void WriterImpl::UpdateHeader(LASHeader const& header)
{
if (m_pointCount != header.GetPointRecordsCount())
{
// Skip to first byte of number of point records data member
std::streamsize const dataPos = 107;
m_ofs.seekp(dataPos, std::ios::beg);
detail::write_n(m_ofs, m_pointCount , sizeof(m_pointCount));
}
}
void WriterImpl::WriteHeader(LASHeader& header)
{
uint8_t n1 = 0;
uint16_t n2 = 0;
uint32_t n4 = 0;
// Rewrite the georeference VLR entries if they exist
header.SetGeoreference();
// Seek to the beginning
m_ofs.seekp(0, std::ios::beg);
std::ios::pos_type beginning = m_ofs.tellp();
// Seek to the end
m_ofs.seekp(0, std::ios::end);
std::ios::pos_type end = m_ofs.tellp();
// Figure out how many points we already have. Each point record
// should be 20 bytes long, and header.GetDataOffset tells
// us the location to start counting points from.
// This test should only be true if we were opened in both
// std::ios::in *and* std::ios::out, otherwise it should return false
// and we won't adjust the point count.
if ((beginning != end) && ((uint32_t)end != 0)) {
m_pointCount = ((uint32_t) end - header.GetDataOffset())/header.GetDataRecordLength();
// Position to the beginning of the file to start writing the header
m_ofs.seekp(0, std::ios::beg);
}
// 1. File Signature
std::string const filesig(header.GetFileSignature());
assert(filesig.size() == 4);
detail::write_n(m_ofs, filesig, 4);
// 2. Reserved
n4 = header.GetReserved();
detail::write_n(m_ofs, n4, sizeof(n4));
// 3-6. GUID data
uint32_t d1 = 0;
uint16_t d2 = 0;
uint16_t d3 = 0;
uint8_t d4[8] = { 0 };
liblas::guid g = header.GetProjectId();
g.output_data(d1, d2, d3, d4);
detail::write_n(m_ofs, d1, sizeof(d1));
detail::write_n(m_ofs, d2, sizeof(d2));
detail::write_n(m_ofs, d3, sizeof(d3));
detail::write_n(m_ofs, d4, sizeof(d4));
// 7. Version major
n1 = header.GetVersionMajor();
assert(1 == n1);
detail::write_n(m_ofs, n1, sizeof(n1));
// 8. Version minor
n1 = header.GetVersionMinor();
assert(0 == n1);
detail::write_n(m_ofs, n1, sizeof(n1));
// 9. System ID
std::string sysid(header.GetSystemId(true));
assert(sysid.size() == 32);
detail::write_n(m_ofs, sysid, 32);
// 10. Generating Software ID
std::string softid(header.GetSoftwareId(true));
assert(softid.size() == 32);
detail::write_n(m_ofs, softid, 32);
// 11. Flight Date Julian
n2 = header.GetCreationDOY();
detail::write_n(m_ofs, n2, sizeof(n2));
// 12. Year
n2 = header.GetCreationYear();
detail::write_n(m_ofs, n2, sizeof(n2));
// 13. Header Size
n2 = header.GetHeaderSize();
assert(227 <= n2);
detail::write_n(m_ofs, n2, sizeof(n2));
// 14. Offset to data
n4 = header.GetDataOffset();
detail::write_n(m_ofs, n4, sizeof(n4));
// 15. Number of variable length records
// TODO: This value must be updated after new variable length record is added.
n4 = header.GetRecordsCount();
detail::write_n(m_ofs, n4, sizeof(n4));
// 16. Point Data Format ID
n1 = static_cast<uint8_t>(header.GetDataFormatId());
detail::write_n(m_ofs, n1, sizeof(n1));
// 17. Point Data Record Length
n2 = header.GetDataRecordLength();
detail::write_n(m_ofs, n2, sizeof(n2));
// 18. Number of point records
// This value is updated if necessary, see UpdateHeader function.
n4 = header.GetPointRecordsCount();
detail::write_n(m_ofs, n4, sizeof(n4));
// 19. Number of points by return
std::vector<uint32_t>::size_type const srbyr = 5;
std::vector<uint32_t> const& vpbr = header.GetPointRecordsByReturnCount();
assert(vpbr.size() <= srbyr);
uint32_t pbr[srbyr] = { 0 };
std::copy(vpbr.begin(), vpbr.end(), pbr);
detail::write_n(m_ofs, pbr, sizeof(pbr));
// 20-22. Scale factors
detail::write_n(m_ofs, header.GetScaleX(), sizeof(double));
detail::write_n(m_ofs, header.GetScaleY(), sizeof(double));
detail::write_n(m_ofs, header.GetScaleZ(), sizeof(double));
// 23-25. Offsets
detail::write_n(m_ofs, header.GetOffsetX(), sizeof(double));
detail::write_n(m_ofs, header.GetOffsetY(), sizeof(double));
detail::write_n(m_ofs, header.GetOffsetZ(), sizeof(double));
// 26-27. Max/Min X
detail::write_n(m_ofs, header.GetMaxX(), sizeof(double));
detail::write_n(m_ofs, header.GetMinX(), sizeof(double));
// 28-29. Max/Min Y
detail::write_n(m_ofs, header.GetMaxY(), sizeof(double));
detail::write_n(m_ofs, header.GetMinY(), sizeof(double));
// 30-31. Max/Min Z
detail::write_n(m_ofs, header.GetMaxZ(), sizeof(double));
detail::write_n(m_ofs, header.GetMinZ(), sizeof(double));
WriteVLR(header);
uint8_t const sgn1 = 0xCC;
uint8_t const sgn2 = 0xDD;
detail::write_n(m_ofs, sgn1, sizeof(uint8_t));
detail::write_n(m_ofs, sgn2, sizeof(uint8_t));
// If we already have points, we're going to put it at the end of the file.
// If we don't have any points, we're going to leave it where it is.
if (m_pointCount != 0)
m_ofs.seekp(0, std::ios::end);
}