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use crate::TransducerError; use std::marker::PhantomData; use rayon::iter::plumbing::*; use rayon::iter::*; #[cfg(feature = "use_scroll")] use scroll::{ ctx::{self, SizeWith}, Pread, }; /// A lazy transducer transforms `n` elements from a source type into an output type. /// /// The transformer is called the transducer, which receives the original source input, and an index /// corresponding to the `i`th element, and returns the corresponding `i`th element out of that source. /// /// Importantly, lazy transducers are: /// /// 1. Lazy - it never parses any elements unless you request it to do so /// 2. Iterable - one can iterate over every element /// 3. Indexable - accessing an element is O(1) /// 4. Parallel - one can iterate in parallel over every element /// /// # Basic Example /// /// We need to provide a data source, the number of elements in the data source, and the means of /// extracting the elements out of the data source (the transducer). /// /// For a simple case, we can consider a backing array of `u32`s, which we cast to `u64`s. /// /// ```rust /// extern crate lazy_transducer; /// use lazy_transducer::LazyTransducer; /// /// # fn main() { /// let data = [0xdeadbeefu32, 0xcafed00d]; /// let lt: LazyTransducer<&[u32], u64> = LazyTransducer::new(&data, 2, |input, idx| input[idx] as u64); /// /// let cafedood = lt.get(1).expect("has 2 elements"); /// assert_eq!(cafedood, 0xcafed00d); /// /// for (i, elem) in lt.into_iter().enumerate() { /// println!("{}: {}", i, elem); /// } /// # } /// ``` /// /// # Advanced Example /// /// This example uses the [bincode](https://github.com/TyOverby/bincode) binary serializer as /// its transducer. /// /// ```rust /// extern crate lazy_transducer; /// #[macro_use] /// extern crate serde_derive; /// extern crate serde; /// extern crate bincode; /// extern crate rayon; /// /// use lazy_transducer::LazyTransducer; /// use bincode::{serialize, deserialize, Error}; /// use rayon::prelude::*; /// /// #[derive(Debug, PartialEq, Serialize, Deserialize)] /// pub struct Foo { /// x: u64, /// y: f32, /// z: bool, /// } /// /// fn run() -> Result<(), Error> { /// let foo1 = Foo { x: 0xcafed00d, y: 0.75, z: false }; /// let foo2 = Foo { x: 0xdeadbeef, y: 0.50, z: true }; /// /// // we need to serialize the data, which we do by extending a byte vector with the individually /// // serialized components /// let mut data = serialize(&foo1)?; /// let sizeof_serialized_element = data.len(); /// data.extend_from_slice(&serialize(&foo2)?); /// /// // we construct our transducer by providing the serialized bytes _and_ the size of a serialized /// // element as input; our transducer just reads at the appropriate byte offset, and deserializes! /// let lt: LazyTransducer<_, Result<Foo, Error>> = /// LazyTransducer::new((data.as_slice(), sizeof_serialized_element), /// 2, /// |(input, size), idx| { /// deserialize(&input[(idx * size)..]) /// }); /// /// let foo2_ = lt.get(1).expect("has 2 elements")?; /// assert_eq!(foo2, foo2_); /// /// // and now with the help of rayon, we iterate over the items in parallel /// lt.into_par_iter().for_each(|elem| { /// println!("{:?