| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/value-bag-1.4.0/src/lib.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>lib.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../source-script.js"></script><script defer src="../../source-files.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../value_bag/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../value_bag/index.html"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="doccomment">//! Structured values. |
| //! |
| //! This crate contains the [`ValueBag`] type, a container for an anonymous structured value. |
| //! `ValueBag`s can be captured in various ways and then formatted, inspected, and serialized |
| //! without losing their original structure. |
| //! |
| //! The producer of a [`ValueBag`] may use a different strategy for capturing than the eventual |
| //! consumer. They don't need to coordinate directly. |
| |
| </span><span class="attribute">#![doc(html_root_url = <span class="string">"https://docs.rs/value-bag/1.4.0"</span>)] |
| #![no_std] |
| |
| </span><span class="comment">/* |
| # Crate design |
| |
| This library internally ties several frameworks together. The details of how |
| this is done are hidden from end-users. It looks roughly like this: |
| |
| ┌─────┐ ┌──────┐ |
| │sval2│ │serde1│ 1. libs on crates.io |
| └──┬──┘ └─┬─┬──┘ |
| ├──────────┘ │ |
| ┌───────▼──┐ ┌───▼───────┐ |
| │meta/sval2│ │meta/serde1│ 2. meta crates with features |
| └───────┬──┘ └───┬───────┘ |
| │ │ |
| ┌─────────────▼──┐ ┌───▼─────────────┐ |
| │internal/sval/v2◄─────┤internal/serde/v1│ 3. internal modules with `InternalVisitor` |
| └─────────────┬──┘ └───┬─────────────┘ |
| │ │ |
| ┌──────▼────────┬───▼────────────┐ |
| │Internal::Sval2│Internal::Serde1│ 4. variants in `Internal` enum |
| └───────────────┼────────────────┘ |
| │ |
| ┌───────────────────────▼────────────────────────┐ |
| │ValueBag::capture_sval2│ValueBag::capture_serde1│ 5. ctors on `ValueBag` |
| └───────────────────────┼────────────────────────┘ |
| │ |
| ┌───────────────────────▼───────────────────────────┐ |
| │impl Value for ValueBag│impl Serialize for ValueBag│ 6. trait impls on `ValueBag` |
| └───────────────────────┴───────────────────────────┘ |
| |
| ## 1. libs on crates.io |
| |
| These are the frameworks like `serde` or `sval`. |
| |
| ## 2. meta crates with features |
| |
| These are crates that are internal to `value-bag`. They depend on the public |
| framework and any utility crates that come along with it. They also expose |
| features for any other framework. This is done this way so `value-bag` can use |
| Cargo's `crate?/feature` syntax to conditionally add framework support. |
| |
| ## 3. internal modules with `InternalVisitor` |
| |
| These are modules in `value-bag` that integrate the framework using the |
| `InternalVisitor` trait. This makes it possible for that framework to cast |
| primitive values and pass-through any other framework. |
| |
| ## 4. variants in `Internal` enum |
| |
| These are individual variants on the `Internal` enum that the `ValueBag` |
| type wraps. Each framework has one or more variants in this enum. |
| |
| ## 5. ctors on `ValueBag` |
| |
| These are constructors for producers of `ValueBag`s that accept a value |
| implementing a serialization trait from a specific framework, like |
| `serde::Serialize` or `sval::Value`. |
| |
| ## 7. trait impls on `ValueBag` |
| |
| These are trait impls for consumers of `ValueBag`s that serialize the |
| underlying value, bridging it if it was produced for a different framework. |
| */ |
| |
| </span><span class="attribute">#[cfg(any(feature = <span class="string">"std"</span>, test))] |
| #[macro_use] |
| #[allow(unused_imports)] |
| </span><span class="kw">extern crate </span>std; |
| |
| <span class="attribute">#[cfg(all(not(test), feature = <span class="string">"alloc"</span>, not(feature = <span class="string">"std"</span>)))] |
| #[macro_use] |
| #[allow(unused_imports)] |
| </span><span class="kw">extern crate </span>core; |
| |
| <span class="attribute">#[cfg(all(not(test), feature = <span class="string">"alloc"</span>, not(feature = <span class="string">"std"</span>)))] |
