// SPDX-License-Identifier: GPL-2.0
//! String representations.
use crate::alloc::{flags::*, vec_ext::VecExt, AllocError};
use alloc::vec::Vec;
use core::fmt::{self, Write};
use core::ops::{self, Deref, DerefMut, Index};
use crate::error::{code::*, Error};
/// Byte string without UTF-8 validity guarantee.
#[repr(transparent)]
pub struct BStr([u8]);
impl BStr {
/// Returns the length of this string.
#[inline]
pub const fn len(&self) -> usize {
self.0.len()
}
/// Returns `true` if the string is empty.
#[inline]
pub const fn is_empty(&self) -> bool {
self.len() == 0
}
/// Creates a [`BStr`] from a `[u8]`.
#[inline]
pub const fn from_bytes(bytes: &[u8]) -> &Self {
// SAFETY: `BStr` is transparent to `[u8]`.
unsafe { &*(bytes as *const [u8] as *const BStr) }
}
}
impl fmt::Display for BStr {
/// Formats printable ASCII characters, escaping the rest.
///
/// ```
/// # use kernel::{fmt, b_str, str::{BStr, CString}};
/// let ascii = b_str!("Hello, BStr!");
/// let s = CString::try_from_fmt(fmt!("{}", ascii)).unwrap();
/// assert_eq!(s.as_bytes(), "Hello, BStr!".as_bytes());
///
/// let non_ascii = b_str!("🦀");
/// let s = CString::try_from_fmt(fmt!("{}", non_ascii)).unwrap();
/// assert_eq!(s.as_bytes(), "\\xf0\\x9f\\xa6\\x80".as_bytes());
/// ```
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
for &b in &self.0 {
match b {
// Common escape codes.
b'\t' => f.write_str("\\t")?,
b'\n' => f.write_str("\\n")?,
b'\r' => f.write_str("\\r")?,
// Printable characters.
0x20..=0x7e => f.write_char(b as char)?,
_ => write!(f, "\\x{:02x}", b)?,
}
}
Ok(())
}
}
impl fmt::Debug for BStr {
/// Formats printable ASCII characters with a double quote on either end,
/// escaping the rest.
///
/// ```
/// # use kernel::{fmt, b_str, str::{BStr, CString}};
/// // Embedded double quotes are escaped.
/// let ascii = b_str!("Hello, \"BStr\"!");
/// let s = CString::try_from_fmt(fmt!("{:?}", ascii)).unwrap();
/// assert_eq!(s.as_bytes(), "\"Hello, \\\"BStr\\\"!\"".as_bytes());
///
/// let non_ascii = b_str!("😺");
/// let s = CString::try_from_fmt(fmt!("{:?}", non_ascii)).unwrap();
/// assert_eq!(s.as_bytes(), "\"\\xf0\\x9f\\x98\\xba\"".as_bytes());
/// ```
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.write_char('"')?;
for &b in &self.0 {
match b {
// Common escape codes.
b'\t' => f.write_str("\\t")?,
b'\n' => f.write_str("\\n")?,
b'\r' => f.write_str("\\r")?,
// String escape characters.
b'\"' => f.write_str("\\\"")?,
b'\\' => f.write_str("\\\\")?,
// Printable characters.
0x20..=0x7e => f.write_char(b as char)?,
_ => write!(f, "\\x{:02x}", b)?,
}
}
f.write_char('"')
}
}
impl Deref for BStr {
type Target = [u8];
#[inline]
fn deref(&self) -> &Self::Target {
&self.0
}
}
/// Creates a new [`BStr`] from a string literal.
///
/// `b_str!` converts the supplied string literal to byte string, so non-ASCII
/// characters can be included.
///
/// # Examples
///
/// ```
/// # use kernel::b_str;
/// # use kernel::str::BStr;
/// const MY_BSTR: &BStr = b_str!("My awesome BStr!");
/// ```
#[macro_export]
macro_rules! b_str {
($str:literal) => {{
const S: &'static str = $str;
const C: &'static $crate::str::BStr = $crate::str::BStr::from_bytes(S.as_bytes());
C
}};
}
/// Possible errors when using conversion functions in [`CStr`].
