rust/src/librustrt/c_str.rs

// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

/*!

C-string manipulation and management

This modules provides the basic methods for creating and manipulating
null-terminated strings for use with FFI calls (back to C). Most C APIs require
that the string being passed to them is null-terminated, and by default rust's
string types are *not* null terminated.

The other problem with translating Rust strings to C strings is that Rust
strings can validly contain a null-byte in the middle of the string (0 is a
valid Unicode codepoint). This means that not all Rust strings can actually be
translated to C strings.

# Creation of a C string

A C string is managed through the `CString` type defined in this module. It
"owns" the internal buffer of characters and will automatically deallocate the
buffer when the string is dropped. The `ToCStr` trait is implemented for `&str`
and `&[u8]`, but the conversions can fail due to some of the limitations
explained above.

This also means that currently whenever a C string is created, an allocation
must be performed to place the data elsewhere (the lifetime of the C string is
not tied to the lifetime of the original string/data buffer). If C strings are
heavily used in applications, then caching may be advisable to prevent
unnecessary amounts of allocations.

Be carefull to remember that the memory is managed by C allocator API and not
by Rust allocator API.
That means that the CString pointers should be freed with C allocator API
if you intend to do that on your own, as the behaviour if you free them with
Rust's allocator API is not well defined

An example of creating and using a C string would be:

```rust
extern crate libc;

extern {
    fn puts(s: *const libc::c_char);
}

fn main() {
    let my_string = "Hello, world!";

    // Allocate the C string with an explicit local that owns the string. The
    // `c_buffer` pointer will be deallocated when `my_c_string` goes out of scope.
    let my_c_string = my_string.to_c_str();
    unsafe {
        puts(my_c_string.as_ptr());
    }

    // Don't save/return the pointer to the C string, the `c_buffer` will be
    // deallocated when this block returns!
    my_string.with_c_str(|c_buffer| {
        unsafe { puts(c_buffer); }
    });
}
```

*/

use alloc::libc_heap::malloc_raw;
use collections::string::String;
use collections::hash;
use core::fmt;
use core::kinds::marker;
use core::mem;
use core::prelude::{Clone, Collection, Drop, Eq, ImmutableSlice, Iterator};
use core::prelude::{MutableSlice, None, Option, Ordering, PartialEq};
use core::prelude::{PartialOrd, RawPtr, Some, StrSlice, range};
use core::ptr;
use core::raw::Slice;
use core::slice;
use core::str;
use libc;

/// The representation of a C String.
///
/// This structure wraps a `*libc::c_char`, and will automatically free the
/// memory it is pointing to when it goes out of scope.
pub struct CString {
    buf: *const libc::c_char,
    owns_buffer_: bool,
}

impl Clone for CString {
    /// Clone this CString into a new, uniquely owned CString. For safety
    /// reasons, this is always a deep clone with the memory allocated
    /// with C's allocator API, rather than the usual shallow clone.
    fn clone(&self) -> CString {
        let len = self.len() + 1;
        let buf = unsafe { malloc_raw(len) } as *mut libc::c_char;
        unsafe { ptr::copy_nonoverlapping_memory(buf, self.buf, len); }
        CString { buf: buf as *const libc::c_char, owns_buffer_: true }
    }
}

impl PartialEq for CString {
    fn eq(&self, other: &CString) -> bool {
        // Check if the two strings share the same buffer
        if self.buf as uint == other.buf as uint {
            true
        } else {
            unsafe {
                libc::strcmp(self.buf, other.buf) == 0
            }
        }
    }
}

impl PartialOrd for CString {
    #[inline]
    fn partial_cmp(&self, other: &CString) -> Option<Ordering> {
        self.as_bytes().partial_cmp(&other.as_bytes())
    }
}

impl Eq for CString {}

impl<S: hash::Writer> hash::Hash<S> for CString {
    #[inline]
    fn hash(&self, state: &mut S) {
        self.as_bytes().hash(state)
    }
}

impl CString {
    /// Create a C String from a pointer, with memory managed by C's allocator
    /// API, so avoid calling it with a pointer to memory managed by Rust's
    /// allocator API, as the behaviour would not be well defined.
    ///
    ///# Failure
    ///
    /// Fails if `buf` is null
    pub unsafe fn new(buf: *const libc::c_char, owns_buffer: bool) -> CString {
        assert!(!buf.is_null());
        CString { buf: buf, owns_buffer_: owns_buffer }
    }