| #[macro_use] |
| #[allow(unused_imports)] |
| </span><span class="kw">extern crate </span>alloc; |
| |
| <span class="attribute">#[cfg(all(not(test), feature = <span class="string">"alloc"</span>, not(feature = <span class="string">"std"</span>)))] |
| </span><span class="kw">mod </span>std { |
| <span class="kw">pub use crate</span>::{ |
| alloc::{boxed, string}, |
| core::<span class="kw-2">*</span>, |
| }; |
| } |
| |
| <span class="attribute">#[cfg(not(any(feature = <span class="string">"alloc"</span>, feature = <span class="string">"std"</span>, test)))] |
| #[macro_use] |
| #[allow(unused_imports)] |
| </span><span class="kw">extern crate </span>core <span class="kw">as </span>std; |
| |
| <span class="kw">mod </span>error; |
| <span class="kw">pub mod </span>fill; |
| <span class="kw">mod </span>impls; |
| <span class="kw">mod </span>internal; |
| <span class="kw">pub mod </span>visit; |
| |
| <span class="attribute">#[cfg(any(test, feature = <span class="string">"test"</span>))] |
| </span><span class="kw">pub mod </span>test; |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"owned"</span>)] |
| </span><span class="kw">mod </span>owned; |
| <span class="attribute">#[cfg(feature = <span class="string">"owned"</span>)] |
| </span><span class="kw">pub use </span><span class="self">self</span>::owned::<span class="kw-2">*</span>; |
| |
| <span class="kw">pub use </span><span class="self">self</span>::error::Error; |
| |
| <span class="doccomment">/// A dynamic structured value. |
| /// |
| /// # Capturing values |
| /// |
| /// There are a few ways to capture a value: |
| /// |
| /// - Using the `ValueBag::capture_*` and `ValueBag::from_*` methods. |
| /// - Using the standard `From` trait. |
| /// - Using the `Fill` API. |
| /// |
| /// ## Using the `ValueBag::capture_*` methods |
| /// |
| /// `ValueBag` offers a few constructor methods that capture values of different kinds. |
| /// These methods require a `T: 'static` to support downcasting. |
| /// |
| /// ``` |
| /// use value_bag::ValueBag; |
| /// |
| /// let value = ValueBag::capture_debug(&42i32); |
| /// |
| /// assert_eq!(Some(42), value.to_i64()); |
| /// ``` |
| /// |
| /// Capturing a value using these methods will retain type information so that |
| /// the contents of the bag can be serialized using an appropriate type. |
| /// |
| /// For cases where the `'static` bound can't be satisfied, there's also a few |
| /// constructors that exclude it. |
| /// |
| /// ``` |
| /// # use std::fmt::Debug; |
| /// use value_bag::ValueBag; |
| /// |
| /// let value = ValueBag::from_debug(&42i32); |
| /// |
| /// assert_eq!(None, value.to_i64()); |
| /// ``` |
| /// |
| /// These `ValueBag::from_*` methods are lossy though and `ValueBag::capture_*` should be preferred. |
| /// |
| /// ## Using the standard `From` trait |
| /// |
| /// Primitive types can be converted into a `ValueBag` using the standard `From` trait. |
| /// |
| /// ``` |
| /// use value_bag::ValueBag; |
| /// |
| /// let value = ValueBag::from(42i32); |
| /// |
| /// assert_eq!(Some(42), value.to_i64()); |
| /// ``` |
| /// |
| /// ## Using the `Fill` API |
| /// |
| /// The [`fill`] module provides a way to bridge APIs that may not be directly |
| /// compatible with other constructor methods. |
| /// |
| /// The `Fill` trait is automatically implemented for closures, so can usually |
| /// be used in libraries that can't implement the trait themselves. |
| /// |
| /// ``` |
| /// use value_bag::{ValueBag, fill::Slot}; |
| /// |
| /// let value = ValueBag::from_fill(&|slot: Slot| { |
| /// #[derive(Debug)] |
| /// struct MyShortLivedValue; |
| /// |
| /// slot.fill_debug(&MyShortLivedValue) |
| /// }); |
| /// |
| /// assert_eq!("MyShortLivedValue", format!("{:?}", value)); |
| /// ``` |
| /// |
| /// The trait can also be implemented manually: |
| /// |
| /// ``` |
| /// # use std::fmt::Debug; |
| /// use value_bag::{ValueBag, Error, fill::{Slot, Fill}}; |
| /// |
| /// struct FillDebug; |
| /// |
| /// impl Fill for FillDebug { |
