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// src/io/local_cache.rs -- a local cache of files obtained from another IoProvider
// Copyright 2017 the Tectonic Project
// Licensed under the MIT License.
use mkstemp;
use std::collections::HashMap;
use std::ffi::{OsStr, OsString};
use std::fs::{self, File};
use std::io::{BufRead, BufReader, Read, Write};
use std::io::ErrorKind as IoErrorKind;
use std::path::{Path, PathBuf};
use std::str::FromStr;
use digest::{self, Digest, DigestData};
use errors::{ErrorKind, Result, ResultExt};
use io::{try_open_file, InputHandle, IoProvider, OpenResult};
use status::StatusBackend;
struct LocalCacheItem {
_length: u64,
digest: Option<DigestData>, // None => negative cache: this file is not in the bundle
}
pub struct LocalCache<B: IoProvider> {
backend: B,
digest_path: PathBuf,
cached_digest: DigestData,
checked_digest: bool,
manifest_path: PathBuf,
data_path: PathBuf,
contents: HashMap<OsString,LocalCacheItem>,
}
impl<B: IoProvider> LocalCache<B> {
pub fn new(mut backend: B, digest: &Path, manifest_base: &Path, data: &Path, status: &mut StatusBackend) -> Result<LocalCache<B>> {
// If the `digest` file exists, we assume that it is valid; this is
// *essential* so that we can use a URL as our default IoProvider
// without requiring a network connection to run. If it does not
// exist, we need to query the backend.
let mut checked_digest = false;
let digest_text = match File::open(digest) {
Ok(f) => {
let mut text = String::new();
f.take(64).read_to_string(&mut text)?;
text
},
Err(e) => {
if e.kind() != IoErrorKind::NotFound {
// Unexpected error reading the digest cache file. Ruh roh!
return Err(e.into());
}
// OK, digest file just doesn't exist. We need to query the backend for it.
match backend.input_open_name(OsStr::new(digest::DIGEST_NAME), status) {
OpenResult::Ok(h) => {
// Phew, the backend has the info we need.
let mut text = String::new();
h.take(64).read_to_string(&mut text)?;
checked_digest = true;
text
},
OpenResult::NotAvailable => {
// Broken or un-cacheable backend.
return Err(ErrorKind::Msg("backend does not provide needed SHA256SUM file".to_owned()).into());
},
OpenResult::Err(e) => {
return Err(e.into());
}
}
}
};
let cached_digest = DigestData::from_str(&digest_text).chain_err(|| "corrupted SHA256 digest cache")?;
if checked_digest {
// If checked_digest is true, the digest cache file did not exist
// and we got the text fresh from the backend. So, we should write
// it out to the cache file.
let mut f = File::create(&digest)?;
writeln!(f, "{}", digest_text)?;
}
// We can now figure out which manifest to use.
let mut manifest_path = manifest_base.to_owned();
manifest_path.push(&digest_text);
manifest_path.set_extension("txt");
// Read it in, if it exists.
let mut contents = HashMap::new();
match try_open_file(&manifest_path) {
OpenResult::NotAvailable => {},
OpenResult::Err(e) => { return Err(e.into()); },
OpenResult::Ok(mfile) => {
let f = BufReader::new(mfile);
for res in f.lines() {
let line = res?;
let bits = line.split_whitespace().collect::<Vec<_>>();
if bits.len() < 3 {
continue; // TODO: warn or something?
}
let name = OsString::from(bits[0]);
let length = match bits[1].parse::<u64>() {
Ok(l) => l,
Err(_) => continue
};
let digest = if bits[2] == "-" {
None
} else {
match DigestData::from_str(&bits[2]) {
Ok(d) => Some(d),
Err(e) => {
tt_warning!(status, "ignoring bad digest data \"{}\" for \"{}\" in \"{}\"",
&bits[2], bits[0], manifest_path.display() ; e);
continue;
}
}
};
contents.insert(name, LocalCacheItem { _length: length, digest: digest });
}
}
}
// All set.
Ok(LocalCache {
backend: backend,
digest_path: digest.to_owned(),
cached_digest: cached_digest,
checked_digest: checked_digest,
manifest_path: manifest_path,
data_path: data.to_owned(),
contents: contents
})
}
fn record_cache_result(&mut self, name: &OsStr, length: u64, digest: Option<DigestData>) -> Result<()> {
let digest_text = match digest {
Some(ref d) => d.to_string(),
None => "-".to_owned(),
};
let mut man = fs::OpenOptions::new()
.append(true)
.create(true)
.open(&self.manifest_path)?;
writeln!(man, "{} {} {}", name.to_string_lossy(), length, digest_text)?;
self.contents.insert(name.to_owned(), LocalCacheItem { _length: length, digest: digest });
Ok(())
}
fn path_for_name(&mut self, name: &OsStr, status: &mut StatusBackend) -> OpenResult<PathBuf> {
if let Some(info) = self.contents.get(name) {
return match info.digest {
None => OpenResult::NotAvailable,
Some(ref d) => match d.create_two_part_path(&self.data_path) {
Ok(p) => OpenResult::Ok(p),
Err(e) => OpenResult::Err(e.into()),
},
};
}
// Bummer, we haven't seen this file before. We need to (try to) fetch
// the item from the backend, saving it to disk and calculating its
// digest ourselves, then enter it in the cache and in our manifest.
