bool ReaderImpl::ReadHeader(LASHeader& header)
{
using detail::read_n;
// Helper variables
uint8_t n1 = 0;
uint16_t n2 = 0;
uint32_t n4 = 0;
double x1 = 0;
double y1 = 0;
double z1 = 0;
double x2 = 0;
double y2 = 0;
double z2 = 0;
std::string buf;
std::string fsig;
m_ifs.seekg(0);
// 1. File Signature
read_n(fsig, m_ifs, 4);
header.SetFileSignature(fsig);
// 2. Reserved
// This data must always contain Zeros.
read_n(n4, m_ifs, sizeof(n4));
// 3-6. GUID data
uint32_t d1 = 0;
uint16_t d2 = 0;
uint16_t d3 = 0;
uint8_t d4[8] = { 0 };
read_n(d1, m_ifs, sizeof(d1));
read_n(d2, m_ifs, sizeof(d2));
read_n(d3, m_ifs, sizeof(d3));
read_n(d4, m_ifs, sizeof(d4));
liblas::guid g(d1, d2, d3, d4);
header.SetProjectId(g);
// 7. Version major
read_n(n1, m_ifs, sizeof(n1));
header.SetVersionMajor(n1);
// 8. Version minor
read_n(n1, m_ifs, sizeof(n1));
header.SetVersionMinor(n1);
// 9. System ID
read_n(buf, m_ifs, 32);
header.SetSystemId(buf);
// 10. Generating Software ID
read_n(buf, m_ifs, 32);
header.SetSoftwareId(buf);
// 11. Flight Date Julian
read_n(n2, m_ifs, sizeof(n2));
header.SetCreationDOY(n2);
// 12. Year
read_n(n2, m_ifs, sizeof(n2));
header.SetCreationYear(n2);
// 13. Header Size
// NOTE: Size of the stanard header block must always be 227 bytes
read_n(n2, m_ifs, sizeof(n2));
// 14. Offset to data
read_n(n4, m_ifs, sizeof(n4));
if (n4 < header.GetHeaderSize())
{
// TODO: Move this test to LASHeader::Validate()
throw std::domain_error("offset to point data smaller than header size");
}
header.SetDataOffset(n4);
// 15. Number of variable length records
read_n(n4, m_ifs, sizeof(n4));
header.SetRecordsCount(n4);
// 16. Point Data Format ID
read_n(n1, m_ifs, sizeof(n1));
if (n1 == LASHeader::ePointFormat0) {
header.SetDataFormatId(LASHeader::ePointFormat0);
}
else if (n1 == LASHeader::ePointFormat1) {
header.SetDataFormatId(LASHeader::ePointFormat1);
}
else if (n1 == LASHeader::ePointFormat2) {
header.SetDataFormatId(LASHeader::ePointFormat2);
}
else if (n1 == LASHeader::ePointFormat3) {
header.SetDataFormatId(LASHeader::ePointFormat3);
}
else {
throw std::domain_error("invalid point data format");
}
// 17. Point Data Record Length
// NOTE: No need to set record length because it's
// determined on basis of point data format.
read_n(n2, m_ifs, sizeof(n2));
// 18. Number of point records
read_n(n4, m_ifs, sizeof(n4));
header.SetPointRecordsCount(n4);
// 19. Number of points by return
std::vector<uint32_t>::size_type const srbyr = 5;
uint32_t rbyr[srbyr] = { 0 };
read_n(rbyr, m_ifs, sizeof(rbyr));
for (std::size_t i = 0; i < srbyr; ++i)
{
header.SetPointRecordsByReturnCount(i, rbyr[i]);
}
// 20-22. Scale factors
read_n(x1, m_ifs, sizeof(x1));
read_n(y1, m_ifs, sizeof(y1));
read_n(z1, m_ifs, sizeof(z1));
header.SetScale(x1, y1, z1);
// 23-25. Offsets
read_n(x1, m_ifs, sizeof(x1));
read_n(y1, m_ifs, sizeof(y1));
read_n(z1, m_ifs, sizeof(z1));
header.SetOffset(x1, y1, z1);
// 26-27. Max/Min X
read_n(x1, m_ifs, sizeof(x1));
read_n(x2, m_ifs, sizeof(x2));
// 28-29. Max/Min Y
read_n(y1, m_ifs, sizeof(y1));
read_n(y2, m_ifs, sizeof(y2));
// 30-31. Max/Min Z
read_n(z1, m_ifs, sizeof(z1));
read_n(z2, m_ifs, sizeof(z2));
header.SetMax(x1, y1, z1);
header.SetMin(x2, y2, z2);
Reset(header);
return true;
}
