这是一个看起来复杂，实际也真复杂的模块。违法的，直接拒绝；违规的，进行处罚。
但我们可以用排除法，先将如下和数方法进行筛选：
数据查询、检查判断、逻辑判断、可重复操作，剩下各个方法才是我们的重点关注对象。
Blockchain_Start
启动软件
/* do initialisation , setup storage, put genesis block and chain in store
This is the first component to get up
Global parameters are picked up from the config package
*/
checkpoints.LoadCheckPoints
Bolt_backend
Mempool
Generate_Genesis_Block
Store_BL/Store_Block_Topological_order/Store_TOPO_HEIGHT/Store_TOP_HEIGHT/store_TIPS
Initialise_Chain_From_DB
init_hard_forks
clean_up_valid_cache
Initialise_Chain_From_DB
从数据库初始化“链”数据
// this function is called to read blockchain state from DB
// It is callable at any point in time
Load_TOP_HEIGHT
load_TIPS
Shutdown
停止软件的运行
// before shutdown , make sure p2p is confirmed stopped
为了解耦，这里不直接操作 p2p
但直接操作 Mempool 和 store
Get_Height
// get top unstable height
// this is obtained by getting the highest topo block and getting its height
先从系统得到 topo 高度，然后根据它找到区块，再根据区块得到其高度。
Get_Stable_Height
// get height where chain is now stable
找到指定的几个 TIP （当前未端区块）的共同祖先。
封装了 find_common_base
Get_TIPS
从数据库获取当前几个末端区块
Get_Top_ID
Get_Difficulty
Get_Cumulative_Difficulty
伪实现，始终返回 0
Get_Median_Block_Size
Get_Network_HashRate
Block_Exists
指定哈希，区块是否存在数据库？
// confirm whether the block exist in the data
// this only confirms whether the block has been downloaded
// a separate check is required, whether the block is valid ( satifies PoW and other conditions)
// we will not add a block to store, until it satisfies PoW
sort_descending_by_cumulative_difficulty
按累积难度降序排序，如果难度相同，则按区块ID排序。
它是下面 SortTips 的核心
// Heighest node weight is ordered first, the condition is reverted see eg. at https://golang.org/pkg/sort/#Slice
// if weights are equal, nodes are sorted by their block ids which will never collide , hopefullly
// block ids are sorted by lowest byte first diff
sort_ascending_by_height
SortTips
按"累积挖矿难度"进行排！
和所谓的“最重子树”有异曲同工之妙。
// this will sort the tips based on cumulative difficulty and/or block ids
// the tips will sorted in descending order
Load_Block_Cumulative_Difficulty
sort_descending_by_cumulative_difficulty
封装上面的按累积难度排序
isblock_SideBlock
主要根据高度，判断指定区块是不是副块。
既是程序需要，又是激励机制的一部分。
后续会影响奖励，之前是 67%，现在是 8%
（特有解决方案）
// side blocks are blocks which lost the race the to become part
// of main chain, but there transactions are honoured,
// they are given 67 % reward
// a block is a side block if it satisfies the following condition
// if block height is less than or equal to height of past 8 topographical blocks
// this is part of consensus rule
// this is the topoheight of this block itself
根据当前区块哈希，得到当前区块，得到其高度（记为 block_height）
根据当前链拓扑高度，逆序获取最后一个区块，得到其高度（记为 previous_height）
如果 block_height <= previous_height，则当前区块为“副块”。
因为，如果它是“主块”的话，它的高度理应比当前的高。
client_protocol
交易费用激励机制，重复交易、冲突交易不给手续费。
运行存储于交易上的智能合约代码。
主要作用是计算手续费！
重复交易不提供手续费。
还有就是运行合约代码。
（特有解决方案）
// runs the client protocol which includes the following operations
// if any TX are being duplicate or double-spend ignore them
// mark all the valid transactions as valid
// mark all invalid transactions as invalid
// calculate total fees based on valid TX
// we need NOT check ranges/ring signatures here, as they have been done already by earlier steps
client_protocol_reverse
// this undoes everything that is done by client protocol
// NOTE: this will have any effect, only if client protocol has been run on this block earlier
revoke_keyimages
Store_TX_Height
mark_TX
只要还没有最终确定，操作是可以撤消、还原的，这也是协议的一部分，也是“共识”的一部分。
transaction_scavenger
// scavanger for transactions from rusty/stale tips to reinsert them into pool
做了太久的孤儿
主要是根据时间限制，如果区块老旧，应当把其打包的交易重新放入交易池
Is_Block_Orphan
通过计算得到，但不做标记（存储结果）。
// Finds whether a block is orphan
// since we donot store any fields, we need to calculate/find the block as orphan
// using an algorithm
// if the block is NOT topo ordered , it is orphan/stale
Is_TX_Orphan
// this is used to find if a tx is orphan, YES orphan TX
// these can occur during when they are detect to be double-spended on
// so the TX becomes orphan ( chances are less may be less that .000001 % but they are there)
// if a tx is not valid in any of the blocks, it has been mined it is orphan
BlockCheckSum
// this is used to for quick syncs as entire blocks as SHA1,
// entires block can skipped for verification, if checksum matches what the devs have stored
mark_keyimages
// this function will mark all the key images present in the tx as requested
// this is done so as they cannot be respent
