/src/binutils-gdb/zlib/inffast.c

Source (jump to first uncovered line)
/* inffast.c -- fast decoding
 * Copyright (C) 1995-2017 Mark Adler
 * For conditions of distribution and use, see copyright notice in zlib.h
 */

#include "zutil.h"
#include "inftrees.h"
#include "inflate.h"
#include "inffast.h"

#ifdef ASMINF
#  pragma message("Assembler code may have bugs -- use at your own risk")
#else

/*
   Decode literal, length, and distance codes and write out the resulting
   literal and match bytes until either not enough input or output is
   available, an end-of-block is encountered, or a data error is encountered.
   When large enough input and output buffers are supplied to inflate(), for
   example, a 16K input buffer and a 64K output buffer, more than 95% of the
   inflate execution time is spent in this routine.

   Entry assumptions:

        state->mode == LEN
        strm->avail_in >= 6
        strm->avail_out >= 258
        start >= strm->avail_out
        state->bits < 8

   On return, state->mode is one of:

        LEN -- ran out of enough output space or enough available input
        TYPE -- reached end of block code, inflate() to interpret next block
        BAD -- error in block data

   Notes:

    - The maximum input bits used by a length/distance pair is 15 bits for the
      length code, 5 bits for the length extra, 15 bits for the distance code,
      and 13 bits for the distance extra.  This totals 48 bits, or six bytes.
      Therefore if strm->avail_in >= 6, then there is enough input to avoid
      checking for available input while decoding.

    - The maximum bytes that a single length/distance pair can output is 258
      bytes, which is the maximum length that can be coded.  inflate_fast()
      requires strm->avail_out >= 258 for each loop to avoid checking for
      output space.
 */
void ZLIB_INTERNAL inflate_fast(strm, start)
z_streamp strm;
unsigned start;         /* inflate()'s starting value for strm->avail_out */
{
    struct inflate_state FAR *state;
    z_const unsigned char FAR *in;      /* local strm->next_in */
    z_const unsigned char FAR *last;    /* have enough input while in < last */
    unsigned char FAR *out;     /* local strm->next_out */
    unsigned char FAR *beg;     /* inflate()'s initial strm->next_out */
    unsigned char FAR *end;     /* while out < end, enough space available */
#ifdef INFLATE_STRICT
    unsigned dmax;              /* maximum distance from zlib header */
#endif
    unsigned wsize;             /* window size or zero if not using window */
    unsigned whave;             /* valid bytes in the window */
    unsigned wnext;             /* window write index */
    unsigned char FAR *window;  /* allocated sliding window, if wsize != 0 */
    unsigned long hold;         /* local strm->hold */
    unsigned bits;              /* local strm->bits */
    code const FAR *lcode;      /* local strm->lencode */
    code const FAR *dcode;      /* local strm->distcode */
    unsigned lmask;             /* mask for first level of length codes */
    unsigned dmask;             /* mask for first level of distance codes */
    code const *here;           /* retrieved table entry */
    unsigned op;                /* code bits, operation, extra bits, or */
                                /*  window position, window bytes to copy */
    unsigned len;               /* match length, unused bytes */
    unsigned dist;              /* match distance */
    unsigned char FAR *from;    /* where to copy match from */

    /* copy state to local variables */
    state = (struct inflate_state FAR *)strm->state;
    in = strm->next_in;
    last = in + (strm->avail_in - 5);
    out = strm->next_out;
    beg = out - (start - strm->avail_out);
    end = out + (strm->avail_out - 257);
#ifdef INFLATE_STRICT
    dmax = state->dmax;
#endif
    wsize = state->wsize;
    whave = state->whave;
    wnext = state->wnext;
    window = state->window;
    hold = state->hold;
    bits = state->bits;
    lcode = state->lencode;
    dcode = state->distcode;
    lmask = (1U << state->lenbits) - 1;
    dmask = (1U << state->distbits) - 1;

