Struct cstr_core::CStr [−][src]
pub struct CStr { /* fields omitted */ }
Representation of a borrowed C string.
This dynamically sized type is only safely constructed via a borrowed
version of an instance of CString
. This type can be constructed from a raw
C string as well and represents a C string borrowed from another location.
Note that this structure is not repr(C)
and is not recommended to be
placed in the signatures of FFI functions. Instead safe wrappers of FFI
functions may leverage the unsafe from_ptr
constructor to provide a safe
interface to other consumers.
Examples
Inspecting a foreign C string:
use cstr_core::CStr; use cstr_core::c_char; extern { fn my_string() -> *const c_char; } unsafe { let slice = CStr::from_ptr(my_string()); println!("string length: {}", slice.to_bytes().len()); }
Passing a Rust-originating C string:
use cstr_core::{CString, CStr}; use cstr_core::c_char; fn work(data: &CStr) { extern { fn work_with(data: *const c_char); } unsafe { work_with(data.as_ptr()) } } let s = CString::new("data data data data").unwrap(); work(&s);
Converting a foreign C string into a Rust String
:
use cstr_core::CStr; use cstr_core::c_char; extern { fn my_string() -> *const c_char; } fn my_string_safe() -> String { unsafe { CStr::from_ptr(my_string()).to_string_lossy().into_owned() } } println!("string: {}", my_string_safe());
Methods
impl CStr
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impl CStr
pub unsafe fn from_ptr<'a>(ptr: *const c_char) -> &'a CStr
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pub unsafe fn from_ptr<'a>(ptr: *const c_char) -> &'a CStr
Casts a raw C string to a safe C string wrapper.
This function will cast the provided ptr
to the CStr
wrapper which
allows inspection and interoperation of non-owned C strings. This method
is unsafe for a number of reasons:
- There is no guarantee to the validity of
ptr
. - The returned lifetime is not guaranteed to be the actual lifetime of
ptr
. - There is no guarantee that the memory pointed to by
ptr
contains a valid nul terminator byte at the end of the string. - It is not guaranteed that the memory pointed by
ptr
won't change before theCStr
has been destroyed.
Note: This operation is intended to be a 0-cost cast but it is currently implemented with an up-front calculation of the length of the string. This is not guaranteed to always be the case.
Examples
use cstr_core::CStr; use cstr_core::c_char; extern { fn my_string() -> *const c_char; } unsafe { let slice = CStr::from_ptr(my_string()); println!("string returned: {}", slice.to_str().unwrap()); }
pub fn from_bytes_with_nul(bytes: &[u8]) -> Result<&CStr, FromBytesWithNulError>
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pub fn from_bytes_with_nul(bytes: &[u8]) -> Result<&CStr, FromBytesWithNulError>
Creates a C string wrapper from a byte slice.
This function will cast the provided bytes
to a CStr
wrapper after
ensuring that it is null terminated and does not contain any interior
nul bytes.
Examples
use cstr_core::CStr; let cstr = CStr::from_bytes_with_nul(b"hello\0"); assert!(cstr.is_ok());
Creating a CStr
without a trailing nul byte is an error:
use cstr_core::CStr; let c_str = CStr::from_bytes_with_nul(b"hello"); assert!(c_str.is_err());
Creating a CStr
with an interior nul byte is an error:
use cstr_core::CStr; let c_str = CStr::from_bytes_with_nul(b"he\0llo\0"); assert!(c_str.is_err());
pub unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr
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pub unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr
Unsafely creates a C string wrapper from a byte slice.
This function will cast the provided bytes
to a CStr
wrapper without
performing any sanity checks. The provided slice must be null terminated
and not contain any interior nul bytes.
Examples
use cstr_core::{CStr, CString}; unsafe { let cstring = CString::new("hello").unwrap(); let cstr = CStr::from_bytes_with_nul_unchecked(cstring.to_bytes_with_nul()); assert_eq!(cstr, &*cstring); }
pub fn as_ptr(&self) -> *const c_char
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pub fn as_ptr(&self) -> *const c_char
Returns the inner pointer to this C string.
The returned pointer will be valid for as long as self
is and points
to a contiguous region of memory terminated with a 0 byte to represent
the end of the string.
WARNING
It is your responsibility to make sure that the underlying memory is not
freed too early. For example, the following code will cause undefined
behavior when ptr
is used inside the unsafe
block:
use cstr_core::{CString}; let ptr = CString::new("Hello").unwrap().as_ptr(); unsafe { // `ptr` is dangling *ptr; }
This happens because the pointer returned by as_ptr
does not carry any
lifetime information and the string is deallocated immediately after
the CString::new("Hello").unwrap().as_ptr()
expression is evaluated.