    /// Return a pointer to the NUL-terminated string data.
    ///
    /// `.as_ptr` returns an internal pointer into the `CString`, and
    /// may be invalidated when the `CString` falls out of scope (the
    /// destructor will run, freeing the allocation if there is
    /// one).
    ///
    /// ```rust
    /// let foo = "some string";
    ///
    /// // right
    /// let x = foo.to_c_str();
    /// let p = x.as_ptr();
    ///
    /// // wrong (the CString will be freed, invalidating `p`)
    /// let p = foo.to_c_str().as_ptr();
    /// ```
    ///
    /// # Example
    ///
    /// ```rust
    /// extern crate libc;
    ///
    /// fn main() {
    ///     let c_str = "foo bar".to_c_str();
    ///     unsafe {
    ///         libc::puts(c_str.as_ptr());
    ///     }
    /// }
    /// ```
    pub fn as_ptr(&self) -> *const libc::c_char {
        self.buf
    }

    /// Return a mutable pointer to the NUL-terminated string data.
    ///
    /// `.as_mut_ptr` returns an internal pointer into the `CString`, and
    /// may be invalidated when the `CString` falls out of scope (the
    /// destructor will run, freeing the allocation if there is
    /// one).
    ///
    /// ```rust
    /// let foo = "some string";
    ///
    /// // right
    /// let mut x = foo.to_c_str();
    /// let p = x.as_mut_ptr();
    ///
    /// // wrong (the CString will be freed, invalidating `p`)
    /// let p = foo.to_c_str().as_mut_ptr();
    /// ```
    pub fn as_mut_ptr(&mut self) -> *mut libc::c_char {
        self.buf as *mut _
    }

    /// Calls a closure with a reference to the underlying `*libc::c_char`.
    #[deprecated="use `.as_ptr()`"]
    pub fn with_ref<T>(&self, f: |*const libc::c_char| -> T) -> T {
        f(self.buf)
    }

    /// Calls a closure with a mutable reference to the underlying `*libc::c_char`.
    #[deprecated="use `.as_mut_ptr()`"]
    pub fn with_mut_ref<T>(&mut self, f: |*mut libc::c_char| -> T) -> T {
        f(self.buf as *mut libc::c_char)
    }

    /// Returns true if the CString is a null.
    #[deprecated="a CString cannot be null"]
    pub fn is_null(&self) -> bool {
        self.buf.is_null()
    }

    /// Returns true if the CString is not null.
    #[deprecated="a CString cannot be null"]
    pub fn is_not_null(&self) -> bool {
        self.buf.is_not_null()
    }

    /// Returns whether or not the `CString` owns the buffer.
    pub fn owns_buffer(&self) -> bool {
        self.owns_buffer_
    }

    /// Converts the CString into a `&[u8]` without copying.
    /// Includes the terminating NUL byte.
    #[inline]
    pub fn as_bytes<'a>(&'a self) -> &'a [u8] {
        unsafe {
            mem::transmute(Slice { data: self.buf, len: self.len() + 1 })
        }
    }

    /// Converts the CString into a `&[u8]` without copying.
    /// Does not include the terminating NUL byte.
    #[inline]
    pub fn as_bytes_no_nul<'a>(&'a self) -> &'a [u8] {
        unsafe {
            mem::transmute(Slice { data: self.buf, len: self.len() })
        }
    }

    /// Converts the CString into a `&str` without copying.
    /// Returns None if the CString is not UTF-8.
    #[inline]
    pub fn as_str<'a>(&'a self) -> Option<&'a str> {
        let buf = self.as_bytes_no_nul();
        str::from_utf8(buf)
    }

    /// Return a CString iterator.
    pub fn iter<'a>(&'a self) -> CChars<'a> {
        CChars {
            ptr: self.buf,
            marker: marker::ContravariantLifetime,
        }
    }

    /// Unwraps the wrapped `*libc::c_char` from the `CString` wrapper.
    ///
    /// Any ownership of the buffer by the `CString` wrapper is
    /// forgotten, meaning that the backing allocation of this
    /// `CString` is not automatically freed if it owns the
    /// allocation. In this case, a user of `.unwrap()` should ensure
    /// the allocation is freed, to avoid leaking memory. You should
    /// use libc's memory allocator in this case.
    ///
    /// Prefer `.as_ptr()` when just retrieving a pointer to the
    /// string data, as that does not relinquish ownership.
    pub unsafe fn unwrap(mut self) -> *const libc::c_char {
        self.owns_buffer_ = false;
        self.buf
    }

