Module Name: src
Committed By: dsl
Date: Wed Oct 7 21:02:57 UTC 2009
Modified Files:
src/usr.bin/sort: fields.c
Log Message:
When encoding numbers, we can use all 8 bits for exponent values.
To generate a diff of this commit:
cvs rdiff -u -r1.29 -r1.30 src/usr.bin/sort/fields.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/usr.bin/sort/fields.c
diff -u src/usr.bin/sort/fields.c:1.29 src/usr.bin/sort/fields.c:1.30
--- src/usr.bin/sort/fields.c:1.29 Wed Sep 16 20:56:38 2009
+++ src/usr.bin/sort/fields.c Wed Oct 7 21:02:57 2009
@@ -1,4 +1,4 @@
-/* $NetBSD: fields.c,v 1.29 2009/09/16 20:56:38 dsl Exp $ */
+/* $NetBSD: fields.c,v 1.30 2009/10/07 21:02:57 dsl Exp $ */
/*-
* Copyright (c) 2000-2003 The NetBSD Foundation, Inc.
@@ -66,7 +66,7 @@
#include "sort.h"
#ifndef lint
-__RCSID("$NetBSD: fields.c,v 1.29 2009/09/16 20:56:38 dsl Exp $");
+__RCSID("$NetBSD: fields.c,v 1.30 2009/10/07 21:02:57 dsl Exp $");
__SCCSID("@(#)fields.c 8.1 (Berkeley) 6/6/93");
#endif /* not lint */
@@ -236,8 +236,8 @@
* -ve values are the 1's compliments (so 0x7f isn't used!).
*
* This only leaves 63 byte values for +ve exponents - which isn't enough.
- * The largest 5 exponent values are used to hold a byte count of the
- * number of following bytes that contain 7 exponent bits per byte,
+ * The largest 4 exponent values are used to hold a byte count of the
+ * number of following bytes that contain 8 exponent bits per byte,
* This lets us sort exponents from -2^31 to +2^31.
*
* The mantissa is stored 2 digits per byte offset by 0x40, for negative
@@ -245,13 +245,7 @@
*
* Reverse sorts are done by inverting the sign of the number.
*/
-
-/* Large exponents are encoded EXP_EXC_BITS per byte, MAX_EXP_ENC is the
- * number of bytes required to contain an exponent. */
-#define EXP_ENC_BITS 7
-#define EXP_ENC_VAL (1 << EXP_ENC_BITS)
-#define EXP_ENC_MASK (EXP_ENC_VAL - 1)
-#define MAX_EXP_ENC ((int)(sizeof(int) * 8 + (EXP_ENC_BITS-1))/EXP_ENC_BITS)
+#define MAX_EXP_ENC ((int)sizeof(int))
static u_char *
number(u_char *pos, const u_char *bufend, u_char *line, u_char *lineend,
@@ -318,29 +312,24 @@
/* Out or range for a single byte */
int c, t;
t = exponent > 0 ? exponent : -exponent;
- /* Count how many 7-bit blocks are needed */
+ /* Count how many 8-bit bytes are needed */
for (c = 0; ; c++) {
- t /= EXP_ENC_VAL;
+ t >>= 8;
if (t == 0)
break;
}
- /* 'c' better be 0..4 here - but probably 0..2 */
- t = c;
+ /* 'c' better be 0..3 here - but probably 0..1 */
/* Offset just outside valid range */
- t += 0x40 - MAX_EXP_ENC;
+ t = c + 0x40 - MAX_EXP_ENC;
if (exponent < 0)
t = -t;
- t += 0xc0;
- *pos++ = negate ^ t;
- /* now add each 7-bit block (offset 0x40..0xbf) */
- for (; c >= 0; c--) {
- t = exponent >> (c * EXP_ENC_BITS);
- t = (t & EXP_ENC_MASK) + 0x40;
- *pos++ = negate ^ t;
- }
+ *pos++ = negate ^ (t + 0xc0);
+ /* now add each byte, most significant first */
+ for (; c >= 0; c--)
+ *pos++ = negate ^ (exponent >> (c * 8));
}
- /* Now add mantissa, 2 digits per byte */
+ /* Finally add mantissa, 2 digits per byte */
for (last_nz_pos = pos; line < lineend; ) {
if (pos >= bufend)
return NULL;