}", elem); /// }); /// Ok(()) /// } /// # fn main() { run().unwrap() } /// ``` #[derive(Debug)] pub struct LazyTransducer<'a, Input, Output> where Input: 'a + Copy, Output: 'a, { pub(crate) count: usize, pub(crate) contents: Input, pub(crate) transducer: fn(Input, usize) -> Output, pub(crate) _marker: PhantomData<&'a Output>, } impl<'a, Input, Output> LazyTransducer<'a, Input, Output> where Input: 'a + Copy, Output: 'a, { /// How many elements are contained in this lazy transducer pub fn len(&self) -> usize { self.count } /// Create a new LazyTransducer with `count` elements in `contents`, using `transducer` to extract /// them. /// /// # Example /// /// ```rust /// use lazy_transducer::LazyTransducer; /// let data = [0xdeadbeefu32, 0xcafed00d]; /// let lt: LazyTransducer<&[u32], u64> = LazyTransducer::new(&data, 2, |input, idx| input[idx] as u64); /// ``` pub fn new(contents: Input, count: usize, transducer: fn(Input, usize) -> Output) -> Self { LazyTransducer { count, contents, transducer, _marker: PhantomData::default(), } } /// Get an element out of the lazy transducer, returning `None` if the index is greater than /// the number of elements in this lazy transducer. /// /// # Example /// /// ```rust /// extern crate lazy_transducer; /// use lazy_transducer::LazyTransducer; /// /// # fn main() { /// let data = [0xdeadbeefu64, 0xcafed00d]; /// let lt: LazyTransducer<&[u64], &u64> = LazyTransducer::new(&data, 2, |input, idx| &input[idx]); /// /// let cafedood = lt.get(1).expect("has 2 elements"); /// assert_eq!(*cafedood, 0xcafed00d); /// /// assert!(lt.get(2).is_none()); /// # } /// ``` #[inline] pub fn get(&self, idx: usize) -> Option<Output> { if idx >= self.count { None } else { Some((self.transducer)(self.contents, idx)) } } } /// A [scroll](https://docs.rs/scroll)-based transducer only requires a parsing context for construction. /// The correct method is statically dispatched according to the output type, and the bounds are checked /// according to the size of the input and the number of elements requested from the byte source. /// /// In order to use this, you must implement TryFromCtx and SizeWith, which you can usually derive /// with `#[derive(Pread, SizeWith)]` /// /// # Example /// /// ```rust /// extern crate lazy_transducer; /// #[macro_use] /// extern crate scroll; /// use lazy_transducer::ScrollTransducer; /// /// #[derive(Debug, Pread, SizeWith)] /// #[repr(C)] /// pub struct Rel { /// pub r_offset: u32, /// pub r_info: u32, /// } /// /// # fn main () { /// let bytes = vec![4, 0, 0, 0, 5, 0, 0, 0, 1, 0, 0, 0, 5, 0, 0, 0]; /// let lt: ScrollTransducer<Rel, scroll::Endian> = ScrollTransducer::parse_with(&bytes, 2, scroll::LE).unwrap(); /// for reloc in lt.into_iter() { /// assert_eq!(reloc.r_info, 5); /// println!("{:?}", reloc); /// } /// # } /// ``` #[cfg(feature = "use_scroll")] pub type ScrollTransducer<'a, Output, Ctx = scroll::Endian> = LazyTransducer<'a, (&'a [u8], Ctx), Output>; #[cfg(feature = "use_scroll")] impl<'a, Output, Ctx, E> ScrollTransducer<'a, Output, Ctx> where Ctx: Copy + Default, Output: 'a + ctx::TryFromCtx<'a, Ctx, Error = E> + SizeWith<Ctx>, E: From<scroll::Error> + std::fmt::Debug, { /// The transducer is just `pread`, whose impl is defined by the user, or via derive macro. /// We unwrap because we bounds checked on creation fn pread((input, ctx): (&'a [u8], Ctx), idx: usize) -> Output { let offset = Output::size_with(&ctx) * idx; input.pread_with(offset, ctx).unwrap() } /// Create a new scroll-based lazy transducer, /// using the given context to parse `count` elements out of `contents` /// /// # Example /// /// ```rust /// extern crate lazy_transducer; /// extern crate rayon; /// use lazy_transducer::{ScrollTransducer, Endian}; /// use rayon::prelude::*; /// /// # fn main() { /// let bytes = vec![1, 0, 0, 0, 2, 0, 0, 0, 3, 0, 0, 0, 0xef, 0xbe, 0xad, 0xde]; /// let lt: ScrollTransducer<u32> = ScrollTransducer::parse_with(&bytes, 4, Endian::Little).unwrap(); /// /// let deadbeef = lt.get(3).expect("has 4 elements"); /// assert_eq!(deadbeef, 0xdeadbeef); /// /// lt.into_par_iter().for_each(|n| { /// println!("{:?