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| -rw-r--r-- | include/RNT_C_API.h | 378 |
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diff --git a/include/RNT_C_API.h b/include/RNT_C_API.h new file mode 100644 index 0000000..ddf6a97 --- /dev/null +++ b/include/RNT_C_API.h @@ -0,0 +1,378 @@ +#pragma once + +/** + * @file RNT_C_API.h + * @brief C-callable surface over the RNT manager pipeline for OCaml ctypes. + * + * All types are opaque void pointers on the C side; the implementation casts + * them to the appropriate C++ types internally. Callers must never dereference + * handle or cursor pointers directly. + * + * ## Memory contract + * - Strings returned via out-parameters (char**) are heap-allocated by the + * API and must be released with rnt_free_string(). + * - Payloads returned via (uint8_t**, size_t*) are heap-allocated and must + * be released with rnt_free_bytes(). + * - Handles and cursors are owned by the caller and must be closed before + * the program exits. + * + * ## Error convention + * - Functions returning int use 0 for success and a negative value for error. + * - Functions returning a pointer return NULL on failure. + * + * ## Thread safety + * This API is **not thread-safe**. The global runtime (g_rt) is a single + * in-process instance; all callers share the same ObjectManager and storage + * backend. The expected usage model is a single OCaml thread (or domain) + * driving the API at a time. If concurrent access is needed in the future, + * a per-object or per-relation mutex strategy should be introduced. + * + * @todo Implement AUTH_CLAIM::READ/WRITE enforcement in rnt_open_handle once + * PermissionsManager::Access is wired to a real policy engine. Currently + * all handles open with full access regardless of the claims parameter. + */ + +#include <stddef.h> +#include <stdint.h> + +#ifdef __cplusplus +extern "C" { +#endif + +/** Opaque handle to a registry object opened through HandlerManager. */ +typedef void* rnt_handle_t; + +/** Opaque cursor over a relation, driven by the VM or used directly. */ +typedef void* rnt_cursor_t; + +/* ------------------------------------------------------------------ */ +/* Runtime lifecycle */ +/* ------------------------------------------------------------------ */ + +/** + * @brief Initialises the RNT runtime with the selected storage backend. + * + * Must be called before any other API function. Once the runtime is + * successfully initialised, subsequent calls are no-ops and return 0. + * If initialisation fails (returns negative), the call may be retried + * with corrected parameters — the runtime is left in a clean state. + * + * @param driver Storage driver to use: "sqlite" or "memory". + * "sqlite" persists data to @p storage_path. + * "memory" keeps all data in process memory (ignores + * @p storage_path); intended for tests. + * @param storage_path File path for the SQLite database, or ":memory:" for + * an ephemeral SQLite store. Ignored when driver is + * "memory". + * @return 0 on success, negative on error. + */ +int rnt_init(const char* driver, const char* storage_path); + +/* ------------------------------------------------------------------ */ +/* Authentication */ +/* ------------------------------------------------------------------ */ + +/** + * @brief Runs PermissionsManager::Firewall for a connection. + * + * @param auth_method "plain_text" or "certificate". + * @param claims_out Set to a heap-allocated, newline-separated claim string. + * Release with rnt_free_string(). NULL on error. + * @return 0 on success, negative when authentication is rejected. + */ +int rnt_firewall(const char* auth_method, char** claims_out); + +/* ------------------------------------------------------------------ */ +/* Handle lifecycle */ +/* ------------------------------------------------------------------ */ + +/** + * @brief Opens a handle to the object at the given slash-separated path. + * + * Runs the full HandlerManager::Open pipeline: + * ObjectManager::Find → PermissionsManager::Access → + * IdentityManager::CanOpen → LifecycleManager::Contention → + * LifecycleManager::Monitor. + * + * @param path Slash-separated logical path, e.g. "/system/branches/main". + * @param claims Claim string returned by rnt_firewall (may be NULL). + * @return Handle pointer, or NULL when the path is not found or access is denied. + */ +rnt_handle_t rnt_open_handle(const char* path, const char* claims); + +/** + * @brief Closes a handle, running HandlerManager::Close and Unmonitor. + * @return 0 on success, negative on error. + */ +int rnt_close_handle(rnt_handle_t handle); + +/** + * @brief Reads the raw payload bytes stored in a BRANCH object. + * + * Only valid for handles opened on BRANCH objects. The caller uses the bytes + * to reconstruct the in-memory multigroup (e.g. via Sakura's deserializer). + * + * @param handle Handle to a BRANCH object. + * @param payload_out Set to a heap-allocated copy of the payload bytes. + * Release with rnt_free_bytes(). + * @param