blockchain

Blockchain.info API Go interface.

GoDoc documentation is available here.

Check the test files for example use. However it is along the lines of:

package main

import (
	"fmt"
	"net/http"

	"github.com/qedus/blockchain"
)

func main() {
	bc := blockchain.New(http.DefaultClient)
	address := &blockchain.Address{Address: "an address hash"}
	if err := bc.Request(address); err != nil {
		panic(err)
	}

	// Loop through all the transactions associated with a certain
	// address "an address hash" and print their transaction hashes.
	for {
		tx, err := address.NextTransaction()
		if err == blockchain.TransactionsDone {
			break
		} else if err != nil {
			panic(err)
		}
		fmt.Println(tx.Hash)
	}
}

Blockchain.info API Issues

By creating this client I have noticed a few issues/inconsistencies with the Blockchain.info API. I have taken the stance of not correcting them with this client and instead document them here.

Coinbase block input has an empty hash

Look at this second block for example. You will notice that the coinbase transaction, i.e. the first transaction, contains an input with an empty hash as so inputs: [{}]. It should really be inputs:[]. The effect this has on the Go JSON parser is to produce an empty Input{} struct for all coinbase transactions. Note that coinbase transactions should have no inputs - not empty ones.

The consequence of this is you cannot use len(tx.Inputs) == 0 to determine if a transaction is a coinbase transaction. Instead I have created tx.IsCoinbase() which should be used to determine if a transaction is a coinbase one.

Transaction input and output counts not always correct

Take transaction 2355913fc1a3d71efbc228c69dc5d74340e07b9012377b4b9f6d5522116d0509 in block 312373 for example. The JSON says there are 14 inputs (vin_sz=14) when in fact it only lists 4 in inputs=[...]. Therefore tx.InputCount and tx.OutputCount do not always match len(tx.Inputs) and len(tx.Outputs). However if you select the transaction individually the correct number of inputs are listed in inputs=[...].

It appears that the block API consolidates inputs with the same address where as the individual transaction API does not. This does not appear to be documented. I therefore advise that if you want to iterate through all transaction inputs and outputs you do not rely on tx.InputCount or tx.OutputCount but instead use len(tx.Inputs) and len(tx.Outputs) or their := range ... equivalents.

    // Do NOT do this.
    for i := 0; i < tx.InputCount; i++ {
        ...
    }
    
    // Do this instead.
    for i, input := range tx.Inputs {
        ...
    }

Warning

If you run the tests ensure that you use a dummy set of credentials for wallet_test.go otherwise the test will spend your money.