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+//! Sources for key-value pairs.
+
+#[cfg(feature = "kv_unstable_sval")]
+extern crate sval;
+#[cfg(feature = "kv_unstable_sval")]
+extern crate sval_ref;
+
+#[cfg(feature = "kv_unstable_serde")]
+extern crate serde;
+
+use kv::{Error, Key, ToKey, ToValue, Value};
+use std::fmt;
+
+/// A source of key-value pairs.
+///
+/// The source may be a single pair, a set of pairs, or a filter over a set of pairs.
+/// Use the [`Visitor`](trait.Visitor.html) trait to inspect the structured data
+/// in a source.
+pub trait Source {
+ /// Visit key-value pairs.
+ ///
+ /// A source doesn't have to guarantee any ordering or uniqueness of key-value pairs.
+ /// If the given visitor returns an error then the source may early-return with it,
+ /// even if there are more key-value pairs.
+ ///
+ /// # Implementation notes
+ ///
+ /// A source should yield the same key-value pairs to a subsequent visitor unless
+ /// that visitor itself fails.
+ fn visit<'kvs>(&'kvs self, visitor: &mut dyn Visitor<'kvs>) -> Result<(), Error>;
+
+ /// Get the value for a given key.
+ ///
+ /// If the key appears multiple times in the source then which key is returned
+ /// is implementation specific.
+ ///
+ /// # Implementation notes
+ ///
+ /// A source that can provide a more efficient implementation of this method
+ /// should override it.
+ #[cfg(not(test))]
+ fn get<'v>(&'v self, key: Key) -> Option<Value<'v>> {
+ get_default(self, key)
+ }
+
+ #[cfg(test)]
+ fn get<'v>(&'v self, key: Key) -> Option<Value<'v>>;
+
+ /// Count the number of key-value pairs that can be visited.
+ ///
+ /// # Implementation notes
+ ///
+ /// A source that knows the number of key-value pairs upfront may provide a more
+ /// efficient implementation.
+ ///
+ /// A subsequent call to `visit` should yield the same number of key-value pairs
+ /// to the visitor, unless that visitor fails part way through.
+ #[cfg(not(test))]
+ fn count(&self) -> usize {
+ count_default(self)
+ }
+
+ #[cfg(test)]
+ fn count(&self) -> usize;
+}
+
+/// The default implemention of `Source::get`
+pub(crate) fn get_default<'v>(source: &'v (impl Source + ?Sized), key: Key) -> Option<Value<'v>> {
+ struct Get<'k, 'v> {
+ key: Key<'k>,
+ found: Option<Value<'v>>,
+ }
+
+ impl<'k, 'kvs> Visitor<'kvs> for Get<'k, 'kvs> {
+ fn visit_pair(&mut self, key: Key<'kvs>, value: Value<'kvs>) -> Result<(), Error> {
+ if self.key == key {
+ self.found = Some(value);
+ }
+
+ Ok(())
+ }
+ }
+
+ let mut get = Get { key, found: None };
+
+ let _ = source.visit(&mut get);
+ get.found
+}
+
+/// The default implementation of `Source::count`.
