Refactor in preparation to larger changes

1 files changed, 0 insertions, 354 deletions

diff --git a/log_db/src/reverse_log_reader.rs b/log_db/src/reverse_log_reader.rs
deleted file mode 100644
index f042406..0000000
--- a/log_db/src/reverse_log_reader.rs
+++ /dev/null
@@ -1,354 +0,0 @@
-use super::common::*;
-use std::fs::{self};
-use std::io::{self, Read, Seek, SeekFrom};
-
-pub struct ReverseLogReader<'a> {
-    /// The file to read from end to beginning.
-    file: &'a mut fs::File,
-    /// The internal buffer used to read from the file.
-    /// It is populated with the last INTERNAL_BUF_SIZE bytes read from the file
-    /// and is used to read records in reverse order
-    internal_buf: Vec<u8>,
-    /// The current position in the internal buffer. It is decremented as bytes are read
-    /// from the buffer. When a read is requested and the internal position is 0, the buffer
-    /// is populated with the next (= closer to the start of the file) INTERNAL_BUF_SIZE bytes from the file.
-    /// Note: This is the index of the next byte to be read from the internal buffer + 1
-    internal_pos: usize,
-    /// A flag indicating whether the record separator at the cursor position has been consumed.
-    /// Useful to avoid consuming the separator once when reading until an escape character, and
-    /// a second time when reading a new record and validating it ends in a separator.
-    consumed_record_sep: bool,
-}
-
-// This value is based on the reverse_read_file_with_various_buffer_sizes benchmark.
-// Greater values yield little to no performance improvement.
-const DEFAULT_INTERNAL_BUF_SIZE: usize = 32768;
-impl<'a> ReverseLogReader<'a> {
-    pub fn new(file: &mut fs::File) -> Result<ReverseLogReader, io::Error> {
-        file.seek(SeekFrom::End(0))?;
-        Ok(ReverseLogReader {
-            file,
-            internal_buf: vec![0; DEFAULT_INTERNAL_BUF_SIZE],
-            internal_pos: 0,
-            consumed_record_sep: false,
-        })
-    }
-
-    pub fn new_with_size(
-        file: &mut fs::File,
-        internal_buf_size: usize,
-    ) -> Result<ReverseLogReader, io::Error> {
-        file.seek(SeekFrom::End(0))?;
-        Ok(ReverseLogReader {
-            file,
-            internal_buf: vec![0; internal_buf_size],
-            internal_pos: 0,
-            consumed_record_sep: false,
-        })
-    }
-
-    pub fn read_record(&mut self) -> Result<Option<Record>, io::Error> {
-        if self.file.stream_position()? == 0 && self.internal_pos == 0 {
-            return Ok(None);
-        }
-
-        if !self.consumed_record_sep {
-            // Check that record ends with a record separator
-            match self.read_special_sequence()? {
-                SpecialSequence::RecordSeparator => {}
-                _ => {
-                    return Err(io::Error::new(
-                        io::ErrorKind::InvalidData,
-                        "Record does not end in record separator",
-                    ));
-                }
-            }
-        }
-        self.consumed_record_sep = false;
-
-        let mut result_buf: Vec<u8> = vec![];
-        let mut read_buf = Vec::with_capacity(self.internal_buf.len());
-        loop {
-            read_buf.clear();
-            let read = self.read_until(ESCAPE_CHARACTER, &mut read_buf)?;
-
-            result_buf.extend(&read_buf[..read]);
-
-            if self.file.stream_position()? == 0 && self.internal_pos == 0 {
-                // We read until the start of the file, we are done
-                break;
-            }
-
-            match self.read_special_sequence()? {
-                SpecialSequence::LiteralEscape => {
-                    result_buf.push(ESCAPE_CHARACTER);
-                }
-                SpecialSequence::LiteralFieldSeparator => {
-                    result_buf.push(FIELD_SEPARATOR);
-                }
-                SpecialSequence::RecordSeparator => {
-                    self.consumed_record_sep = true;
-                    break;
-                }
-            }
-        }
-
-        result_buf.reverse();
-        Ok(Some(Record::deserialize(&result_buf)))
-    }
-
-    /// Read exactly `buf.len()` bytes from the file, return an error if the file is exhausted.
-    /// The bytes are returned in start -> end order.
-    /// If an error is returned, the contents of `buf` are in an undefined state.
