Bug 707984: Extend fmtquote to cope with high range unicode.

Use surrogate pairs in output as required.

Also (thanks to Tor!) fix fmtquote_xml output.

Thanks to Xybei for the report, and the first version of the patch.

source/fitz/printf.c

@@ -253,7 +253,7 @@ static void fmtquote(struct fmtbuf *out, const char *s, int sq, int eq, int verb
 					for (i = 0; i < n; ++i)
 						fmtputc(out, s[i]);
 				}
-				else
+				else if (c <= 0xffff)
 				{
 					fmtputc(out, '\\');
 					fmtputc(out, 'u');
@@ -262,6 +262,24 @@ static void fmtquote(struct fmtbuf *out, const char *s, int sq, int eq, int verb
 					fmtputc(out, "0123456789ABCDEF"[(c>>4)&15]);
 					fmtputc(out, "0123456789ABCDEF"[(c)&15]);
 				}
+				else
+				{
+					/* Use a surrogate pair */
+					int hi = 0xd800 + ((c - 0x10000) >> 10);
+					int lo = 0xdc00 + ((c - 0x10000) & 0x3ff);
+					fmtputc(out, '\\');
+					fmtputc(out, 'u');
+					fmtputc(out, "0123456789ABCDEF"[(hi>>12)&15]);
+					fmtputc(out, "0123456789ABCDEF"[(hi>>8)&15]);
+					fmtputc(out, "0123456789ABCDEF"[(hi>>4)&15]);
+					fmtputc(out, "0123456789ABCDEF"[(hi)&15]);
+					fmtputc(out, '\\');
+					fmtputc(out, 'u');
+					fmtputc(out, "0123456789ABCDEF"[(lo>>12)&15]);
+					fmtputc(out, "0123456789ABCDEF"[(lo>>8)&15]);
+					fmtputc(out, "0123456789ABCDEF"[(lo>>4)&15]);
+					fmtputc(out, "0123456789ABCDEF"[(lo)&15]);
+				}
 			} else {
 				if (c == sq || c == eq)
 					fmtputc(out, '\\');
@@ -356,6 +374,12 @@ static void fmtquote_xml(struct fmtbuf *out, const char *s)
 			if (c < 32 || c >= 127) {
 				fmtputc(out, '&');
 				fmtputc(out, '#');
+				fmtputc(out, 'x');
+				if (c > 65535)
+				{
+					fmtputc(out, "0123456789ABCDEF"[(c>>20)&15]);
+					fmtputc(out, "0123456789ABCDEF"[(c>>16)&15]);
+				}
 				if (c > 255)
 				{
 					fmtputc(out, "0123456789ABCDEF"[(c>>12)&15]);