+pub(crate) fn count_default(source: impl Source) -> usize {
+ struct Count(usize);
+
+ impl<'kvs> Visitor<'kvs> for Count {
+ fn visit_pair(&mut self, _: Key<'kvs>, _: Value<'kvs>) -> Result<(), Error> {
+ self.0 += 1;
+
+ Ok(())
+ }
+ }
+
+ let mut count = Count(0);
+ let _ = source.visit(&mut count);
+ count.0
+}
+
+impl<'a, T> Source for &'a T
+where
+ T: Source + ?Sized,
+{
+ fn visit<'kvs>(&'kvs self, visitor: &mut dyn Visitor<'kvs>) -> Result<(), Error> {
+ Source::visit(&**self, visitor)
+ }
+
+ fn get<'v>(&'v self, key: Key) -> Option<Value<'v>> {
+ Source::get(&**self, key)
+ }
+
+ fn count(&self) -> usize {
+ Source::count(&**self)
+ }
+}
+
+impl<K, V> Source for (K, V)
+where
+ K: ToKey,
+ V: ToValue,
+{
+ fn visit<'kvs>(&'kvs self, visitor: &mut dyn Visitor<'kvs>) -> Result<(), Error> {
+ visitor.visit_pair(self.0.to_key(), self.1.to_value())
+ }
+
+ fn get<'v>(&'v self, key: Key) -> Option<Value<'v>> {
+ if self.0.to_key() == key {
+ Some(self.1.to_value())
+ } else {
+ None
+ }
+ }
+
+ fn count(&self) -> usize {
+ 1
+ }
+}
+
+impl<S> Source for [S]
+where
+ S: Source,
+{
+ fn visit<'kvs>(&'kvs self, visitor: &mut dyn Visitor<'kvs>) -> Result<(), Error> {
+ for source in self {
+ source.visit(visitor)?;
+ }
+
+ Ok(())
+ }
+
+ fn get<'v>(&'v self, key: Key) -> Option<Value<'v>> {
+ for source in self {
+ if let Some(found) = source.get(key.clone()) {
+ return Some(found);
+ }
+ }
+
+ None
+ }
+
+ fn count(&self) -> usize {
+ self.len()
+ }
+}
+
+impl<S> Source for Option<S>
+where
+ S: Source,
+{
+ fn visit<'kvs>(&'kvs self, visitor: &mut dyn Visitor<'kvs>) -> Result<(), Error> {
+ if let Some(ref source) = *self {
+ source.visit(visitor)?;
+ }
+
+ Ok(())
+ }
+
+ fn get<'v>(&'v self, key: Key) -> Option<Value<'v>> {
+ self.as_ref().and_then(|s| s.get(key))
+ }
+
+ fn count(&self) -> usize {
+ self.as_ref().map(Source::count).unwrap_or(0)
+ }
+}
+
+/// A visitor for the key-value pairs in a [`Source`](trait.Source.html).
+pub trait Visitor<'kvs> {
+ /// Visit a key-value pair.
+ fn visit_pair(&mut self, key: Key<'kvs>, value: Value<'kvs>) -> Result<(), Error>;
+}
+
+impl<'a, 'kvs, T> Visitor<'kvs> for &'a mut T
+where
+ T: Visitor<'kvs> + ?Sized,
+{
+ fn visit_pair(&mut self, key: Key<'kvs>, value: Value<'kvs>) -> Result<(), Error> {
+ (**self).visit_pair(key, value)
+ }
+}
+
+impl<'a, 'b: 'a, 'kvs> Visitor<'kvs> for fmt::DebugMap<'a, 'b> {
+ fn visit_pair(&mut self, key: Key<'kvs>, value: Value<'kvs>) -> Result<(), Error> {
+ self.entry(&key, &value);
+ Ok(())
+ }
+}
+
+impl<'a, 'b: 'a, 'kvs> Visitor<'kvs> for fmt::DebugList<'a, 'b> {
+ fn visit_pair(&mut self, key: Key<'kvs>, value: Value<'kvs>) -> Result<(), Error> {
+ self.entry(&(key, value));
+ Ok(())
+ }
+}
+
+impl<'a, 'b: 'a, 'kvs> Visitor<'kvs> for fmt::DebugSet<'a, 'b> {
+ fn visit_pair(&mut self, key: Key<'kvs>, value: Value<'kvs>) -> Result<(), Error> {
+ self.entry(&(key, value));
+ Ok(())
+ }
+}
+
+impl<'a, 'b: 'a, 'kvs> Visitor<'kvs> for fmt::DebugTuple<'a, 'b> {
+ fn visit_pair(&mut self, key: Key<'kvs>, value: Value<'kvs>) -> Result<(), Error> {
+ self.field(&key);
+ self.field(&value);
