Struct std::ffi::CString
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[src]
pub struct CString {
// some fields omitted
}A type representing an owned C-compatible string
This type serves the primary purpose of being able to safely generate a C-compatible string from a Rust byte slice or vector. An instance of this type is a static guarantee that the underlying bytes contain no interior 0 bytes and the final byte is 0.
A CString is created from either a byte slice or a byte vector. After
being created, a CString predominately inherits all of its methods from
the Deref implementation to [c_char]. Note that the underlying array
is represented as an array of c_char as opposed to u8. A u8 slice
can be obtained with the as_bytes method. Slices produced from a CString
do not contain the trailing nul terminator unless otherwise specified.
Examples
fn main() { use std::ffi::CString; use std::os::raw::c_char; extern { fn my_printer(s: *const c_char); } let c_to_print = CString::new("Hello, world!").unwrap(); unsafe { my_printer(c_to_print.as_ptr()); } }use std::ffi::CString; use std::os::raw::c_char; extern { fn my_printer(s: *const c_char); } let c_to_print = CString::new("Hello, world!").unwrap(); unsafe { my_printer(c_to_print.as_ptr()); }
Methods
impl CString
fn new<T: Into<Vec<u8>>>(t: T) -> Result<CString, NulError>
Creates a new C-compatible string from a container of bytes.
This method will consume the provided data and use the underlying bytes to construct a new string, ensuring that there is a trailing 0 byte.
Examples
use std::ffi::CString; use std::os::raw::c_char; extern { fn puts(s: *const c_char); } fn main() { let to_print = CString::new("Hello!").unwrap(); unsafe { puts(to_print.as_ptr()); } }use std::ffi::CString; use std::os::raw::c_char; extern { fn puts(s: *const c_char); } fn main() { let to_print = CString::new("Hello!").unwrap(); unsafe { puts(to_print.as_ptr()); } }
Errors
This function will return an error if the bytes yielded contain an internal 0 byte. The error returned will contain the bytes as well as the position of the nul byte.
unsafe fn from_vec_unchecked(v: Vec<u8>) -> CString
Creates a C-compatible string from a byte vector without checking for interior 0 bytes.
This method is equivalent to new except that no runtime assertion
is made that v contains no 0 bytes, and it requires an actual
byte vector, not anything that can be converted to one with Into.
unsafe fn from_ptr(ptr: *const c_char) -> CString
: renamed to from_raw
Retakes ownership of a CString that was transferred to C.
The only appropriate argument is a pointer obtained by calling
into_raw. The length of the string will be recalculated
using the pointer.
unsafe fn from_raw(ptr: *mut c_char) -> CString
Retakes ownership of a CString that was transferred to C.
The only appropriate argument is a pointer obtained by calling
into_raw. The length of the string will be recalculated
using the pointer.
fn into_ptr(self) -> *const c_char
: renamed to into_raw
Transfers ownership of the string to a C caller.
The pointer must be returned to Rust and reconstituted using
from_raw to be properly deallocated. Specifically, one
should not use the standard C free function to deallocate
this string.
Failure to call from_raw will lead to a memory leak.
fn into_raw(self) -> *mut c_char
Transfers ownership of the string to a C caller.
The pointer must be returned to Rust and reconstituted using
from_raw to be properly deallocated. Specifically, one
should not use the standard C free function to deallocate
this string.
Failure to call from_raw will lead to a memory leak.
fn into_string(self) -> Result<String, IntoStringError>
Converts the CString into a String if it contains valid Unicode data.
On failure, ownership of the original CString is returned.
fn into_bytes(self) -> Vec<u8>
Returns the underlying byte buffer.
The returned buffer does not contain the trailing nul separator and it is guaranteed to not have any interior nul bytes.
fn into_bytes_with_nul(self) -> Vec<u8>
Equivalent to the into_bytes function except that the returned vector
includes the trailing nul byte.
fn as_bytes(&self) -> &[u8]
Returns the contents of this CString as a slice of bytes.
The returned slice does not contain the trailing nul separator and it is guaranteed to not have any interior nul bytes.
fn as_bytes_with_nul(&self) -> &[u8]
Equivalent to the as_bytes function except that the returned slice
includes the trailing nul byte.
Methods from Deref<Target=CStr>
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.
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 0-cost cast, but it is planned to alter its definition in the future to perform the length calculation whenever this method is called.
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.
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 0-cost 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.
fn to_string_lossy(&self) -> Cow<str>
Converts a CStr into a Cow<str>.
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 as a Cow<str>, replacing any invalid UTF-8 sequences
with U+FFFD REPLACEMENT CHARACTER.
Note: This method is currently implemented to check for validity after a 0-cost 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.