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Diffstat (limited to 'xpcom/rust/nsstring/src')
| -rw-r--r-- | xpcom/rust/nsstring/src/lib.rs | 853 |
1 files changed, 853 insertions, 0 deletions
diff --git a/xpcom/rust/nsstring/src/lib.rs b/xpcom/rust/nsstring/src/lib.rs new file mode 100644 index 000000000..cd518f3c5 --- /dev/null +++ b/xpcom/rust/nsstring/src/lib.rs @@ -0,0 +1,853 @@ +//! This module provides rust bindings for the XPCOM string types. +//! +//! # TL;DR (what types should I use) +//! +//! Use `&{mut,} nsA[C]String` for functions in rust which wish to take or +//! mutate XPCOM strings. The other string types `Deref` to this type. +//! +//! Use `ns[C]String<'a>` for string struct members which don't leave rust, and +//! as an intermediate between rust string data structures (such as `String`, +//! `Vec<u16>`, `&str`, and `&[u16]`) and `&{mut,} nsA[C]String` (using +//! `ns[C]String::from(value)`). These conversions, when possible, will not +//! perform any allocations. +//! +//! Use `nsFixed[C]String` or `ns_auto_[c]string!` for dynamic stack allocated +//! strings which are expected to hold short string values. +//! +//! Use `*{const,mut} nsA[C]String` (`{const,} nsA[C]String*` in C++) for +//! function arguments passed across the rust/C++ language boundary. +//! +//! Use `ns[C]StringRepr` for string struct members which are shared between +//! rust and C++, but be careful, because this type lacks a `Drop` +//! implementation. +//! +//! # String Types +//! +//! ## `nsA[C]String` +//! +//! The core types in this module are `nsAString` and `nsACString`. These types +//! are zero-sized as far as rust is concerned, and are safe to pass around +//! behind both references (in rust code), and pointers (in C++ code). They +//! represent a handle to a XPCOM string which holds either `u16` or `u8` +//! characters respectively. The backing character buffer is guaranteed to live +//! as long as the reference to the `nsAString` or `nsACString`. +//! +//! These types in rust are simply used as dummy types. References to them +//! represent a pointer to the beginning of a variable-sized `#[repr(C)]` struct +//! which is common between both C++ and Rust implementations. In C++, their +//! corresponding types are also named `nsAString` or `nsACString`, and they are +//! defined within the `nsTSubstring.{cpp,h}` file. +//! +//! ### Valid Operations +//! +//! An `&nsA[C]String` acts like rust's `&str`, in that it is a borrowed +//! reference to the backing data. When used as an argument to other functions +//! on `&mut nsA[C]String`, optimizations can be performed to avoid copying +//! buffers, as information about the backing storage is preserved. +//! +//! An `&mut nsA[C]String` acts like rust's `&mut Cow<str>`, in that it is a +//! mutable reference to a potentially borrowed string, which when modified will +//! ensure that it owns its own backing storage. This type can be appended to +//! with the methods `.append`, `.append_utf{8,16}`, and with the `write!` +//! macro, and can be assigned to with `.assign`. +//! +//! ## `ns[C]String<'a>` +//! +//! This type is an maybe-owned string type. It acts similarially to a +//! `Cow<[{u8,u16}]>`. This type provides `Deref` and `DerefMut` implementations +//! to `nsA[C]String`, which provides the methods for manipulating this type. +//! This type's lifetime parameter, `'a`, represents the lifetime of the backing +//! storage. When modified this type may re-allocate in order to ensure that it +//! does not mutate its backing storage. +//! +//! `ns[C]String`s can be constructed either with `ns[C]String::new()`, which +//! creates an empty `ns[C]String<'static>`, or through one of the provided +//! `From` implementations. Both string types may be