+ Ok(())
+ }
+}
+
+#[cfg(feature = "std")]
+mod std_support {
+ use super::*;
+ use std::borrow::Borrow;
+ use std::collections::{BTreeMap, HashMap};
+ use std::hash::{BuildHasher, Hash};
+
+ impl<S> Source for Box<S>
+ where
+ S: Source + ?Sized,
+ {
+ fn visit<'kvs>(&'kvs self, visitor: &mut dyn Visitor<'kvs>) -> Result<(), Error> {
+ Source::visit(&**self, visitor)
+ }
+
+ fn get<'v>(&'v self, key: Key) -> Option<Value<'v>> {
+ Source::get(&**self, key)
+ }
+
+ fn count(&self) -> usize {
+ Source::count(&**self)
+ }
+ }
+
+ impl<S> Source for Vec<S>
+ where
+ S: Source,
+ {
+ fn visit<'kvs>(&'kvs self, visitor: &mut dyn Visitor<'kvs>) -> Result<(), Error> {
+ Source::visit(&**self, visitor)
+ }
+
+ fn get<'v>(&'v self, key: Key) -> Option<Value<'v>> {
+ Source::get(&**self, key)
+ }
+
+ fn count(&self) -> usize {
+ Source::count(&**self)
+ }
+ }
+
+ impl<'kvs, V> Visitor<'kvs> for Box<V>
+ where
+ V: Visitor<'kvs> + ?Sized,
+ {
+ fn visit_pair(&mut self, key: Key<'kvs>, value: Value<'kvs>) -> Result<(), Error> {
+ (**self).visit_pair(key, value)
+ }
+ }
+
+ impl<K, V, S> Source for HashMap<K, V, S>
+ where
+ K: ToKey + Borrow<str> + Eq + Hash,
+ V: ToValue,
+ S: BuildHasher,
+ {
+ fn visit<'kvs>(&'kvs self, visitor: &mut dyn Visitor<'kvs>) -> Result<(), Error> {
+ for (key, value) in self {
+ visitor.visit_pair(key.to_key(), value.to_value())?;
+ }
+ Ok(())
+ }
+
+ fn get<'v>(&'v self, key: Key) -> Option<Value<'v>> {
+ HashMap::get(self, key.as_str()).map(|v| v.to_value())
+ }
+
+ fn count(&self) -> usize {
+ self.len()
+ }
+ }
+
+ impl<K, V> Source for BTreeMap<K, V>
+ where
+ K: ToKey + Borrow<str> + Ord,
+ V: ToValue,
+ {
+ fn visit<'kvs>(&'kvs self, visitor: &mut dyn Visitor<'kvs>) -> Result<(), Error> {
+ for (key, value) in self {
+ visitor.visit_pair(key.to_key(), value.to_value())?;
+ }
+ Ok(())
+ }
+
+ fn get<'v>(&'v self, key: Key) -> Option<Value<'v>> {
+ BTreeMap::get(self, key.as_str()).map(|v| v.to_value())
+ }
+
+ fn count(&self) -> usize {
+ self.len()
+ }
+ }
+
+ #[cfg(test)]
+ mod tests {
+ use super::*;
+ use kv::value::tests::Token;
+ use std::collections::{BTreeMap, HashMap};
+
+ #[test]
+ fn count() {
+ assert_eq!(1, Source::count(&Box::new(("a", 1))));
+ assert_eq!(2, Source::count(&vec![("a", 1), ("b", 2)]));
+ }
+
+ #[test]
+ fn get() {
+ let source = vec![("a", 1), ("b", 2), ("a", 1)];
+ assert_eq!(
+ Token::I64(1),
+ Source::get(&source, Key::from_str("a")).unwrap().to_token()
+ );
+
+ let source = Box::new(Option::None::<(&str, i32)>);
+ assert!(Source::get(&source, Key::from_str("a")).is_none());
+ }
+
+ #[test]
+ fn hash_map() {
+ let mut map = HashMap::new();
+ map.insert("a", 1);
+ map.insert("b", 2);
+
+ assert_eq!(2, Source::count(&map));
+ assert_eq!(
+ Token::I64(1),
+ Source::get(&map, Key::from_str("a")).unwrap().to_token()
+ );
+ }
+
+ #[test]
+ fn btree_map() {
+ let mut map = BTreeMap::new();
+ map.insert("a", 1);
+ map.insert("b", 2);
+
+ assert_eq!(2, Source::count(&map));
+ assert_eq!(
+ Token::I64(1),
+ Source::get(&map, Key::from_str("a")).unwrap().to_token()
+ );
+ }
+ }
+}
+
+/// The result of calling `Source::as_map`.
