Programs

Writing app programs with Pico

Pico entrypoint

The program is executed and proved with the zkVM platform. Pico links the programs by the main function annotated with the entrypoint macro_rules. The program needs to be declared with no_main.

// declare no_main
#![no_main]

// point out the main function in your program.
pico_sdk::entrypoint!(main);

pub fn main() {
    //todo: write your program logic here
}

Raw system calls are available by using pico_sdk::riscv_ecalls::* but it is recommended to use the integrated patch libraries to avoid disrupting the standard development workflow. The program can then be compiled to RiscV without creating conditional compilation-related hoops aside from the entry point (unless your system assumes a word size of 64 bits, which is untrue in the zkVM). A few light wrappers for elliptic curve types can also be found in the pico-patch-libs crate.

Be very careful with using heap memory. The currently implemented allocator does not free any memory, so cloning a medium-sized Vec a few too many times will cause your program to go OOM. You must write your own allocator if a more managed memory solution is required.

Inputs and outputs

pico_sdk::io::read_as Read a serialized input data type into the program and deserialize it into specific types, such as u32, u64, and bytes. Pico prove CLI provides two ways to pass the inputs: hex string and file path. When your specific input is a file path , the file content will be read as bytes in the program.

cargo pico prove --input "" # hex or file path

pico_sdk::io::commit Commit serializable data to the public stream. The public inputs will be compressed using a SHA256 hash and exported to the on-chain.

pico_sdk::io:commit_bytes Write the public values in a byte buffer.

Setup programs

1. Create an instant program

cargo pico new --template basic basic-example

The project only contains a program module. You can test and debug your RISC-V program quickly using the basic template.

1. Create a program with EVM

cargo pico new --template evm evm-example

The created project with the evm template will contain an extra Contracts folder for app and verification contracts .

• Proving with the evm option referring to this page can generate the proof for on-chain EVM.

• Verification test requires to the install foundryup and forge test.

Use the pre-prepared pico EVM proof and Groth16 verifier in the repo to run contract tests.

cd contract 
forge test