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#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include "segment.h"
static int read_int(int,int *);
/* fd must be open for read and write */
/*!
* \brief initialize segment
* structure
*
* Initializes the <b>seg</b> structure. The file on <b>fd</b> is
* a segment file created by <i>segment_format</i> and must be open for
* reading and writing. The segment file configuration parameters <i>nrows,
* ncols, srows, scols</i>, and <i>len</i>, as written to the file by
* <i>segment_format</i>, are read from the file and stored in the
* <b>seg</b> structure. <b>Nsegs</b> specifies the number of segments that
* will be retained in memory. The minimum value allowed is 1.
* <b>Note.</b> The size of a segment is <i>scols*srows*len</i> plus a few
* bytes for managing each segment.
* Return codes are: 1 if ok; else -1 could not seek or read segment file, or -2 out of memory.
*
* \param seg
* \param fd
* \param nsegs
* \return int
*/
int segment_init (SEGMENT *SEG,int fd,int nseg)
{
SEG->open = 0;
SEG->fd = fd;
SEG->nseg = nseg;
if (lseek (fd, 0L, 0) < 0)
{
G_warning ("segment_init: %s\n",strerror(errno));
return -1;
}
/* read the header */
if (!read_int (fd, &SEG->nrows)
|| !read_int (fd, &SEG->ncols)
|| !read_int (fd, &SEG->srows)
|| !read_int (fd, &SEG->scols)
|| !read_int (fd, &SEG->len))
return -1;
return segment_setup (SEG);
}
static int read_int (int fd, int *n)
{
int bytes_read;
if((bytes_read = read (fd, n, sizeof(int))) == -1)
G_warning("read_int: %s\n",strerror(errno));
bytes_read = (bytes_read == sizeof(int));
return bytes_read;
}
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