+pub struct AsMap<S>(S);
+
+/// Visit this source as a map.
+pub fn as_map<S>(source: S) -> AsMap<S>
+where
+ S: Source,
+{
+ AsMap(source)
+}
+
+impl<S> Source for AsMap<S>
+where
+ S: Source,
+{
+ fn visit<'kvs>(&'kvs self, visitor: &mut dyn Visitor<'kvs>) -> Result<(), Error> {
+ self.0.visit(visitor)
+ }
+
+ fn get<'v>(&'v self, key: Key) -> Option<Value<'v>> {
+ self.0.get(key)
+ }
+
+ fn count(&self) -> usize {
+ self.0.count()
+ }
+}
+
+impl<S> fmt::Debug for AsMap<S>
+where
+ S: Source,
+{
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ let mut f = f.debug_map();
+ self.0.visit(&mut f).map_err(|_| fmt::Error)?;
+ f.finish()
+ }
+}
+
+/// The result of calling `Source::as_list`
+pub struct AsList<S>(S);
+
+/// Visit this source as a list.
+pub fn as_list<S>(source: S) -> AsList<S>
+where
+ S: Source,
+{
+ AsList(source)
+}
+
+impl<S> Source for AsList<S>
+where
+ S: Source,
+{
+ fn visit<'kvs>(&'kvs self, visitor: &mut dyn Visitor<'kvs>) -> Result<(), Error> {
+ self.0.visit(visitor)
+ }
+
+ fn get<'v>(&'v self, key: Key) -> Option<Value<'v>> {
+ self.0.get(key)
+ }
+
+ fn count(&self) -> usize {
+ self.0.count()
+ }
+}
+
+impl<S> fmt::Debug for AsList<S>
+where
+ S: Source,
+{
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ let mut f = f.debug_list();
+ self.0.visit(&mut f).map_err(|_| fmt::Error)?;
+ f.finish()
+ }
+}
+
+#[cfg(feature = "kv_unstable_sval")]
+mod sval_support {
+ use super::*;
+
+ impl<S> self::sval::Value for AsMap<S>
+ where
+ S: Source,
+ {
+ fn stream<'sval, SV: self::sval::Stream<'sval> + ?Sized>(
+ &'sval self,
+ stream: &mut SV,
+ ) -> self::sval::Result {
+ struct StreamVisitor<'a, V: ?Sized>(&'a mut V);
+
+ impl<'a, 'kvs, V: self::sval::Stream<'kvs> + ?Sized> Visitor<'kvs> for StreamVisitor<'a, V> {
+ fn visit_pair(&mut self, key: Key<'kvs>, value: Value<'kvs>) -> Result<(), Error> {
+ self.0
+ .map_key_begin()
+ .map_err(|_| Error::msg("failed to stream map key"))?;
+ sval_ref::stream_ref(self.0, key)
+ .map_err(|_| Error::msg("failed to stream map key"))?;
+ self.0
+ .map_key_end()
+ .map_err(|_| Error::msg("failed to stream map key"))?;
+
+ self.0
+ .map_value_begin()
+ .map_err(|_| Error::msg("failed to stream map value"))?;
+ sval_ref::stream_ref(self.0, value)
+ .map_err(|_| Error::msg("failed to stream map value"))?;
+ self.0
+ .map_value_end()
+ .map_err(|_| Error::msg("failed to stream map value"))?;
+
+ Ok(())
+ }
+ }
+
+ stream
+ .map_begin(Some(self.count()))
+ .map_err(|_| self::sval::Error::new())?;
+
+ self.visit(&mut StreamVisitor(stream))
+ .map_err(|_| self::sval::Error::new())?;
+
+ stream.map_end().map_err(|_| self::sval::Error::new())
+ }
+ }
+
+ impl<S> self::sval::Value for AsList<S>
+ where
+ S: Source,
+ {
+ fn stream<'sval, SV: self::sval::Stream<'sval> + ?Sized>(
+ &'sval self,
+ stream: &mut SV,
+ ) -> self::sval::Result {
