pipe BlockContext

方便某些情况下管理“区块”

模块化设计的产物。

数据结构和 Chain 链有几分相似，是其“子集”。

/// Contextual information required to process a new block and either reject or
/// accept it.
pub struct BlockContext<'a> {
    /// The options
    pub opts: Options,
    /// The pow verifier to use when processing a block.
    pub pow_verifier: fn(&BlockHeader) -> Result<(), pow::Error>,
    /// The active txhashset (rewindable MMRs) to use for block processing.
    pub txhashset: &'a mut txhashset::TxHashSet,
    /// The active batch to use for block processing.
    pub batch: store::Batch<'a>,
    /// The verifier cache (caching verifier for rangeproofs and kernel signatures)
    pub verifier_cache: Arc<RwLock<VerifierCache>>,
    /// Recent orphan blocks to avoid double-processing
    pub orphans: Arc<OrphanBlockPool>,
}