}

impl Drop for CString {
    fn drop(&mut self) {
        if self.owns_buffer_ {
            unsafe {
                libc::free(self.buf as *mut libc::c_void)
            }
        }
    }
}

impl Collection for CString {
    /// Return the number of bytes in the CString (not including the NUL terminator).
    #[inline]
    fn len(&self) -> uint {
        let mut cur = self.buf;
        let mut len = 0;
        unsafe {
            while *cur != 0 {
                len += 1;
                cur = cur.offset(1);
            }
        }
        return len;
    }
}

impl fmt::Show for CString {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        String::from_utf8_lossy(self.as_bytes_no_nul()).fmt(f)
    }
}

/// A generic trait for converting a value to a CString.
pub trait ToCStr {
    /// Copy the receiver into a CString.
    ///
    /// # Failure
    ///
    /// Fails the task if the receiver has an interior null.
    fn to_c_str(&self) -> CString;

    /// Unsafe variant of `to_c_str()` that doesn't check for nulls.
    unsafe fn to_c_str_unchecked(&self) -> CString;

    /// Work with a temporary CString constructed from the receiver.
    /// The provided `*libc::c_char` will be freed immediately upon return.
    ///
    /// # Example
    ///
    /// ```rust
    /// extern crate libc;
    ///
    /// fn main() {
    ///     let s = "PATH".with_c_str(|path| unsafe {
    ///         libc::getenv(path)
    ///     });
    /// }
    /// ```
    ///
    /// # Failure
    ///
    /// Fails the task if the receiver has an interior null.
    #[inline]
    fn with_c_str<T>(&self, f: |*const libc::c_char| -> T) -> T {
        let c_str = self.to_c_str();
        f(c_str.as_ptr())
    }

    /// Unsafe variant of `with_c_str()` that doesn't check for nulls.
    #[inline]
    unsafe fn with_c_str_unchecked<T>(&self, f: |*const libc::c_char| -> T) -> T {
        let c_str = self.to_c_str_unchecked();
        f(c_str.as_ptr())
    }
}

// FIXME (#12938): Until DST lands, we cannot decompose &str into &
// and str, so we cannot usefully take ToCStr arguments by reference
// (without forcing an additional & around &str). So we are instead
// temporarily adding an instance for ~str and String, so that we can
// take ToCStr as owned. When DST lands, the string instances should
// be revisited, and arguments bound by ToCStr should be passed by
// reference.

impl<'a> ToCStr for &'a str {
    #[inline]
    fn to_c_str(&self) -> CString {
        self.as_bytes().to_c_str()
    }

    #[inline]
    unsafe fn to_c_str_unchecked(&self) -> CString {
        self.as_bytes().to_c_str_unchecked()
    }

    #[inline]
    fn with_c_str<T>(&self, f: |*const libc::c_char| -> T) -> T {
        self.as_bytes().with_c_str(f)
    }

    #[inline]
    unsafe fn with_c_str_unchecked<T>(&self, f: |*const libc::c_char| -> T) -> T {
        self.as_bytes().with_c_str_unchecked(f)
    }
}

impl ToCStr for String {
    #[inline]
    fn to_c_str(&self) -> CString {
        self.as_bytes().to_c_str()
    }

    #[inline]
    unsafe fn to_c_str_unchecked(&self) -> CString {
        self.as_bytes().to_c_str_unchecked()
    }

    #[inline]
    fn with_c_str<T>(&self, f: |*const libc::c_char| -> T) -> T {
        self.as_bytes().with_c_str(f)
    }

    #[inline]
    unsafe fn with_c_str_unchecked<T>(&self, f: |*const libc::c_char| -> T) -> T {
        self.as_bytes().with_c_str_unchecked(f)
    }
}

// The length of the stack allocated buffer for `vec.with_c_str()`
static BUF_LEN: uint = 128;

impl<'a> ToCStr for &'a [u8] {
    fn to_c_str(&self) -> CString {
        let mut cs = unsafe { self.to_c_str_unchecked() };
        check_for_null(*self, cs.as_mut_ptr());
        cs
    }

    unsafe fn to_c_str_unchecked(&self) -> CString {
        let self_len = self.len();
        let buf = malloc_raw(self_len + 1);

        ptr::copy_memory(buf, self.as_ptr(), self_len);
        *buf.offset(self_len as int) = 0;

