ia64/linux-2.6.18-xen.hg

view fs/jffs2/compr_rtime.c @ 524:7f8b544237bf

netfront: Allow netfront in domain 0.

This is useful if your physical network device is in a utility domain.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
author Keir Fraser <keir.fraser@citrix.com>
date Tue Apr 15 15:18:58 2008 +0100 (2008-04-15)
parents 831230e53067
children
line source
1 /*
2 * JFFS2 -- Journalling Flash File System, Version 2.
3 *
4 * Copyright (C) 2001-2003 Red Hat, Inc.
5 *
6 * Created by Arjan van de Ven <arjanv@redhat.com>
7 *
8 * For licensing information, see the file 'LICENCE' in this directory.
9 *
10 * $Id: compr_rtime.c,v 1.14 2004/06/23 16:34:40 havasi Exp $
11 *
12 *
13 * Very simple lz77-ish encoder.
14 *
15 * Theory of operation: Both encoder and decoder have a list of "last
16 * occurrences" for every possible source-value; after sending the
17 * first source-byte, the second byte indicated the "run" length of
18 * matches
19 *
20 * The algorithm is intended to only send "whole bytes", no bit-messing.
21 *
22 */
24 #include <linux/kernel.h>
25 #include <linux/types.h>
26 #include <linux/errno.h>
27 #include <linux/string.h>
28 #include <linux/jffs2.h>
29 #include "compr.h"
31 /* _compress returns the compressed size, -1 if bigger */
32 static int jffs2_rtime_compress(unsigned char *data_in,
33 unsigned char *cpage_out,
34 uint32_t *sourcelen, uint32_t *dstlen,
35 void *model)
36 {
37 short positions[256];
38 int outpos = 0;
39 int pos=0;
41 memset(positions,0,sizeof(positions));
43 while (pos < (*sourcelen) && outpos <= (*dstlen)-2) {
44 int backpos, runlen=0;
45 unsigned char value;
47 value = data_in[pos];
49 cpage_out[outpos++] = data_in[pos++];
51 backpos = positions[value];
52 positions[value]=pos;
54 while ((backpos < pos) && (pos < (*sourcelen)) &&
55 (data_in[pos]==data_in[backpos++]) && (runlen<255)) {
56 pos++;
57 runlen++;
58 }
59 cpage_out[outpos++] = runlen;
60 }
62 if (outpos >= pos) {
63 /* We failed */
64 return -1;
65 }
67 /* Tell the caller how much we managed to compress, and how much space it took */
68 *sourcelen = pos;
69 *dstlen = outpos;
70 return 0;
71 }
74 static int jffs2_rtime_decompress(unsigned char *data_in,
75 unsigned char *cpage_out,
76 uint32_t srclen, uint32_t destlen,
77 void *model)
78 {
79 short positions[256];
80 int outpos = 0;
81 int pos=0;
83 memset(positions,0,sizeof(positions));
85 while (outpos<destlen) {
86 unsigned char value;
87 int backoffs;
88 int repeat;
90 value = data_in[pos++];
91 cpage_out[outpos++] = value; /* first the verbatim copied byte */
92 repeat = data_in[pos++];
93 backoffs = positions[value];
95 positions[value]=outpos;
96 if (repeat) {
97 if (backoffs + repeat >= outpos) {
98 while(repeat) {
99 cpage_out[outpos++] = cpage_out[backoffs++];
100 repeat--;
101 }
102 } else {
103 memcpy(&cpage_out[outpos],&cpage_out[backoffs],repeat);
104 outpos+=repeat;
105 }
106 }
107 }
108 return 0;
109 }
111 static struct jffs2_compressor jffs2_rtime_comp = {
112 .priority = JFFS2_RTIME_PRIORITY,
113 .name = "rtime",
114 .compr = JFFS2_COMPR_RTIME,
115 .compress = &jffs2_rtime_compress,
116 .decompress = &jffs2_rtime_decompress,
117 #ifdef JFFS2_RTIME_DISABLED
118 .disabled = 1,
119 #else
120 .disabled = 0,
121 #endif
122 };
124 int jffs2_rtime_init(void)
125 {
126 return jffs2_register_compressor(&jffs2_rtime_comp);
127 }
129 void jffs2_rtime_exit(void)
130 {
131 jffs2_unregister_compressor(&jffs2_rtime_comp);
132 }