constructed `From<&'a +//! str>`, with `nsCString` having a `'a` lifetime, as the storage is shared +//! with the `str`, while `nsString` has a `'static` lifetime, as its storage +//! has to be transcoded. +//! +//! When passing this type by reference, prefer passing a `&nsA[C]String` or +//! `&mut nsA[C]String`. to passing this type. +//! +//! This type is _not_ `#[repr(C)]`, as it has a `Drop` impl, which in versions +//! of `rustc < 1.13` adds drop flags to the struct, which messes up the layout, +//! making it unsafe to pass across the FFI boundary. The rust compiler will +//! warn if this type appears in `extern "C"` function definitions. +//! +//! When passing this type across the language boundary, pass it as `*const +//! nsA[C]String` for an immutable reference, or `*mut nsA[C]String` for a +//! mutable reference. +//! +//! This type is similar to the C++ type of the same name. +//! +//! ## `nsFixed[C]String<'a>` +//! +//! This type is a string type with fixed backing storage. It is created with +//! `nsFixed[C]String::new(buffer)`, passing a mutable reference to a buffer as +//! the argument. This buffer will be used as backing storage whenever the +//! resulting string will fit within it, falling back to heap allocations only +//! when the string size exceeds that of the backing buffer. +//! +//! Like `ns[C]String`, this type dereferences to `nsA[C]String` which provides +//! the methods for manipulating the type, and is not `#[repr(C)]`. +//! +//! When passing this type by reference, prefer passing a `&nsA[C]String` or +//! `&mut nsA[C]String`. to passing this type. +//! +//! This type is _not_ `#[repr(C)]`, as it has a `Drop` impl, which in versions +//! of `rustc < 1.13` adds drop flags to the struct, which messes up the layout, +//! making it unsafe to pass across the FFI boundary. The rust compiler will +//! warn if this type appears in `extern "C"` function definitions. +//! +//! When passing this type across the language boundary, pass it as `*const +//! nsA[C]String` for an immutable reference, or `*mut nsA[C]String` for a +//! mutable reference. +//! +//! This type is similar to the C++ type of the same name. +//! +//! ## `ns_auto_[c]string!($name)` +//! +//! This is a helper macro which defines a fixed size, (currently 64 character), +//! backing array on the stack, and defines a local variable with name `$name` +//! which is a `nsFixed[C]String` using this buffer as its backing storage. +//! +//! Usage of this macro is similar to the C++ type `nsAuto[C]String`, but could +//! not be implemented as a basic type due to the differences between rust and +//! C++'s move semantics. +//! +//! ## `ns[C]StringRepr` +//! +//! This type represents a C++ `ns[C]String`. This type is `#[repr(C)]` and is +//! safe to use in struct definitions which are shared across the language +//! boundary. It automatically dereferences to `&{mut,} nsA[C]String`, and thus +//! can be treated similarially to `ns[C]String`. +//! +//! If this type is dropped in rust, it will not free its backing storage. This +//! is because types implementing `Drop` have a drop flag added, which messes up +//! the layout of this type. When drop flags are removed, which should happen in +//! `rustc 1.13` (see rust-lang/rust#35764), this type will likely be removed, +//! and replaced with direct usage of `ns[C]String<'a>`, as its layout may be +//! identical. This module provides rust bindings to our xpcom ns[C]String +//! types. + +#![allow(non_camel_case_types)] + +use std::ops::{Deref, DerefMut}; +use std::marker::PhantomData; +use std::slice; +use std::ptr; +use std::mem; +use std::fmt; +use std::cmp; +use std::str; +use std::u32; + +////////////////////////////////// +// Internal Implemenation Flags // +////////////////////////////////// + +const F_NONE: u32 = 0; // no flags + +// data flags are in the lower 16-bits +const F_TERMINATED: u32 = 1 << 0; // IsTerminated returns true +const F_VOIDED: u32 = 1 << 1; // IsVoid returns true +const F_SHARED: u32 = 1 << 2; // mData points to a heap-allocated, shared buffer +const F_OWNED: u32 = 1 << 3; // mData points to a heap-allocated, raw buffer +const F_FIXED: u32 = 1 << 4; // mData points to a fixed-size writable, dependent buffer +const F_LITERAL: u32 = 1 << 5; // mData points to a string literal; F_TERMINATED will also be set + +// class flags are in the upper 16-bits +const F_CLASS_FIXED: u32 = 1 << 16; // indicates that |this| is of type nsTFixedString + +//////////////////////////////////// +// Generic String Bindings Macros // +//////////////////////////////////// + +macro_rules! define_string_types { + { + char_t = $char_t: ty; + AString = $AString: ident; + String = $String: ident; + FixedString = $FixedString: ident; + + StringRepr = $StringRepr: ident; + FixedStringRepr = $FixedStringRepr: ident; + AutoStringRepr = $AutoStringRepr: ident; + } => { + /// The representation of a ns[C]String type in C++. This type is + /// used internally by our definition of ns[C]String to ensure layout + /// compatibility with the C++ ns[C]String type. + /// + /// This type may also be used in place of a C++ ns[C]String inside of + /// struct definitions which are shared with C++, as it has identical + /// layout to our ns[C]String type. Due to drop flags, our ns[C]String + /// type does not have identical layout. When drop flags are removed, + /// this type will likely be made a private implementation detail, and + /// its uses will be replaced with `ns[C]String`. + /// + /// This struct will leak its data if dropped from rust. See the module + /// documentation for more information on this type. + #[repr(C)] + pub struct $StringRepr { + data: *const $char_t, + length: u32, + flags: u32, + } + + impl Deref for $StringRepr { + type Target = $AString; + fn deref(&self) -> &$AString { + unsafe { + mem::transmute(self) + } + } + } + + impl DerefMut for $StringRepr { + fn deref_mut(&mut self) -> &mut $AString { + unsafe { + mem::transmute(self) + } + } + } + + /// The representation of a nsFixed[C]String type in C++. This type is + /// used internally by our definition of nsFixed[C]String to ensure layout + /// compatibility with the C++ nsFixed[C]String type. + #[repr(C)] + struct $FixedStringRepr { + base: $StringRepr, + capacity: u32, + buffer: *mut $char_t, + } + + /// This type is the abstract type which is used for interacting with + /// strings in rust. Each string type can derefence to an instance of + /// this type, which provides the useful operations on strings. + /// + /// NOTE: Rust thinks this type has a size of 0, because the data + /// associated with it is not necessarially safe to move. It is not safe + /// to construct a nsAString yourself, unless it is received by + /// dereferencing one of these types. + /// + /// NOTE: The `[u8; 0]` member is zero sized, and only exists to prevent + /// the construction by code outside of this module. It is used instead + /// of a private `()` member because the `improper_ctypes` lint complains + /// about some ZST members in `extern "C"` function declarations. + #[repr(C)] + pub struct $AString { + _prohibit_constructor: [u8; 0], + } + + impl Deref for $AString { + type Target = [$char_t]; + fn deref(&self) -> &[$char_t] { + unsafe { + // This is legal, as all $AString values actually point to a + // $StringRepr + let this: &$StringRepr = mem::transmute(self); + if this.data.is_null() { + debug_assert!