Helper functions for ABI's math functions.
API Functions
| Function | Arity | Description | Param Kinds |
|---|---|---|---|
unpad | 3 | Inverse of pad/4. Reads size_in_bytes of content out of data, skipping 32-byte-slot padding on the matching side. | data: value, size_in_bytes: value, padding_direction: value |
pad | 4 | Pad a binary up to the next 32-byte ABI word boundary, with side and fill byte chosen by argument. | bin: value, size_in_bytes: value, direction: value, opts: value |
kec | 1 | Compute the keccak-256 hash of a binary input. The hash function used throughout Ethereum and the ABI spec for selector and event-topic derivation. | data: value |
mod | 2 | Compute integer modulo with sign-aware behavior, returning a non-negative result for negative dividends. | x: value, n: value |
Summary
Functions
Returns the keccak sha256 of a given input.
Simple function to compute modulo function to work on integers of any sign.
Pads a binary up to the next 32-byte ABI word boundary.
Inverse of pad/4. Reads size_in_bytes of content out of data,
skipping 32-byte-slot padding on the side matching padding_direction
(:left for left-padded types like address, :right for right-padded
types like bytes<M> and string). Returns {value, rest}, where
rest is whatever follows the padded word in data.
Functions
Returns the keccak sha256 of a given input.
Examples
iex> ABI.Math.kec("hello world")
<<71, 23, 50, 133, 168, 215, 52, 30, 94, 151, 47, 198, 119, 40, 99,
132, 248, 2, 248, 239, 66, 165, 236, 95, 3, 187, 250, 37, 76, 176,
31, 173>>
iex> ABI.Math.kec(<<0x01, 0x02, 0x03>>)
<<241, 136, 94, 218, 84, 183, 160, 83, 49, 140, 212, 30, 32, 147, 34,
13, 171, 21, 214, 83, 129, 177, 21, 122, 54, 51, 168, 59, 253, 92,
146, 57>>@spec mod(integer(), pos_integer()) :: non_neg_integer()
Simple function to compute modulo function to work on integers of any sign.
Examples
iex> ABI.Math.mod(5, 2)
1
iex> ABI.Math.mod(-5, 1337)
1332
iex> ABI.Math.mod(1337 + 5, 1337)
5
iex> ABI.Math.mod(0, 1337)
0
iex> ABI.Math.mod(-7, 5)
3
iex> ABI.Math.mod(-1338, 1337)
1336@spec pad(binary(), non_neg_integer(), :left | :right, keyword()) :: binary()
Pads a binary up to the next 32-byte ABI word boundary.
size_in_bytes is the logical field width used to compute the word
boundary — not necessarily byte_size(bin). The output is always rounded
up from size_in_bytes to a 32-byte multiple. bin may be shorter than
size_in_bytes (callers like encode_int/encode_uint pass a target
slot size and let padding absorb the difference); encode_bytes passes
byte_size(bin) directly.
direction is :left for left-aligned types like uint/int/address,
:right for right-padded types like bytes<M> and string. Pass
fill_byte: <<0xFF>> for signed sign-extension; defaults to <<0x00>>.
Examples
iex> ABI.Math.pad(<<1, 2, 3>>, 3, :left)
<<0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3>>
iex> ABI.Math.pad(<<1, 2, 3>>, 3, :right)
<<1, 2, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0>>@spec unpad(binary(), non_neg_integer(), :left | :right) :: {binary(), binary()}
Inverse of pad/4. Reads size_in_bytes of content out of data,
skipping 32-byte-slot padding on the side matching padding_direction
(:left for left-padded types like address, :right for right-padded
types like bytes<M> and string). Returns {value, rest}, where
rest is whatever follows the padded word in data.
Examples
iex> ABI.Math.unpad(
...> <<0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
...> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3>>,
...> 3,
...> :left
...> )
{<<1, 2, 3>>, <<>>}
iex> ABI.Math.unpad(
...> <<1, 2, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
...> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
...> 9, 9>>,
...> 3,
...> :right
...> )
{<<1, 2, 3>>, <<9, 9>>}