C API: move to src/lib*/c/

src/libexpr/c/nix_api_expr.h

@@ -0,0 +1,213 @@
+#ifndef NIX_API_EXPR_H
+#define NIX_API_EXPR_H
+/** @defgroup libexpr libexpr
+ * @brief Bindings to the Nix evaluator
+ *
+ * Example (without error handling):
+ * @code{.c}
+ * int main() {
+ *    nix_libexpr_init(NULL);
+ *
+ *    Store* store = nix_store_open(NULL, "dummy", NULL);
+ *    State* state = nix_state_create(NULL, NULL, store); // empty nix path
+ *    Value *value = nix_alloc_value(NULL, state);
+ *
+ *    nix_expr_eval_from_string(NULL, state, "builtins.nixVersion", ".", value);
+ *    nix_value_force(NULL, state, value);
+ *    printf("nix version: %s\n", nix_get_string(NULL, value));
+ *
+ *    nix_gc_decref(NULL, value);
+ *    nix_state_free(state);
+ *    nix_store_unref(store);
+ *    return 0;
+ *    }
+ * @endcode
+ * @{
+ */
+/** @file
+ * @brief Main entry for the libexpr C bindings
+ */
+
+#include "nix_api_store.h"
+#include "nix_api_util.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+// cffi start
+
+// Type definitions
+/**
+ * @brief Represents a nix evaluator state.
+ *
+ * Multiple can be created for multi-threaded
+ * operation.
+ * @struct State
+ */
+typedef struct State State; // nix::EvalState
+/**
+ * @brief Represents a nix value.
+ *
+ * Owned by the GC.
+ * @struct Value
+ * @see value_manip
+ */
+typedef void Value; // nix::Value
+
+// Function prototypes
+/**
+ * @brief Initializes the Nix expression evaluator.
+ *
+ * This function should be called before creating a State.
+ * This function can be called multiple times.
+ *
+ * @param[out] context Optional, stores error information
+ * @return NIX_OK if the initialization was successful, an error code otherwise.
+ */
+nix_err nix_libexpr_init(nix_c_context *context);
+
+/**
+ * @brief Parses and evaluates a Nix expression from a string.
+ *
+ * @param[out] context Optional, stores error information
+ * @param[in] state The state of the evaluation.
+ * @param[in] expr The Nix expression to parse.
+ * @param[in] path The file path to associate with the expression.
+ * @param[out] value The result of the evaluation. You should allocate this
+ * yourself.
+ * @return NIX_OK if the evaluation was successful, an error code otherwise.
+ */
+nix_err nix_expr_eval_from_string(nix_c_context *context, State *state,
+                                  const char *expr, const char *path,
+                                  Value *value);
+
+/**
+ * @brief Calls a Nix function with an argument.
+ *
+ * @param[out] context Optional, stores error information
+ * @param[in] state The state of the evaluation.
+ * @param[in] fn The Nix function to call.
+ * @param[in] arg The argument to pass to the function.
+ * @param[out] value The result of the function call.
+ * @return NIX_OK if the function call was successful, an error code otherwise.
+ */
+nix_err nix_value_call(nix_c_context *context, State *state, Value *fn,
+                       Value *arg, Value *value);
+
+/**
+ * @brief Forces the evaluation of a Nix value.
+ *
+ * The Nix interpreter is lazy, and not-yet-evaluated Values can be
+ * of type NIX_TYPE_THUNK instead of their actual value.
+ *
+ * This function converts these Values into their final type.
+ *
+ * @note You don't need this function for basic API usage, since all functions
+ * that return a value call it for you. The only place you will see a
+ * NIX_TYPE_THUNK is in the primop callback.
+ *
+ * @param[out] context Optional, stores error information
+ * @param[in] state The state of the evaluation.
+ * @param[in,out] value The Nix value to force.
+ * @post values is not of type NIX_TYPE_THUNK
+ * @return NIX_OK if the force operation was successful, an error code
+ * otherwise.
+ */
+nix_err nix_value_force(nix_c_context *context, State *state, Value *value);
+
+/**
+ * @brief Forces the deep evaluation of a Nix value.
+ *
+ * Recursively calls nix_value_force
+ *
+ * @see nix_value_force
+ * @warning Calling this function on a recursive data structure will cause a
+ * stack overflow.
+ * @param[out] context Optional, stores error information
+ * @param[in] state The state of the evaluation.
+ * @param[in,out] value The Nix value to force.
+ * @return NIX_OK if the deep force operation was successful, an error code
+ * otherwise.
+ */
+nix_err nix_value_force_deep(nix_c_context *context, State *state,
+                             Value *value);
+
+/**
+ * @brief Creates a new Nix state.
+ *
+ * @param[out] context Optional, stores error information
+ * @param[in] searchPath The NIX_PATH.
+ * @param[in] store The Nix store to use.
+ * @return A new Nix state or NULL on failure.
+ */
+State *nix_state_create(nix_c_context *context, const char **searchPath,
+                        Store *store);
+
+/**
+ * @brief Frees a Nix state.
+ *
+ * Does not fail.
+ *
+ * @param[in] state The state to free.
+ */
+void nix_state_free(State *state);
+
+/** @addtogroup GC
+ * @brief Reference counting and garbage collector operations
+ *
+ * Nix's evaluator uses a garbage collector. To ease C interop, we implement
+ * a reference counting scheme, where objects will be deallocated
+ * when there are no references from the Nix side, and the reference count kept
+ * by the C API reaches `0`.
+ *
+ * Functions returning a garbage-collected object will automatically increase
+ * the refcount for you. You should make sure to call `nix_gc_decref` when
+ * you're done.
+ * @{
+ */
+/**
+ * @brief Increase the GC refcount.
+ *
+ * The nix C api keeps alive objects by refcounting.
+ * When you're done with a refcounted pointer, call nix_gc_decref.
+ *
+ * @param[out] context Optional, stores error information
+ * @param[in] object The object to keep alive
+ */
+nix_err nix_gc_incref(nix_c_context *context, const void *object);
+/**
+ * @brief Decrease the GC refcount
+ *
+ * @param[out] context Optional, stores error information
+ * @param[in] object The object to stop referencing
+ */
+nix_err nix_gc_decref(nix_c_context *context, const void *object);
+
+/**
+ * @brief Trigger the garbage collector manually
+ *
+ * You should not need to do this, but it can be useful for debugging.
+ */
+void nix_gc_now();
+
+/**
+ * @brief Register a callback that gets called when the object is garbage
+ * collected.
+ * @note objects can only have a single finalizer. This function overwrites
+ * silently.
+ * @param[in] obj the object to watch
+ * @param[in] cd the data to pass to the finalizer
+ * @param[in] finalizer the callback function, called with obj and cd
+ */
+void nix_gc_register_finalizer(void *obj, void *cd,
+                               void (*finalizer)(void *obj, void *cd));
+
+/** @} */
+// cffi end
+#ifdef __cplusplus
+}
+#endif
+
+/** @} */
+
+#endif // NIX_API_EXPR_H