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postgresql/contrib/seg/seg.c

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Gene Selkov's SEG datatype (GiST example code)
2000-12-12 04:40:33 +08:00
/******************************************************************************
This file contains routines that can be bound to a Postgres backend and
called by the backend in the process of processing queries. The calling
format for these routines is dictated by Postgres architecture.
******************************************************************************/
#include "postgres.h"
#include <float.h>
#include "access/gist.h"
#include "access/rtree.h"
#include "utils/elog.h"
#include "utils/palloc.h"
#include "utils/builtins.h"
#include "segdata.h"
#define max(a,b) ((a) > (b) ? (a) : (b))
#define min(a,b) ((a) <= (b) ? (a) : (b))
#define abs(a) ((a) < (0) ? (-a) : (a))
/*
#define GIST_DEBUG
#define GIST_QUERY_DEBUG
*/
extern void set_parse_buffer(char *str);
extern int seg_yyparse();
/*
extern int seg_yydebug;
*/
/*
** Input/Output routines
*/
SEG * seg_in(char *str);
char * seg_out(SEG *seg);
float32 seg_lower(SEG *seg);
float32 seg_upper(SEG *seg);
float32 seg_center(SEG *seg);
/*
** GiST support methods
*/
bool gseg_consistent(GISTENTRY *entry, SEG *query, StrategyNumber strategy);
GISTENTRY * gseg_compress(GISTENTRY *entry);
GISTENTRY * gseg_decompress(GISTENTRY *entry);
float * gseg_penalty(GISTENTRY *origentry, GISTENTRY *newentry, float *result);
GIST_SPLITVEC * gseg_picksplit(bytea *entryvec, GIST_SPLITVEC *v);
bool gseg_leaf_consistent(SEG *key, SEG *query, StrategyNumber strategy);
bool gseg_internal_consistent(SEG *key, SEG *query, StrategyNumber strategy);
SEG * gseg_union(bytea *entryvec, int *sizep);
SEG * gseg_binary_union(SEG *r1, SEG *r2, int *sizep);
bool * gseg_same(SEG *b1, SEG *b2, bool *result);
/*
** R-tree suport functions
*/
bool seg_same(SEG *a, SEG *b);
bool seg_contains_int(SEG *a, int *b);
bool seg_contains_float4(SEG *a, float4 *b);
bool seg_contains_float8(SEG *a, float8 *b);
bool seg_contains(SEG *a, SEG *b);
bool seg_contained(SEG *a, SEG *b);
bool seg_overlap(SEG *a, SEG *b);
bool seg_left(SEG *a, SEG *b);
bool seg_over_left(SEG *a, SEG *b);
bool seg_right(SEG *a, SEG *b);
bool seg_over_right(SEG *a, SEG *b);
SEG * seg_union(SEG *a, SEG *b);
SEG * seg_inter(SEG *a, SEG *b);
void rt_seg_size(SEG *a, float* sz);
float * seg_size(SEG *a);
/*
** Various operators
*/
int32 seg_cmp(SEG *a, SEG *b);
bool seg_lt(SEG *a, SEG *b);
bool seg_le(SEG *a, SEG *b);
bool seg_gt(SEG *a, SEG *b);
bool seg_ge(SEG *a, SEG *b);
bool seg_different(SEG *a, SEG *b);
/*
** Auxiliary funxtions
*/
static int restore(char *s, float val, int n);
int significant_digits (char* s);
/*****************************************************************************
* Input/Output functions
*****************************************************************************/
SEG *
seg_in(char *str)
{
SEG * result = palloc(sizeof(SEG));
set_parse_buffer( str );
/*
seg_yydebug = 1;
*/
if ( seg_yyparse(result) != 0 ) {
pfree ( result );
return NULL;
}
return ( result );
}
/*
* You might have noticed a slight inconsistency between the following
* declaration and the SQL definition:
* CREATE FUNCTION seg_out(opaque) RETURNS opaque ...
