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