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Mention other keys in metadata mapping.
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@ -121,9 +121,10 @@ Encoding of the Metadata Hash in the Bytecode
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Because we might support other ways to retrieve the metadata file in the future,
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the mapping ``{"bzzr0": <Swarm hash>}`` is stored
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`CBOR <https://tools.ietf.org/html/rfc7049>`_-encoded. Since the beginning of that
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`CBOR <https://tools.ietf.org/html/rfc7049>`_-encoded. Since the mapping might
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contain more keys (see below) and the beginning of that
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encoding is not easy to find, its length is added in a two-byte big-endian
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encoding. The current version of the Solidity compiler thus adds the following
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encoding. The current version of the Solidity compiler usually adds the following
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to the end of the deployed bytecode::
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0xa1 0x65 'b' 'z' 'z' 'r' '0' 0x58 0x20 <32 bytes swarm hash> 0x00 0x29
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@ -131,6 +132,14 @@ to the end of the deployed bytecode::
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So in order to retrieve the data, the end of the deployed bytecode can be checked
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to match that pattern and use the Swarm hash to retrieve the file.
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.. note::
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The CBOR mapping can also contain other keys, so it is better to fully
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decode the data instead of relying on it starting with ``0xa165``.
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For example, if any experimental features that affect code generation
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are used, the mapping will also contain ``"experimental": true``.
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Furthermore, we are planning to add the compiler version to the mapping
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to ease source-verification and scanning for bugs.
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.. note::
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The compiler currently uses the "swarm version 0" hash of the metadata,
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but this might change in the future, so do not rely on this sequence
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