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https://git.osgeo.org/gitea/postgis/postgis
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6b1245d125
git-svn-id: http://svn.osgeo.org/postgis/trunk@10707 b70326c6-7e19-0410-871a-916f4a2858ee
102 lines
3.3 KiB
C
102 lines
3.3 KiB
C
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/**********************************************************************
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** GIDX structure.
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**
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** This is an n-dimensional (practically, the
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** implementation is 2-4 dimensions) box used for index keys. The
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** coordinates are anonymous, so we can have any number of dimensions.
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** The sizeof a GIDX is 1 + 2 * ndims * sizeof(float).
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** The order of values in a GIDX is
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** xmin,xmax,ymin,ymax,zmin,zmax...
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*/
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typedef struct
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{
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int32 varsize;
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float c[1];
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} GIDX;
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/*
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** For some GiST support functions, it is more efficient to allocate
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** memory for our GIDX off the stack and cast that memory into a GIDX.
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** But, GIDX is variable length, what to do? We'll bake in the assumption
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** that no GIDX is more than 4-dimensional for now, and ensure that much
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** space is available.
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** 4 bytes varsize + 4 dimensions * 2 ordinates * 4 bytes float size = 36 bytes
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*/
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#define GIDX_MAX_SIZE 36
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/**********************************************************************
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** BOX2DF structure.
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**
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** This is a 2-dimensional key for simple cartesian indexes,
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** with backwards compatible behavior to previous indexes in
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** PostGIS
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*/
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typedef struct
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{
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float xmin, xmax, ymin, ymax;
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} BOX2DF;
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/*********************************************************************************
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** GIDX support functions.
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**
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** We put the GIDX support here rather than libgeom because it is a specialized
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** type only used for indexing purposes. It also makes use of some PgSQL
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** infrastructure like the VARSIZE() macros.
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*/
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/* allocate a new gidx object on the heap */
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GIDX* gidx_new(int ndims) ;
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/* Convert a gidx to a gbox */
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void gbox_from_gidx(GIDX *gidx, GBOX *gbox);
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/* Convert a gbox to a new gidx */
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GIDX* gidx_from_gbox(GBOX box);
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/* Increase the size of a GIDX */
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void gidx_expand(GIDX *a, float d);
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/* Generate human readable form for GIDX. */
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#if POSTGIS_DEBUG_LEVEL > 0
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char* gidx_to_string(GIDX *a) ;
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#endif
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/* Returns number of dimensions for this GIDX */
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#define GIDX_NDIMS(gidx) ((VARSIZE((gidx)) - VARHDRSZ) / (2 * sizeof(float)))
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/* Minimum accessor. */
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#define GIDX_GET_MIN(gidx, dimension) ((gidx)->c[2*(dimension)])
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/* Maximum accessor. */
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#define GIDX_GET_MAX(gidx, dimension) ((gidx)->c[2*(dimension)+1])
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/* Minimum setter. */
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#define GIDX_SET_MIN(gidx, dimension, value) ((gidx)->c[2*(dimension)] = (value))
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/* Maximum setter. */
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#define GIDX_SET_MAX(gidx, dimension, value) ((gidx)->c[2*(dimension)+1] = (value))
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/* Returns the size required to store a GIDX of requested dimension */
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#define GIDX_SIZE(dimensions) (sizeof(int32) + 2*(dimensions)*sizeof(float))
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/*********************************************************************************
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** GSERIALIZED support functions.
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**
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** Fast functions for pulling boxes out of serializations.
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*/
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/* Pull out the #GIDX bounding box with a absolute minimum system overhead */
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int gserialized_datum_get_gidx_p(Datum gserialized_datum, GIDX *gidx);
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/* Pull out the gidx bounding box from an already de-toasted geography */
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int gserialized_get_gidx_p(GSERIALIZED *g, GIDX *gidx);
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/* Copy a new bounding box into an existing gserialized */
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GSERIALIZED* gserialized_set_gidx(GSERIALIZED *g, GIDX *gidx);
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/* Given two datums, do they overlap? Computed very fast using embedded boxes. */
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/* int gserialized_datum_overlaps(Datum gs1, Datum gs2); */
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/* Remove the box from a disk serialization */
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GSERIALIZED* gserialized_drop_gidx(GSERIALIZED *g);
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