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More explanation about the packed encoding.

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chriseth 2017-11-22 10:57:52 +01:00 committed by Alex Beregszaszi
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commit 88e1b68aaf
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docs/abi-spec.rst
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@ -451,13 +451,18 @@ Non-standard Packed Mode
Solidity supports a non-standard packed mode where:
- no :ref:`function selector <abi_function_selector>` is encoded,
- short types are not zero padded and
- 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 ``uint1, bytes1, uint8, string`` with values ``1, 0x42, 0x2424, "Hello, world!"`` results in ::
As an example encoding ``int1, bytes1, uint16, string`` with values ``-1, 0x42, 0x2424, "Hello, world!"`` results in ::
0x0142242448656c6c6f2c20776f726c6421
^^ uint1(1)
0xff42242448656c6c6f2c20776f726c6421
^^ int1(-1)
^^ bytes1(0x42)
^^^^ uint8(0x2424)
^^^^ 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.