Official Go implementation of the Ethereum protocol
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go-ethereum/common
Felix Lange 318ad3c1e4 common/hexutil: fix Test{Decode,Unmarshal}Uint64 on 32bit arch (#3363) 8 years ago
..
compiler common/compiler: simplify solc wrapper 8 years ago
hexutil common/hexutil: fix Test{Decode,Unmarshal}Uint64 on 32bit arch (#3363) 8 years ago
math all: update license information 8 years ago
mclock les: light client protocol and API 8 years ago
number all: fix license headers one more time 9 years ago
.gitignore Moved ethutil => common 10 years ago
.travis.yml Moved ethutil => common 10 years ago
README.md common: Update README.md for the current package name 9 years ago
big.go common, crypto: add ICAP functions 9 years ago
big_test.go all: fix license headers one more time 9 years ago
bytes.go internal/ethapi: add personal_sign and fix eth_sign to hash message (#2940) 8 years ago
bytes_test.go common: Remove dead code 9 years ago
debug.go core: added basic chain configuration 9 years ago
format.go common, core, eth/downloader: adjust import log formatting 8 years ago
icap.go common, crypto: add ICAP functions 9 years ago
icap_test.go common, crypto: add ICAP functions 9 years ago
list.go all: fix license headers one more time 9 years ago
main_test.go all: fix license headers one more time 9 years ago
path.go common, node: move datadir defaults into package node 8 years ago
size.go all: fix license headers one more time 9 years ago
size_test.go common: remove windows path functions 9 years ago
test_utils.go all: fix license headers one more time 9 years ago
types.go common: use package hexutil for fixed size type encoding 8 years ago
types_template.go all: fix license headers one more time 9 years ago
types_test.go common: use package hexutil for fixed size type encoding 8 years ago

README.md

common

BuildStatus

The common package contains the ethereum utility library.

Installation

As a subdirectory the main go-ethereum repository, you get it with go get github.com/ethereum/go-ethereum.

Usage

RLP (Recursive Linear Prefix) Encoding

RLP Encoding is an encoding scheme used by the Ethereum project. It encodes any native value or list to a string.

More in depth information about the encoding scheme see the Wiki article.

rlp := common.Encode("doge")
fmt.Printf("%q\n", rlp) // => "\0x83dog"

rlp = common.Encode([]interface{}{"dog", "cat"})
fmt.Printf("%q\n", rlp) // => "\0xc8\0x83dog\0x83cat"
decoded := common.Decode(rlp)
fmt.Println(decoded) // => ["dog" "cat"]

Patricia Trie

Patricie Tree is a merkle trie used by the Ethereum project.

More in depth information about the (modified) Patricia Trie can be found on the Wiki.

The patricia trie uses a db as backend and could be anything as long as it satisfies the Database interface found in common/db.go.

db := NewDatabase()

// db, root
trie := common.NewTrie(db, "")

trie.Put("puppy", "dog")
trie.Put("horse", "stallion")
trie.Put("do", "verb")
trie.Put("doge", "coin")

// Look up the key "do" in the trie
out := trie.Get("do")
fmt.Println(out) // => verb

trie.Delete("puppy")

The patricia trie, in combination with RLP, provides a robust, cryptographically authenticated data structure that can be used to store all (key, value) bindings.

// ... Create db/trie

// Note that RLP uses interface slices as list
value := common.Encode([]interface{}{"one", 2, "three", []interface{}{42}})
// Store the RLP encoded value of the list
trie.Put("mykey", value)

Value

Value is a Generic Value which is used in combination with RLP data or ([])interface{} structures. It may serve as a bridge between RLP data and actual real values and takes care of all the type checking and casting. Unlike Go's reflect.Value it does not panic if it's unable to cast to the requested value. It simple returns the base value of that type (e.g. Slice() returns []interface{}, Uint() return 0, etc).

Creating a new Value

NewEmptyValue() returns a new *Value with it's initial value set to a []interface{}

AppendList() appends a list to the current value.

Append(v) appends the value (v) to the current value/list.

val := common.NewEmptyValue().Append(1).Append("2")
val.AppendList().Append(3)

Retrieving values

Get(i) returns the i item in the list.

Uint() returns the value as an unsigned int64.

Slice() returns the value as a interface slice.

Str() returns the value as a string.

Bytes() returns the value as a byte slice.

Len() assumes current to be a slice and returns its length.

Byte() returns the value as a single byte.

val := common.NewValue([]interface{}{1,"2",[]interface{}{3}})
val.Get(0).Uint() // => 1
val.Get(1).Str()  // => "2"
s := val.Get(2)   // => Value([]interface{}{3})
s.Get(0).Uint()   // => 3

Decoding

Decoding streams of RLP data is simplified

val := common.NewValueFromBytes(rlpData)
val.Get(0).Uint()

Encoding

Encoding from Value to RLP is done with the Encode method. The underlying value can be anything RLP can encode (int, str, lists, bytes)

val := common.NewValue([]interface{}{1,"2",[]interface{}{3}})
rlp := val.Encode()
// Store the rlp data
Store(rlp)