| /// fn fill(&self, slot: Slot) -> Result<(), Error> { |
| /// slot.fill_debug(&42i32 as &dyn Debug) |
| /// } |
| /// } |
| /// |
| /// let value = ValueBag::from_fill(&FillDebug); |
| /// |
| /// assert_eq!(None, value.to_i64()); |
| /// ``` |
| /// |
| /// # Inspecting values |
| /// |
| /// Once you have a `ValueBag` there are also a few ways to inspect it: |
| /// |
| /// - Using `std::fmt` |
| /// - Using `sval` |
| /// - Using `serde` |
| /// - Using the `ValueBag::visit` method. |
| /// - Using the `ValueBag::to_*` methods. |
| /// - Using the `ValueBag::downcast_ref` method. |
| /// |
| /// ## Using the `ValueBag::visit` method |
| /// |
| /// The [`visit`] module provides a simple visitor API that can be used to inspect |
| /// the structure of primitives stored in a `ValueBag`. |
| /// More complex datatypes can then be handled using `std::fmt`, `sval`, or `serde`. |
| /// |
| /// ``` |
| /// #[cfg(not(feature = "std"))] fn main() {} |
| /// #[cfg(feature = "std")] |
| /// # fn main() -> Result<(), Box<dyn std::error::Error>> { |
| /// # fn escape(buf: &[u8]) -> &[u8] { buf } |
| /// # fn itoa_fmt<T>(num: T) -> Vec<u8> { vec![] } |
| /// # fn ryu_fmt<T>(num: T) -> Vec<u8> { vec![] } |
| /// # use std::io::Write; |
| /// use value_bag::{ValueBag, Error, visit::Visit}; |
| /// |
| /// // Implement some simple custom serialization |
| /// struct MyVisit(Vec<u8>); |
| /// impl<'v> Visit<'v> for MyVisit { |
| /// fn visit_any(&mut self, v: ValueBag) -> Result<(), Error> { |
| /// // Fallback to `Debug` if we didn't visit the value specially |
| /// write!(&mut self.0, "{:?}", v).map_err(|_| Error::msg("failed to write value")) |
| /// } |
| /// |
| /// fn visit_u64(&mut self, v: u64) -> Result<(), Error> { |
| /// self.0.extend_from_slice(itoa_fmt(v).as_slice()); |
| /// Ok(()) |
| /// } |
| /// |
| /// fn visit_i64(&mut self, v: i64) -> Result<(), Error> { |
| /// self.0.extend_from_slice(itoa_fmt(v).as_slice()); |
| /// Ok(()) |
| /// } |
| /// |
| /// fn visit_f64(&mut self, v: f64) -> Result<(), Error> { |
| /// self.0.extend_from_slice(ryu_fmt(v).as_slice()); |
| /// Ok(()) |
| /// } |
| /// |
| /// fn visit_str(&mut self, v: &str) -> Result<(), Error> { |
| /// self.0.push(b'\"'); |
| /// self.0.extend_from_slice(escape(v.as_bytes())); |
| /// self.0.push(b'\"'); |
| /// Ok(()) |
| /// } |
| /// |
| /// fn visit_bool(&mut self, v: bool) -> Result<(), Error> { |
| /// self.0.extend_from_slice(if v { b"true" } else { b"false" }); |
| /// Ok(()) |
| /// } |
| /// } |
| /// |
| /// let value = ValueBag::from(42i64); |
| /// |
| /// let mut visitor = MyVisit(vec![]); |
| /// value.visit(&mut visitor)?; |
| /// # Ok(()) |
| /// # } |
| /// ``` |
| /// |
| /// ## Using `std::fmt` |
| /// |
| /// Any `ValueBag` can be formatted using the `std::fmt` machinery as either `Debug` |
| /// or `Display`. |
| /// |
| /// ``` |
| /// use value_bag::ValueBag; |
| /// |
| /// let value = ValueBag::from(true); |
| /// |
| /// assert_eq!("true", format!("{:?}", value)); |
| /// ``` |
| /// |
| /// ## Using `sval` |
| /// |
| /// When the `sval2` feature is enabled, any `ValueBag` can be serialized using `sval`. |
| /// This makes it possible to visit any typed structure captured in the `ValueBag`, |
| /// including complex datatypes like maps and sequences. |
| /// |
| /// `sval` doesn't need to allocate so can be used in no-std environments. |
| /// |
| /// First, enable the `sval2` feature in your `Cargo.toml`: |
| /// |
| /// ```toml |
| /// [dependencies.value-bag] |
| /// features = ["sval2"] |
| /// ``` |
| /// |
| /// Then stream the contents of the `ValueBag` using `sval`. |
| /// |
| /// ``` |
| /// # #[cfg(not(all(feature = "std", feature = "sval2")))] fn main() {} |
| /// # #[cfg(all(feature = "std", feature = "sval2"))] |
| /// # fn main() -> Result<(), Box<dyn std::error::Error>> { |
| /// # use value_bag_sval2::json as sval_json; |
| /// use value_bag::ValueBag; |
| /// |
| /// let value = ValueBag::from(42i64); |
| /// let json = sval_json::stream_to_string(value)?; |
| /// # Ok(()) |
| /// # } |
| /// ``` |
| /// |
| /// ## Using `serde` |
| /// |
