1 // SPDX-License-Identifier: BSD-2-Clause
2 /*
3 LZ4 - Fast LZ compression algorithm
4 Copyright (C) 2011-2015, Yann Collet.
5
6 You can contact the author at :
7 - LZ4 source repository : https://github.com/Cyan4973/lz4
8 - LZ4 public forum : https://groups.google.com/forum/#!forum/lz4c
9 */
10
11
12 /**************************************
13 * Reading and writing into memory
14 **************************************/
15
16 /* customized version of memcpy, which may overwrite up to 7 bytes beyond dstEnd */
LZ4_wildCopy(void * dstPtr,const void * srcPtr,void * dstEnd)17 static void LZ4_wildCopy(void* dstPtr, const void* srcPtr, void* dstEnd)
18 {
19 BYTE* d = (BYTE*)dstPtr;
20 const BYTE* s = (const BYTE*)srcPtr;
21 BYTE* e = (BYTE*)dstEnd;
22 do { LZ4_copy8(d,s); d+=8; s+=8; } while (d<e);
23 }
24
25
26 /**************************************
27 * Common Constants
28 **************************************/
29 #define MINMATCH 4
30
31 #define COPYLENGTH 8
32 #define LASTLITERALS 5
33 #define MFLIMIT (COPYLENGTH+MINMATCH)
34 static const int LZ4_minLength = (MFLIMIT+1);
35
36 #define KB *(1 <<10)
37 #define MB *(1 <<20)
38 #define GB *(1U<<30)
39
40 #define MAXD_LOG 16
41 #define MAX_DISTANCE ((1 << MAXD_LOG) - 1)
42
43 #define ML_BITS 4
44 #define ML_MASK ((1U<<ML_BITS)-1)
45 #define RUN_BITS (8-ML_BITS)
46 #define RUN_MASK ((1U<<RUN_BITS)-1)
47
48
49 /**************************************
50 * Local Structures and types
51 **************************************/
52 typedef enum { noDict = 0, withPrefix64k, usingExtDict } dict_directive;
53 typedef enum { endOnOutputSize = 0, endOnInputSize = 1 } endCondition_directive;
54 typedef enum { full = 0, partial = 1 } earlyEnd_directive;
55
56
57
58 /*******************************
59 * Decompression functions
60 *******************************/
61 /*
62 * This generic decompression function cover all use cases.
63 * It shall be instantiated several times, using different sets of directives
64 * Note that it is essential this generic function is really inlined,
65 * in order to remove useless branches during compilation optimization.
66 */
LZ4_decompress_generic(const char * const source,char * const dest,int inputSize,int outputSize,int endOnInput,int partialDecoding,int targetOutputSize,int dict,const BYTE * const lowPrefix,const BYTE * const dictStart,const size_t dictSize)67 FORCE_INLINE int LZ4_decompress_generic(
68 const char* const source,
69 char* const dest,
70 int inputSize,
71 int outputSize, /* If endOnInput==endOnInputSize, this value is the max size of Output Buffer. */
72
73 int endOnInput, /* endOnOutputSize, endOnInputSize */
74 int partialDecoding, /* full, partial */
75 int targetOutputSize, /* only used if partialDecoding==partial */
76 int dict, /* noDict, withPrefix64k, usingExtDict */
77 const BYTE* const lowPrefix, /* == dest if dict == noDict */
78 const BYTE* const dictStart, /* only if dict==usingExtDict */
79 const size_t dictSize /* note : = 0 if noDict */
80 )
81 {
82 /* Local Variables */
83 const BYTE* ip = (const BYTE*) source;
84 const BYTE* const iend = ip + inputSize;
85
86 BYTE* op = (BYTE*) dest;
87 BYTE* const oend = op + outputSize;
88 BYTE* cpy;
89 BYTE* oexit = op + targetOutputSize;
90 const BYTE* const lowLimit = lowPrefix - dictSize;
91
92 const BYTE* const dictEnd = (const BYTE*)dictStart + dictSize;
93 const size_t dec32table[] = {4, 1, 2, 1, 4, 4, 4, 4};
94 const size_t dec64table[] = {0, 0, 0, (size_t)-1, 0, 1, 2, 3};
95
96 const int safeDecode = (endOnInput==endOnInputSize);
97 const int checkOffset = ((safeDecode) && (dictSize < (int)(64 KB)));
98
99
100 /* Special cases */
101 if ((partialDecoding) && (oexit> oend-MFLIMIT)) oexit = oend-MFLIMIT; /* targetOutputSize too high => decode everything */
102 if ((endOnInput) && (unlikely(outputSize==0))) return ((inputSize==1) && (*ip==0)) ? 0 : -1; /* Empty output buffer */
103 if ((!endOnInput) && (unlikely(outputSize==0))) return (*ip==0?1:-1);
104
105
106 /* Main Loop */
107 while (1)
108 {
109 unsigned token;
110 size_t length;
