qubit_io/std_io/ext/
write_ext.rs

1// =============================================================================
2//    Copyright (c) 2026 Haixing Hu.
3//
4//    SPDX-License-Identifier: Apache-2.0
5//
6//    Licensed under the Apache License, Version 2.0.
7// =============================================================================
8
9//! Extension operations for standard byte writers.
10
11use std::io::Result;
12use std::io::Write;
13
14use crate::util::UncheckedSlice;
15
16/// Extension methods for [`Write`] values.
17///
18/// `WriteExt` provides small method-style helpers for byte writers. The
19/// methods are implemented for every type that implements [`Write`], including
20/// `dyn Write` trait objects.
21pub trait WriteExt: Write {
22    /// Writes bytes from a range of `buffer` without checking the range bounds
23    /// in release builds.
24    ///
25    /// This method delegates to [`Write::write`] after creating the source
26    /// slice with raw pointer arithmetic. It performs at most one write
27    /// operation and returns the number of bytes written, keeping the same
28    /// short-write and error behavior as [`Write::write`].
29    ///
30    /// # Parameters
31    /// - `buffer`: Source buffer.
32    /// - `start_index`: Start offset inside `buffer`.
33    /// - `count`: Maximum number of bytes to write.
34    ///
35    /// # Returns
36    /// The number of bytes written from `buffer[start_index..start_index +
37    /// count]`. The value is in `0..=count`.
38    ///
39    /// # Errors
40    /// Returns the error reported by [`Write::write`].
41    ///
42    /// # Panics
43    /// Panics in debug builds if the requested source range does not fit.
44    ///
45    /// # Safety
46    /// The caller must guarantee that `start_index..start_index + count` is a
47    /// valid range within `buffer` and that `start_index + count` does not
48    /// overflow `usize`.
49    #[inline(always)]
50    unsafe fn write_unchecked(&mut self, buffer: &[u8], start_index: usize, count: usize) -> Result<usize> {
51        // SAFETY: The caller guarantees that the computed pointer and length
52        // form a valid subslice of `buffer`.
53        let source = unsafe { UncheckedSlice::subslice(buffer, start_index, count) };
54        self.write(source)
55    }
56
57    /// Writes exactly `count` bytes from a range of `buffer` without checking
58    /// the range bounds in release builds.
59    ///
60    /// This method delegates to [`Write::write_all`] after creating the source
61    /// slice with raw pointer arithmetic. It keeps the same short-write,
62    /// [`std::io::ErrorKind::Interrupted`], and
63    /// [`std::io::ErrorKind::WriteZero`] behavior as [`Write::write_all`].
64    ///
65    /// # Parameters
66    /// - `buffer`: Source buffer.
67    /// - `start_index`: Start offset inside `buffer`.
68    /// - `count`: Number of bytes to write.
69    ///
70    /// # Returns
71    /// `Ok(())` after the requested range has been written.
72    ///
73    /// # Errors
74    /// Returns the error reported by [`Write::write_all`].
75    ///
76    /// # Panics
77    /// Panics in debug builds if the requested source range does not fit.
78    ///
79    /// # Safety
80    /// The caller must guarantee that `start_index..start_index + count` is a
81    /// valid range within `buffer` and that `start_index + count` does not
82    /// overflow `usize`.
83    #[inline(always)]
84    unsafe fn write_all_unchecked(&mut self, buffer: &[u8], start_index: usize, count: usize) -> Result<()> {
85        // SAFETY: The caller guarantees that the computed pointer and length
86        // form a valid subslice of `buffer`.
87        let source = unsafe { UncheckedSlice::subslice(buffer, start_index, count) };
88        self.write_all(source)
89    }
90}
91
92impl<T> WriteExt for T where T: Write + ?Sized {}
qubit_io/std_io/ext/write_ext.rs

qubit_io/std_io/ext/
write_ext.rs
