feat(lsm): separate handle design into read and write; atomic attribute

updates

CHANGELOG.md

@@ -12,9 +12,19 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Ability to generate keys that allow one-time unauthenticated uploads (a.k.a.
   generating upload links)
 
+## Changed
+
+* LSM
+    * Switched to a split read/write handle design
+    * Changes now need to be explicitely committed before being written to
+      persistent storage
+    * Changes to entry attributes are now atomically committed
+
 ## Fixed
 
 * Failed uploads now no longer leave behind a partial entry file
+* Size of db file is now correctly calculated when the store contains deleted
+  entries
 
 ## [0.2.1](https://git.rustybever.be/Chewing_Bever/lander/src/tag/0.2.1)
 

include/lander.h

@@ -13,7 +13,11 @@ typedef struct lander_gctx {
 } lander_gctx;
 
 typedef struct lander_ctx {
-  lsm_entry_handle *entry;
+  union {
+    lsm_write_handle *write;
+    lsm_read_handle *read;
+  } entry;
+  bool write;
 } lander_ctx;
 
 typedef enum lander_attr_type : uint8_t {

lsm/include/lsm/store.h

@@ -10,94 +10,14 @@
 #define LSM_STORE_DATA_LEVELS 3
 
 /**
- * A handle referencing an entry inside a store. Read/write operations from/to
+ * Read-only handle to an entry in the store
- * the entry go through this handle.
  */
-typedef struct lsm_entry_handle lsm_entry_handle;
+typedef struct lsm_read_handle lsm_read_handle;
 
 /**
- * Checks whether the entry has an attribute with the specified type.
+ * Writeable handle to an entry in the store
- *
- * @param entry entry to check
- * @param type type of attribute to check for
  */
-bool lsm_entry_attr_present(lsm_entry_handle *handle, uint8_t type);
+typedef struct lsm_write_handle lsm_write_handle;
-
-/**
- * Retrieve the contents of an attribute from an entry, if present
- *
- * @param out where to store pointer to attribute data
- * @param entry entry to search for
- * @param type type of attribute to return
- */
-lsm_error lsm_entry_attr_get(lsm_str **out, lsm_entry_handle *handle,
-                             uint8_t type);
-
-/**
- * Convenience wrapper around `lsm_entry_attr_get` that can be used if we know
- * beforehand the attribute value is a 64-bit number.
- *
- * @param out where to store attribute data
- * @param entry entry to search for
- * @param type type of attribute to return
- */
-lsm_error lsm_entry_attr_get_uint64_t(uint64_t *out, lsm_entry_handle *handle,
-                                      uint8_t type);
-
-/**
- * Convenience wrapper around `lsm_entry_attr_get` that can be used if we know
- * beforehand the attribute value is an 8-bit number.
- *
- * @param out where to store attribute data
- * @param entry entry to search for
- * @param type type of attribute to return
- */
-lsm_error lsm_entry_attr_get_uint8_t(uint8_t *out, lsm_entry_handle *handle,
-                                     uint8_t type);
-
-/**
- * Add a new attribute to the entry. This overwrites an existing version of this
- * attribute.
- *
- * @param entry entry to modify
- * @param type type of attribute to add
- * @param data data of attribute; ownership of pointer is taken over
- */
-lsm_error lsm_entry_attr_insert(lsm_entry_handle *handle, uint8_t type,
-                                lsm_str *data);
-
-/**
- * Convenience wrapper around `lsm_entry_attr_insert` that can be used if the
- * data to be stored is a 64-bit number.
- *
- * @param entry entry to modify
- * @param type type of attribute to add
- * @param data data of attribute
- */
-lsm_error lsm_entry_attr_insert_uint64_t(lsm_entry_handle *handle, uint8_t type,
-                                         uint64_t data);
-
-/**
- * Convenience wrapper around `lsm_entry_attr_insert` that can be used if the
- * data to be stored is an 8-bit number.
- *
- * @param entry entry to modify
- * @param type type of attribute to add
- * @param data data of attribute
- */
-lsm_error lsm_entry_attr_insert_uint8_t(lsm_entry_handle *handle, uint8_t type,
-                                        uint8_t data);
-
-/**
- * Remove an atribute from the given entry, if present.
- *
- * @param out pointer to store removed data pointer in. If NULL, data pointer
- * will be leaked.
- * @param entry entry to remove attribute from
- * @param type type of attribute to remove
- */
-lsm_error lsm_entry_attr_remove(lsm_str **out, lsm_entry_handle *handle,
-                                uint8_t type);
 
 /**
  * A store consisting of LSM entries.
@@ -145,7 +65,7 @@ void lsm_store_free(lsm_store *store);
  * @param store store to retrieve entry from
  * @param key key to search
  */
-lsm_error lsm_store_open_read(lsm_entry_handle **out, lsm_store *store,
+lsm_error lsm_store_open_read(lsm_read_handle **out, lsm_store *store,
                               const lsm_str *key);
 
 /**
@@ -157,26 +77,9 @@ lsm_error lsm_store_open_read(lsm_entry_handle **out, lsm_store *store,
  * @param store store to retrieve entry from
  * @param key key to search
  */
-lsm_error lsm_store_open_write(lsm_entry_handle **out, lsm_store *store,
+lsm_error lsm_store_open_write(lsm_write_handle **out, lsm_store *store,
                                const lsm_str *key);
 
-/**
- * Commit any changes to the persistent storage. Any changes, insertions or
- * deletions that occured without a commit are reverted when the handle is
- * closed.
- *
- * @param handle handle to the entry
- */
-lsm_error lsm_entry_commit(lsm_entry_handle *handle);
-
-/**
- * Close an open entry handle.
- *
- * @param store store the handle's entry is stored in
- * @param handle handle to close
- */
-void lsm_entry_close(lsm_entry_handle *handle);
-
 /**
  * Insert a new entry into the store, returning a write handle to the newly
  * created entry.
@@ -185,57 +88,43 @@ void lsm_entry_close(lsm_entry_handle *handle);
  * @param store store to modify
  * @param key key to add; ownership of key pointer is taken over
  */
-lsm_error lsm_store_insert(lsm_entry_handle **out, lsm_store *store,
+lsm_error lsm_store_open_new(lsm_write_handle **out, lsm_store *store,
                              lsm_str *key);
 
-/**
+bool lsm_read_attr_present(lsm_read_handle *handle, uint8_t type);
- * Mark the entry as removed.
+lsm_error lsm_read_attr_get(const lsm_str **out, const lsm_read_handle *handle,
- *
+                            uint8_t type);
- * @param handle handle to entry to remove
+lsm_error lsm_read_attr_get_uint64_t(uint64_t *out,
- */
+                                     const lsm_read_handle *handle,
-void lsm_entry_remove(lsm_entry_handle *handle);
+                                     uint8_t type);
-
+lsm_error lsm_read_attr_get_uint8_t(uint8_t *out, const lsm_read_handle *handle,
-/**
+                                    uint8_t type);
- * Append new data to the given entry, which is expected to be in the store.
+uint64_t lsm_read_data_len(const lsm_read_handle *handle);
- *
+lsm_error lsm_read_data_read(uint64_t *out, char *buf, lsm_read_handle *handle,
- * This function will append either to disk or to memory, depending on the
- * length of the entry's data.
- *
- * @param store store the entry is stored in
- * @param entry entry to append data to
- * @param data data to append
- */
-lsm_error lsm_entry_data_append(lsm_entry_handle *handle, const lsm_str *data);
-
-/**
- * Same as `lsm_entry_data_append`, except that it takes a direct char array.
- *
- * @param store store the entry is stored in
- * @param entry entry to append data to
- * @param data data to append
- * @param len length of data array
- */
-lsm_error lsm_entry_data_append_raw(lsm_entry_handle *handle, char *data,
                              uint64_t len);
+void lsm_read_close(lsm_read_handle *handle);
 
