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pub struct JNIString { /* private fields */ }
Expand description

Wrapper for std::ffi::CString that also takes care of encoding between UTF-8 and Java’s Modified UTF-8. As with CString , this implements Deref to &JNIStr .

Implementations §

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impl JNIString

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pub fn borrowed (&self) -> & JNIStr

Get the borrowed version of the JNIString. Equivalent to CString::borrowed .

Methods from Deref <Target = CStr > §

1.0.0 · source

pub fn as_ptr (&self) -> *const i8

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.

The type of the returned pointer is *const c_char , and whether it’s an alias for *const i8 or *const u8 is platform-specific.

WARNING

The returned pointer is read-only; writing to it (including passing it to C code that writes to it) causes undefined behavior.

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 std::ffi::CString;
// Do not do this:
let ptr = CString::new("Hello").expect("CString::new failed").as_ptr();
unsafe {
    // `ptr` is dangling
    *ptr;

This happens because the pointer returned by as_ptr does not carry any lifetime information and the CString is deallocated immediately after the CString::new("Hello").expect("CString::new failed").as_ptr() expression is evaluated. To fix the problem, bind the CString to a local variable:

use std::ffi::CString;
let hello = CString::new("Hello").expect("CString::new failed");
let ptr = hello.as_ptr();
unsafe {
    // `ptr` is valid because `hello` is in scope
    *ptr;

This way, the lifetime of the CString in hello encompasses the lifetime of ptr and the unsafe block.

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pub fn is_empty (&self) -> bool

🔬 This is a nightly-only experimental API. ( cstr_is_empty )

Returns true if self.to_bytes() has a length of 0.

Examples
#![feature(cstr_is_empty)]
use std::ffi::CStr;
let cstr = CStr::from_bytes_with_nul(b"foo\0")?;
assert!(!cstr.is_empty());
let empty_cstr = CStr::from_bytes_with_nul(b"\0")?;
assert!(empty_cstr.is_empty());
1.0.0 · source

pub fn to_bytes (&self) -> &[ u8 ]

Converts this C string to a byte slice.

The returned slice will not contain the trailing nul terminator 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 std::ffi::CStr;
let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
assert_eq!(cstr.to_bytes(), b"foo");
1.0.0 · source

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 CStr::to_bytes except that it will retain the trailing nul terminator 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 std::ffi::CStr;
let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
assert_eq!(cstr.to_bytes_with_nul(), b"foo\0");
1.4.0 · source

pub fn to_str (&self) -> Result <& str , Utf8Error >

Yields a & str slice if the CStr contains valid UTF-8.

If the contents of the CStr are valid UTF-8 data, this function will return the corresponding & str slice. Otherwise, it will return an error with details of where UTF-8 validation failed.

Examples
use std::ffi::CStr;
let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
assert_eq!(cstr.to_str(), Ok("foo"));
1.4.0 · source

pub fn to_string_lossy (&self) -> Cow <'_, str >

Converts a CStr into a Cow < str > .

If the contents of the CStr are valid UTF-8 data, this function will return a Cow :: Borrowed (& str ) with the corresponding & str slice. Otherwise, it will replace any invalid UTF-8 sequences with U+FFFD REPLACEMENT CHARACTER and return a Cow :: Owned (& str ) with the result.

Examples

Calling to_string_lossy on a CStr containing valid UTF-8:

use std::borrow::Cow;
use std::ffi::CStr;
let cstr = CStr::from_bytes_with_nul(b"Hello World\0")
                 .expect("CStr::from_bytes_with_nul failed");
assert_eq!(cstr.to_string_lossy(), Cow::Borrowed("Hello World"));

Calling to_string_lossy on a CStr containing invalid UTF-8:

use std::borrow::Cow;
use std::ffi::CStr;
let cstr = CStr::from_bytes_with_nul(b"Hello \xF0\x90\x80World\0")
                 .expect("CStr::from_bytes_with_nul failed");
assert_eq!(
    cstr.to_string_lossy(),
    Cow::Owned(String::from("Hello �World")) as Cow<'_, str>

Trait Implementations §

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impl Borrow < JNIStr > for JNIString

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fn borrow (&self) -> & JNIStr

Immutably borrows from an owned value. Read more
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impl Deref for JNIString

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type Target = JNIStr

The resulting type after dereferencing.
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fn deref (&self) -> &Self:: Target

Dereferences the value.
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impl<'local> Desc <'local, JThrowable <'local>> for JNIString

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type Output = AutoLocal <'local, JThrowable <'local>>

The type that this Desc returns.
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fn lookup (self, env: &mut JNIEnv <'local>) -> Result <Self:: Output >

Look up the concrete type from the JVM. Read more
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impl From < JNIString > for String

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fn from (other: JNIString ) -> String

Converts to this type from the input type.
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impl<T> From <T> for JNIString where T: AsRef < str >,

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fn from (other: T) -> Self

Converts to this type from the input type.

Auto Trait Implementations §

Blanket Implementations §

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impl<T> Any for T where T: 'static + ? Sized ,

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fn type_id (&self) -> TypeId

Gets the TypeId of self . Read more
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impl<T> Borrow <T> for T where T: ? Sized ,

const: unstable · source §

fn borrow (&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut <T> for T where T: ? Sized ,

const: unstable · source §

fn borrow_mut (&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From <T> for T

const: unstable · source §

fn from (t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into <U> for T where