* The reason is that the argument passed into seg_out is really just a
* pointer. POSTGRES thinks all output functions are:
* char *out_func(char *);
*/
char *
seg_out(SEG *seg)
{
char *result;
char *p;
if (seg == NULL) return(NULL);
p = result = (char *) palloc(40);
if ( seg->l_ext == '>' || seg->l_ext == '<' || seg->l_ext == '~' ) {
p += sprintf(p, "%c", seg->l_ext);
}
if ( seg->lower == seg->upper && seg->l_ext == seg->u_ext ) {
/* indicates that this interval was built by seg_in off a single point */
p += restore(p, seg->lower, seg->l_sigd);
}
else {
if ( seg->l_ext != '-' ) {
/* print the lower boudary if exists */
p += restore(p, seg->lower, seg->l_sigd);
p += sprintf(p, " ");
}
p += sprintf(p, "..");
if ( seg->u_ext != '-' ) {
/* print the upper boudary if exists */
p += sprintf(p, " ");
if ( seg->u_ext == '>' || seg->u_ext == '<' || seg->l_ext == '~' ) {
p += sprintf(p, "%c", seg->u_ext);
}
p += restore(p, seg->upper, seg->u_sigd);
}
}
return(result);
}
float32
seg_center(SEG *seg)
{
float32 result = (float32) palloc(sizeof(float32data));
if (!seg)
return (float32) NULL;
*result = ((float)seg->lower + (float)seg->upper)/2.0;
return (result);
}
float32
seg_lower(SEG *seg)
{
float32 result = (float32) palloc(sizeof(float32data));
if (!seg)
return (float32) NULL;
*result = (float)seg->lower;
return (result);
}
float32
seg_upper(SEG *seg)
{
float32 result = (float32) palloc(sizeof(float32data));
if (!seg)
return (float32) NULL;
*result = (float)seg->upper;
return (result);
}
/*****************************************************************************
* GiST functions
*****************************************************************************/
/*
** The GiST Consistent method for segments
** Should return false if for all data items x below entry,
** the predicate x op query == FALSE, where op is the oper
** corresponding to strategy in the pg_amop table.
*/
bool
gseg_consistent(GISTENTRY *entry,
SEG *query,
StrategyNumber strategy)
{
/*
** if entry is not leaf, use gseg_internal_consistent,
** else use gseg_leaf_consistent
*/
if (GIST_LEAF(entry))
return(gseg_leaf_consistent((SEG *)(entry->pred), query, strategy));
else
return(gseg_internal_consistent((SEG *)(entry->pred), query, strategy));
}
/*
** The GiST Union method for segments
** returns the minimal bounding seg that encloses all the entries in entryvec
*/
SEG *
gseg_union(bytea *entryvec, int *sizep)
{
int numranges, i;
SEG *out = (SEG *)NULL;
SEG *tmp;
#ifdef GIST_DEBUG
fprintf(stderr, "union\n");
#endif
numranges = (VARSIZE(entryvec) - VARHDRSZ)/sizeof(GISTENTRY);
tmp = (SEG *)(((GISTENTRY *)(VARDATA(entryvec)))[0]).pred;
*sizep = sizeof(SEG);
for (i = 1; i < numranges; i++) {
out = gseg_binary_union(tmp, (SEG *)
(((GISTENTRY *)(VARDATA(entryvec)))[i]).pred,
sizep);
#ifdef GIST_DEBUG
/*
fprintf(stderr, "\t%s ^ %s -> %s\n", seg_out(tmp), seg_out((SEG *)(((GISTENTRY *)(VARDATA(entryvec)))[i]).pred), seg_out(out));
*/
#endif
if (i > 1) pfree(tmp);
tmp = out;
}
return(out);
