Read/write operations fail on big-endian architectures

[mloskot]

When we started to work on libLAS, we've decided to defer implementation of robust endiannes support for after 1.0 release.

From libLAS FAQ:

According to the LAS Format Standard, all data is stored in little-endian format. The implication is that on little-endian architectures multi-byte data of LAS file can be read (or write) directly and bytes reordering is not required. On big endian machines, however, bytes of multi-byte data must reordered between big-endian and little-endian format.

Thus, problems with reading/writing LAS files on big-endian machines are expected. This ticket dedicated for discussion on this subject and should serve as a reminder.

Here is result of make check execution on Power PC machine (Apple PowerBook? G4 running Mac OS X 10.4):

libLAS Test Suite:
==================
liblas::LASError: ...
liblas::LASFile: .[2=F]....[7=F][8=F]..
liblas::LASHeader: ...........
liblas::LASPoint: ...............
liblas::LASReader: .[2=F].end of file encountered
[4=F][5=X][6=X].
liblas::LASRecordHeader: ......
liblas::LASWriter: ....
liblas::guid: .......

---> group: liblas::LASFile, test: test<2>
     problem: assertion failed
     failed assertion: " expected '229' actual '3841982464'"

---> group: liblas::LASFile, test: test<7>
     problem: assertion failed
     failed assertion: " expected '229' actual '3841982464'"

---> group: liblas::LASFile, test: test<8>
     problem: assertion failed
     failed assertion: " expected '229' actual '3841982464'"

---> group: liblas::LASReader, test: test<2>
     problem: assertion failed
     failed assertion: " expected '229' actual '3841982464'"

---> group: liblas::LASReader, test: test<4>
     problem: assertion failed
     failed assertion: " expected (630262 - 630262) actual '0'"

---> group: liblas::LASReader, test: test<5>
     problem: unexpected exception
     exception typeid: St13runtime_error
     message: "detail::liblas::read_n input stream is not readable"

---> group: liblas::LASReader, test: test<6>
     problem: unexpected exception
     exception typeid: St13runtime_error
     message: "detail::liblas::read_n input stream is not readable"

tests summary: exceptions:2 failures:5 ok:56

The tests output confirms the need for fixes in near future.

[mloskot]

Fixed in trunk (r746, r748).

I've successfully run all unit tests on Intel Xeon (little-endian) and Power PC (big-endian). Hobu, I'd be thankful if you can run tests on your machines too and confirm it works.

[mloskot]

Added big endian byte swapping for members of VLRHeader type (r750)

[hobu]

All tests pass for me on epimetheus and my intel box. Declaring this one done...