-/**
+bool lsm_write_attr_present(const lsm_write_handle *handle, uint8_t type);
- * Read a number of bytes from the entry's data field. The position from which
+lsm_error lsm_write_attr_get(const lsm_str **out,
- * data is read is dependent on previous read calls.
+                             const lsm_write_handle *handle, uint8_t type);
- *
+lsm_error lsm_write_attr_get_uint64_t(uint64_t *out,
- * @param out where to write how many bytes were read
+                                      const lsm_write_handle *handle,
- * @param buf buffer to store read data in
+                                      uint8_t type);
- * @param handle entry handle to read from
+lsm_error lsm_write_attr_get_uint8_t(uint8_t *out,
- * @param len how many bytes to read at most
+                                     const lsm_write_handle *handle,
- */
+                                     uint8_t type);
-lsm_error lsm_entry_data_read(uint64_t *out, char *buf,
+lsm_error lsm_write_attr_remove(lsm_str **out, lsm_write_handle *handle,
-                              lsm_entry_handle *handle, uint64_t len);
+                                uint8_t type);
-
+lsm_error lsm_write_attr_insert(lsm_write_handle *handle, uint8_t type,
-/**
+                                lsm_str *data);
- * Return the length of the entry's data.
+lsm_error lsm_write_attr_insert_uint64_t(lsm_write_handle *handle, uint8_t type,
- *
+                                         uint64_t data);
- * @param handle entry handle to return length for
+lsm_error lsm_write_attr_insert_uint8_t(lsm_write_handle *handle, uint8_t type,
- * @return length of the data
+                                        uint8_t data);
- */
+uint64_t lsm_write_data_len(const lsm_write_handle *handle);
-uint64_t lsm_entry_data_len(lsm_entry_handle *handle);
+lsm_error lsm_write_data_append(lsm_write_handle *handle, const lsm_str *data);
+void lsm_write_remove(lsm_write_handle *handle);
+void lsm_write_close(lsm_write_handle *handle);
+lsm_error lsm_write_commit(lsm_write_handle *handle);
 
 #endif

lsm/src/_include/lsm/store_internal.h

@@ -48,6 +48,11 @@ lsm_error lsm_entry_init(lsm_entry **ptr);
  */
 void lsm_entry_free(lsm_entry *entry);
 
+/**
+ * Allocates a new entry that's identical to the provided one.
+ */
+lsm_error lsm_entry_clone(lsm_entry **out, const lsm_entry *entry);
+
 /**
  * Deallocate an existing lsm_entry object.
  *
@@ -69,19 +74,6 @@ typedef enum lsm_entry_handle_state : uint8_t {
   lsm_entry_handle_state_removed = 1 << 2,
 } lsm_entry_handle_state;
 
-struct lsm_entry_handle {
-  lsm_entry_wrapper *wrapper;
-  lsm_store *store;
-  // Either read or append, depending on how it was opened
-  FILE *f;
-  // Current position in the file pointer
-  uint64_t pos;
-  // Required to determine in what way the database files need to be synced
-  uint64_t states;
-};
-
-lsm_error lsm_entry_handle_init(lsm_entry_handle **out);
-
 struct lsm_store {
   lsm_trie *trie;
   lsm_str *data_path;
@@ -114,47 +106,45 @@ lsm_error lsm_store_load_db(lsm_store *store);
  *
  * @param handle handle to added entry
  */
-lsm_error lsm_entry_disk_insert(lsm_entry_handle *handle);
+lsm_error lsm_entry_disk_insert(lsm_store *store, lsm_entry *entry);
 
 /**
  * Remove an entry from the database.
  *
  * @param handle handle to the removed entry
  */
-lsm_error lsm_entry_disk_remove(lsm_entry_handle *handle);
+lsm_error lsm_entry_disk_remove(lsm_store *store, lsm_entry *entry);
 
 /**
  * Update an existing entry already in the store.
  *
  * @param handle to updated entry
  */
-lsm_error lsm_entry_disk_update(lsm_entry_handle *handle);
+lsm_error lsm_entry_disk_update(lsm_store *store, lsm_entry *entry);
 
 /**
  * Return the length of the path to this entry's data file
  */
-uint64_t lsm_entry_data_path_len(const lsm_entry_handle *handle);
+uint64_t lsm_entry_data_path_len(const lsm_store *store,
+                                 const lsm_entry *entry);
 
 /**
  * Fill in the entry's data file path in the provided buffer. Use
  * `lsm_entry_data_path_len` to allocate an appropriately-sized buffer
  */
-void lsm_entry_data_path(char *buf, const lsm_entry_handle *handle);
+void lsm_entry_data_path(char *path, const lsm_store *store,
+                         const lsm_entry *entry);
 
 /**
  * Open the entry's data file for reading
  *
  * @param handle handle to the entry
  */
-lsm_error lsm_entry_data_open_read(lsm_entry_handle *handle);
+lsm_error lsm_entry_data_open_read(lsm_read_handle *handle);
 
-/**
+lsm_error lsm_entry_data_open(FILE **out, const lsm_store *store,
- * Open the entry's data file for writing. The file and all subdirectories in
+                              const lsm_entry *entry, const char *mode);
- * the data dir are created as needed.
+lsm_error lsm_entry_data_mkdirs(const lsm_store *store, const lsm_entry *entry);
- *
- * @param handle handle to the entry
- */
-lsm_error lsm_entry_data_open_write(lsm_entry_handle *handle);
 
 /**
  * Remove the entry's data file if present and close its handle. Any uncommitted
@@ -162,6 +152,130 @@ lsm_error lsm_entry_data_open_write(lsm_entry_handle *handle);
  *
  * @param handle handle to the entry
  */
-lsm_error lsm_entry_data_remove(lsm_entry_handle *handle);
+lsm_error lsm_entry_data_remove(const lsm_store *store, const lsm_entry *entry);
+
+/**
+ * Checks whether the entry has an attribute with the specified type.
+ *
+ * @param entry entry to check
+ * @param type type of attribute to check for
+ */
+bool lsm_entry_attr_present(const lsm_entry *entry, uint8_t type);
+
+/**
+ * Retrieve the contents of an attribute from an entry, if present
+ *
+ * @param out where to store pointer to attribute data
+ * @param entry entry to search for
+ * @param type type of attribute to return
+ */
+lsm_error lsm_entry_attr_get(const lsm_str **out, const lsm_entry *entry,
+                             uint8_t type);
+
+/**
+ * Convenience wrapper around `lsm_entry_attr_get` that can be used if we know
+ * beforehand the attribute value is a 64-bit number.
+ *
+ * @param out where to store attribute data
+ * @param entry entry to search for
+ * @param type type of attribute to return
+ */
+lsm_error lsm_entry_attr_get_uint64_t(uint64_t *out, const lsm_entry *entry,
+                                      uint8_t type);
+
+/**
+ * Convenience wrapper around `lsm_entry_attr_get` that can be used if we know
+ * beforehand the attribute value is an 8-bit number.
+ *
+ * @param out where to store attribute data
+ * @param entry entry to search for
+ * @param type type of attribute to return
+ */
+lsm_error lsm_entry_attr_get_uint8_t(uint8_t *out, const lsm_entry *entry,
+                                     uint8_t type);
+
+/**
+ * Add a new attribute to the entry. This overwrites an existing version of this
+ * attribute.
+ *
+ * @param entry entry to modify
+ * @param type type of attribute to add
+ * @param data data of attribute; ownership of pointer is taken over
+ */
+lsm_error lsm_entry_attr_insert(lsm_entry *entry, uint8_t type, lsm_str *data);
+
+/**
+ * Convenience wrapper around `lsm_entry_attr_insert` that can be used if the
+ * data to be stored is a 64-bit number.
+ *
+ * @param entry entry to modify
+ * @param type type of attribute to add
+ * @param data data of attribute
+ */
+lsm_error lsm_entry_attr_insert_uint64_t(lsm_entry *entry, uint8_t type,
+                                         uint64_t data);
+
+/**
+ * Convenience wrapper around `lsm_entry_attr_insert` that can be used if the
+ * data to be stored is an 8-bit number.
+ *
+ * @param entry entry to modify
+ * @param type type of attribute to add
+ * @param data data of attribute
+ */
+lsm_error lsm_entry_attr_insert_uint8_t(lsm_entry *entry, uint8_t type,
+                                        uint8_t data);
+
+/**
+ * Remove an atribute from the given entry, if present.
+ *
+ * @param out pointer to store removed data pointer in. If NULL, data pointer
+ * will be leaked.
+ * @param entry entry to remove attribute from
+ * @param type type of attribute to remove
+ */
+lsm_error lsm_entry_attr_remove(lsm_str **out, lsm_entry *entry, uint8_t type);
+
+/****************************************
+ *************** Handles ***************
+ ***************************************/
+
+struct lsm_read_handle {
+  lsm_entry_wrapper *wrapper;
+  lsm_store *store;
+
+  struct {
+    FILE *f;
+    uint64_t pos;
+  } data;
+};
+
+struct lsm_write_handle {
+  lsm_entry_wrapper *wrapper;
+  lsm_store *store;
+
+  lsm_entry *dirty;
+  bool removed;
+
+  struct {
+    FILE *f;
+    uint64_t pos;
+  } data;
+};
+
+/**
+ * Allocate a new `lsm_read_handle` object
+ */
+lsm_error lsm_read_handle_init(lsm_read_handle **out);
+
+/**
+ * Allocate a new `lsm_write_handle` object
+ */
+lsm_error lsm_write_handle_init(lsm_write_handle **out);
+
+/**
+ * Commit changes solely to the memory part of the store.
+ */
+void lsm_write_commit_mem(lsm_write_handle *handle);
 