}
/*
** GiST Compress and Decompress methods for segments
** do not do anything.
*/
GISTENTRY *
gseg_compress(GISTENTRY *entry)
{
return(entry);
}
GISTENTRY *
gseg_decompress(GISTENTRY *entry)
{
return(entry);
}
/*
** The GiST Penalty method for segments
** As in the R-tree paper, we use change in area as our penalty metric
*/
float *
gseg_penalty(GISTENTRY *origentry, GISTENTRY *newentry, float *result)
{
Datum ud;
float tmp1, tmp2;
ud = (Datum)seg_union((SEG *)(origentry->pred), (SEG *)(newentry->pred));
rt_seg_size((SEG *)ud, &tmp1);
rt_seg_size((SEG *)(origentry->pred), &tmp2);
*result = tmp1 - tmp2;
pfree((char *)ud);
#ifdef GIST_DEBUG
fprintf(stderr, "penalty\n");
fprintf(stderr, "\t%g\n", *result);
#endif
return(result);
}
/*
** The GiST PickSplit method for segments
** We use Guttman's poly time split algorithm
*/
GIST_SPLITVEC *
gseg_picksplit(bytea *entryvec,
GIST_SPLITVEC *v)
{
OffsetNumber i, j;
SEG *datum_alpha, *datum_beta;
SEG *datum_l, *datum_r;
SEG *union_d, *union_dl, *union_dr;
SEG *inter_d;
bool firsttime;
float size_alpha, size_beta, size_union, size_inter;
float size_waste, waste;
float size_l, size_r;
int nbytes;
OffsetNumber seed_1 = 0, seed_2 = 0;
OffsetNumber *left, *right;
OffsetNumber maxoff;
#ifdef GIST_DEBUG
fprintf(stderr, "picksplit\n");
#endif
maxoff = ((VARSIZE(entryvec) - VARHDRSZ)/sizeof(GISTENTRY)) - 2;
nbytes = (maxoff + 2) * sizeof(OffsetNumber);
v->spl_left = (OffsetNumber *) palloc(nbytes);
v->spl_right = (OffsetNumber *) palloc(nbytes);
firsttime = true;
waste = 0.0;
for (i = FirstOffsetNumber; i < maxoff; i = OffsetNumberNext(i)) {
datum_alpha = (SEG *)(((GISTENTRY *)(VARDATA(entryvec)))[i].pred);
for (j = OffsetNumberNext(i); j <= maxoff; j = OffsetNumberNext(j)) {
datum_beta = (SEG *)(((GISTENTRY *)(VARDATA(entryvec)))[j].pred);
/* compute the wasted space by unioning these guys */
/* size_waste = size_union - size_inter; */
union_d = (SEG *)seg_union(datum_alpha, datum_beta);
rt_seg_size(union_d, &size_union);
inter_d = (SEG *)seg_inter(datum_alpha, datum_beta);
rt_seg_size(inter_d, &size_inter);
size_waste = size_union - size_inter;
pfree(union_d);
if (inter_d != (SEG *) NULL)
pfree(inter_d);
/*
* are these a more promising split that what we've
* already seen?
*/
if (size_waste > waste || firsttime) {
waste = size_waste;
seed_1 = i;
seed_2 = j;
firsttime = false;
}
}
}
left = v->spl_left;
v->spl_nleft = 0;
right = v->spl_right;
v->spl_nright = 0;
datum_alpha = (SEG *)(((GISTENTRY *)(VARDATA(entryvec)))[seed_1].pred);
datum_l = (SEG *)seg_union(datum_alpha, datum_alpha);
rt_seg_size((SEG *)datum_l, &size_l);
datum_beta = (SEG *)(((GISTENTRY *)(VARDATA(entryvec)))[seed_2].pred);;
datum_r = (SEG *)seg_union(datum_beta, datum_beta);
rt_seg_size((SEG *)datum_r, &size_r);
/*
* Now split up the regions between the two seeds. An important
* property of this split algorithm is that the split vector v
* has the indices of items to be split in order in its left and
* right vectors. We exploit this property by doing a merge in
* the code that actually splits the page.
*
* For efficiency, we also place the new index tuple in this loop.
* This is handled at the very end, when we have placed all the
* existing tuples and i == maxoff + 1.
