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r15436@catbus: nickm | 2007-10-01 21:17:27 -0400

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Fix disgusting O(n^2) behavior in router_parse_list_from_string.  Noticed by Li-Hui Zhou; found with oprofile.


svn:r11738
This commit is contained in:
Nick Mathewson 2007-10-02 01:22:42 +00:00
parent b8364ef8c7
commit 439fe55c6b
2 changed files with 41 additions and 32 deletions
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6
ChangeLog
View File

@ -12,6 +12,12 @@ Changes in version 0.2.0.8-alpha - 2007-??-??
- Use annotations to record the source for each descriptor.
- Use annotations to record the purpose of each descriptor.
o Major bugfixes (performance):
- Fix really bad O(n^2) performance when parsing a long list of routers:
Instead of searching the entire list for an "extra-info " string which
usually wasn't there, once for every routerinfo we read, just scan
lines forward until we find one we like. Bugfix on 0.2.0.1.
o Minor bugfixes (controller):
- When sending a status event to the controller telling it that an
OR address is readable, set the port correctly. (Previously we

67
src/or/routerparse.c
View File

@ -855,6 +855,40 @@ check_signature_token(const char *digest,
return 0;
}
/** DOCDOC */
static int
find_start_of_next_router_or_extrainfo(const char **s_ptr,
const char *eos,
int *is_extrainfo_out)
{
const char *annotations = NULL;
const char *s = *s_ptr;
s = eat_whitespace_eos(s, eos);
while (s < eos-32) { /* 32 gives enough room for a the first keyword. */
/* We're at the start of a line. */
tor_assert(*s != '\n');
if (*s == '@' && !annotations) {
annotations = s;
} else if (*s == 'r' && !strcmpstart(s, "router ")) {
*s_ptr = annotations ? annotations : s;
*is_extrainfo_out = 0;
return 0;
} else if (*s == 'e' && !strcmpstart(s, "extra-info ")) {
*s_ptr = annotations ? annotations : s;
*is_extrainfo_out = 1;
return 0;
}
if (!(s = memchr(s+1, '\n', eos-(s+1))))
break;
s = eat_whitespace_eos(s, eos);
}
return -1;
}
/** Given a string *<b>s</b> containing a concatenated sequence of router
* descriptors (or extra-info documents if <b>is_extrainfo</b> is set), parses
* them and stores the result in <b>dest</b>. All routers are marked running
@ -893,40 +927,9 @@ router_parse_list_from_string(const char **s, const char *eos,
tor_assert(eos >= *s);
while (1) {
*s = eat_whitespace_eos(*s, eos);
if ((eos - *s) < 32) /* make sure it's long enough. */
if (find_start_of_next_router_or_extrainfo(s, eos, &have_extrainfo) < 0)
break;
/* Don't start parsing the rest of *s unless it contains a router or
* extra-info. */
if (strcmpstart(*s, "extra-info ")==0) {
have_extrainfo = 1;
} else if (strcmpstart(*s, "router ")==0) {
have_extrainfo = 0;
} else {
/* skip junk. */
const char *annotation = NULL, *ei, *ri;
if (**s == '@') {
annotation = *s;
} else {
if ((annotation = tor_memstr(*s, eos-*s, "\n@")))
++annotation;
}
ei = tor_memstr(*s, eos-*s, "\nextra-info ");
ri = tor_memstr(*s, eos-*s, "\nrouter ");
if (ri && (!ei || ri < ei)) {
have_extrainfo = 0;
*s = ri + 1;
} else if (ei) {
have_extrainfo = 1;
*s = ei + 1;
} else {
break;
}
if (annotation && annotation < *s)
*s = annotation;
}
end = tor_memstr(*s, eos-*s, "\nrouter-signature");
if (end)
end = tor_memstr(end, eos-end, "\n-----END SIGNATURE-----\n");