[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

1 files changed, 6 insertions, 6 deletions

diff --git a/src/mod_rrdtool.c b/src/mod_rrdtool.c
index 45017697..ea65b933 100644
--- a/src/mod_rrdtool.c
+++ b/src/mod_rrdtool.c
@@ -186,7 +186,7 @@ SETDEFAULTS_FUNC(mod_rrd_set_defaults) {
         for (; -1 != cpv->k_id; ++cpv) {
             switch (cpv->k_id) {
               case 0: /* rrdtool.db-name */
-                if (!buffer_string_is_empty(cpv->v.b)) {
+                if (!buffer_is_blank(cpv->v.b)) {
                     rrd_config *rrd = calloc(1, sizeof(rrd_config));
                     force_assert(rrd);
                     rrd->path_rrd = cpv->v.b;
@@ -196,7 +196,7 @@ SETDEFAULTS_FUNC(mod_rrd_set_defaults) {
                 }
                 break;
               case 1: /* rrdtool.binary */ /* T_CONFIG_SCOPE_SERVER */
-                if (!buffer_string_is_empty(cpv->v.b))
+                if (!buffer_is_blank(cpv->v.b))
                     p->path_rrdtool_bin = cpv->v.b; /*(store directly in p)*/
                 break;
               default:/* should not happen */
@@ -279,7 +279,7 @@ static int mod_rrdtool_create_rrd(server *srv, plugin_data *p, rrd_config *s, ch
 	buffer_clear(cmd);
 	buffer_append_str3(cmd,
 	  CONST_STR_LEN("create "),
-	  CONST_BUF_LEN(s->path_rrd),
+	  BUF_PTR_LEN(s->path_rrd),
 	  CONST_STR_LEN(
 		" --step 60 "
 		"DS:InOctets:ABSOLUTE:600:U:U "
@@ -298,7 +298,7 @@ static int mod_rrdtool_create_rrd(server *srv, plugin_data *p, rrd_config *s, ch
 		"RRA:MIN:0.5:24:775 "
 		"RRA:MIN:0.5:288:797\n"));
 
-	if (-1 == (safe_write(p->write_fd, CONST_BUF_LEN(cmd)))) {
+	if (-1 == (safe_write(p->write_fd, BUF_PTR_LEN(cmd)))) {
 		log_perror(srv->errh, __FILE__, __LINE__, "rrdtool-write: failed");
 		return HANDLER_ERROR;
 	}
@@ -334,7 +334,7 @@ static int mod_rrd_write_data(server *srv, plugin_data *p, rrd_config *s) {
     buffer * const cmd = srv->tmp_buf;
     buffer_clear(cmd);
     buffer_append_str3(cmd, CONST_STR_LEN("update "),
-                            CONST_BUF_LEN(s->path_rrd),
+                            BUF_PTR_LEN(s->path_rrd),
                             CONST_STR_LEN(" N:"));
     buffer_append_int(cmd, s->bytes_read);
     buffer_append_string_len(cmd, CONST_STR_LEN(":"));
@@ -343,7 +343,7 @@ static int mod_rrd_write_data(server *srv, plugin_data *p, rrd_config *s) {
     buffer_append_int(cmd, s->requests);
     buffer_append_string_len(cmd, CONST_STR_LEN("\n"));
 
-    if (-1 == safe_write(p->write_fd, CONST_BUF_LEN(cmd))) {
+    if (-1 == safe_write(p->write_fd, BUF_PTR_LEN(cmd))) {
         log_error(srv->errh, __FILE__, __LINE__, "rrdtool-write: failed");
         return mod_rrd_fatal_error(p);
     }