preserves/implementations/rust/preserves/src/value/writer.rs

use num::bigint::BigInt;
use std::io::Error;
use super::signed_integer::SignedIntegerRepr;
use super::repr::{Value, NestedValue, IOValue, UnwrappedIOValue, Float, Double};

pub type Result<T> = std::result::Result<T, Error>;

pub trait AnnotationWriter: Writer {
    fn start_annotation(&mut self) -> Result<()>;
    fn start_value(&mut self) -> Result<()>;
}

pub trait CompoundWriter: Writer {
    fn extend(&mut self) -> Result<()>;
    fn delimit(&mut self) -> Result<()>;
}

pub trait Writer: Sized {
    type AnnWriter: AnnotationWriter;
    type SeqWriter: CompoundWriter;
    type SetWriter: CompoundWriter;
    type EmbeddedWriter: Writer;

    fn align(&mut self, natural_chunksize: u64) -> Result<()>;

    fn start_annotations(&mut self) -> Result<Self::AnnWriter>;
    fn end_annotations(&mut self, ann: Self::AnnWriter) -> Result<()>;

    fn write_bool(&mut self, v: bool) -> Result<()>;

    fn write_f32(&mut self, v: f32) -> Result<()>;
    fn write_f64(&mut self, v: f64) -> Result<()>;

    fn write_i8(&mut self, v: i8) -> Result<()>;
    fn write_u8(&mut self, v: u8) -> Result<()>;
    fn write_i16(&mut self, v: i16) -> Result<()>;
    fn write_u16(&mut self, v: u16) -> Result<()>;
    fn write_i32(&mut self, v: i32) -> Result<()>;
    fn write_u32(&mut self, v: u32) -> Result<()>;
    fn write_i64(&mut self, v: i64) -> Result<()>;
    fn write_u64(&mut self, v: u64) -> Result<()>;
    fn write_i128(&mut self, v: i128) -> Result<()>;
    fn write_u128(&mut self, v: u128) -> Result<()>;
    fn write_int(&mut self, v: &BigInt) -> Result<()>;

    fn write_string(&mut self, v: &str) -> Result<()>;
    fn write_bytes(&mut self, v: &[u8]) -> Result<()>;
    fn write_symbol(&mut self, v: &str) -> Result<()>;

    fn start_record(&mut self, field_count: Option<usize>) -> Result<Self::SeqWriter>;
    fn start_sequence(&mut self, item_count: Option<usize>) -> Result<Self::SeqWriter>;
    fn end_seq(&mut self, seq: Self::SeqWriter) -> Result<()>;

    fn start_set(&mut self, item_count: Option<usize>) -> Result<Self::SetWriter>;
    fn start_dictionary(&mut self, entry_count: Option<usize>) -> Result<Self::SetWriter>;
    fn end_set(&mut self, set: Self::SetWriter) -> Result<()>;

    fn start_embedded(&mut self) -> Result<Self::EmbeddedWriter>;
    fn end_embedded(&mut self, ptr: Self::EmbeddedWriter) -> Result<()>;

    //---------------------------------------------------------------------------

    fn write(&mut self, v: &IOValue) -> Result<()> {
        match v.annotations().maybe_slice() {
            None => {
                self.write_value(v.value())?;
            }
            Some(anns) => {
                let mut a = self.start_annotations()?;
                for ann in anns {
                    a.start_annotation()?;
                    a.write(ann)?;
                }
                a.start_value()?;
                a.write_value(v.value())?;
                self.end_annotations(a)?;
            }
        }
        Ok(())
    }

    fn write_value(&mut self, v: &UnwrappedIOValue) -> Result<()> {
        match v {
            Value::Boolean(b) => self.write_bool(*b),
            Value::Float(Float(f)) => self.write_f32(*f),
            Value::Double(Double(d)) => self.write_f64(*d),
            Value::SignedInteger(n) => match n.repr() {
                SignedIntegerRepr::I128(i) => self.write_i128(*i),
                SignedIntegerRepr::U128(u) => self.write_u128(*u),
                SignedIntegerRepr::Big(n) => self.write_int(n),
            }
            Value::String(s) => self.write_string(s),
            Value::ByteString(bs) => self.write_bytes(bs),
            Value::Symbol(s) => self.write_symbol(s),
            Value::Record(r) => {
                let mut c = self.start_record(Some(r.arity()))?;
                c.extend()?;
                c.write(r.label())?;
                c.delimit()?;
                for f in r.fields() {
                    c.extend()?;
                    c.write(f)?;
                    c.delimit()?;
                }
                self.end_seq(c)
            }
            Value::Sequence(vs) => {
                let mut c = self.start_sequence(Some(vs.len()))?;
                for v in vs {
                    c.extend()?;
                    c.write(v)?;
                    c.delimit()?;
                }
                self.end_seq(c)
            }
            Value::Set(vs) => {
                let mut c = self.start_set(Some(vs.len()))?;
                for v in vs {
                    c.extend()?;
                    c.write(v)?;
                    c.delimit()?;
                }
                self.end_set(c)
            }
            Value::Dictionary(vs) => {
                let mut c = self.start_dictionary(Some(vs.len()))?;
                for (k, v) in vs {
                    c.extend()?;
                    c.write(k)?;
                    c.write(v)?;
                    c.delimit()?;
                }
                self.end_set(c)
            }
            Value::Embedded(d) => {
                let mut c = self.start_embedded()?;
                c.write(&d)?;
                self.end_embedded(c)
            }
        }
    }
}

pub fn varint<W: std::io::Write>(w: &mut W, mut v: u64) -> Result<usize> {
    let mut byte_count = 0;
    loop {
        byte_count += 1;
        if v < 128 {
            w.write_all(&[v as u8])?;
            return Ok(byte_count);
        } else {
            w.write_all(&[((v & 0x7f) + 128) as u8])?;
            v >>= 7;
        }
    }
}