[tor-commits] [tor/master] Replace use of strcmp_len() with new mem_eq_token().

[nickm at torproject.org]

commit a0fad3981e9d072188c6ba19f25bdd78962330d8
Author: Nick Mathewson <nickm at torproject.org>
Date:   Mon Dec 17 09:03:04 2018 -0500

    Replace use of strcmp_len() with new mem_eq_token().
    
    The strcmp_len() function was somewhat misconceived, since we're
    only using it to test whether a length+extent string is equal to a
    NUL-terminated string or not.  By simplifying it and making it
    inlined, we should be able to make it a little faster.
    
    (It *does* show up in profiles.)
    
    Closes ticket 28856.
---
 src/feature/dirparse/parsecommon.c | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/src/feature/dirparse/parsecommon.c b/src/feature/dirparse/parsecommon.c
index e00af0eea..a69957e74 100644
--- a/src/feature/dirparse/parsecommon.c
+++ b/src/feature/dirparse/parsecommon.c
@@ -15,6 +15,7 @@
 #include "lib/string/printf.h"
 #include "lib/memarea/memarea.h"
 #include "lib/crypt_ops/crypto_rsa.h"
+#include "lib/ctime/di_ops.h"
 
 #include <string.h>
 
@@ -251,6 +252,16 @@ token_check_object(memarea_t *area, const char *kwd,
   return tok;
 }
 
+/** Return true iff the <b>memlen</b>-byte chunk of memory at
+ * <b>memlen</b> is the same length as <b>token</b>, and their
+ * contents are equal. */
+static bool
+mem_eq_token(const void *mem, size_t memlen, const char *token)
+{
+  size_t len = strlen(token);
+  return memlen == len && fast_memeq(mem, token, len);
+}
+
 /** Helper function: read the next token from *s, advance *s to the end of the
  * token, and return the parsed token.  Parse *<b>s</b> according to the list
  * of tokens in <b>table</b>.
@@ -290,7 +301,7 @@ get_next_token(memarea_t *area,
 
   next = find_whitespace_eos(*s, eol);
 
-  if (!strcmp_len(*s, "opt", next-*s)) {
+  if (mem_eq_token(*s, next-*s, "opt")) {
     /* Skip past an "opt" at the start of the line. */
     *s = eat_whitespace_eos_no_nl(next, eol);
     next = find_whitespace_eos(*s, eol);
@@ -301,7 +312,7 @@ get_next_token(memarea_t *area,
   /* Search the table for the appropriate entry.  (I tried a binary search
    * instead, but it wasn't any faster.) */
   for (i = 0; table[i].t ; ++i) {
-    if (!strcmp_len(*s, table[i].t, next-*s)) {
+    if (mem_eq_token(*s, next-*s, table[i].t)) {
       /* We've found the keyword. */
       kwd = table[i].t;
       tok->tp = table[i].v;
@@ -354,7 +365,7 @@ get_next_token(memarea_t *area,
 
   obstart = *s; /* Set obstart to start of object spec */
   if (eol - *s <= 16 || memchr(*s+11,'\0',eol-*s-16) || /* no short lines, */
-      strcmp_len(eol-5, "-----", 5) ||           /* nuls or invalid endings */
+      !mem_eq_token(eol-5, 5, "-----") ||   /* nuls or invalid endings */
       (eol-*s) > MAX_UNPARSED_OBJECT_SIZE) {     /* name too long */
     RET_ERR("Malformed object: bad begin line");
   }
@@ -373,8 +384,8 @@ get_next_token(memarea_t *area,
     eol = eos;
   /* Validate the ending tag, which should be 9 + NAME + 5 + eol */
   if ((size_t)(eol-next) != 9+obname_len+5 ||
-      strcmp_len(next+9, tok->object_type, obname_len) ||
-      strcmp_len(eol-5, "-----", 5)) {
+      !mem_eq_token(next+9, obname_len, tok->object_type) ||
+      !mem_eq_token(eol-5, 5, "-----")) {
     tor_snprintf(ebuf, sizeof(ebuf), "Malformed object: mismatched end tag %s",
              tok->object_type);
     ebuf[sizeof(ebuf)-1] = '\0';