diff options
| -rw-r--r-- | Changelog.md | 2 | ||||
| -rw-r--r-- | docs/miscellaneous.rst | 46 | ||||
| -rw-r--r-- | solc/CommandLineInterface.cpp | 2 |
3 files changed, 26 insertions, 24 deletions
diff --git a/Changelog.md b/Changelog.md index cb3ccae7..1058fdf5 100644 --- a/Changelog.md +++ b/Changelog.md @@ -1,7 +1,7 @@ ### 0.4.7 (unreleased) Features: - * Code generator: Inject the swarm hash of a metadata file into the bytecode. + * Code generator: Inject the Swarm hash of a metadata file into the bytecode. * Optimizer: Some dead code elimination. Bugfixes: diff --git a/docs/miscellaneous.rst b/docs/miscellaneous.rst index 5b51c4a9..c44b3e9e 100644 --- a/docs/miscellaneous.rst +++ b/docs/miscellaneous.rst @@ -236,21 +236,21 @@ If ``solc`` is called with the option ``--link``, all input files are interprete Contract Metadata ***************** -The Solidity compiler automatically generates a json file, the +The Solidity compiler automatically generates a JSON file, the contract metadata, that contains information about the current contract. -It can be used to query the compiler version, the sourcecode, the ABI +It can be used to query the compiler version, the sources used, the ABI and NatSpec documentation in order to more safely interact with the contract and to verify its source code. -The compiler appends a swarm hash (32 bytes) of that file to the end of the +The compiler appends a Swarm hash of the metadata file to the end of the bytecode (for details, see below) of each contract, so that you can retrieve the file in an authenticated way without having to resort to a centralized data provider. -Of course, you have to publish the metadata file to swarm (or some other service) +Of course, you have to publish the metadata file to Swarm (or some other service) so that others can access it. The file can be output by using ``solc --metadata`` and the file will be called ``ContractName_meta.json``. -It will contain swarm references to the source code, so you have to upload +It will contain Swarm references to the source code, so you have to upload all source files and the metadata file. The metadata file has the following format. The example below is presented in a @@ -282,12 +282,13 @@ Comments are of course also not permitted and used here only for explanatory pur // Required: keccak256 hash of the source file "keccak256": "0x123...", // Required (unless "content" is used, see below): URL to the - // source file, protocol is more or less arbitrary, but a swarm + // source file, protocol is more or less arbitrary, but a Swarm // URL is recommended "url": "bzzr://56ab..." }, "mortal": { - "keccak256": "0x123...", + // Required: keccak256 hash of the source file + "keccak256": "0x234...", // Required (unless "url" is used): literal contents of the source file "content": "contract mortal is owned { function kill() { if (msg.sender == owner) selfdestruct(owner); } }" } @@ -296,15 +297,18 @@ Comments are of course also not permitted and used here only for explanatory pur settings: { // Required for Solidity: Sorted list of remappings - remappings: [":g/dir"], + remappings: [ ":g/dir" ], // Optional: Optimizer settings (enabled defaults to false) - optimizer: {enabled: true, runs: 500}, + optimizer: { + enabled: true, + runs: 500 + }, // Required for Solidity: File and name of the contract or library this // metadata is created for. compilationTarget: { "myFile.sol": "MyContract" }, - // Required for Solidity: Addresses for libraries + // Required for Solidity: Addresses for libraries used libraries: { "MyLib": "0x123123..." } @@ -326,7 +330,7 @@ Encoding of the Metadata Hash in the Bytecode --------------------------------------------- Because we might support other ways to retrieve the metadata file in the future, -the mapping ``{"bzzr0": <swarm hash>}`` is stored +the mapping ``{"bzzr0": <Swarm hash>}`` is stored [CBOR](https://tools.ietf.org/html/rfc7049)-encoded. Since the beginning of that encoding is not easy to find, its length is added in a two-byte big-endian encoding. The current version of the Solidity compiler thus adds the following @@ -334,35 +338,33 @@ to the end of the deployed bytecode:: 0xa1 0x65 'b' 'z' 'z' 'r' '0' 0x58 0x20 <32 bytes swarm hash> 0x00 0x29 -So in order to retrieve the data, you can check the end of the deployed -bytecode to match that pattern and use the swarm hash to retrieve the -file. +So in order to retrieve the data, the end of the deployed bytecode can be checked +to match that pattern and use the Swarm hash to retrieve the file. Usage for Automatic Interface Generation and NatSpec ---------------------------------------------------- The metadata is used in the following way: A component that wants to interact -with a contract (e.g. mist) retrieves the code of the contract, from that -the swarm hash of a file which is then retrieved. +with a contract (e.g. Mist) retrieves the code of the contract, from that +the Swarm hash of a file which is then retrieved. That file is JSON-decoded into a structure like above. -The component can then use the abi to automatically generate a rudimentary +The component can then use the ABI to automatically generate a rudimentary user interface for the contract. -Furthermore, mist can use the userdoc to display a confirmation message to the user +Furthermore, Mist can use the userdoc to display a confirmation message to the user whenever they interact with the contract. Usage for Source Code Verification ---------------------------------- -In order to verify the compilation, sources can be retrieved from swarm +In order to verify the compilation, sources can be retrieved from Swarm via the link in the metadata file. The compiler of the correct version (which is checked to be part of the "official" compilers) is invoked on that input with the specified settings. The resulting bytecode is compared to the data of the creation transaction or CREATE opcode data. -This automatically verifies the metadata since -its hash is part of the bytecode. -Excess data is constructor input data which should be decoded +This automatically verifies the metadata since its hash is part of the bytecode. +Excess data corresponds to the constructor input data, which should be decoded according to the interface and presented to the user. diff --git a/solc/CommandLineInterface.cpp b/solc/CommandLineInterface.cpp index 419a1de0..6e59099a 100644 --- a/solc/CommandLineInterface.cpp +++ b/solc/CommandLineInterface.cpp @@ -482,7 +482,7 @@ Allowed options)", (g_argSignatureHashes.c_str(), "Function signature hashes of the contracts.") (g_argNatspecUserStr.c_str(), "Natspec user documentation of all contracts.") (g_argNatspecDevStr.c_str(), "Natspec developer documentation of all contracts.") - (g_argMetadata.c_str(), "Combined metadata JSON whose swarm hash is stored on-chain.") + (g_argMetadata.c_str(), "Combined Metadata JSON whose Swarm hash is stored on-chain.") ("formal", "Translated source suitable for formal analysis."); desc.add(outputComponents); |