+ struct StreamVisitor<'a, V: ?Sized>(&'a mut V);
+
+ impl<'a, 'kvs, V: self::sval::Stream<'kvs> + ?Sized> Visitor<'kvs> for StreamVisitor<'a, V> {
+ fn visit_pair(&mut self, key: Key<'kvs>, value: Value<'kvs>) -> Result<(), Error> {
+ self.0
+ .seq_value_begin()
+ .map_err(|_| Error::msg("failed to stream seq value"))?;
+ self::sval_ref::stream_ref(self.0, (key, value))
+ .map_err(|_| Error::msg("failed to stream seq value"))?;
+ self.0
+ .seq_value_end()
+ .map_err(|_| Error::msg("failed to stream seq value"))?;
+
+ Ok(())
+ }
+ }
+
+ stream
+ .seq_begin(Some(self.count()))
+ .map_err(|_| self::sval::Error::new())?;
+
+ self.visit(&mut StreamVisitor(stream))
+ .map_err(|_| self::sval::Error::new())?;
+
+ stream.seq_end().map_err(|_| self::sval::Error::new())
+ }
+ }
+
+ #[cfg(test)]
+ mod tests {
+ extern crate sval_derive;
+
+ use super::*;
+
+ use self::sval_derive::Value;
+
+ use crate::kv::source;
+
+ #[test]
+ fn derive_stream() {
+ #[derive(Value)]
+ pub struct MyRecordAsMap<'a> {
+ msg: &'a str,
+ kvs: source::AsMap<&'a dyn Source>,
+ }
+
+ #[derive(Value)]
+ pub struct MyRecordAsList<'a> {
+ msg: &'a str,
+ kvs: source::AsList<&'a dyn Source>,
+ }
+ }
+ }
+}
+
+#[cfg(feature = "kv_unstable_serde")]
+pub mod as_map {
+ //! `serde` adapters for serializing a `Source` as a map.
+
+ use super::*;
+
+ use self::serde::{Serialize, Serializer};
+
+ /// Serialize a `Source` as a map.
+ pub fn serialize<T, S>(source: &T, serializer: S) -> Result<S::Ok, S::Error>
+ where
+ T: Source,
+ S: Serializer,
+ {
+ as_map(source).serialize(serializer)
+ }
+}
+
+#[cfg(feature = "kv_unstable_serde")]
+pub mod as_list {
+ //! `serde` adapters for serializing a `Source` as a list.
+
+ use super::*;
+
+ use self::serde::{Serialize, Serializer};
+
+ /// Serialize a `Source` as a list.
+ pub fn serialize<T, S>(source: &T, serializer: S) -> Result<S::Ok, S::Error>
+ where
+ T: Source,
+ S: Serializer,
+ {
+ as_list(source).serialize(serializer)
+ }
+}
+
+#[cfg(feature = "kv_unstable_serde")]
+mod serde_support {
+ use super::*;
+
+ use self::serde::ser::{Error as SerError, Serialize, SerializeMap, SerializeSeq, Serializer};
+
+ impl<T> Serialize for AsMap<T>
+ where
+ T: Source,
+ {
+ fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+ where
+ S: Serializer,
+ {
+ struct SerializerVisitor<'a, S>(&'a mut S);
+
+ impl<'a, 'kvs, S> Visitor<'kvs> for SerializerVisitor<'a, S>
+ where
+ S: SerializeMap,
+ {
+ fn visit_pair(&mut self, key: Key<'kvs>, value: Value<'kvs>) -> Result<(), Error> {
+ self.0
+ .serialize_entry(&key, &value)
+ .map_err(|_| Error::msg("failed to serialize map entry"))?;
+ Ok(())
+ }
+ }
+
+ let mut map = serializer.serialize_map(Some(self.count()))?;
+
+ self.visit(&mut SerializerVisitor(&mut map))
+ .map_err(|_| S::Error::custom("failed to visit key-values"))?;
+
+ map.end()
+ }
+ }
+
