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/**
* \file lib/segment/setup.c
*
* \brief Segment setup routines.
*
* This program is free software under the GNU General Public License
* (>=v2). Read the file COPYING that comes with GRASS for details.
*
* \author GRASS GIS Development Team
*
* \date 2005-2009
*/
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <grass/gis.h>
#include "local_proto.h"
/**
* \brief Internal use only
*
* Setup segment.
*
* <b>SEG</b> must have the following parms set:
* fd (open for read and write), nrows, ncols, srows, scols, len, nseg
*
* \param[in,out] SEG segment
* \return 1 if successful
* \return -1 if illegal parameters are passed in <b>SEG</b>
* \return -2 if unable to allocate memory
*/
int seg_setup(SEGMENT *SEG)
{
int i;
int seg_exp, n_total_segs;
SEG->open = 0;
SEG->cache = NULL;
if (SEG->nrows <= 0 || SEG->ncols <= 0 || SEG->srows <= 0 ||
SEG->scols <= 0 || SEG->len <= 0 || SEG->nseg <= 0) {
G_warning("Segment setup: illegal segment file parameters");
return -1;
}
/* This is close to the beginning of the file, so doesn't need to be an
* off_t */
SEG->offset = (int)lseek(SEG->fd, 0L, SEEK_CUR);
SEG->spr = SEG->ncols / SEG->scols;
SEG->spill = SEG->ncols % SEG->scols;
if (SEG->spill)
SEG->spr++;
/* fast address */
SEG->fast_adrs = 0;
seg_exp = 0;
while (SEG->scols - (1 << seg_exp) > 0)
seg_exp++;
if (SEG->scols - (1 << seg_exp) == 0) {
SEG->scolbits = seg_exp;
seg_exp = 0;
while (SEG->srows - (1 << seg_exp) > 0)
seg_exp++;
if (SEG->srows - (1 << seg_exp) == 0) {
SEG->srowbits = seg_exp;
SEG->segbits = SEG->srowbits + SEG->scolbits;
SEG->fast_adrs = 1;
G_debug(1, "Segment setup: fast address activated");
}
}
if (SEG->fast_adrs)
SEG->address = seg_address_fast;
else
SEG->address = seg_address_slow;
/* fast seek */
SEG->fast_seek = 0;
if (SEG->fast_adrs == 1) {
seg_exp = 0;
while (SEG->len - (1 << seg_exp) > 0)
seg_exp++;
if (SEG->len - (1 << seg_exp) == 0) {
SEG->lenbits = seg_exp;
SEG->sizebits = SEG->segbits + SEG->lenbits;
SEG->fast_seek = 1;
G_debug(1, "Segment setup: fast seek activated");
}
}
if (SEG->fast_seek)
SEG->seek = seg_seek_fast;
else
SEG->seek = seg_seek_slow;
/* adjust number of open segments if larger than number of total segments */
n_total_segs = SEG->spr * ((SEG->nrows + SEG->srows - 1) / SEG->srows);
if (SEG->nseg > n_total_segs) {
G_debug(1,
"Segment setup: reducing number of open segments from %d to %d",
SEG->nseg, n_total_segs);
SEG->nseg = n_total_segs;
}
if ((SEG->scb = (struct scb *)G_malloc(SEG->nseg * sizeof(struct scb))) ==
NULL)
return -2;
if ((SEG->freeslot = (int *)G_malloc(SEG->nseg * sizeof(int))) == NULL)
return -2;
if ((SEG->agequeue = (struct aq *)G_malloc((SEG->nseg + 1) *
sizeof(struct aq))) == NULL)
return -2;
SEG->srowscols = SEG->srows * SEG->scols;
SEG->size = SEG->srowscols * SEG->len;
for (i = 0; i < SEG->nseg; i++) {
if ((SEG->scb[i].buf = G_malloc(SEG->size)) == NULL)
return -2;
SEG->scb[i].n = -1; /* mark free */
SEG->scb[i].dirty = 0;
SEG->scb[i].age = NULL;
SEG->freeslot[i] = i;
SEG->agequeue[i].cur = -1;
if (i > 0) {
SEG->agequeue[i].younger = &(SEG->agequeue[i - 1]);
SEG->agequeue[i].older = &(SEG->agequeue[i + 1]);
}
else if (i == 0) {
SEG->agequeue[i].younger = &(SEG->agequeue[SEG->nseg]);
SEG->agequeue[i].older = &(SEG->agequeue[i + 1]);
}
}
SEG->agequeue[SEG->nseg].cur = -1;
SEG->agequeue[SEG->nseg].younger = &(SEG->agequeue[SEG->nseg - 1]);
SEG->agequeue[SEG->nseg].older = &(SEG->agequeue[0]);
SEG->youngest = SEG->oldest = &(SEG->agequeue[SEG->nseg]);
SEG->nfreeslots = SEG->nseg;
SEG->cur = 0;
SEG->open = 1;
/* index for each segment, same like cache of r.proj */
/* alternative using less memory: RB Tree */
/* SEG->loaded = rbtree_create(cmp, sizeof(SEGID)); */
/* SEG->loaded = NULL; */
SEG->load_idx = G_malloc(n_total_segs * sizeof(int));
for (i = 0; i < n_total_segs; i++)
SEG->load_idx[i] = -1;
return 1;
}
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