/rust/registry/src/index.crates.io-6f17d22bba15001f/libz-sys-1.1.21/src/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(z_streamp strm, unsigned start) {
    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: 2025-06-16 06:50

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	26.3k	void ZLIB_INTERNAL inflate_fast(z_streamp strm, unsigned start) {
51	26.3k	struct inflate_state FAR *state;
52	26.3k	z_const unsigned char FAR in; / local strm->next_in */
53	26.3k	z_const unsigned char FAR last; / have enough input while in < last */
54	26.3k	unsigned char FAR out; / local strm->next_out */
55	26.3k	unsigned char FAR beg; / inflate()'s initial strm->next_out */
56	26.3k	unsigned char FAR end; / while out < end, enough space available */
57		#ifdef INFLATE_STRICT
58		unsigned dmax; /* maximum distance from zlib header */
59		#endif
60	26.3k	unsigned wsize; /* window size or zero if not using window */
61	26.3k	unsigned whave; /* valid bytes in the window */
62	26.3k	unsigned wnext; /* window write index */
63	26.3k	unsigned char FAR window; / allocated sliding window, if wsize != 0 */
64	26.3k	unsigned long hold; /* local strm->hold */
65	26.3k	unsigned bits; /* local strm->bits */
66	26.3k	code const FAR lcode; / local strm->lencode */
67	26.3k	code const FAR dcode; / local strm->distcode */
68	26.3k	unsigned lmask; /* mask for first level of length codes */
69	26.3k	unsigned dmask; /* mask for first level of distance codes */
70	26.3k	code const here; / retrieved table entry */
71	26.3k	unsigned op; /* code bits, operation, extra bits, or */
72		/* window position, window bytes to copy */
73	26.3k	unsigned len; /* match length, unused bytes */
74	26.3k	unsigned dist; /* match distance */
75	26.3k	unsigned char FAR from; / where to copy match from */
76
77		/* copy state to local variables */
78	26.3k	state = (struct inflate_state FAR *)strm->state;
79	26.3k	in = strm->next_in;
80	26.3k	last = in + (strm->avail_in - 5);
81	26.3k	out = strm->next_out;
82	26.3k	beg = out - (start - strm->avail_out);
83	26.3k	end = out + (strm->avail_out - 257);
84		#ifdef INFLATE_STRICT
85		dmax = state->dmax;
86		#endif
87	26.3k	wsize = state->wsize;
88	26.3k	whave = state->whave;
89	26.3k	wnext = state->wnext;
90	26.3k	window = state->window;
91	26.3k	hold = state->hold;
92	26.3k	bits = state->bits;
93	26.3k	lcode = state->lencode;
94	26.3k	dcode = state->distcode;
95	26.3k	lmask = (1U << state->lenbits) - 1;
96	26.3k	dmask = (1U << state->distbits) - 1;
97
98		/* decode literals and length/distances until end-of-block or not enough
99		input data or output space */
100	239M	do {
101	239M	if (bits < 15) {
102	164M	hold += (unsigned long)(*in++) << bits;
103	164M	bits += 8;
104	164M	hold += (unsigned long)(*in++) << bits;
105	164M	bits += 8;
106	164M	}
107	239M	here = lcode + (hold & lmask);
108	244M	dolen:
109	244M	op = (unsigned)(here->bits);
110	244M	hold >>= op;
111	244M	bits -= op;
112	244M	op = (unsigned)(here->op);
113	244M	if (op == 0) { /* literal */
114	76.4M	Tracevv((stderr, here->val >= 0x20 && here->val < 0x7f ?
115	76.4M	"inflate: literal '%c'\n" :
116	76.4M	"inflate: literal 0x%02x\n", here->val));
117	76.4M	*out++ = (unsigned char)(here->val);
118	76.4M	}
119	167M	else if (op & 16) { /* length base */
120	162M	len = (unsigned)(here->val);
121	162M	op &= 15; /* number of extra bits */
122	162M	if (op) {
123	84.6M	if (bits < op) {
124	0	hold += (unsigned long)(*in++) << bits;
125	0	bits += 8;
126	0	}
127	84.6M	len += (unsigned)hold & ((1U << op) - 1);
128	84.6M	hold >>= op;
129	84.6M	bits -= op;
130	84.6M	}
131	162M	Tracevv((stderr, "inflate: length %u\n", len));
132	162M	if (bits < 15) {
133	58.0M	hold += (unsigned long)(*in++) << bits;
134	58.0M	bits += 8;
135	58.0M	hold += (unsigned long)(*in++) << bits;
136	58.0M	bits += 8;
137	58.0M	}
138	162M	here = dcode + (hold & dmask);
139	165M	dodist:
140	165M	op = (unsigned)(here->bits);
141	165M	hold >>= op;
142	165M	bits -= op;
143	165M	op = (unsigned)(here->op);
144	165M	if (op & 16) { /* distance base */
145	162M	dist = (unsigned)(here->val);
146	162M	op &= 15; /* number of extra bits */
147	162M	if (bits < op) {
148	4.17M	hold += (unsigned long)(*in++) << bits;
149	4.17M	bits += 8;
150	4.17M	if (bits < op) {
151	0	hold += (unsigned long)(*in++) << bits;
152	0	bits += 8;
153	0	}
154	4.17M	}
155	162M	dist += (unsigned)hold & ((1U << op) - 1);
156		#ifdef INFLATE_STRICT
157		if (dist > dmax) {
158		strm->msg = (char *)"invalid distance too far back";