#[derive(Debug, Clone, Copy)]
pub enum CStrConvertError {
/// Supplied bytes contain an interior `NUL`.
InteriorNul,
/// Supplied bytes are not terminated by `NUL`.
NotNulTerminated,
}
impl From<CStrConvertError> for Error {
#[inline]
fn from(_: CStrConvertError) -> Error {
EINVAL
}
}
/// A string that is guaranteed to have exactly one `NUL` byte, which is at the
/// end.
///
/// Used for interoperability with kernel APIs that take C strings.
#[repr(transparent)]
pub struct CStr([u8]);
impl CStr {
/// Returns the length of this string excluding `NUL`.
#[inline]
pub const fn len(&self) -> usize {
self.len_with_nul() - 1
}
/// Returns the length of this string with `NUL`.
#[inline]
pub const fn len_with_nul(&self) -> usize {
// SAFETY: This is one of the invariant of `CStr`.
// We add a `unreachable_unchecked` here to hint the optimizer that
// the value returned from this function is non-zero.
if self.0.is_empty() {
unsafe { core::hint::unreachable_unchecked() };
}
self.0.len()
}
/// Returns `true` if the string only includes `NUL`.
#[inline]
pub const fn is_empty(&self) -> bool {
self.len() == 0
}
/// Wraps a raw C string pointer.
///
/// # Safety
///
/// `ptr` must be a valid pointer to a `NUL`-terminated C string, and it must
/// last at least `'a`. When `CStr` is alive, the memory pointed by `ptr`
/// must not be mutated.
#[inline]
pub unsafe fn from_char_ptr<'a>(ptr: *const core::ffi::c_char) -> &'a Self {
// SAFETY: The safety precondition guarantees `ptr` is a valid pointer
// to a `NUL`-terminated C string.
let len = unsafe { bindings::strlen(ptr) } + 1;
// SAFETY: Lifetime guaranteed by the safety precondition.
let bytes = unsafe { core::slice::from_raw_parts(ptr as _, len as _) };
// SAFETY: As `len` is returned by `strlen`, `bytes` does not contain interior `NUL`.
// As we have added 1 to `len`, the last byte is known to be `NUL`.
unsafe { Self::from_bytes_with_nul_unchecked(bytes) }
}
/// Creates a [`CStr`] from a `[u8]`.
///
/// The provided slice must be `NUL`-terminated, does not contain any
/// interior `NUL` bytes.
pub const fn from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, CStrConvertError> {
if bytes.is_empty() {
return Err(CStrConvertError::NotNulTerminated);
}
if bytes[bytes.len() - 1] != 0 {
return Err(CStrConvertError::NotNulTerminated);
}
let mut i = 0;
// `i + 1 < bytes.len()` allows LLVM to optimize away bounds checking,
// while it couldn't optimize away bounds checks for `i < bytes.len() - 1`.
while i + 1 < bytes.len() {
if bytes[i] == 0 {
return Err(CStrConvertError::InteriorNul);
}
i += 1;
}
// SAFETY: We just checked that all properties hold.
Ok(unsafe { Self::from_bytes_with_nul_unchecked(bytes) })
}
/// Creates a [`CStr`] from a `[u8]` without performing any additional
/// checks.
///
/// # Safety
///
/// `bytes` *must* end with a `NUL` byte, and should only have a single
/// `NUL` byte (or the string will be truncated).
#[inline]
pub const unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {
// SAFETY: Properties of `bytes` guaranteed by the safety precondition.
unsafe { core::mem::transmute(bytes) }
}
/// Creates a mutable [`CStr`] from a `[u8]` without performing any
/// additional checks.
///
/// # Safety
///
/// `bytes` *must* end with a `NUL` byte, and should only have a single
/// `NUL` byte (or the string will be truncated).
