path: root/openpgp/src/parse/partial_body.rs

use std::cmp;
use std::io;
use std::io::{Error, ErrorKind};

use buffered_reader::{buffered_reader_generic_read_impl, BufferedReader};

use crate::{vec_resize, vec_truncate};
use crate::packet::header::BodyLength;
use crate::parse::{Cookie, Hashing};

const TRACE : bool = false;


/// A `BufferedReader` that transparently handles OpenPGP's chunking
/// scheme.  This implicitly implements a limitor.
pub(crate) struct BufferedReaderPartialBodyFilter<T: BufferedReader<Cookie>> {
    // The underlying reader.
    reader: T,

    // The amount of unread data in the current partial body chunk.
    // That is, if `buffer` contains 10 bytes and
    // `partial_body_length` is 20, then there are 30 bytes of
    // unprocessed (unconsumed) data in the current chunk.
    partial_body_length: u32,
    // Whether this is the last partial body chuck.
    last: bool,

    // Sometimes we have to double buffer.  This happens if the caller
    // requests X bytes and that chunk straddles a partial body length
    // boundary.
    buffer: Option<Vec<u8>>,
    // The position within the buffer.
    cursor: usize,
    /// Currently unused buffers.
    unused_buffers: Vec<Vec<u8>>,

    // The user-defined cookie.
    cookie: Cookie,

    // Whether to include the headers in any hash directly over the
    // current packet.  If not, calls Cookie::hashing at
    // the current level to disable hashing while reading headers.
    hash_headers: bool,
}

impl<T: BufferedReader<Cookie>> std::fmt::Display
        for BufferedReaderPartialBodyFilter<T> {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        write!(f, "BufferedReaderPartialBodyFilter")
    }
}

impl<T: BufferedReader<Cookie>> std::fmt::Debug
        for BufferedReaderPartialBodyFilter<T> {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        f.debug_struct("BufferedReaderPartialBodyFilter")
            .field("partial_body_length", &self.partial_body_length)
            .field("last", &self.last)
            .field("hash headers", &self.hash_headers)
            .field("buffer (bytes left)",
                   &self.buffer.as_ref().map(|buffer| buffer.len()))
            .field("reader", &self.reader)
            .finish()
    }
}

impl<T: BufferedReader<Cookie>> BufferedReaderPartialBodyFilter<T> {
    /// Create a new BufferedReaderPartialBodyFilter object.
    /// `partial_body_length` is the amount of data in the initial
    /// partial body chunk.
    pub fn with_cookie(reader: T, partial_body_length: u32,
                       hash_headers: bool, cookie: Cookie) -> Self {
        BufferedReaderPartialBodyFilter {
            reader,
            partial_body_length,
            last: false,
            buffer: None,
            cursor: 0,
            unused_buffers: Vec::with_capacity(2),
            cookie,
            hash_headers,
        }
    }

    // Make sure that the local buffer contains `amount` bytes.
    fn do_fill_buffer (&mut self, amount: usize) -> Result<(), std::io::Error> {
        tracer!(TRACE, "PBF::do_fill_buffer", self.cookie.level.unwrap_or(0));
        t!("BufferedReaderPartialBodyFilter::do_fill_buffer(\
            amount: {}) (partial body length: {}, last: {})",
           amount, self.partial_body_length, self.last);

        if self.last && self.partial_body_length == 0 {
            // We reached the end.  Avoid fruitlessly copying data
            // over and over again trying to buffer more data.
            return Ok(());
        }

        // We want to avoid double buffering as much as possible.
        // Thus, we only buffer as much as needed.
        let mut buffer = self.unused_buffers.pop()
            .map(|mut v| {
                vec_resize(&mut v, amount);
                v
            })
            .unwrap_or_else(|| vec![0u8; amount]);
        let mut amount_buffered = 0;

        if let Some(ref old_buffer) = self.buffer {
            // The amount of data that is left in the old buffer.
            let amount_left = old_buffer.len() - self.cursor;

            // This function should only be called if we actually need
            // to read something.
            assert!(amount > amount_left);

            amount_buffered = amount_left;

            // Copy the data that is still in buffer.
            buffer[..amount_buffered]
                .copy_from_slice(&old_buffer[self.cursor..]);

            t!("Copied {} bytes from the old buffer", amount_buffered);
        }

        let mut err = None;

        loop {
            let to_read = cmp::min(
                // Data in current chunk.
                self.partial_body_length as usize,
                // Space left in the buffer.
                buffer.len() - amount_buffered);
            t!("Trying to buffer {} bytes \
                (partial body length: {}; space: {})",
               to_read, self.partial_body_length,
               buffer.len() - amount_buffered);
            if to_read > 0 {
                let result = self.reader.read(
                    &mut buffer[amount_buffered..amount_buffered + to_read]);
                match result {
                    Ok(did_read) => {
                        t!("Buffered {} bytes", did_read);
                        amount_buffered += did_read;
                        self.partial_body_length -= did_read as u32;

                        if did_read < to_read {
                            // Short read => EOF.  We're done.
                            // (Although the underlying message is
                            // probably corrupt.)
                            break;
                        }
                    },
                    Err(e) => {
                        t!("Err reading: {:?}", e);
                        err = Some(e);
                        break;
                    },
                }
            }

            if amount_buffered == amount || self.last {
                // We're read enough or we've read everything.
                break;
            }

            // Read the next partial body length header.
            assert_eq!(self.partial_body_length, 0);

            // Disable hashing, if necessary.
            if ! self.hash_headers {
                if let Some(level) = self.reader.cookie_ref().level {
                    Cookie::hashing(
                        &mut self.reader, Hashing::Disabled, level);
                }
            }

            t!("Reading next chunk's header (hashing: {}, level: {:?})",
               self.hash_headers, self.reader.cookie_ref().level);