address of buffer is arg (&foo)
(compiler optimizer detects this in most, but not all, cases)
- buffer is checked for NULL earlier in func
- buffer is accessed in same scope without a NULL check (e.g. b->ptr)

internal behavior change:
callers must not pass a NULL buffer to some funcs.
- buffer_init_buffer() requires non-null args
- buffer_copy_buffer() requires non-null args
- buffer_append_string_buffer() requires non-null args
- buffer_string_space() requires non-null arg

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[multiple] PCRE w/ PCRE_STUDY_JIT_COMPILE (fixes #2361)

enabled by default
disable using server.feature-flags += ("server.pcre_jit" => "disable")

Available since pcre-8.20 (2011), and improved in p

[multiple] PCRE w/ PCRE_STUDY_JIT_COMPILE (fixes #2361)

enabled by default
disable using server.feature-flags += ("server.pcre_jit" => "disable")

Available since pcre-8.20 (2011), and improved in pcre-8.32 (2012),
PCRE_STUDY_JIT_COMPILE can greatly speed up repeated execution of PCRE
patterns. (https://zherczeg.github.io/sljit/pcre.html)

lighttpd continues to use pcre_exec() instead of pcre_jit_exec(),
even though doing so does not realize all of the performance increase
potentially available with PCRE_STUDY_JIT_COMPILE and pcre_jit_exec().

pcre_jit_exec() is available with PCRE 8.32 and later, if PCRE is
compiled with --enable-jit, but lighttpd does not currently use
pcre_jit_exec() since the PCRE library might not have been compiled
with --enable-jit (though this could be solved with a weak symbol).
Similarly, lighttpd does not currently configure the pcre_jit_stack.

(Using pcre_jit_exec() may be revisited in the future.)

x-ref:
"add support for pcre JIT"
https://redmine.lighttpd.net/issues/2361

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[core] tighten struct data_config and related code

tighten struct data_config and config_cond_info
create config key at startup and reuse for debug/trace
separate routine for configparser_parse_cond

[core] tighten struct data_config and related code

tighten struct data_config and config_cond_info
create config key at startup and reuse for debug/trace
separate routine for configparser_parse_condition()
separate routine for configparser_parse_else_condition()

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[multiple] stat_cache_path_stat() for struct st

stat_cache_path_stat() for cached (struct st *)

[multiple] rename connection_reset hook to request

rename connection_reset to handle_request_reset

[core] remove r->uri.path_raw; generate as needed

(r->uri.path_raw previously duplicated from r->target, minus query-part)

[multiple] split con, request (very large change)

NB: r->tmp_buf == srv->tmp_buf (pointer is copied for quicker access)

NB: request read and write chunkqueues currently point to connection
chun

[multiple] split con, request (very large change)

NB: r->tmp_buf == srv->tmp_buf (pointer is copied for quicker access)

NB: request read and write chunkqueues currently point to connection
chunkqueues; per-request and per-connection chunkqueues are
not distinct from one another
con->read_queue == r->read_queue
con->write_queue == r->write_queue

NB: in the future, a separate connection config may be needed for
connection-level module hooks. Similarly, might need to have
per-request chunkqueues separate from per-connection chunkqueues.
Should probably also have a request_reset() which is distinct from
connection_reset().

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[multiple] copy small struct instead of memcpy()

when patching config

[core] store subrequest_handler instead of mode

store pointer to module in handler_module instead of con->mode id

[core] move plugin_ctx into (request_st *)

NB: in the future, a separate plugin_ctx may be needed for
connection-level plugins to keep state across multiple requests

[core] move addtl request-specific struct members

[multiple] store srv->tmp_buf in tb var

rather than using srv->tmp_buf directly in code modifying temp buf (tb)

[multiple] generic config array type checking

[multiple] stat_cache singleton

[multiple] connection hooks no longer get (srv *)

(explicit (server *) not passed; available in con->srv)

[multiple] prefer (connection *) to (srv *)

convert all log_error_write() to log_error() and pass (log_error_st *)

use con->errh in preference to srv->errh (even though currently same)

avoid passi

[multiple] prefer (connection *) to (srv *)

convert all log_error_write() to log_error() and pass (log_error_st *)

use con->errh in preference to srv->errh (even though currently same)

avoid passing (server *) when previously used only for logging (errh)

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[core] split cond cache from cond matches

[multiple] plugin.c handles common FREE_FUNC code

(simpler for modules; less boilerplate to cut-n-paste)

[core] config_get_config_cond_info()

isolate direct use of (data_config *)