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/// `fingertips` creates an inverted index for a set of text files.
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///
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/// Most of the actual work is done by the modules `index`, `read`, `write`,
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/// and `merge`. In this file, `main.rs`, we put the pieces together in two
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/// different ways.
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///
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/// * `run_single_threaded` simply does everything in one thread, in
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/// the most straightforward possible way.
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///
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/// * Then, we break the work into a five-stage pipeline so that we can run
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/// it on multiple CPUs. `run_pipeline` puts the five stages together.
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///
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/// The `main` function at the end handles command-line arguments. It calls one
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/// of the two functions above to do the work.
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mod index;
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mod read;
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mod write;
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mod merge;
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mod tmp;
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use std::fs::File;
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use std::io;
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use std::io::prelude::*;
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use std::path::{Path, PathBuf};
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use std::sync::mpsc::{channel, Receiver};
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use std::thread::{spawn, JoinHandle};
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use argparse::{ArgumentParser, StoreTrue, Collect};
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use crate::index::InMemoryIndex;
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use crate::write::write_index_to_tmp_file;
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use crate::merge::FileMerge;
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use crate::tmp::TmpDir;
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/// Create an inverted index for the given list of `documents`,
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/// storing it in the specified `output_dir`.
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fn run_single_threaded(documents: Vec<PathBuf>, output_dir: PathBuf)
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-> io::Result<()>
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{
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// If all the documents fit comfortably in memory, we'll create the whole
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// index in memory.
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let mut accumulated_index = InMemoryIndex::new();
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// If not, then as memory fills up, we'll write largeish temporary index
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// files to disk, saving the temporary filenames in `merge` so that later we
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// can merge them all into a single huge file.
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let mut merge = FileMerge::new(&output_dir);
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// A tool for generating temporary filenames.
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let mut tmp_dir = TmpDir::new(&output_dir);
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// For each document in the set...
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for (doc_id, filename) in documents.into_iter().enumerate() {
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// ...load it into memory...
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let mut f = File::open(filename)?;
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let mut text = String::new();
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f.read_to_string(&mut text)?;
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// ...and add its contents to the in-memory `accumulated_index`.
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let index = InMemoryIndex::from_single_document(doc_id, text);
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accumulated_index.merge(index);
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if accumulated_index.is_large() {
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// To avoid running out of memory, dump `accumulated_index` to disk.
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let file = write_index_to_tmp_file(accumulated_index, &mut tmp_dir)?;
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merge.add_file(file)?;
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accumulated_index = InMemoryIndex::new();
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}
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}
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// Done reading documents! Save the last data set to disk, then merge the
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// temporary index files if there are more than one.
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if !accumulated_index.is_empty() {
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let file = write_index_to_tmp_file(accumulated_index, &mut tmp_dir)?;
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merge.add_file(file)?;
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}
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merge.finish()
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}
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/// Start a thread that loads documents from the filesystem into memory.
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///
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/// `documents` is a list of filenames to load.
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///
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/// This returns a pair of values: a receiver that receives the documents, as
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/// Strings; and a `JoinHandle` that can be used to wait for this thread to
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/// exit and to get the `io::Error` value if anything goes wrong.
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fn start_file_reader_thread(documents: Vec<PathBuf>)
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-> (Receiver<String>, JoinHandle<io::Result<()>>)
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{
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let (sender, receiver) = channel();
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let handle = spawn(move || {
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for filename in documents {
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let mut f = File::open(filename)?;
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let mut text = String::new();
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f.read_to_string(&mut text)?;
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if sender.send(text).is_err() {
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break;
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}
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}
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Ok(())
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});
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(receiver, handle)
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}
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/// Start a thread that tokenizes each text and converts it into an in-memory
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/// index. (We assume that every document fits comfortably in memory.)
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///
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/// `texts` is the stream of documents from the file reader thread.
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///
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/// This assigns each document a number. It returns a pair of values: a
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/// receiver, the sequence of in-memory indexes; and a `JoinHandle` that can be
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/// used to wait for this thread to exit. This stage of the pipeline is
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/// infallible (it performs no I/O, so there are no possible errors).
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fn start_file_indexing_thread(texts: Receiver<String>)
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-> (Receiver<InMemoryIndex>, JoinHandle<()>)
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{
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let (sender, receiver) = channel();
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let handle = spawn(move || {
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for (doc_id, text) in texts.into_iter().enumerate() {
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let index = InMemoryIndex::from_single_document(doc_id, text);
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if sender.send(index).is_err() {
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break;
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}
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}
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});
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(receiver, handle)
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}
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/// Start a thread that merges in-memory indexes.
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///
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/// `file_indexes` receives a stream of indexes from the file indexing thread.
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/// These indexes typically vary a lot in size, since the input documents will
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/// typically be all different sizes.
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///
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/// The thread created by this function merges those indexes into "large"
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/// indexes and passes these large indexes on to a new channel.
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///
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/// This returns a pair: a receiver, the sequence of large indexes produced by
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/// merging the input indexes; and a `JoinHandle` that can be used to wait for
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/// this thread to exit. This stage of the pipeline is infallible (it performs
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/// no I/O).
