This repository contains an overflow arithmetic library component (in the library directory) that exports an implementation of overflowing-add which returns the resulting value from addition plus a boolean indicating whether an arithmetic overflow would occur.
Additionally a Spin HTTP application (in the example directory) imports the library to compute the overflowing addition of 2 values that are passed to the handler within each requests body as a json value (e.g. {"x": 42, "y": 2}). On success, the application returns a json encoded response reporting the value of addition and whether overflow occured, e.g. {"value": 44, "overflow": false}. If the returned "overflow" field is true (indicating overflow has occurred), the "value" field contains the wrapped value.
The example Spin application is composed with the overflow arithmetic library to create the application's component wasm which is then served by the spin-cli.
cargo-component
spin v2.3.0
wasm-tools
$ spin up --build -f example
In a separate window:
curl -d '{"x": 100, "y": 200}' localhost:3000/add
{"overflow":false,"value":300}
# NOTE: the value of "x" in the following example is i32::MAX
curl -d '{"x": 2147483647, "y": 1}' localhost:3000/add
{"overflow":true,"value":-2147483648}