Author: stefan2
Date: Mon Aug 18 15:50:44 2014
New Revision: 1618641
URL: http://svn.apache.org/r1618641
Log:
Within FSFS, replace the use of svn__strtol with a variant that
provides overflow detection. FSFS needs a locale-independent
and preferrably quick number parser.
This is to eventually get rid of svn__strtol.
* subversion/libsvn_fs_fs/id.c
(fast__strtol): New local function, mainly taken form string.c
but with overflow checks and state return added.
(part_parse,
txn_id_parse,
svn_fs_fs__id_parse): Update callers.
Modified:
subversion/trunk/subversion/libsvn_fs_fs/id.c
Modified: subversion/trunk/subversion/libsvn_fs_fs/id.c
URL:
http://svn.apache.org/viewvc/subversion/trunk/subversion/libsvn_fs_fs/id.c?rev=1618641&r1=1618640&r2=1618641&view=diff
==============================================================================
--- subversion/trunk/subversion/libsvn_fs_fs/id.c (original)
+++ subversion/trunk/subversion/libsvn_fs_fs/id.c Mon Aug 18 15:50:44 2014
@@ -48,12 +48,55 @@ typedef struct fs_fs__id_t
+/** Like strtol but with a fixed base of 10, locale independent and limited
+ * to non-negative values. Overflows are indicated by a FALSE return value
+ * in which case *RESULT_P will not be modified.
+ *
+ * This allows the compiler to generate massively faster code.
+ * (E.g. Avoiding locale specific processing). ID parsing is one of the
+ * most CPU consuming parts of FSFS data access. Better be quick.
+ */
+static svn_boolean_t
+fast__strtol(long *result_p,
+ const char* buffer,
+ const char** end)
+{
+ /* We allow positive values only. Unsigned arithmetics tend to be faster
+ * as they allow for a wider range of compiler-side optimizations. */
+ unsigned long result = 0;
+ while (1)
+ {
+ unsigned long c = (unsigned char)*buffer - (unsigned char)'0';
+ unsigned long next;
+
+ /* This implies the NUL check. */
+ if (c > 9)
+ break;
+
+ next = result * 10 + c;
+
+ /* Overflow check. */
+ if (next < result)
+ return FALSE;
+
+ result = next;
+ ++buffer;
+ }
+
+ *end = buffer;
+ *result_p = (long)result;
+
+ return TRUE;
+}
+
/* Parse the NUL-terminated ID part at DATA and write the result into *PART.
* Return TRUE if no errors were detected. */
static svn_boolean_t
part_parse(svn_fs_fs__id_part_t *part,
const char *data)
{
+ const char *end;
+
/* special case: ID inside some transaction */
if (data[0] == '_')
{
@@ -78,12 +121,7 @@ part_parse(svn_fs_fs__id_part_t *part,
return *data == '\0';
}
- {
- const char *end;
- part->revision = svn__strtol(data+1, &end);
- }
-
- return TRUE;
+ return fast__strtol(&part->revision, data+1, &end);
}
/* Parse the transaction id in DATA and store the result in *TXN_ID.
@@ -94,7 +132,9 @@ txn_id_parse(svn_fs_fs__id_part_t *txn_i
const char *data)
{
const char *end;
- txn_id->revision = svn__strtol(data, &end);
+ if (!fast__strtol(&txn_id->revision, data, &end))
+ return FALSE;
+
data = strchr(end, '-');
if (data == NULL)
return FALSE;
@@ -489,7 +529,8 @@ svn_fs_fs__id_parse(char *data,
str = svn_cstring_tokenize("/", &data);
if (str == NULL)
return NULL;
- id->private_id.rev_item.revision = svn__strtol(str, &tmp);
+ if (!fast__strtol(&id->private_id.rev_item.revision, str, &tmp))
+ return NULL;
err = svn_cstring_atoi64(&val, data);
if (err)