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fn start_in_memory_merge_thread(file_indexes: Receiver<InMemoryIndex>)
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-> (Receiver<InMemoryIndex>, JoinHandle<()>)
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{
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let (sender, receiver) = channel();
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let handle = spawn(move || {
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let mut accumulated_index = InMemoryIndex::new();
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for fi in file_indexes {
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accumulated_index.merge(fi);
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if accumulated_index.is_large() {
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if sender.send(accumulated_index).is_err() {
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return;
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}
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accumulated_index = InMemoryIndex::new();
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}
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}
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if !accumulated_index.is_empty() {
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let _ = sender.send(accumulated_index);
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}
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});
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(receiver, handle)
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}
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/// Start a thread that saves large indexes to temporary files.
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///
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/// This thread generates a meaningless unique filename for each index in
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/// `big_indexes`, saves the data, and passes the filename on to a new channel.
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///
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/// This returns a pair: a receiver that receives the filenames; and a
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/// `JoinHandle` that can be used to wait for this thread to exit and receive
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/// any I/O errors it encountered.
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fn start_index_writer_thread(big_indexes: Receiver<InMemoryIndex>,
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output_dir: &Path)
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-> (Receiver<PathBuf>, JoinHandle<io::Result<()>>)
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{
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let (sender, receiver) = channel();
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let mut tmp_dir = TmpDir::new(output_dir);
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let handle = spawn(move || {
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for index in big_indexes {
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let file = write_index_to_tmp_file(index, &mut tmp_dir)?;
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if sender.send(file).is_err() {
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break;
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}
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}
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Ok(())
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});
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(receiver, handle)
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}
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/// Given a sequence of filenames of index data files, merge all the files
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/// into a single index data file.
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fn merge_index_files(files: Receiver<PathBuf>, output_dir: &Path)
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-> io::Result<()>
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{
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let mut merge = FileMerge::new(output_dir);
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for file in files {
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merge.add_file(file)?;
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}
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merge.finish()
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}
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/// Create an inverted index for the given list of `documents`,
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/// storing it in the specified `output_dir`.
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///
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/// On success this does exactly the same thing as `run_single_threaded`, but
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/// faster since it uses multiple CPUs and keeps them busy while I/O is
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/// happening.
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fn run_pipeline(documents: Vec<PathBuf>, output_dir: PathBuf)
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-> io::Result<()>
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{
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// Launch all five stages of the pipeline.
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let (texts, h1) = start_file_reader_thread(documents);
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let (pints, h2) = start_file_indexing_thread(texts);
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let (gallons, h3) = start_in_memory_merge_thread(pints);
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let (files, h4) = start_index_writer_thread(gallons, &output_dir);
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let result = merge_index_files(files, &output_dir);
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// Wait for threads to finish, holding on to any errors that they encounter.
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let r1 = h1.join().unwrap();
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h2.join().unwrap();
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h3.join().unwrap();
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let r4 = h4.join().unwrap();
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// Return the first error encountered, if any.
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// (As it happens, h2 and h3 can't fail: those threads
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// are pure in-memory data processing.)
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r1?;
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r4?;
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result
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}
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/// Given some paths, generate the complete list of text files to index. We check
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/// on disk whether the path is the name of a file or a directory; for
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/// directories, all .txt files immediately under the directory are indexed.
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/// Relative paths are fine.
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///
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/// It's an error if any of the `args` is not a valid path to an existing file
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/// or directory.
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fn expand_filename_arguments(args: Vec<String>) -> io::Result<Vec<PathBuf>> {
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let mut filenames = vec![];
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for arg in args {
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let path = PathBuf::from(arg);
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if path.metadata()?.is_dir() {
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for entry in path.read_dir()? {
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let entry = entry?;
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if entry.file_type()?.is_file() {
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filenames.push(entry.path());
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}
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}
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} else {
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filenames.push(path);
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}
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}
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Ok(filenames)
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}
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/// Generate an index for a bunch of text files.
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fn run(filenames: Vec<String>, single_threaded: bool) -> io::Result<()> {
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let output_dir = PathBuf::from(".");
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let documents = expand_filename_arguments(filenames)?;
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if single_threaded {
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run_single_threaded(documents, output_dir)
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} else {
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run_pipeline(documents, output_dir)
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}
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}
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fn main() {
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let mut single_threaded = false;
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let mut filenames = vec![];
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{
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let mut ap = ArgumentParser::new();
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ap.set_description("Make an inverted index for searching documents.");
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ap.refer(&mut single_threaded)
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.add_option(&["-1", "--single-threaded"], StoreTrue,
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"Do all the work on a single thread.");
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ap.refer(&mut filenames)
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.add_argument("filenames", Collect,
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"Names of files/directories to index. \
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For directories, all .txt files immediately \
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under the directory are indexed.");
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ap.parse_args_or_exit();
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}
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match run(filenames, single_threaded) {
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Ok(()) => {}
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Err(err) => println!("error: {}", err)
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}
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}
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