evm

v0.1.14

evm v0.1.14 EVM.Helpers

Various helper functions with no other home.

Link to this section Summary

Functions

all_but_one_64th(n)

Defined as Eq.(224) in the Yellow Paper, this is “all but one 64th”, written as L(x)

bit_at(n, at)
bit_position(byte_position)
decode_signed(n)
encode_signed(n)

Encodes signed ints using twos compliment

encode_val(n)
inspect(msg, prefix)

Helper function to print an instruction message

invert(m)

Inverts a map so each key becomes a value, and vice versa

left_pad_bytes(n, size \\ EVM.word_size())

Left pad binary with bytes

read_zero_padded(data, start_pos, read_length)

Reads a length of data from a binary, filling in all unknown values as zero

right_pad_bytes(n, size \\ EVM.word_size())

Right pad binary with bytes

take_n_last_bytes(data, n)

Take the last n bytes of a binary

wrap_address(n)

Wrap ints greater than the maximum allowed address size

wrap_int(n)

Wrap ints greater than the max int around back to 0

Link to this section Functions

Link to this function all_but_one_64th(n) 
all_but_one_64th(integer) :: integer

Defined as Eq.(224) in the Yellow Paper, this is “all but one 64th”, written as L(x).

Examples 

iex> EVM.Helpers.all_but_one_64th(5)
5

iex> EVM.Helpers.all_but_one_64th(1000)
985
Link to this function bit_position(byte_position)
Link to this function decode_signed(n) 
decode_signed(integer | nil) :: EVM.val
Link to this function encode_signed(n) 
encode_signed(integer) :: EVM.val

Encodes signed ints using twos compliment

Examples 

iex> EVM.Helpers.encode_signed(1)
1

iex> EVM.Helpers.encode_signed(-1)
EVM.max_int() - 1
Link to this function encode_val(n) 
encode_val(integer | binary | [integer]) :: [EVM.val]
Link to this function inspect(msg, prefix)

Helper function to print an instruction message.

Link to this function invert(m) 
invert(map) :: map

Inverts a map so each key becomes a value, and vice versa.

Examples 

iex> EVM.Helpers.invert(%{a: 5, b: 10})
%{5 => :a, 10 => :b}

iex> EVM.Helpers.invert(%{dog: "cat"})
%{"cat" => :dog}

iex> EVM.Helpers.invert(%{cow: :moo})
%{moo: :cow}

iex> EVM.Helpers.invert(%{"name" => "bob"})
%{"bob" => "name"}

iex> EVM.Helpers.invert(%{})
%{}
Link to this function left_pad_bytes(n, size \\ EVM.word_size()) 
left_pad_bytes(binary | integer, integer) :: integer

Left pad binary with bytes

Examples 

iex> EVM.Helpers.left_pad_bytes(1, 3)
<<0, 0, 1>>
iex> EVM.Helpers.left_pad_bytes(<<1>>, 3)
<<0, 0, 1>>
iex> EVM.Helpers.left_pad_bytes(<<1, 2, 3>>, 2)
<<1, 2, 3>>
Link to this function read_zero_padded(data, start_pos, read_length) 
read_zero_padded(binary, integer, integer) :: binary

Reads a length of data from a binary, filling in all unknown values as zero.

Examples 

iex> EVM.Helpers.read_zero_padded(<<5, 6, 7>>, 1, 3)
<<6, 7, 0>>

iex> EVM.Helpers.read_zero_padded(<<5, 6, 7>>, 0, 2)
<<5, 6>>

iex> EVM.Helpers.read_zero_padded(<<5, 6, 7>>, 0, 3)
<<5, 6, 7>>

iex> EVM.Helpers.read_zero_padded(<<5, 6, 7>>, 4, 3)
<<0, 0, 0>>
Link to this function right_pad_bytes(n, size \\ EVM.word_size()) 
right_pad_bytes(binary | integer, integer) :: integer

Right pad binary with bytes

Examples 

iex> EVM.Helpers.right_pad_bytes(1, 3)
<<1, 0, 0>>
iex> EVM.Helpers.right_pad_bytes(<<1>>, 3)
<<1, 0, 0>>
iex> EVM.Helpers.right_pad_bytes(<<1, 2, 3>>, 2)
<<1, 2, 3>>
Link to this function take_n_last_bytes(data, n) 
take_n_last_bytes(binary, integer) :: integer

Take the last n bytes of a binary

Link to this function wrap_address(n)

Wrap ints greater than the maximum allowed address size.

Examples 

iex> EVM.Helpers.wrap_address(1)
1

iex> EVM.Helpers.wrap_address(<<1>>)
<<1>>

iex> EVM.Helpers.wrap_address(EVM.Address.max() + 1)
1
Link to this function wrap_int(n) 
wrap_int(integer) :: EVM.val

Wrap ints greater than the max int around back to 0

Examples 

iex> EVM.Helpers.wrap_int(1)
1

iex> EVM.Helpers.wrap_int(EVM.max_int() + 1)
1