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#include <mbgl/geometry/line_buffer.hpp>
#include <cmath>
namespace mbgl {
size_t LineVertexBuffer::add(vertex_type x, vertex_type y, float ex, float ey, bool tx, bool ty, int8_t dir, int32_t linesofar) {
size_t idx = index();
void *data = addElement();
int16_t *coords = static_cast<int16_t *>(data);
coords[0] = (x * 2) | tx;
coords[1] = (y * 2) | ty;
uint8_t *ubytes = static_cast<uint8_t *>(data);
// add 128 to store an byte in an unsigned byte
ubytes[4] = ::round(extrudeScale * ex) + 128;
ubytes[5] = ::round(extrudeScale * ey) + 128;
// Encode the -1/0/1 direction value into the first two bits of .z of a_data.
// Combine it with the lower 6 bits of `linesofar` (shifted by 2 bites to make
// room for the direction value). The upper 8 bits of `linesofar` are placed in
// the `w` component. `linesofar` is scaled down by `LINE_DISTANCE_SCALE` so that
// we can store longer distances while sacrificing precision.
// Encode the -1/0/1 direction value into .zw coordinates of a_data, which is normally covered
// by linesofar, so we need to merge them.
// The z component's first bit, as well as the sign bit is reserved for the direction,
// so we need to shift the linesofar.
ubytes[6] = ((dir == 0 ? 0 : (dir < 0 ? -1 : 1 )) + 1) | ((linesofar & 0x3F) << 2);
ubytes[7] = linesofar >> 6;
return idx;
}
} // namespace mbgl
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