Eliminate use of ctype.h and replace isdigit() and tolower() with non-locale-sensitive approaches.

json_object.c

@@ -13,7 +13,6 @@
 #include "strerror_override.h"
 
 #include <assert.h>
-#include <ctype.h>
 #ifdef HAVE_LIMITS_H
 #include <limits.h>
 #endif
@@ -35,6 +34,9 @@
 #include "snprintf_compat.h"
 #include "strdup_compat.h"
 
+/* Avoid ctype.h and locale overhead */
+#define is_plain_digit(c) ((c) >= '0' && (c) <= '9')
+
 #if SIZEOF_LONG_LONG != SIZEOF_INT64_T
 #error "The long long type isn't 64-bits"
 #endif
@@ -1056,8 +1058,8 @@ static int json_object_double_to_json_string_format(struct json_object *jso, str
 			format_drops_decimals = 1;
 
 		looks_numeric = /* Looks like *some* kind of number */
-		    isdigit((unsigned char)buf[0]) ||
-		    (size > 1 && buf[0] == '-' && isdigit((unsigned char)buf[1]));
+		    is_plain_digit(buf[0]) ||
+		    (size > 1 && buf[0] == '-' && is_plain_digit(buf[1]));
 
 		if (size < (int)sizeof(buf) - 2 && looks_numeric && !p && /* Has no decimal point */
 		    strchr(buf, 'e') == NULL && /* Not scientific notation */

json_pointer.c

@@ -10,7 +10,6 @@
 
 #include "strerror_override.h"
 
-#include <ctype.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -20,6 +19,9 @@
 #include "strdup_compat.h"
 #include "vasprintf_compat.h"
 
+/* Avoid ctype.h and locale overhead */
+#define is_plain_digit(c) ((c) >= '0' && (c) <= '9')
+
 /**
  * JavaScript Object Notation (JSON) Pointer
  *   RFC 6901 - https://tools.ietf.org/html/rfc6901
@@ -47,7 +49,7 @@ static int is_valid_index(struct json_object *jo, const char *path, int32_t *idx
 	 */
 	if (len == 1)
 	{
-		if (isdigit((unsigned char)path[0]))
+		if (is_plain_digit(path[0]))
 		{
 			*idx = (path[0] - '0');
 			goto check_oob;
@@ -64,7 +66,7 @@ static int is_valid_index(struct json_object *jo, const char *path, int32_t *idx
 	/* RFC states base-10 decimals */
 	for (i = 0; i < len; i++)
 	{
-		if (!isdigit((unsigned char)path[i]))
+		if (!is_plain_digit(path[i]))
 		{
 			errno = EINVAL;
 			return 0;

json_tokener.c

@@ -17,7 +17,6 @@
 
 #include "math_compat.h"
 #include <assert.h>
-#include <ctype.h>
 #include <limits.h>
 #include <math.h>
 #include <stddef.h>
@@ -82,7 +81,8 @@ static inline int is_hex_char(char c)
 static const char json_null_str[] = "null";
 static const int json_null_str_len = sizeof(json_null_str) - 1;
 static const char json_inf_str[] = "Infinity";
-static const char json_inf_str_lower[] = "infinity";
+/* Swapped case "Infinity" to avoid need to call tolower() on input chars: */
+static const char json_inf_str_invert[] = "iNFINITY";
 static const unsigned int json_inf_str_len = sizeof(json_inf_str) - 1;
 static const char json_nan_str[] = "NaN";
 static const int json_nan_str_len = sizeof(json_nan_str) - 1;
@@ -442,17 +442,15 @@ struct json_object *json_tokener_parse_ex(struct json_tokener *tok, const char *
 			 * complicated with likely little performance benefit.
 			 */
 			int is_negative = 0;
-			const char *_json_inf_str = json_inf_str;
-			if (!(tok->flags & JSON_TOKENER_STRICT))
-				_json_inf_str = json_inf_str_lower;
 
 			/* Note: tok->st_pos must be 0 when state is set to json_tokener_state_inf */
 			while (tok->st_pos < (int)json_inf_str_len)
 			{
 				char inf_char = *str;
-				if (!(tok->flags & JSON_TOKENER_STRICT))
-					inf_char = tolower((unsigned char)*str);
-				if (inf_char != _json_inf_str[tok->st_pos])
+				if (inf_char != json_inf_str[tok->st_pos] &&
+				    ((tok->flags & JSON_TOKENER_STRICT) ||
+				      inf_char != json_inf_str_invert[tok->st_pos])
+				   )
 				{
 					tok->err = json_tokener_error_parse_unexpected;
 					goto out;

json_util.c

@@ -14,7 +14,6 @@
 
 #include "strerror_override.h"
 
-#include <ctype.h>
 #include <limits.h>
 #include <stdarg.h>
 #include <stddef.h>