(this.length == 0); + // Use an arbitrary non-null value as the pointer + slice::from_raw_parts(0x1 as *const $char_t, 0) + } else { + slice::from_raw_parts(this.data, this.length as usize) + } + } + } + } + + impl cmp::PartialEq for $AString { + fn eq(&self, other: &$AString) -> bool { + &self[..] == &other[..] + } + } + + impl cmp::PartialEq<[$char_t]> for $AString { + fn eq(&self, other: &[$char_t]) -> bool { + &self[..] == other + } + } + + impl<'a> cmp::PartialEq<$String<'a>> for $AString { + fn eq(&self, other: &$String<'a>) -> bool { + self.eq(&**other) + } + } + + impl<'a> cmp::PartialEq<$FixedString<'a>> for $AString { + fn eq(&self, other: &$FixedString<'a>) -> bool { + self.eq(&**other) + } + } + + pub struct $String<'a> { + hdr: $StringRepr, + _marker: PhantomData<&'a [$char_t]>, + } + + impl $String<'static> { + pub fn new() -> $String<'static> { + $String { + hdr: $StringRepr { + data: ptr::null(), + length: 0, + flags: F_NONE, + }, + _marker: PhantomData, + } + } + } + + impl<'a> Deref for $String<'a> { + type Target = $AString; + fn deref(&self) -> &$AString { + &self.hdr + } + } + + impl<'a> DerefMut for $String<'a> { + fn deref_mut(&mut self) -> &mut $AString { + &mut self.hdr + } + } + + impl<'a> From<&'a String> for $String<'a> { + fn from(s: &'a String) -> $String<'a> { + $String::from(&s[..]) + } + } + + impl<'a> From<&'a Vec<$char_t>> for $String<'a> { + fn from(s: &'a Vec<$char_t>) -> $String<'a> { + $String::from(&s[..]) + } + } + + impl<'a> From<&'a [$char_t]> for $String<'a> { + fn from(s: &'a [$char_t]) -> $String<'a> { + assert!(s.len() < (u32::MAX as usize)); + $String { + hdr: $StringRepr { + data: s.as_ptr(), + length: s.len() as u32, + flags: F_NONE, + }, + _marker: PhantomData, + } + } + } + + impl From<Box<[$char_t]>> for $String<'static> { + fn from(s: Box<[$char_t]>) -> $String<'static> { + assert!(s.len() < (u32::MAX as usize)); + // SAFETY NOTE: This method produces an F_OWNED ns[C]String from + // a Box<[$char_t]>. this is only safe because in the Gecko + // tree, we use the same allocator for Rust code as for C++ + // code, meaning that our box can be legally freed with + // libc::free(). + let length = s.len() as u32; + let ptr = s.as_ptr(); + mem::forget(s); + $String { + hdr: $StringRepr { + data: ptr, + length: length, + flags: F_OWNED, + }, + _marker: PhantomData, + } + } + } + + impl From<Vec<$char_t>> for $String<'static> { + fn from(s: Vec<$char_t>) -> $String<'static> { + s.into_boxed_slice().into() + } + } + + impl<'a> From<&'a $AString> for $String<'static> { + fn from(s: &'a $AString) -> $String<'static> { + let mut string = $String::new(); + string.assign(s); + string + } + } + + impl<'a> fmt::Write for $String<'a> { + fn write_str(&mut self, s: &str) -> Result<(), fmt::Error> { + $AString::write_str(self, s) + } + } + + impl<'a> fmt::Display for $String<'a> { + fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { + <$AString as fmt::Display>::fmt(self, f) + } + } + + impl<'a> fmt::Debug for $String<'a> { + fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { + <$AString as fmt::Debug>::fmt(self, f) + } + } + + impl<'a> cmp::PartialEq for $String<'a> { + fn eq(&self, other: &$String<'a>) -> bool { + $AString::eq(self, other) + } + } + + impl<'a> cmp::PartialEq<[$char_t]> for $String<'a> { + fn eq(&self, other: &[$char_t]) -> bool { + $AString::eq(self, other) + } + } + + impl<'a, 'b> cmp::PartialEq<&'b [$char_t]> for $String<'a> { + fn eq(&self, other: &&'b [$char_t]) -> bool { + $AString::eq(self, *other) + } + } + + impl<'a> cmp::PartialEq<str> for $String<'a> { + fn eq(&self, other: &str) -> bool { + $AString::eq(self, other) + } + } + + impl<'a, 'b> cmp::PartialEq<&'b str> for $String<'a> { + fn eq(&self, other: &&'b str) -> bool { + $AString::eq(self, *other) + } + } + + impl<'a> Drop for $String<'a> { + fn drop(&mut self) { + unsafe { + self.finalize(); + } + } + } + + /// A nsFixed[C]String is a string which uses a fixed size mutable + /// backing buffer for storing strings which will fit within that + /// buffer, rather than using heap allocations. + pub struct $FixedString<'a> { + hdr: $FixedStringRepr, + _marker: PhantomData<&'a mut [$char_t]>, + } + + impl<'a> $FixedString<'a> { + pub fn new(buf: &'a mut [$char_t]) -> $FixedString<'a> { + let len = buf.len(); + assert!