Struct llvm_plugin_inkwell::support::LLVMString

source ·

pub struct LLVMString { /* private fields */ }

Expand description

An owned LLVM String. Also known as a LLVM Message

Implementations§

source §

impl LLVMString

source

pub fn to_string(&self) -> String

This is a convenience method for creating a Rust String, however; it will reallocate. LLVMString should be used as much as possible to save memory since it is allocated by LLVM. It’s essentially a CString with a custom LLVM deallocator

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.

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;

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>
);