From 42afefa09b30bff7699275ee5ccb33b79c54d90c Mon Sep 17 00:00:00 2001
From: Sky <sky@sky9.dev>
Date: Sun, 31 Dec 2023 00:02:08 -0500
Subject: [PATCH 1/2] Initial implementation of `str::from_raw_parts[_mut]`

---
 library/core/src/str/converts.rs | 40 +++++++++++++++++++++++++++++++-
 library/core/src/str/mod.rs      |  3 +++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/library/core/src/str/converts.rs b/library/core/src/str/converts.rs
index 0f23cf7ae239f..ba282f09d2067 100644
--- a/library/core/src/str/converts.rs
+++ b/library/core/src/str/converts.rs
@@ -1,6 +1,6 @@
 //! Ways to create a `str` from bytes slice.
 
-use crate::mem;
+use crate::{mem, ptr};
 
 use super::validations::run_utf8_validation;
 use super::Utf8Error;
@@ -205,3 +205,41 @@ pub const unsafe fn from_utf8_unchecked_mut(v: &mut [u8]) -> &mut str {
     // comes from a reference which is guaranteed to be valid for writes.
     unsafe { &mut *(v as *mut [u8] as *mut str) }
 }
+
+/// Creates an `&str` from a pointer and a length.
+///
+/// The pointed-to bytes must be valid UTF-8.
+/// If this might not be the case, use `str::from_utf8(slice::from_raw_parts(ptr, len))`,
+/// which will return an `Err` if the data isn't valid UTF-8.
+///
+/// This function is the `str` equivalent of [`slice::from_raw_parts`](crate::slice::from_raw_parts).
+/// See that function's documentation for safety concerns and examples.
+///
+/// The mutable version of this function is [`from_raw_parts_mut`].
+#[inline]
+#[must_use]
+#[unstable(feature = "str_from_raw_parts", issue = "119206")]
+#[rustc_const_unstable(feature = "str_from_raw_parts", issue = "119206")]
+pub const unsafe fn from_raw_parts<'a>(ptr: *const u8, len: usize) -> &'a str {
+    // SAFETY: the caller must uphold the safety contract for `from_raw_parts`.
+    unsafe { &*ptr::from_raw_parts(ptr.cast(), len) }
+}
+
+/// Creates an `&mut str` from a pointer and a length.
+///
+/// The pointed-to bytes must be valid UTF-8.
+/// If this might not be the case, use `str::from_utf8_mut(slice::from_raw_parts_mut(ptr, len))`,
+/// which will return an `Err` if the data isn't valid UTF-8.
+///
+/// This function is the `str` equivalent of [`slice::from_raw_parts_mut`](crate::slice::from_raw_parts_mut).
+/// See that function's documentation for safety concerns and examples.
+///
+/// The immutable version of this function is [`from_raw_parts`].
+#[inline]
+#[must_use]
+#[unstable(feature = "str_from_raw_parts", issue = "119206")]
+#[rustc_const_unstable(feature = "const_str_from_raw_parts_mut", issue = "119206")]
+pub const unsafe fn from_raw_parts_mut<'a>(ptr: *mut u8, len: usize) -> &'a str {
+    // SAFETY: the caller must uphold the safety contract for `from_raw_parts_mut`.
+    unsafe { &mut *ptr::from_raw_parts_mut(ptr.cast(), len) }
+}
diff --git a/library/core/src/str/mod.rs b/library/core/src/str/mod.rs
index a22c46edce254..2981d1206dd59 100644
--- a/library/core/src/str/mod.rs
+++ b/library/core/src/str/mod.rs
@@ -33,6 +33,9 @@ pub use converts::{from_utf8, from_utf8_unchecked};
 #[stable(feature = "str_mut_extras", since = "1.20.0")]
 pub use converts::{from_utf8_mut, from_utf8_unchecked_mut};
 
+#[unstable(feature = "str_from_raw_parts", issue = "119206")]
+pub use converts::{from_raw_parts, from_raw_parts_mut};
+
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use error::{ParseBoolError, Utf8Error};
 

From f94a94227cad840e45b11f5a537748b626737c6c Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Thu, 25 Jan 2024 18:11:54 -0800
Subject: [PATCH 2/2] Export core::str::from_raw_parts{,_mut} into alloc::str
 and std::str

---
 library/alloc/src/str.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/library/alloc/src/str.rs b/library/alloc/src/str.rs
index 38f9f39fbf89a..ade114678b7f9 100644
--- a/library/alloc/src/str.rs
+++ b/library/alloc/src/str.rs
@@ -30,6 +30,8 @@ pub use core::str::SplitAsciiWhitespace;
 pub use core::str::SplitInclusive;
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::str::SplitWhitespace;
+#[unstable(feature = "str_from_raw_parts", issue = "119206")]
+pub use core::str::{from_raw_parts, from_raw_parts_mut};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::str::{from_utf8, from_utf8_mut, Bytes, CharIndices, Chars};
 #[stable(feature = "rust1", since = "1.0.0")]