#[inline]
pub unsafe fn from_bytes_with_nul_unchecked_mut(bytes: &mut [u8]) -> &mut CStr {
// SAFETY: Properties of `bytes` guaranteed by the safety precondition.
unsafe { &mut *(bytes as *mut [u8] as *mut CStr) }
}
/// Returns a C pointer to the string.
#[inline]
pub const fn as_char_ptr(&self) -> *const core::ffi::c_char {
self.0.as_ptr() as _
}
/// Convert the string to a byte slice without the trailing `NUL` byte.
#[inline]
pub fn as_bytes(&self) -> &[u8] {
&self.0[..self.len()]
}
/// Convert the string to a byte slice containing the trailing `NUL` byte.
#[inline]
pub const fn as_bytes_with_nul(&self) -> &[u8] {
&self.0
}
/// Yields a [`&str`] slice if the [`CStr`] contains valid UTF-8.
///
/// If the contents of the [`CStr`] are valid UTF-8 data, this
/// function will return the corresponding [`&str`] slice. Otherwise,
/// it will return an error with details of where UTF-8 validation failed.
///
/// # Examples
///
/// ```
/// # use kernel::str::CStr;
/// let cstr = CStr::from_bytes_with_nul(b"foo\0").unwrap();
/// assert_eq!(cstr.to_str(), Ok("foo"));
/// ```
#[inline]
pub fn to_str(&self) -> Result<&str, core::str::Utf8Error> {
core::str::from_utf8(self.as_bytes())
}
/// Unsafely convert this [`CStr`] into a [`&str`], without checking for
/// valid UTF-8.
///
/// # Safety
///
/// The contents must be valid UTF-8.
///
/// # Examples
///
/// ```
/// # use kernel::c_str;
/// # use kernel::str::CStr;
/// let bar = c_str!("ツ");
/// // SAFETY: String literals are guaranteed to be valid UTF-8
/// // by the Rust compiler.
/// assert_eq!(unsafe { bar.as_str_unchecked() }, "ツ");
/// ```
#[inline]
pub unsafe fn as_str_unchecked(&self) -> &str {
unsafe { core::str::from_utf8_unchecked(self.as_bytes()) }
}
/// Convert this [`CStr`] into a [`CString`] by allocating memory and
/// copying over the string data.
pub fn to_cstring(&self) -> Result<CString, AllocError> {
CString::try_from(self)
}
/// Converts this [`CStr`] to its ASCII lower case equivalent in-place.
///
/// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
/// but non-ASCII letters are unchanged.
///
/// To return a new lowercased value without modifying the existing one, use
/// [`to_ascii_lowercase()`].
///
/// [`to_ascii_lowercase()`]: #method.to_ascii_lowercase
pub fn make_ascii_lowercase(&mut self) {
// INVARIANT: This doesn't introduce or remove NUL bytes in the C
// string.
self.0.make_ascii_lowercase();
}
/// Converts this [`CStr`] to its ASCII upper case equivalent in-place.
///
/// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
/// but non-ASCII letters are unchanged.
///
/// To return a new uppercased value without modifying the existing one, use
/// [`to_ascii_uppercase()`].
///
/// [`to_ascii_uppercase()`]: #method.to_ascii_uppercase
pub fn make_ascii_uppercase(&mut self) {
// INVARIANT: This doesn't introduce or remove NUL bytes in the C
// string.
self.0.make_ascii_uppercase();
}
/// Returns a copy of this [`CString`] where each character is mapped to its
/// ASCII lower case equivalent.
///
/// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
/// but non-ASCII letters are unchanged.
///
/// To lowercase the value in-place, use [`make_ascii_lowercase`].
///
/// [`make_ascii_lowercase`]: str::make_ascii_lowercase
pub fn to_ascii_lowercase(&self) -> Result<CString, AllocError> {
let mut s = self.to_cstring()?;
s.make_ascii_lowercase();
Ok(s)
}
/// Returns a copy of this [`CString`] where each character is mapped to its
/// ASCII upper case equivalent.
///
/// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
/// but non-ASCII letters are unchanged.