    /* decode literals and length/distances until end-of-block or not enough
       input data or output space */
    do {
        if (bits < 15) {
            hold += (unsigned long)(*in++) << bits;
            bits += 8;
            hold += (unsigned long)(*in++) << bits;
            bits += 8;
        }
        here = lcode + (hold & lmask);
      dolen:
        op = (unsigned)(here->bits);
        hold >>= op;
        bits -= op;
        op = (unsigned)(here->op);
        if (op == 0) {                          /* literal */
            Tracevv((stderr, here->val >= 0x20 && here->val < 0x7f ?
                    "inflate:         literal '%c'\n" :
                    "inflate:         literal 0x%02x\n", here->val));
            *out++ = (unsigned char)(here->val);
        }
        else if (op & 16) {                     /* length base */
            len = (unsigned)(here->val);
            op &= 15;                           /* number of extra bits */
            if (op) {
                if (bits < op) {
                    hold += (unsigned long)(*in++) << bits;
                    bits += 8;
                }
                len += (unsigned)hold & ((1U << op) - 1);
                hold >>= op;
                bits -= op;
            }
            Tracevv((stderr, "inflate:         length %u\n", len));
            if (bits < 15) {
                hold += (unsigned long)(*in++) << bits;
                bits += 8;
                hold += (unsigned long)(*in++) << bits;
                bits += 8;
            }
            here = dcode + (hold & dmask);
          dodist:
            op = (unsigned)(here->bits);
            hold >>= op;
            bits -= op;
            op = (unsigned)(here->op);
            if (op & 16) {                      /* distance base */
                dist = (unsigned)(here->val);
                op &= 15;                       /* number of extra bits */
                if (bits < op) {
                    hold += (unsigned long)(*in++) << bits;
                    bits += 8;
                    if (bits < op) {
                        hold += (unsigned long)(*in++) << bits;
                        bits += 8;
                    }
                }
                dist += (unsigned)hold & ((1U << op) - 1);
#ifdef INFLATE_STRICT
                if (dist > dmax) {
                    strm->msg = (char *)"invalid distance too far back";
                    state->mode = BAD;
                    break;
                }
#endif
                hold >>= op;
                bits -= op;
                Tracevv((stderr, "inflate:         distance %u\n", dist));
                op = (unsigned)(out - beg);     /* max distance in output */
                if (dist > op) {                /* see if copy from window */
                    op = dist - op;             /* distance back in window */
                    if (op > whave) {
                        if (state->sane) {
                            strm->msg =
                                (char *)"invalid distance too far back";
                            state->mode = BAD;
                            break;
                        }
#ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR
                        if (len <= op - whave) {
                            do {
                                *out++ = 0;
                            } while (--len);
                            continue;
                        }
                        len -= op - whave;
                        do {
                            *out++ = 0;
                        } while (--op > whave);
                        if (op == 0) {
                            from = out - dist;
                            do {
                                *out++ = *from++;
                            } while (--len);
                            continue;
                        }
#endif
                    }
                    from = window;
                    if (wnext == 0) {           /* very common case */
                        from += wsize - op;
                        if (op < len) {         /* some from window */
                            len -= op;
                            do {
                                *out++ = *from++;
                            } while (--op);
                            from = out - dist;  /* rest from output */
                        }
                    }
                    else if (wnext < op) {      /* wrap around window */
                        from += wsize + wnext - op;
                        op -= wnext;
                        if (op < len) {         /* some from end of window */
                            len -= op;
                            do {
                                *out++ = *from++;
                            } while (--op);
                            from = window;
                            if (wnext < len) {  /* some from start of window */
                                op = wnext;
                                len -= op;
                                do {
                                    *out++ = *from++;
                                } while (--op);
                                from = out - dist;      /* rest from output */
                            }
                        }
                    }
                    else {                      /* contiguous in window */
                        from += wnext - op;
                        if (op < len) {         /* some from window */
                            len -= op;
                            do {
                                *out++ = *from++;
                            } while (--op);
                            from = out - dist;  /* rest from output */
                        }
                    }
                    while (len > 2) {
                        *out++ = *from++;
                        *out++ = *from++;
                        *out++ = *from++;
                        len -= 3;
                    }
                    if (len) {
                        *out++ = *from++;
                        if (len > 1)
                            *out++ = *from++;
                    }
                }
                else {
                    from = out - dist;          /* copy direct from output */
                    do {                        /* minimum length is three */
                        *out++ = *from++;
                        *out++ = *from++;
                        *out++ = *from++;
                        len -= 3;
                    } while (len > 2);
                    if (len) {
                        *out++ = *from++;
                        if (len > 1)
                            *out++ = *from++;
                    }
                }
            }
            else if ((op & 64) == 0) {          /* 2nd level distance code */
                here = dcode + here->val + (hold & ((1U << op) - 1));
                goto dodist;
            }
            else {
                strm->msg = (char *)"invalid distance code";
                state->mode = BAD;
                break;
            }
        }
        else if ((op & 64) == 0) {              /* 2nd level length code */
            here = lcode + here->val + (hold & ((1U << op) - 1));
            goto dolen;
        }
        else if (op & 32) {                     /* end-of-block */
            Tracevv((stderr, "inflate:         end of block\n"));
            state->mode = TYPE;
            break;
        }
        else {
            strm->msg = (char *)"invalid literal/length code";
            state->mode = BAD;
            break;
        }
    } while (in < last && out < end);

