1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133

//! Macros for including transformed files at compile time.
//!
//! The macros include a file similar to [`include_bytes!`], but transform the
//! data before inclusion (e.g. runs an assembler).
//!
//! The original purpose of this project was including assembled application
//! processor initialization code in [libhermit-rs] using [`include_nasm_bin!`].
//!
//! ```
//! [dependencies]
//! include-transformed = "0.2"
//! ```
//!
//! # Requirements
//!
//! This project depends on the unstable features `proc_macro_span` [#54725] and
//! `proc_macro_expand` [#90765], which are only available on the nightly
//! toolchain channel.
//!
//! [libhermit-rs]: https://github.com/hermitcore/libhermit-rs
//! [#54725]: https://github.com/rust-lang/rust/issues/54725
//! [#90765]: https://github.com/rust-lang/rust/issues/90765

#![feature(proc_macro_expand)]
#![feature(proc_macro_span)]

use std::{io::Read, path::Path, process::Command};

use proc_macro::Literal;
use quote::quote;
use syn::{parse_macro_input, LitStr};
use tempfile::NamedTempFile;

/// Simluates inclusion.
///
/// This makes sure, the proc-macro is rerun if the included file has changed.
fn simulate_inclusion(file: &LitStr) -> Result<(), proc_macro::ExpandError> {
    let src = quote! {
        include_bytes!(#file)
    };
    proc_macro::TokenStream::from(src).expand_expr().map(drop)
}

macro_rules! expand_macro_input {
    ($tokenstream:ident) => {
        match $tokenstream.expand_expr() {
            Ok(tokenstream) => tokenstream,
            Err(err) => {
                let tokenstream = proc_macro2::TokenStream::from($tokenstream);
                let error = syn::Error::new_spanned(tokenstream, err);
                return proc_macro::TokenStream::from(error.into_compile_error());
            }
        }
    };
}

fn include_transformed(
    input: proc_macro::TokenStream,
    transform: impl FnOnce(&Path, &Path) -> Result<(), proc_macro::TokenStream>,
) -> proc_macro::TokenStream {
    let input = expand_macro_input!(input);
    let file = parse_macro_input!(input as LitStr);

    simulate_inclusion(&file).unwrap();
    let mut src = proc_macro::Span::call_site().source_file().path();
    src.set_file_name(file.value());
    let mut dst = NamedTempFile::new().unwrap();

    if let Err(output) = transform(src.as_path(), dst.path()) {
        return output;
    }

    let output = {
        let mut buf = Vec::new();
        dst.read_to_end(&mut buf).unwrap();
        Literal::byte_string(&buf)
    };
    proc_macro::TokenStream::from(proc_macro::TokenTree::from(output))
}

macro_rules! bail {
    ($($arg:tt)*) => {{
        let msg = format!($($arg)*);
        let compile_error = quote! {
            compile_error!(#msg)
        };
        return Err(proc_macro::TokenStream::from(compile_error));
    }};
}

fn run(command: &mut Command, program: &str) -> Result<(), proc_macro::TokenStream> {
    let status = match command.status() {
        Ok(status) => status,
        Err(err) => bail!("Failed to execute {program}: {err}"),
    };
    if !status.success() {
        bail!("{program} finished with: {status}");
    }
    Ok(())
}

/// Assembles a file with [NASM] into raw binary and includes the output as a
/// reference to a byte array.
///
/// The file is located relative to the current file (similarly to how modules
/// are found). This macro will yield an expression of type `&'static [u8; N]`
/// which is the contents of the assembled file.
///
/// # Dependencies
///
/// This macro requires [NASM] to be installed.
///
/// # Examples
///
/// Assume there is a file 'boot.asm' in the same directory as 'main.rs'.
///
/// ```ignore
/// let boot_code = include_nasm_bin!("boot.asm");
/// ```
///
/// This code is equivalent to running `nasm -f bin boot.asm -o boot` and
/// including `boot` via [`include_bytes!`].
///
/// [NASM]: https://www.nasm.us/
#[proc_macro]
pub fn include_nasm_bin(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
    include_transformed(input, |src, dst| {
        let program = "nasm";
        let mut command = Command::new(program);
        command.arg("-f").arg("bin").arg(src).arg("-o").arg(dst);
        run(&mut command, program)
    })
}