always implement traits for C type

This commit is contained in:
Dustin J. Mitchell 2022-02-06 23:05:33 +00:00
parent 1e585ba0d9
commit e11506ee6a
8 changed files with 60 additions and 59 deletions

View file

@ -3,37 +3,37 @@ use crate::traits::*;
use crate::util::{drop_pointer_array, vec_into_raw_parts};
use std::ptr::NonNull;
/// TCStrings represents a list of string.
/// TCStrings represents a list of strings.
///
/// The content of this struct must be treated as read-only.
#[repr(C)]
pub struct TCStrings {
/// number of tags in items
/// number of strings in items
len: libc::size_t,
/// total size of items (internal use only)
_capacity: libc::size_t,
/// strings representing each tag. these remain owned by the TCStrings instance and will be freed
/// strings representing each string. these remain owned by the TCStrings instance and will be freed
/// by tc_strings_free.
items: *const NonNull<TCString<'static>>,
}
impl PassByValue for Vec<NonNull<TCString<'static>>> {
type CType = TCStrings;
impl PassByValue for TCStrings {
type RustType = Vec<NonNull<TCString<'static>>>;
unsafe fn from_ctype(arg: TCStrings) -> Self {
unsafe fn from_ctype(self) -> Self::RustType {
// SAFETY:
// - C treats TCStrings as read-only, so items, len, and _capacity all came
// from a Vec originally.
unsafe { Vec::from_raw_parts(arg.items as *mut _, arg.len, arg._capacity) }
unsafe { Vec::from_raw_parts(self.items as *mut _, self.len, self._capacity) }
}
fn as_ctype(self) -> TCStrings {
fn as_ctype(arg: Self::RustType) -> Self {
// emulate Vec::into_raw_parts():
// - disable dropping the Vec with ManuallyDrop
// - extract ptr, len, and capacity using those methods
let (items, len, _capacity) = vec_into_raw_parts(self);
let (items, len, _capacity) = vec_into_raw_parts(arg);
TCStrings {
len,
_capacity,
@ -55,10 +55,10 @@ impl Default for TCStrings {
/// Free a TCStrings instance. The instance, and all TCStrings it contains, must not be used after
/// this call.
#[no_mangle]
pub extern "C" fn tc_strings_free<'a>(tctags: *mut TCStrings) {
debug_assert!(!tctags.is_null());
pub extern "C" fn tc_strings_free<'a>(tcstrings: *mut TCStrings) {
debug_assert!(!tcstrings.is_null());
// SAFETY:
// - *tctags is a valid TCStrings (caller promises to treat it as read-only)
let tags = unsafe { Vec::take_from_arg(tctags, TCStrings::default()) };
drop_pointer_array(tags);
// - *tcstrings is a valid TCStrings (caller promises to treat it as read-only)
let strings = unsafe { TCStrings::take_from_arg(tcstrings, TCStrings::default()) };
drop_pointer_array(strings);
}