    /* return unused bytes (on entry, bits < 8, so in won't go too far back) */
    len = bits >> 3;
    in -= len;
    bits -= len << 3;
    hold &= (1U << bits) - 1;

    /* update state and return */
    strm->next_in = in;
    strm->next_out = out;
    strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last));
    strm->avail_out = (unsigned)(out < end ?
                                 257 + (end - out) : 257 - (out - end));
    state->hold = hold;
    state->bits = bits;
    return;
}

/*
   inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe):
   - Using bit fields for code structure
   - Different op definition to avoid & for extra bits (do & for table bits)
   - Three separate decoding do-loops for direct, window, and wnext == 0
   - Special case for distance > 1 copies to do overlapped load and store copy
   - Explicit branch predictions (based on measured branch probabilities)
   - Deferring match copy and interspersed it with decoding subsequent codes
   - Swapping literal/length else
   - Swapping window/direct else
   - Larger unrolled copy loops (three is about right)
   - Moving len -= 3 statement into middle of loop
 */

#endif /* !ASMINF */

Coverage Report

Created: 2025-06-24 06:45

Line	Count	Source (jump to first uncovered line)
1		/* inffast.c -- fast decoding
2		* Copyright (C) 1995-2017 Mark Adler
3		* For conditions of distribution and use, see copyright notice in zlib.h
4		*/
5
6		#include "zutil.h"
7		#include "inftrees.h"
8		#include "inflate.h"
9		#include "inffast.h"
10
11		#ifdef ASMINF
12		# pragma message("Assembler code may have bugs -- use at your own risk")
13		#else
14
15		/*
16		Decode literal, length, and distance codes and write out the resulting
17		literal and match bytes until either not enough input or output is
18		available, an end-of-block is encountered, or a data error is encountered.
19		When large enough input and output buffers are supplied to inflate(), for
20		example, a 16K input buffer and a 64K output buffer, more than 95% of the
21		inflate execution time is spent in this routine.
22
23		Entry assumptions:
24
25		state->mode == LEN
26		strm->avail_in >= 6
27		strm->avail_out >= 258
28		start >= strm->avail_out
29		state->bits < 8
30
31		On return, state->mode is one of:
32
33		LEN -- ran out of enough output space or enough available input
34		TYPE -- reached end of block code, inflate() to interpret next block
35		BAD -- error in block data
36
37		Notes:
38
39		- The maximum input bits used by a length/distance pair is 15 bits for the
40		length code, 5 bits for the length extra, 15 bits for the distance code,
41		and 13 bits for the distance extra. This totals 48 bits, or six bytes.
42		Therefore if strm->avail_in >= 6, then there is enough input to avoid
43		checking for available input while decoding.
44
45		- The maximum bytes that a single length/distance pair can output is 258
46		bytes, which is the maximum length that can be coded. inflate_fast()
47		requires strm->avail_out >= 258 for each loop to avoid checking for
48		output space.
49		*/
50		void ZLIB_INTERNAL inflate_fast(strm, start)
51		z_streamp strm;
52		unsigned start; /* inflate()'s starting value for strm->avail_out */
53	80	{
54	80	struct inflate_state FAR *state;
55	80	z_const unsigned char FAR in; / local strm->next_in */
56	80	z_const unsigned char FAR last; / have enough input while in < last */
57	80	unsigned char FAR out; / local strm->next_out */
58	80	unsigned char FAR beg; / inflate()'s initial strm->next_out */
59	80	unsigned char FAR end; / while out < end, enough space available */
60		#ifdef INFLATE_STRICT
61		unsigned dmax; /* maximum distance from zlib header */
62		#endif
63	80	unsigned wsize; /* window size or zero if not using window */
64	80	unsigned whave; /* valid bytes in the window */
65	80	unsigned wnext; /* window write index */
