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func NewBlockTemplate

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NewBlockTemplate returns a new block template that is ready to be solved using the transactions from the passed transaction source pool and a coinbase that either pays to the passed address if it is not nil, or a coinbase that is redeemable by anyone if the passed address is nil. The nil address functionality is useful since there are cases such as the getblocktemplate RPC where external mining software is responsible for creating their own coinbase which will replace the one generated for the block template. Thus the need to have configured address can be avoided.

The transactions selected and included are prioritized according to several factors. First, each transaction has a priority calculated based on its value, age of inputs, and size. Transactions which consist of larger amounts, older inputs, and small sizes have the highest priority. Second, a fee per kilobyte is calculated for each transaction. Transactions with a higher fee per kilobyte are preferred. Finally, the block generation related policy settings are all taken into account.

Transactions which only spend outputs from other transactions already in the block chain are immediately added to a priority queue which either prioritizes based on the priority (then fee per kilobyte) or the fee per kilobyte (then priority) depending on whether or not the BlockPrioritySize policy setting allots space for high-priority transactions. Transactions which spend outputs from other transactions in the source pool are added to a dependency map so they can be added to the priority queue once the transactions they depend on have been included.

Once the high-priority area (if configured) has been filled with transactions, or the priority falls below what is considered high-priority, the priority queue is updated to prioritize by fees per kilobyte (then priority).

When the fees per kilobyte drop below the TxMinFreeFee policy setting, the transaction will be skipped unless the BlockMinSize policy setting is nonzero, in which case the block will be filled with the low-fee/free transactions until the block size reaches that minimum size.

Any transactions which would cause the block to exceed the BlockMaxSize policy setting, exceed the maximum allowed signature operations per block, or otherwise cause the block to be invalid are skipped.

Given the above, a block generated by this function is of the following form:

 -----------------------------------  --  --
|      Coinbase Transaction         |   |   |
|-----------------------------------|   |   |
|                                   |   |   | ----- policy.BlockPrioritySize
|   High-priority Transactions      |   |   |
|                                   |   |   |
|-----------------------------------|   | --
|                                   |   |
|                                   |   |
|                                   |   |--- policy.BlockMaxSize
|  Transactions prioritized by fee  |   |
|  until <= policy.TxMinFreeFee     |   |
|                                   |   |
|                                   |   |
|                                   |   |
|-----------------------------------|   |
|  Low-fee/Non high-priority (free) |   |
|  transactions (while block size   |   |
|  <= policy.BlockMinSize)          |   |
 -----------------------------------  --

NewBlockTemplate is referenced in 1 repository