(len < (u32::MAX as usize)); + let buf_ptr = buf.as_mut_ptr(); + $FixedString { + hdr: $FixedStringRepr { + base: $StringRepr { + data: ptr::null(), + length: 0, + flags: F_CLASS_FIXED, + }, + capacity: len as u32, + buffer: buf_ptr, + }, + _marker: PhantomData, + } + } + } + + impl<'a> Deref for $FixedString<'a> { + type Target = $AString; + fn deref(&self) -> &$AString { + &self.hdr.base + } + } + + impl<'a> DerefMut for $FixedString<'a> { + fn deref_mut(&mut self) -> &mut $AString { + &mut self.hdr.base + } + } + + impl<'a> fmt::Write for $FixedString<'a> { + fn write_str(&mut self, s: &str) -> Result<(), fmt::Error> { + $AString::write_str(self, s) + } + } + + impl<'a> fmt::Display for $FixedString<'a> { + fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { + <$AString as fmt::Display>::fmt(self, f) + } + } + + impl<'a> fmt::Debug for $FixedString<'a> { + fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { + <$AString as fmt::Debug>::fmt(self, f) + } + } + + impl<'a> cmp::PartialEq for $FixedString<'a> { + fn eq(&self, other: &$FixedString<'a>) -> bool { + $AString::eq(self, other) + } + } + + impl<'a> cmp::PartialEq<[$char_t]> for $FixedString<'a> { + fn eq(&self, other: &[$char_t]) -> bool { + $AString::eq(self, other) + } + } + + impl<'a, 'b> cmp::PartialEq<&'b [$char_t]> for $FixedString<'a> { + fn eq(&self, other: &&'b [$char_t]) -> bool { + $AString::eq(self, *other) + } + } + + impl<'a> cmp::PartialEq<str> for $FixedString<'a> { + fn eq(&self, other: &str) -> bool { + $AString::eq(self, other) + } + } + + impl<'a, 'b> cmp::PartialEq<&'b str> for $FixedString<'a> { + fn eq(&self, other: &&'b str) -> bool { + $AString::eq(self, *other) + } + } + + impl<'a> Drop for $FixedString<'a> { + fn drop(&mut self) { + unsafe { + self.finalize(); + } + } + } + } +} + +/////////////////////////////////////////// +// Bindings for nsCString (u8 char type) // +/////////////////////////////////////////// + +define_string_types! { + char_t = u8; + + AString = nsACString; + String = nsCString; + FixedString = nsFixedCString; + + StringRepr = nsCStringRepr; + FixedStringRepr = nsFixedCStringRepr; + AutoStringRepr = nsAutoCStringRepr; +} + +impl nsACString { + /// Leaves the nsACString in an unstable state with a dangling data pointer. + /// Should only be used in drop implementations of rust types which wrap + /// this type. + unsafe fn finalize(&mut self) { + Gecko_FinalizeCString(self); + } + + pub fn assign(&mut self, other: &nsACString) { + unsafe { + Gecko_AssignCString(self as *mut _, other as *const _); + } + } + + pub fn assign_utf16(&mut self, other: &nsAString) { + self.assign(&nsCString::new()); + self.append_utf16(other); + } + + pub fn append(&mut self, other: &nsACString) { + unsafe { + Gecko_AppendCString(self as *mut _, other as *const _); + } + } + + pub fn append_utf16(&mut self, other: &nsAString) { + unsafe { + Gecko_AppendUTF16toCString(self as *mut _, other as *const _); + } + } + + pub unsafe fn as_str_unchecked(&self) -> &str { + str::from_utf8_unchecked(self) + } +} + +impl<'a> From<&'a str> for nsCString<'a> { + fn from(s: &'a str) -> nsCString<'a> { + s.as_bytes().into() + } +} + +impl From<Box<str>> for nsCString<'static> { + fn from(s: Box<str>) -> nsCString<'static> { + s.into_string().into() + } +} + +impl From<String> for nsCString<'static> { + fn from(s: String) -> nsCString<'static> { + s.into_bytes().into() + } +} + +// Support for the write!