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
134
135
136
137
138
139
140
141
142
143

//! Decorator module for creating native functions callable from haru
//!
//! ```rust,text
//! extern crate haru;
//! use haru::vmbindings::vm::Vm;
//! use haru::vmbindings::value::Value;
//!
//! #[hana_function()]
//! fn succ(i: Value::Int) {
//!     Value::Int(i + 1)
//! }
//! ```
//!
//! The macro should generate a function with the signature:
//! ```rust,text
//! pub extern "C" fn succ(vm: *const Vm, nargs: u16) {
//!     ...
//! }
//! ```

extern crate proc_macro;
#[macro_use]
extern crate quote;
use proc_macro::TokenStream;
use syn;

/// Generates a native function callable from haru's virtual machine.
///
/// Note that the file containing your native function must contain
/// the imports for Vm and Value:
///
/// ```rust,text
/// extern crate haru;
/// use haru::vmbindings::value::Value;
/// use haru::vmbindings::vm::Vm;
/// ```
///
/// Example:
///
/// ```rust,text
/// #[hana_function()]
/// fn fopen(path: Value::String, mode: Value::String) {
///     [body of fopen]
/// }
/// ```
///
/// should generate a function like this (semi pseudocode):
///
/// ```rust,text
/// pub extern "C" fn fopen(cvm : *mut Vm, nargs : u16) {
///     if nargs != [nargs] { [raise vm error] }
///     fn fopen() -> Value {
///         let Value::String(path) = vm.stack.pop().unwrap() ||
///                 panic!("expected path to be string");
///         let Value::String(mode) = vm.stack.pop().unwrap() ||
///                 panic!("expected mode to be string");
///         [body of fopen]
///     }
///     let vm = unsafe { &mut *cvm };
///     let result : Value = #name(vm);
///     vm.stack.push(result.wrap());
/// }
/// ```
#[proc_macro_attribute]
pub fn hana_function(_args: TokenStream, item: TokenStream) -> TokenStream {
    let input = syn::parse_macro_input!(item as syn::ItemFn);
    let name = &input.ident;
    let body = &input.block;

    let mut args_setup = Vec::new();
    for arg in input.decl.inputs.iter() {
        match *arg {
            syn::FnArg::Captured(ref cap) => {
                let pattern = match &cap.pat {
                    syn::Pat::Ident(x) => x,
                    _ => panic!("expected identifier argument!"),
                };
                let path = match &cap.ty {
                    syn::Type::Path(x) => &x.path.segments,
                    _ => panic!("expected type for {:?} to be path!", pattern),
                };
                // match and unwrap type from value variant
                // also panics if unexpected type
                let atype = path.last().unwrap().into_value().ident.to_string();
                let atypes = syn::LitStr::new(atype.as_str(), quote::__rt::Span::call_site());
                let argname = syn::LitStr::new(
                    pattern.ident.to_string().as_str(),
                    quote::__rt::Span::call_site(),
                );
                let match_arm = match atype.as_str() {
                    "Int" | "Float" | "NativeFn" | "Fn" | "Str" | "Record" | "Array" => {
                        quote!(#path(x) => x)
                    }
                    "Any" => quote!(#path => x),
                    _ => panic!("unknown type {}!", atype),
                };
                args_setup.push(match atype.as_str() {
                    "Any" => quote!(let #pattern = vm.stack.pop().unwrap().unwrap();),
                    _ => quote!(
                        let #pattern = {
                            match vm.stack.pop().unwrap().unwrap() {
                                #match_arm,
                                _ => panic!("expected argument {} to be type {}",
                                    #argname,
                                    #atypes)
                            }
                        };
                    ),
                });
            }
            _ => unimplemented!(),
        }
    }

    let arglen = syn::LitInt::new(
        input.decl.inputs.len() as u64,
        syn::IntSuffix::None,
        quote::__rt::Span::call_site(),
    );

    quote!(
        pub extern "C" fn #name(cvm : *mut Vm, nargs : u16) {
            let vm = unsafe { &mut *cvm };
            if nargs != #arglen {
                use super::VmError;
                vm.error = VmError::ERROR_MISMATCH_ARGUMENTS;
                vm.error_expected = #arglen;
                return;
            }
            #[inline(always)]
            fn #name(vm: &mut Vm) -> Value {
                #(#args_setup)*
                #body
            }
            let result : Value = #name(vm);
            match result {
                Value::PropagateError => (),
                _ => vm.stack.push(result.wrap()),
            }
        }
    )
    .into()
}