Mercurial > lbo > hg > leveldb-rs
view src/table_reader.rs @ 120:28bf33d01950
Build shared block cache into Options
author | Lewin Bormann <lbo@spheniscida.de> |
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date | Mon, 26 Dec 2016 11:09:07 +0000 |
parents | c2539cd2d021 |
children | 04b1d08a5876 |
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use block::{Block, BlockIter}; use blockhandle::BlockHandle; use filter::{InternalFilterPolicy, FilterPolicy}; use filter_block::FilterBlockReader; use options::{self, CompressionType, Options}; use table_builder::{self, Footer}; use types::{cmp, CmpFn, LdbIterator}; use key_types::{internal_key_cmp, InternalKey}; use std::io::{self, Read, Seek, SeekFrom, Result}; use std::cmp::Ordering; use integer_encoding::FixedInt; use crc::crc32::{self, Hasher32}; /// Reads the table footer. fn read_footer<R: Read + Seek>(f: &mut R, size: usize) -> Result<Footer> { try!(f.seek(SeekFrom::Start((size - table_builder::FULL_FOOTER_LENGTH) as u64))); let mut buf = [0; table_builder::FULL_FOOTER_LENGTH]; try!(f.read_exact(&mut buf)); Ok(Footer::decode(&buf)) } fn read_bytes<R: Read + Seek>(f: &mut R, location: &BlockHandle) -> Result<Vec<u8>> { try!(f.seek(SeekFrom::Start(location.offset() as u64))); let mut buf = Vec::new(); buf.resize(location.size(), 0); try!(f.read_exact(&mut buf[0..location.size()])); Ok(buf) } struct TableBlock { block: Block, checksum: u32, compression: CompressionType, } impl TableBlock { /// Reads a block at location. fn read_block<R: Read + Seek>(f: &mut R, location: &BlockHandle) -> Result<TableBlock> { // The block is denoted by offset and length in BlockHandle. A block in an encoded // table is followed by 1B compression type and 4B checksum. let buf = try!(read_bytes(f, location)); let compress = try!(read_bytes(f, &BlockHandle::new(location.offset() + location.size(), table_builder::TABLE_BLOCK_COMPRESS_LEN))); let cksum = try!(read_bytes(f, &BlockHandle::new(location.offset() + location.size() + table_builder::TABLE_BLOCK_COMPRESS_LEN, table_builder::TABLE_BLOCK_CKSUM_LEN))); Ok(TableBlock { block: Block::new(buf), checksum: u32::decode_fixed(&cksum), compression: options::int_to_compressiontype(compress[0] as u32) .unwrap_or(CompressionType::CompressionNone), }) } /// Verify checksum of block fn verify(&self) -> bool { let mut digest = crc32::Digest::new(crc32::CASTAGNOLI); digest.write(&self.block.contents()); digest.write(&[self.compression as u8; 1]); digest.sum32() == self.checksum } } pub struct Table<R: Read + Seek, FP: FilterPolicy> { file: R, file_size: usize, opt: Options, cmp: Box<CmpFn>, footer: Footer, indexblock: Block, filters: Option<FilterBlockReader<FP>>, } impl<R: Read + Seek, FP: FilterPolicy> Table<R, FP> { /// Creates a new table reader operating on unformatted keys (i.e., UserKey). fn new_raw(mut file: R, size: usize, fp: FP, opt: Options) -> Result<Table<R, FP>> { let footer = try!(read_footer(&mut file, size)); let indexblock = try!(TableBlock::read_block(&mut file, &footer.index)); let metaindexblock = try!(TableBlock::read_block(&mut file, &footer.meta_index)); if !indexblock.verify() || !metaindexblock.verify() { return Err(io::Error::new(io::ErrorKind::InvalidData, "Indexblock/Metaindexblock failed verification")); } // Open filter block for reading let mut filter_block_reader = None; let filter_name = format!("filter.{}", fp.name()).as_bytes().to_vec(); let mut metaindexiter = metaindexblock.block.iter(); metaindexiter.seek(&filter_name); if let Some((_key, val)) = metaindexiter.current() { let filter_block_location = BlockHandle::decode(&val).0; if filter_block_location.size() > 0 { let buf = try!