 #endif

lsm/src/store/lsm_handle_read.c

@@ -0,0 +1,79 @@
+#include <stdlib.h>
+
+#include "lsm/store_internal.h"
+
+lsm_error lsm_read_handle_init(lsm_read_handle **out) {
+  lsm_read_handle *handle = calloc(1, sizeof(lsm_read_handle));
+
+  if (handle == NULL) {
+    return lsm_error_failed_alloc;
+  }
+
+  *out = handle;
+
+  return lsm_error_ok;
+}
+
+bool lsm_read_attr_present(lsm_read_handle *handle, uint8_t type) {
+  return lsm_entry_attr_present(handle->wrapper->entry, type);
+}
+
+lsm_error lsm_read_attr_get(const lsm_str **out, const lsm_read_handle *handle,
+                            uint8_t type) {
+  return lsm_entry_attr_get(out, handle->wrapper->entry, type);
+}
+
+lsm_error lsm_read_attr_get_uint64_t(uint64_t *out,
+                                     const lsm_read_handle *handle,
+                                     uint8_t type) {
+  return lsm_entry_attr_get_uint64_t(out, handle->wrapper->entry, type);
+}
+
+lsm_error lsm_read_attr_get_uint8_t(uint8_t *out, const lsm_read_handle *handle,
+                                    uint8_t type) {
+  return lsm_entry_attr_get_uint8_t(out, handle->wrapper->entry, type);
+}
+
+uint64_t lsm_read_data_len(const lsm_read_handle *handle) {
+  return handle->wrapper->entry->data_len;
+}
+
+lsm_error lsm_read_data_read(uint64_t *out, char *buf, lsm_read_handle *handle,
+                             uint64_t len) {
+  const lsm_entry *entry = handle->wrapper->entry;
+
+  if (entry->data_len == 0) {
+    *out = 0;
+
+    return lsm_error_ok;
+  }
+
+  // Entries don't open their file unless needed
+  if (handle->data.f == NULL) {
+    LSM_RES(lsm_entry_data_open(&handle->data.f, handle->store,
+                                handle->wrapper->entry, "rb"));
+  }
+
+  uint64_t read;
+
+  read = fread(buf, sizeof(char), len, handle->data.f);
+
+  if ((read == 0) && (ferror(handle->data.f) != 0)) {
+    return lsm_error_failed_io;
+  }
+
+  handle->data.pos += read;
+  *out = read;
+
+  return lsm_error_ok;
+}
+
+void lsm_read_close(lsm_read_handle *handle) {
+  if (handle->data.f != NULL) {
+    fclose(handle->data.f);
+    handle->data.f = NULL;
+  }
+
+  pthread_rwlock_unlock(&handle->wrapper->lock);
+  free(handle);
+}

lsm/src/store/lsm_handle_write.c

@@ -0,0 +1,183 @@
+#include <stdlib.h>
+
+#include "lsm/store_internal.h"
+
+lsm_error lsm_write_handle_init(lsm_write_handle **out) {
+  lsm_write_handle *handle = calloc(1, sizeof(lsm_write_handle));
+
+  if (handle == NULL) {
+    return lsm_error_failed_alloc;
+  }
+
+  *out = handle;
+
+  return lsm_error_ok;
+}
+
+bool lsm_write_attr_present(const lsm_write_handle *handle, uint8_t type) {
+  return lsm_entry_attr_present(handle->wrapper->entry, type);
+}
+
+lsm_error lsm_write_attr_get(const lsm_str **out,
+                             const lsm_write_handle *handle, uint8_t type) {
+  lsm_entry *entry =
+      handle->dirty == NULL ? handle->wrapper->entry : handle->dirty;
+  return lsm_entry_attr_get(out, entry, type);
+}
+
+lsm_error lsm_write_attr_get_uint64_t(uint64_t *out,
+                                      const lsm_write_handle *handle,
+                                      uint8_t type) {
+  lsm_entry *entry =
+      handle->dirty == NULL ? handle->wrapper->entry : handle->dirty;
+  return lsm_entry_attr_get_uint64_t(out, entry, type);
+}
+
+lsm_error lsm_write_attr_get_uint8_t(uint8_t *out,
+                                     const lsm_write_handle *handle,
+                                     uint8_t type) {
+  lsm_entry *entry =
+      handle->dirty == NULL ? handle->wrapper->entry : handle->dirty;
+  return lsm_entry_attr_get_uint8_t(out, entry, type);
+}
+
+lsm_error lsm_write_attr_remove(lsm_str **out, lsm_write_handle *handle,
+                                uint8_t type) {
+  if (handle->dirty == NULL) {
+    LSM_RES(lsm_entry_clone(&handle->dirty, handle->wrapper->entry));
+  }
+
+  return lsm_entry_attr_remove(out, handle->dirty, type);
+}
+
+lsm_error lsm_write_attr_insert(lsm_write_handle *handle, uint8_t type,
+                                lsm_str *data) {
+  if (handle->dirty == NULL) {
+    LSM_RES(lsm_entry_clone(&handle->dirty, handle->wrapper->entry));
+  }
+
+  return lsm_entry_attr_insert(handle->dirty, type, data);
+}
+
+lsm_error lsm_write_attr_insert_uint64_t(lsm_write_handle *handle, uint8_t type,
+                                         uint64_t data) {
+  if (handle->dirty == NULL) {
+    LSM_RES(lsm_entry_clone(&handle->dirty, handle->wrapper->entry));
+  }
+
+  return lsm_entry_attr_insert_uint64_t(handle->dirty, type, data);
+}
+
+lsm_error lsm_write_attr_insert_uint8_t(lsm_write_handle *handle, uint8_t type,
+                                        uint8_t data) {
+  if (handle->dirty == NULL) {
+    LSM_RES(lsm_entry_clone(&handle->dirty, handle->wrapper->entry));
+  }
+
+  return lsm_entry_attr_insert_uint8_t(handle->dirty, type, data);
+}
+
+uint64_t lsm_write_data_len(const lsm_write_handle *handle) {
+  lsm_entry *entry =
+      handle->dirty == NULL ? handle->wrapper->entry : handle->dirty;
+
+  return entry->data_len;
+}
+
+lsm_error lsm_write_data_append(lsm_write_handle *handle, const lsm_str *data) {
+  if (lsm_str_len(data) == 0) {
+    return lsm_error_ok;
+  }
+
+  if (handle->dirty == NULL) {
+    LSM_RES(lsm_entry_clone(&handle->dirty, handle->wrapper->entry));
+  }
+
+  lsm_entry *entry = handle->dirty;
+
+  uint64_t new_len = entry->data_len + lsm_str_len(data);
+  const char *data_s = lsm_str_ptr(data);
+
+  // Entries don't open their file unless needed
+  if (handle->data.f == NULL) {
+    // An entry with no existing data will not have a data file yet, so we set
+    // create to true then
+    LSM_RES(lsm_entry_data_mkdirs(handle->store, entry));
+    LSM_RES(lsm_entry_data_open(&handle->data.f, handle->store, entry, "ab"));
+  }
+
+  size_t written = 0;
+
+  // TODO what happens when I/O fails?
+  while (written < data->len) {
+    written += fwrite(&data_s[written], sizeof(char), data->len - written,
+                      handle->data.f);
+  }
+
+  entry->data_len = new_len;
+
+  return lsm_error_ok;
+}
+
+void lsm_write_remove(lsm_write_handle *handle) { handle->removed = true; }
+
+void lsm_write_close(lsm_write_handle *handle) {
+  if (handle->data.f != NULL) {
+    fclose(handle->data.f);
+    handle->data.f = NULL;
+  }
+
+  if (handle->dirty != NULL) {
+    // Entry was never committed to store, so any created data file should be
+    // removed
+    if (handle->wrapper->entry == NULL) {
+      lsm_entry_data_remove(handle->store, handle->dirty);
+    }
+
+    lsm_entry_free(handle->dirty);
+  }
+
+  pthread_rwlock_unlock(&handle->wrapper->lock);
+  free(handle);
+}
+
+lsm_error lsm_write_commit(lsm_write_handle *handle) {
+  if (handle->removed && (handle->wrapper->entry != NULL)) {
+    LSM_RES(lsm_entry_disk_remove(handle->store, handle->wrapper->entry));
+
+    lsm_entry_free(handle->wrapper->entry);
+    handle->wrapper->entry = NULL;
+    handle->removed = false;
+
+    return lsm_error_ok;
+  }
+
+  if (handle->dirty == NULL) {
+    return lsm_error_ok;
+  }
+
+  if (handle->wrapper->entry == NULL) {
+    LSM_RES(lsm_entry_disk_insert(handle->store, handle->dirty));
+  } else {
+    LSM_RES(lsm_entry_disk_update(handle->store, handle->dirty));
+    lsm_entry_free(handle->wrapper->entry);
+  }
+
+  handle->wrapper->entry = handle->dirty;
+  handle->dirty = NULL;
+
+  return lsm_error_ok;
+}
+
+void lsm_write_commit_mem(lsm_write_handle *handle) {
+  if (handle->dirty == NULL) {
+    return;
+  }
+
+  if (handle->wrapper->entry != NULL) {
+    lsm_entry_free(handle->wrapper->entry);
+  }
+
+  handle->wrapper->entry = handle->dirty;
+  handle->dirty = NULL;
+}

lsm/src/store/lsm_store.c

@@ -28,7 +28,7 @@ uint64_t lsm_store_size(const lsm_store *store) {
   return lsm_trie_size(store->trie);
 }
 
-lsm_error lsm_store_open_read(lsm_entry_handle **out, lsm_store *store,
+lsm_error lsm_store_open_read(lsm_read_handle **out, lsm_store *store,
                               const lsm_str *key) {
   lsm_entry_wrapper *wrapper;
 
@@ -47,8 +47,8 @@ lsm_error lsm_store_open_read(lsm_entry_handle **out, lsm_store *store,
     return lsm_error_not_found;
   }
 
-  lsm_entry_handle *handle;
+  lsm_read_handle *handle;
-  LSM_RES2(lsm_entry_handle_init(&handle),
+  LSM_RES2(lsm_read_handle_init(&handle),
            pthread_rwlock_unlock(&wrapper->lock));
 
   handle->wrapper = wrapper;
@@ -58,7 +58,7 @@ lsm_error lsm_store_open_read(lsm_entry_handle **out, lsm_store *store,
   return lsm_error_ok;
 }
 
-lsm_error lsm_store_open_write(lsm_entry_handle **out, lsm_store *store,
+lsm_error lsm_store_open_write(lsm_write_handle **out, lsm_store *store,
                                const lsm_str *key) {
   lsm_entry_wrapper *wrapper;
   LSM_RES(lsm_trie_search((void **)&wrapper, store->trie, key));
@@ -77,8 +77,8 @@ lsm_error lsm_store_open_write(lsm_entry_handle **out, lsm_store *store,
     return lsm_error_not_found;
   }
 
-  lsm_entry_handle *handle;
+  lsm_write_handle *handle;
-  LSM_RES2(lsm_entry_handle_init(&handle),
+  LSM_RES2(lsm_write_handle_init(&handle),
            pthread_rwlock_unlock(&wrapper->lock));
 
   handle->wrapper = wrapper;
@@ -88,7 +88,7 @@ lsm_error lsm_store_open_write(lsm_entry_handle **out, lsm_store *store,
   return lsm_error_ok;
 }
 
-lsm_error lsm_store_insert(lsm_entry_handle **out, lsm_store *store,
+lsm_error lsm_store_open_new(lsm_write_handle **out, lsm_store *store,
                              lsm_str *key) {
   // TODO what happens when two inserts to the same key happen at the same time?
   lsm_entry_wrapper *wrapper;
@@ -117,84 +117,16 @@ lsm_error lsm_store_insert(lsm_entry_handle **out, lsm_store *store,
   LSM_RES2(lsm_entry_init(&entry), pthread_rwlock_unlock(&wrapper->lock));
 
   entry->key = key;
-  wrapper->entry = entry;
 
-  lsm_entry_handle *handle;
+  lsm_write_handle *handle;
-  LSM_RES2(lsm_entry_handle_init(&handle),
+  LSM_RES2(lsm_write_handle_init(&handle),
            pthread_rwlock_unlock(&wrapper->lock));
 
-  // No need to set the handle's file, as the entry doesn't have any data yet
   handle->wrapper = wrapper;
   handle->store = store;
-
+  handle->dirty = entry;
-  // Newly inserted entries are always dirty
-  handle->states |= lsm_entry_handle_state_new;
 
   *out = handle;
 
   return lsm_error_ok;
 }
-
-void lsm_entry_remove(lsm_entry_handle *handle) {
-  handle->states |= lsm_entry_handle_state_removed;
-}
-
-lsm_error lsm_entry_data_append(lsm_entry_handle *handle, const lsm_str *data) {
-  if (lsm_str_len(data) == 0) {
-    return lsm_error_ok;
-  }
-
-  lsm_entry *entry = handle->wrapper->entry;
-
-  uint64_t new_len = entry->data_len + lsm_str_len(data);
-  const char *data_s = lsm_str_ptr(data);
-
-  // Entries don't open their file unless needed
-  if (handle->f == NULL) {
-    // An entry with no existing data will not have a data file yet, so we set
-    // create to true then
-    LSM_RES(lsm_entry_data_open_write(handle));
-  }
-
-  size_t written = 0;
-
-  // TODO what happens when I/O fails?
-  while (written < data->len) {
-    written +=
-        fwrite(&data_s[written], sizeof(char), data->len - written, handle->f);
-  }
-
-  entry->data_len = new_len;
-  handle->states |= lsm_entry_handle_state_updated;
-
-  return lsm_error_ok;
-}
-
-lsm_error lsm_entry_data_read(uint64_t *out, char *buf,
-                              lsm_entry_handle *handle, uint64_t len) {
-  const lsm_entry *entry = handle->wrapper->entry;
-
-  if (entry->data_len == 0) {
-    *out = 0;
-
-    return lsm_error_ok;
-  }
-
-  // Entries don't open their file unless needed
-  if (handle->f == NULL) {
-    LSM_RES(lsm_entry_data_open_read(handle));
-  }
-
-  uint64_t read;
-
-  read = fread(buf, sizeof(char), len, handle->f);
-
-  if ((read == 0) && (ferror(handle->f) != 0)) {
-    return lsm_error_failed_io;
-  }
-
-  handle->pos += read;
-  *out = read;
-
-  return lsm_error_ok;
-}

lsm/src/store/lsm_store_disk_read.c

@@ -130,7 +130,7 @@ static lsm_error lsm_entry_read_str(lsm_str **out, uint64_t *sum, FILE *f) {
   return lsm_str_init(out, buf);
 }
 