        CString::new(buf as *const libc::c_char, true)
    }

    fn with_c_str<T>(&self, f: |*const libc::c_char| -> T) -> T {
        unsafe { with_c_str(*self, true, f) }
    }

    unsafe fn with_c_str_unchecked<T>(&self, f: |*const libc::c_char| -> T) -> T {
        with_c_str(*self, false, f)
    }
}

// Unsafe function that handles possibly copying the &[u8] into a stack array.
unsafe fn with_c_str<T>(v: &[u8], checked: bool,
                        f: |*const libc::c_char| -> T) -> T {
    let c_str = if v.len() < BUF_LEN {
        let mut buf: [u8, .. BUF_LEN] = mem::uninitialized();
        slice::bytes::copy_memory(buf, v);
        buf[v.len()] = 0;

        let buf = buf.as_mut_ptr();
        if checked {
            check_for_null(v, buf as *mut libc::c_char);
        }

        return f(buf as *const libc::c_char)
    } else if checked {
        v.to_c_str()
    } else {
        v.to_c_str_unchecked()
    };

    f(c_str.as_ptr())
}

#[inline]
fn check_for_null(v: &[u8], buf: *mut libc::c_char) {
    for i in range(0, v.len()) {
        unsafe {
            let p = buf.offset(i as int);
            assert!(*p != 0);
        }
    }
}

/// External iterator for a CString's bytes.
///
/// Use with the `std::iter` module.
pub struct CChars<'a> {
    ptr: *const libc::c_char,
    marker: marker::ContravariantLifetime<'a>,
}

impl<'a> Iterator<libc::c_char> for CChars<'a> {
    fn next(&mut self) -> Option<libc::c_char> {
        let ch = unsafe { *self.ptr };
        if ch == 0 {
            None
        } else {
            self.ptr = unsafe { self.ptr.offset(1) };
            Some(ch)
        }
    }
}

/// Parses a C "multistring", eg windows env values or
/// the req->ptr result in a uv_fs_readdir() call.
///
/// Optionally, a `count` can be passed in, limiting the
/// parsing to only being done `count`-times.
///
/// The specified closure is invoked with each string that
/// is found, and the number of strings found is returned.
pub unsafe fn from_c_multistring(buf: *const libc::c_char,
                                 count: Option<uint>,
                                 f: |&CString|) -> uint {

    let mut curr_ptr: uint = buf as uint;
    let mut ctr = 0;
    let (limited_count, limit) = match count {
        Some(limit) => (true, limit),
        None => (false, 0)
    };
    while ((limited_count && ctr < limit) || !limited_count)
          && *(curr_ptr as *const libc::c_char) != 0 as libc::c_char {
        let cstr = CString::new(curr_ptr as *const libc::c_char, false);
        f(&cstr);
        curr_ptr += cstr.len() + 1;
        ctr += 1;
    }
    return ctr;
}

#[cfg(test)]
mod tests {
    use std::prelude::*;
    use std::ptr;
    use std::task;
    use libc;

    use super::*;

    #[test]
    fn test_str_multistring_parsing() {
        unsafe {
            let input = b"zero\0one\0\0";
            let ptr = input.as_ptr();
            let expected = ["zero", "one"];
            let mut it = expected.iter();
            let result = from_c_multistring(ptr as *const libc::c_char, None, |c| {
                let cbytes = c.as_bytes_no_nul();
                assert_eq!(cbytes, it.next().unwrap().as_bytes());
            });
            assert_eq!(result, 2);
            assert!(it.next().is_none());
        }
    }

    #[test]
    fn test_str_to_c_str() {
        let c_str = "".to_c_str();
        unsafe {
            assert_eq!(*c_str.as_ptr().offset(0), 0);
        }

        let c_str = "hello".to_c_str();
        let buf = c_str.as_ptr();
        unsafe {
            assert_eq!(*buf.offset(0), 'h' as libc::c_char);
            assert_eq!(*buf.offset(1), 'e' as libc::c_char);
            assert_eq!(*buf.offset(2), 'l' as libc::c_char);
            assert_eq!(*buf.offset(3), 'l' as libc::c_char);
            assert_eq!(*buf.offset(4), 'o' as libc::c_char);
            assert_eq!(*buf.offset(5), 0);
        }
    }

