PostGIS  2.3.8dev-r@@SVN_REVISION@@

◆ lwmline_measured_from_lwmline()

LWMLINE* lwmline_measured_from_lwmline ( const LWMLINE lwmline,
double  m_start,
double  m_end 
)

Re-write the measure ordinate (or add one, if it isn't already there) interpolating the measure between the supplied start and end values.

Definition at line 56 of file lwmline.c.

References LWMLINE::flags, FLAGS_GET_Z, LWMLINE::geoms, if(), lwalloc(), lwcollection_construct(), lwcollection_construct_empty(), lwerror(), lwgeom_is_empty(), lwline_measured_from_lwline(), MULTILINETYPE, LWMLINE::ngeoms, POINTARRAY::npoints, LWLINE::points, ptarray_length_2d(), LWGEOM::srid, LWGEOM::type, and LWMLINE::type.

Referenced by ST_AddMeasure().

57 {
58  int i = 0;
59  int hasm = 0, hasz = 0;
60  double length = 0.0, length_so_far = 0.0;
61  double m_range = m_end - m_start;
62  LWGEOM **geoms = NULL;
63 
64  if ( lwmline->type != MULTILINETYPE )
65  {
66  lwerror("lwmline_measured_from_lmwline: only multiline types supported");
67  return NULL;
68  }
69 
70  hasz = FLAGS_GET_Z(lwmline->flags);
71  hasm = 1;
72 
73  /* Calculate the total length of the mline */
74  for ( i = 0; i < lwmline->ngeoms; i++ )
75  {
76  LWLINE *lwline = (LWLINE*)lwmline->geoms[i];
77  if ( lwline->points && lwline->points->npoints > 1 )
78  {
79  length += ptarray_length_2d(lwline->points);
80  }
81  }
82 
83  if ( lwgeom_is_empty((LWGEOM*)lwmline) )
84  {
85  return (LWMLINE*)lwcollection_construct_empty(MULTILINETYPE, lwmline->srid, hasz, hasm);
86  }
87 
88  geoms = lwalloc(sizeof(LWGEOM*) * lwmline->ngeoms);
89 
90  for ( i = 0; i < lwmline->ngeoms; i++ )
91  {
92  double sub_m_start, sub_m_end;
93  double sub_length = 0.0;
94  LWLINE *lwline = (LWLINE*)lwmline->geoms[i];
95 
96  if ( lwline->points && lwline->points->npoints > 1 )
97  {
98  sub_length = ptarray_length_2d(lwline->points);
99  }
100 
101  sub_m_start = (m_start + m_range * length_so_far / length);
102  sub_m_end = (m_start + m_range * (length_so_far + sub_length) / length);
103 
104  geoms[i] = (LWGEOM*)lwline_measured_from_lwline(lwline, sub_m_start, sub_m_end);
105 
106  length_so_far += sub_length;
107  }
108 
109  return (LWMLINE*)lwcollection_construct(lwmline->type, lwmline->srid, NULL, lwmline->ngeoms, geoms);
110 }
LWLINE * lwline_measured_from_lwline(const LWLINE *lwline, double m_start, double m_end)
Add a measure dimension to a line, interpolating linearly from the start to the end value...
Definition: lwline.c:396
uint8_t type
Definition: liblwgeom.h:476
LWCOLLECTION * lwcollection_construct(uint8_t type, int srid, GBOX *bbox, uint32_t ngeoms, LWGEOM **geoms)
Definition: lwcollection.c:43
int npoints
Definition: liblwgeom.h:370
double ptarray_length_2d(const POINTARRAY *pts)
Find the 2d length of the given POINTARRAY (even if it&#39;s 3d)
Definition: ptarray.c:1652
int32_t srid
Definition: liblwgeom.h:398
int ngeoms
Definition: liblwgeom.h:480
uint8_t flags
Definition: liblwgeom.h:477
#define FLAGS_GET_Z(flags)
Macros for manipulating the &#39;flags&#39; byte.
Definition: liblwgeom.h:139
LWLINE ** geoms
Definition: liblwgeom.h:482
uint8_t type
Definition: liblwgeom.h:395
void * lwalloc(size_t size)
Definition: lwutil.c:227
int lwgeom_is_empty(const LWGEOM *geom)
Return true or false depending on whether a geometry is an "empty" geometry (no vertices members) ...
Definition: lwgeom.c:1310
#define MULTILINETYPE
Definition: liblwgeom.h:88
LWCOLLECTION * lwcollection_construct_empty(uint8_t type, int srid, char hasz, char hasm)
Definition: lwcollection.c:94
void lwerror(const char *fmt,...)
Write a notice out to the error handler.
Definition: lwutil.c:102
if(!(yy_init))
POINTARRAY * points
Definition: liblwgeom.h:421
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