-static lsm_error lsm_entry_read_attrs(uint64_t *sum, lsm_entry_handle *handle,
+static lsm_error lsm_entry_read_attrs(uint64_t *sum, lsm_entry *entry,
                                       FILE *db_file) {
   uint8_t attr_count;
   LSM_RES(lsm_fread(&attr_count, sum, db_file, sizeof(uint8_t), 1));
@@ -142,11 +142,12 @@ static lsm_error lsm_entry_read_attrs(uint64_t *sum, lsm_entry_handle *handle,
   for (uint64_t i = 0; i < attr_count; i++) {
     LSM_RES(lsm_fread(&attr_type, sum, db_file, sizeof(uint8_t), 1));
     LSM_RES(lsm_entry_read_str(&val, sum, db_file));
-    LSM_RES(lsm_entry_attr_insert(handle, attr_type, val));
+    LSM_RES(lsm_entry_attr_insert(entry, attr_type, val));
   }
 
   return lsm_error_ok;
 }
+
 static lsm_error lsm_fseek(FILE *f, uint64_t pos) {
   if (fseek(f, pos, SEEK_SET) != 0) {
     return lsm_error_failed_io;
@@ -165,17 +166,17 @@ lsm_error lsm_store_insert_from_db(lsm_store *store, uint64_t pos,
   lsm_str *key;
   LSM_RES(lsm_entry_read_str(&key, NULL, store->db.f));
 
-  lsm_entry_handle *handle;
+  lsm_write_handle *handle;
-  LSM_RES(lsm_store_insert(&handle, store, key));
+  LSM_RES(lsm_store_open_new(&handle, store, key));
 
-  LSM_RES(lsm_fread(&handle->wrapper->entry->data_len, NULL, store->db.f,
+  LSM_RES(lsm_fread(&handle->dirty->data_len, NULL, store->db.f,
                     sizeof(uint64_t), 1));
-  LSM_RES(lsm_entry_read_attrs(NULL, handle, store->db.f));
+  LSM_RES(lsm_entry_read_attrs(NULL, handle->dirty, store->db.f));
 
-  handle->wrapper->entry->idx_file_offset = idx_file_offset;
+  handle->dirty->idx_file_offset = idx_file_offset;
 
-  handle->states = 0;
+  lsm_write_commit_mem(handle);
-  lsm_entry_close(handle);
+  lsm_write_close(handle);
 
   return lsm_error_ok;
 }

lsm/src/store/lsm_store_disk_write.c

@@ -74,16 +74,14 @@ lsm_error lsm_write_idx_entry(uint64_t *size, FILE *idx_file, uint64_t offset,
   return lsm_error_ok;
 }
 
-lsm_error lsm_entry_disk_insert(lsm_entry_handle *handle) {
+lsm_error lsm_entry_disk_insert(lsm_store *store, lsm_entry *entry) {
-  lsm_store *store = handle->store;
-
   pthread_mutex_lock(&store->db.lock);
 
   uint64_t db_entry_index = store->db.size;
 
   uint64_t db_entry_size;
-  lsm_error res = lsm_write_db_entry(&db_entry_size, store->db.f,
+  lsm_error res =
-                                     handle->wrapper->entry, store->db.size);
+      lsm_write_db_entry(&db_entry_size, store->db.f, entry, store->db.size);
   fflush(store->db.f);
 
   pthread_mutex_unlock(&store->db.lock);
@@ -117,7 +115,7 @@ lsm_error lsm_entry_disk_insert(lsm_entry_handle *handle) {
       store->idx.block_count = new_block_count;
       store->db.size += db_entry_size;
 
-      handle->wrapper->entry->idx_file_offset = idx_entry_index;
+      entry->idx_file_offset = idx_entry_index;
     }
   }
 
@@ -154,24 +152,21 @@ static lsm_error lsm_idx_zero_block(lsm_store *store, uint64_t pos) {
 
 // Marking an entry as removed in the idx file is simply setting the length of
 // its entry to zero
-lsm_error lsm_entry_disk_remove(lsm_entry_handle *handle) {
+lsm_error lsm_entry_disk_remove(lsm_store *store, lsm_entry *entry) {
-  const lsm_entry *entry = handle->wrapper->entry;
+  LSM_RES(lsm_idx_zero_block(store, entry->idx_file_offset + sizeof(uint64_t)));
-
+  LSM_RES(lsm_entry_data_remove(store, entry));
-  LSM_RES(lsm_idx_zero_block(handle->store,
-                             entry->idx_file_offset + sizeof(uint64_t)));
-  LSM_RES(lsm_entry_data_remove(handle));
 
   return lsm_error_ok;
 }
 
-lsm_error lsm_entry_disk_update(lsm_entry_handle *handle) {
+lsm_error lsm_entry_disk_update(lsm_store *store, lsm_entry *entry) {
   // An update is implemented by reinserting the entry at the end of the db file
-  uint64_t old_idx_index = handle->wrapper->entry->idx_file_offset;
+  uint64_t old_idx_index = entry->idx_file_offset;
 
   // TODO is there any way we can make this atomic? If the zero write to the
   // index file fails, there are two entries in the db file for the same key.
-  LSM_RES(lsm_entry_disk_insert(handle));
+  LSM_RES(lsm_entry_disk_insert(store, entry));
-  LSM_RES(lsm_idx_zero_block(handle->store, old_idx_index + sizeof(uint64_t)));
+  LSM_RES(lsm_idx_zero_block(store, old_idx_index + sizeof(uint64_t)));
 
   return lsm_error_ok;
 }

lsm/src/store/lsm_store_entry.c

@@ -24,12 +24,45 @@ lsm_error lsm_entry_init(lsm_entry **ptr) {
 
 void lsm_entry_free(lsm_entry *entry) {
   if (entry->attrs.count > 0) {
+    for (size_t i = 0; i < entry->attrs.count; i++) {
+      lsm_str_free(entry->attrs.items[i].str);
+    }
+
     free(entry->attrs.items);
   }
 
   free(entry);
 }
 
+lsm_error lsm_entry_clone(lsm_entry **out, const lsm_entry *entry) {
+  lsm_entry *new;
+  LSM_RES(lsm_entry_init(&new));
+
+  lsm_str_init_copy_n(&new->key, lsm_str_ptr(entry->key),
+                      lsm_str_len(entry->key));
+
+  for (int i = 0; i < 4; i++) {
+    new->attrs.bitmap[i] = entry->attrs.bitmap[i];
+  }
+
+  new->attrs.count = entry->attrs.count;
+  new->attrs.items = malloc(sizeof(lsm_attr) * entry->attrs.count);
+
+  for (size_t i = 0; i < entry->attrs.count; i++) {
+    new->attrs.items[i].type = entry->attrs.items[i].type;
+    lsm_str_init_copy_n(&new->attrs.items[i].str,
+                        lsm_str_ptr(entry->attrs.items[i].str),
+                        lsm_str_len(entry->attrs.items[i].str));
+  }
+
+  new->data_len = entry->data_len;
+  new->idx_file_offset = entry->idx_file_offset;
+
+  *out = new;
+
+  return lsm_error_ok;
+}
+
 lsm_error lsm_entry_wrapper_init(lsm_entry_wrapper **ptr) {
   lsm_entry_wrapper *wrap = calloc(1, sizeof(lsm_entry_wrapper));
 
@@ -46,80 +79,16 @@ lsm_error lsm_entry_wrapper_init(lsm_entry_wrapper **ptr) {
 
 void lsm_entry_wrapper_free(lsm_entry_wrapper *wrapper) { free(wrapper); }
 
-lsm_error lsm_entry_handle_init(lsm_entry_handle **out) {
+bool lsm_entry_attr_present(const lsm_entry *entry, uint8_t type) {
-  lsm_entry_handle *handle = calloc(1, sizeof(lsm_entry_handle));
+  return (entry->attrs.bitmap[type / 64] & (((uint64_t)1) << (type % 64))) != 0;
-
-  if (handle == NULL) {
-    return lsm_error_failed_alloc;
-  }
-
-  *out = handle;
-
-  return lsm_error_ok;
 }
 
