>>> > Quoting Paolo Bonzini (2015-11-11 08:49:57) >> >> >> On 11/11/2015 15:02, Michael Roth wrote: >> >> GENERIC_READ for files >> >> = FILE_READ_DATA >> >> + FILE_READ_ATTRIBUTES >> >> + FILE_READ_EA >> >> + SYNCHRONIZE >> >> + STANDARD_RIGHTS_READ (which is READ_CONTROL) >> >> >> >> GENERIC_WRITE for files >> >> = FILE_APPEND_DATA >> >> + FILE_WRITE_DATA >> >> + FILE_WRITE_ATTRIBUTES >> >> + FILE_WRITE_EA >> >> + SYNCHRONIZE >> >> + STANDARD_RIGHTS_WRITE (which is READ_CONTROL too!) >> >> >> >> Of these of course qemu-ga only needs FILE_*_DATA and possibly >> >> SYNCHRONIZE. >> >> >> >> The above description doesn't say what happens if you specify >> >> FILE_READ_DATA and FILE_APPEND_DATA together, but I guess you can expect >> >> it to just work. >> > >> > Thanks, this is very helpful. This seems to coincide with >> > FILE_GENERIC_WRITE / FILE_GENERIC_READ if you want to access the >> > bitmasks directly (though it looks like you can still add flags >> > to GENERIC_WRITE / GENERIC_READ): >> > >> > > https://msdn.microsoft.com/en-us/library/windows/desktop/aa364399(v=vs.85).as > px >> >> Yes, I had missed the FILE_GENERIC_* definitions. I found them now in >> mingw as well, and they are exactly what you would expect (an | of the >> various flags). >> >> > Looks like the crux of it is that FILE_WRITE_DATA causes us not to ignore >> > the start offset (0) for writes, so we end up writing data at the >> > beginning of the file instead of the end. >> > >> > So I think the following >> > should work: >> > >> > a: FILE_GENERIC_WRITE & ~FILE_WRITE_DATA >> > a+: FILE_GENERIC_READ | FILE_APPEND_DATA >> > >> > FILE_APPEND_DATA by itself might work for a:, but for consistency I >> > think I'd prefer sticking with the generic set and masking out >> > FILE_WRITE_DATA. >> >> For a+ I would use any of >> >> (FILE_GENERIC_READ | FILE_GENERIC_WRITE) & ~FILE_WRITE_DATA >> GENERIC_READ | (FILE_GENERIC_WRITE & ~FILE_WRITE_DATA) >> >> Perhaps you can define this: >> >> #define FILE_GENERIC_APPEND (FILE_GENERIC_WRITE & ~FILE_WRITE_DATA) >> >> and then use >> >> a: FILE_GENERIC_APPEND >> a+: GENERIC_READ|FILE_GENERIC_APPEND >> >> or >> >> a: FILE_GENERIC_APPEND >> a+: FILE_GENERIC_READ|FILE_GENERIC_APPEND > > Yah, both are more proper actually (I was relying on FILE_GENERIC_READ > already containing the other flags from FILE_GENERIC_WRITE, but that's > more likely to break in the future). > > I think I prefer the former since it avoids confusion on GENERIC_READ vs. > FILE_GENERIC_READ differences. > > Kirk, I'm planning on squashing this into your v2 series, so no need to > resubmit.
Sounds great. Thanks - Kirk > > Thanks! > >> >> ? >> >> Paolo >>
