      1
      2
      3
      4
      5
      6
      7
      8
      9
     10
     11
     12
     13
     14
     15
     16
     17
     18
     19
     20
     21
     22
     23
     24
     25
     26
     27
     28
     29
     30
     31
     32
     33
     34
     35
     36
     37
     38
     39
     40
     41
     42
     43
     44
     45
     46
     47
     48
     49
     50
     51
     52
     53
     54
     55
     56
     57
     58
     59
     60
     61
     62
     63
     64
     65
     66
     67
     68
     69
     70
     71
     72
     73
     74
     75
     76
     77
     78
     79
     80
     81
     82
     83
     84
     85
     86
     87
     88
     89
     90
     91
     92
     93
     94
     95
     96
     97
     98
     99
    100
    101
    102
    103
    104
    105
    106
    107
    108
    109
    110
    111
    112
    113
    114
    115
    116
    117
    118
    119
    120
    121
    122
    123
    124
    125
    126
    127
    128
    129
    130
    131
    132
    133
    134
    135
    136
    137
    138
    139
    140
    141
    142
    143
    144
    145
    146
    147
    148
    149
    150
    151
    152
    153
    154
    155
    156
    157
    158
    159
    160
    161
    162
    163
    164
    165
    166
    167
    168
    169
    170
    171
    172
    173
    174
    175
    176
    177
    178
    179
    180
    181
    182
    183
    184
    185
    186
    187
    188
    189
    190
    191
    192
    193
    194
    195
    196
    197
    198
    199
    200
    201
    202
    203
    204
    205
    206
    207
    208
    209
    210
    211
    212
    213
    214
    215
    216
    217
    218
    219
    220
    221
    222
    223
    224
    225
    226
    227
    228
    229
    230
    231
    232
    233
    234
    235
    236
    237
    238
    239
    240
    241
    242
    243
    244
    245
    246
    247
    248
    249
    250
    251
    252
    253
    254
    255
    256
    257
    258
    259
    260
    261
    262
    263
    264
    265
    266
    267
    268
    269
    270
    271
    272
    273
    274
    275
    276
    277
    278
    279
    280
    281
    282
    283
    284
    285
    286
    287
    288
    289
    290
    291
    292
    293
    294
    295
    296
    297

    // Copyright 2015-2017 Parity Technologies (UK) Ltd.
    // This file is part of Parity.

    // Parity is free software: you can redistribute it and/or modify
    // it under the terms of the GNU General Public License as published by
    // the Free Software Foundation, either version 3 of the License, or
    // (at your option) any later version.

    // Parity is distributed in the hope that it will be useful,
    // but WITHOUT ANY WARRANTY; without even the implied warranty of
    // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    // GNU General Public License for more details.

    // You should have received a copy of the GNU General Public License
    // along with Parity.  If not, see <http://www.gnu.org/licenses/>.

    //! Reference-counted memory-based `HashDB` implementation.

    use hash::*;
    use rlp::*;
    use sha3::*;
    use hashdb::*;
    use heapsize::*;
    use std::mem;
    use std::collections::HashMap;
    use std::collections::hash_map::Entry;

    /// Reference-counted memory-based `HashDB` implementation.
    ///
    /// Use `new()` to create a new database. Insert items with `insert()`, remove items
    /// with `remove()`, check for existence with `containce()` and lookup a hash to derive
    /// the data with `get()`. Clear with `clear()` and purge the portions of the data
    /// that have no references with `purge()`.
    ///
    /// # Example
    /// ```rust
    /// extern crate ethcore_util;
    /// use ethcore_util::hashdb::*;
    /// use ethcore_util::memorydb::*;
    /// fn main() {
    ///   let mut m = MemoryDB::new();
    ///   let d = "Hello world!".as_bytes();
    ///
    ///   let k = m.insert(d);
    ///   assert!(m.contains(&k));
    ///   assert_eq!(m.get(&k).unwrap(), d);
    ///
    ///   m.insert(d);
    ///   assert!(m.contains(&k));
    ///
    ///   m.remove(&k);
    ///   assert!(m.contains(&k));
    ///
    ///   m.remove(&k);
    ///   assert!(!m.contains(&k));
    ///
    ///   m.remove(&k);
    ///   assert!(!m.contains(&k));
    ///
    ///   m.insert(d);
    ///   assert!(!m.contains(&k));