}", n); /// }); /// # } /// ``` pub fn parse_with(contents: &'a [u8], count: usize, ctx: Ctx) -> Result<Self, TransducerError> { let sizeof_element = Output::size_with(&ctx); let total_size = sizeof_element * count; if total_size > contents.len() { Err(TransducerError::ElementOverflow { nelements: count, sizeof_element, src_size: contents.len(), } .into()) } else { Ok(LazyTransducer { contents: (contents, ctx), count, transducer: Self::pread, _marker: PhantomData::default(), }) } } } impl<'a, Input: Copy, Output> Clone for LazyTransducer<'a, Input, Output> { fn clone(&self) -> Self { LazyTransducer { count: self.count, contents: self.contents, transducer: self.transducer.clone(), _marker: PhantomData::default(), } } } /// A generic iterator over the elements produced by the lazy transducer pub struct IntoIter<'a, Input: 'a + Copy, Output: 'a> { current: usize, lt: LazyTransducer<'a, Input, Output>, } impl<'a, Input: Copy, Output> Iterator for IntoIter<'a, Input, Output> { type Item = Output; fn next(&mut self) -> Option<Self::Item> { if self.current >= self.lt.count { None } else { let output = self.lt.get(self.current); self.current += 1; output } } } impl<'a, Input: Copy, Output> IntoIterator for LazyTransducer<'a, Input, Output> { type Item = Output; type IntoIter = IntoIter<'a, Input, Output>; fn into_iter(self) -> Self::IntoIter { IntoIter { current: 0, lt: self, } } } impl<'a, 'b, Input: Copy, Output> IntoIterator for &'b LazyTransducer<'a, Input, Output> { type Item = Output; type IntoIter = IntoIter<'a, Input, Output>; fn into_iter(self) -> Self::IntoIter { IntoIter { current: 0, lt: self.clone(), } } } impl<'a, Input: Copy, Output> ExactSizeIterator for IntoIter<'a, Input, Output> { fn len(&self) -> usize { self.lt.count } } /// A generic, parallel iterator over the elements produced by the lazy transducer. /// /// This implements rayon's ParallelIterator trait, so you need only use `rayon::prelude::*` and /// iterate in parallel via the `into_par_iter()` method. pub struct IntoParIter<'a, Input: 'a + Copy, Output: 'a> { current: usize, lt: LazyTransducer<'a, Input, Output>, } impl<'a, Input: Sync + Copy + Send, Output: Send + Sync> IntoParallelIterator for LazyTransducer<'a, Input, Output> { type Iter = IntoParIter<'a, Input, Output>; type Item = Output; fn into_par_iter(self) -> Self::Iter { IntoParIter { current: 0, lt: self, } } } impl<'a, Input: Sync + Send + Copy, Output: Send + Sync> ParallelIterator for IntoParIter<'a, Input, Output> { type Item = Output; fn drive_unindexed<C>(self, consumer: C) -> C::Result where C: UnindexedConsumer<Self::Item>, { bridge_unindexed( Producer { top: self.lt.count, lt: &self.lt, current: self.current, }, consumer, ) } } /// The parallel iterator producer for a lazy transducer, required by rayon. pub struct Producer<'b, 'a: 'b, Input: 'a + Sync + Copy + Send, Output: 'a + Send + Sync> { lt: &'b LazyTransducer<'a, Input, Output>, current: usize, top: usize, } impl<'b, 'a, Input: Sync + Copy + Send, Output: Send + Sync> Iterator for Producer<'b, 'a, Input, Output> { type Item = Output; fn next(&mut self) -> Option<Self::Item> { if self.current >= self.top || self.current >= self.lt.count { None } else { let output = self.lt.get(self.current); self.current += 1; output } } } impl<'b, 'a, Input: Send + Sync + Copy, Output: Sync + Send> UnindexedProducer for Producer<'b, 'a, Input, Output> { type Item = Output; fn split(mut self) -> (Self, Option<Self>) { let len = self.top - self.current; if len > 1 { let old_top = self.top; let split_len = len / 2; self.top = self.current + split_len; let right = Producer { lt: self.lt, current: self.top, top: old_top, }; (self, Some(right)) } else { (self, None) } } fn fold_with<F>(self, folder: F) -> F where F: Folder<Self::Item>, { folder.consume_iter(self.into_iter()) } }