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/* inffast.c -- fast decoding
 * Copyright (C) 1995-2004 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"
 
#ifndef ASMINF
 
/* Allow machine dependent optimization for post-increment or pre-increment.
   Based on testing to date,
   Pre-increment preferred for:
   - PowerPC G3 (Adler)
   - MIPS R5000 (Randers-Pehrson)
   Post-increment preferred for:
   - none
   No measurable difference:
   - Pentium III (Anderson)
   - M68060 (Nikl)
 */
#ifdef POSTINC
#  define OFF 0
#  define PUP(a) *(a)++
#else
#  define OFF 1
#  define PUP(a) *++(a)
#endif
 
/*
   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 inflate_fast(strm, start)
z_streamp strm;
unsigned start;         /* inflate()'s starting value for strm->avail_out */
{
    struct inflate_state FAR *state;
    unsigned char FAR *in;      /* local strm->next_in */
    unsigned char FAR *last;    /* while in < last, enough input available */
    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 write;             /* 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 this;                  /* 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 - OFF;
    last = in + (strm->avail_in - 5);
    out = strm->next_out - OFF;
    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;
    write = state->write;
    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)(PUP(in)) << bits;
            bits += 8;
            hold += (unsigned long)(PUP(in)) << bits;
            bits += 8;
        }
        this = lcode[hold & lmask];
      dolen:
        op = (unsigned)(this.bits);
        hold >>= op;
        bits -= op;
        op = (unsigned)(this.op);
        if (op == 0) {                          /* literal */
            Tracevv((stderr, this.val >= 0x20 && this.val < 0x7f ?
                    "inflate:         literal '%c'\n" :
                    "inflate:         literal 0x%02x\n", this.val));
            PUP(out) = (unsigned char)(this.val);
        }
        else if (op & 16) {                     /* length base */
            len = (unsigned)(this.val);
            op &= 15;                           /* number of extra bits */
            if (op) {
                if (bits < op) {
                    hold += (unsigned long)(PUP(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)(PUP(in)) << bits;
                bits += 8;
                hold += (unsigned long)(PUP(in)) << bits;
                bits += 8;
            }
            this = dcode[hold & dmask];
          dodist:
            op = (unsigned)(this.bits);
            hold >>= op;
            bits -= op;
            op = (unsigned)(this.op);
            if (op & 16) {                      /* distance base */
                dist = (unsigned)(this.val);
                op &= 15;                       /* number of extra bits */
                if (bits < op) {
                    hold += (unsigned long)(PUP(in)) << bits;
                    bits += 8;
                    if (bits < op) {
                        hold += (unsigned long)(PUP(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) {
                        strm->msg = (char *)"invalid distance too far back";
                        state->mode = BAD;
                        break;
                    }
                    from = window - OFF;
                    if (write == 0) {           /* very common case */
                        from += wsize - op;
                        if (op < len) {         /* some from window */
                            len -= op;
                            do {
                                PUP(out) = PUP(from);
                            } while (--op);
                            from = out - dist;  /* rest from output */
                        }
                    }
                    else if (write < op) {      /* wrap around window */
                        from += wsize + write - op;
                        op -= write;
                        if (op < len) {         /* some from end of window */
                            len -= op;
                            do {
                                PUP(out) = PUP(from);
                            } while (--op);
                            from = window - OFF;
                            if (write < len) {  /* some from start of window */
                                op = write;