    ///   m.insert(d);
    ///   assert!(m.contains(&k));
    ///   assert_eq!(m.get(&k).unwrap(), d);
    ///
    ///   m.remove(&k);
    ///   assert!(!m.contains(&k));
    /// }
    /// ```
    #[derive(Default, Clone, PartialEq)]
    pub struct MemoryDB {
    	data: H256FastMap<(DBValue, i32)>,
    }

    impl MemoryDB {
    	/// Create a new instance of the memory DB.
    	pub fn new() -> MemoryDB {
    		MemoryDB {
    			data: H256FastMap::default(),
    		}
    	}

    	/// Clear all data from the database.
    	///
    	/// # Examples
    	/// ```rust
    	/// extern crate ethcore_util;
    	/// use ethcore_util::hashdb::*;
    	/// use ethcore_util::memorydb::*;
    	/// fn main() {
    	///   let mut m = MemoryDB::new();
    	///   let hello_bytes = "Hello world!".as_bytes();
    	///   let hash = m.insert(hello_bytes);
    	///   assert!(m.contains(&hash));
    	///   m.clear();
    	///   assert!(!m.contains(&hash));
    	/// }
    	/// ```
    	pub fn clear(&mut self) {
    		self.data.clear();
    	}

    	/// Purge all zero-referenced data from the database.
    	pub fn purge(&mut self) {
    		let empties: Vec<_> = self.data.iter()
    			.filter(|&(_, &(_, rc))| rc == 0)
    			.map(|(k, _)| k.clone())
    			.collect();
    		for empty in empties { self.data.remove(&empty); }
    	}

    	/// Return the internal map of hashes to data, clearing the current state.
    	pub fn drain(&mut self) -> H256FastMap<(DBValue, i32)> {
    		mem::replace(&mut self.data, H256FastMap::default())
    	}

    	/// Grab the raw information associated with a key. Returns None if the key
    	/// doesn't exist.
    	///
    	/// Even when Some is returned, the data is only guaranteed to be useful
    	/// when the refs > 0.
    	pub fn raw(&self, key: &H256) -> Option<(DBValue, i32)> {
    		if key == &SHA3_NULL_RLP {
    			return Some((DBValue::from_slice(&NULL_RLP_STATIC), 1));
    		}
    		self.data.get(key).cloned()
    	}

    	/// Returns the size of allocated heap memory
    	pub fn mem_used(&self) -> usize {
    		self.data.heap_size_of_children()
    	}

    	/// Remove an element and delete it from storage if reference count reaches zero.
    	/// If the value was purged, return the old value.
    	pub fn remove_and_purge(&mut self, key: &H256) -> Option<DBValue> {
    		if key == &SHA3_NULL_RLP {
    			return None;
    		}
    		match self.data.entry(key.clone()) {
    			Entry::Occupied(mut entry) =>
    				if entry.get().1 == 1 {
    					Some(entry.remove().0)
    				} else {
    					entry.get_mut().1 -= 1;
    					None
    				},
    			Entry::Vacant(entry) => {
    				entry.insert((DBValue::new(), -1));
    				None
    			}
    		}
    	}

    	/// Consolidate all the entries of `other` into `self`.
    	pub fn consolidate(&mut self, mut other: Self) {
    		for (key, (value, rc)) in other.drain() {
    			match self.data.entry(key) {
    				Entry::Occupied(mut entry) => {
    					if entry.get().1 < 0 {
    						entry.get_mut().0 = value;
    					}

    					entry.get_mut().1 += rc;
    				}
    				Entry::Vacant(entry) => {
    					entry.insert((value, rc));
    				}
    			}
    		}
    	}
    }

    static NULL_RLP_STATIC: [u8; 1] = [0x80; 1];

    impl HashDB for MemoryDB {
    	fn get(&self, key: &H256) -> Option<DBValue> {
    		if key == &SHA3_NULL_RLP {
    			return Some(DBValue::from_slice(&NULL_RLP_STATIC));
    		}

    		match self.data.get(key) {
    			Some(&(ref d, rc)) if rc > 0 => Some(d.clone()),
    			_ => None
    		}
    	}

