bitcoin/doc/shared-libraries.md
Cory Fields 25dc87e6f8 libconsensus: deprecate
This library has existed for nearly 10 years with very little known uptake or
impact. It has become a maintenance burden. In several cases it dictates our
code/library structure (for example necessitating LIBBITCOIN_CRYPTO_BASE), as
well as build-system procedures (building multiple copies of object files
especially for the lib).

Several discussions have arisen wrt migrating it to CMake and it has become
difficult to justify adding more complexity for a library that is virtually
unused anyway.

See for example the discussions:
https://github.com/hebasto/bitcoin/pull/41
https://github.com/bitcoin/bitcoin/pull/29123

Instead, we (fanquake, hebasto, TheCharlatan, and I) propose simply not
migrating it to CMake and letting it end with v27. Any remaining use-cases
could be handled in the future by libbitcoinkernel.
2024-01-30 23:19:02 +00:00

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Shared Libraries
================
## bitcoinconsensus
***This library is deprecated and will be removed in v28***
The purpose of this library is to make the verification functionality that is critical to Bitcoin's consensus available to other applications, e.g. to language bindings.
### API
The interface is defined in the C header `bitcoinconsensus.h` located in `src/script/bitcoinconsensus.h`.
#### Version
`bitcoinconsensus_version` returns an `unsigned int` with the API version *(currently `2`)*.
#### Script Validation
`bitcoinconsensus_verify_script`, `bitcoinconsensus_verify_script_with_amount` and `bitcoinconsensus_verify_script_with_spent_outputs` return an `int` with the status of the verification. It will be `1` if the input script correctly spends the previous output `scriptPubKey`.
##### Parameters
###### bitcoinconsensus_verify_script
- `const unsigned char *scriptPubKey` - The previous output script that encumbers spending.
- `unsigned int scriptPubKeyLen` - The number of bytes for the `scriptPubKey`.
- `const unsigned char *txTo` - The transaction with the input that is spending the previous output.
- `unsigned int txToLen` - The number of bytes for the `txTo`.
- `unsigned int nIn` - The index of the input in `txTo` that spends the `scriptPubKey`.
- `unsigned int flags` - The script validation flags *(see below)*.
- `bitcoinconsensus_error* err` - Will have the error/success code for the operation *(see below)*.
###### bitcoinconsensus_verify_script_with_amount
- `const unsigned char *scriptPubKey` - The previous output script that encumbers spending.
- `unsigned int scriptPubKeyLen` - The number of bytes for the `scriptPubKey`.
- `int64_t amount` - The amount spent in the input
- `const unsigned char *txTo` - The transaction with the input that is spending the previous output.
- `unsigned int txToLen` - The number of bytes for the `txTo`.
- `unsigned int nIn` - The index of the input in `txTo` that spends the `scriptPubKey`.
- `unsigned int flags` - The script validation flags *(see below)*.
- `bitcoinconsensus_error* err` - Will have the error/success code for the operation *(see below)*.
###### bitcoinconsensus_verify_script_with_spent_outputs
- `const unsigned char *scriptPubKey` - The previous output script that encumbers spending.
- `unsigned int scriptPubKeyLen` - The number of bytes for the `scriptPubKey`.
- `int64_t amount` - The amount spent in the input
- `const unsigned char *txTo` - The transaction with the input that is spending the previous output.
- `unsigned int txToLen` - The number of bytes for the `txTo`.
- `UTXO *spentOutputs` - Previous outputs spent in the transaction. `UTXO` is a struct composed by `const unsigned char *scriptPubKey`, `unsigned int scriptPubKeySize` (the number of bytes for the `scriptPubKey`) and `unsigned int value`.
- `unsigned int spentOutputsLen` - The number of bytes for the `spentOutputs`.
- `unsigned int nIn` - The index of the input in `txTo` that spends the `scriptPubKey`.
- `unsigned int flags` - The script validation flags *(see below)*.
- `bitcoinconsensus_error* err` - Will have the error/success code for the operation *(see below)*.
##### Script Flags
- `bitcoinconsensus_SCRIPT_FLAGS_VERIFY_NONE`
- `bitcoinconsensus_SCRIPT_FLAGS_VERIFY_P2SH` - Evaluate P2SH ([BIP16](https://github.com/bitcoin/bips/blob/master/bip-0016.mediawiki)) subscripts
- `bitcoinconsensus_SCRIPT_FLAGS_VERIFY_DERSIG` - Enforce strict DER ([BIP66](https://github.com/bitcoin/bips/blob/master/bip-0066.mediawiki)) compliance
- `bitcoinconsensus_SCRIPT_FLAGS_VERIFY_NULLDUMMY` - Enforce NULLDUMMY ([BIP147](https://github.com/bitcoin/bips/blob/master/bip-0147.mediawiki))
- `bitcoinconsensus_SCRIPT_FLAGS_VERIFY_CHECKLOCKTIMEVERIFY` - Enable CHECKLOCKTIMEVERIFY ([BIP65](https://github.com/bitcoin/bips/blob/master/bip-0065.mediawiki))
- `bitcoinconsensus_SCRIPT_FLAGS_VERIFY_CHECKSEQUENCEVERIFY` - Enable CHECKSEQUENCEVERIFY ([BIP112](https://github.com/bitcoin/bips/blob/master/bip-0112.mediawiki))
- `bitcoinconsensus_SCRIPT_FLAGS_VERIFY_WITNESS` - Enable WITNESS ([BIP141](https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki))
- `bitcoinconsensus_SCRIPT_FLAGS_VERIFY_TAPROOT` - Enable TAPROOT ([BIP340](https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki), [BIP341](https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki), [BIP342](https://github.com/bitcoin/bips/blob/master/bip-0342.mediawiki))
##### Errors
- `bitcoinconsensus_ERR_OK` - No errors with input parameters *(see the return value of `bitcoinconsensus_verify_script` for the verification status)*
- `bitcoinconsensus_ERR_TX_INDEX` - An invalid index for `txTo`
- `bitcoinconsensus_ERR_TX_SIZE_MISMATCH` - `txToLen` did not match with the size of `txTo`
- `bitcoinconsensus_ERR_DESERIALIZE` - An error deserializing `txTo`
- `bitcoinconsensus_ERR_AMOUNT_REQUIRED` - Input amount is required if WITNESS is used
- `bitcoinconsensus_ERR_INVALID_FLAGS` - Script verification `flags` are invalid (i.e. not part of the libconsensus interface)
- `bitcoinconsensus_ERR_SPENT_OUTPUTS_REQUIRED` - Spent outputs are required if TAPROOT is used
- `bitcoinconsensus_ERR_SPENT_OUTPUTS_MISMATCH` - Spent outputs size doesn't match tx inputs size
### Example Implementations
- [NBitcoin](https://github.com/MetacoSA/NBitcoin/blob/5e1055cd7c4186dee4227c344af8892aea54faec/NBitcoin/Script.cs#L979-#L1031) (.NET Bindings)
- [node-libbitcoinconsensus](https://github.com/bitpay/node-libbitcoinconsensus) (Node.js Bindings)
- [java-libbitcoinconsensus](https://github.com/dexX7/java-libbitcoinconsensus) (Java Bindings)
- [bitcoinconsensus-php](https://github.com/Bit-Wasp/bitcoinconsensus-php) (PHP Bindings)
- [rust-bitcoinconsensus](https://github.com/rust-bitcoin/rust-bitcoinconsensus) (Rust Bindings)