Add a runtime check to see if parse_int64 needs to workaround sscanf bugs. If that workaround is not needed parsing is nearly twice as fast.
diff --git a/json_util.c b/json_util.c
index 4e4e00c..194f290 100644
--- a/json_util.c
+++ b/json_util.c
@@ -61,6 +61,10 @@
#include "json_tokener.h"
#include "json_util.h"
+static int sscanf_is_broken = 0;
+static int sscanf_is_broken_testdone = 0;
+static void sscanf_is_broken_test(void);
+
struct json_object* json_object_from_file(const char *filename)
{
struct printbuf *pb;
@@ -142,41 +146,78 @@
return json_object_to_file_ext(filename, obj, JSON_C_TO_STRING_PLAIN);
}
+/*
+ * Not all implementations of sscanf actually work properly.
+ * Check whether the one we're currently using does, and if
+ * it's broken, enable the workaround code.
+ */
+static void sscanf_is_broken_test()
+{
+ int64_t num64;
+
+ (void)sscanf(" -01234567890123456789012345", "%" SCNd64, &num64);
+ int ret_errno = errno;
+ int is_int64_min = (num64 == INT64_MIN);
+
+ (void)sscanf(" 01234567890123456789012345", "%" SCNd64, &num64);
+ int ret_errno2 = errno;
+ int is_int64_max = (num64 == INT64_MAX);
+
+ if (ret_errno != ERANGE || !is_int64_min ||
+ ret_errno2 != ERANGE || !is_int64_max)
+ {
+ MC_DEBUG("sscanf_is_broken_test failed, enabling workaround code\n");
+ sscanf_is_broken = 1;
+ }
+}
+
int json_parse_int64(const char *buf, int64_t *retval)
{
int64_t num64;
- const char *buf_skip_space;
+ const char *buf_sig_digits;
int orig_has_neg;
int saved_errno;
+
+ if (!sscanf_is_broken_testdone)
+ {
+ sscanf_is_broken_test();
+ sscanf_is_broken_testdone = 1;
+ }
+
+ // Skip leading spaces
+ while (isspace((int)*buf) && *buf)
+ buf++;
+
errno = 0; // sscanf won't always set errno, so initialize
if (sscanf(buf, "%" SCNd64, &num64) != 1)
{
MC_DEBUG("Failed to parse, sscanf != 1\n");
return 1;
}
+
saved_errno = errno;
- buf_skip_space = buf;
+ buf_sig_digits = buf;
orig_has_neg = 0;
- // Skip leading spaces
- while (isspace((int)*buf_skip_space) && *buf_skip_space)
- buf_skip_space++;
- if (*buf_skip_space == '-')
+ if (*buf_sig_digits == '-')
{
- buf_skip_space++;
+ buf_sig_digits++;
orig_has_neg = 1;
}
- // Skip leading zeros, but keep at least one digit
- while (buf_skip_space[0] == '0' && buf_skip_space[1] != '\0')
- buf_skip_space++;
- if (buf_skip_space[0] == '0' && buf_skip_space[1] == '\0')
- orig_has_neg = 0; // "-0" is the same as just plain "0"
-
- if (saved_errno != ERANGE)
+
+ // Not all sscanf implementations actually work
+ if (sscanf_is_broken && saved_errno != ERANGE)
{
char buf_cmp[100];
char *buf_cmp_start = buf_cmp;
int recheck_has_neg = 0;
int buf_cmp_len;
+
+ // Skip leading zeros, but keep at least one digit
+ while (buf_sig_digits[0] == '0' && buf_sig_digits[1] != '\0')
+ buf_sig_digits++;
+ if (num64 == 0) // assume all sscanf impl's will parse -0 to 0
+ orig_has_neg = 0; // "-0" is the same as just plain "0"
+
snprintf(buf_cmp_start, sizeof(buf_cmp), "%" PRId64, num64);
if (*buf_cmp_start == '-')
{
@@ -190,18 +231,22 @@
* If the sign is different, or
* some of the digits are different, or
* there is another digit present in the original string
- * then we NOT successfully parsed the value.
+ * then we have NOT successfully parsed the value.
*/
if (orig_has_neg != recheck_has_neg ||
- strncmp(buf_skip_space, buf_cmp_start, strlen(buf_cmp_start)) != 0 ||
- ((int)strlen(buf_skip_space) != buf_cmp_len &&
- isdigit((int)buf_skip_space[buf_cmp_len])
+ strncmp(buf_sig_digits, buf_cmp_start, strlen(buf_cmp_start)) != 0 ||
+ ((int)strlen(buf_sig_digits) != buf_cmp_len &&
+ isdigit((int)buf_sig_digits[buf_cmp_len])
)
)
{
saved_errno = ERANGE;
}
}
+
+ // Not all sscanf impl's set the value properly when out of range.
+ // Always do this, even for properly functioning implementations,
+ // since it shouldn't slow things down much.
if (saved_errno == ERANGE)
{
if (orig_has_neg)