segment.h

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#ifndef GRASS_SEGMENT_H
#define GRASS_SEGMENT_H

#include <grass/gis.h>

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif

struct aq {                     /* age queue */
    int cur;                    /* segment number */
    struct aq *younger, *older; /* pointer to next younger and next older */
} ;

typedef struct
{
    int open;                   /* open flag */
    off_t nrows;                /* rows in original data */
    off_t ncols;                /* cols in original data */
    int len;                    /* bytes per data value */
    int srows;                  /* rows in segments */
    int scols;                  /* cols in segments */
    int srowscols;              /* rows x cols in segments */
    int size;                   /* size in bytes of a segment */
    int spr;                    /* segments per row */
    int spill;                  /* cols in last segment in row */

    /* fast mode */
    int fast_adrs;              /* toggles fast address mode */
    off_t scolbits;             /* column bitshift */
    off_t srowbits;             /* row bitshift */
    off_t segbits;              /* segment bitshift */
    int fast_seek;              /* toggles fast seek mode */
    int lenbits;                /* data size bitshift */
    int sizebits;               /* segment size bitshift */
    int (*address)();
    int (*seek)();
    
    char *fname;                /* segment file name */
    int fd;                     /* file descriptor to read/write segment */
    struct scb                  /* control blocks */
    {
        char *buf;              /* data buffer */
        char dirty;             /* dirty flag */
        struct aq *age;         /* pointer to position in age queue */
        int n;                  /* segment number */
    } *scb;
    int *load_idx;              /* index of loaded segments */
    int nfreeslots;             /* number of free slots */
    int *freeslot;              /* array of free slots */
    struct aq *agequeue,        /* queue of age for order of access */ 
              *youngest,        /* youngest in age queue */
              *oldest;          /* oldest in age queue */
    int nseg;                   /* number of segments in memory */
    int cur;                    /* last accessed segment */
    int offset;                 /* offset of data past header */

    char *cache;                /* all in memory cache */
} SEGMENT;

#include <grass/defs/segment.h>

#endif /* GRASS_SEGMENT_H */