-    fn read_exact(&mut self, buf: &mut [u8]) -> Result<usize, io::Error> {
-        let mut read = 0;
-        while read < buf.len() {
-            if self.internal_pos == 0 {
-                let populated_n = self.populate_internal_buf()?;
-                if populated_n == 0 {
-                    return Err(io::Error::new(
-                        io::ErrorKind::UnexpectedEof,
-                        "Unexpected end of file",
-                    ));
-                }
-            }
-
-            let end = buf.len() - read;
-            let n = std::cmp::min(self.internal_pos, end);
-            buf[end - n..end]
-                .copy_from_slice(&self.internal_buf[self.internal_pos - n..self.internal_pos]);
-            read += n;
-            self.internal_pos -= n;
-        }
-
-        Ok(read)
-    }
-
-    fn populate_internal_buf(&mut self) -> Result<usize, io::Error> {
-        let current_seek_pos = self.file.stream_position()? as usize;
-
-        // Seek back by the size of the internal buffer or to the beginning of the file
-        let seek_length = if current_seek_pos > self.internal_buf.len() {
-            self.internal_pos = self.internal_buf.len();
-            self.internal_buf.len()
-        } else {
-            self.internal_buf = vec![0; current_seek_pos as usize];
-            self.internal_pos = current_seek_pos as usize;
-            current_seek_pos
-        };
-
-        self.file.seek_relative(-(seek_length as i64))?;
-        self.file.read_exact(&mut self.internal_buf)?;
-        self.file.seek_relative(-(seek_length as i64))?;
-
-        Ok(seek_length as usize)
-    }
-
-    /// Iterate over the internal buffer with internal_pos as the index.
-    /// If the byte is found or the file has been exhausted, we return the number of bytes read.
-    /// The `buf` parameter is used to store the bytes read from the internal buffer, excluding the found byte,
-    /// in reverse order.
-    fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize, io::Error> {
-        // TODO: optimize this
-        let mut read = 0;
-        loop {
-            // If we reach internal_pos == 0, we need to populate the internal buffer.
-            if self.internal_pos == 0 {
-                let populated_n = self.populate_internal_buf()?;
-                if populated_n == 0 {
-                    return Ok(read);
-                }
-            }
-
-            while self.internal_pos > 0 {
-                let index = self.internal_pos - 1;
-                if self.internal_buf[index] == byte {
-                    return Ok(read);
-                }
-                buf.push(self.internal_buf[index]);
-                read += 1;
-                self.internal_pos -= 1;
-            }
-        }
-    }
-
-    fn read_special_sequence(&mut self) -> Result<SpecialSequence, io::Error> {
-        let mut special_buf: Vec<u8> = vec![0; SEQ_RECORD_SEP.len()];
-        self.read_exact(&mut special_buf)?;
-
-        match validate_special(&special_buf.as_slice()) {
-            Some(special) => Ok(special),
-            None => {
-                let pos = self.file.stream_position().unwrap() + self.internal_pos as u64;
-
-                Err(io::Error::new(
-                    io::ErrorKind::InvalidData,
-                    format!(
-                        "Not a special sequence: {:?} at pos: {:x}",
-                        special_buf, pos,
-                    ),
-                ))
-            }
-        }
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use std::io::Write;
-    use std::path::Path;
-
-    #[test]
-    fn test_read_until_found() {
-        let mut file = tempfile::tempfile().unwrap();
-        file.write_all(b"hello,world").unwrap();
-        let mut reader = ReverseLogReader::new(&mut file).unwrap();
-        let mut buf = vec![];
-        assert_eq!(reader.read_until(b',', &mut buf).unwrap(), 5);
-        assert_eq!(buf, b"dlrow");
-    }
-
-    #[test]
-    fn test_read_until_not_found() {
-        let mut file = tempfile::tempfile().unwrap();
-        file.write_all(b"hello,world").unwrap();
-        let mut reader = ReverseLogReader::new(&mut file).unwrap();
-        let mut buf = vec![];
-        let read = reader.read_until(b'!', &mut buf).unwrap();
-        assert_eq!(buf, b"dlrow,olleh");
-        assert_eq!(read, 11);
-    }
-
-    #[test]
