Start on the C api

Author: jneem

flake.nix

@@ -482,6 +482,7 @@
         inputsFrom = [ (mkCraneArtifacts { inherit rust; profile = "dev"; }).cargoArtifactsDeps ];
 
         buildInputs = [
+          pkgs.cargo-c
           pkgs.cargo-flamegraph
           pkgs.cargo-insta
           pkgs.cargo-nextest

nickel/Cargo.toml

@@ -10,6 +10,9 @@ repository.workspace = true
 homepage.workspace = true
 readme.workspace = true
 
+[features]
+capi = []
+
 [dependencies]
 codespan-reporting.workspace = true
 indexmap.workspace = true

nickel/capi-tests/run_tests.c

@@ -0,0 +1,40 @@
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "nickel_lang.h"
+
+const char* EXAMPLE = " \
+  { \
+    foo = 1, \
+  } \
+";
+
+int main() {
+  Context *ctx = nickel_context_new();
+  Expr *expr = nickel_expr_alloc();
+  Error *error = NULL;
+  nickel_context_eval_deep(ctx, EXAMPLE, expr, &error);
+
+  printf("%p %p\n", expr, error);
+
+  printf("is record: %d\n", nickel_expr_is_record(expr));
+  Record const *rec = nickel_expr_as_record(expr);
+  printf("record len: %ld\n", nickel_record_len(rec));
+
+  char const* key;
+  uintptr_t len;
+  Expr *val = nickel_expr_alloc();
+  nickel_record_key_value_by_index(rec, 0, &key, &len, val);
+
+  char *key_str = malloc(len + 1);
+  memcpy(key_str, key, len);
+  key_str[len] = '\0';
+
+  printf("key %s, value number: %d\n", key_str, nickel_expr_is_number(val));
+
+  nickel_expr_free(val);
+  nickel_expr_free(expr);
+  nickel_context_free(ctx);
+}

nickel/cbindgen.toml

@@ -0,0 +1,14 @@
+header = "// SPDX-License-Identifier: MIT"
+sys_includes = ["stdint.h"]
+no_includes = true
+include_guard = "NICKEL_LANG_H"
+tab_width = 4
+style = "Type"
+language = "C"
+cpp_compat = true
+
+[export]
+
+[const]
+allow_static_const = false
+allow_constexpr = false