///
/// To uppercase the value in-place, use [`make_ascii_uppercase`].
///
/// [`make_ascii_uppercase`]: str::make_ascii_uppercase
pub fn to_ascii_uppercase(&self) -> Result<CString, AllocError> {
let mut s = self.to_cstring()?;
s.make_ascii_uppercase();
Ok(s)
}
}
impl fmt::Display for CStr {
/// Formats printable ASCII characters, escaping the rest.
///
/// ```
/// # use kernel::c_str;
/// # use kernel::fmt;
/// # use kernel::str::CStr;
/// # use kernel::str::CString;
/// let penguin = c_str!("🐧");
/// let s = CString::try_from_fmt(fmt!("{}", penguin)).unwrap();
/// assert_eq!(s.as_bytes_with_nul(), "\\xf0\\x9f\\x90\\xa7\0".as_bytes());
///
/// let ascii = c_str!("so \"cool\"");
/// let s = CString::try_from_fmt(fmt!("{}", ascii)).unwrap();
/// assert_eq!(s.as_bytes_with_nul(), "so \"cool\"\0".as_bytes());
/// ```
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
for &c in self.as_bytes() {
if (0x20..0x7f).contains(&c) {
// Printable character.
f.write_char(c as char)?;
} else {
write!(f, "\\x{:02x}", c)?;
}
}
Ok(())
}
}
impl fmt::Debug for CStr {
/// Formats printable ASCII characters with a double quote on either end, escaping the rest.
///
/// ```
/// # use kernel::c_str;
/// # use kernel::fmt;
/// # use kernel::str::CStr;
/// # use kernel::str::CString;
/// let penguin = c_str!("🐧");
/// let s = CString::try_from_fmt(fmt!("{:?}", penguin)).unwrap();
/// assert_eq!(s.as_bytes_with_nul(), "\"\\xf0\\x9f\\x90\\xa7\"\0".as_bytes());
///
/// // Embedded double quotes are escaped.
/// let ascii = c_str!("so \"cool\"");
/// let s = CString::try_from_fmt(fmt!("{:?}", ascii)).unwrap();
/// assert_eq!(s.as_bytes_with_nul(), "\"so \\\"cool\\\"\"\0".as_bytes());
/// ```
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.write_str("\"")?;
for &c in self.as_bytes() {
match c {
// Printable characters.
b'\"' => f.write_str("\\\"")?,
0x20..=0x7e => f.write_char(c as char)?,
_ => write!(f, "\\x{:02x}", c)?,
}
}
f.write_str("\"")
}
}
impl AsRef<BStr> for CStr {
#[inline]
fn as_ref(&self) -> &BStr {
BStr::from_bytes(self.as_bytes())
}
}
impl Deref for CStr {
type Target = BStr;
#[inline]
fn deref(&self) -> &Self::Target {
self.as_ref()
}
}
impl Index<ops::RangeFrom<usize>> for CStr {
type Output = CStr;
#[inline]
fn index(&self, index: ops::RangeFrom<usize>) -> &Self::Output {
// Delegate bounds checking to slice.
// Assign to _ to mute clippy's unnecessary operation warning.
let _ = &self.as_bytes()[index.start..];
// SAFETY: We just checked the bounds.
unsafe { Self::from_bytes_with_nul_unchecked(&self.0[index.start..]) }
}
}
impl Index<ops::RangeFull> for CStr {
type Output = CStr;
#[inline]
fn index(&self, _index: ops::RangeFull) -> &Self::Output {
self
}
}
mod private {
use core::ops;
// Marker trait for index types that can be forward to `BStr`.
pub trait CStrIndex {}
impl CStrIndex for usize {}
impl CStrIndex for ops::Range<usize> {}
impl CStrIndex for ops::RangeInclusive<usize> {}
impl CStrIndex for ops::RangeToInclusive<usize> {}
}
impl<Idx> Index<Idx> for CStr
where
Idx: private::CStrIndex,
BStr: Index<Idx>,
{
type Output = <BStr as Index<Idx>>::Output;
#[inline]
fn index(&self, index: Idx) -> &Self::Output {
&self.as_ref()[index]
}
}
/// Creates a new [`CStr`] from a string literal.