-    fn test_read_special_sequence() {
-        let mut file = tempfile::tempfile().unwrap();
-        let mut buf = vec![];
-        buf.extend(SEQ_RECORD_SEP);
-        buf.extend(SEQ_LIT_ESCAPE);
-        buf.extend(SEQ_LIT_FIELD_SEP);
-        // Note: written in start -> end order, read end -> start
-        file.write_all(&buf).unwrap();
-
-        let mut reader = ReverseLogReader::new(&mut file).unwrap();
-        assert_eq!(
-            reader.read_special_sequence().unwrap(),
-            SpecialSequence::LiteralFieldSeparator
-        );
-        assert_eq!(
-            reader.read_special_sequence().unwrap(),
-            SpecialSequence::LiteralEscape
-        );
-        assert_eq!(
-            reader.read_special_sequence().unwrap(),
-            SpecialSequence::RecordSeparator
-        );
-    }
-
-    #[test]
-    fn test_populate_internal_buf() {
-        let mut file = tempfile::tempfile().unwrap();
-        file.write_all(b"hello,world").unwrap();
-        let mut reader = ReverseLogReader::new_with_size(&mut file, 3).unwrap();
-
-        reader.populate_internal_buf().unwrap();
-        assert_eq!(
-            String::from_utf8(reader.internal_buf.clone()).unwrap(),
-            "rld".to_string()
-        );
-
-        reader.populate_internal_buf().unwrap();
-        assert_eq!(
-            String::from_utf8(reader.internal_buf.clone()).unwrap(),
-            ",wo".to_string()
-        );
-
-        reader.populate_internal_buf().unwrap();
-        assert_eq!(
-            String::from_utf8(reader.internal_buf.clone()).unwrap(),
-            "llo".to_string()
-        );
-
-        reader.populate_internal_buf().unwrap();
-        assert_eq!(
-            String::from_utf8(reader.internal_buf.clone()).unwrap(),
-            "he".to_string()
-        );
-    }
-
-    #[test]
-    fn test_reverse_log_reader_fixture_db1() {
-        let db_path = Path::new(TEST_RESOURCES_DIR).join("test_db1");
-        let mut file = fs::OpenOptions::new()
-            .read(true)
-            .open(&db_path)
-            .expect("Failed to open file");
-        let mut reverse_log_reader = ReverseLogReader::new(&mut file).unwrap();
-
-        // There are two records in the log with "schema": Int, Null
-
-        let last_record = reverse_log_reader
-            .next()
-            .expect("Failed to read the last record");
-        assert!(match last_record.values.as_slice() {
-            [RecordValue::Int(10), RecordValue::Null] => true,
-            _ => false,
-        });
-
-        let first_record = reverse_log_reader
-            .next()
-            .expect("Failed to read the first record");
-        assert!(match first_record.values.as_slice() {
-            // Note: the int value is equal to the escape byte
-            [RecordValue::Int(0x1D), RecordValue::Null] => true,
-            _ => false,
-        });
-
-        assert!(reverse_log_reader.next().is_none());
-    }
-
-    #[test]
-    fn test_read_exact() {
-        let mut file = tempfile::tempfile().unwrap();
-        file.write_all(b"hello,world").unwrap();
-        let mut reader = ReverseLogReader::new(&mut file).unwrap();
-        let mut buf = vec![0; 3];
-
-        let read = reader.read_exact(&mut buf).unwrap();
-        assert_eq!(buf, b"rld");
-        assert_eq!(read, 3);
-
-        let read = reader.read_exact(&mut buf).unwrap();
-        assert_eq!(buf, b",wo");
-        assert_eq!(read, 3);
-
-        let read = reader.read_exact(&mut buf).unwrap();
-        assert_eq!(buf, b"llo");
-        assert_eq!(read, 3);
-
-        assert!(reader.read_exact(&mut buf).unwrap_err().kind() == io::ErrorKind::UnexpectedEof);
-    }
-
-    #[test]
-    fn test_read_exact_insufficient_bytes() {
-        let mut file = tempfile::tempfile().unwrap();
-        file.write_all(b"hello").unwrap();
-        let mut reader = ReverseLogReader::new(&mut file).unwrap();
-        let mut buf = vec![0; 10];
-        assert!(reader.read_exact(&mut buf).unwrap_err().kind() == io::ErrorKind::UnexpectedEof);
-    }
-}
-
-impl Iterator for ReverseLogReader<'_> {
-    type Item = Record;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        match self.read_record() {
-            Ok(Some(record)) => Some(record),
-            Ok(None) => None,
-            Err(err) => {
-                panic!("Error reading record: {:?}", err,)
-            }
-        }
-    }
-}