zlib 1.2.0v1.2.0

1 files changed, 277 insertions, 162 deletions

diff --git a/inffast.c b/inffast.c
index aa7f1d4..8d145c2 100644
--- a/inffast.c
+++ b/inffast.c
@@ -1,183 +1,298 @@
-/* inffast.c -- process literals and length/distance pairs fast
- * Copyright (C) 1995-2002 Mark Adler
- * For conditions of distribution and use, see copyright notice in zlib.h 
+/* inffast.c -- fast decoding
+ * Copyright (C) 1995-2003 Mark Adler
+ * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
 #include "zutil.h"
 #include "inftrees.h"
-#include "infblock.h"
-#include "infcodes.h"
-#include "infutil.h"
+#include "inflate.h"
 #include "inffast.h"
 
-struct inflate_codes_state {int dummy;}; /* for buggy compilers */
+/* 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)
+ */
+#ifdef POSTINC
+#  define OFF 0
+#  define PUP(a) *(a)++
+#else
+#  define OFF 1
+#  define PUP(a) *++(a)
+#endif
 
-/* simplify the use of the inflate_huft type with some defines */
-#define exop word.what.Exop
-#define bits word.what.Bits
+/*
+   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.
 
-/* macros for bit input with no checking and for returning unused bytes */
-#define GRABBITS(j) {while(k<(j)){b|=((uLong)NEXTBYTE)<<k;k+=8;}}
-#define UNGRAB {c=z->avail_in-n;c=(k>>3)<c?k>>3:c;n+=c;p-=c;k-=c<<3;}
+   Entry assumptions:
 
-/* Called with number of bytes left to write in window at least 258
-   (the maximum string length) and number of input bytes available
-   at least ten.  The ten bytes are six bytes for the longest length/
-   distance pair plus four bytes for overloading the bit buffer. */
+        state->mode == LEN
+        strm->avail_in >= 6
+        strm->avail_out >= 258
+        start >= strm->avail_out
+        state->bits < 8
 
-int inflate_fast(bl, bd, tl, td, s, z)
-uInt bl, bd;
-inflate_huft *tl;
-inflate_huft *td; /* need separate declaration for Borland C++ */
-inflate_blocks_statef *s;
-z_streamp z;
-{
-  inflate_huft *t;      /* temporary pointer */
-  uInt e;               /* extra bits or operation */
-  uLong b;              /* bit buffer */
-  uInt k;               /* bits in bit buffer */
-  Bytef *p;             /* input data pointer */
-  uInt n;               /* bytes available there */
-  Bytef *q;             /* output window write pointer */
-  uInt m;               /* bytes to end of window or read pointer */
-  uInt ml;              /* mask for literal/length tree */
-  uInt md;              /* mask for distance tree */
-  uInt c;               /* bytes to copy */
-  uInt d;               /* distance back to copy from */
-  Bytef *r;             /* copy source pointer */
+   On return, state->mode is one of:
 
-  /* load input, output, bit values */
-  LOAD
+        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
 
-  /* initialize masks */
-  ml = inflate_mask[bl];
-  md = inflate_mask[bd];
+   Notes:
 
-  /* do until not enough input or output space for fast loop */
-  do {                          /* assume called with m >= 258 && n >= 10 */
-    /* get literal/length code */
-    GRABBITS(20)                /* max bits for literal/length code */
-    if ((e = (t = tl + ((uInt)b & ml))->exop) == 0)
-    {
-      DUMPBITS(t->bits)
-      Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ?
-                "inflate:         * literal '%c'\n" :
-                "inflate:         * literal 0x%02x\n", t->base));
-      *q++ = (Byte)t->base;
-      m--;
-      continue;
-    }
-    do {
-      DUMPBITS(t->bits)
-      if (e & 16)
-      {
-        /* get extra bits for length */
-        e &= 15;
-        c = t->base + ((uInt)b & inflate_mask[e]);
-        DUMPBITS(e)
-        Tracevv((stderr, "inflate:         * length %u\n", c));
+    - 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 */
+    unsigned wsize;             /* window size or zero if not using 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 */
 
-        /* decode distance base of block to copy */
-        GRABBITS(15);           /* max bits for distance code */
-        e = (t = td + ((uInt)b & md))->exop;
-        do {
-          DUMPBITS(t->bits)
-          if (e & 16)
-          {
-            /* get extra bits to add to distance base */
-            e &= 15;
-            GRABBITS(e)         /* get extra bits (up to 13) */
-            d = t->base + ((uInt)b & inflate_mask[e]);
-            DUMPBITS(e)
-            Tracevv((stderr, "inflate:         * distance %u\n", d));
+    /* 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);
+    wsize = state->wsize;
+    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;
 
-            /* do the copy */
-            m -= c;
-            r = q - d;
-            if (r < s->window)                  /* wrap if needed */
-            {
-              do {
-                r += s->end - s->window;        /* force pointer in window */
-              } while (r < s->window);          /* covers invalid distances */
-              e = s->end - r;
-              if (c > e)
-              {
-                c -= e;                         /* wrapped copy */
-                do {
-                    *q++ = *r++;
-                } while (--e);
-                r = s->window;
-                do {
-                    *q++ = *r++;
-                } while (--c);
-              }
-              else                              /* normal copy */
-              {
-                *q++ = *r++;  c--;
-                *q++ = *r++;  c--;
-                do {
-                    *q++ = *r++;
-                } while (--c);
-              }
+    /* 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 += 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;
             }
-            else                                /* normal copy */
-            {
-              *q++ = *r++;  c--;
-              *q++ = *r++;  c--;
-              do {
-                *q++ = *r++;
-              } while (--c);
+            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 += hold & ((1U << op) - 1);
+                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 */
+                    if (dist > wsize) {
+                        strm->msg = (char *)"invalid distance too far back";
+                        state->mode = BAD;
+                        break;
+                    }
+                    from = window - OFF;
+                    op = dist - op;             /* distance back in window */
+                    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 if ((e & 64) == 0)
-          {
-            t += t->base;
-            e = (t += ((uInt)b & inflate_mask[e]))->exop;
-          }
-          else
-          {
-            z->msg = (char*)"invalid distance code";
-            UNGRAB
-            UPDATE
-            return Z_DATA_ERROR;
-          }
-        } while (1);
-        break;
-      }
-      if ((e & 64) == 0)
-      {
-        t += t->base;
-        if ((e = (t += ((uInt)b & inflate_mask[e]))->exop) == 0)
-        {
-          DUMPBITS(t->bits)
-          Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ?
-                    "inflate:         * literal '%c'\n" :
-                    "inflate:         * literal 0x%02x\n", t->base));
-          *q++ = (Byte)t->base;
-          m--;
-          break;
         }
-      }
-      else if (e & 32)
-      {
-        Tracevv((stderr, "inflate:         * end of block\n"));
-        UNGRAB
-        UPDATE
-        return Z_STREAM_END;
-      }
-      else
-      {
-        z->msg = (char*)"invalid literal/length code";
-        UNGRAB
-        UPDATE
-        return Z_DATA_ERROR;
-      }
-    } while (1);
-  } while (m >= 258 && n >= 10);
+        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;
 
-  /* not enough input or output--restore pointers and return */
-  UNGRAB
-  UPDATE
-  return Z_OK;
+    /* 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
+ */