///
/// The string literal should not contain any `NUL` bytes.
///
/// # Examples
///
/// ```
/// # use kernel::c_str;
/// # use kernel::str::CStr;
/// const MY_CSTR: &CStr = c_str!("My awesome CStr!");
/// ```
#[macro_export]
macro_rules! c_str {
($str:expr) => {{
const S: &str = concat!($str, "\0");
const C: &$crate::str::CStr = match $crate::str::CStr::from_bytes_with_nul(S.as_bytes()) {
Ok(v) => v,
Err(_) => panic!("string contains interior NUL"),
};
C
}};
}
#[cfg(test)]
mod tests {
use super::*;
use alloc::format;
const ALL_ASCII_CHARS: &'static str =
"\\x01\\x02\\x03\\x04\\x05\\x06\\x07\\x08\\x09\\x0a\\x0b\\x0c\\x0d\\x0e\\x0f\
\\x10\\x11\\x12\\x13\\x14\\x15\\x16\\x17\\x18\\x19\\x1a\\x1b\\x1c\\x1d\\x1e\\x1f \
!\"#$%&'()*+,-./0123456789:;<=>?@\
ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\\x7f\
\\x80\\x81\\x82\\x83\\x84\\x85\\x86\\x87\\x88\\x89\\x8a\\x8b\\x8c\\x8d\\x8e\\x8f\
\\x90\\x91\\x92\\x93\\x94\\x95\\x96\\x97\\x98\\x99\\x9a\\x9b\\x9c\\x9d\\x9e\\x9f\
\\xa0\\xa1\\xa2\\xa3\\xa4\\xa5\\xa6\\xa7\\xa8\\xa9\\xaa\\xab\\xac\\xad\\xae\\xaf\
\\xb0\\xb1\\xb2\\xb3\\xb4\\xb5\\xb6\\xb7\\xb8\\xb9\\xba\\xbb\\xbc\\xbd\\xbe\\xbf\
\\xc0\\xc1\\xc2\\xc3\\xc4\\xc5\\xc6\\xc7\\xc8\\xc9\\xca\\xcb\\xcc\\xcd\\xce\\xcf\
\\xd0\\xd1\\xd2\\xd3\\xd4\\xd5\\xd6\\xd7\\xd8\\xd9\\xda\\xdb\\xdc\\xdd\\xde\\xdf\
\\xe0\\xe1\\xe2\\xe3\\xe4\\xe5\\xe6\\xe7\\xe8\\xe9\\xea\\xeb\\xec\\xed\\xee\\xef\
\\xf0\\xf1\\xf2\\xf3\\xf4\\xf5\\xf6\\xf7\\xf8\\xf9\\xfa\\xfb\\xfc\\xfd\\xfe\\xff";
#[test]
fn test_cstr_to_str() {
let good_bytes = b"\xf0\x9f\xa6\x80\0";
let checked_cstr = CStr::from_bytes_with_nul(good_bytes).unwrap();
let checked_str = checked_cstr.to_str().unwrap();
assert_eq!(checked_str, "🦀");
}
#[test]
#[should_panic]
fn test_cstr_to_str_panic() {
let bad_bytes = b"\xc3\x28\0";
let checked_cstr = CStr::from_bytes_with_nul(bad_bytes).unwrap();
checked_cstr.to_str().unwrap();
}
#[test]
fn test_cstr_as_str_unchecked() {
let good_bytes = b"\xf0\x9f\x90\xA7\0";
let checked_cstr = CStr::from_bytes_with_nul(good_bytes).unwrap();
let unchecked_str = unsafe { checked_cstr.as_str_unchecked() };
assert_eq!(unchecked_str, "🐧");
}
#[test]
fn test_cstr_display() {
let hello_world = CStr::from_bytes_with_nul(b"hello, world!\0").unwrap();
assert_eq!(format!("{}", hello_world), "hello, world!");
let non_printables = CStr::from_bytes_with_nul(b"\x01\x09\x0a\0").unwrap();
assert_eq!(format!("{}", non_printables), "\\x01\\x09\\x0a");
let non_ascii = CStr::from_bytes_with_nul(b"d\xe9j\xe0 vu\0").unwrap();
