From 55ac90d9647c5e27aec8f93796d79be21167a856 Mon Sep 17 00:00:00 2001
From: Mattias Andrée <maandree@kth.se>
Date: Tue, 17 Jan 2023 19:48:42 +0100
Subject: libfonts_do_decoded_font_descriptions_match: check charset subset
 coverage
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Signed-off-by: Mattias Andrée <maandree@kth.se>
---
 libfonts.h                                    |  2 +-
 libfonts_do_decoded_font_descriptions_match.c | 67 ++++++++++++++++++++++++++-
 2 files changed, 67 insertions(+), 2 deletions(-)

diff --git a/libfonts.h b/libfonts.h
index 11e4ea4..e20152f 100644
--- a/libfonts.h
+++ b/libfonts.h
@@ -1625,7 +1625,7 @@ struct libfonts_font_description {
 	 * inclusive ranges included the subset. A range will either be a
 	 * decimal integer, or an two decimal integers separated by a "-"
 	 * (the left-hand side will be strictly less than the right-hand side).
-	 * All ranges will be disjunction, and have a non-zero distance.
+	 * All ranges will be disjunctive, and have a non-zero distance.
 	 * 
 	 * The library will take care of converting hexadecimal numbers (prefixed
 	 * with "0x") to decimal, removing leading zeroes, converting "_" to "-",
diff --git a/libfonts_do_decoded_font_descriptions_match.c b/libfonts_do_decoded_font_descriptions_match.c
index 776ca4f..a6b0fb9 100644
--- a/libfonts_do_decoded_font_descriptions_match.c
+++ b/libfonts_do_decoded_font_descriptions_match.c
@@ -19,9 +19,74 @@
 	X(average_width, equal) _\
 	X(charset_registry, equal) _\
 	X(charset_encoding, equal) _\
-	X(charset_subset, equal) /* TODO desc shall match spec if spec is a subset of desc */
+	X(charset_subset, super)
 
 
+static const char *
+read_uint32(uint32_t *restrict nump, const char *s)
+{
+	uint32_t r;
+	for (r = 0; isdigit(*s); s++)
+		r = r * 10 + (uint32_t)(*s & 15);
+	*nump = r;
+	return s;
+}
+
+static int
+super(const char *desc, const char *spec)
+{
+	uint32_t dl = 0, dh = 0, sl = 0, sh = 0;
+	int have_d = 0, have_s = 0;
+
+	if (!spec || !desc)
+		return 1;
+
+	while (*desc && *spec) {
+		if (!have_d) {
+			have_d = 1;
+			if (!isdigit(*desc))
+				return 0;
+			desc = read_uint32(&dl, desc);
+			if (desc[0] == '-' && isdigit(desc[1]))
+				desc = read_uint32(&dh, desc);
+			else
+				dh = dl;
+			if (*desc) {
+				if (*desc != ' ')
+					return 0;
+				desc++;
+			}
+		}
+
+		if (!have_s) {
+			have_s = 1;
+			if (!isdigit(*spec))
+				return 0;
+			spec = read_uint32(&sl, spec);
+			if (spec[0] == '-' && isdigit(spec[1]))
+				spec = read_uint32(&sh, spec);
+			else
+				sh = sl;
+			if (*spec) {
+				if (*spec != ' ')
+					return 0;
+				spec++;
+			}
+		}
+
+		if (sl < dl)
+			return 0;
+		else if (sl > dh)
+			have_d = 0;
+		else if (sh > dh)
+			return 0;
+		else
+			have_s = 0;
+	}
+
+	return !*spec;
+}
+
 static int
 equal(const char *desc, const char *spec)
 {
-- 
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