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41 lines
1.1 KiB
41 lines
1.1 KiB
3 years ago
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//! System interactions
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//!
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//! Basic system interactions.
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use super::*;
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/// Attempt to get the size of any stream that is backed by a file-descriptor.
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///
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/// If one cannot be determined (or the fd is unsized), `None` is returned.
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#[cfg_attr(feature="logging", instrument(level="info", skip(reader), ret, fields(reader = std::any::type_name::<R>())))]
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#[inline]
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//TODO: XXX: What if the size of `reader` really *is* 0. We shouldn't use `NonZeroUsize` here, we should just use `usize`. I think `st_size` can be `-1` if `fstat64()` fails to find a size...
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pub fn try_get_size<R: ?Sized>(reader: &R) -> Option<NonZeroUsize>
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where R: AsRawFd
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{
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let fd = reader.as_raw_fd();
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use libc::{
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fstat64,
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stat64,
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};
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if fd < 0 {
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return None;
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}
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let mut st: MaybeUninit<stat64> = MaybeUninit::uninit();
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unsafe {
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match fstat64(fd, st.as_mut_ptr()) {
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0 => {
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NonZeroUsize::new(st.assume_init().st_size as usize)
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},
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_ => None,
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}
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}
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}
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/// Get the current stream position of any seekable stream.
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#[inline(always)]
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pub fn tell_file<T>(file: &mut T) -> io::Result<u64>
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where T: io::Seek + ?Sized
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{
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file.stream_position()
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}
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