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Use coercion in BFF argument passing

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Alex Bethel 2021-07-22 22:08:04 -05:00
parent 50f9bfa4c6
commit 501d182fb4
1 changed files with 8 additions and 59 deletions
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67
src/variables.rs
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@ -54,66 +54,15 @@ pub enum Value {
}
impl Value {
/// Write an AbleScript value to a Brainfuck input stream. This
/// should generally only be called on `Write`rs that cannot fail,
/// e.g., `Vec<u8>`, because any IO errors will cause a panic.
///
/// The mapping from values to encodings is as follows, where all
/// multi-byte integers are little-endian:
///
/// | AbleScript representation | Brainfuck representation |
/// |---------------------------|-------------------------------------------------------------|
/// | Nul | `00` |
/// | Str | `01` [length, 4 bytes] [string, \[LENGTH\] bytes, as UTF-8] |
/// | Int | `02` [value, 4 bytes] |
/// | Bool | `03` `00` false, `03` `01` true. |
/// | Abool | `04` `00` never, `04` `01` always, `04` `02` sometimes. |
/// | Brainfuck Functio | `05` `00` [length, 4 bytes] [source code, \[LENGTH\] bytes] |
/// | AbleScript Functio | `05` `01` (todo, not yet finalized or implemented) |
///
/// The existing mappings should never change, as they are
/// directly visible from Brainfuck code and modifying them would
/// break a significant amount of AbleScript code. If more types
/// are added in the future, they should be assigned the remaining
/// discriminant bytes from 06..FF.
/// Write an AbleScript value to a Brainfuck input stream by
/// coercing the value to an integer, then truncating that integer
/// to a single byte, then writing that byte. This should only be
/// called on `Write`rs that cannot fail, e.g., `Vec<u8>`, because
/// any IO errors will cause a panic.
pub fn bf_write(&self, stream: &mut impl Write) {
match self {
Value::Nul => stream.write_all(&[0]),
Value::Str(s) => stream
.write_all(&[1])
.and_then(|_| stream.write_all(&(s.len() as u32).to_le_bytes()))
.and_then(|_| stream.write_all(&s.as_bytes())),
Value::Int(v) => stream
.write_all(&[2])
.and_then(|_| stream.write_all(&v.to_le_bytes())),
Value::Bool(b) => stream
.write_all(&[3])
.and_then(|_| stream.write_all(&[*b as _])),
Value::Abool(a) => stream.write_all(&[4]).and_then(|_| {
stream.write_all(&[match *a {
Abool::Never => 0,
Abool::Sometimes => 2,
Abool::Always => 1,
}])
}),
Value::Functio(f) => stream.write_all(&[5]).and_then(|_| match f {
Functio::BfFunctio {
instructions,
tape_len: _,
} => {
// NOTE(Alex): Tape length should maybe be taken
// into account here.
stream
.write_all(&[0])
.and_then(|_| stream.write_all(&(instructions.len() as u32).to_le_bytes()))
.and_then(|_| stream.write_all(&instructions))
}
Functio::AbleFunctio { params: _, body: _ } => {
todo!()
}
}),
}
.expect("Failed to write to Brainfuck input");
stream
.write_all(&[self.clone().into_i32() as u8])
.expect("Failed to write to Brainfuck input");
}
/// Coerce a value to an integer.