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Subject[Trivial Patch] Remove JFFS2 dependency on internal Zlib header
Date
History:
During the discussion over the speed and stability of the proposed inclusion
of a stripped-down, minimized version of the LZO compression algorithm it was
noted that the way that patch handled separation of compression and
decompression could be used for zlib as well. Then it was noted that moving
the private zlib header 'zutil.h' to a combined zlib directory would break
JFFS2, which used it. On examining JFFS2 it became clear that the only thing
JFFS2 used the header for was a single constant. Since his code was involved,
Mark Adler was contacted and he stated that that constant - PRESET_DICT - was
part of the zlib standard and defined in RFC 1950. So, to remove the
dependency the simplest recourse is to replace PRESET_DICT with the 'magic
number' it represents.

Signed-off-by: Daniel Hazelton <dhazelton@enter.net>

DRH

diff --git a/fs/jffs2/compr_zlib.c b/fs/jffs2/compr_zlib.c
index 2b87fcc..9f1b935 100644
--- a/fs/jffs2/compr_zlib.c
+++ b/fs/jffs2/compr_zlib.c
@@ -16,7 +16,6 @@
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/zlib.h>
-#include <linux/zutil.h>
#include "nodelist.h"
#include "compr.h"

@@ -154,7 +153,7 @@ static int jffs2_zlib_decompress(unsigned char *data_in,

/* If it's deflate, and it's got no preset dictionary, then
we can tell zlib to skip the adler32 check. */
- if (srclen > 2 && !(data_in[1] & PRESET_DICT) &&
+ if (srclen > 2 && !(data_in[1] & 0x20) &&
((data_in[0] & 0x0f) == Z_DEFLATED) &&
!(((data_in[0]<<8) + data_in[1]) % 31)) {
diff --git a/fs/jffs2/compr_zlib.c b/fs/jffs2/compr_zlib.c
index 2b87fcc..9f1b935 100644
--- a/fs/jffs2/compr_zlib.c
+++ b/fs/jffs2/compr_zlib.c
@@ -16,7 +16,6 @@
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/zlib.h>
-#include <linux/zutil.h>
#include "nodelist.h"
#include "compr.h"

@@ -154,7 +153,7 @@ static int jffs2_zlib_decompress(unsigned char *data_in,

/* If it's deflate, and it's got no preset dictionary, then
we can tell zlib to skip the adler32 check. */
- if (srclen > 2 && !(data_in[1] & PRESET_DICT) &&
+ if (srclen > 2 && !(data_in[1] & 0x20) &&
((data_in[0] & 0x0f) == Z_DEFLATED) &&
!(((data_in[0]<<8) + data_in[1]) % 31)) {
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