*/
maxoff = OffsetNumberNext(maxoff);
for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i)) {
/*
* If we've already decided where to place this item, just
* put it on the right list. Otherwise, we need to figure
* out which page needs the least enlargement in order to
* store the item.
*/
if (i == seed_1) {
*left++ = i;
v->spl_nleft++;
continue;
} else if (i == seed_2) {
*right++ = i;
v->spl_nright++;
continue;
}
/* okay, which page needs least enlargement? */
datum_alpha = (SEG *)(((GISTENTRY *)(VARDATA(entryvec)))[i].pred);
union_dl = (SEG *)seg_union(datum_l, datum_alpha);
union_dr = (SEG *)seg_union(datum_r, datum_alpha);
rt_seg_size((SEG *)union_dl, &size_alpha);
rt_seg_size((SEG *)union_dr, &size_beta);
/* pick which page to add it to */
if (size_alpha - size_l < size_beta - size_r) {
pfree(datum_l);
pfree(union_dr);
datum_l = union_dl;
size_l = size_alpha;
*left++ = i;
v->spl_nleft++;
} else {
pfree(datum_r);
pfree(union_dl);
datum_r = union_dr;
size_r = size_alpha;
*right++ = i;
v->spl_nright++;
}
}
*left = *right = FirstOffsetNumber; /* sentinel value, see dosplit() */
v->spl_ldatum = (char *)datum_l;
v->spl_rdatum = (char *)datum_r;
return v;
}
/*
** Equality methods
*/
bool *
gseg_same(SEG *b1, SEG *b2, bool *result)
{
if (seg_same(b1, b2))
*result = TRUE;
else *result = FALSE;
#ifdef GIST_DEBUG
fprintf(stderr, "same: %s\n", (*result ? "TRUE" : "FALSE" ));
#endif
return(result);
}
/*
** SUPPORT ROUTINES
*/
bool
gseg_leaf_consistent(SEG *key,
SEG *query,
StrategyNumber strategy)
{
bool retval;
#ifdef GIST_QUERY_DEBUG
fprintf(stderr, "leaf_consistent, %d\n", strategy);
#endif
switch(strategy) {
case RTLeftStrategyNumber:
retval = (bool)seg_left(key, query);
break;
case RTOverLeftStrategyNumber:
retval = (bool)seg_over_left(key,query);
break;
case RTOverlapStrategyNumber:
retval = (bool)seg_overlap(key, query);
break;
case RTOverRightStrategyNumber:
retval = (bool)seg_over_right(key, query);
break;
case RTRightStrategyNumber:
retval = (bool)seg_right(key, query);
break;
case RTSameStrategyNumber:
retval = (bool)seg_same(key, query);
break;
case RTContainsStrategyNumber:
retval = (bool)seg_contains(key, query);
break;
case RTContainedByStrategyNumber:
retval = (bool)seg_contained(key,query);
break;
default:
retval = FALSE;
}
return(retval);
}
bool
gseg_internal_consistent(SEG *key,
SEG *query,
StrategyNumber strategy)
{
bool retval;
#ifdef GIST_QUERY_DEBUG
fprintf(stderr, "internal_consistent, %d\n", strategy);
#endif
switch(strategy) {
case RTLeftStrategyNumber:
case RTOverLeftStrategyNumber:
retval = (bool)seg_over_left(key,query);
break;
case RTOverlapStrategyNumber:
retval = (bool)seg_overlap(key, query);
break;
case RTOverRightStrategyNumber:
case RTRightStrategyNumber:
retval = (bool)seg_right(key, query);
break;
case RTSameStrategyNumber:
case RTContainsStrategyNumber:
retval = (bool)seg_contains(key, query);
break;
case RTContainedByStrategyNumber:
retval = (bool)seg_overlap(key, query);
break;
default:
retval = FALSE;
}
return(retval);
}
SEG *
gseg_binary_union(SEG *r1, SEG *r2, int *sizep)
{
SEG *retval;
retval = seg_union(r1, r2);
*sizep = sizeof(SEG);
return (retval);
}
bool
seg_contains(SEG *a, SEG *b)
{
return ( (a->lower <= b->lower) && (a->upper >= b->upper) );
}
bool
seg_contained(SEG *a, SEG *b)
{
return ( seg_contains(b, a) );
}
/*****************************************************************************
* Operator class for R-tree indexing
*****************************************************************************/
bool
seg_same(SEG *a, SEG *b)
{
return seg_cmp(a, b) == 0;
}
/* seg_overlap -- does a overlap b?