// Fun times.
//
// First, if we're going to go to the backend, we should check that its
// digest is what we expect. If not, we do a lame thing where we error
// out but set things up so that things should succeed if the program
// is re-run. Exactly the lame TeX user experience that I've been trying
// to avoid!
if !self.checked_digest {
let dtext = match self.backend.input_open_name(OsStr::new("SHA256SUM"), status) {
OpenResult::Ok(h) => {
let mut text = String::new();
if let Err(e) = h.take(64).read_to_string(&mut text) {
return OpenResult::Err(e.into());
}
text
},
OpenResult::NotAvailable => {
// Broken or un-cacheable backend.
return OpenResult::Err(ErrorKind::Msg("backend does not provide needed SHA256SUM file".to_owned()).into());
},
OpenResult::Err(e) => {
return OpenResult::Err(e.into());
}
};
let current_digest = match DigestData::from_str(&dtext).chain_err(|| "bad SHA256 digest from backend") {
Ok(d) => d,
Err(e) => { return OpenResult::Err(e); },
};
if self.cached_digest != current_digest {
// Crap! The backend isn't what we thought it was. Rewrite the
// digest file so that next time we'll start afresh.
match File::create(&self.digest_path) {
Ok(mut f) => {
if let Err(e) = writeln!(f, "{}", current_digest.to_string()) {
return OpenResult::Err(e.into());
}
},
Err(e) => {
// XXX this will be super confusing since we don't
// indicate that the error is related to the digest
// file, not the underlying file.
return OpenResult::Err(e.into());
}
};
return OpenResult::Err(ErrorKind::Msg("backend digest changed; rerun to use updated information".to_owned()).into());
}
// Phew, the backend hasn't changed. Don't check again.
self.checked_digest = true;
}
// The bundle's overall digest is OK. Now try open the file. If it's
// not available, cache that result, since LaTeX compilations commonly
// touch nonexistent files. If we didn't maintain the negative cache,
// we'd have to touch the network for virtually every compilation.
let mut stream = match self.backend.input_open_name (name, status) {
OpenResult::Ok(s) => s,
OpenResult::Err(e) => return OpenResult::Err(e),
OpenResult::NotAvailable => {
if let Err(e) = self.record_cache_result(name, 0, None) {
return OpenResult::Err(e.into());
}
return OpenResult::NotAvailable;
}
};
// OK, we can stream the file to a temporary location on disk,
// computing its SHA256 as we go.
let mut digest_builder = digest::create();
let mut length = 0;
let temp_path = {
let mut templ = self.data_path.clone();
templ.push("download_XXXXXX");
let mut temp_dest = match mkstemp::TempFile::new(&templ.to_string_lossy(), false) {
Ok(f) => f,
Err(e) => return OpenResult::Err(e.into()),
};
let mut buf = [0u8; 8192];
while let Ok(nbytes) = stream.read(&mut buf) {
if nbytes == 0 {
break;
}
length += nbytes;
let chunk = &buf[..nbytes];
digest_builder.input(chunk);
if let Err(e) = temp_dest.write_all(chunk) {
return OpenResult::Err(e.into());
}
}
// XXX MAKE READONLY -- the ideal approach depends on unstable APIs
temp_dest.path().to_owned()
};
let digest = DigestData::from(digest_builder);
// Now we can move it to its final destination ..
let final_path = match digest.create_two_part_path(&self.data_path) {
Ok(p) => p,
Err(e) => return OpenResult::Err(e.into()),
};
if let Err(e) = fs::rename(&temp_path, &final_path) {
return OpenResult::Err(e.into());
}
// And finally add a record of this file to our manifest. Note that
// we're opening and closing this file every time we load a new file;
// not so efficient, but whatever.
if let Err(e) = self.record_cache_result(name, length as u64, Some(digest)) {
return OpenResult::Err(e.into());
}
OpenResult::Ok(final_path)
}
}
impl<B: IoProvider> IoProvider for LocalCache<B> {
fn input_open_name(&mut self, name: &OsStr, status: &mut StatusBackend) -> OpenResult<InputHandle> {
let path = match self.path_for_name(name, status) {
OpenResult::Ok(p) => p,
OpenResult::NotAvailable => return OpenResult::NotAvailable,
OpenResult::Err(e) => return OpenResult::Err(e),
};
let f = match File::open (&path) {
Ok(f) => f,
Err(e) => return OpenResult::Err(e.into())
};
OpenResult::Ok(InputHandle::new(name, BufReader::new(f)))
}
}