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
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161

//! Scheme runtime for Incremental
//!
//! Low level runtime functions for memory management, object layout, low level
//! bit fiddling etc.

use crate::{immediate::*, x86::WORDSIZE};
use std::{
    ffi::CStr,
    fs::{self, File},
    io::{self, Write},
    os::{raw::c_char, unix::io::AsRawFd},
};

/// Checks if a function is defined in the built in runtime
pub fn defined(name: &str) -> bool {
    SYMBOLS.contains(&name)
}

// All symbols exported to the runtime from this module
const SYMBOLS: [&str; 6] = ["string-length", "symbol=?", "exit",
    "rt-open-write", "writeln", "type"];

#[no_mangle]
pub extern "C" fn print(val: i64, nested: bool) {
    match val & MASK {
        NUM => print!("{}", val >> SHIFT),
        BOOL => print!("{}", if val == TRUE { "#t" } else { "#f" }),
        CHAR => {
            let c = ((val >> SHIFT) as u8) as char;
            let p = match c {
                '\t' => "#\\tab".into(),
                '\n' => "#\\newline".into(),
                '\r' => "#\\return".into(),
                ' ' => "#\\space".into(),
                _ => format!("#\\{}", c),
            };
            print!("{}", &p)
        }
        PAIR => {
            let pcar = car(val);
            let pcdr = cdr(val);

            if !nested {
                print!("(")
            };

            print(pcar, false);

            if pcdr != NIL {
                if (pcdr & MASK) != PAIR {
                    print!(" . ");
                    print(pcdr, false);
                } else {
                    print!(" ");
                    print(pcdr, true);
                }
            }
            if !nested {
                print!(")")
            };
        }
        NIL => {
            print!("()");
        }
        STR => print!("\"{}\"", str_str(val)),
        SYM => print!("'{}", sym_name(val)),

        VEC => {
            print!("[");

            for i in 0..vec_len(val) {
                print(vec_nth(val, i), false);

                if i != vec_len(val) - 1 {
                    print!(" ");
                }
            }

            print!("]");

            io::stdout().flush().unwrap();
        }
        _ => panic!("Unexpected value returned by runtime: {}", val),
    }

    io::stdout().flush().unwrap();
}

#[no_mangle]
pub extern "C" fn car(val: i64) -> i64 {
    assert!((val & MASK) == PAIR);

    unsafe { *((val - PAIR) as *mut i64) }
}

#[no_mangle]
pub extern "C" fn cdr(val: i64) -> i64 {
    assert!((val & MASK) == PAIR);

    unsafe { *((val - PAIR + 8) as *mut i64) }
}

#[no_mangle]
pub extern "C" fn string_length(val: i64) -> usize {
    assert!((val & MASK) == STR);

    let len = unsafe { *((val - STR) as *mut usize) };
    len << SHIFT
}

#[no_mangle]
pub extern "C" fn symbol_eq(a: i64, b: i64) -> i64 {
    if (a == b) && ((a & MASK) == SYM) {
        TRUE
    } else {
        FALSE
    }
}

#[no_mangle]
pub extern "C" fn rt_open_write(fname: i64) -> i64 {
    let f = File::create(str_str(fname)).unwrap().as_raw_fd();
    i64::from(f << SHIFT)
}

#[no_mangle]
pub extern "C" fn writeln(data: i64, port: i64) -> i64 {
    let path = str_str(vec_nth(port, 1));
    let s = format!("{}\n", str_str(data));

    fs::write(&path, s).unwrap_or_else(|_| panic!("Failed to write to {}", &path));

    NIL
}

// Get a string pointer from a string object
fn str_str(val: i64) -> String {
    assert!((val & MASK) == STR);

    let s = unsafe { CStr::from_ptr((val - STR + 8) as *const c_char) };
    s.to_string_lossy().into_owned()
}

fn sym_name(val: i64) -> String {
    assert!((val & MASK) == SYM);

    let s = unsafe { CStr::from_ptr((val - SYM + 16) as *const c_char) };
    s.to_string_lossy().into_owned()
}

fn vec_len(val: i64) -> i64 {
    assert!((val & MASK) == VEC);

    unsafe { *((val - VEC) as *const i64) }
}

fn vec_nth(val: i64, n: i64) -> i64 {
    assert!((val & MASK) == VEC);

    unsafe { *((val - VEC + WORDSIZE + (n * WORDSIZE)) as *const i64) }
}