1 /* 1 /*
2 * JFFS2 -- Journalling Flash File System, Ver 2 * JFFS2 -- Journalling Flash File System, Version 2.
3 * 3 *
4 * Copyright © 2001-2007 Red Hat, Inc. !! 4 * Copyright (C) 2001-2003 Red Hat, Inc.
5 * Copyright © 2004-2010 David Woodhouse <dwm <<
6 * 5 *
7 * Created by Arjan van de Ven <arjanv@redhat. 6 * Created by Arjan van de Ven <arjanv@redhat.com>
8 * 7 *
9 * For licensing information, see the file 'LI 8 * For licensing information, see the file 'LICENCE' in this directory.
10 * 9 *
>> 10 * $Id: compr_rtime.c,v 1.11 2003/10/04 08:33:06 dwmw2 Exp $
11 * 11 *
12 * 12 *
13 * Very simple lz77-ish encoder. 13 * Very simple lz77-ish encoder.
14 * 14 *
15 * Theory of operation: Both encoder and decod 15 * Theory of operation: Both encoder and decoder have a list of "last
16 * occurrences" for every possible source-valu 16 * occurrences" for every possible source-value; after sending the
17 * first source-byte, the second byte indicate 17 * first source-byte, the second byte indicated the "run" length of
18 * matches 18 * matches
19 * 19 *
20 * The algorithm is intended to only send "who 20 * The algorithm is intended to only send "whole bytes", no bit-messing.
21 * 21 *
22 */ 22 */
23 23
24 #include <linux/kernel.h> 24 #include <linux/kernel.h>
25 #include <linux/types.h> 25 #include <linux/types.h>
26 #include <linux/errno.h> 26 #include <linux/errno.h>
27 #include <linux/string.h> !! 27 #include <linux/string.h>
28 #include <linux/jffs2.h> <<
29 #include "compr.h" <<
30 28
31 /* _compress returns the compressed size, -1 i 29 /* _compress returns the compressed size, -1 if bigger */
32 static int jffs2_rtime_compress(unsigned char !! 30 int jffs2_rtime_compress(unsigned char *data_in, unsigned char *cpage_out,
33 unsigned char !! 31 uint32_t *sourcelen, uint32_t *dstlen)
34 uint32_t *sour <<
35 { 32 {
36 unsigned short positions[256]; !! 33 short positions[256];
37 int outpos = 0; 34 int outpos = 0;
38 int pos=0; 35 int pos=0;
39 36
40 if (*dstlen <= 3) !! 37 memset(positions,0,sizeof(positions));
41 return -1; !! 38
42 <<
43 memset(positions,0,sizeof(positions)); <<
44 <<
45 while (pos < (*sourcelen) && outpos <= 39 while (pos < (*sourcelen) && outpos <= (*dstlen)-2) {
46 int backpos, runlen=0; 40 int backpos, runlen=0;
47 unsigned char value; 41 unsigned char value;
48 !! 42
49 value = data_in[pos]; 43 value = data_in[pos];
50 44
51 cpage_out[outpos++] = data_in[ 45 cpage_out[outpos++] = data_in[pos++];
52 !! 46
53 backpos = positions[value]; 47 backpos = positions[value];
54 positions[value]=pos; 48 positions[value]=pos;
55 !! 49
56 while ((backpos < pos) && (pos 50 while ((backpos < pos) && (pos < (*sourcelen)) &&
57 (data_in[pos]==data_in[ 51 (data_in[pos]==data_in[backpos++]) && (runlen<255)) {
58 pos++; 52 pos++;
59 runlen++; 53 runlen++;
60 } 54 }
61 cpage_out[outpos++] = runlen; 55 cpage_out[outpos++] = runlen;
62 } 56 }
63 57
64 if (outpos >= pos) { 58 if (outpos >= pos) {
65 /* We failed */ 59 /* We failed */
66 return -1; 60 return -1;
67 } 61 }
68 !! 62
69 /* Tell the caller how much we managed 63 /* Tell the caller how much we managed to compress, and how much space it took */
70 *sourcelen = pos; 64 *sourcelen = pos;
71 *dstlen = outpos; 65 *dstlen = outpos;
72 return 0; 66 return 0;
73 } !! 67 }
74 68
75 69
76 static int jffs2_rtime_decompress(unsigned cha !! 70 void jffs2_rtime_decompress(unsigned char *data_in, unsigned char *cpage_out,
77 unsigned cha !! 71 uint32_t srclen, uint32_t destlen)
78 uint32_t src <<
79 { 72 {
80 unsigned short positions[256]; !! 73 short positions[256];
81 int outpos = 0; 74 int outpos = 0;
82 int pos=0; 75 int pos=0;
83 !! 76
84 memset(positions,0,sizeof(positions)); !! 77 memset(positions,0,sizeof(positions));
85 !! 78
86 while (outpos<destlen) { 79 while (outpos<destlen) {
87 unsigned char value; 80 unsigned char value;
88 int backoffs; 81 int backoffs;
89 int repeat; 82 int repeat;
90 !! 83
91 value = data_in[pos++]; 84 value = data_in[pos++];
92 cpage_out[outpos++] = value; / 85 cpage_out[outpos++] = value; /* first the verbatim copied byte */
93 repeat = data_in[pos++]; 86 repeat = data_in[pos++];
94 backoffs = positions[value]; 87 backoffs = positions[value];
95 !! 88
96 positions[value]=outpos; 89 positions[value]=outpos;
97 if (repeat) { 90 if (repeat) {
98 if (backoffs + repeat 91 if (backoffs + repeat >= outpos) {
99 while(repeat) 92 while(repeat) {
100 cpage_ 93 cpage_out[outpos++] = cpage_out[backoffs++];
101 repeat 94 repeat--;
102 } 95 }
103 } else { 96 } else {
104 memcpy(&cpage_ 97 memcpy(&cpage_out[outpos],&cpage_out[backoffs],repeat);
105 outpos+=repeat !! 98 outpos+=repeat;
106 } 99 }
107 } 100 }
108 } !! 101 }
109 return 0; !! 102 }
110 } <<
111 <<
112 static struct jffs2_compressor jffs2_rtime_com <<
113 .priority = JFFS2_RTIME_PRIORITY, <<
114 .name = "rtime", <<
115 .compr = JFFS2_COMPR_RTIME, <<
116 .compress = &jffs2_rtime_compress, <<
117 .decompress = &jffs2_rtime_decompress, <<
118 #ifdef JFFS2_RTIME_DISABLED <<
119 .disabled = 1, <<
120 #else <<
121 .disabled = 0, <<
122 #endif <<
123 }; <<
124 103
125 int jffs2_rtime_init(void) <<
126 { <<
127 return jffs2_register_compressor(&jffs2_rt <<
128 } <<
129 104
130 void jffs2_rtime_exit(void) <<
131 { <<
132 jffs2_unregister_compressor(&jffs2_rtime_c <<
133 } <<
134 105
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