233 lines
8.0 KiB
Rust
233 lines
8.0 KiB
Rust
//! Generic [Writer] trait for unparsing Preserves [Value]s, implemented by code that provides
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//! each specific transfer syntax.
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use super::boundary as B;
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use super::repr::{Double, NestedValue, Value};
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use super::signed_integer::SignedIntegerRepr;
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use super::DomainEncode;
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use num::bigint::BigInt;
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use std::io;
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#[doc(hidden)]
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/// Utility trait for tracking unparser state during production of compound `Value`s.
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pub trait CompoundWriter: Writer {
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fn boundary(&mut self, b: &B::Type) -> io::Result<()>;
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}
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/// Generic unparser for Preserves.
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pub trait Writer: Sized {
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// Hiding these from the documentation for the moment because I don't want to have to
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// document the whole Boundary thing.
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#[doc(hidden)]
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type AnnWriter: CompoundWriter;
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#[doc(hidden)]
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type RecWriter: CompoundWriter;
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#[doc(hidden)]
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type SeqWriter: CompoundWriter;
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#[doc(hidden)]
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type SetWriter: CompoundWriter;
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#[doc(hidden)]
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type DictWriter: CompoundWriter;
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#[doc(hidden)]
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type EmbeddedWriter: Writer;
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#[doc(hidden)]
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fn start_annotations(&mut self) -> io::Result<Self::AnnWriter>;
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#[doc(hidden)]
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fn end_annotations(&mut self, ann: Self::AnnWriter) -> io::Result<()>;
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#[doc(hidden)]
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fn write_bool(&mut self, v: bool) -> io::Result<()>;
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#[doc(hidden)]
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fn write_f64(&mut self, v: f64) -> io::Result<()>;
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#[doc(hidden)]
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fn write_i8(&mut self, v: i8) -> io::Result<()>;
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#[doc(hidden)]
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fn write_u8(&mut self, v: u8) -> io::Result<()>;
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#[doc(hidden)]
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fn write_i16(&mut self, v: i16) -> io::Result<()>;
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#[doc(hidden)]
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fn write_u16(&mut self, v: u16) -> io::Result<()>;
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#[doc(hidden)]
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fn write_i32(&mut self, v: i32) -> io::Result<()>;
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#[doc(hidden)]
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fn write_u32(&mut self, v: u32) -> io::Result<()>;
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#[doc(hidden)]
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fn write_i64(&mut self, v: i64) -> io::Result<()>;
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#[doc(hidden)]
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fn write_u64(&mut self, v: u64) -> io::Result<()>;
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#[doc(hidden)]
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fn write_i128(&mut self, v: i128) -> io::Result<()>;
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#[doc(hidden)]
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fn write_u128(&mut self, v: u128) -> io::Result<()>;
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#[doc(hidden)]
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fn write_int(&mut self, v: &BigInt) -> io::Result<()>;
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#[doc(hidden)]
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fn write_string(&mut self, v: &str) -> io::Result<()>;
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#[doc(hidden)]
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fn write_bytes(&mut self, v: &[u8]) -> io::Result<()>;
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#[doc(hidden)]
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fn write_symbol(&mut self, v: &str) -> io::Result<()>;
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#[doc(hidden)]
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fn start_record(&mut self, field_count: Option<usize>) -> io::Result<Self::RecWriter>;
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#[doc(hidden)]
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fn end_record(&mut self, rec: Self::RecWriter) -> io::Result<()>;
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#[doc(hidden)]
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fn start_sequence(&mut self, item_count: Option<usize>) -> io::Result<Self::SeqWriter>;
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#[doc(hidden)]
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fn end_sequence(&mut self, seq: Self::SeqWriter) -> io::Result<()>;
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#[doc(hidden)]
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fn start_set(&mut self, item_count: Option<usize>) -> io::Result<Self::SetWriter>;
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#[doc(hidden)]
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fn end_set(&mut self, set: Self::SetWriter) -> io::Result<()>;
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#[doc(hidden)]
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fn start_dictionary(&mut self, entry_count: Option<usize>) -> io::Result<Self::DictWriter>;
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#[doc(hidden)]
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fn end_dictionary(&mut self, dict: Self::DictWriter) -> io::Result<()>;
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#[doc(hidden)]
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fn start_embedded(&mut self) -> io::Result<Self::EmbeddedWriter>;
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#[doc(hidden)]
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fn end_embedded(&mut self, ptr: Self::EmbeddedWriter) -> io::Result<()>;
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/// Flushes any buffered output.