66	80	unsigned char FAR window; / allocated sliding window, if wsize != 0 */
67	80	unsigned long hold; /* local strm->hold */
68	80	unsigned bits; /* local strm->bits */
69	80	code const FAR lcode; / local strm->lencode */
70	80	code const FAR dcode; / local strm->distcode */
71	80	unsigned lmask; /* mask for first level of length codes */
72	80	unsigned dmask; /* mask for first level of distance codes */
73	80	code const here; / retrieved table entry */
74	80	unsigned op; /* code bits, operation, extra bits, or */
75		/* window position, window bytes to copy */
76	80	unsigned len; /* match length, unused bytes */
77	80	unsigned dist; /* match distance */
78	80	unsigned char FAR from; / where to copy match from */
79
80		/* copy state to local variables */
81	80	state = (struct inflate_state FAR *)strm->state;
82	80	in = strm->next_in;
83	80	last = in + (strm->avail_in - 5);
84	80	out = strm->next_out;
85	80	beg = out - (start - strm->avail_out);
86	80	end = out + (strm->avail_out - 257);
87		#ifdef INFLATE_STRICT
88		dmax = state->dmax;
89		#endif
90	80	wsize = state->wsize;
91	80	whave = state->whave;
92	80	wnext = state->wnext;
93	80	window = state->window;
94	80	hold = state->hold;
95	80	bits = state->bits;
96	80	lcode = state->lencode;
97	80	dcode = state->distcode;
98	80	lmask = (1U << state->lenbits) - 1;
99	80	dmask = (1U << state->distbits) - 1;
100
101		/* decode literals and length/distances until end-of-block or not enough
102		input data or output space */
103	13.2k	do {
104	13.2k	if (bits < 15) {
105	5.13k	hold += (unsigned long)(*in++) << bits;
106	5.13k	bits += 8;
107	5.13k	hold += (unsigned long)(*in++) << bits;
108	5.13k	bits += 8;
109	5.13k	}
110	13.2k	here = lcode + (hold & lmask);
111	13.2k	dolen:
112	13.2k	op = (unsigned)(here->bits);
113	13.2k	hold >>= op;
114	13.2k	bits -= op;
115	13.2k	op = (unsigned)(here->op);
116	13.2k	if (op == 0) { /* literal */
117	11.2k	Tracevv((stderr, here->val >= 0x20 && here->val < 0x7f ?
118	11.2k	"inflate: literal '%c'\n" :
119	11.2k	"inflate: literal 0x%02x\n", here->val));
120	11.2k	*out++ = (unsigned char)(here->val);
121	11.2k	}
122	2.01k	else if (op & 16) { /* length base */
123	2.00k	len = (unsigned)(here->val);
124	2.00k	op &= 15; /* number of extra bits */
125	2.00k	if (op) {
126	110	if (bits < op) {
127	0	hold += (unsigned long)(*in++) << bits;
128	0	bits += 8;
129	0	}
130	110	len += (unsigned)hold & ((1U << op) - 1);
131	110	hold >>= op;
132	110	bits -= op;
133	110	}
134	2.00k	Tracevv((stderr, "inflate: length %u\n", len));
135	2.00k	if (bits < 15) {
136	575	hold += (unsigned long)(*in++) << bits;
137	575	bits += 8;
138	575	hold += (unsigned long)(*in++) << bits;
139	575	bits += 8;
140	575	}
141	2.00k	here = dcode + (hold & dmask);
142	2.00k	dodist:
143	2.00k	op = (unsigned)(here->bits);
144	2.00k	hold >>= op;
145	2.00k	bits -= op;
146	2.00k	op = (unsigned)(here->op);
147	2.00k	if (op & 16) { /* distance base */
148	2.00k	dist = (unsigned)(here->val);
149	2.00k	op &= 15; /* number of extra bits */
150	2.00k	if (bits < op) {
151	0	hold += (unsigned long)(*in++) << bits;
152	0	bits += 8;
153	0	if (bits < op) {
154	0	hold += (unsigned long)(*in++) << bits;
155	0	bits += 8;
156	0	}
157	0	}
158	2.00k	dist += (unsigned)hold & ((1U << op) - 1);
159		#ifdef INFLATE_STRICT
160		if (dist > dmax) {
161		strm->msg = (char *)"invalid distance too far back";
162		state->mode = BAD;
163		break;
164		}
165		#endif
166	2.00k	hold >>= op;
167	2.00k	bits -= op;
168	2.00k	Tracevv((stderr, "inflate: distance %u\n", dist));
169	2.00k	op = (unsigned)(out - beg); /* max distance in output */
170	2.00k	if (dist > op) { /* see if copy from window */
171	19	op = dist - op; /* distance back in window */
172	19	if (op > whave) {
173	19	if (state->sane) {
174	19	strm->msg =
175	19	(char *)"invalid distance too far back";
176	19	state->mode = BAD;
177	19	break;
178	19	}
179		#ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR
