pink: Example for larger HTTP response

[kvinwang]

Note

Don't merge. This PR shows an example of how to handle a bigger HTTP response.

In PR #1280, we have implemented support for batch HTTP requests and increased the HTTP response limit to 2MB. The following example is based on that PR.

Things not ready yet

• At present, ink uses a static buffer with a hardcoded size of 16KB to exchange data across the boundary of the wasm virtual machine. The downstream contract does not have the ability to alter this configuration. Although a customizable solution has been proposed upstream, it has yet to be implemented. While we await their completion, we can implement a temporary solution by patching ink to expand the size of this static buffer.

• cargo-contract is currently rigid in that it hardcodes the maximum available memory for the output WASM as 1MB. To overcome this, we've submitted a PR upstream to allow for runtime configuration. Until that PR is merged, we can use our fork of cargo-contract for compilation to bypass this limitation.

Steps to build this example

• Install the patched cargo-contract

git clone https://github.com/kvinwang/cargo-contract
cd cargo-contract
git checkout max-memory
cargo install --path crates/cargo-contract

• Clone and checkout this PR

git clone https://github.com/Phala-Network/phala-blockchain
cd phala-blockchain/e2e/contracts/check_system
git checkout big-http
cargo contract build --max-memory-pages 32