+ impl<T> Serialize for AsList<T>
+ where
+ T: Source,
+ {
+ fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+ where
+ S: Serializer,
+ {
+ struct SerializerVisitor<'a, S>(&'a mut S);
+
+ impl<'a, 'kvs, S> Visitor<'kvs> for SerializerVisitor<'a, S>
+ where
+ S: SerializeSeq,
+ {
+ fn visit_pair(&mut self, key: Key<'kvs>, value: Value<'kvs>) -> Result<(), Error> {
+ self.0
+ .serialize_element(&(key, value))
+ .map_err(|_| Error::msg("failed to serialize seq entry"))?;
+ Ok(())
+ }
+ }
+
+ let mut seq = serializer.serialize_seq(Some(self.count()))?;
+
+ self.visit(&mut SerializerVisitor(&mut seq))
+ .map_err(|_| S::Error::custom("failed to visit seq"))?;
+
+ seq.end()
+ }
+ }
+
+ #[cfg(test)]
+ mod tests {
+ use super::*;
+
+ use self::serde::Serialize;
+
+ use crate::kv::source;
+
+ #[test]
+ fn derive_serialize() {
+ #[derive(Serialize)]
+ pub struct MyRecordAsMap<'a> {
+ msg: &'a str,
+ #[serde(flatten)]
+ #[serde(with = "source::as_map")]
+ kvs: &'a dyn Source,
+ }
+
+ #[derive(Serialize)]
+ pub struct MyRecordAsList<'a> {
+ msg: &'a str,
+ #[serde(flatten)]
+ #[serde(with = "source::as_list")]
+ kvs: &'a dyn Source,
+ }
+ }
+ }
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+ use kv::value::tests::Token;
+
+ #[test]
+ fn source_is_object_safe() {
+ fn _check(_: &dyn Source) {}
+ }
+
+ #[test]
+ fn visitor_is_object_safe() {
+ fn _check(_: &dyn Visitor) {}
+ }
+
+ #[test]
+ fn count() {
+ struct OnePair {
+ key: &'static str,
+ value: i32,
+ }
+
+ impl Source for OnePair {
+ fn visit<'kvs>(&'kvs self, visitor: &mut dyn Visitor<'kvs>) -> Result<(), Error> {
+ visitor.visit_pair(self.key.to_key(), self.value.to_value())
+ }
+
+ fn get<'v>(&'v self, key: Key) -> Option<Value<'v>> {
+ get_default(self, key)
+ }
+
+ fn count(&self) -> usize {
+ count_default(self)
+ }
+ }
+
+ assert_eq!(1, Source::count(&("a", 1)));
+ assert_eq!(2, Source::count(&[("a", 1), ("b", 2)] as &[_]));
+ assert_eq!(0, Source::count(&Option::None::<(&str, i32)>));
+ assert_eq!(1, Source::count(&OnePair { key: "a", value: 1 }));
+ }
+
+ #[test]
+ fn get() {
+ let source = &[("a", 1), ("b", 2), ("a", 1)] as &[_];
+ assert_eq!(
+ Token::I64(1),
+ Source::get(source, Key::from_str("a")).unwrap().to_token()
+ );
+ assert_eq!(
+ Token::I64(2),
+ Source::get(source, Key::from_str("b")).unwrap().to_token()
+ );
+ assert!(Source::get(&source, Key::from_str("c")).is_none());
+
+ let source = Option::None::<(&str, i32)>;
+ assert!(Source::get(&source, Key::from_str("a")).is_none());
+ }
+
+ #[test]
+ fn as_map() {
+ let _ = crate::kv::source::as_map(("a", 1));
+ let _ = crate::kv::source::as_map(&("a", 1) as &dyn Source);
+ }
+
+ #[test]
+ fn as_list() {
+ let _ = crate::kv::source::as_list(("a", 1));
+ let _ = crate::kv::source::as_list(&("a", 1) as &dyn Source);
+ }
+}
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