/**
* Writes a unsigned varInt to the buffer
*/
void
bytebuffer_append_uvarint(bytebuffer_t *b, const uint64_t val)
{
size_t size;
bytebuffer_makeroom(b, 8);
size = varint_u64_encode_buf(val, b->writecursor);
b->writecursor += size;
return;
}
/**
* Stores a pointarray as varints in the buffer
* @register_npoints, controls whether an npoints entry is added to the buffer (used to skip npoints for point types)
* @dimension, states the dimensionality of object this array is part of (0 = point, 1 = linear, 2 = areal)
*/
static int ptarray_to_twkb_buf(const POINTARRAY *pa, TWKB_GLOBALS *globals, TWKB_STATE *ts, int register_npoints, int minpoints)
{
int ndims = FLAGS_NDIMS(pa->flags);
int i, j;
bytebuffer_t b;
bytebuffer_t *b_p;
int64_t nextdelta[MAX_N_DIMS];
int npoints = 0;
size_t npoints_offset = 0;
LWDEBUGF(2, "Entered %s", __func__);
/* Dispense with the empty case right away */
if ( pa->npoints == 0 && register_npoints )
{
LWDEBUGF(4, "Register npoints:%d", pa->npoints);
bytebuffer_append_uvarint(ts->geom_buf, pa->npoints);
return 0;
}
/* If npoints is more than 127 it is unpredictable how many bytes npoints will need */
/* Then we have to store the deltas in a temp buffer to later add them after npoints */
/* If noints is below 128 we know 1 byte will be needed */
/* Then we can make room for that 1 byte at once and write to */
/* ordinary buffer */
if( pa->npoints > 127 )
{
/* Independent buffer to hold the coordinates, so we can put the npoints */
/* into the stream once we know how many points we actually have */
bytebuffer_init_with_size(&b, 3 * ndims * pa->npoints);
b_p = &b;
}
else
{
/* We give an alias to our ordinary buffer */
b_p = ts->geom_buf;
if ( register_npoints )
{
/* We do not store a pointer to the place where we want the npoints value */
/* Instead we store how far from the beginning of the buffer we want the value */
/* That is because we otherwise will get in trouble if the buffer is reallocated */
npoints_offset = b_p->writecursor - b_p->buf_start;
/* We just move the cursor 1 step to make room for npoints byte */
/* We use the function append_byte even if we have no value yet, */
/* since that gives us the check for big enough buffer and moves the cursor */
bytebuffer_append_byte(b_p, 0);
}
}
for ( i = 0; i < pa->npoints; i++ )
{
double *dbl_ptr = (double*)getPoint_internal(pa, i);
int diff = 0;
/* Write this coordinate to the buffer as a varint */
for ( j = 0; j < ndims; j++ )
{
/* To get the relative coordinate we don't get the distance */
/* from the last point but instead the distance from our */
/* last accumulated point. This is important to not build up an */
/* accumulated error when rounding the coordinates */
nextdelta[j] = (int64_t) llround(globals->factor[j] * dbl_ptr[j]) - ts->accum_rels[j];
LWDEBUGF(4, "deltavalue: %d, ", nextdelta[j]);
diff += llabs(nextdelta[j]);
}
/* Skipping the first point is not allowed */
/* If the sum(abs()) of all the deltas was zero, */
/* then this was a duplicate point, so we can ignore it */
if ( i > minpoints && diff == 0 )
continue;
/* We really added a point, so... */
npoints++;
/* Write this vertex to the temporary buffer as varints */
for ( j = 0; j < ndims; j++ )
{
ts->accum_rels[j] += nextdelta[j];
bytebuffer_append_varint(b_p, nextdelta[j]);
}
/* See if this coordinate expands the bounding box */
if( globals->variant & TWKB_BBOX )
{
for ( j = 0; j < ndims; j++ )
{
if( ts->accum_rels[j] > ts->bbox_max[j] )
ts->bbox_max[j] = ts->accum_rels[j];
if( ts->accum_rels[j] < ts->bbox_min[j] )
ts->bbox_min[j] = ts->accum_rels[j];
}
}
}
if ( pa->npoints > 127 )
{
/* Now write the temporary results into the main buffer */
/* First the npoints */
if ( register_npoints )
bytebuffer_append_uvarint(ts->geom_buf, npoints);
/* Now the coordinates */
bytebuffer_append_bytebuffer(ts->geom_buf, b_p);
/* Clear our temporary buffer */
lwfree(b.buf_start);
}
else
{
/* If we didn't use a temp buffer, we just write that npoints value */
/* to where it belongs*/
if ( register_npoints )
varint_u64_encode_buf(npoints, b_p->buf_start + npoints_offset);
}
return 0;
}