*/
bool
seg_overlap(SEG *a, SEG *b)
{
return (
((a->upper >= b->upper) && (a->lower <= b->upper))
||
((b->upper >= a->upper) && (b->lower <= a->upper))
);
}
/* seg_overleft -- is the right edge of (a) located to the left of the right edge of (b)?
*/
bool
seg_over_left(SEG *a, SEG *b)
{
return ( a->upper <= b->upper && !seg_left(a, b) && !seg_right(a, b));
}
/* seg_left -- is (a) entirely on the left of (b)?
*/
bool
seg_left(SEG *a, SEG *b)
{
return ( a->upper < b->lower );
}
/* seg_right -- is (a) entirely on the right of (b)?
*/
bool
seg_right(SEG *a, SEG *b)
{
return ( a->lower > b->upper );
}
/* seg_overright -- is the left edge of (a) located to the right of the left edge of (b)?
*/
bool
seg_over_right(SEG *a, SEG *b)
{
return (a->lower >= b->lower && !seg_left(a, b) && !seg_right(a, b));
}
SEG *
seg_union(SEG *a, SEG *b)
{
SEG *n;
n = (SEG *) palloc(sizeof(*n));
/* take max of upper endpoints */
if (a->upper > b->upper)
{
n->upper = a->upper;
n->u_sigd = a->u_sigd;
n->u_ext = a->u_ext;
}
else
{
n->upper = b->upper;
n->u_sigd = b->u_sigd;
n->u_ext = b->u_ext;
}
/* take min of lower endpoints */
if (a->lower < b->lower)
{
n->lower = a->lower;
n->l_sigd = a->l_sigd;
n->l_ext = a->l_ext;
}
else
{
n->lower = b->lower;
n->l_sigd = b->l_sigd;
n->l_ext = b->l_ext;
}
return (n);
}
SEG *
seg_inter(SEG *a, SEG *b)
{
SEG *n;
n = (SEG *) palloc(sizeof(*n));
/* take min of upper endpoints */
if (a->upper < b->upper)
{
n->upper = a->upper;
n->u_sigd = a->u_sigd;
n->u_ext = a->u_ext;
}
else
{
n->upper = b->upper;
n->u_sigd = b->u_sigd;
n->u_ext = b->u_ext;
}
/* take max of lower endpoints */
if (a->lower > b->lower)
{
n->lower = a->lower;
n->l_sigd = a->l_sigd;
n->l_ext = a->l_ext;
}
else
{
n->lower = b->lower;
n->l_sigd = b->l_sigd;
n->l_ext = b->l_ext;
}
return (n);
}
void
rt_seg_size(SEG *a, float *size)
{
if (a == (SEG *) NULL || a->upper <= a->lower)
*size = 0.0;
else
*size = (float) abs(a->upper - a->lower);
return;
}
float *
seg_size(SEG *a)
{
float *result;
result = (float *) palloc(sizeof(float));
*result = (float) abs(a->upper - a->lower);
return(result);
}
/*****************************************************************************
* Miscellaneous operators
*****************************************************************************/
int32
seg_cmp(SEG *a, SEG *b)
{
/*
* First compare on lower boundary position
*/
if ( a->lower < b->lower )
return -1;
if ( a->lower > b->lower )
return 1;
/*
* a->lower == b->lower, so consider type of boundary.
*
* A '-' lower bound is < any other kind (this could only be relevant
* if -HUGE is used as a regular data value).
* A '<' lower bound is < any other kind except '-'.
* A '>' lower bound is > any other kind.
