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// Copyright (c) The Diem Core Contributors
// SPDX-License-Identifier: Apache-2.0

// Copyright 2021 Conflux Foundation. All rights reserved.
// Conflux is free software and distributed under GNU General Public License.
// See http://www.gnu.org/licenses/

//! This module defines physical storage schema for the transaction accumulator.
//!
//! A hash value is stored on each position.
//! See `storage/accumulator/lib.rs` for details.
//! ```text
//! |<----------key--------->|<-value->|
//! | position in post order |   hash  |
//! ```

use crate::schema::{ensure_slice_len_eq, TRANSACTION_ACCUMULATOR_CF_NAME};
use anyhow::Result;
use byteorder::{BigEndian, ReadBytesExt};
use diem_crypto::HashValue;
use diem_types::proof::position::Position;
use schemadb::{
    define_schema,
    schema::{KeyCodec, ValueCodec},
};
use std::mem::size_of;

define_schema!(
    TransactionAccumulatorSchema,
    Position,
    HashValue,
    TRANSACTION_ACCUMULATOR_CF_NAME
);

impl KeyCodec<TransactionAccumulatorSchema> for Position {
    fn encode_key(&self) -> Result<Vec<u8>> {
        Ok(self.to_postorder_index().to_be_bytes().to_vec())
    }

    fn decode_key(mut data: &[u8]) -> Result<Self> {
        ensure_slice_len_eq(data, size_of::<u64>())?;
        let index = data.read_u64::<BigEndian>()?;
        Position::from_postorder_index(index)
    }
}

impl ValueCodec<TransactionAccumulatorSchema> for HashValue {
    fn encode_value(&self) -> Result<Vec<u8>> { Ok(self.to_vec()) }

    fn decode_value(data: &[u8]) -> Result<Self> {
        Self::from_slice(data).map_err(Into::into)
    }
}

#[cfg(test)]
mod test;