                                len -= op;
                                do {
                                    PUP(out) = PUP(from);
                                } while (--op);
                                from = out - dist;      /* rest from output */
                            }
                        }
                    }
                    else {                      /* contiguous in window */
                        from += write - op;
                        if (op < len) {         /* some from window */
                            len -= op;
                            do {
                                PUP(out) = PUP(from);
                            } while (--op);
                            from = out - dist;  /* rest from output */
                        }
                    }
                    while (len > 2) {
                        PUP(out) = PUP(from);
                        PUP(out) = PUP(from);
                        PUP(out) = PUP(from);
                        len -= 3;
                    }
                    if (len) {
                        PUP(out) = PUP(from);
                        if (len > 1)
                            PUP(out) = PUP(from);
                    }
                }
                else {
                    from = out - dist;          /* copy direct from output */
                    do {                        /* minimum length is three */
                        PUP(out) = PUP(from);
                        PUP(out) = PUP(from);
                        PUP(out) = PUP(from);
                        len -= 3;
                    } while (len > 2);
                    if (len) {
                        PUP(out) = PUP(from);
                        if (len > 1)
                            PUP(out) = PUP(from);
                    }
                }
            }
            else if ((op & 64) == 0) {          /* 2nd level distance code */
                this = dcode[this.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 */
            this = lcode[this.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 + OFF;
    strm->next_out = out + OFF;
    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 write == 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 */

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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [zlib/] [inffast.c] - Blame information for rev 775

Line No.	Rev	Author	Line
1	745	jeremybenn	`/* inffast.c -- fast decoding`
2			`* Copyright (C) 1995-2004 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			`#ifndef ASMINF`
12
13			`/* Allow machine dependent optimization for post-increment or pre-increment.`
14			`Based on testing to date,`
15			`Pre-increment preferred for:`
16			`- PowerPC G3 (Adler)`
17			`- MIPS R5000 (Randers-Pehrson)`
18			`Post-increment preferred for:`
19			`- none`
20			`No measurable difference:`
21			`- Pentium III (Anderson)`
22			`- M68060 (Nikl)`
23			`*/`
24			`#ifdef POSTINC`
25			`# define OFF 0`
26			`# define PUP(a) *(a)++`
27			`#else`
28			`# define OFF 1`
29			`# define PUP(a) *++(a)`
30			`#endif`
31
32			`/*`
33			`Decode literal, length, and distance codes and write out the resulting`
34			`literal and match bytes until either not enough input or output is`
35			`available, an end-of-block is encountered, or a data error is encountered.`
36			`When large enough input and output buffers are supplied to inflate(), for`
37			`example, a 16K input buffer and a 64K output buffer, more than 95% of the`
38			`inflate execution time is spent in this routine.`
39
40			`Entry assumptions:`
41
42			`state->mode == LEN`
43			`strm->avail_in >= 6`
44			`strm->avail_out >= 258`
45			`start >= strm->avail_out`
46			`state->bits < 8`
47
48			`On return, state->mode is one of:`
49
50			`LEN -- ran out of enough output space or enough available input`
51			`TYPE -- reached end of block code, inflate() to interpret next block`
52			`BAD -- error in block data`
53
54			`Notes:`
55
56			`- The maximum input bits used by a length/distance pair is 15 bits for the`
57			`length code, 5 bits for the length extra, 15 bits for the distance code,`
58			`and 13 bits for the distance extra. This totals 48 bits, or six bytes.`
59			`Therefore if strm->avail_in >= 6, then there is enough input to avoid`
60			`checking for available input while decoding.`