*/
if ( a->l_ext != b->l_ext )
{
if ( a->l_ext == '-')
return -1;
if ( b->l_ext == '-')
return 1;
if ( a->l_ext == '<')
return -1;
if ( b->l_ext == '<')
return 1;
if ( a->l_ext == '>')
return 1;
if ( b->l_ext == '>')
return -1;
}
/*
* For other boundary types, consider # of significant digits first.
*/
if ( a->l_sigd < b->l_sigd ) /* (a) is blurred and is likely to include (b) */
return -1;
if ( a->l_sigd > b->l_sigd ) /* (a) is less blurred and is likely to be included in (b) */
return 1;
/*
* For same # of digits, an approximate boundary is more blurred than
* exact.
*/
if ( a->l_ext != b->l_ext )
{
if ( a->l_ext == '~' ) /* (a) is approximate, while (b) is exact */
return -1;
if ( b->l_ext == '~' )
return 1;
/* can't get here unless data is corrupt */
elog(ERROR, "seg_cmp: bogus lower boundary types %d %d",
(int) a->l_ext, (int) b->l_ext);
}
/* at this point, the lower boundaries are identical */
/*
* First compare on upper boundary position
*/
if ( a->upper < b->upper )
return -1;
if ( a->upper > b->upper )
return 1;
/*
* a->upper == b->upper, so consider type of boundary.
*
* A '-' upper bound is > any other kind (this could only be relevant
* if HUGE is used as a regular data value).
* A '<' upper bound is < any other kind.
* A '>' upper bound is > any other kind except '-'.
*/
if ( a->u_ext != b->u_ext )
{
if ( a->u_ext == '-')
return 1;
if ( b->u_ext == '-')
return -1;
if ( a->u_ext == '<')
return -1;
if ( b->u_ext == '<')
return 1;
if ( a->u_ext == '>')
return 1;
if ( b->u_ext == '>')
return -1;
}
/*
* For other boundary types, consider # of significant digits first.
* Note result here is converse of the lower-boundary case.
*/
if ( a->u_sigd < b->u_sigd ) /* (a) is blurred and is likely to include (b) */
return 1;
if ( a->u_sigd > b->u_sigd ) /* (a) is less blurred and is likely to be included in (b) */
return -1;
/*
* For same # of digits, an approximate boundary is more blurred than
* exact. Again, result is converse of lower-boundary case.
*/
if ( a->u_ext != b->u_ext )
{
if ( a->u_ext == '~' ) /* (a) is approximate, while (b) is exact */
return 1;
if ( b->u_ext == '~' )
return -1;
/* can't get here unless data is corrupt */
elog(ERROR, "seg_cmp: bogus upper boundary types %d %d",
(int) a->u_ext, (int) b->u_ext);
}
return 0;
}
bool
seg_lt(SEG *a, SEG *b)
{
return seg_cmp(a, b) < 0;
}
bool
seg_le(SEG *a, SEG *b)
{
return seg_cmp(a, b) <= 0;
}
bool
seg_gt(SEG *a, SEG *b)
{
return seg_cmp(a, b) > 0;
}
bool
seg_ge(SEG *a, SEG *b)
{
return seg_cmp(a, b) >= 0;
}
bool
seg_different(SEG *a, SEG *b)
{
return seg_cmp(a, b) != 0;
}
/*****************************************************************************
* Auxiliary functions
*****************************************************************************/
/* The purpose of this routine is to print the floating point
* value with exact number of significant digits. Its behaviour
* is similar to %.ng except it prints 8.00 where %.ng would
* print 8
*/
static int restore ( char * result, float val, int n )
{
static char efmt[8] = {'%', '-', '1', '5', '.', '#', 'e', 0};
char buf[25] = {
'0', '0', '0', '0', '0',
'0', '0', '0', '0', '0',
'0', '0', '0', '0', '0',
'0', '0', '0', '0', '0',