159		state->mode = BAD;
160		break;
161		}
162		#endif
163	162M	hold >>= op;
164	162M	bits -= op;
165	162M	Tracevv((stderr, "inflate: distance %u\n", dist));
166	162M	op = (unsigned)(out - beg); /* max distance in output */
167	162M	if (dist > op) { /* see if copy from window */
168	0	op = dist - op; /* distance back in window */
169	0	if (op > whave) {
170	0	if (state->sane) {
171	0	strm->msg =
172	0	(char *)"invalid distance too far back";
173	0	state->mode = BAD;
174	0	break;
175	0	}
176		#ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR
177		if (len <= op - whave) {
178		do {
179		*out++ = 0;
180		} while (--len);
181		continue;
182		}
183		len -= op - whave;
184		do {
185		*out++ = 0;
186		} while (--op > whave);
187		if (op == 0) {
188		from = out - dist;
189		do {
190		out++ = from++;
191		} while (--len);
192		continue;
193		}
194		#endif
195	0	}
196	0	from = window;
197	0	if (wnext == 0) { /* very common case */
198	0	from += wsize - op;
199	0	if (op < len) { /* some from window */
200	0	len -= op;
201	0	do {
202	0	out++ = from++;
203	0	} while (--op);
204	0	from = out - dist; /* rest from output */
205	0	}
206	0	}
207	0	else if (wnext < op) { /* wrap around window */
208	0	from += wsize + wnext - op;
209	0	op -= wnext;
210	0	if (op < len) { /* some from end of window */
211	0	len -= op;
212	0	do {
213	0	out++ = from++;
214	0	} while (--op);
215	0	from = window;
216	0	if (wnext < len) { /* some from start of window */
217	0	op = wnext;
218	0	len -= op;
219	0	do {
220	0	out++ = from++;
221	0	} while (--op);
222	0	from = out - dist; /* rest from output */
223	0	}
224	0	}
225	0	}
226	0	else { /* contiguous in window */
227	0	from += wnext - op;
228	0	if (op < len) { /* some from window */
229	0	len -= op;
230	0	do {
231	0	out++ = from++;
232	0	} while (--op);
233	0	from = out - dist; /* rest from output */
234	0	}
235	0	}
236	0	while (len > 2) {
237	0	out++ = from++;
238	0	out++ = from++;
239	0	out++ = from++;
240	0	len -= 3;
241	0	}
242	0	if (len) {
243	0	out++ = from++;
244	0	if (len > 1)
245	0	out++ = from++;
246	0	}
247	0	}
248	162M	else {
249	162M	from = out - dist; /* copy direct from output */
250	945M	do { /* minimum length is three */
251	945M	out++ = from++;
252	945M	out++ = from++;
253	945M	out++ = from++;
254	945M	len -= 3;
255	945M	} while (len > 2);
256	162M	if (len) {
257	106M	out++ = from++;
258	106M	if (len > 1)
259	50.4M	out++ = from++;
260	106M	}
261	162M	}
262	162M	}
263	2.39M	else if ((op & 64) == 0) { /* 2nd level distance code */
264	2.39M	here = dcode + here->val + (hold & ((1U << op) - 1));
265	2.39M	goto dodist;
266	2.39M	}
267	0	else {
268	0	strm->msg = (char *)"invalid distance code";
269	0	state->mode = BAD;
270	0	break;
271	0	}
272	165M	}
273	5.08M	else if ((op & 64) == 0) { /* 2nd level length code */
274	5.06M	here = lcode + here->val + (hold & ((1U << op) - 1));
275	5.06M	goto dolen;
276	5.06M	}
277	13.1k	else if (op & 32) { /* end-of-block */
278	13.1k	Tracevv((stderr, "inflate: end of block\n"));
279	13.1k	state->mode = TYPE;
280	13.1k	break;
281	13.1k	}
282	0	else {
283	0	strm->msg = (char *)"invalid literal/length code";
284	0	state->mode = BAD;
285	0	break;
286	0	}
287	244M	} while (in < last && out < end);
288
289		/* return unused bytes (on entry, bits < 8, so in won't go too far back) */
290	26.3k	len = bits >> 3;
291	26.3k	in -= len;
292	26.3k	bits -= len << 3;
293	26.3k	hold &= (1U << bits) - 1;
294
295		/* update state and return */
296	26.3k	strm->next_in = in;
297	26.3k	strm->next_out = out;
298	26.3k	strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last));
299	26.3k	strm->avail_out = (unsigned)(out < end ?
300	13.1k	257 + (end - out) : 257 - (out - end));
301	26.3k	state->hold = hold;
302	26.3k	state->bits = bits;
303	26.3k	return;
304	26.3k	}
305
306		/*
307		inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe):
308		- Using bit fields for code structure
309		- Different op definition to avoid & for extra bits (do & for table bits)
310		- Three separate decoding do-loops for direct, window, and wnext == 0
311		- Special case for distance > 1 copies to do overlapped load and store copy
312		- Explicit branch predictions (based on measured branch probabilities)
313		- Deferring match copy and interspersed it with decoding subsequent codes
314		- Swapping literal/length else
315		- Swapping window/direct else
316		- Larger unrolled copy loops (three is about right)
317		- Moving len -= 3 statement into middle of loop
318		*/
319
320		#endif /* !ASMINF */