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

changeset 698: 96958d3eb5b0
parent: 0ccbbd142694
author: Richard Westhaver <ellis@rwest.io>
date: Fri, 04 Oct 2024 22:04:59 -0400
permissions: -rw-r--r--
description: fixes 
     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::{
     8   fmt::{self, Display},
     9   result,
    10 };
    11 
    12 pub enum ErrorKind {
    13   Other,
    14 }
    15 
    16 // I/O errors can never occur in no-std mode. All our no-std I/O implementations
    17 // are infallible.
    18 pub struct Error;
    19 
    20 impl Display for Error {
    21   fn fmt(&self, _formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
    22     unreachable!()
    23   }
    24 }
    25 
    26 impl Error {
    27   pub(crate) fn new(_kind: ErrorKind, _error: &'static str) -> Error {
    28     Error
    29   }
    30 }
    31 
    32 pub type Result<T> = result::Result<T, Error>;
    33 
    34 pub trait Write {
    35   fn write(&mut self, buf: &[u8]) -> Result<usize>;
    36 
    37   fn write_all(&mut self, buf: &[u8]) -> Result<()> {
    38     // All our Write impls in no_std mode always write the whole buffer in
    39     // one call infallibly.
    40     let result = self.write(buf);
    41     debug_assert!(result.is_ok());
    42     debug_assert_eq!(result.unwrap_or(0), buf.len());
    43     Ok(())
    44   }
    45 
    46   fn flush(&mut self) -> Result<()>;
    47 }
    48 
    49 impl<W: Write> Write for &mut W {
    50   #[inline]
    51   fn write(&mut self, buf: &[u8]) -> Result<usize> {
    52     (*self).write(buf)
    53   }
    54 
    55   #[inline]
    56   fn write_all(&mut self, buf: &[u8]) -> Result<()> {
    57     (*self).write_all(buf)
    58   }
    59 
    60   #[inline]
    61   fn flush(&mut self) -> Result<()> {
    62     (*self).flush()
    63   }
    64 }
    65 
    66 impl Write for Vec<u8> {
    67   #[inline]
    68   fn write(&mut self, buf: &[u8]) -> Result<usize> {
    69     self.extend_from_slice(buf);
    70     Ok(buf.len())
    71   }
    72 
    73   #[inline]
    74   fn write_all(&mut self, buf: &[u8]) -> Result<()> {
    75     self.extend_from_slice(buf);
    76     Ok(())
    77   }
    78 
    79   #[inline]
    80   fn flush(&mut self) -> Result<()> {
    81     Ok(())
    82   }
    83 }