(read_bytes(&mut file, &filter_block_location)); filter_block_reader = Some(FilterBlockReader::new_owned(fp, buf)); } } metaindexiter.reset(); Ok(Table { file: file, file_size: size, opt: opt, cmp: Box::new(cmp), footer: footer, filters: filter_block_reader, indexblock: indexblock.block, }) } /// Creates a new table reader operating on internal keys (i.e., InternalKey). This means that /// a different comparator (internal_key_cmp) and a different filter policy /// (InternalFilterPolicy) are used. pub fn new(file: R, size: usize, fp: FP, opt: Options) -> Result<Table<R, InternalFilterPolicy<FP>>> { let mut t = try!(Table::new_raw(file, size, InternalFilterPolicy::new(fp), opt)); t.cmp = Box::new(internal_key_cmp); Ok(t) } fn read_block(&mut self, location: &BlockHandle) -> Result<TableBlock> { let b = try!(TableBlock::read_block(&mut self.file, location)); if !b.verify() { Err(io::Error::new(io::ErrorKind::InvalidData, "Data block failed verification")) } else { Ok(b) } } /// Returns the offset of the block that contains `key`. pub fn approx_offset_of(&self, key: &[u8]) -> usize { let mut iter = self.indexblock.iter(); iter.seek(key); if let Some((_, val)) = iter.current() { let location = BlockHandle::decode(&val).0; return location.offset(); } return self.footer.meta_index.offset(); } // Iterators read from the file; thus only one iterator can be borrowed (mutably) per scope fn iter<'a>(&'a mut self) -> TableIterator<'a, R, FP> { let iter = TableIterator { current_block: self.indexblock.iter(), // just for filling in here current_block_off: 0, index_block: self.indexblock.iter(), table: self, init: false, }; iter } /// Retrieve value from table. This function uses the attached filters, so is better suited if /// you frequently look for non-existing values (as it will detect the non-existence of an /// entry in a block without having to load the block). pub fn get<'a>(&mut self, to: InternalKey<'a>) -> Option<Vec<u8>> { let mut iter = self.iter(); iter.seek(to); if let Some((k, v)) = iter.current() { if k == to { Some(v) } else { None } } else { None } // Future impl: // // let mut index_block = self.indexblock.iter(); // // index_block.seek(to); // // if let Some((past_block, handle)) = index_block.current() { // if cmp(to, &past_block) == Ordering::Less { // ok, found right block: continue // if let Ok(()) = self.load_block(&handle) { // self.current_block.seek(to); // } else { // return None; // }*/ // return None; // } else { // return None; // } // } else { // return None; // } // } } /// This iterator is a "TwoLevelIterator"; it uses an index block in order to get an offset hint /// into the data blocks. pub struct TableIterator<'a, R: 'a + Read + Seek, FP: 'a + FilterPolicy> { table: &'a mut Table<R, FP>, current_block: BlockIter, current_block_off: usize, index_block: BlockIter, init: bool, } impl<'a, R: Read + Seek, FP: FilterPolicy> TableIterator<'a, R, FP> { // Skips to the entry referenced by the next entry in the index block. // This is called once a block has run out of entries. fn skip_to_next_entry(&mut self) -> Result<bool> { if let Some((_key, val)) = self.index_block.next() { self.load_block(&val).map(|_| true) } else { Ok(false) } } // Load the block at `handle` into `self.current_block` fn load_block(&mut self, handle: &[u8]) -> Result<()> { let (new_block_handle, _) = BlockHandle::decode(handle); let block = try!(self.table.read_block(&new_block_handle)); self.current_block = block.block.iter(); self.current_block_off = new_block_handle.offset(); Ok(()) } } impl<'a, R: Read + Seek, FP: FilterPolicy> Iterator for TableIterator<'a, R, FP> { type Item = (Vec<u8>, Vec<u8>); fn next(&mut self) -> Option<Self::Item> { if !self.init { self.init = true; if self.skip_to_next_entry().is_err() { return None; } } if let Some((key, val)) = self.current_block.next() { Some((key, val)) } else { if self.skip_to_next_entry().unwrap_or(false) { self.next() } else { None } } } } impl<'a, R: Read + Seek, FP: FilterPolicy> LdbIterator for TableIterator<'a, R, FP> { // A call to