vt: move unicode processing to a separate file

This will make it easier to maintain. Also make it depend on
CONFIG_CONSOLE_TRANSLATIONS.

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20250417184849.475581-3-nico@fluxnic.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 66 insertions, 40 deletions

diff --git a/drivers/tty/vt/Makefile b/drivers/tty/vt/Makefile
index 2c8ce8b592ed..e24c8546ac12 100644
--- a/drivers/tty/vt/Makefile
+++ b/drivers/tty/vt/Makefile
@@ -7,7 +7,8 @@ FONTMAPFILE = cp437.uni
 obj-$(CONFIG_VT)			+= vt_ioctl.o vc_screen.o \
 					   selection.o keyboard.o \
 					   vt.o defkeymap.o
-obj-$(CONFIG_CONSOLE_TRANSLATIONS)	+= consolemap.o consolemap_deftbl.o
+obj-$(CONFIG_CONSOLE_TRANSLATIONS)	+= consolemap.o consolemap_deftbl.o \
+					   ucs.o
 
 # Files generated that shall be removed upon make clean
 clean-files := consolemap_deftbl.c defkeymap.c
diff --git a/drivers/tty/vt/ucs.c b/drivers/tty/vt/ucs.c
new file mode 100644
index 000000000000..dc4a6e794531
--- /dev/null
+++ b/drivers/tty/vt/ucs.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ucs.c - Universal Character Set processing
+ */
+
+#include <linux/array_size.h>
+#include <linux/bsearch.h>
+#include <linux/consolemap.h>
+#include <linux/minmax.h>
+
+/* ucs_is_double_width() is based on the wcwidth() implementation by
+ * Markus Kuhn -- 2007-05-26 (Unicode 5.0)
+ * Latest version: https://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c
+ */
+
+struct ucs_interval {
+	u32 first;
+	u32 last;
+};
+
+static const struct ucs_interval ucs_double_width_ranges[] = {
+	{ 0x1100, 0x115F }, { 0x2329, 0x232A }, { 0x2E80, 0x303E },
+	{ 0x3040, 0xA4CF }, { 0xAC00, 0xD7A3 }, { 0xF900, 0xFAFF },
+	{ 0xFE10, 0xFE19 }, { 0xFE30, 0xFE6F }, { 0xFF00, 0xFF60 },
+	{ 0xFFE0, 0xFFE6 }, { 0x20000, 0x2FFFD }, { 0x30000, 0x3FFFD }
+};
+
+static int interval_cmp(const void *key, const void *element)
+{
+	u32 cp = *(u32 *)key;
+	const struct ucs_interval *entry = element;
+
+	if (cp < entry->first)
+		return -1;
+	if (cp > entry->last)
+		return 1;
+	return 0;
+}
+
+/**
+ * ucs_is_double_width() - Determine if a Unicode code point is double-width.
+ * @cp: Unicode code point (UCS-4)
+ *
+ * Return: true if the character is double-width, false otherwise
+ */
+bool ucs_is_double_width(u32 cp)
+{
+	size_t size = ARRAY_SIZE(ucs_double_width_ranges);
+
+	if (!in_range(cp, ucs_double_width_ranges[0].first,
+			  ucs_double_width_ranges[size - 1].last))
+		return false;
+
+	return __inline_bsearch(&cp, ucs_double_width_ranges, size,
+				sizeof(*ucs_double_width_ranges),
+				interval_cmp) != NULL;
+}
diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index b5f3c8a818ed..bcb508bc15ab 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -104,7 +104,6 @@
 #include <linux/uaccess.h>
 #include <linux/kdb.h>
 #include <linux/ctype.h>
-#include <linux/bsearch.h>
 #include <linux/gcd.h>
 
 #define MAX_NR_CON_DRIVER 16
@@ -2712,43 +2711,6 @@ static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, u8 c)
 	}
 }
 
-/* is_double_width() is based on the wcwidth() implementation by
- * Markus Kuhn -- 2007-05-26 (Unicode 5.0)
- * Latest version: https://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c
- */
-struct interval {
-	uint32_t first;
-	uint32_t last;
-};
-
-static int ucs_cmp(const void *key, const void *elt)
-{
-	uint32_t ucs = *(uint32_t *)key;
-	struct interval e = *(struct interval *) elt;
-
-	if (ucs > e.last)
-		return 1;
-	else if (ucs < e.first)
-		return -1;
-	return 0;
-}
-
-static int is_double_width(uint32_t ucs)
-{
-	static const struct interval double_width[] = {
-		{ 0x1100, 0x115F }, { 0x2329, 0x232A }, { 0x2E80, 0x303E },
-		{ 0x3040, 0xA4CF }, { 0xAC00, 0xD7A3 }, { 0xF900, 0xFAFF },
-		{ 0xFE10, 0xFE19 }, { 0xFE30, 0xFE6F }, { 0xFF00, 0xFF60 },
-		{ 0xFFE0, 0xFFE6 }, { 0x20000, 0x2FFFD }, { 0x30000, 0x3FFFD }
-	};
-	if (ucs < double_width[0].first ||
-	    ucs > double_width[ARRAY_SIZE(double_width) - 1].last)
-		return 0;
-
-	return bsearch(&ucs, double_width, ARRAY_SIZE(double_width),
-			sizeof(struct interval), ucs_cmp) != NULL;
-}
-
 struct vc_draw_region {
 	unsigned long from, to;
 	int x;
@@ -2953,7 +2915,7 @@ static int vc_con_write_normal(struct vc_data *vc, int tc, int c,
 	bool inverse = false;
 
 	if (vc->vc_utf && !vc->vc_disp_ctrl) {
-		if (is_double_width(c))
+		if (ucs_is_double_width(c))
 			width = 2;
 	}
 
diff --git a/include/linux/consolemap.h b/include/linux/consolemap.h
index c35db4896c37..caf079bcb8c9 100644
--- a/include/linux/consolemap.h
+++ b/include/linux/consolemap.h
@@ -28,6 +28,7 @@ int conv_uni_to_pc(struct vc_data *conp, long ucs);
 u32 conv_8bit_to_uni(unsigned char c);
 int conv_uni_to_8bit(u32 uni);
 void console_map_init(void);
+bool ucs_is_double_width(uint32_t cp);
 #else
 static inline u16 inverse_translate(const struct vc_data *conp, u16 glyph,
 		bool use_unicode)
@@ -57,6 +58,11 @@ static inline int conv_uni_to_8bit(u32 uni)
 }
 
 static inline void console_map_init(void) { }
+
+static inline bool ucs_is_double_width(uint32_t cp)
+{
+	return false;
+}
 #endif /* CONFIG_CONSOLE_TRANSLATIONS */
 
 #endif /* __LINUX_CONSOLEMAP_H__ */