An attempt to estimate the gas cost for various lengths of data in the event dictionary entry has been done using the CEP-78 contract built from this commit.
The baseline is an event with just one byte of data indicating the event type (aka CEP-78 event type modality).
| Event Data / Length | Cost for first token minted | Δ gas |
|---|---|---|
| u8 / 6 bytes | 1.817.618.450 motes | - |
| (u8,u8) / 9 bytes | 1.820.206.210 motes | 2.587.760 motes |
| (u8,string-len:6) / 18 bytes | 1.826.317.300 motes | 8.698.850 motes |
| (u8,string-len:100) / 112 bytes | 1.887.685.030 motes | 70.066.580 motes |
| (u8,string-len:50,string-len:50) / 117 bytes | 1.891.817.740 motes | 74.199.290 motes |
| (u8,string-len:100,string-len:100) / 217 bytes | 1.956.753.980 motes | 139.135.530 motes |
Length includes the total number of bytes required to encode the data in a CLValue.
Looking at the gas costs defined at chainspec.toml file, each byte of storage costs 630.000 motes. In the table above the cost increment is not equal to Δbytes*630.000 but it's close.
Events are emitted as a new entry in the dictionary stored under the contract named key events.
The data contained is a CLValue with type Option<Vec<u8>>. The Vec<u8> contains a sequence of
values that identifies the dictionary item as an event and describes it.
Data parts:
- Event tag: string
event: 9 bytes - Event type: string with event name: 8-16 bytes
- Event body:
| Event | Contents | Length |
|---|---|---|
| Mint | token_id (U64) + recipient (Key) | 41 bytes |
| Transfer | token_id (U64) + recipient (Key) + sender (Key) | 74 bytes |
| Burn | token_id (U64) | 8 bytes |
| Approve | token_id (U64) + operator (Key) | 41 bytes |
| Approve_all | owner (Key) + operator (Key) + approve_all (Bool) | 67 bytes |
| Set_metadata | token_id (U64) | 8 bytes |
The total length of the event for each type is then:
| Event | Length |
|---|---|
| Mint | 58 bytes |
| Transfer | 95 bytes |
| Burn | 25 bytes |
| Approve | 61 bytes |
| Approve_all | 91 bytes |
| Set_metadata | 33 bytes |
Looking at the gas estimation table, the cost increment for the additional information included in the event might range between 0.020 CSPR and 0.070 CSPR.