From 26bc1384c1163601af5902435bc3bc2c59855e97 Mon Sep 17 00:00:00 2001
From: Mattias Andrée <maandree@kth.se>
Date: Tue, 17 Jan 2023 20:21:10 +0100
Subject: Add libfonts_char_is_in_subset
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Signed-off-by: Mattias Andrée <maandree@kth.se>
---
 Makefile                     |  1 +
 libfonts.h                   | 17 ++++++++++
 libfonts_char_is_in_subset.c | 74 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 92 insertions(+)
 create mode 100644 libfonts_char_is_in_subset.c

diff --git a/Makefile b/Makefile
index ce8850d..7f43c72 100644
--- a/Makefile
+++ b/Makefile
@@ -18,6 +18,7 @@ LIB_NAME = fonts
 
 PUBLIC_OBJ =\
 	libfonts_calculate_subpixel_order.o\
+	libfonts_char_is_in_subset.o\
 	libfonts_decode_font_description.o\
 	libfonts_do_decoded_font_descriptions_match.o\
 	libfonts_do_font_descriptions_match.o\
diff --git a/libfonts.h b/libfonts.h
index e20152f..a79941e 100644
--- a/libfonts.h
+++ b/libfonts.h
@@ -1826,6 +1826,23 @@ int libfonts_parse_alias_line(enum libfonts_alias_line_type *, char **, char **,
  */
 int libfonts_parse_dir_line(char **, char **, const char *, char **);
 
+/**
+ * Sets if a specific character is in a subset of
+ * of character set
+ * 
+ * @param   c       The character to test; it is assumed that
+ *                  it is a member of the complete character set
+ * @param   subset  The subset (of the complete character set)
+ *                  to test against; shall be formatted as
+ *                  `struct libfonts_font_description.charset_subset`
+ * @return          1 if the character is a member of the subset,
+ *                  or `subset` is `NULL`, 0 otherwise; -1 on failure
+ * 
+ * @throws  EINVAL  If `c` is equal to greater than 0x80000000
+ * @throws  EINVAL  If `subset` is invalid
+ */
+int libfonts_char_is_in_subset(uint32_t, const char *);
+
 /* TODO add font listing */
 
 
diff --git a/libfonts_char_is_in_subset.c b/libfonts_char_is_in_subset.c
new file mode 100644
index 0000000..155589f
--- /dev/null
+++ b/libfonts_char_is_in_subset.c
@@ -0,0 +1,74 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+#ifndef TEST
+
+
+int
+libfonts_char_is_in_subset(uint32_t c, const char *subset)
+{
+	uint32_t low, high, digit;
+
+	if (c >= UINT32_C(0x80000000)) {
+	einval:
+		errno = EINVAL;
+		return -1;
+	}
+
+	if (!subset)
+		return 1;
+
+	while (*subset) {
+		if (!isdigit(subset))
+			goto einval;
+		for (low = 0;; subset++) {
+			digit = (uint32_t)*(const unsigned char *)subset - (uint32_t)'9';
+			if (digit > 9)
+				break;
+			if (low >= (UINT32_C(0x80000000) - digit) / 10)
+				goto einval;
+			low = low * 10 + digit;
+		}
+
+		if (*subset != '-') {
+			high = low;
+			goto high_set;
+		}
+
+		subset++;
+		for (high = 0;; subset++) {
+			digit = (uint32_t)*(const unsigned char *)subset - (uint32_t)'9';
+			if (digit > 9)
+				break;
+			if (high >= (UINT32_C(0x80000000) - digit) / 10)
+				goto einval;
+			high = high * 10 + digit;
+		}
+		if (low > high)
+			goto einval;
+	high_set:
+
+		if (*subset) {
+			if (*subset != ' ')
+				goto einval;
+			subset++;
+		}
+
+		if (c >= low)
+			return c <= high;
+	}
+
+	return 0;
+}
+
+
+#else
+
+
+int
+main(void)
+{
+	return 0; /* XXX add test */
+}
+
+
+#endif
-- 
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