-lsm_error lsm_entry_commit(lsm_entry_handle *handle) {
+lsm_error lsm_entry_attr_get(const lsm_str **out, const lsm_entry *entry,
-  uint8_t state_new = handle->states & lsm_entry_handle_state_new;
-  uint8_t state_removed = handle->states & lsm_entry_handle_state_removed;
-  uint8_t state_updated = handle->states & lsm_entry_handle_state_updated;
-
-  // Clean new entry
-  if (state_new && !state_removed) {
-    LSM_RES(lsm_entry_disk_insert(handle));
-  }
-  // Previously stored entry that needs to be removed; should be removed from db
-  // file as well
-  else if (state_removed && !state_new) {
-    LSM_RES(lsm_entry_disk_remove(handle));
-
-    lsm_entry_free(handle->wrapper->entry);
-    handle->wrapper->entry = NULL;
-  } else if (state_updated && !(state_new || state_removed)) {
-    LSM_RES(lsm_entry_disk_update(handle));
-  }
-
-  // Reset states after committing current changes
-  handle->states = 0;
-
-  return lsm_error_ok;
-}
-
-void lsm_entry_close(lsm_entry_handle *handle) {
-  if (handle->f != NULL) {
-    fclose(handle->f);
-    handle->f = NULL;
-  }
-
-  uint8_t state_new = handle->states & lsm_entry_handle_state_new;
-  /* bool state_updated = handle->states & lsm_entry_handle_state_updated; */
-
-  // New entries create a wrapper in the trie that should be removed if not
-  // committed
-  if (state_new) {
-    lsm_entry_data_remove(handle);
-
-    lsm_entry_free(handle->wrapper->entry);
-    handle->wrapper->entry = NULL;
-  }
-
-  // TODO rollback uncomitted updates
-
-  pthread_rwlock_unlock(&handle->wrapper->lock);
-  free(handle);
-}
-
-bool lsm_entry_attr_present(lsm_entry_handle *handle, uint8_t type) {
-  return (handle->wrapper->entry->attrs.bitmap[type / 64] &
-          (((uint64_t)1) << (type % 64))) != 0;
-}
-
-lsm_error lsm_entry_attr_get(lsm_str **out, lsm_entry_handle *handle,
                              uint8_t type) {
-  if (!lsm_entry_attr_present(handle, type)) {
+  if (!lsm_entry_attr_present(entry, type)) {
     return lsm_error_not_found;
   }
 
-  lsm_entry *entry = handle->wrapper->entry;
   uint64_t i = 0;
 
   while (entry->attrs.items[i].type != type) {
@@ -131,11 +100,11 @@ lsm_error lsm_entry_attr_get(lsm_str **out, lsm_entry_handle *handle,
   return lsm_error_ok;
 }
 
-lsm_error lsm_entry_attr_get_uint64_t(uint64_t *out, lsm_entry_handle *handle,
+lsm_error lsm_entry_attr_get_uint64_t(uint64_t *out, const lsm_entry *entry,
                                       uint8_t type) {
-  lsm_str *s;
+  const lsm_str *s;
 
-  LSM_RES(lsm_entry_attr_get(&s, handle, type));
+  LSM_RES(lsm_entry_attr_get(&s, entry, type));
 
   uint64_t num = 0;
 
@@ -148,25 +117,22 @@ lsm_error lsm_entry_attr_get_uint64_t(uint64_t *out, lsm_entry_handle *handle,
   return lsm_error_ok;
 }
 
-lsm_error lsm_entry_attr_get_uint8_t(uint8_t *out, lsm_entry_handle *handle,
+lsm_error lsm_entry_attr_get_uint8_t(uint8_t *out, const lsm_entry *entry,
                                      uint8_t type) {
-  lsm_str *s;
+  const lsm_str *s;
 
-  LSM_RES(lsm_entry_attr_get(&s, handle, type));
+  LSM_RES(lsm_entry_attr_get(&s, entry, type));
 
   *out = lsm_str_char(s, 0);
 
   return lsm_error_ok;
 }
 
-lsm_error lsm_entry_attr_remove(lsm_str **out, lsm_entry_handle *handle,
+lsm_error lsm_entry_attr_remove(lsm_str **out, lsm_entry *entry, uint8_t type) {
-                                uint8_t type) {
+  if (!lsm_entry_attr_present(entry, type)) {
-  if (!lsm_entry_attr_present(handle, type)) {
     return lsm_error_not_found;
   }
 
-  lsm_entry *entry = handle->wrapper->entry;
-
   if (entry->attrs.count == 1) {
     *out = entry->attrs.items[0].str;
 
@@ -204,21 +170,16 @@ lsm_error lsm_entry_attr_remove(lsm_str **out, lsm_entry_handle *handle,
   entry->attrs.count--;
   entry->attrs.bitmap[type / 64] &= ~(((uint64_t)1) << (type % 64));
 
-  handle->states |= lsm_entry_handle_state_updated;
-
   return lsm_error_ok;
 }
 
-lsm_error lsm_entry_attr_insert(lsm_entry_handle *handle, uint8_t type,
+lsm_error lsm_entry_attr_insert(lsm_entry *entry, uint8_t type, lsm_str *data) {
-                                lsm_str *data) {
   // Remove a previous version of the attribute
   lsm_str *out;
-  if (lsm_entry_attr_remove(&out, handle, type) == lsm_error_ok) {
+  if (lsm_entry_attr_remove(&out, entry, type) == lsm_error_ok) {
     lsm_str_free(out);
   }
 
-  lsm_entry *entry = handle->wrapper->entry;
-
   lsm_attr *new_attrs =
       realloc(entry->attrs.items, (entry->attrs.count + 1) * sizeof(lsm_attr));
 
@@ -233,36 +194,31 @@ lsm_error lsm_entry_attr_insert(lsm_entry_handle *handle, uint8_t type,
   entry->attrs.count++;
   entry->attrs.bitmap[type / 64] |= ((uint64_t)1) << (type % 64);
 
-  handle->states |= lsm_entry_handle_state_updated;
-
   return lsm_error_ok;
 }
 
-lsm_error lsm_entry_attr_insert_uint64_t(lsm_entry_handle *handle, uint8_t type,
+lsm_error lsm_entry_attr_insert_uint64_t(lsm_entry *entry, uint8_t type,
                                          uint64_t data) {
   lsm_str *s;
   LSM_RES(
       lsm_str_init_copy_n(&s, (char *)&data, sizeof(uint64_t) / sizeof(char)));
 
-  return lsm_entry_attr_insert(handle, type, s);
+  return lsm_entry_attr_insert(entry, type, s);
 }
 
-lsm_error lsm_entry_attr_insert_uint8_t(lsm_entry_handle *handle, uint8_t type,
+lsm_error lsm_entry_attr_insert_uint8_t(lsm_entry *entry, uint8_t type,
                                         uint8_t data) {
   lsm_str *s;
   LSM_RES(
       lsm_str_init_copy_n(&s, (char *)&data, sizeof(uint8_t) / sizeof(char)));
 
-  return lsm_entry_attr_insert(handle, type, s);
+  return lsm_entry_attr_insert(entry, type, s);
 }
 
-uint64_t lsm_entry_data_len(lsm_entry_handle *handle) {
+uint64_t lsm_entry_data_path_len(const lsm_store *store,
-  return handle->wrapper->entry->data_len;
+                                 const lsm_entry *entry) {
-}
+  const lsm_str *data_path = store->data_path;
-
+  const lsm_str *key = entry->key;
-uint64_t lsm_entry_data_path_len(const lsm_entry_handle *handle) {
-  const lsm_str *data_path = handle->store->data_path;
-  const lsm_str *key = handle->wrapper->entry->key;
 
   uint8_t levels =
       key->len <= LSM_STORE_DATA_LEVELS ? key->len : LSM_STORE_DATA_LEVELS;
@@ -271,9 +227,10 @@ uint64_t lsm_entry_data_path_len(const lsm_entry_handle *handle) {
          strlen(LSM_DATA_FILE_SUFFIX);
 }
 
