Merge pull request #193 from ia0/v2_lib

Add new store (without tests yet)

libraries/persistent_store/src/format.rs

@@ -12,14 +12,13 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// TODO(ia0): Remove when the module is used.
-#![allow(dead_code)]
-
 #[macro_use]
 mod bitfield;
 
-use self::bitfield::*;
-use crate::{usize_to_nat, Nat, Storage, StorageIndex, StoreError, StoreResult};
+#[cfg(test)]
+use self::bitfield::Length;
+use self::bitfield::{count_zeros, num_bits, Bit, Checksum, ConstField, Field};
+use crate::{usize_to_nat, Nat, Storage, StorageIndex, StoreError, StoreResult, StoreUpdate};
 use alloc::vec::Vec;
 use core::cmp::min;
 use core::convert::TryFrom;
@@ -492,6 +491,61 @@ impl Format {
         HEADER_DELETED.set(word);
     }
 
+    /// Returns the capacity required by a transaction.
+    pub fn transaction_capacity(&self, updates: &[StoreUpdate]) -> Nat {
+        match updates.len() {
+            // An empty transaction doesn't consume anything.
+            0 => 0,
+            // Transactions with a single update are optimized by avoiding a marker entry.
+            1 => match &updates[0] {
+                StoreUpdate::Insert { value, .. } => self.entry_size(value),
+                // Transactions with a single update which is a removal don't consume anything.
+                StoreUpdate::Remove { .. } => 0,
+            },
+            // A transaction consumes one word for the marker entry in addition to its updates.
+            _ => 1 + updates.iter().map(|x| self.update_capacity(x)).sum::<Nat>(),
+        }
+    }
+
+    /// Returns the capacity of an update.
+    fn update_capacity(&self, update: &StoreUpdate) -> Nat {
+        match update {
+            StoreUpdate::Insert { value, .. } => self.entry_size(value),
+            StoreUpdate::Remove { .. } => 1,
+        }
+    }
+
+    /// Returns the size of a user entry given its value.
+    pub fn entry_size(&self, value: &[u8]) -> Nat {
+        1 + self.bytes_to_words(usize_to_nat(value.len()))
+    }
+
+    /// Checks if a transaction is valid and returns its sorted keys.
+    ///
+    /// Returns `None` if the transaction is invalid.
+    pub fn transaction_valid(&self, updates: &[StoreUpdate]) -> Option<Vec<Nat>> {
+        if usize_to_nat(updates.len()) > self.max_updates() {
+            return None;
+        }
+        let mut sorted_keys = Vec::with_capacity(updates.len());
+        for update in updates {
+            let key = usize_to_nat(update.key());
+            if key > self.max_key() {
+                return None;
+            }
+            if let Some(value) = update.value() {
+                if usize_to_nat(value.len()) > self.max_value_len() {
+                    return None;
+                }
+            }
+            match sorted_keys.binary_search(&key) {
+                Ok(_) => return None,
+                Err(pos) => sorted_keys.insert(pos, key),
+            }
+        }
+        Some(sorted_keys)
+    }
+
     /// Returns the minimum number of words to represent a given number of bytes.
     ///
     /// # Preconditions

libraries/persistent_store/src/lib.rs

@@ -359,7 +359,9 @@ pub use self::buffer::{BufferCorruptFunction, BufferOptions, BufferStorage};
 #[cfg(feature = "std")]
 pub use self::model::{StoreModel, StoreOperation};
 pub use self::storage::{Storage, StorageError, StorageIndex, StorageResult};
-pub use self::store::{StoreError, StoreRatio, StoreResult, StoreUpdate};
+pub use self::store::{
+    Store, StoreError, StoreHandle, StoreIter, StoreRatio, StoreResult, StoreUpdate,
+};
 
 /// Internal representation of natural numbers.
 ///

libraries/persistent_store/src/model.rs

@@ -14,7 +14,7 @@
 
 use crate::format::Format;
 use crate::{usize_to_nat, StoreError, StoreRatio, StoreResult, StoreUpdate};
-use std::collections::{HashMap, HashSet};
+use std::collections::HashMap;
 
 /// Models the mutable operations of a store.
 ///
@@ -79,38 +79,23 @@ impl StoreModel {
     /// Returns the capacity according to the model.
     pub fn capacity(&self) -> StoreRatio {
         let total = self.format.total_capacity();
-        let used = usize_to_nat(self.content.values().map(|x| self.entry_size(x)).sum());
+        let used = usize_to_nat(
+            self.content
+                .values()
+                .map(|x| self.format.entry_size(x) as usize)
+                .sum(),
+        );
         StoreRatio { used, total }
     }
 
     /// Applies a transaction.
     fn transaction(&mut self, updates: Vec<StoreUpdate>) -> StoreResult<()> {
-        // Fail if too many updates.
-        if updates.len() > self.format.max_updates() as usize {
-            return Err(StoreError::InvalidArgument);
-        }
-        // Fail if an update is invalid.
-        if !updates.iter().all(|x| self.update_valid(x)) {
-            return Err(StoreError::InvalidArgument);
-        }
-        // Fail if updates are not disjoint, i.e. there are duplicate keys.
-        let keys: HashSet<_> = updates.iter().map(|x| x.key()).collect();
-        if keys.len() != updates.len() {
+        // Fail if the transaction is invalid.
+        if self.format.transaction_valid(&updates).is_none() {
             return Err(StoreError::InvalidArgument);
         }
         // Fail if there is not enough capacity.
-        let capacity = match updates.len() {
-            // An empty transaction doesn't consume anything.
-            0 => 0,
-            // Transactions with a single update are optimized by avoiding a marker entry.
-            1 => match &updates[0] {
-                StoreUpdate::Insert { value, .. } => self.entry_size(value),
-                // Transactions with a single update which is a removal don't consume anything.
-                StoreUpdate::Remove { .. } => 0,
-            },
-            // A transaction consumes one word for the marker entry in addition to its updates.
-            _ => 1 + updates.iter().map(|x| self.update_size(x)).sum::<usize>(),
-        };
+        let capacity = self.format.transaction_capacity(&updates) as usize;
         if self.capacity().remaining() < capacity {
             return Err(StoreError::NoCapacity);
         }
@@ -144,25 +129,4 @@ impl StoreModel {
         }
         Ok(())
     }
-
-    /// Returns the word capacity of an update.
-    fn update_size(&self, update: &StoreUpdate) -> usize {
-        match update {
-            StoreUpdate::Insert { value, .. } => self.entry_size(value),
-            StoreUpdate::Remove { .. } => 1,
-        }
-    }
-
-    /// Returns the word capacity of an entry.
-    fn entry_size(&self, value: &[u8]) -> usize {
-        1 + self.format.bytes_to_words(usize_to_nat(value.len())) as usize
-    }
-
-    /// Returns whether an update is valid.
-    fn update_valid(&self, update: &StoreUpdate) -> bool {
-        update.key() <= self.format.max_key() as usize
-            && update
-                .value()
-                .map_or(true, |x| x.len() <= self.format.max_value_len() as usize)
-    }
 }