[PATCH v2] vt: Use bsearch library function in is_double_width

From: Thomas Meyer
Date: Thu Aug 31 2017 - 10:21:21 EST


Use bsearch library function instead of duplicated functionality.

v2: Re-introduce early exit from old binary search.

Signed-off-by: Thomas Meyer <thomas@xxxxxxxx>
---
drivers/tty/vt/vt.c | 29 ++++++++++++++---------------
1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 2ebaba16f785..ca55004a639e 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -102,6 +102,7 @@
#include <linux/uaccess.h>
#include <linux/kdb.h>
#include <linux/ctype.h>
+#include <linux/bsearch.h>

#define MAX_NR_CON_DRIVER 16

@@ -2142,22 +2143,15 @@ struct interval {
uint32_t last;
};

-static int bisearch(uint32_t ucs, const struct interval *table, int max)
+static int ucs_cmp(const void *key, const void *elt)
{
- int min = 0;
- int mid;
+ uint32_t ucs = *(uint32_t *)key;
+ struct interval e = *(struct interval *) elt;

- if (ucs < table[0].first || ucs > table[max].last)
- return 0;
- while (max >= min) {
- mid = (min + max) / 2;
- if (ucs > table[mid].last)
- min = mid + 1;
- else if (ucs < table[mid].first)
- max = mid - 1;
- else
- return 1;
- }
+ if (ucs > e.last)
+ return 1;
+ else if (ucs < e.first)
+ return -1;
return 0;
}

@@ -2169,7 +2163,12 @@ static int is_double_width(uint32_t ucs)
{ 0xFE10, 0xFE19 }, { 0xFE30, 0xFE6F }, { 0xFF00, 0xFF60 },
{ 0xFFE0, 0xFFE6 }, { 0x20000, 0x2FFFD }, { 0x30000, 0x3FFFD }
};
- return bisearch(ucs, double_width, ARRAY_SIZE(double_width) - 1);
+ 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;
}

static void con_flush(struct vc_data *vc, unsigned long draw_from,
--
2.11.0