assert_eq!(format!("{}", non_ascii), "d\\xe9j\\xe0 vu");
let good_bytes = CStr::from_bytes_with_nul(b"\xf0\x9f\xa6\x80\0").unwrap();
assert_eq!(format!("{}", good_bytes), "\\xf0\\x9f\\xa6\\x80");
}
#[test]
fn test_cstr_display_all_bytes() {
let mut bytes: [u8; 256] = [0; 256];
// fill `bytes` with [1..=255] + [0]
for i in u8::MIN..=u8::MAX {
bytes[i as usize] = i.wrapping_add(1);
}
let cstr = CStr::from_bytes_with_nul(&bytes).unwrap();
assert_eq!(format!("{}", cstr), ALL_ASCII_CHARS);
}
#[test]
fn test_cstr_debug() {
let hello_world = CStr::from_bytes_with_nul(b"hello, world!\0").unwrap();
assert_eq!(format!("{:?}", hello_world), "\"hello, world!\"");
let non_printables = CStr::from_bytes_with_nul(b"\x01\x09\x0a\0").unwrap();
assert_eq!(format!("{:?}", non_printables), "\"\\x01\\x09\\x0a\"");
let non_ascii = CStr::from_bytes_with_nul(b"d\xe9j\xe0 vu\0").unwrap();
assert_eq!(format!("{:?}", non_ascii), "\"d\\xe9j\\xe0 vu\"");
let good_bytes = CStr::from_bytes_with_nul(b"\xf0\x9f\xa6\x80\0").unwrap();
assert_eq!(format!("{:?}", good_bytes), "\"\\xf0\\x9f\\xa6\\x80\"");
}
#[test]
fn test_bstr_display() {
let hello_world = BStr::from_bytes(b"hello, world!");
assert_eq!(format!("{}", hello_world), "hello, world!");
let escapes = BStr::from_bytes(b"_\t_\n_\r_\\_\'_\"_");
assert_eq!(format!("{}", escapes), "_\\t_\\n_\\r_\\_'_\"_");
let others = BStr::from_bytes(b"\x01");
assert_eq!(format!("{}", others), "\\x01");
let non_ascii = BStr::from_bytes(b"d\xe9j\xe0 vu");
assert_eq!(format!("{}", non_ascii), "d\\xe9j\\xe0 vu");
let good_bytes = BStr::from_bytes(b"\xf0\x9f\xa6\x80");
assert_eq!(format!("{}", good_bytes), "\\xf0\\x9f\\xa6\\x80");
}
#[test]
fn test_bstr_debug() {
let hello_world = BStr::from_bytes(b"hello, world!");
assert_eq!(format!("{:?}", hello_world), "\"hello, world!\"");
let escapes = BStr::from_bytes(b"_\t_\n_\r_\\_\'_\"_");
assert_eq!(format!("{:?}", escapes), "\"_\\t_\\n_\\r_\\\\_'_\\\"_\"");
let others = BStr::from_bytes(b"\x01");
assert_eq!(format!("{:?}", others), "\"\\x01\"");
let non_ascii = BStr::from_bytes(b"d\xe9j\xe0 vu");
assert_eq!(format!("{:?}", non_ascii), "\"d\\xe9j\\xe0 vu\"");
let good_bytes = BStr::from_bytes(b"\xf0\x9f\xa6\x80");
assert_eq!(format!("{:?}", good_bytes), "\"\\xf0\\x9f\\xa6\\x80\"");
}
}
/// Allows formatting of [`fmt::Arguments`] into a raw buffer.
///
/// It does not fail if callers write past the end of the buffer so that they can calculate the
/// size required to fit everything.
///
/// # Invariants
///
/// The memory region between `pos` (inclusive) and `end` (exclusive) is valid for writes if `pos`
/// is less than `end`.
pub(crate) struct RawFormatter {
// Use `usize` to use `saturating_*` functions.
beg: usize,
pos: usize,
end: usize,
}
impl RawFormatter {
/// Creates a new instance of [`RawFormatter`] with an empty buffer.
fn new() -> Self {
// INVARIANT: The buffer is empty, so the region that needs to be writable is empty.
Self {
beg: 0,
pos: 0,
end: 0,
}
}
/// Creates a new instance of [`RawFormatter`] with the given buffer pointers.
///
/// # Safety
///
/// If `pos` is less than `end`, then the region between `pos` (inclusive) and `end`
/// (exclusive) must be valid for writes for the lifetime of the returned [`RawFormatter`].
pub(crate) unsafe fn from_ptrs(pos: *mut u8, end: *mut u8) -> Self {
// INVARIANT: The safety requirements guarantee the type invariants.
Self {
beg: pos as _,
pos: pos as _,
end: end as _,
}
}
/// Creates a new instance of [`RawFormatter`] with the given buffer.
///
/// # Safety
///
/// The memory region starting at `buf` and extending for `len` bytes must be valid for writes
/// for the lifetime of the returned [`RawFormatter`].
pub(crate) unsafe fn from_buffer(buf: *mut u8, len: usize) -> Self {
let pos = buf as usize;
// INVARIANT: We ensure that `end` is never less then `buf`, and the safety requirements
// guarantees that the memory region is valid for writes.
Self {
pos,
beg: pos,
end: pos.saturating_add(len),
}
}
/// Returns the current insert position.
///
/// N.B. It may point to invalid memory.
pub(crate) fn pos(&self) -> *mut u8 {
self.pos as _
}
/// Returns the number of bytes written to the formatter.
pub(crate) fn bytes_written(&self) -> usize {
self.pos - self.beg
}
}
impl fmt::Write for RawFormatter {
fn write_str(&mut self, s: &str) -> fmt::Result {
// `pos` value after writing `len` bytes. This does not have to be bounded by `end`, but we
// don't want it to wrap around to 0.
let pos_new = self.pos.saturating_add(s.len());
// Amount that we can copy. `saturating_sub` ensures we get 0 if `pos` goes past `end`.
let len_to_copy = core::cmp::min(pos_new, self.end).saturating_sub(self.pos);
if len_to_copy > 0 {
// SAFETY: If `len_to_copy` is non-zero, then we know `pos` has not gone past `end`
// yet, so it is valid for write per the type invariants.
unsafe {
core::ptr::copy_nonoverlapping(
s.as_bytes().as_ptr(),
self.pos as *mut u8,
len_to_copy,
)
};
}
self.pos = pos_new;
Ok(())
}
}
/// Allows formatting of [`fmt::Arguments`] into a raw buffer.
///
/// Fails if callers attempt to write more than will fit in the buffer.
pub(crate) struct Formatter(RawFormatter);
impl Formatter {
/// Creates a new instance of [`Formatter`] with the given buffer.
///
/// # Safety
///
/// The memory region starting at `buf` and extending for `len` bytes must be valid for writes
/// for the lifetime of the returned [`Formatter`].
pub(crate) unsafe fn from_buffer(buf: *mut u8, len: usize) -> Self {
// SAFETY: The safety requirements of this function satisfy those of the callee.
Self(unsafe { RawFormatter::from_buffer(buf, len) })
}
}
impl Deref for Formatter {
type Target = RawFormatter;
fn deref(&self) -> &Self::Target {
&self.0
}
}
impl fmt::Write for Formatter {
fn write_str(&mut self, s: &str) -> fmt::Result {
self.0.write_str(s)?;
// Fail the request if we go past the end of the buffer.
if self.0.pos > self.0.end {
Err(fmt::Error)
} else {
Ok(())
}
}
}
/// An owned string that is guaranteed to have exactly one `NUL` byte, which is at the end.
