diff options
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/abi-spec.rst | 20 |
1 files changed, 14 insertions, 6 deletions
diff --git a/docs/abi-spec.rst b/docs/abi-spec.rst index 0f4a16b6..3c9dfcf9 100644 --- a/docs/abi-spec.rst +++ b/docs/abi-spec.rst @@ -609,7 +609,9 @@ Through ``abi.encodePacked()``, Solidity supports a non-standard packed mode whe - types shorter than 32 bytes are neither zero padded nor sign extended and - dynamic types are encoded in-place and without the length. -As an example encoding ``int8, bytes1, uint16, string`` with values ``-1, 0x42, 0x2424, "Hello, world!"`` results in: +This packed mode is mainly used for indexed event parameters. + +As an example, the encoding of ``int8(-1), bytes1(0x42), uint16(0x2424), string("Hello, world!")`` results in: .. code-block:: none @@ -619,12 +621,18 @@ As an example encoding ``int8, bytes1, uint16, string`` with values ``-1, 0x42, ^^^^ uint16(0x2424) ^^^^^^^^^^^^^^^^^^^^^^^^^^ string("Hello, world!") without a length field -More specifically, each statically-sized type takes as many bytes as its range has -and dynamically-sized types like ``string``, ``bytes`` or ``uint[]`` are encoded without -their length field. This means that the encoding is ambiguous as soon as there are two -dynamically-sized elements. +More specifically: + - Each value type takes as many bytes as its range has. + - The encoding of a struct or fixed-size array is the concatenation of the + encoding of its members/elements without any separator or padding. + - Mapping members of structs are ignored as usual. + - Dynamically-sized types like ``string``, ``bytes`` or ``uint[]`` are encoded without + their length field. + +In general, the encoding is ambiguous as soon as there are two dynamically-sized elements, +because of the missing length field. If padding is needed, explicit type conversions can be used: ``abi.encodePacked(uint16(0x12)) == hex"0012"``. Since packed encoding is not used when calling functions, there is no special support -for prepending a function selector. +for prepending a function selector. Since the encoding is ambiguous, there is no decoding function. |