@@ -36,7 +36,8 @@ $(obj)/defkeymap.c: $(obj)/%.c: $(src)/%.map
endif
-$(obj)/ucs.o: $(src)/ucs.c $(obj)/ucs_width_table.h $(obj)/ucs_recompose_table.h
+$(obj)/ucs.o: $(src)/ucs.c $(obj)/ucs_width_table.h \
+ $(obj)/ucs_recompose_table.h $(obj)/ucs_fallback_table.h
# You may uncomment one of those to have the UCS tables be regenerated
# during the build process. By default the _shipped versions are used.
@@ -157,3 +157,87 @@ u32 ucs_recompose(u32 base, u32 mark)
return result ? result->recomposed : 0;
}
+
+/*
+ * The fallback table structures implement a 2-level lookup.
+ */
+
+struct ucs_page_desc {
+ u8 page; /* Page index (high byte of code points) */
+ u8 count; /* Number of entries in this page */
+ u16 start; /* Start index in entries array */
+};
+
+struct ucs_page_entry {
+ u8 offset; /* Offset within page (0-255) */
+ u8 fallback; /* Fallback character or range start marker */
+};
+
+#include "ucs_fallback_table.h"
+
+static int ucs_page_desc_cmp(const void *key, const void *element)
+{
+ u8 page = *(u8 *)key;
+ const struct ucs_page_desc *entry = element;
+
+ if (page < entry->page)
+ return -1;
+ if (page > entry->page)
+ return 1;
+ return 0;
+}
+
+static int ucs_page_entry_cmp(const void *key, const void *element)
+{
+ u8 offset = *(u8 *)key;
+ const struct ucs_page_entry *entry = element;
+
+ if (offset < entry->offset)
+ return -1;
+ if (entry->fallback == UCS_PAGE_ENTRY_RANGE_MARKER) {
+ if (offset > entry[1].offset)
+ return 1;
+ } else {
+ if (offset > entry->offset)
+ return 1;
+ }
+ return 0;
+}
+
+/**
+ * ucs_get_fallback() - Get a substitution for the provided Unicode character
+ * @base: Base Unicode code point (UCS-4)
+ *
+ * Get a simpler fallback character for the provided Unicode character.
+ * This is used for terminal display when corresponding glyph is unavailable.
+ * The substitution may not be as good as the actual glyph for the original
+ * character but still way more helpful than a squared question mark.
+ *
+ * Return: Fallback Unicode code point, or 0 if none is available
+ */
+u32 ucs_get_fallback(u32 cp)
+{
+ const struct ucs_page_desc *page;
+ const struct ucs_page_entry *entry;
+ u8 page_idx = cp >> 8, offset = cp;
+
+ if (!UCS_IS_BMP(cp))
+ return 0;
+
+ page = __inline_bsearch(&page_idx, ucs_fallback_pages,
+ ARRAY_SIZE(ucs_fallback_pages),
+ sizeof(*ucs_fallback_pages),
+ ucs_page_desc_cmp);
+ if (!page)
+ return 0;
+
+ entry = __inline_bsearch(&offset, ucs_fallback_entries + page->start,
+ page->count, sizeof(*ucs_fallback_entries),
+ ucs_page_entry_cmp);
+ if (!entry)
+ return 0;
+
+ if (entry->fallback == UCS_PAGE_ENTRY_RANGE_MARKER)
+ entry++;
+ return entry->fallback;
+}
@@ -31,6 +31,7 @@ void console_map_init(void);
bool ucs_is_double_width(uint32_t cp);
bool ucs_is_zero_width(uint32_t cp);
u32 ucs_recompose(u32 base, u32 mark);
+u32 ucs_get_fallback(u32 cp);
#else
static inline u16 inverse_translate(const struct vc_data *conp, u16 glyph,
bool use_unicode)
@@ -75,6 +76,11 @@ static inline u32 ucs_recompose(u32 base, u32 mark)
{
return 0;
}
+
+static inline u32 ucs_get_fallback(u32 cp)
+{
+ return 0;
+}
#endif /* CONFIG_CONSOLE_TRANSLATIONS */
#endif /* __LINUX_CONSOLEMAP_H__ */