    #[test]
    fn test_vec_to_c_str() {
        let b: &[u8] = [];
        let c_str = b.to_c_str();
        unsafe {
            assert_eq!(*c_str.as_ptr().offset(0), 0);
        }

        let c_str = b"hello".to_c_str();
        let buf = c_str.as_ptr();
        unsafe {
            assert_eq!(*buf.offset(0), 'h' as libc::c_char);
            assert_eq!(*buf.offset(1), 'e' as libc::c_char);
            assert_eq!(*buf.offset(2), 'l' as libc::c_char);
            assert_eq!(*buf.offset(3), 'l' as libc::c_char);
            assert_eq!(*buf.offset(4), 'o' as libc::c_char);
            assert_eq!(*buf.offset(5), 0);
        }

        let c_str = b"foo\xFF".to_c_str();
        let buf = c_str.as_ptr();
        unsafe {
            assert_eq!(*buf.offset(0), 'f' as libc::c_char);
            assert_eq!(*buf.offset(1), 'o' as libc::c_char);
            assert_eq!(*buf.offset(2), 'o' as libc::c_char);
            assert_eq!(*buf.offset(3), 0xffu8 as i8);
            assert_eq!(*buf.offset(4), 0);
        }
    }

    #[test]
    fn test_unwrap() {
        let c_str = "hello".to_c_str();
        unsafe { libc::free(c_str.unwrap() as *mut libc::c_void) }
    }

    #[test]
    fn test_as_ptr() {
        let c_str = "hello".to_c_str();
        let len = unsafe { libc::strlen(c_str.as_ptr()) };
        assert_eq!(len, 5);
    }

    #[test]
    fn test_iterator() {
        let c_str = "".to_c_str();
        let mut iter = c_str.iter();
        assert_eq!(iter.next(), None);

        let c_str = "hello".to_c_str();
        let mut iter = c_str.iter();
        assert_eq!(iter.next(), Some('h' as libc::c_char));
        assert_eq!(iter.next(), Some('e' as libc::c_char));
        assert_eq!(iter.next(), Some('l' as libc::c_char));
        assert_eq!(iter.next(), Some('l' as libc::c_char));
        assert_eq!(iter.next(), Some('o' as libc::c_char));
        assert_eq!(iter.next(), None);
    }

    #[test]
    fn test_to_c_str_fail() {
        assert!(task::try(proc() { "he\x00llo".to_c_str() }).is_err());
    }

    #[test]
    fn test_to_c_str_unchecked() {
        unsafe {
            let c_string = "he\x00llo".to_c_str_unchecked();
            let buf = c_string.as_ptr();
            assert_eq!(*buf.offset(0), 'h' as libc::c_char);
            assert_eq!(*buf.offset(1), 'e' as libc::c_char);
            assert_eq!(*buf.offset(2), 0);
            assert_eq!(*buf.offset(3), 'l' as libc::c_char);
            assert_eq!(*buf.offset(4), 'l' as libc::c_char);
            assert_eq!(*buf.offset(5), 'o' as libc::c_char);
            assert_eq!(*buf.offset(6), 0);
        }
    }

    #[test]
    fn test_as_bytes() {
        let c_str = "hello".to_c_str();
        assert_eq!(c_str.as_bytes(), b"hello\0");
        let c_str = "".to_c_str();
        assert_eq!(c_str.as_bytes(), b"\0");
        let c_str = b"foo\xFF".to_c_str();
        assert_eq!(c_str.as_bytes(), b"foo\xFF\0");
    }

    #[test]
    fn test_as_bytes_no_nul() {
        let c_str = "hello".to_c_str();
        assert_eq!(c_str.as_bytes_no_nul(), b"hello");
        let c_str = "".to_c_str();
        let exp: &[u8] = [];
        assert_eq!(c_str.as_bytes_no_nul(), exp);
        let c_str = b"foo\xFF".to_c_str();
        assert_eq!(c_str.as_bytes_no_nul(), b"foo\xFF");
    }

    #[test]
    fn test_as_str() {
        let c_str = "hello".to_c_str();
        assert_eq!(c_str.as_str(), Some("hello"));
        let c_str = "".to_c_str();
        assert_eq!(c_str.as_str(), Some(""));
        let c_str = b"foo\xFF".to_c_str();
        assert_eq!(c_str.as_str(), None);
    }

    #[test]
    #[should_fail]
    fn test_new_fail() {
        let _c_str = unsafe { CString::new(ptr::null(), false) };
    }