// mark is int64 height
consume_keyimages
//this will mark all the keyimages present in this TX as spent
//this is done so as an input cannot be spent twice
标记“密钥镜像”已被使用（单独存储）
revoke_keyimages
//this will mark all the keyimages present in this TX as unspent
//this is required during client protocol runs
Get_TX
/* this will only give you access to transactions which have been mined */
从数据库加载已被打包的区块
Calculate_Height_At_Tips
根据几个 Tip 获得高度（取最大值）
（特有解决方案）
// This will get the biggest height of tip for hardfork version and other calculations
// get biggest height of parent, add 1
IsLagging
时钟，我们是否滞后？
// verifies whether we are lagging
// return true if we need resync
// returns false if we are good and resync is not required
Expand_Transaction_v2
对交易补充数据，数据是重复的，非必须的。
数据：指的密钥镜像、环成员数据，在其它地方已经有体现。
作用：更全面的安全考虑，以及后续使用方便。
补充 RctSignature.MlsagSigs.II 和 RctSignature.MixRing
并保证通过验证
（特有解决方案）
// This function will expand a transaction with all the missing info being reconstitued from the blockchain
// this also increases security since data is coming from the chain or being calculated
// basically this places data for ring signature verification
// REMEMBER to expand key images from the blockchain
Block_Count_Vout
统计该区块所有“输出”的总数
// this function count all the vouts of the block,
// this function exists here because only the chain knows the tx
Rewind_Chain
// this function will rewind the chain from the topo height one block at a time
// this function also runs the client protocol in reverse and also deletes the block from the storage
由客户端操作
重新组织“链”的拓扑结构
自己扩展，不上链，自己可修改
我们向其它节点发送请求，尝试同步数据。
结果发现我们反而领先了？！
这种情况下，先进行自我检查，并“尝试回滚本地数据”。有则改之，无则加勉。
然后重新发送请求，等待响应。
buildReachability_internal
// build reachability graph upto 2*config deeps to answer reachability queries
buildReachability
// build reachability graph upto 2*limit deeps to answer reachability queries
VerifyNonReachability
// this is part of consensus rule, 2 tips cannot refer to their common parent
不能恶意引用末端区块，会被直接拒绝。
BuildReachableBlocks
// used in the difficulty calculation for consensus and while scavenging
BuildReachabilityKeyImages
// this is part of consensus rule, reachable blocks cannot have keyimages collision with new blocks
// this is to avoid dishonest miners including dead transactions
IsBlockSyncBlockHeight
// sync blocks have the following specific property
// 1) the block is singleton at this height
// basically the condition allow us to confirm weight of future blocks with reference to sync blocks
// these are the one who settle the chain and guarantee it
IsBlockSyncBlockHeightSpecific
FindTipBase
// base of a tip is last known sync point
// weight of bases in mentioned in term of height
// this must not employ any cache
FindTipWorkScore_internal
// this will find the sum of work done ( skipping any repetive nodes )
// all the information is privided in unique_map
FindTipWorkScore
// find the score of the tip in reference to a base (NOTE: base is always a sync block otherwise results will be wrong )
find_common_base
找到几个 Tip 共有的祖先，也就是其分歧点
（特有解决该当，涉及到算法）
// this function finds a common base which can be used to compare tips
// weight is replace by height
find_best_tip
核心是“累积挖矿难度”！（注意，叔块对应的难度已经考虑进来了）
GHOST，贪婪最重可见子树协议，这是其一种实现方式。
理论上：大算力，会影响主链的选择（确定主链）。这也符合直觉。
找到最佳 Tip
最佳 Tip 可做为父块，其余 Tip 可做为叔块
（特有解决方案，涉及到算法）
// this function finds a common base which can be used to compare tips based on cumulative difficulty
calculate_mainchain_distance_internal_recursive
按累积难度降序排序
（特有解决方案，涉及算法）
// Heighest node weight is ordered first, the condition is reverted see eg. at https://golang.org/pkg/sort/#Slice
// if weights are equal, nodes are sorted by their block ids which will never collide , hopefullly
// block ids are sorted by lowest byte first diff
calculate_mainchain_distance
Generate_Full_Order
BlockDAG 的全排序！
先获得几个 tips 的后后一个共同祖先，然后找出当前最优解。
BlockDAG 核心技术之一。
（特有解决方案）
// converts a DAG's partial order into a full order, this function is recursive
// generate full order should be only callled on the basis of base blocks which satisfy sync block properties as follows
// generate full order is called on maximum weight tip at every tip change
// blocks are ordered recursively, till we find a find a block which is already in the chain
Load_Block_Topological_order
获得区块在全排序里的排序序号！
先获得几个 tips 的后后一个共同祖先，然后找出当前最优解。
WriteBlockChainTree
其它：
除了 blockchain.go 文件，其它文件下，也有很多 chain *Blockchain 实例方法。
PoW 应用最长链规则（Longest Chain Rule）或者最重链规则（GHOST）选择出有效的区块链。