Release calc version 2.10.2t30

jump.h

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+/*
+ * Copyright (c) 1996 by Landon Curt Noll.  All Rights Reserved.
+ *
+ * Permission to use, copy, modify, and distribute this software and
+ * its documentation for any purpose and without fee is hereby granted,
+ * provided that the above copyright, this permission notice and text
+ * this comment, and the disclaimer below appear in all of the following:
+ *
+ *	supporting documentation
+ *	source copies
+ *	source works derived from this source
+ *	binaries derived from this source or from derived source
+ *
+ * LANDON CURT NOLL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
+ * EVENT SHALL LANDON CURT NOLL BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
+ * USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+ * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ *
+ * chongo was here	/\../\
+ */
+/*
+ * jump - trivial prime jump table
+ *
+ * If x is divisible by a trivial prime (2,3,5,7,11), then:
+ *
+ *		x + jmpindx[ (x>>1)%JMPMOD ]
+ *
+ * is the value of the smallest value > x that is not divisible by a
+ * trivial prime.  JMPMOD is the product of the odd trivial primes.
+ *
+ * This table is useful for skipping values that are obviously not prime
+ * by skipping values that are a multiple of trivial prime.
+ *
+ * If x is not divisible by a trivial prime, then:
+ *
+ *		x + jmp[ -jmpindx[(x>>1)%JMPMOD] ]
+ *
+ * is the value of the smallest value > x that is not divisible by a
+ * trivial prime.
+ *
+ * If jmpindx[y] > 0 (y = x mod JMPMOD*2), then it refers to an 'x' that
+ * is divisible by a trivial prime and jmpindx[y] is the offset to the next
+ * value that is not divisible.
+ *
+ * If jmpindx[y] <= 0, then 'x' is not divisible by a trivial prime and
+ * the negative of jmpindx[y] is the index into the jmp[] table.  We use
+ * successive values from jmp[] (wrapping around to the beginning when
+ * we move off the end of jmp[]) to move to higher and higher values
+ * that are not divisible by trivial primes.
+ *
+ * Instead of testing successive odd values, this system allows us to
+ * skip odd values divisible by trivial primes.  This is process on the
+ * average reduces the values we need to test by a factor of at least 2.4.
+ */
+
+#if !defined(JUMP_H)
+#define JUMP_H
+
+#include "have_const.h"
+
+/*
+ * trivial prime CONSTants
+ */
+#define JMPMOD (3*5*7*11)	/* product of odd trivial primes */
+#define JMPSIZE (2*4*6*10)	/* ints mod JMPMOD not div by trivial primes */
+#define JPRIME (prime+4)	/* pointer to first non-trivial prime */
+
+/* given x, return the index within jmpindx that applies */
+#define jmpmod(x) (((x)>>1)%JMPMOD)
+
+/* jmpindx table value */
+#define jmpindxval(x) (jmpindx[jmpmod(x)])
+
+/* return the smallest value >= x not divisible by a trivial prime */
+#define firstjmp(x,tmp) ((tmp) = jmpindxval(x), ((tmp) > 0) ? ((x)+(tmp)) : (x))
+
+/* given x not divisible by a trivial prime, return jmp[] index */
+#define jmpptr(x) (-jmpindxval(x))
+
+/* given a jmp pointer, return current jump increment and bump the pointer */
+#define nxtjmp(p) ( *( ((p)<lastjmp) ? ((p)++) : (((p)=jmp),lastjmp) ) )
+
+/* given a jmp pointer, return dec pointer and return previous jump increment */
+#define prevjmp(p) ( *( ((p)>jmp) ? (--(p)) : ((p)=lastjmp) ) )
+
+/*
+ * external jump tables
+ */
+extern CONST short jmpindx[];
+extern CONST unsigned char jmp[];
+extern CONST unsigned char *CONST lastjmp;
+
+#endif /* !JUMP_H */