() macro for appending to nsACStrings +impl fmt::Write for nsACString { + fn write_str(&mut self, s: &str) -> Result<(), fmt::Error> { + self.append(&nsCString::from(s)); + Ok(()) + } +} + +impl fmt::Display for nsACString { + fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { + fmt::Display::fmt(&String::from_utf8_lossy(&self[..]), f) + } +} + +impl fmt::Debug for nsACString { + fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { + fmt::Debug::fmt(&String::from_utf8_lossy(&self[..]), f) + } +} + +impl cmp::PartialEq<str> for nsACString { + fn eq(&self, other: &str) -> bool { + &self[..] == other.as_bytes() + } +} + +#[macro_export] +macro_rules! ns_auto_cstring { + ($name:ident) => { + let mut buf: [u8; 64] = [0; 64]; + let mut $name = $crate::nsFixedCString::new(&mut buf); + } +} + +/////////////////////////////////////////// +// Bindings for nsString (u16 char type) // +/////////////////////////////////////////// + +define_string_types! { + char_t = u16; + + AString = nsAString; + String = nsString; + FixedString = nsFixedString; + + StringRepr = nsStringRepr; + FixedStringRepr = nsFixedStringRepr; + AutoStringRepr = nsAutoStringRepr; +} + +impl nsAString { + /// Leaves the nsAString in an unstable state with a dangling data pointer. + /// Should only be used in drop implementations of rust types which wrap + /// this type. + unsafe fn finalize(&mut self) { + Gecko_FinalizeString(self); + } + + pub fn assign(&mut self, other: &nsAString) { + unsafe { + Gecko_AssignString(self as *mut _, other as *const _); + } + } + + pub fn assign_utf8(&mut self, other: &nsACString) { + self.assign(&nsString::new()); + self.append_utf8(other); + } + + pub fn append(&mut self, other: &nsAString) { + unsafe { + Gecko_AppendString(self as *mut _, other as *const _); + } + } + + pub fn append_utf8(&mut self, other: &nsACString) { + unsafe { + Gecko_AppendUTF8toString(self as *mut _, other as *const _); + } + } +} + +// NOTE: The From impl for a string slice for nsString produces a <'static> +// lifetime, as it allocates. +impl<'a> From<&'a str> for nsString<'static> { + fn from(s: &'a str) -> nsString<'static> { + s.encode_utf16().collect::<Vec<u16>>().into() + } +} + +// Support for the write!() macro for writing to nsStrings +impl fmt::Write for nsAString { + fn write_str(&mut self, s: &str) -> Result<(), fmt::Error> { + // Directly invoke gecko's routines for appending utf8 strings to + // nsAString values, to avoid as much overhead as possible + self.append_utf8(&nsCString::from(s)); + Ok(()) + } +} + +impl fmt::Display for nsAString { + fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { + fmt::Display::fmt(&String::from_utf16_lossy(&self[..]), f) + } +} + +impl fmt::Debug for nsAString { + fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { + fmt::Debug::fmt(&String::from_utf16_lossy(&self[..]), f) + } +} + +impl cmp::PartialEq<str> for nsAString { + fn eq(&self, other: &str) -> bool { + other.encode_utf16().eq(self.iter().cloned()) + } +} + +#[macro_export] +macro_rules! ns_auto_string { + ($name:ident) => { + let mut buf: [u16; 64] = [0; 64]; + let mut $name = $crate::nsFixedString::new(&mut buf); + } +} + +// NOTE: These bindings currently only expose infallible operations. Perhaps +// consider allowing for fallible methods? +extern "C" { + // Gecko implementation in nsSubstring.cpp + fn Gecko_FinalizeCString(this: *mut nsACString); + fn Gecko_AssignCString(this: *mut nsACString, other: *const nsACString); + fn Gecko_AppendCString(this: *mut nsACString, other: *const nsACString); + + fn Gecko_FinalizeString(this: *mut nsAString); + fn Gecko_AssignString(this: *mut nsAString, other: *const nsAString); + fn Gecko_AppendString(this: *mut nsAString, other: *const nsAString); + + // Gecko implementation in nsReadableUtils.cpp + fn Gecko_AppendUTF16toCString(this: *mut nsACString, other: *const nsAString); + fn Gecko_AppendUTF8toString(this: *mut nsAString, other: *const nsACString); +} + +////////////////////////////////////// +// Repr Validation Helper Functions // +////////////////////////////////////// + +pub mod test_helpers { + //! This module only exists to help with ensuring that the layout of the + //! structs inside of rust and C++ are identical. + //! + //! It is public to ensure that these testing functions are avaliable to + //! gtest code. + + use super::{ + nsFixedCStringRepr, + nsFixedStringRepr, + nsCStringRepr, + nsStringRepr, + F_NONE, + F_TERMINATED, + F_VOIDED, + F_SHARED, + F_OWNED, + F_FIXED, + F_LITERAL, + F_CLASS_FIXED, + }; + use std::mem; + + /// Generates an #[no_mangle] extern "C" function which returns the size and + /// alignment of the given type with the given name. + macro_rules! size_align_check { + ($T:ty, $fname:ident) => { + #[no_mangle] + #[allow(non_snake_case)] + pub extern fn $fname(size: *mut usize, align: *mut usize) { + unsafe { + *size = mem::size_of::<$T>(); + *align = mem::align_of::<$T>(); + } + } + } + } + + size_align_check!(nsStringRepr, Rust_Test_ReprSizeAlign_nsString); + size_align_check!(nsCStringRepr, Rust_Test_ReprSizeAlign_nsCString); + size_align_check!(nsFixedStringRepr, Rust_Test_ReprSizeAlign_nsFixedString); + size_align_check!(nsFixedCStringRepr, Rust_Test_ReprSizeAlign_nsFixedCString); + + /// Generates a $[no_mangle] extern "C" function which returns the size, + /// alignment and offset in the parent struct of a given member, with the + /// given name. + /// + /// This method can trigger Undefined Behavior if the accessing the member + /// $member on a given type would use that type's `Deref` implementation. + macro_rules! member_check { + ($T:ty, $member:ident, $method:ident) => { + #[no_mangle] + #[allow(non_snake_case)] + pub extern fn $method(size: *mut usize, + align: *mut usize, + offset: *mut usize) { + unsafe { + // Create a temporary value of type T to get offsets, sizes + // and aligns off of + let tmp: $T = mem::zeroed(); + *size = mem::size_of_val(&tmp.$member); + *align = mem::align_of_val(&tmp.$member); + *offset = + (&tmp.$member as *const _ as usize) - + (&tmp as *const _ as usize); + mem::forget(tmp); + } + } + } + } + + member_check!(nsStringRepr, data, Rust_Test_Member_nsString_mData); + member_check!(nsStringRepr, length, Rust_Test_Member_nsString_mLength); + member_check!(nsStringRepr, flags, Rust_Test_Member_nsString_mFlags); + member_check!(nsCStringRepr, data, Rust_Test_Member_nsCString_mData); + member_check!(nsCStringRepr, length, Rust_Test_Member_nsCString_mLength); + member_check!(nsCStringRepr, flags, Rust_Test_Member_nsCString_mFlags); + member_check!(nsFixedStringRepr, capacity, Rust_Test_Member_nsFixedString_mFixedCapacity); + member_check!(nsFixedStringRepr, buffer, Rust_Test_Member_nsFixedString_mFixedBuf); + member_check!(nsFixedCStringRepr, capacity, Rust_Test_Member_nsFixedCString_mFixedCapacity); + member_check!(nsFixedCStringRepr, buffer, Rust_Test_Member_nsFixedCString_mFixedBuf); + + #[no_mangle] + #[allow(non_snake_case)] + pub extern fn Rust_Test_NsStringFlags(f_none: *mut u32, + f_terminated: *mut u32, + f_voided: *mut u32, + f_shared: *mut u32, + f_owned: *mut u32, + f_fixed: *mut u32, + f_literal: *mut u32, + f_class_fixed: *mut u32) { + unsafe { + *f_none = F_NONE; + *f_terminated = F_TERMINATED; + *f_voided = F_VOIDED; + *f_shared = F_SHARED; + *f_owned = F_OWNED; + *f_fixed = F_FIXED; + *f_literal = F_LITERAL; + *f_class_fixed = F_CLASS_FIXED; + } + } +} |