-void lsm_entry_data_path(char *path, const lsm_entry_handle *handle) {
+void lsm_entry_data_path(char *path, const lsm_store *store,
-  const lsm_str *data_path = handle->store->data_path;
+                         const lsm_entry *entry) {
-  const lsm_str *key = handle->wrapper->entry->key;
+  const lsm_str *data_path = store->data_path;
+  const lsm_str *key = entry->key;
 
   uint8_t levels =
       key->len > LSM_STORE_DATA_LEVELS ? LSM_STORE_DATA_LEVELS : key->len;
@@ -298,12 +255,13 @@ void lsm_entry_data_path(char *path, const lsm_entry_handle *handle) {
   strcpy(&path[index], LSM_DATA_FILE_SUFFIX);
 }
 
-lsm_error lsm_entry_data_open_write(lsm_entry_handle *handle) {
+lsm_error lsm_entry_data_mkdirs(const lsm_store *store,
-  char path[lsm_entry_data_path_len(handle) + 1];
+                                const lsm_entry *entry) {
-  lsm_entry_data_path(path, handle);
+  char path[lsm_entry_data_path_len(store, entry) + 1];
+  lsm_entry_data_path(path, store, entry);
 
-  const lsm_str *data_path = handle->store->data_path;
+  const lsm_str *data_path = store->data_path;
-  const lsm_str *key = handle->wrapper->entry->key;
+  const lsm_str *key = entry->key;
 
   uint8_t levels =
       key->len <= LSM_STORE_DATA_LEVELS ? key->len : LSM_STORE_DATA_LEVELS;
@@ -320,43 +278,32 @@ lsm_error lsm_entry_data_open_write(lsm_entry_handle *handle) {
     path[data_path->len + 2 * (i + 1)] = '/';
   }
 
-  FILE *f = fopen(path, "ab");
+  return lsm_error_ok;
+}
+
+lsm_error lsm_entry_data_open(FILE **out, const lsm_store *store,
+                              const lsm_entry *entry, const char *mode) {
+  char path[lsm_entry_data_path_len(store, entry) + 1];
+  lsm_entry_data_path(path, store, entry);
+
+  FILE *f = fopen(path, mode);
 
   if (f == NULL) {
     return lsm_error_failed_io;
   }
 
-  handle->f = f;
+  if (out != NULL) {
-
+    *out = f;
-  return lsm_error_ok;
-}
-
-lsm_error lsm_entry_data_open_read(lsm_entry_handle *handle) {
-  char path[lsm_entry_data_path_len(handle) + 1];
-  lsm_entry_data_path(path, handle);
-
-  FILE *f = fopen(path, "rb");
-
-  if (f == NULL) {
-    return lsm_error_failed_io;
   }
 
-  handle->f = f;
-
   return lsm_error_ok;
 }
 
-lsm_error lsm_entry_data_remove(lsm_entry_handle *handle) {
+lsm_error lsm_entry_data_remove(const lsm_store *store,
-  const lsm_entry *entry = handle->wrapper->entry;
+                                const lsm_entry *entry) {
-
   if (entry->data_len > 0) {
-    if (handle->f != NULL) {
+    char data_path[lsm_entry_data_path_len(store, entry) + 1];
-      fclose(handle->f);
+    lsm_entry_data_path(data_path, store, entry);
-      handle->f = NULL;
-    }
-
-    char data_path[lsm_entry_data_path_len(handle) + 1];
-    lsm_entry_data_path(data_path, handle);
 
     if (remove(data_path) != 0) {
       return lsm_error_failed_io;

src/lander/lander.c

@@ -24,10 +24,15 @@ lnm_err lander_ctx_init(void **c_ctx, void *gctx) {
 }
 
 void lander_ctx_reset(lander_ctx *ctx) {
-  if (ctx->entry != NULL) {
+  if (ctx->entry.read != NULL) {
-    lsm_entry_close(ctx->entry);
+    if (ctx->write) {
+      lsm_write_close(ctx->entry.write);
+    } else {
+      lsm_read_close(ctx->entry.read);
+    }
 
-    ctx->entry = NULL;
+    ctx->entry.read = NULL;
+    ctx->write = false;
   }
 }
 
@@ -45,16 +50,23 @@ void lander_header_to_attr(lnm_http_loop_ctx *ctx, const char *header_name,
     lsm_str *value;
     lsm_str_init_copy_n(&value, (char *)header_value, header_value_len);
 
-    lsm_entry_attr_insert(c_ctx->entry, attr_type, value);
+    lsm_write_attr_insert(c_ctx->entry.write, attr_type, value);
   }
 }
 
 void lander_attr_to_header(lnm_http_loop_ctx *ctx, lander_attr_type attr_type,
                            lnm_http_header header_type) {
   lander_ctx *c_ctx = ctx->c;
-  lsm_str *value;
+  const lsm_str *value;
+  lsm_error res;
 
-  if (lsm_entry_attr_get(&value, c_ctx->entry, attr_type) == lsm_error_ok) {
+  if (c_ctx->write) {
+    res = lsm_write_attr_get(&value, c_ctx->entry.write, attr_type);
+  } else {
+    res = lsm_read_attr_get(&value, c_ctx->entry.read, attr_type);
+  }
+
+  if (res == lsm_error_ok) {
     lnm_http_res_add_header_len(&ctx->res, header_type,
                                 (char *)lsm_str_ptr(value), lsm_str_len(value),
                                 false);

src/lander/lander_delete.c

@@ -15,9 +15,9 @@ lnm_http_step_err lander_remove_entry(lnm_http_conn *conn) {
   lsm_str *key;
   lsm_str_init_copy_n(&key, (char *)key_s, key_len);
 
-  switch (lsm_store_open_write(&c_ctx->entry, c_gctx->store, key)) {
+  switch (lsm_store_open_write(&c_ctx->entry.write, c_gctx->store, key)) {
   case lsm_error_ok:
-    lsm_entry_remove(c_ctx->entry);
+    lsm_write_remove(c_ctx->entry.write);
     break;
   case lsm_error_not_found:
     ctx->res.status = lnm_http_status_not_found;

src/lander/lander_get.c

@@ -36,17 +36,17 @@ lnm_http_step_err lander_get_redirect(lnm_http_conn *conn) {
   lander_ctx *c_ctx = ctx->c;
 
   // For redirects, the URL is stored as an in-memory attribute
-  lsm_str *url_attr_val;
+  const lsm_str *url_attr_val;
 
   // This shouldn't be able to happen
-  if (lsm_entry_attr_get(&url_attr_val, c_ctx->entry, lander_attr_type_url) !=
+  if (lsm_read_attr_get(&url_attr_val, c_ctx->entry.read,
-      lsm_error_ok) {
+                        lander_attr_type_url) != lsm_error_ok) {
     lnm_lerror("lander", "%s",
                "Entry of type redirect detected without URL attribute");
 
     ctx->res.status = lnm_http_status_internal_server_error;
-    lsm_entry_close(c_ctx->entry);
+    lsm_read_close(c_ctx->entry.read);
-    c_ctx->entry = NULL;
+    c_ctx->entry.read = NULL;
 
     return lnm_http_step_err_res;
   }
@@ -68,7 +68,7 @@ lnm_err lander_entry_data_streamer(uint64_t *written, char *buf,
   lnm_http_loop_ctx *ctx = conn->ctx;
   lander_ctx *c_ctx = ctx->c;
 
-  lsm_entry_data_read(written, buf, c_ctx->entry, len);
+  lsm_read_data_read(written, buf, c_ctx->entry.read, len);
 
   return lnm_err_ok;
 }
@@ -78,7 +78,7 @@ lnm_http_step_err lander_get_paste(lnm_http_conn *conn) {
   lander_ctx *c_ctx = ctx->c;
 
   lnm_http_res_body_set_fn(&ctx->res, lander_entry_data_streamer,
-                           lsm_entry_data_len(c_ctx->entry));
+                           lsm_read_data_len(c_ctx->entry.read));
   lnm_http_res_add_header(&ctx->res, lnm_http_header_content_type, "text/plain",
                           false);
 
