8c6b1ac71e
Also include some minor fixes for gcc 5.1.1 Signed-off-by: Peter Jones <pjones@redhat.com>
49 lines
1.3 KiB
Diff
49 lines
1.3 KiB
Diff
From 7ba066419a2e0f777a0c103b058fba49e1492f04 Mon Sep 17 00:00:00 2001
|
|
From: Vladimir Serbinenko <phcoder@gmail.com>
|
|
Date: Thu, 26 Feb 2015 22:10:09 +0100
|
|
Subject: [PATCH 340/506] gzio: Optimize by removing division.
|
|
|
|
---
|
|
grub-core/io/gzio.c | 18 +++++++++++++++++-
|
|
1 file changed, 17 insertions(+), 1 deletion(-)
|
|
|
|
diff --git a/grub-core/io/gzio.c b/grub-core/io/gzio.c
|
|
index 129209e..0f2ea6b 100644
|
|
--- a/grub-core/io/gzio.c
|
|
+++ b/grub-core/io/gzio.c
|
|
@@ -1161,6 +1161,19 @@ grub_gzio_open (grub_file_t io, const char *name __attribute__ ((unused)))
|
|
return file;
|
|
}
|
|
|
|
+static grub_uint8_t
|
|
+mod_31 (grub_uint16_t v)
|
|
+{
|
|
+ /* At most 2 iterations for any number that
|
|
+ we can get here.
|
|
+ In any case faster than real division. */
|
|
+ while (v > 0x1f)
|
|
+ v = (v & 0x1f) + (v >> 5);
|
|
+ if (v == 0x1f)
|
|
+ return 0;
|
|
+ return v;
|
|
+}
|
|
+
|
|
static int
|
|
test_zlib_header (grub_gzio_t gzio)
|
|
{
|
|
@@ -1178,7 +1191,10 @@ test_zlib_header (grub_gzio_t gzio)
|
|
return 0;
|
|
}
|
|
|
|
- if ((cmf * 256U + flg) % 31U)
|
|
+ /* Usually it would be: (cmf * 256 + flg) % 31 != 0. */
|
|
+ /* But 256 == 8 (31). */
|
|
+ /* By multiplying by 4 and using 32 == 1 (31). We get our formula. */
|
|
+ if (mod_31 (cmf + flg * 4) != 0)
|
|
{
|
|
grub_error (GRUB_ERR_BAD_COMPRESSED_DATA, N_("unsupported gzip format"));
|
|
return 0;
|
|
--
|
|
2.4.3
|
|
|