180		if (len <= op - whave) {
181		do {
182		*out++ = 0;
183		} while (--len);
184		continue;
185		}
186		len -= op - whave;
187		do {
188		*out++ = 0;
189		} while (--op > whave);
190		if (op == 0) {
191		from = out - dist;
192		do {
193		out++ = from++;
194		} while (--len);
195		continue;
196		}
197		#endif
198	19	}
199	0	from = window;
200	0	if (wnext == 0) { /* very common case */
201	0	from += wsize - op;
202	0	if (op < len) { /* some from window */
203	0	len -= op;
204	0	do {
205	0	out++ = from++;
206	0	} while (--op);
207	0	from = out - dist; /* rest from output */
208	0	}
209	0	}
210	0	else if (wnext < op) { /* wrap around window */
211	0	from += wsize + wnext - op;
212	0	op -= wnext;
213	0	if (op < len) { /* some from end of window */
214	0	len -= op;
215	0	do {
216	0	out++ = from++;
217	0	} while (--op);
218	0	from = window;
219	0	if (wnext < len) { /* some from start of window */
220	0	op = wnext;
221	0	len -= op;
222	0	do {
223	0	out++ = from++;
224	0	} while (--op);
225	0	from = out - dist; /* rest from output */
226	0	}
227	0	}
228	0	}
229	0	else { /* contiguous in window */
230	0	from += wnext - op;
231	0	if (op < len) { /* some from window */
232	0	len -= op;
233	0	do {
234	0	out++ = from++;
235	0	} while (--op);
236	0	from = out - dist; /* rest from output */
237	0	}
238	0	}
239	0	while (len > 2) {
240	0	out++ = from++;
241	0	out++ = from++;
242	0	out++ = from++;
243	0	len -= 3;
244	0	}
245	0	if (len) {
246	0	out++ = from++;
247	0	if (len > 1)
248	0	out++ = from++;
249	0	}
250	0	}
251	1.98k	else {
252	1.98k	from = out - dist; /* copy direct from output */
253	3.87k	do { /* minimum length is three */
254	3.87k	out++ = from++;
255	3.87k	out++ = from++;
256	3.87k	out++ = from++;
257	3.87k	len -= 3;
258	3.87k	} while (len > 2);
259	1.98k	if (len) {
260	671	out++ = from++;
261	671	if (len > 1)
262	190	out++ = from++;
263	671	}
264	1.98k	}
265	2.00k	}
266	3	else if ((op & 64) == 0) { /* 2nd level distance code */
267	0	here = dcode + here->val + (hold & ((1U << op) - 1));
268	0	goto dodist;
269	0	}
270	3	else {
271	3	strm->msg = (char *)"invalid distance code";
272	3	state->mode = BAD;
273	3	break;
274	3	}
275	2.00k	}
276	7	else if ((op & 64) == 0) { /* 2nd level length code */
277	0	here = lcode + here->val + (hold & ((1U << op) - 1));
278	0	goto dolen;
279	0	}
280	7	else if (op & 32) { /* end-of-block */
281	6	Tracevv((stderr, "inflate: end of block\n"));
282	6	state->mode = TYPE;
283	6	break;
284	6	}
285	1	else {
286	1	strm->msg = (char *)"invalid literal/length code";
287	1	state->mode = BAD;
288	1	break;
289	1	}
290	13.2k	} while (in < last && out < end);
291
292		/* return unused bytes (on entry, bits < 8, so in won't go too far back) */
293	80	len = bits >> 3;
294	80	in -= len;
295	80	bits -= len << 3;
296	80	hold &= (1U << bits) - 1;
297
298		/* update state and return */
299	80	strm->next_in = in;
300	80	strm->next_out = out;
301	80	strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last));
302	80	strm->avail_out = (unsigned)(out < end ?
303	63	257 + (end - out) : 257 - (out - end));
304	80	state->hold = hold;
305	80	state->bits = bits;
306	80	return;
307	80	}
308
309		/*
310		inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe):
311		- Using bit fields for code structure
312		- Different op definition to avoid & for extra bits (do & for table bits)
313		- Three separate decoding do-loops for direct, window, and wnext == 0
314		- Special case for distance > 1 copies to do overlapped load and store copy
315		- Explicit branch predictions (based on measured branch probabilities)
316		- Deferring match copy and interspersed it with decoding subsequent codes
317		- Swapping literal/length else
318		- Swapping window/direct else
319		- Larger unrolled copy loops (three is about right)
320		- Moving len -= 3 statement into middle of loop
321		*/
322
323		#endif /* !ASMINF */