111 const BYTE* match;
112
113 /* get literal length */
114 token = *ip++;
115 if ((length=(token>>ML_BITS)) == RUN_MASK)
116 {
117 unsigned s;
118 do
119 {
120 s = *ip++;
121 length += s;
122 }
123 while (likely((endOnInput)?ip<iend-RUN_MASK:1) && (s==255));
124 if ((safeDecode) && unlikely((size_t)(op+length)<(size_t)(op))) goto _output_error; /* overflow detection */
125 if ((safeDecode) && unlikely((size_t)(ip+length)<(size_t)(ip))) goto _output_error; /* overflow detection */
126 }
127
128 /* copy literals */
129 cpy = op+length;
130 if (((endOnInput) && ((cpy>(partialDecoding?oexit:oend-MFLIMIT)) || (ip+length>iend-(2+1+LASTLITERALS))) )
131 || ((!endOnInput) && (cpy>oend-COPYLENGTH)))
132 {
133 if (partialDecoding)
134 {
135 if (cpy > oend) goto _output_error; /* Error : write attempt beyond end of output buffer */
136 if ((endOnInput) && (ip+length > iend)) goto _output_error; /* Error : read attempt beyond end of input buffer */
137 }
138 else
139 {
140 if ((!endOnInput) && (cpy != oend)) goto _output_error; /* Error : block decoding must stop exactly there */
141 if ((endOnInput) && ((ip+length != iend) || (cpy > oend))) goto _output_error; /* Error : input must be consumed */
142 }
143 memcpy(op, ip, length);
144 ip += length;
145 op += length;
146 break; /* Necessarily EOF, due to parsing restrictions */
147 }
148 LZ4_wildCopy(op, ip, cpy);
149 ip += length; op = cpy;
150
151 /* get offset */
152 match = cpy - LZ4_readLE16(ip); ip+=2;
153 if ((checkOffset) && (unlikely(match < lowLimit))) goto _output_error; /* Error : offset outside destination buffer */
154
155 /* get matchlength */
156 length = token & ML_MASK;
157 if (length == ML_MASK)
158 {
159 unsigned s;
160 do
161 {
162 if ((endOnInput) && (ip > iend-LASTLITERALS)) goto _output_error;
163 s = *ip++;
164 length += s;
165 } while (s==255);
166 if ((safeDecode) && unlikely((size_t)(op+length)<(size_t)op)) goto _output_error; /* overflow detection */
167 }
168 length += MINMATCH;
169
170 /* check external dictionary */
171 if ((dict==usingExtDict) && (match < lowPrefix))
172 {
173 if (unlikely(op+length > oend-LASTLITERALS)) goto _output_error; /* doesn't respect parsing restriction */
174
175 if (length <= (size_t)(lowPrefix-match))
176 {
177 /* match can be copied as a single segment from external dictionary */
178 match = dictEnd - (lowPrefix-match);
179 memmove(op, match, length); op += length;
180 }
181 else
182 {
183 /* match encompass external dictionary and current segment */
184 size_t copySize = (size_t)(lowPrefix-match);
185 memcpy(op, dictEnd - copySize, copySize);
186 op += copySize;
187 copySize = length - copySize;
188 if (copySize > (size_t)(op-lowPrefix)) /* overlap within current segment */
189 {
190 BYTE* const endOfMatch = op + copySize;
191 const BYTE* copyFrom = lowPrefix;
192 while (op < endOfMatch) *op++ = *copyFrom++;
193 }
194 else
195 {
196 memcpy(op, lowPrefix, copySize);
197 op += copySize;
198 }
199 }
200 continue;
201 }
202
203 /* copy repeated sequence */
204 cpy = op + length;
205 if (unlikely((op-match)<8))
206 {
207 const size_t dec64 = dec64table[op-match];
208 op[0] = match[0];
209 op[1] = match[1];
210 op[2] = match[2];
211 op[3] = match[3];
212 match += dec32table[op-match];
213 LZ4_copy4(op+4, match);
214 op += 8; match -= dec64;
215 } else { LZ4_copy8(op, match); op+=8; match+=8; }
216
217 if (unlikely(cpy>oend-12))
218 {
219 if (cpy > oend-LASTLITERALS) goto _output_error; /* Error : last LASTLITERALS bytes must be literals */
220 if (op < oend-8)
221 {
222 LZ4_wildCopy(op, match, oend-8);
223 match += (oend-8) - op;
224 op = oend-8;
225 }
226 while (op<cpy) *op++ = *match++;
227 }
228 else
229 LZ4_wildCopy(op, match, cpy);
230 op=cpy; /* correction */
231 }
232
233 /* end of decoding */
234 if (endOnInput)
235 return (int) (((char*)op)-dest); /* Nb of output bytes decoded */
236 else
237 return (int) (((const char*)ip)-source); /* Nb of input bytes read */
238
239 /* Overflow error detected */
240 _output_error:
241 return (int) (-(((const char*)ip)-source))-1;
242 }
243