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Mercurial > core / rust/lib/sxp/src/nostd.rs

changeset 8: 1227f932b628
child: 0ccbbd142694
author: ellis <ellis@rwest.io>
date: Tue, 17 Oct 2023 20:36:37 -0400
permissions: -rw-r--r--
description: rust import 
     1 //! nostd.rs --- nostd support
     2 
     3 //! Reimplements core logic and types from `std::io` in an `alloc`-friendly
     4 //! fashion.
     5 
     6 use alloc::vec::Vec;
     7 use core::fmt::{self, Display};
     8 use core::result;
     9 
    10 pub enum ErrorKind {
    11   Other,
    12 }
    13 
    14 // I/O errors can never occur in no-std mode. All our no-std I/O implementations
    15 // are infallible.
    16 pub struct Error;
    17 
    18 impl Display for Error {
    19   fn fmt(&self, _formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
    20     unreachable!()
    21   }
    22 }
    23 
    24 impl Error {
    25   pub(crate) fn new(_kind: ErrorKind, _error: &'static str) -> Error {
    26     Error
    27   }
    28 }
    29 
    30 pub type Result<T> = result::Result<T, Error>;
    31 
    32 pub trait Write {
    33   fn write(&mut self, buf: &[u8]) -> Result<usize>;
    34 
    35   fn write_all(&mut self, buf: &[u8]) -> Result<()> {
    36     // All our Write impls in no_std mode always write the whole buffer in
    37     // one call infallibly.
    38     let result = self.write(buf);
    39     debug_assert!(result.is_ok());
    40     debug_assert_eq!(result.unwrap_or(0), buf.len());
    41     Ok(())
    42   }
    43 
    44   fn flush(&mut self) -> Result<()>;
    45 }
    46 
    47 impl<W: Write> Write for &mut W {
    48   #[inline]
    49   fn write(&mut self, buf: &[u8]) -> Result<usize> {
    50     (*self).write(buf)
    51   }
    52 
    53   #[inline]
    54   fn write_all(&mut self, buf: &[u8]) -> Result<()> {
    55     (*self).write_all(buf)
    56   }
    57 
    58   #[inline]
    59   fn flush(&mut self) -> Result<()> {
    60     (*self).flush()
    61   }
    62 }
    63 
    64 impl Write for Vec<u8> {
    65   #[inline]
    66   fn write(&mut self, buf: &[u8]) -> Result<usize> {
    67     self.extend_from_slice(buf);
    68     Ok(buf.len())
    69   }
    70 
    71   #[inline]
    72   fn write_all(&mut self, buf: &[u8]) -> Result<()> {
    73     self.extend_from_slice(buf);
    74     Ok(())
    75   }
    76 
    77   #[inline]
    78   fn flush(&mut self) -> Result<()> {
    79     Ok(())
    80   }
    81 }