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Add write_all_at for compatibility with FileExt, improve docs a little

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This commit is contained in:
Thom Chiovoloni 2020-10-04 15:38:43 -07:00
parent d61fe36237
commit 587fdeb185
1 changed files with 23 additions and 3 deletions
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26
src/blob/pos_io.rs
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@ -19,6 +19,12 @@ impl<'conn> Blob<'conn> {
/// Note: This is part of the positional I/O API, and thus takes an absolute
/// position write to, instead of using the internal position that can be
/// manipulated by the `std::io` traits.
///
/// Unlike the similarly named [`FileExt::write_at`][fext_write_at] function
/// (from `std::os::unix`), it's always an error to perform a "short write".
///
/// [fext_write_at]: https://doc.rust-lang.org/std/os/unix/fs/trait.FileExt.html#tymethod.write_at
#[inline]
pub fn write_at(&mut self, buf: &[u8], write_start: usize) -> Result<()> {
let len = self.len();
@ -49,6 +55,16 @@ impl<'conn> Blob<'conn> {
Ok(())
}
/// An alias for `write_at` provided for compatibility with the conceptually
/// equivalent [`std::os::unix::FileExt::write_all_at`][write_all_at]
/// function from libstd:
///
/// [write_all_at]: https://doc.rust-lang.org/std/os/unix/fs/trait.FileExt.html#method.write_all_at
#[inline]
pub fn write_all_at(&mut self, buf: &[u8], write_start: usize) -> Result<()> {
self.write_at(buf, write_start)
}
/// Read as much as possible from `offset` to `offset + buf.len()` out of
/// `self`, writing into `buf`. On success, returns the number of bytes
/// written.
@ -63,7 +79,8 @@ impl<'conn> Blob<'conn> {
/// Note: This is part of the positional I/O API, and thus takes an absolute
/// position to read from, instead of using the internal position that can
/// be manipulated by the `std::io` traits. Consequently, it does not change
/// that value. either.
/// that value either.
#[inline]
pub fn read_at(&self, buf: &mut [u8], read_start: usize) -> Result<usize> {
// Safety: this is safe because `raw_read_at` never stores uninitialized
// data into `as_uninit`.
@ -85,7 +102,8 @@ impl<'conn> Blob<'conn> {
/// Note: This is part of the positional I/O API, and thus takes an absolute
/// position to read from, instead of using the internal position that can
/// be manipulated by the `std::io` traits. Consequently, it does not change
/// that value. either.
/// that value either.
#[inline]
pub fn raw_read_at<'a>(
&self,
buf: &'a mut [MaybeUninit<u8>],
@ -146,6 +164,7 @@ impl<'conn> Blob<'conn> {
/// Equivalent to [`Blob::read_at`], but returns a `BlobSizeError` if `buf`
/// is not fully initialized.
#[inline]
pub fn read_at_exact(&self, buf: &mut [u8], read_start: usize) -> Result<()> {
let n = self.read_at(buf, read_start)?;
if n != buf.len() {
@ -157,6 +176,7 @@ impl<'conn> Blob<'conn> {
/// Equivalent to [`Blob::raw_read_at`], but returns a `BlobSizeError` if
/// `buf` is not fully initialized.
#[inline]
pub fn raw_read_at_exact<'a>(
&self,
buf: &'a mut [MaybeUninit<u8>],
@ -226,7 +246,7 @@ mod test {
blob.read_at_exact(&mut [], 0).unwrap();
blob.read_at_exact(&mut [], 5).unwrap();
blob.write_at(&[16, 17, 18, 19, 20], 5).unwrap();
blob.write_all_at(&[16, 17, 18, 19, 20], 5).unwrap();
blob.read_at_exact(&mut s, 0).unwrap();
assert_eq!(&s, &[1u8, 2, 3, 4, 5, 16, 17, 18, 19, 20]);