> ## Documentation Index > Fetch the complete documentation index at: https://docs.herodotus.cloud/llms.txt > Use this file to discover all available pages before exploring further. # HDP Capabilities and API Surface > Everything available through the HDP object in Cairo modules HDP exposes four capability groups in your Cairo module: * `hdp.evm` for EVM data * `hdp.starknet` for Starknet data * `hdp.injected_state` for injected trie state * `hdp.unconstrained` helpers for unconstrained reads It also exposes `execute_eth_call` for provable EVM contract calls at a chosen historical block. ## HDP object in your module ```cairo theme={null} pub struct HDP { pub evm: EvmMemorizer, pub starknet: StarknetMemorizer, pub injected_state: InjectedStateMemorizer, pub unconstrained: UnconstrainedMemorizer, } ``` ## 1) `hdp.evm` (EVM memorizer) Reads verified EVM data for a specific `(chain_id, block_number, ...)` key. Chain constants: * `ETHEREUM_MAINNET_CHAIN_ID` * `ETHEREUM_TESTNET_CHAIN_ID` * `OPTIMISM_MAINNET_CHAIN_ID` * `OPTIMISM_TESTNET_CHAIN_ID` ### Header fields **Input key for all methods below:** `HeaderKey { chain_id, block_number }` | API | Output | What it gives you | | ----------------------------- | ----------- | ------------------------------------------ | | `header_get_parent` | `u256` | Parent block hash of the block header | | `header_get_uncle` | `u256` | Uncle/ommer hash field from the header | | `header_get_coinbase` | `u256` | Block proposer (beneficiary) address | | `header_get_state_root` | `u256` | Global EVM state root for that block | | `header_get_transaction_root` | `u256` | Transaction trie root for that block | | `header_get_receipt_root` | `u256` | Receipt trie root for that block | | `header_get_bloom` | `ByteArray` | Header bloom filter for event prefiltering | | `header_get_difficulty` | `u256` | Block difficulty field | | `header_get_number` | `u256` | Block number from the header | | `header_get_gas_limit` | `u256` | Block gas limit | | `header_get_gas_used` | `u256` | Total gas used in that block | | `header_get_timestamp` | `u256` | Block timestamp | | `header_get_mix_hash` | `u256` | Header mix hash field | | `header_get_nonce` | `u256` | Header nonce field | | `header_get_base_fee_per_gas` | `u256` | EIP-1559 base fee for the block | | `header_get_blob_gas_used` | `u256` | Blob gas used (EIP-4844 field) | | `header_get_excess_blob_gas` | `u256` | Excess blob gas (EIP-4844 field) | | `header_get_requests_hash` | `u256` | Requests hash field from the header | ### Account fields **Input key for all methods below:** `AccountKey { chain_id, block_number, address }` | API | Output | What it gives you | | ------------------------ | ------ | ----------------------------------------- | | `account_get_nonce` | `u256` | Account nonce at the selected block | | `account_get_balance` | `u256` | Account ETH balance at the selected block | | `account_get_state_root` | `u256` | Account storage root | | `account_get_code_hash` | `u256` | Account bytecode hash | ### Storage | API | Input | Output | What it gives you | | ------------------ | -------------------------------------------------------------- | ------ | ------------------------------------------------------------- | | `storage_get_slot` | `StorageKey { chain_id, block_number, address, storage_slot }` | `u256` | Value of a specific storage slot for a contract at that block | ### Block transactions **Input key for all methods below:** `BlockTxKey { chain_id, block_number, transaction_index }` | API | Output | What it gives you | | --------------------------------------- | ------ | ------------------------------------- | | `block_tx_get_nonce` | `u256` | Nonce of a transaction by block/index | | `block_tx_get_gas_price` | `u256` | Legacy gas price of the transaction | | `block_tx_get_gas_limit` | `u256` | Gas limit set on the transaction | | `block_tx_get_receiver` | `u256` | Recipient address (`to`) | | `block_tx_get_value` | `u256` | Native token value transferred | | `block_tx_get_v` | `u256` | Signature `v` component | | `block_tx_get_r` | `u256` | Signature `r` component | | `block_tx_get_s` | `u256` | Signature `s` component | | `block_tx_get_chain_id` | `u256` | Transaction chain id | | `block_tx_get_max_fee_per_gas` | `u256` | EIP-1559 max fee per gas | | `block_tx_get_max_priority_fee_per_gas` | `u256` | EIP-1559 priority fee | | `block_tx_get_max_fee_per_blob_gas` | `u256` | EIP-4844 max fee per blob gas | | `block_tx_get_tx_type` | `u256` | Transaction type | | `block_tx_get_sender` | `u256` | Sender address (`from`) | | `block_tx_get_hash` | `u256` | Transaction hash | ### Block receipts **Input key for all methods below:** `BlockReceiptKey { chain_id, block_number, transaction_index }` | API | Output | What it gives you | | --------------------------------------- | ----------- | ----------------------------------------- | | `block_receipt_get_status` | `u256` | Execution status of a transaction receipt | | `block_receipt_get_cumulative_gas_used` | `u256` | Cumulative