len_out Set to the number of bytes in payload_out. + * @return 0 on success, negative when the handle is not a BRANCH. + */ +int rnt_branch_payload(rnt_handle_t handle, + uint8_t** payload_out, + size_t* len_out); + +/** + * @brief Writes new payload bytes into the BRANCH object referenced by handle. + * + * Updates the in-memory branch object. Callers are responsible for persisting + * the multigroup state to the storage backend separately via tuple link + * operations. + * + * Write exclusion is structural: BRANCH objects carry @c exclusive=true in + * their object_type, so LifecycleManager::Contention prevents a second handle + * from being opened while a writer holds the branch. AUTH_CLAIM::WRITE is not + * checked at the C API boundary. + * + * @param handle Open BRANCH handle. + * @param payload New serialized multigroup bytes. + * @param len Number of bytes in payload. + * @return 0 on success, negative on error. + */ +int rnt_branch_set_payload(rnt_handle_t handle, + const uint8_t* payload, + size_t len); + +/* ------------------------------------------------------------------ */ +/* Object registration */ +/* ------------------------------------------------------------------ */ + +/** + * @brief Registers a RELATION object at the given path. + * + * Idempotent: if an object already exists at the path, the call succeeds + * without re-registering. + * + * @param path Slash-separated path, e.g. "/system/branches/main/relations/foo". + * @return 0 on success, negative on error. + */ +int rnt_register_relation(const char* path); + +/** + * @brief Registers a BRANCH object at the given path with an initial payload. + * + * If a BRANCH already exists at this path, returns 0 without modifying it. + * + * @param path Slash-separated path, e.g. "/system/branches/main". + * @param payload Initial serialized multigroup bytes (may be NULL for empty). + * @param payload_len Byte count of payload. + * @return 0 on success, negative on error. + */ +int rnt_register_branch(const char* path, + const uint8_t* payload, + size_t payload_len); + +/* ------------------------------------------------------------------ */ +/* Tuple storage */ +/* ------------------------------------------------------------------ */ + +/** + * @brief Stores a tuple and links it to the relation at the given path. + * + * Tuples are encoded as a flat key=value string, one attribute per line: + * "name=Blathers\nprofession=Museum Curator\n" + * Attributes are sorted by name before hashing to ensure content-addressing + * is order-independent. + * + * @param relation_path Slash-separated relation path. + * @param kv_attrs Newline-delimited "key=value" attribute string. + * @param hash_out Set to the 64-character hex SHA-256 hash of the tuple. + * Release with rnt_free_string(). NULL on error. + * @return 0 on success, negative on error. + */ +int rnt_link_tuple(const char* relation_path, + const char* kv_attrs, + char** hash_out); + +/** + * @brief Removes a tuple from the relation's Merkle tree and tuple store. + * + * Calls Merkle::Remove on the relation's current root and updates + * ObjectManager::Relation::merkle_root atomically. The tuple bytes remain in + * the KV store (they may be referenced by older snapshots); only the + * membership in the current tree is removed. + * + * @param relation_path Slash-separated relation path. + * @param tuple_hash 64-character hex SHA-256 of the tuple to remove. + * @return 0 on success, negative when the relation is not found. + */ +int rnt_unlink_tuple(const char* relation_path, const char* tuple_hash); + +/** + * @brief Resets a relation's Merkle root to the empty-tree state. + * + * Sets ObjectManager::Relation::merkle_root to the empty string. Existing + * tuple bytes remain in the KV store. After this call the relation contains + * no tuples from the perspective of cursor iteration. + * + * @param relation_path Slash-separated relation path. + * @return 0 on success, negative when the relation is not found. + */ +int rnt_clear_relation(const char* relation_path); + +/** + * @brief Returns the current Merkle root hash for a relation. + * + * OCaml calls this after rnt_link_tuple or rnt_unlink_tuple to read the + * updated root back and store it in the in-memory multigroup (tree_pointer). + * An empty string is returned for a relation that contains no tuples. + * + * @param relation_path Slash-separated relation path. + * @param root_hash_out Set to the 64-character hex root hash, or to an empty + * heap-allocated string for an empty relation. + * Release with rnt_free_string(). + * @return 0 on success, negative when the relation is not found. + */ +int rnt_relation_root(const char* relation_path, char** root_hash_out); + +/** + * @brief Writes a Merkle root hash into a relation's ObjectManager entry. + * + * Called by Sakura's open_branch during multigroup reconstruction: after + * deserializing the branch payload, OCaml calls this function once per + * relation to restore the persisted Merkle