    	fn keys(&self) -> HashMap<H256, i32> {
    		self.data.iter().filter_map(|(k, v)| if v.1 != 0 {Some((k.clone(), v.1))} else {None}).collect()
    	}

    	fn contains(&self, key: &H256) -> bool {
    		if key == &SHA3_NULL_RLP {
    			return true;
    		}

    		match self.data.get(key) {
    			Some(&(_, x)) if x > 0 => true,
    			_ => false
    		}
    	}

    	fn insert(&mut self, value: &[u8]) -> H256 {
    		if value == &NULL_RLP {
    			return SHA3_NULL_RLP.clone();
    		}
    		let key = value.sha3();
    		if match self.data.get_mut(&key) {
    			Some(&mut (ref mut old_value, ref mut rc @ -0x80000000i32 ... 0)) => {
    				*old_value = DBValue::from_slice(value);
    				*rc += 1;
    				false
    			},
    			Some(&mut (_, ref mut x)) => { *x += 1; false } ,
    			None => true,
    		}{	// ... None falls through into...
    			self.data.insert(key.clone(), (DBValue::from_slice(value), 1));
    		}
    		key
    	}

    	fn emplace(&mut self, key: H256, value: DBValue) {
    		if &*value == &NULL_RLP {
    			return;
    		}

    		match self.data.get_mut(&key) {
    			Some(&mut (ref mut old_value, ref mut rc @ -0x80000000i32 ... 0)) => {
    				*old_value = value;
    				*rc += 1;
    				return;
    			},
    			Some(&mut (_, ref mut x)) => { *x += 1; return; } ,
    			None => {},
    		}
    		// ... None falls through into...
    		self.data.insert(key, (value, 1));
    	}

    	fn remove(&mut self, key: &H256) {
    		if key == &SHA3_NULL_RLP {
    			return;
    		}

    		if match self.data.get_mut(key) {
    			Some(&mut (_, ref mut x)) => { *x -= 1; false }
    			None => true
    		}{	// ... None falls through into...
    			self.data.insert(key.clone(), (DBValue::new(), -1));
    		}
    	}
    }

    #[test]
    fn memorydb_remove_and_purge() {
    	let hello_bytes = b"Hello world!";
    	let hello_key = hello_bytes.sha3();

    	let mut m = MemoryDB::new();
    	m.remove(&hello_key);
    	assert_eq!(m.raw(&hello_key).unwrap().1, -1);
    	m.purge();
    	assert_eq!(m.raw(&hello_key).unwrap().1, -1);
    	m.insert(hello_bytes);
    	assert_eq!(m.raw(&hello_key).unwrap().1, 0);
    	m.purge();
    	assert_eq!(m.raw(&hello_key), None);

    	let mut m = MemoryDB::new();
    	assert!(m.remove_and_purge(&hello_key).is_none());
    	assert_eq!(m.raw(&hello_key).unwrap().1, -1);
    	m.insert(hello_bytes);
    	m.insert(hello_bytes);
    	assert_eq!(m.raw(&hello_key).unwrap().1, 1);
    	assert_eq!(&*m.remove_and_purge(&hello_key).unwrap(), hello_bytes);
    	assert_eq!(m.raw(&hello_key), None);
    	assert!(m.remove_and_purge(&hello_key).is_none());
    }

    #[test]
    fn consolidate() {
    	let mut main = MemoryDB::new();
    	let mut other = MemoryDB::new();
    	let remove_key = other.insert(b"doggo");
    	main.remove(&remove_key);

    	let insert_key = other.insert(b"arf");
    	main.emplace(insert_key, DBValue::from_slice(b"arf"));

    	main.consolidate(other);

    	let overlay = main.drain();

    	assert_eq!(overlay.get(&remove_key).unwrap(), &(DBValue::from_slice(b"doggo"), 0));
    	assert_eq!(overlay.get(&insert_key).unwrap(), &(DBValue::from_slice(b"arf"), 2));
    }

# Help

## Keyboard Shortcuts

?
  Show this help dialog
S
  Focus the search field
⇤
  Move up in search results
⇥
  Move down in search results
⏎
  Go to active search result
+
  Collapse/expand all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)