61
62			`- The maximum bytes that a single length/distance pair can output is 258`
63			`bytes, which is the maximum length that can be coded. inflate_fast()`
64			`requires strm->avail_out >= 258 for each loop to avoid checking for`
65			`output space.`
66			`*/`
67			`void inflate_fast(strm, start)`
68			`z_streamp strm;`
69			`unsigned start; /* inflate()'s starting value for strm->avail_out */`
70			`{`
71			`struct inflate_state FAR *state;`
72			`unsigned char FAR in; / local strm->next_in */`
73			`unsigned char FAR last; / while in < last, enough input available */`
74			`unsigned char FAR out; / local strm->next_out */`
75			`unsigned char FAR beg; / inflate()'s initial strm->next_out */`
76			`unsigned char FAR end; / while out < end, enough space available */`
77			`#ifdef INFLATE_STRICT`
78			`unsigned dmax; /* maximum distance from zlib header */`
79			`#endif`
80			`unsigned wsize; /* window size or zero if not using window */`
81			`unsigned whave; /* valid bytes in the window */`
82			`unsigned write; /* window write index */`
83			`unsigned char FAR window; / allocated sliding window, if wsize != 0 */`
84			`unsigned long hold; /* local strm->hold */`
85			`unsigned bits; /* local strm->bits */`
86			`code const FAR lcode; / local strm->lencode */`
87			`code const FAR dcode; / local strm->distcode */`
88			`unsigned lmask; /* mask for first level of length codes */`
89			`unsigned dmask; /* mask for first level of distance codes */`
90			`code this; /* retrieved table entry */`
91			`unsigned op; /* code bits, operation, extra bits, or */`
92			`/* window position, window bytes to copy */`
93			`unsigned len; /* match length, unused bytes */`
94			`unsigned dist; /* match distance */`
95			`unsigned char FAR from; / where to copy match from */`
96
97			`/* copy state to local variables */`
98			`state = (struct inflate_state FAR *)strm->state;`
99			`in = strm->next_in - OFF;`
100			`last = in + (strm->avail_in - 5);`
101			`out = strm->next_out - OFF;`
102			`beg = out - (start - strm->avail_out);`
103			`end = out + (strm->avail_out - 257);`
104			`#ifdef INFLATE_STRICT`
105			`dmax = state->dmax;`
106			`#endif`
107			`wsize = state->wsize;`
108			`whave = state->whave;`
109			`write = state->write;`
110			`window = state->window;`
111			`hold = state->hold;`
112			`bits = state->bits;`
113			`lcode = state->lencode;`
114			`dcode = state->distcode;`
115			`lmask = (1U << state->lenbits) - 1;`
116			`dmask = (1U << state->distbits) - 1;`
117
118			`/* decode literals and length/distances until end-of-block or not enough`
119			`input data or output space */`
120			`do {`
121			`if (bits < 15) {`
122			`hold += (unsigned long)(PUP(in)) << bits;`
123			`bits += 8;`
124			`hold += (unsigned long)(PUP(in)) << bits;`
125			`bits += 8;`
126			`}`
127			`this = lcode[hold & lmask];`
128			`dolen:`
129			`op = (unsigned)(this.bits);`
130			`hold >>= op;`
131			`bits -= op;`
132			`op = (unsigned)(this.op);`
133			`if (op == 0) { /* literal */`
134			`Tracevv((stderr, this.val >= 0x20 && this.val < 0x7f ?`
135			`"inflate: literal '%c'\n" :`
136			`"inflate: literal 0x%02x\n", this.val));`
137			`PUP(out) = (unsigned char)(this.val);`
138			`}`
139			`else if (op & 16) { /* length base */`
140			`len = (unsigned)(this.val);`
141			`op &= 15; /* number of extra bits */`
142			`if (op) {`
143			`if (bits < op) {`
144			`hold += (unsigned long)(PUP(in)) << bits;`
145			`bits += 8;`
146			`}`
147			`len += (unsigned)hold & ((1U << op) - 1);`
148			`hold >>= op;`
149			`bits -= op;`
150			`}`
151			`Tracevv((stderr, "inflate: length %u\n", len));`
152			`if (bits < 15) {`
153			`hold += (unsigned long)(PUP(in)) << bits;`
154			`bits += 8;`
155			`hold += (unsigned long)(PUP(in)) << bits;`
156			`bits += 8;`
157			`}`
158			`this = dcode[hold & dmask];`
159			`dodist:`
160			`op = (unsigned)(this.bits);`
161			`hold >>= op;`
162			`bits -= op;`
163			`op = (unsigned)(this.op);`
164			`if (op & 16) { /* distance base */`
165			`dist = (unsigned)(this.val);`
166			`op &= 15; /* number of extra bits */`
167			`if (bits < op) {`
168			`hold += (unsigned long)(PUP(in)) << bits;`
169			`bits += 8;`
170			`if (bits < op) {`
171			`hold += (unsigned long)(PUP(in)) << bits;`
172			`bits += 8;`
173			`}`
174			`}`
175			`dist += (unsigned)hold & ((1U << op) - 1);`
176			`#ifdef INFLATE_STRICT`
