GRASS GIS 8 Programmer's Manual 8.2.1(2023)-exported
segment/get.c
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1
2/**
3 * \file lib/segment/get.c
4 *
5 * \brief Get segment routines.
6 *
7 * This program is free software under the GNU General Public License
8 * (>=v2). Read the file COPYING that comes with GRASS for details.
9 *
10 * \author GRASS GIS Development Team
11 *
12 * \date 2005-2018
13 */
14
15#include <string.h>
16#include "local_proto.h"
17
18
19/*bugfix: buf: char* vs int* -> wrong pointer arithmetics!!!. Pierre de Mouveaux - 09 april 2000 */
20/* int Segment_get (SEGMENT *SEG, register int *buf,int row,int col) */
21
22
23/**
24 * \brief Get value from segment file.
25 *
26 * Provides random read access to the segmented data. It gets
27 * <i>len</i> bytes of data into <b>buf</b> from the segment file
28 * <b>seg</b> for the corresponding <b>row</b> and <b>col</b> in the
29 * original data matrix.
30 *
31 * \param[in] SEG segment
32 * \param[in,out] buf value return buffer
33 * \param[in] row
34 * \param[in] col
35 * \return 1 of successful
36 * \return -1 if unable to seek or read segment file
37 */
38
39int Segment_get(SEGMENT * SEG, void *buf, off_t row, off_t col)
40{
41 int index, n, i;
42
43 if (SEG->cache) {
44 memcpy(buf, SEG->cache + ((size_t)row * SEG->ncols + col) * SEG->len, SEG->len);
45
46 return 1;
47 }
48
49 SEG->address(SEG, row, col, &n, &index);
50 if ((i = seg_pagein(SEG, n)) < 0)
51 return -1;
52
53 memcpy(buf, &SEG->scb[i].buf[index], SEG->len);
54
55 return 1;
56}
int seg_pagein(SEGMENT *SEG, int n)
Internal use only.
Definition: pagein.c:37
int Segment_get(SEGMENT *SEG, void *buf, off_t row, off_t col)
Get value from segment file.
Definition: segment/get.c:39