Inefficient FILE I/O (especially in openmpt::could_open_propability):
libopenmpt currently pre-caches the whole file in more situations than theoretically necessary.
This is caused mainly by calls to FileReader::GetRawData() or calls to FileReader::GetLength() (for unseekable streams).
GetRawData() always precaches the whole file. Theoretically, only from the current position would be necessary. Ultimately, GetRawData() will always require a view to almost the complete file data as contiguous memory. Many GetRawData() uses have been removed in r6102 and related revisions.
Even seekable streams are currently completely cached while reading.
This results in twice the filesize of memory consumption: 1. the cache and 2. the parsed file. This hurts platforms with low memory. Somewhere around r6102, this was also improved.
Status as of r6641:
GetRawData() still always pre-caches the whole file. However, it is only used rarely now.
As of r6140, almost all cases relevant to libopenmpt in practice have been converted to not use GetRawData() anymore.
The remaining offenders are: MMCMP, XPK, PP20 depackers and MDL, MED loaders (which need a full loader rewrite anyway).
