Module Name: src
Committed By: dsl
Date: Wed Sep 16 20:56:39 UTC 2009
Modified Files:
src/usr.bin/sort: fields.c
Log Message:
Minor tweaks to the key generation for numeric fields.
Use 1's compliment for -ve numbers to avoid confitionals.
To generate a diff of this commit:
cvs rdiff -u -r1.28 -r1.29 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:1.28 src/usr.bin/sort/fields.c:1.29
--- src/usr.bin/sort/fields.c:1.28 Thu Sep 10 22:02:40 2009
+++ src/usr.bin/sort/fields.c Wed Sep 16 20:56:38 2009
@@ -1,4 +1,4 @@
-/* $NetBSD: fields.c,v 1.28 2009/09/10 22:02:40 dsl Exp $ */
+/* $NetBSD: fields.c,v 1.29 2009/09/16 20:56:38 dsl Exp $ */
/*-
* Copyright (c) 2000-2003 The NetBSD Foundation, Inc.
@@ -66,7 +66,7 @@
#include "sort.h"
#ifndef lint
-__RCSID("$NetBSD: fields.c,v 1.28 2009/09/10 22:02:40 dsl Exp $");
+__RCSID("$NetBSD: fields.c,v 1.29 2009/09/16 20:56:38 dsl Exp $");
__SCCSID("@(#)fields.c 8.1 (Berkeley) 6/6/93");
#endif /* not lint */
@@ -232,21 +232,22 @@
* exponent. These have to be ordered (-ve value, decreasing exponent),
* zero, (+ve value, increasing exponent).
*
- * The first byte is 0x80 for zero, 0x40 for -ve with exponent 0 and
- * 0xc0 for +ve with exponent zero.
- * This only leaves 62 byte values for +ve exponents - which isn't enough.
+ * The first byte is 0x80 for zero, 0xc0 for +ve with exponent 0.
+ * -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,
+ * This lets us sort exponents from -2^31 to +2^31.
*
* The mantissa is stored 2 digits per byte offset by 0x40, for negative
- * numbers the order must be reversed (they are subtracted from 0x100).
+ * numbers the order must be reversed (they are bit inverted).
*
* Reverse sorts are done by inverting the sign of the number.
*/
-#define SIGNED(reverse, value) ((reverse) ? 0x100 - (value) : (value))
-
-/* Large exponents are encoded EXP_EXC_BITS per byte */
+/* 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)
@@ -262,8 +263,12 @@
char ch;
unsigned int val;
u_char *last_nz_pos;
+ u_char negate;
- reverse &= R;
+ if (reverse & R)
+ negate = 0xff;
+ else
+ negate = 0;
/* Give ourselves space for the key terminator */
bufend--;
@@ -274,7 +279,7 @@
SKIP_BLANKS(line);
if (*line == '-') { /* set the sign */
- reverse ^= R;
+ negate ^= 0xff;
line++;
}
/* eat initial zeroes */
@@ -304,11 +309,11 @@
/* Maybe here we should allow for e+12 (etc) */
- if (exponent < 0x3f - MAX_EXP_ENC && -exponent < 0x3f - MAX_EXP_ENC) {
+ if (exponent < 0x40 - MAX_EXP_ENC && -exponent < 0x40 - MAX_EXP_ENC) {
/* Value ok for simple encoding */
/* exponent 0 is 0xc0 for +ve numbers and 0x40 for -ve ones */
exponent += 0xc0;
- *pos++ = SIGNED(reverse, exponent);
+ *pos++ = negate ^ exponent;
} else {
/* Out or range for a single byte */
int c, t;
@@ -326,12 +331,12 @@
if (exponent < 0)
t = -t;
t += 0xc0;
- *pos++ = SIGNED(reverse, t);
+ *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++ = SIGNED(reverse, t);
+ *pos++ = negate ^ t;
}
}
@@ -360,13 +365,13 @@
val += ch - '0';
break;
}
- *pos++ = SIGNED(reverse, val + 0x40);
+ *pos++ = negate ^ (val + 0x40);
if (val != 0)
last_nz_pos = pos;
}
/* Add key terminator, deleting any trailing "00" */
- *last_nz_pos++ = SIGNED(reverse, 1);
+ *last_nz_pos++ = negate;
return (last_nz_pos);
}
