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Oct 9, 2022
…g breaking changes to get joncampbell123#3347 working again (MEM_BlockWrite MUSTN'T be called on ext device, otherwise it overwrites buffer which causes malfunction)
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This pull request fixes the handling of DOS file I/O device drivers
What issue(s) does this PR address?
There are some device drivers that expect a pre-filled input-buffer on READ function (3Fh) and also don't like to be called for every single byte in that buffer. Therefore the current implementation doesn't work correctly for them.
Therefore to do proper buffer transfers, the device driver should be called directly with the correct buffer pointer in place which also eliminates unnecessary copying.
The current code also has a bug that it lets the buffer point to the beginning of the DCP, which is not desirable, because:
dosbox-x/src/dos/dos_devices.cpp
Line 138 in 6533d69
but:
dosbox-x/src/dos/dos_devices.cpp
Line 101 in 6533d69
0x20 & 0xF = 0!