first bits of a dynamc lib

lib/Cargo.toml

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+[package]
+name = "taskchampion-lib"
+version = "0.1.0"
+edition = "2021"
+build = "build.rs"
+
+[lib]
+name = "taskchampion"
+crate-type = ["cdylib"]
+
+[dependencies]
+taskchampion = { path = "../taskchampion" }
+
+[build-dependencies]
+cbindgen = "0.20.0"

lib/Makefile

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+taskchampion.h: cbindgen.toml ../target/debug/libtaskchampion.so
+	cbindgen --config cbindgen.toml --crate taskchampion-lib --output $@

lib/build.rs

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+use cbindgen::*;
+
+use std::env;
+
+fn main() {
+    let crate_dir = env::var("CARGO_MANIFEST_DIR").unwrap();
+
+    Builder::new()
+        .with_crate(crate_dir)
+        .with_language(Language::C)
+        .with_config(Config {
+            cpp_compat: true,
+            ..Default::default()
+        })
+        .generate()
+        .expect("Unable to generate bindings")
+        .write_to_file("taskchampion.h");
+}

lib/src/lib.rs

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+pub mod storage;

lib/src/storage.rs

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+use taskchampion::{storage::Storage, StorageConfig};
+
+pub struct StoragePtr(Box<dyn Storage>);
+
+#[no_mangle]
+pub extern "C" fn storage_new_in_memory() -> *mut StoragePtr {
+    // TODO: this is a box containing a fat pointer
+    Box::into_raw(Box::new(StoragePtr(
+        StorageConfig::InMemory.into_storage().unwrap(),
+    )))
+}
+
+#[no_mangle]
+pub extern "C" fn storage_free(storage: *mut StoragePtr) {
+    drop(unsafe { Box::from_raw(storage) });
+}

lib/taskchampion.h

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+#include <cstdarg>
+#include <cstdint>
+#include <cstdlib>
+#include <ostream>
+#include <new>
+
+struct StoragePtr;
+
+extern "C" {
+
+StoragePtr *storage_new_in_memory();
+
+void storage_free(StoragePtr *storage);
+
+} // extern "C"