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fn flush(&mut self) -> io::Result<()>;
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//---------------------------------------------------------------------------
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/// Writes [NestedValue] `v` to the output of this [Writer].
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fn write<N: NestedValue, Enc: DomainEncode<N::Embedded>>(
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&mut self,
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enc: &mut Enc,
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v: &N,
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) -> io::Result<()> {
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match v.annotations().maybe_slice() {
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None => {
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self.write_value(enc, v.value())?;
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}
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Some(anns) => {
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let mut a = self.start_annotations()?;
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let mut b = B::Type::default();
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for ann in anns {
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b.shift(Some(B::Item::Annotation));
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a.boundary(&b)?;
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a.write(enc, ann)?;
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}
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b.shift(Some(B::Item::AnnotatedValue));
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a.boundary(&b)?;
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a.write_value(enc, v.value())?;
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b.shift(None);
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a.boundary(&b)?;
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self.end_annotations(a)?;
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}
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}
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Ok(())
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}
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/// Writes [Value] `v` to the output of this [Writer].
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fn write_value<N: NestedValue, Enc: DomainEncode<N::Embedded>>(
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&mut self,
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enc: &mut Enc,
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v: &Value<N>,
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) -> io::Result<()> {
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match v {
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Value::Boolean(b) => self.write_bool(*b),
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Value::Double(Double(d)) => self.write_f64(*d),
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Value::SignedInteger(n) => match n.repr() {
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SignedIntegerRepr::I128(i) => self.write_i128(*i),
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SignedIntegerRepr::U128(u) => self.write_u128(*u),
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SignedIntegerRepr::Big(n) => self.write_int(n),
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},
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Value::String(s) => self.write_string(s),
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Value::ByteString(bs) => self.write_bytes(bs),
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Value::Symbol(s) => self.write_symbol(s),
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Value::Record(r) => {
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let mut c = self.start_record(Some(r.arity()))?;
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let mut b = B::start(B::Item::RecordLabel);
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c.boundary(&b)?;
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c.write(enc, r.label())?;
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for f in r.fields() {
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b.shift(Some(B::Item::RecordField));
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c.boundary(&b)?;
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c.write(enc, f)?;
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}
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b.shift(None);
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c.boundary(&b)?;
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self.end_record(c)
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}
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Value::Sequence(vs) => {
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let mut c = self.start_sequence(Some(vs.len()))?;
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let mut b = B::Type::default();
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for v in vs {
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b.shift(Some(B::Item::SequenceValue));
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c.boundary(&b)?;
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c.write(enc, v)?;
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}
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b.shift(None);
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c.boundary(&b)?;
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self.end_sequence(c)
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}
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Value::Set(vs) => {
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let mut c = self.start_set(Some(vs.len()))?;
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let mut b = B::Type::default();
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for v in vs {
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b.shift(Some(B::Item::SetValue));
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c.boundary(&b)?;
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c.write(enc, v)?;
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}
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b.shift(None);
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c.boundary(&b)?;
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self.end_set(c)
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}
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Value::Dictionary(vs) => {
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let mut c = self.start_dictionary(Some(vs.len()))?;
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let mut b = B::Type::default();
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for (k, v) in vs {
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b.shift(Some(B::Item::DictionaryKey));
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c.boundary(&b)?;
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c.write(enc, k)?;
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b.shift(Some(B::Item::DictionaryValue));
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c.boundary(&b)?;
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c.write(enc, v)?;
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}
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b.shift(None);
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c.boundary(&b)?;
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self.end_dictionary(c)
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}
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Value::Embedded(d) => {
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let mut c = self.start_embedded()?;
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enc.encode_embedded(&mut c, d)?;
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self.end_embedded(c)
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}
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}
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}
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}
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/// Writes a [varint](https://protobuf.dev/programming-guides/encoding/#varints) to `w`.
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/// Returns the number of bytes written.
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///
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/// ```text
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/// varint(n) = [n] if n < 128
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/// [(n & 127) | 128] ++ varint(n >> 7) if n ≥ 128
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/// ```
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pub fn varint<W: io::Write>(w: &mut W, mut v: u64) -> io::Result<usize> {
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let mut byte_count = 0;
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loop {
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byte_count += 1;
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if v < 128 {
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w.write_all(&[v as u8])?;
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return Ok(byte_count);
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} else {
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w.write_all(&[((v & 0x7f) + 128) as u8])?;
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v >>= 7;
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}
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}
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}
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