GRASS GIS 8 Programmer's Manual 8.3.2(2024)-exported
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segment/get.c
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1/**
2 * \file lib/segment/get.c
3 *
4 * \brief Get segment routines.
5 *
6 * This program is free software under the GNU General Public License
7 * (>=v2). Read the file COPYING that comes with GRASS for details.
8 *
9 * \author GRASS GIS Development Team
10 *
11 * \date 2005-2018
12 */
13
14#include <string.h>
15#include "local_proto.h"
16
17/*bugfix: buf: char* vs int* -> wrong pointer arithmetics!!!. Pierre de Mouveaux
18 * - 09 april 2000 */
19/* int Segment_get (SEGMENT *SEG, register int *buf,int row,int col) */
20
21/**
22 * \brief Get value from segment file.
23 *
24 * Provides random read access to the segmented data. It gets
25 * <i>len</i> bytes of data into <b>buf</b> from the segment file
26 * <b>seg</b> for the corresponding <b>row</b> and <b>col</b> in the
27 * original data matrix.
28 *
29 * \param[in] SEG segment
30 * \param[in,out] buf value return buffer
31 * \param[in] row
32 * \param[in] col
33 * \return 1 of successful
34 * \return -1 if unable to seek or read segment file
35 */
36
37int Segment_get(SEGMENT *SEG, void *buf, off_t row, off_t col)
38{
39 int index, n, i;
40
41 if (SEG->cache) {
42 memcpy(buf, SEG->cache + ((size_t)row * SEG->ncols + col) * SEG->len,
43 SEG->len);
44
45 return 1;
46 }
47
48 SEG->address(SEG, row, col, &n, &index);
49 if ((i = seg_pagein(SEG, n)) < 0)
50 return -1;
51
52 memcpy(buf, &SEG->scb[i].buf[index], SEG->len);
53
54 return 1;
55}
int seg_pagein(SEGMENT *SEG, int n)
Internal use only.
Definition pagein.c:35
int Segment_get(SEGMENT *SEG, void *buf, off_t row, off_t col)
Get value from segment file.
Definition segment/get.c:37