| /// When the `serde1` feature is enabled, any `ValueBag` can be serialized using `serde`. |
| /// This makes it possible to visit any typed structure captured in the `ValueBag`, |
| /// including complex datatypes like maps and sequences. |
| /// |
| /// `serde` needs a few temporary allocations, so also brings in the `std` feature. |
| /// |
| /// First, enable the `serde1` feature in your `Cargo.toml`: |
| /// |
| /// ```toml |
| /// [dependencies.value-bag] |
| /// features = ["serde1"] |
| /// ``` |
| /// |
| /// Then stream the contents of the `ValueBag` using `serde`. |
| /// |
| /// ``` |
| /// # #[cfg(not(all(feature = "std", feature = "serde1")))] fn main() {} |
| /// # #[cfg(all(feature = "std", feature = "serde1"))] |
| /// # fn main() -> Result<(), Box<dyn std::error::Error>> { |
| /// # use value_bag_serde1::json as serde_json; |
| /// use value_bag::ValueBag; |
| /// |
| /// let value = ValueBag::from(42i64); |
| /// let json = serde_json::to_string(&value)?; |
| /// # Ok(()) |
| /// # } |
| /// ``` |
| /// |
| /// Also see [`serde.rs`](https://serde.rs) for more examples of writing your own serializers. |
| /// |
| /// ## Using the `ValueBag::to_*` methods |
| /// |
| /// `ValueBag` provides a set of methods for attempting to pull a concrete value out. |
| /// These are useful for ad-hoc analysis but aren't intended for exhaustively serializing |
| /// the contents of a `ValueBag`. |
| /// |
| /// ``` |
| /// use value_bag::ValueBag; |
| /// |
| /// let value = ValueBag::capture_display(&42u64); |
| /// |
| /// assert_eq!(Some(42u64), value.to_u64()); |
| /// ``` |
| /// |
| /// ## Using the `ValueBag::downcast_ref` method |
| /// |
| /// When a `ValueBag` is created using one of the `capture_*` constructors, it can be downcast |
| /// back to its original value. |
| /// This can also be useful for ad-hoc analysis where there's a common possible non-primitive |
| /// type that could be captured. |
| /// |
| /// ``` |
| /// # #[derive(Debug)] struct SystemTime; |
| /// # fn now() -> SystemTime { SystemTime } |
| /// use value_bag::ValueBag; |
| /// |
| /// let timestamp = now(); |
| /// let value = ValueBag::capture_debug(&timestamp); |
| /// |
| /// assert!(value.downcast_ref::<SystemTime>().is_some()); |
| /// ``` |
| </span><span class="attribute">#[derive(Clone)] |
| </span><span class="kw">pub struct </span>ValueBag<<span class="lifetime">'v</span>> { |
| inner: internal::Internal<<span class="lifetime">'v</span>>, |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'v</span>> ValueBag<<span class="lifetime">'v</span>> { |
| <span class="doccomment">/// Get a `ValueBag` from a reference to a `ValueBag`. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>by_ref<<span class="lifetime">'u</span>>(<span class="kw-2">&</span><span class="lifetime">'u </span><span class="self">self</span>) -> ValueBag<<span class="lifetime">'u</span>> { |
| ValueBag { |
| inner: <span class="self">self</span>.inner.by_ref(), |
| } |
| } |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>tests { |
| <span class="kw">use super</span>::<span class="kw-2">*</span>; |
| <span class="kw">use </span><span class="kw">crate</span>::std::mem; |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"inline-i128"</span>)] |
| </span><span class="kw">const </span>SIZE_LIMIT_U64: usize = <span class="number">4</span>; |
| <span class="attribute">#[cfg(not(feature = <span class="string">"inline-i128"</span>))] |
| </span><span class="kw">const </span>SIZE_LIMIT_U64: usize = <span class="number">3</span>; |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>value_bag_size() { |
| <span class="kw">let </span>size = mem::size_of::<ValueBag<<span class="lifetime">'_</span>>>(); |
| <span class="kw">let </span>limit = mem::size_of::<u64>() * SIZE_LIMIT_U64; |
| |
| <span class="kw">if </span>size > limit { |
| <span class="macro">panic!</span>( |
| <span class="string">"`ValueBag` size ({} bytes) is too large (expected up to {} bytes)"</span>, |
| size, limit, |
| ); |
| } |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="value_bag" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |