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use libc::{c_char, size_t};
use std::fmt;
use std::marker::PhantomData;
use std::ptr::null;
use std::slice;
use std::str;
/// A read-only view on a Rust byte slice.
///
/// This is used to pass data from rustls-ffi to callback functions provided
/// by the user of the API.
/// `len` indicates the number of bytes than can be safely read.
///
/// The memory exposed is available as specified by the function
/// using this in its signature. For instance, when this is a parameter to a
/// callback, the lifetime will usually be the duration of the callback.
/// Functions that receive one of these must not dereference the data pointer
/// beyond the allowed lifetime.
#[repr(C)]
pub struct rustls_slice_bytes<'a> {
pub data: *const u8,
pub len: size_t,
phantom: PhantomData<&'a [u8]>,
}
impl<'a> Default for rustls_slice_bytes<'a> {
fn default() -> rustls_slice_bytes<'a> {
Self {
data: &[0u8; 0] as *const u8,
len: 0,
phantom: PhantomData,
}
}
}
impl<'a> From<&'a [u8]> for rustls_slice_bytes<'a> {
fn from(s: &[u8]) -> Self {
rustls_slice_bytes {
data: s.as_ptr(),
len: s.len(),
phantom: PhantomData,
}
}
}
#[test]
fn test_rustls_slice_bytes() {
let bytes = b"abcd";
let rsb: rustls_slice_bytes = bytes.as_ref().into();
unsafe {
assert_eq!(*rsb.data, b'a');
assert_eq!(*rsb.data.offset(3), b'd');
assert_eq!(rsb.len, 4);
}
}
/// A read-only view of a slice of Rust byte slices.
///
/// This is used to pass data from rustls-ffi to callback functions provided
/// by the user of the API. Because Vec and slice are not `#[repr(C)]`, we
/// provide access via a pointer to an opaque struct and an accessor method
/// that acts on that struct to get entries of type `rustls_slice_bytes`.
/// Internally, the pointee is a `&[&[u8]]`.
///
/// The memory exposed is available as specified by the function
/// using this in its signature. For instance, when this is a parameter to a
/// callback, the lifetime will usually be the duration of the callback.
/// Functions that receive one of these must not call its methods beyond the
/// allowed lifetime.
pub struct rustls_slice_slice_bytes<'a> {
pub(crate) inner: &'a [&'a [u8]],
}
/// Return the length of the outer slice. If the input pointer is NULL,
/// returns 0.
#[no_mangle]
pub extern "C" fn rustls_slice_slice_bytes_len(input: *const rustls_slice_slice_bytes) -> size_t {
match unsafe { input.as_ref() } {
Some(c) => c.inner.len(),
None => 0,
}
}
/// Retrieve the nth element from the input slice of slices.
///
/// If the input pointer is NULL, or n is greater than the length
/// of the `rustls_slice_slice_bytes`, returns rustls_slice_bytes{NULL, 0}.
#[no_mangle]
pub extern "C" fn rustls_slice_slice_bytes_get(
input: *const rustls_slice_slice_bytes,
n: size_t,
) -> rustls_slice_bytes {
let input = {
match unsafe { input.as_ref() } {
Some(c) => c,
None => {
return rustls_slice_bytes {
data: null(),
len: 0,
phantom: PhantomData,
}
}
}
};
match input.inner.get(n) {
Some(rsb) => (*rsb).into(),
None => rustls_slice_bytes {
data: null(),
len: 0,
phantom: PhantomData,
},
}
}
#[test]
fn test_rustls_slice_slice_bytes() {
let many_bytes: Vec<&[u8]> = vec![b"abcd", b"", b"xyz"];
let rssb = rustls_slice_slice_bytes { inner: &many_bytes };
assert_eq!(rustls_slice_slice_bytes_len(&rssb), 3);
assert_eq!(rustls_slice_slice_bytes_get(&rssb, 0).len, 4);
assert_eq!(rustls_slice_slice_bytes_get(&rssb, 1).len, 0);
assert_ne!(rustls_slice_slice_bytes_get(&rssb, 1).data, null());
assert_eq!(rustls_slice_slice_bytes_get(&rssb, 2).len, 3);
assert_eq!(rustls_slice_slice_bytes_get(&rssb, 3).len, 0);
assert_eq!(rustls_slice_slice_bytes_get(&rssb, 3).data, null());
unsafe {
assert_eq!(*rustls_slice_slice_bytes_get(&rssb, 0).data, b'a');
assert_eq!(*rustls_slice_slice_bytes_get(&rssb, 0).data.offset(3), b'd');
assert_eq!(*rustls_slice_slice_bytes_get(&rssb, 2).data, b'x');
assert_eq!(*rustls_slice_slice_bytes_get(&rssb, 2).data.offset(2), b'z');
}
}
/// A read-only view on a Rust `&str`.
///
/// The contents are guaranteed to be valid UTF-8.
///
/// As an additional guarantee on top of Rust's normal UTF-8 guarantee,
/// a `rustls_str` is guaranteed not to contain internal NUL bytes, so it is
/// safe to interpolate into a C string or compare using strncmp. Keep in mind
/// that it is not NUL-terminated.
///
/// The memory exposed is available as specified by the function
/// using this in its signature. For instance, when this is a parameter to a
/// callback, the lifetime will usually be the duration of the callback.
/// Functions that receive one of these must not dereference the data pointer
/// beyond the allowed lifetime.
#[repr(C)]
pub struct rustls_str<'a> {
pub data: *const c_char,
pub len: size_t,
phantom: PhantomData<&'a str>,
}
/// NulByte represents an error converting `&str` to `rustls_str` when the &str
/// contains a NUL.
#[derive(Debug)]
pub struct NulByte {}
impl<'a> TryFrom<&'a str> for rustls_str<'a> {
type Error = NulByte;
fn try_from(s: &str) -> Result<Self, Self::Error> {
if s.contains('\0') {
return Err(NulByte {});
}
Ok(rustls_str {
data: s.as_ptr() as *const c_char,
len: s.len(),
phantom: PhantomData,
})
}
}
impl<'a> Default for rustls_str<'a> {
fn default() -> rustls_str<'static> {
Self::from_str_unchecked("")
}
}
/// rustls_str represents a string that can be passed to C code.
///
/// The string should not have any internal NUL bytes and is not NUL terminated.
/// C code should not create rustls_str objects, they should only be created in Rust
/// code.
impl<'a> rustls_str<'a> {
pub fn from_str_unchecked(s: &'static str) -> rustls_str<'static> {
rustls_str {
data: s.as_ptr() as *const _,
len: s.len(),
phantom: PhantomData,
}
}
/// Change a rustls_str's lifetime to 'static.
///
/// This doesn't actually change how long the pointed-to data lives, but
/// is necessary when returning a rustls_str (as opposed to passing it
/// into a callback), because Rust can't figure out the "real" lifetime.
///
/// # Safety
///
/// The caller is responsible for requiring (usually via
/// documentation) that nothing uses the resulting rustls_str past its
/// actual validity period. The validity period is somewhat ill-defined
/// at present, but the Stacked Borrows experiment provides one definition,
/// by which a shared reference is valid until a mutable reference (to
/// the object or a parent object) is created.
pub unsafe fn into_static(self) -> rustls_str<'static> {
std::mem::transmute(self)
}
/// Change a rustls_str back to a &str.
///
/// # Safety
///
/// The caller must ensure the rustls_str data is valid utf8
pub unsafe fn to_str(&self) -> &str {
str::from_utf8_unchecked(slice::from_raw_parts(self.data as *const u8, self.len))
}
}
// If the assertion about Rust code being the only creator of rustls_str objects
// changes, you must change this Debug impl, since the assertion in it no longer
// holds.
impl<'a> fmt::Debug for rustls_str<'a> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let raw = unsafe {
// Despite the use of "unsafe", we know that this is safe because:
// - self.data is a u8, and single bytes are aligned
// - the entire memory range is a single allocated object, because
// we always build rustls_str objects from a slice (though this may
// change if we accept rustls_str objects from C code)
// - all values are properly initialized because we only init
// rustls_str objects inside of Rust code
// - not larger than isize::MAX because, again, it's coming from Rust
slice::from_raw_parts(self.data as *const u8, self.len)
};
let s = str::from_utf8(raw).unwrap_or("%!(ERROR)");
f.debug_struct("rustls_str")
.field("data", &s)
.field("len", &self.len)
.finish()
}
}
#[test]
fn test_rustls_str() {
let s = "abcd";
let rs: rustls_str = s.try_into().unwrap();
assert_eq!(rs.len, 4);
unsafe {
assert_eq!(*rs.data, 'a' as c_char);
assert_eq!(*rs.data.offset(3), 'd' as c_char);
}
let rs = unsafe { rs.to_str() };
assert_eq!(rs, s);
}
#[cfg(test)]
mod tests {
use crate::rslice::*;
#[test]
fn test_rustls_str_debug() {
let s = "abcd";
let rs: rustls_str = s.try_into().unwrap();
assert_eq!(
format!("{:?}", rs),
r#"rustls_str { data: "abcd", len: 4 }"#
);
}
}
#[test]
fn test_rustls_str_rejects_nul() {
assert!(matches!(rustls_str::try_from("\0"), Err(NulByte {})));
assert!(matches!(rustls_str::try_from("abc\0"), Err(NulByte {})));
assert!(matches!(rustls_str::try_from("ab\0cd"), Err(NulByte {})));
}
/// A read-only view of a slice of multiple Rust `&str`'s (that is, multiple
/// strings).
///
/// Like `rustls_str`, this guarantees that each string contains
/// UTF-8 and no NUL bytes. Strings are not NUL-terminated.
///
/// This is used to pass data from rustls-ffi to callback functions provided
/// by the user of the API. Because Vec and slice are not `#[repr(C)]`, we
/// can't provide a straightforward `data` and `len` structure. Instead, we
/// provide access via a pointer to an opaque struct and accessor methods.
/// Internally, the pointee is a `&[&str]`.
///
/// The memory exposed is available as specified by the function
/// using this in its signature. For instance, when this is a parameter to a
/// callback, the lifetime will usually be the duration of the callback.
/// Functions that receive one of these must not call its methods beyond the
/// allowed lifetime.
pub struct rustls_slice_str<'a> {
pub(crate) inner: &'a [&'a str],
}
/// Return the length of the outer slice.
///
/// If the input pointer is NULL, returns 0.
#[no_mangle]
pub extern "C" fn rustls_slice_str_len(input: *const rustls_slice_str) -> size_t {
unsafe {
match input.as_ref() {
Some(c) => c.inner.len(),
None => 0,
}
}
}
/// Retrieve the nth element from the input slice of `&str`s.
///
/// If the input pointer is NULL, or n is greater than the length of the
/// rustls_slice_str, returns rustls_str{NULL, 0}.
#[no_mangle]
pub extern "C" fn rustls_slice_str_get(input: *const rustls_slice_str, n: size_t) -> rustls_str {
let input: &rustls_slice_str = unsafe {
match input.as_ref() {
Some(c) => c,
None => {
return rustls_str {
data: null(),
len: 0,
phantom: PhantomData,
}
}
}
};
input
.inner
.get(n)
.and_then(|&s| s.try_into().ok())
.unwrap_or(rustls_str {
data: null(),
len: 0,
phantom: PhantomData,
})
}
#[test]
fn test_rustls_slice_str() {
let many_strings = vec!["abcd", "", "xyz"];
let rss = rustls_slice_str {
inner: &many_strings,
};
assert_eq!(rustls_slice_str_len(&rss), 3);
assert_eq!(rustls_slice_str_get(&rss, 0).len, 4);
assert_eq!(rustls_slice_str_get(&rss, 1).len, 0);
assert_ne!(rustls_slice_str_get(&rss, 1).data, null());
assert_eq!(rustls_slice_str_get(&rss, 2).len, 3);
assert_eq!(rustls_slice_str_get(&rss, 3).len, 0);
assert_eq!(rustls_slice_str_get(&rss, 3).data, null());
unsafe {
assert_eq!(*rustls_slice_str_get(&rss, 0).data, 'a' as c_char);
assert_eq!(*rustls_slice_str_get(&rss, 0).data.offset(3), 'd' as c_char);
assert_eq!(*rustls_slice_str_get(&rss, 2).data, 'x' as c_char);
assert_eq!(*rustls_slice_str_get(&rss, 2).data.offset(2), 'z' as c_char);
}
}
/// A read-only view on a Rust slice of 16-bit integers in platform endianness.
///
/// This is used to pass data from rustls-ffi to callback functions provided
/// by the user of the API.
/// `len` indicates the number of bytes than can be safely read.
///
/// The memory exposed is available as specified by the function
/// using this in its signature. For instance, when this is a parameter to a
/// callback, the lifetime will usually be the duration of the callback.
/// Functions that receive one of these must not dereference the data pointer
/// beyond the allowed lifetime.
#[repr(C)]
pub struct rustls_slice_u16<'a> {
pub data: *const u16,
pub len: size_t,
phantom: PhantomData<&'a [u16]>,
}
impl<'a> From<&'a [u16]> for rustls_slice_u16<'a> {
fn from(s: &[u16]) -> Self {
rustls_slice_u16 {
data: s.as_ptr(),
len: s.len(),
phantom: PhantomData,
}
}
}
#[test]
fn test_rustls_slice_u16() {
let u16s = vec![101, 314, 2718];
let rsu: rustls_slice_u16 = (&*u16s).into();
assert_eq!(rsu.len, 3);
unsafe {
assert_eq!(*rsu.data, 101);
assert_eq!(*rsu.data.offset(1), 314);
assert_eq!(*rsu.data.offset(2), 2718);
}
}