//! This crate defines a macro named `asm_func!` which is suitable for
//! generating a single `global_asm!`-defined function.
//!
//! This macro takes care of platform-specific directives to get the symbol
//! attributes correct (e.g. ELF symbols get a size and are flagged as a
//! function) and additionally handles visibility across platforms. All symbols
//! should be visible to Rust but not visible externally outside of a `*.so`.
//!
//! It also exports a an `asm_sym!` macro which can be used to reference symbols
//! from within `global_asm!`-defined functions, and handles adding the leading
//! underscore that macOS prepends to symbols for you.

cfg_if::cfg_if! {
    if #[cfg(target_os = "macos")] {
        #[macro_export]
        macro_rules! asm_func {
            ($name:expr, $($body:tt)*) => {
                std::arch::global_asm!(concat!(
                    ".p2align 4\n",
                    ".private_extern _", $name, "\n",
                    ".global _", $name, "\n",
                    "_", $name, ":\n",
                    $($body)*
                ));
            };
        }

        #[macro_export]
        macro_rules! asm_sym {
            ( $( $name:tt )* ) => ( concat!("_", $( $name )* ) )
        }
    } else if #[cfg(target_os = "windows")] {
        #[macro_export]
        macro_rules! asm_func {
            ($name:expr, $($body:tt)*) => {
                std::arch::global_asm!(concat!(
                    ".def ", $name, "\n",
                    ".scl 2\n",
                    ".type 32\n",
                    ".endef\n",
                    ".global ", $name, "\n",
                    ".p2align 4\n",
                    $name, ":\n",
                    $($body)*
                ));
            };
        }

        #[macro_export]
        macro_rules! asm_sym {
            ( $( $name:tt )* ) => ( $( $name )* )
        }
    } else {
        // Note that for now this "else" clause just assumes that everything
        // other than macOS is ELF and has the various directives here for
        // that.
        cfg_if::cfg_if! {
            if #[cfg(target_arch = "arm")] {
                #[macro_export]
                macro_rules! elf_func_type_header {
                    ($name:tt) => (concat!(".type ", $name, ",%function\n"))
                }
            } else {
                #[macro_export]
                macro_rules! elf_func_type_header {
                    ($name:tt) => (concat!(".type ", $name, ",@function\n"))
                }
            }
        }

        #[macro_export]
        macro_rules! asm_func {
            ($name:expr, $($body:tt)*) => {
                std::arch::global_asm!(concat!(
                    ".p2align 4\n",
                    ".hidden ", $name, "\n",
                    ".global ", $name, "\n",
                    $crate::elf_func_type_header!($name),
                    $name, ":\n",
                    concat!($($body)*),
                    ".size ", $name, ",.-", $name,
                ));
            };
        }

        #[macro_export]
        macro_rules! asm_sym {
            ( $( $name:tt )* ) => ( $( $name )* )
        }
    }
}