gas used at this receipt index | | `block_receipt_get_bloom` | `ByteArray` | Receipt bloom for event filtering | ### Logs **Input key for all methods below:** `LogKey { chain_id, block_number, transaction_index, log_index }` | API | Output | What it gives you | | ----------------- | ------------- | ------------------------------------------ | | `log_get_address` | `u256` | Contract address that emitted the log | | `log_get_topic0` | `u256` | First topic (usually event signature hash) | | `log_get_topic1` | `u256` | Second indexed topic | | `log_get_topic2` | `u256` | Third indexed topic | | `log_get_topic3` | `u256` | Fourth indexed topic | | `log_get_topic4` | `u256` | Fifth topic when present | | `log_get_data` | `Array` | Unindexed event data payload | ## 2) `hdp.starknet` (Starknet memorizer) Reads verified Starknet data for a specific `(chain_id, block_number, ...)` key. Chain constants: * `STARKNET_MAINNET_CHAIN_ID` * `STARKNET_TESTNET_CHAIN_ID` ### Header fields **Input key for all methods below:** `HeaderKey { chain_id, block_number }` | API | Output | What it gives you | | ------------------------------------- | --------- | ----------------------------------- | | `header_get_block_number` | `felt252` | Starknet block number | | `header_get_state_root` | `felt252` | Global Starknet state root | | `header_get_sequencer_address` | `felt252` | Sequencer address for that block | | `header_get_block_timestamp` | `felt252` | Block timestamp | | `header_get_transaction_count` | `felt252` | Number of transactions in the block | | `header_get_transaction_commitment` | `felt252` | Transaction commitment value | | `header_get_event_count` | `felt252` | Number of events in the block | | `header_get_event_commitment` | `felt252` | Event commitment value | | `header_get_parent_block_hash` | `felt252` | Parent block hash | | `header_get_state_diff_commitment` | `felt252` | State diff commitment | | `header_get_state_diff_length` | `felt252` | State diff length | | `header_get_l1_gas_price_in_wei` | `felt252` | L1 gas price (wei unit field) | | `header_get_l1_gas_price_in_fri` | `felt252` | L1 gas price (fri unit field) | | `header_get_l1_data_gas_price_in_wei` | `felt252` | L1 data gas price (wei unit field) | | `header_get_l1_data_gas_price_in_fri` | `felt252` | L1 data gas price (fri unit field) | | `header_get_receipts_commitment` | `felt252` | Receipts commitment value | | `header_get_l1_data_mode` | `felt252` | L1 data availability mode field | | `header_get_protocol_version` | `felt252` | Protocol version field | ### Storage | API | Input | Output | What it gives you | | ------------------ | -------------------------------------------------------------- | --------- | ------------------------------------------------------- | | `storage_get_slot` | `StorageKey { chain_id, block_number, address, storage_slot }` | `felt252` | Value of a specific Starknet storage slot at that block | ## 3) `hdp.injected_state` (InjectedState memorizer) Works with labeled trie-like injected state you provide for a run. | API | Input | Output | What it gives you | | -------------------------------------- | ---------------------------------------------- | ----------------- | ------------------------------------------------ | | `read_injected_state_trie_root(label)` | `label: felt252` | `Option` | Current root for the labeled injected trie | | `read_key(label, key)` | `label: felt252, key: felt252` | `Option` | Value for a key in the labeled injected trie | | `write_key(label, key, value)` | `label: felt252, key: felt252, value: felt252` | `felt252` | Writes a value and returns the updated trie root | ## 4) `hdp.unconstrained` / unconstrained helpers | API | Input | Output | What it gives you | | ------------------------------- | ------------------------------------------------ | ---------- | ------------------------------------------------------ | | `evm_account_get_bytecode(key)` | `AccountKey { chain_id, block_number, address }` | `ByteCode` | Contract bytecode for an EVM account at a chosen block | ## 5) `execute_eth_call` (provable EVM call) `execute_eth_call` lets you perform a provable EVM contract call at a chosen historical block. | Item | What it means | | ----------------------------------------------- | ----------------------------------------------------------- | | Input `HDP` | Access to HDP-backed verified chain state | | Input `TimeAndSpace { chain_id, block_number }` | Selects which chain and historical block to execute against | | Input `sender` | Caller address context for the call | | Input `target` | Contract being called | | Input `calldata` | ABI-encoded function selector + arguments | | Output `success` | Whether the call execution succeeded | | Output `return_data` | Raw return bytes from the contract | | Output `gas_used` | Gas consumed by the call execution | | Output `state` | Post-call execution state object | See the dedicated page for details and patterns: * [Provable EVM Contract Calls (`execute_eth_call`)](/data-processor/eth-call)