    #[test]
    fn test_clone() {
        let a = "hello".to_c_str();
        let b = a.clone();
        assert!(a == b);
    }

    #[test]
    fn test_clone_noleak() {
        fn foo(f: |c: &CString|) {
            let s = "test".to_string();
            let c = s.to_c_str();
            // give the closure a non-owned CString
            let mut c_ = unsafe { CString::new(c.as_ptr(), false) };
            f(&c_);
            // muck with the buffer for later printing
            unsafe { *c_.as_mut_ptr() = 'X' as libc::c_char }
        }

        let mut c_: Option<CString> = None;
        foo(|c| {
            c_ = Some(c.clone());
            c.clone();
            // force a copy, reading the memory
            c.as_bytes().to_vec();
        });
        let c_ = c_.unwrap();
        // force a copy, reading the memory
        c_.as_bytes().to_vec();
    }
}

#[cfg(test)]
mod bench {
    use test::Bencher;
    use libc;
    use std::prelude::*;

    #[inline]
    fn check(s: &str, c_str: *const libc::c_char) {
        let s_buf = s.as_ptr();
        for i in range(0, s.len()) {
            unsafe {
                assert_eq!(
                    *s_buf.offset(i as int) as libc::c_char,
                    *c_str.offset(i as int));
            }
        }
    }

    static S_SHORT: &'static str = "Mary";
    static S_MEDIUM: &'static str = "Mary had a little lamb";
    static S_LONG: &'static str = "\
        Mary had a little lamb, Little lamb
        Mary had a little lamb, Little lamb
        Mary had a little lamb, Little lamb
        Mary had a little lamb, Little lamb
        Mary had a little lamb, Little lamb
        Mary had a little lamb, Little lamb";

    fn bench_to_string(b: &mut Bencher, s: &str) {
        b.iter(|| {
            let c_str = s.to_c_str();
            check(s, c_str.as_ptr());
        })
    }

    #[bench]
    fn bench_to_c_str_short(b: &mut Bencher) {
        bench_to_string(b, S_SHORT)
    }

    #[bench]
    fn bench_to_c_str_medium(b: &mut Bencher) {
        bench_to_string(b, S_MEDIUM)
    }

    #[bench]
    fn bench_to_c_str_long(b: &mut Bencher) {
        bench_to_string(b, S_LONG)
    }

    fn bench_to_c_str_unchecked(b: &mut Bencher, s: &str) {
        b.iter(|| {
            let c_str = unsafe { s.to_c_str_unchecked() };
            check(s, c_str.as_ptr())
        })
    }

    #[bench]
    fn bench_to_c_str_unchecked_short(b: &mut Bencher) {
        bench_to_c_str_unchecked(b, S_SHORT)
    }

    #[bench]
    fn bench_to_c_str_unchecked_medium(b: &mut Bencher) {
        bench_to_c_str_unchecked(b, S_MEDIUM)
    }

    #[bench]
    fn bench_to_c_str_unchecked_long(b: &mut Bencher) {
        bench_to_c_str_unchecked(b, S_LONG)
    }

    fn bench_with_c_str(b: &mut Bencher, s: &str) {
        b.iter(|| {
            s.with_c_str(|c_str_buf| check(s, c_str_buf))
        })
    }

    #[bench]
    fn bench_with_c_str_short(b: &mut Bencher) {
        bench_with_c_str(b, S_SHORT)
    }

    #[bench]
    fn bench_with_c_str_medium(b: &mut Bencher) {
        bench_with_c_str(b, S_MEDIUM)
    }

    #[bench]
    fn bench_with_c_str_long(b: &mut Bencher) {
        bench_with_c_str(b, S_LONG)
    }

    fn bench_with_c_str_unchecked(b: &mut Bencher, s: &str) {
        b.iter(|| {
            unsafe {
                s.with_c_str_unchecked(|c_str_buf| check(s, c_str_buf))
            }
        })
    }

    #[bench]
    fn bench_with_c_str_unchecked_short(b: &mut Bencher) {
        bench_with_c_str_unchecked(b, S_SHORT)
    }

    #[bench]
    fn bench_with_c_str_unchecked_medium(b: &mut Bencher) {
        bench_with_c_str_unchecked(b, S_MEDIUM)
    }

    #[bench]
    fn bench_with_c_str_unchecked_long(b: &mut Bencher) {
        bench_with_c_str_unchecked(b, S_LONG)
    }
}