root into the in-memory + * ObjectManager so that subsequent cursors see the correct tuple set. + * + * @param relation_path Slash-separated relation path. + * @param root_hash 64-character hex Merkle root, or empty string to mark + * the relation as empty. + * @return 0 on success, negative when the relation is not found. + */ +int rnt_set_relation_root(const char* relation_path, const char* root_hash); + +/* ------------------------------------------------------------------ */ +/* Cursor and VM */ +/* ------------------------------------------------------------------ */ + +/** + * @brief Opens a cursor on the relation referenced by handle. + * + * The returned cursor is positioned before the first tuple. Advance it with + * rnt_cursor_next(). The cursor must be closed with rnt_cursor_close() before + * closing the handle. + * + * @param handle Open RELATION handle. + * @return Cursor pointer, or NULL on error. + */ +rnt_cursor_t rnt_cursor_open(rnt_handle_t handle); + +/** + * @brief Advances the cursor and returns the next tuple as a kv string. + * + * The tuple is encoded as a newline-delimited "key=value" string matching the + * format accepted by rnt_link_tuple: + * "name=Blathers\nprofession=Museum Curator\n" + * + * @param cursor Open cursor. + * @param tuple_out Set to a heap-allocated kv string, or NULL when exhausted. + * Release with rnt_free_string() when non-NULL. + * @return 1 when a tuple was returned, 0 when exhausted, negative on error. + */ +int rnt_cursor_next(rnt_cursor_t cursor, char** tuple_out); + +/** + * @brief Closes a cursor and releases its resources. + * @return 0 on success, negative on error. + */ +int rnt_cursor_close(rnt_cursor_t cursor); + +/* ------------------------------------------------------------------ */ +/* VM plan builder */ +/* ------------------------------------------------------------------ */ + +/** Opaque plan node tree, built incrementally via rnt_plan_* calls. */ +typedef void* rnt_plan_t; + +/** + * @brief Creates a SCAN plan node that reads all tuples from a stored relation. + * + * Opens a RELATION handle and cursor internally. Both are transferred to the + * plan and released when the resulting VM cursor is closed. + * + * @param relation_path Absolute slash-separated path to the relation, e.g. + * "/system/branches/main/relations/public:users". + * @return Plan node, or NULL when the relation does not exist or cannot be opened. + */ +rnt_plan_t rnt_plan_scan(const char* relation_path); + +/** + * @brief Creates a nested-loop JOIN plan node. + * + * Takes ownership of both @p left and @p right. On success the caller must not + * free either child; they are released when the returned plan is freed or + * executed. On failure (NULL return) both children are freed. + * + * @return Plan node, or NULL on error. + */ +rnt_plan_t rnt_plan_join(rnt_plan_t left, rnt_plan_t right); + +/** + * @brief Creates a TAKE plan node that limits output to at most @p limit tuples. + * + * Takes ownership of @p source. On failure @p source is freed. + * + * @return Plan node, or NULL on error. + */ +rnt_plan_t rnt_plan_take(rnt_plan_t source, size_t limit); + +/** + * @brief Releases a plan that was built but not yet executed. + * + * Closes any open cursors and handles owned by the plan tree, then frees all + * nodes. Safe to call with NULL. Do NOT call after rnt_vm_execute_plan — + * that function takes ownership. + */ +void rnt_plan_free(rnt_plan_t plan); + +/** + * @brief Executes a plan tree and returns a streaming VM cursor. + * + * Takes ownership of @p plan; the caller must not call rnt_plan_free after this. + * The returned cursor is advanced with rnt_vm_cursor_next() and must be closed + * with rnt_vm_cursor_close(), which also releases all plan resources. + * + * @return VM cursor, or NULL when the plan is NULL. + */ +rnt_cursor_t rnt_vm_execute_plan(rnt_plan_t plan); + +/** + * @brief Advances a VM cursor and returns the next merged tuple as a kv string. + * + * Same encoding and return-value semantics as rnt_cursor_next. + * + * @param vm_cursor Cursor returned by rnt_vm_execute_plan. + * @param tuple_out Set to a heap-allocated kv string, or NULL when exhausted. + * Release with rnt_free_string() when non-NULL. + * @return 1 when a tuple was returned, 0 when exhausted, negative on error. + */ +int rnt_vm_cursor_next(rnt_cursor_t vm_cursor, char** tuple_out); + +/** + * @brief Closes a VM cursor, releases all plan nodes, cursors, and handles. + * @return 0 on success, negative on error. + */ +int rnt_vm_cursor_close(rnt_cursor_t vm_cursor); + +/* ------------------------------------------------------------------ */ +/* Memory management */ +/* ------------------------------------------------------------------ */ + +/** @brief Releases a string allocated by the API. Safe to call with NULL. */ +void rnt_free_string(char* s); + +/** @brief Releases a byte buffer allocated by the API. Safe to call with NULL. */ +void rnt_free_bytes(uint8_t* p); + +#ifdef __cplusplus +} +#endif |