'0', '0', '0', '0', '\0'
};
char *p;
char *mant;
int exp;
int i, dp, sign;
/* put a cap on the number of siugnificant digits to avoid
nonsense in the output */
n = min(n, FLT_DIG);
/* remember the sign */
sign = ( val < 0 ? 1 : 0 );
efmt[5] = '0' + (n-1)%10; /* makes %-15.(n-1)e -- this format guarantees that
the exponent is always present */
sprintf(result, efmt, val);
/* trim the spaces left by the %e */
for( p = result; *p != ' '; p++ ); *p = '\0';
/* get the exponent */
mant = (char *)strtok( strdup(result), "e" );
exp = atoi(strtok( NULL, "e" ));
if ( exp == 0 ) {
/* use the supplied mantyssa with sign */
strcpy((char *)index(result, 'e'), "");
}
else {
if ( abs( exp ) <= 4 ) {
/* remove the decimal point from the mantyssa and write the digits to the buf array */
for( p = result + sign, i = 10, dp = 0; *p != 'e'; p++, i++ ) {
buf[i] = *p;
if( *p == '.' ) {
dp = i--; /* skip the decimal point */
}
}
if (dp == 0) dp = i--; /* no decimal point was found in the above for() loop */
if ( exp > 0 ) {
if ( dp - 10 + exp >= n ) {
/*
the decimal point is behind the last significant digit;
the digits in between must be converted to the exponent
and the decimal point placed after the first digit
*/
exp = dp - 10 + exp - n;
buf[10+n] = '\0';
/* insert the decimal point */
if ( n > 1 ) {
dp = 11;
for ( i = 23; i > dp; i-- ) {
buf[i] = buf[i-1];
}
buf[dp] = '.';
}
/* adjust the exponent by the number of digits after the decimal point */
if ( n > 1 ) {
sprintf(&buf[11+n], "e%d", exp + n - 1);
}
else {
sprintf(&buf[11], "e%d", exp + n - 1);
}
if ( sign ) {
buf[9] = '-';
strcpy(result, &buf[9]);
}
else {
strcpy(result, &buf[10]);
}
}
else { /* insert the decimal point */
dp += exp;
for ( i = 23; i > dp; i-- ) {
buf[i] = buf[i-1];
}
buf[11+n] = '\0';
buf[dp] = '.';
if ( sign ) {
buf[9] = '-';
strcpy(result, &buf[9]);
}
else {
strcpy(result, &buf[10]);
}
}
}
else { /* exp <= 0 */
dp += exp - 1;
buf[10+n] = '\0';
buf[dp] = '.';
if ( sign ) {
buf[dp-2] = '-';
strcpy(result, &buf[dp-2]);
}
else {
strcpy(result, &buf[dp-1]);
}
}
}
/* do nothing for abs(exp) > 4; %e must be OK */
/* just get rid of zeroes after [eE]- and +zeroes after [Ee]. */
/* ... this is not done yet. */
}
return ( strlen ( result ) );
}
/*
** Miscellany
*/
bool
seg_contains_int(SEG *a, int *b)
{
return ( (a->lower <= *b) && (a->upper >= *b) );
}
bool
seg_contains_float4(SEG *a, float4 *b)
{
return ( (a->lower <= *b) && (a->upper >= *b) );
}
bool
seg_contains_float8(SEG *a, float8 *b)
{
return ( (a->lower <= *b) && (a->upper >= *b) );
}
/* find out the number of significant digits in a string representing
* a floating point number
*/
int significant_digits ( char* s )
{
char * p = s;
int n, c, zeroes;
zeroes = 1;
/* skip leading zeroes and sign */
for ( c = *p; (c == '0' || c == '+' || c == '-') && c != 0; c = *(++p) );
/* skip decimal point and following zeroes */
for ( c = *p; (c == '0' || c == '.' ) && c != 0; c = *(++p) ) {
if ( c != '.') zeroes++;
}
/* count significant digits (n) */
for ( c = *p, n = 0; c != 0; c = *(++p) ) {
if ( !( (c >= '0' && c <= '9') || (c == '.') ) ) break;
if ( c != '.') n++;
}
if (!n) return ( zeroes );
return( n );
}
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