Remove use of C character class functions that may use locale

Some of these cause warnings, and should never have been used in the first
place since they depend on locale.

NEWS

@@ -2,10 +2,11 @@ serd (0.30.7) unstable;
 
   * Fix potential memory error when serialising URIs
   * Move headers to an include directory
+  * Remove use of C character class functions that may use locale
   * Split up and reorganize unit tests
   * Use aligned allocation via C11 or Windows API where possible
 
- -- David Robillard <d@drobilla.net>  Thu, 12 Nov 2020 19:18:33 +0000
+ -- David Robillard <d@drobilla.net>  Fri, 13 Nov 2020 11:53:07 +0000
 
 serd (0.30.6) stable;
 

src/n3.c

@@ -24,7 +24,6 @@
 #include "serd/serd.h"
 
 #include <assert.h>
-#include <ctype.h>
 #include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
@@ -714,7 +713,7 @@ read_IRIREF(SerdReader* reader, Ref* dest)
 			break;
 		default:
 			if (c <= 0x20) {
-				if (isprint(c)) {
+				if (is_print(c)) {
 					r_err(reader, SERD_ERR_BAD_SYNTAX,
 					      "invalid IRI character `%c' (escape %%%02X)\n",
 					      c, (unsigned)c);

src/serd_internal.h

@@ -20,7 +20,6 @@
 #include "serd/serd.h"
 
 #include <assert.h>
-#include <ctype.h>
 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>

src/string_utils.h

@@ -20,7 +20,6 @@
 #include "serd/serd.h"
 
 #include <assert.h>
-#include <ctype.h>
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
@@ -74,6 +73,12 @@ is_space(const char c)
 	}
 }
 
+static inline bool
+is_print(const int c)
+{
+	return c >= 0x20 && c <= 0x7E;
+}
+
 static inline bool
 is_base64(const uint8_t c)
 {
@@ -93,11 +98,17 @@ serd_substrlen(const uint8_t* str,
                size_t*        n_bytes,
                SerdNodeFlags* flags);
 
+static inline char
+serd_to_upper(const char c)
+{
+	return (char)((c >= 'a' && c <= 'z') ? c - 32 : c);
+}
+
 static inline int
 serd_strncasecmp(const char* s1, const char* s2, size_t n)
 {
 	for (; n > 0 && *s2; s1++, s2++, --n) {
-		if (toupper(*s1) != toupper(*s2)) {
+		if (serd_to_upper(*s1) != serd_to_upper(*s2)) {
 			return ((*(const uint8_t*)s1 < *(const uint8_t*)s2) ? -1 : +1);
 		}
 	}