177			`if (dist > dmax) {`
178			`strm->msg = (char *)"invalid distance too far back";`
179			`state->mode = BAD;`
180			`break;`
181			`}`
182			`#endif`
183			`hold >>= op;`
184			`bits -= op;`
185			`Tracevv((stderr, "inflate: distance %u\n", dist));`
186			`op = (unsigned)(out - beg); /* max distance in output */`
187			`if (dist > op) { /* see if copy from window */`
188			`op = dist - op; /* distance back in window */`
189			`if (op > whave) {`
190			`strm->msg = (char *)"invalid distance too far back";`
191			`state->mode = BAD;`
192			`break;`
193			`}`
194			`from = window - OFF;`
195			`if (write == 0) { /* very common case */`
196			`from += wsize - op;`
197			`if (op < len) { /* some from window */`
198			`len -= op;`
199			`do {`
200			`PUP(out) = PUP(from);`
201			`} while (--op);`
202			`from = out - dist; /* rest from output */`
203			`}`
204			`}`
205			`else if (write < op) { /* wrap around window */`
206			`from += wsize + write - op;`
207			`op -= write;`
208			`if (op < len) { /* some from end of window */`
209			`len -= op;`
210			`do {`
211			`PUP(out) = PUP(from);`
212			`} while (--op);`
213			`from = window - OFF;`
214			`if (write < len) { /* some from start of window */`
215			`op = write;`
216			`len -= op;`
217			`do {`
218			`PUP(out) = PUP(from);`
219			`} while (--op);`
220			`from = out - dist; /* rest from output */`
221			`}`
222			`}`
223			`}`
224			`else { /* contiguous in window */`
225			`from += write - op;`
226			`if (op < len) { /* some from window */`
227			`len -= op;`
228			`do {`
229			`PUP(out) = PUP(from);`
230			`} while (--op);`
231			`from = out - dist; /* rest from output */`
232			`}`
233			`}`
234			`while (len > 2) {`
235			`PUP(out) = PUP(from);`
236			`PUP(out) = PUP(from);`
237			`PUP(out) = PUP(from);`
238			`len -= 3;`
239			`}`
240			`if (len) {`
241			`PUP(out) = PUP(from);`
242			`if (len > 1)`
243			`PUP(out) = PUP(from);`
244			`}`
245			`}`
246			`else {`
247			`from = out - dist; /* copy direct from output */`
248			`do { /* minimum length is three */`
249			`PUP(out) = PUP(from);`
250			`PUP(out) = PUP(from);`
251			`PUP(out) = PUP(from);`
252			`len -= 3;`
253			`} while (len > 2);`
254			`if (len) {`
255			`PUP(out) = PUP(from);`
256			`if (len > 1)`
257			`PUP(out) = PUP(from);`
258			`}`
259			`}`
260			`}`
261			`else if ((op & 64) == 0) { /* 2nd level distance code */`
262			`this = dcode[this.val + (hold & ((1U << op) - 1))];`
263			`goto dodist;`
264			`}`
265			`else {`
266			`strm->msg = (char *)"invalid distance code";`
267			`state->mode = BAD;`
268			`break;`
269			`}`
270			`}`
271			`else if ((op & 64) == 0) { /* 2nd level length code */`
272			`this = lcode[this.val + (hold & ((1U << op) - 1))];`
273			`goto dolen;`
274			`}`
275			`else if (op & 32) { /* end-of-block */`
276			`Tracevv((stderr, "inflate: end of block\n"));`
277			`state->mode = TYPE;`
278			`break;`
279			`}`
280			`else {`
281			`strm->msg = (char *)"invalid literal/length code";`
282			`state->mode = BAD;`
283			`break;`
284			`}`
285			`} while (in < last && out < end);`
286
287			`/* return unused bytes (on entry, bits < 8, so in won't go too far back) */`
288			`len = bits >> 3;`
289			`in -= len;`
290			`bits -= len << 3;`
291			`hold &= (1U << bits) - 1;`
292
293			`/* update state and return */`
294			`strm->next_in = in + OFF;`
295			`strm->next_out = out + OFF;`
296			`strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last));`
297			`strm->avail_out = (unsigned)(out < end ?`
298			`257 + (end - out) : 257 - (out - end));`
299			`state->hold = hold;`
300			`state->bits = bits;`
301			`return;`
302			`}`
303
304			`/*`
305			`inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe):`
306			`- Using bit fields for code structure`
307			`- Different op definition to avoid & for extra bits (do & for table bits)`
308			`- Three separate decoding do-loops for direct, window, and write == 0`
309			`- Special case for distance > 1 copies to do overlapped load and store copy`
310			`- Explicit branch predictions (based on measured branch probabilities)`
311			`- Deferring match copy and interspersed it with decoding subsequent codes`
312			`- Swapping literal/length else`
313			`- Swapping window/direct else`
314			`- Larger unrolled copy loops (three is about right)`
315			`- Moving len -= 3 statement into middle of loop`
316			`*/`
317
318			`#endif /* !ASMINF */`