valid() after seeking is necessary to ensure that the seek worked (e.g., no error // while reading from disk) fn seek(&mut self, to: &[u8]) { // first seek in index block, rewind by one entry (so we get the next smaller index entry), // then set current_block and seek there self.index_block.seek(to); if let Some((past_block, handle)) = self.index_block.current() { if (self.table.cmp)(to, &past_block) == Ordering::Less { // ok, found right block: continue if let Ok(()) = self.load_block(&handle) { self.current_block.seek(to); self.init = true; } else { self.reset(); return; } } else { self.reset(); return; } } else { panic!("Unexpected None from current() (bug)"); } } fn prev(&mut self) -> Option<Self::Item> { // happy path: current block contains previous entry if let Some(result) = self.current_block.prev() { Some(result) } else { // Go back one block and look for the last entry in the previous block if let Some((_, handle)) = self.index_block.prev() { if self.load_block(&handle).is_ok() { self.current_block.seek_to_last(); self.current_block.current() } else { self.reset(); None } } else { None } } } fn reset(&mut self) { self.index_block.reset(); self.init = false; } // This iterator is special in that it's valid even before the first call to next(). It behaves // correctly, though. fn valid(&self) -> bool { self.init && (self.current_block.valid() || self.index_block.valid()) } fn current(&self) -> Option<Self::Item> { if self.init { self.current_block.current() } else { None } } } #[cfg(test)] mod tests { use filter::BloomPolicy; use filter::InternalFilterPolicy; use options::Options; use table_builder::TableBuilder; use types::LdbIterator; use key_types::LookupKey; use std::io::Cursor; use super::*; fn build_data() -> Vec<(&'static str, &'static str)> { vec![("abc", "def"), ("abd", "dee"), ("bcd", "asa"), ("bsr", "a00"), ("xyz", "xxx"), ("xzz", "yyy"), ("zzz", "111")] } fn build_table() -> (Vec<u8>, usize) { let mut d = Vec::with_capacity(512); let mut opt = Options::default(); opt.block_restart_interval = 2; opt.block_size = 32; { let mut b = TableBuilder::new(opt, &mut d, BloomPolicy::new(4)); let data = build_data(); for &(k, v) in data.iter() { b.add(k.as_bytes(), v.as_bytes()); } b.finish(); } let size = d.len(); (d, size) } fn build_internal_table() -> (Vec<u8>, usize) { let mut d = Vec::with_capacity(512); let mut opt = Options::default(); opt.block_restart_interval = 2; opt.block_size = 32; let mut i = 0 as u64; let data: Vec<(Vec<u8>, &'static str)> = build_data() .into_iter() .map(|(k, v)| { i += 1; (LookupKey::new(k.as_bytes(), i).internal_key().to_vec(), v) }) .collect(); { let mut b = TableBuilder::new(opt, &mut d, InternalFilterPolicy::new(BloomPolicy::new(4))); for &(ref k, ref v) in data.iter() { b.add(k.as_slice(), v.as_bytes()); } b.finish(); } let size = d.len(); (d, size) } #[test] fn test_table_reader_checksum() { let (mut src, size) = build_table(); println!("{}", size); src[45] = 0; let mut table = Table::new_raw(Cursor::new(&src as &[u8]), size, BloomPolicy::new(4), Options::default()) .unwrap(); assert!(table.filters.is_some()); assert_eq!(table.filters.as_ref().unwrap().num(), 1); { let iter = table.iter(); // Last block is skipped assert_eq!(iter.count(), 3); } { let iter = table.iter(); for (k, _) in iter { if k == build_data()[2].0.as_bytes() { return; } } panic!("Should have hit 3rd record in table!"); } } #[test] fn test_table_iterator_fwd() { let (src, size) = build_table(); let data = build_data(); let mut table = Table::new_raw(Cursor::new(&src as &[u8]), size, BloomPolicy::new(4), Options::default()) .unwrap(); let iter = table.iter(); let mut i = 0; for (k, v) in iter { assert_eq!((data[i].0.as_bytes(), data[i].1.as_bytes()), (k.as_ref(), v.as_ref())); i += 1; } assert_eq!