Fix json_quote_str to handle non-ASCII characters

The current code in json_quote_str() only accepts strict printable ASCII
code points (i.e. 32-127), all other code points are dropped from the
JSON output. The code is attempting to drop only non-printable ASCII
characters, but doing a signed comparison of the byte value is also
dropping characters with values >= 128.

This patch uses an unsigned comparison to accept code points 32-255.

Reviewed-by: Carl Worth <cworth@cworth.org> (with some additional
details for commit message).

1 files changed, 2 insertions, 2 deletions

diff --git a/json.c b/json.c
index f90b0fa2..1d0c1694 100644
--- a/json.c
+++ b/json.c
@@ -63,7 +63,7 @@ json_quote_chararray(const void *ctx, const char *str, const size_t len)
     for (loop = 0, required = 0, ptr = str;
 	 loop < len;
 	 loop++, required++, ptr++) {
-	if (*ptr < 32 || *ptr == '\"' || *ptr == '\\')
+	if ((unsigned char)(*ptr) < 32 || *ptr == '\"' || *ptr == '\\')
 	    required++;
     }
 
@@ -80,7 +80,7 @@ json_quote_chararray(const void *ctx, const char *str, const size_t len)
 
     *ptr2++ = '\"';
     for (loop = 0; loop < len; loop++) {
-	    if (*ptr > 31 && *ptr != '\"' && *ptr != '\\') {
+	if ((unsigned char)(*ptr) > 31 && *ptr != '\"' && *ptr != '\\') {
 		*ptr2++ = *ptr++;
 	    } else {
 		*ptr2++ = '\\';