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Minor tweaks to the key generation for numeric fields. 

Use 1's compliment for -ve numbers to avoid confitionals.
This commit is contained in:
dsl 2009-09-16 20:56:38 +00:00
parent 51827ae696
commit fe52672374
1 changed files with 22 additions and 17 deletions
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39
usr.bin/sort/fields.c
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@ -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 @@ enterfield(u_char *tablepos, const u_char *endkey, struct field *cur_fld,
* 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 @@ number(u_char *pos, const u_char *bufend, u_char *line, u_char *lineend,
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 @@ number(u_char *pos, const u_char *bufend, u_char *line, u_char *lineend,
SKIP_BLANKS(line);
if (*line == '-') { /* set the sign */
reverse ^= R;
negate ^= 0xff;
line++;
}
/* eat initial zeroes */
@ -304,11 +309,11 @@ number(u_char *pos, const u_char *bufend, u_char *line, u_char *lineend,
/* 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 @@ number(u_char *pos, const u_char *bufend, u_char *line, u_char *lineend,
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 @@ number(u_char *pos, const u_char *bufend, u_char *line, u_char *lineend,
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);
}