///
/// Used for interoperability with kernel APIs that take C strings.
///
/// # Invariants
///
/// The string is always `NUL`-terminated and contains no other `NUL` bytes.
///
/// # Examples
///
/// ```
/// use kernel::{str::CString, fmt};
///
/// let s = CString::try_from_fmt(fmt!("{}{}{}", "abc", 10, 20)).unwrap();
/// assert_eq!(s.as_bytes_with_nul(), "abc1020\0".as_bytes());
///
/// let tmp = "testing";
/// let s = CString::try_from_fmt(fmt!("{tmp}{}", 123)).unwrap();
/// assert_eq!(s.as_bytes_with_nul(), "testing123\0".as_bytes());
///
/// // This fails because it has an embedded `NUL` byte.
/// let s = CString::try_from_fmt(fmt!("a\0b{}", 123));
/// assert_eq!(s.is_ok(), false);
/// ```
pub struct CString {
buf: Vec<u8>,
}
impl CString {
/// Creates an instance of [`CString`] from the given formatted arguments.
pub fn try_from_fmt(args: fmt::Arguments<'_>) -> Result<Self, Error> {
// Calculate the size needed (formatted string plus `NUL` terminator).
let mut f = RawFormatter::new();
f.write_fmt(args)?;
f.write_str("\0")?;
let size = f.bytes_written();
// Allocate a vector with the required number of bytes, and write to it.
let mut buf = <Vec<_> as VecExt<_>>::with_capacity(size, GFP_KERNEL)?;
// SAFETY: The buffer stored in `buf` is at least of size `size` and is valid for writes.
let mut f = unsafe { Formatter::from_buffer(buf.as_mut_ptr(), size) };
f.write_fmt(args)?;
f.write_str("\0")?;
// SAFETY: The number of bytes that can be written to `f` is bounded by `size`, which is
// `buf`'s capacity. The contents of the buffer have been initialised by writes to `f`.
unsafe { buf.set_len(f.bytes_written()) };
// Check that there are no `NUL` bytes before the end.
// SAFETY: The buffer is valid for read because `f.bytes_written()` is bounded by `size`
// (which the minimum buffer size) and is non-zero (we wrote at least the `NUL` terminator)
// so `f.bytes_written() - 1` doesn't underflow.
let ptr = unsafe { bindings::memchr(buf.as_ptr().cast(), 0, (f.bytes_written() - 1) as _) };
if !ptr.is_null() {
return Err(EINVAL);
}
// INVARIANT: We wrote the `NUL` terminator and checked above that no other `NUL` bytes
// exist in the buffer.
Ok(Self { buf })
}
}
impl Deref for CString {
type Target = CStr;
fn deref(&self) -> &Self::Target {
// SAFETY: The type invariants guarantee that the string is `NUL`-terminated and that no
// other `NUL` bytes exist.
unsafe { CStr::from_bytes_with_nul_unchecked(self.buf.as_slice()) }
}
}
impl DerefMut for CString {
fn deref_mut(&mut self) -> &mut Self::Target {
// SAFETY: A `CString` is always NUL-terminated and contains no other
// NUL bytes.
unsafe { CStr::from_bytes_with_nul_unchecked_mut(self.buf.as_mut_slice()) }
}
}
impl<'a> TryFrom<&'a CStr> for CString {
type Error = AllocError;
fn try_from(cstr: &'a CStr) -> Result<CString, AllocError> {
let mut buf = Vec::new();
<Vec<_> as VecExt<_>>::extend_from_slice(&mut buf, cstr.as_bytes_with_nul(), GFP_KERNEL)
.map_err(|_| AllocError)?;
// INVARIANT: The `CStr` and `CString` types have the same invariants for
// the string data, and we copied it over without changes.
Ok(CString { buf })
}
}
impl fmt::Debug for CString {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Debug::fmt(&**self, f)
}
}
/// A convenience alias for [`core::format_args`].
#[macro_export]
macro_rules! fmt {
($($f:tt)*) => ( core::format_args!($($f)*) )
}
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