Lib.rs

Sequences of Instructions executed within a single transaction.

In Solana, programs execute instructions, and clients submit sequences of instructions to the network to be atomically executed as Transactions.

A Message is the compact internal encoding of a transaction, as transmitted across the network and stored in, and operated on, by the runtime. It contains a flat array of all accounts accessed by all instructions in the message, a MessageHeader that describes the layout of that account array, a recent blockhash, and a compact encoding of the message's instructions.

Clients most often deal with Instructions and Transactions, with Messages being created by Transaction constructors.

To ensure reliable network delivery, serialized messages must fit into the IPv6 MTU size, conservatively assumed to be 1280 bytes. Thus constrained, care must be taken in the amount of data consumed by instructions, and the number of accounts they require to function.

This module defines two versions of Message in their own modules: legacy and [v0]. legacy is reexported here and is the current version as of Solana 1.10.0. v0 is a future message format that encodes more account keys into a transaction than the legacy format. The VersionedMessage type is a thin wrapper around either message version.

Despite living in the solana-program crate, there is no way to access the runtime's messages from within a Solana program, and only the legacy message types continue to be exposed to Solana programs, for backwards compatibility reasons.