To fix the problem, bind the string to a local variable:
use cstr_core::{CString}; let hello = CString::new("Hello").unwrap(); let ptr = hello.as_ptr(); unsafe { // `ptr` is valid because `hello` is in scope *ptr; }
pub fn to_bytes(&self) -> &[u8]
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pub fn to_bytes(&self) -> &[u8]
Converts this C string to a byte slice.
This function will calculate the length of this string (which normally
requires a linear amount of work to be done) and then return the
resulting slice of u8
elements.
The returned slice will not contain the trailing nul that this C string has.
Note: This method is currently implemented as a constant-time cast, but it is planned to alter its definition in the future to perform the length calculation whenever this method is called.
Examples
use cstr_core::CStr; let c_str = CStr::from_bytes_with_nul(b"foo\0").unwrap(); assert_eq!(c_str.to_bytes(), b"foo");
pub fn to_bytes_with_nul(&self) -> &[u8]
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pub fn to_bytes_with_nul(&self) -> &[u8]
Converts this C string to a byte slice containing the trailing 0 byte.
This function is the equivalent of to_bytes
except that it will retain
the trailing nul instead of chopping it off.
Note: This method is currently implemented as a 0-cost cast, but it is planned to alter its definition in the future to perform the length calculation whenever this method is called.
Examples
use cstr_core::CStr; let c_str = CStr::from_bytes_with_nul(b"foo\0").unwrap(); assert_eq!(c_str.to_bytes_with_nul(), b"foo\0");
pub fn to_str(&self) -> Result<&str, Utf8Error>
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pub fn to_str(&self) -> Result<&str, Utf8Error>
Yields a &str
slice if the CStr
contains valid UTF-8.
This function will calculate the length of this string and check for
UTF-8 validity, and then return the &str
if it's valid.
Note: This method is currently implemented to check for validity after a constant-time cast, but it is planned to alter its definition in the future to perform the length calculation in addition to the UTF-8 check whenever this method is called.
Examples
use cstr_core::CStr; let c_str = CStr::from_bytes_with_nul(b"foo\0").unwrap(); assert_eq!(c_str.to_str(), Ok("foo"));
Trait Implementations
impl Hash for CStr
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impl Hash for CStr
fn hash<__H: Hasher>(&self, state: &mut __H)
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fn hash<__H: Hasher>(&self, state: &mut __H)
Feeds this value into the given [Hasher
]. Read more
fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,
1.3.0[src]
fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,
Feeds a slice of this type into the given [Hasher
]. Read more
impl Debug for CStr
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impl Debug for CStr
fn fmt(&self, f: &mut Formatter) -> Result
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fn fmt(&self, f: &mut Formatter) -> Result
Formats the value using the given formatter. Read more
impl<'a> Default for &'a CStr
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impl<'a> Default for &'a CStr
impl PartialEq for CStr
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impl PartialEq for CStr
fn eq(&self, other: &CStr) -> bool
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fn eq(&self, other: &CStr) -> bool
This method tests for self
and other
values to be equal, and is used by ==
. Read more
fn ne(&self, other: &Rhs) -> bool
1.0.0[src]
fn ne(&self, other: &Rhs) -> bool
This method tests for !=
.
impl Eq for CStr
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impl Eq for CStr
impl PartialOrd for CStr
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impl PartialOrd for CStr
fn partial_cmp(&self, other: &CStr) -> Option<Ordering>
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fn partial_cmp(&self, other: &CStr) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
fn lt(&self, other: &Rhs) -> bool
1.0.0[src]
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
fn le(&self, other: &Rhs) -> bool
1.0.0[src]
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
fn gt(&self, other: &Rhs) -> bool
1.0.0[src]
fn gt(&self, other: &Rhs) -> bool
This method tests greater than (for self
and other
) and is used by the >
operator. Read more
fn ge(&self, other: &Rhs) -> bool
1.0.0[src]
fn ge(&self, other: &Rhs) -> bool
This method tests greater than or equal to (for self
and other
) and is used by the >=
operator. Read more
impl Ord for CStr
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impl Ord for CStr
fn cmp(&self, other: &CStr) -> Ordering
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fn cmp(&self, other: &CStr) -> Ordering
This method returns an Ordering
between self
and other
. Read more
fn max(self, other: Self) -> Self
1.21.0[src]
fn max(self, other: Self) -> Self
Compares and returns the maximum of two values. Read more
fn min(self, other: Self) -> Self
1.21.0[src]
fn min(self, other: Self) -> Self
Compares and returns the minimum of two values. Read more
impl AsRef<CStr> for CStr
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impl AsRef<CStr> for CStr