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mortbopet
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Sep 2, 2023
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Some comments - bonus points if you can also come up with a unit test to verify your changes :).
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| return (fileFlags[fd] + 1) & 1; // LSB is 1 if the fd has read perms | ||
| } | ||
| return false; | ||
| return (fileFlags[fd] + 1) & 2; // 2nd LSB is 1 if the fd has write perms |
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Mixing arithmetic and bitwise logic is a bit too funky for me. I think these expressions can be rewritten using bit extracts and XORs.
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secondly, we should also extract out the nth LSB is X perms to an enum, e.g. something like
enum FilePermissions {
RD_PERM_FLAG = 1 << 0,
WR_PERM_FLAG = 1 << 1
};| static constexpr int O_TRUNC = 0x00000400; // 1024 | ||
| static constexpr int O_EXCL = 0x00000800; // 2048 | ||
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| enum Permission { |
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The fdInUse function passed in O_WRONLY | O_RDWR as flags and then checked fileFlags[fd] & flags == flags. This is only true if all of the bits set in flags are also set in fileFlags[fd]. Since O_WRONLY | O_RDWR are mutually exclusive the fdInUse function always returns false in this case and the write syscall fails.
I fixed the expression and passed in an enum instead to make it more explicit about what we are testing for.