(i, data.len()); } #[test] fn test_table_iterator_filter() { let (src, size) = build_table(); let mut table = Table::new_raw(Cursor::new(&src as &[u8]), size, BloomPolicy::new(4), Options::default()) .unwrap(); let filter_reader = table.filters.clone().unwrap(); let mut iter = table.iter(); loop { if let Some((k, _)) = iter.next() { assert!(filter_reader.key_may_match(iter.current_block_off, &k)); assert!(!filter_reader.key_may_match(iter.current_block_off, "somerandomkey".as_bytes())); } else { break; } } } #[test] fn test_table_iterator_state_behavior() { let (src, size) = build_table(); let mut table = Table::new_raw(Cursor::new(&src as &[u8]), size, BloomPolicy::new(4), Options::default()) .unwrap(); let mut iter = table.iter(); // behavior test // See comment on valid() assert!(!iter.valid()); assert!(iter.current().is_none()); assert!(iter.next().is_some()); let first = iter.current(); assert!(iter.valid()); assert!(iter.current().is_some()); assert!(iter.next().is_some()); assert!(iter.prev().is_some()); assert!(iter.current().is_some()); iter.reset(); assert!(!iter.valid()); assert!(iter.current().is_none()); assert_eq!(first, iter.next()); } #[test] fn test_table_iterator_values() { let (src, size) = build_table(); let data = build_data(); let mut table = Table::new_raw(Cursor::new(&src as &[u8]), size, BloomPolicy::new(4), Options::default()) .unwrap(); let mut iter = table.iter(); let mut i = 0; iter.next(); iter.next(); // Go back to previous entry, check, go forward two entries, repeat // Verifies that prev/next works well. while iter.valid() && i < data.len() { iter.prev(); if let Some((k, v)) = iter.current() { assert_eq!((data[i].0.as_bytes(), data[i].1.as_bytes()), (k.as_ref(), v.as_ref())); } else { break; } i += 1; iter.next(); iter.next(); } assert_eq!(i, 7); } #[test] fn test_table_iterator_seek() { let (src, size) = build_table(); let mut table = Table::new_raw(Cursor::new(&src as &[u8]), size, BloomPolicy::new(4), Options::default()) .unwrap(); let mut iter = table.iter(); iter.seek("bcd".as_bytes()); assert!(iter.valid()); assert_eq!(iter.current(), Some(("bcd".as_bytes().to_vec(), "asa".as_bytes().to_vec()))); iter.seek("abc".as_bytes()); assert!(iter.valid()); assert_eq!(iter.current(), Some(("abc".as_bytes().to_vec(), "def".as_bytes().to_vec()))); } #[test] fn test_table_get() { let (src, size) = build_table(); let mut table = Table::new_raw(Cursor::new(&src as &[u8]), size, BloomPolicy::new(4), Options::default()) .unwrap(); assert!(table.get("aaa".as_bytes()).is_none()); assert_eq!(table.get("abc".as_bytes()), Some("def".as_bytes().to_vec())); assert!(table.get("abcd".as_bytes()).is_none()); assert_eq!(table.get("bcd".as_bytes()), Some("asa".as_bytes().to_vec())); assert_eq!(table.get("zzz".as_bytes()), Some("111".as_bytes().to_vec())); assert!(table.get("zz1".as_bytes()).is_none()); } // This test verifies that the table and filters work with internal keys. This means: // The table contains keys in InternalKey format and it uses a filter wrapped by // InternalFilterPolicy. // All the other tests use raw keys that don't have any internal structure; this is fine in // general, but here we want to see that the other infrastructure works too. #[test] fn test_table_internal_keys() { use key_types::LookupKey; let (src, size) = build_internal_table(); let mut table = Table::new(Cursor::new(&src as &[u8]), size, BloomPolicy::new(4), Options::default()) .unwrap(); let filter_reader = table.filters.clone().unwrap(); // Check that we're actually using internal keys for (ref k, _) in table.iter() { assert_eq!(k.len(), 3 + 8); } let mut iter = table.iter(); loop { if let Some((k, _)) = iter.next() { let lk = LookupKey::new(&k, 123); let userkey = lk.user_key(); assert!(filter_reader.key_may_match(iter.current_block_off, userkey)); assert!(!filter_reader.key_may_match(iter.current_block_off, "somerandomkey".as_bytes())); } else { break; } } } }