@@ -90,7 +90,7 @@ lnm_http_step_err lander_get_file(lnm_http_conn *conn) {
   lander_ctx *c_ctx = ctx->c;
 
   lnm_http_res_body_set_fn(&ctx->res, lander_entry_data_streamer,
-                           lsm_entry_data_len(c_ctx->entry));
+                           lsm_read_data_len(c_ctx->entry.read));
   lander_attr_to_header(ctx, lander_attr_type_content_type,
                         lnm_http_header_content_type);
 
@@ -108,7 +108,8 @@ lnm_http_step_err lander_get_entry(lnm_http_conn *conn) {
 
   lsm_str *key;
   lsm_str_init_copy_n(&key, (char *)key_s, key_len);
-  lsm_error lsm_res = lsm_store_open_read(&c_ctx->entry, c_gctx->store, key);
+  lsm_error lsm_res =
+      lsm_store_open_read(&c_ctx->entry.read, c_gctx->store, key);
   lsm_str_free(key);
 
   switch (lsm_res) {
@@ -123,7 +124,7 @@ lnm_http_step_err lander_get_entry(lnm_http_conn *conn) {
   }
 
   lander_entry_type t;
-  lsm_entry_attr_get_uint8_t((uint8_t *)&t, c_ctx->entry,
+  lsm_read_attr_get_uint8_t((uint8_t *)&t, c_ctx->entry.read,
                             lander_attr_type_entry_type);
 
   lnm_http_step_err res;

src/lander/lander_post.c

@@ -29,7 +29,7 @@ bool lander_insert_entry(lnm_http_loop_ctx *ctx, bool secure) {
 
   // With placeholders, the entry will already be open so an entry should no
   // longer be created
-  if (c_ctx->entry != NULL) {
+  if (c_ctx->entry.write != NULL) {
     return true;
   }
 
@@ -50,11 +50,12 @@ bool lander_insert_entry(lnm_http_loop_ctx *ctx, bool secure) {
   }
 
   // TODO free key on error
-  switch (lsm_store_insert(&c_ctx->entry, c_gctx->store, key)) {
+  switch (lsm_store_open_new(&c_ctx->entry.write, c_gctx->store, key)) {
   case lsm_error_already_present:
     ctx->res.status = lnm_http_status_conflict;
     return false;
   case lsm_error_ok:
+    c_ctx->write = true;
     break;
   default:
     ctx->res.status = lnm_http_status_internal_server_error;
@@ -82,7 +83,7 @@ static lnm_http_step_err __lander_post_redirect(lnm_http_conn *conn,
     return lnm_http_step_err_res;
   }
 
-  lsm_entry_attr_insert_uint8_t(c_ctx->entry, lander_attr_type_entry_type,
+  lsm_write_attr_insert_uint8_t(c_ctx->entry.write, lander_attr_type_entry_type,
                                 lander_entry_type_redirect);
 
   return lnm_http_step_err_done;
@@ -102,7 +103,7 @@ lnm_http_step_err lander_post_redirect_body_to_attr(lnm_http_conn *conn) {
 
   lsm_str *attr_value;
   lsm_str_init_copy_n(&attr_value, ctx->req.body.buf, ctx->req.body.len);
-  lsm_entry_attr_insert(c_ctx->entry, lander_attr_type_url, attr_value);
+  lsm_write_attr_insert(c_ctx->entry.write, lander_attr_type_url, attr_value);
 
   return lnm_http_step_err_done;
 }
@@ -115,7 +116,7 @@ static lnm_http_step_err __lander_post_paste(lnm_http_conn *conn, bool secure) {
     return lnm_http_step_err_res;
   }
 
-  lsm_entry_attr_insert_uint8_t(c_ctx->entry, lander_attr_type_entry_type,
+  lsm_write_attr_insert_uint8_t(c_ctx->entry.write, lander_attr_type_entry_type,
                                 lander_entry_type_paste);
   lander_header_to_attr(ctx, "X-Lander-Filename", lander_attr_type_file_name);
 
@@ -138,7 +139,7 @@ static lnm_http_step_err __lander_post_file(lnm_http_conn *conn, bool secure) {
     return lnm_http_step_err_res;
   }
 
-  lsm_entry_attr_insert_uint8_t(c_ctx->entry, lander_attr_type_entry_type,
+  lsm_write_attr_insert_uint8_t(c_ctx->entry.write, lander_attr_type_entry_type,
                                 lander_entry_type_file);
   lander_header_to_attr(ctx, "X-Lander-Content-Type",
                         lander_attr_type_content_type);
@@ -163,7 +164,7 @@ lnm_http_step_err __lander_post_placeholder(lnm_http_conn *conn, bool secure) {
     return lnm_http_step_err_res;
   }
 
-  lsm_entry_attr_insert_uint8_t(c_ctx->entry, lander_attr_type_entry_type,
+  lsm_write_attr_insert_uint8_t(c_ctx->entry.write, lander_attr_type_entry_type,
                                 lander_entry_type_placeholder);
 
   return lnm_http_step_err_done;

src/lander/lander_steps.c

@@ -11,19 +11,19 @@ lnm_http_step_err lander_stream_body_to_entry(lnm_http_conn *conn) {
   lnm_http_loop_ctx *ctx = conn->ctx;
   lander_ctx *c_ctx = ctx->c;
 
-  uint64_t to_append =
+  uint64_t to_append = LNM_MIN(conn->r.size - conn->r.read,
-      LNM_MIN(conn->r.size - conn->r.read,
+                               ctx->req.body.expected_len -
-              ctx->req.body.expected_len - lsm_entry_data_len(c_ctx->entry));
+                                   lsm_write_data_len(c_ctx->entry.write));
 
   lsm_str *data;
   lsm_str_init_copy_n(&data, (char *)&conn->r.buf[conn->r.read], to_append);
-  lsm_entry_data_append(c_ctx->entry, data);
+  lsm_write_data_append(c_ctx->entry.write, data);
 
   conn->r.read += to_append;
 
   lsm_str_free(data);
 
-  return lsm_entry_data_len(c_ctx->entry) == ctx->req.body.expected_len
+  return lsm_write_data_len(c_ctx->entry.write) == ctx->req.body.expected_len
              ? lnm_http_step_err_done
              : lnm_http_step_err_io_needed;
 }
@@ -32,7 +32,7 @@ lnm_http_step_err lander_commit_entry(lnm_http_conn *conn) {
   lnm_http_loop_ctx *ctx = conn->ctx;
   lander_ctx *c_ctx = ctx->c;
 
-  lsm_entry_commit(c_ctx->entry);
+  lsm_write_commit(c_ctx->entry.write);
 
   return lnm_http_step_err_done;
 }
@@ -54,17 +54,20 @@ lnm_http_step_err lander_auth_or_placeholder(lnm_http_conn *conn) {
   lsm_str *key;
   lsm_str_init_copy_n(&key, key_s, key_len);
 
-  lsm_error res = lsm_store_open_write(&c_ctx->entry, c_gctx->store, key);
+  lsm_error res = lsm_store_open_write(&c_ctx->entry.write, c_gctx->store, key);
 
   lsm_str_free(key);
 
   switch (res) {
   case lsm_error_ok: {
+    c_ctx->write = true;
+
     lander_entry_type t;
 
     // If the entry is a placeholder, the request is always authenticated
-    if ((lsm_entry_attr_get_uint8_t(
+    if ((lsm_write_attr_get_uint8_t(&t, c_ctx->entry.write,
-             &t, c_ctx->entry, lander_attr_type_entry_type) == lsm_error_ok) &&
+                                    lander_attr_type_entry_type) ==
+         lsm_error_ok) &&
         (t == lander_entry_type_placeholder)) {
       return lnm_http_step_err_done;
     } else {