zlib 0.79

inffast.c

@@ -0,0 +1,148 @@
+/* inffast.c -- process literals and length/distance pairs fast
+ * Copyright (C) 1995 Mark Adler
+ * For conditions of distribution and use, see copyright notice in zlib.h 
+ */
+
+#include "zutil.h"
+#include "inftrees.h"
+#include "infutil.h"
+#include "inffast.h"
+
+/* simplify the use of the inflate_huft type with some defines */
+#define base more.Base
+#define next more.Next
+#define exop word.what.Exop
+#define bits word.what.Bits
+
+/* macros for bit input with no checking and for returning unused bytes */
+#ifdef DEBUG
+#  undef NEXTBYTE
+#  define NEXTBYTE (n--?0:fprintf(stderr,"inffast underrun\n"),*p++)
+#endif
+#define GRABBITS(j) {while(k<(j)){b|=((uLong)NEXTBYTE)<<k;k+=8;}}
+#define UNGRAB {n+=(c=k>>3);p-=c;k&=7;}
+
+/* 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. */
+
+int inflate_fast(bl, bd, tl, td, s, z)
+uInt bl, bd;
+inflate_huft *tl, *td;
+struct inflate_blocks_state *s;
+z_stream *z;
+{
+  inflate_huft *t;	/* temporary pointer */
+  int e;		/* extra bits or operation */
+  uLong b;		/* bit buffer */
+  uInt k;		/* bits in bit buffer */
+  Byte *p;		/* input data pointer */
+  uInt n;		/* bytes available there */
+  Byte *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 */
+  Byte *r;		/* copy source pointer */
+
+  /* load input, output, bit values */
+  LOAD
+
+  /* initialize masks in registers */
+  ml = inflate_mask[bl];
+  md = inflate_mask[bd];
+
+  /* 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)
+      do {
+	if (e == -128)
+	{
+	  z->msg = "invalid literal/length code";
+          UNGRAB
+	  UPDATE
+	  return Z_DATA_ERROR;
+	}
+	DUMPBITS(t->bits)
+	e = -e;
+	if (e & 64)		/* end of block */
+	{
+          UNGRAB
+	  UPDATE
+	  return Z_STREAM_END;
+	}
+      } while ((e = (t = t->next + ((uInt)b & inflate_mask[e]))->exop) < 0);
+    DUMPBITS(t->bits)
+
+    /* process literal or length (end of block already trapped) */
+    if (e & 16)			/* then it's a literal */
+    {
+      *q++ = (Byte)t->base;
+      m--;
+    }
+    else			/* it's a length */
+    {
+      /* get length of block to copy (already have extra bits) */
+      c = t->base + ((uInt)b & inflate_mask[e]);
+      DUMPBITS(e);
+
+      /* decode distance base of block to copy */
+      GRABBITS(15);		/* max bits for distance code */
+      if ((e = (t = td + ((uInt)b & md))->exop) < 0)
+	do {
+	  if (e == -128)
+	  {
+	    z->msg = "invalid distance code";
+	    UNGRAB
+	    UPDATE
+	    return Z_DATA_ERROR;
+	  }
+	  DUMPBITS(t->bits)
+	  e = -e;
+	} while ((e = (t = t->next + ((uInt)b & inflate_mask[e]))->exop) < 0);
+      DUMPBITS(t->bits)
+
+      /* get extra bits to add to distance base */
+      GRABBITS(e)           /* get extra bits (up to 13) */
+      d = t->base + ((uInt)b & inflate_mask[e]);
+      DUMPBITS(e)
+
+      /* do the copy */
+      m -= c;
+      if (q - s->window >= d)		/* if offset before destination, */
+      {					/*  just copy */
+	r = q - d;
+	*q++ = *r++;  c--;		/* minimum count is three, */
+	*q++ = *r++;  c--;		/*  so unroll loop a little */
+	do {
+	  *q++ = *r++;
+	} while (--c);
+      }
+      else				/* else offset after destination */
+      {
+	e = d - (q - s->window);	/* bytes from offset to end */
+	r = s->end - e;			/* pointer to offset */
+	if (c > e)			/* if source crosses, */
+	{
+	  c -= e;			/* copy to end of window */
+	  do {
+	    *q++ = *r++;
+	  } while (--e);
+	  r = s->window;		/* copy rest from start of window */
+	}
+	do {				/* copy all or what's left */
+	  *q++ = *r++;
+	} while (--c);
+      }
+    }
+  } while (m >= 258 && n >= 10);
+
+  /* not enough input or output--restore pointers and return */
+  UNGRAB
+  UPDATE
+  return Z_OK;
+}