feat(lsm): data streaming, random other stuff, locks

lsm/include/lsm.h

@@ -15,7 +15,9 @@ typedef enum lsm_error {
   lsm_error_failed_alloc = 1,
   lsm_error_not_found = 2,
   lsm_error_already_present = 3,
-  lsm_error_null_value = 4
+  lsm_error_null_value = 4,
+  lsm_error_failed_io = 5,
+  lsm_error_lock_busy = 6,
 } lsm_error;
 
 /*typedef struct lsm_string { */

lsm/include/lsm/store.h

@@ -104,7 +104,7 @@ lsm_error lsm_store_init(lsm_store **ptr);
  * @param db_path path to the database file
  * @param data_path path to the data directory
  */
-lsm_error lsm_store_open(lsm_store **ptr, char *db_path, char *data_path);
+lsm_error lsm_store_open(lsm_store **ptr, lsm_str *db_path, lsm_str *data_path);
 
 /**
  * Dealocate an existing lsm_store object.
@@ -114,16 +114,37 @@ lsm_error lsm_store_open(lsm_store **ptr, char *db_path, char *data_path);
 void lsm_store_free(lsm_store *store);
 
 /**
- * Search for an entry in the store.
+ * Retrieve an entry from the store, preparing & locking it for the purpose of
+ * reading.
  *
- * @param out pointer to store entry pointer in
- * @param store store to search in
- * @param key key to look with
+ * @param out pointer to store entry pointer
+ * @param store store to retrieve entry from
+ * @param key key to search
  */
-lsm_error lsm_store_search(lsm_entry **out, lsm_store *store, lsm_str *key);
+lsm_error lsm_store_get_read(lsm_entry **out, lsm_store *store, lsm_str *key);
 
 /**
- * Allocate a new entry in the store with the specified key.
+ * Retrieve an entry from the store for the purposes of writing. This
+ * write-locks the entry.
+ *
+ * @param out pointer to store entry pointer
+ * @param store store to retrieve entry from
+ * @param key key to search
+ */
+lsm_error lsm_store_get_write(lsm_entry **out, lsm_store *store, lsm_str *key);
+
+/**
+ * Unlock a locked entry.
+ *
+ * @param store store to unlock entry in
+ * @param entry entry to unlock
+ */
+lsm_error lsm_store_unlock(lsm_store *store, lsm_entry *entry);
+
+/**
+ * Allocate a new entry in the store with the specified key. The entry returned
+ * will be write-locked, and should be unlocked after streaming the necessary
+ * data.
  *
  * @param out pointer to store new entry pointer in
  * @param store store to modify
@@ -141,6 +162,7 @@ lsm_error lsm_store_insert(lsm_entry **out, lsm_store *store, lsm_str *key);
  * @param entry entry to append data to
  * @param data data to append
  */
-lsm_error lsm_store_data_append(lsm_store *store, lsm_entry *entry, lsm_str *data);
+lsm_error lsm_store_data_write(lsm_store *store, lsm_entry *entry,
+                               lsm_str *data);
 
 #endif

lsm/src/_include/lsm/store_internal.h

@@ -1,6 +1,7 @@
 #ifndef LSM_STORE_INTERNAL
 #define LSM_STORE_INTERNAL
 
+#include <pthread.h>
 #include <stdio.h>
 
 #include "lsm/store.h"
@@ -29,10 +30,17 @@ struct lsm_entry {
   } data;
 };
 
+typedef struct lsm_entry_wrapper {
+  pthread_rwlock_t lock;
+  lsm_entry *entry;
+} lsm_entry_wrapper;
+
+lsm_error lsm_entry_wrapper_init(lsm_entry_wrapper **ptr);
+
 struct lsm_store {
   lsm_trie *trie;
-  char *data_path;
-  char *db_path;
+  lsm_str *data_path;
+  lsm_str *db_path;
 };
 
 #endif

lsm/src/store/lsm_store.c

@@ -1,10 +1,11 @@
+#include <pthread.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include "lsm.h"
 #include "lsm/store.h"
-#include "lsm/trie.h"
 #include "lsm/store_internal.h"
+#include "lsm/trie.h"
 
 lsm_error lsm_store_init(lsm_store **ptr) {
   lsm_store *store = calloc(1, sizeof(lsm_store));
@@ -26,7 +27,8 @@ lsm_error lsm_store_init(lsm_store **ptr) {
   return lsm_error_ok;
 }
 
-lsm_error lsm_store_open(lsm_store **ptr, char *db_path, char *data_path) {
+lsm_error lsm_store_open(lsm_store **ptr, lsm_str *db_path,
+                         lsm_str *data_path) {
   lsm_store *store;
   LSM_RES(lsm_store_init(&store));
 
@@ -40,24 +42,67 @@ lsm_error lsm_store_open(lsm_store **ptr, char *db_path, char *data_path) {
   return lsm_error_ok;
 }
 
-lsm_error lsm_store_search(lsm_entry **out, lsm_store *store, lsm_str *key) {
-  return lsm_trie_search((void **)out, store->trie, key);
+lsm_error lsm_store_get_read(lsm_entry **out, lsm_store *store, lsm_str *key) {
+  lsm_entry_wrapper *wrapper;
+
+  LSM_RES(lsm_trie_search((void **)&wrapper, store->trie, key));
+
+  // We don't want to block the thread
+  if (pthread_rwlock_tryrdlock(&wrapper->lock) != 0) {
+    return lsm_error_lock_busy;
+  }
+
+  lsm_entry *entry = wrapper->entry;
+
+  // While the trie's data field will never be NULL, the actual entry pointer
+  // might be
+  if (entry == NULL) {
+    pthread_rwlock_unlock(&wrapper->lock);
+
+    return lsm_error_not_found;
+  }
+
+  // Open a new file descriptor if needed
+  if (entry->data.on_disk && (entry->data.value.file == NULL)) {
+    char path[store->data_path->len + entry->key->len + 2];
+    sprintf(path, "%s/%s", lsm_str_ptr(store->data_path),
+            lsm_str_ptr(entry->key));
+
+    FILE *f = fopen(path, "rb");
+
+    if (f == NULL) {
+      return lsm_error_failed_io;
+    }
+
+    entry->data.value.file = f;
+  }
+
+  return lsm_error_ok;
 }
 
 lsm_error lsm_store_insert(lsm_entry **out, lsm_store *store, lsm_str *key) {
-  lsm_entry *entry;
+  lsm_entry_wrapper *wrapper;
+  LSM_RES(lsm_entry_wrapper_init(&wrapper));
 
+  lsm_entry *entry;
   LSM_RES(lsm_entry_init(&entry));
-  LSM_RES(lsm_trie_insert(store->trie, key, entry));
 
   entry->key = key;
+  wrapper->entry = entry;
+  pthread_rwlock_wrlock(&wrapper->lock);
+
+  // TODO mem leak if already present
+  LSM_RES(lsm_trie_insert(store->trie, key, wrapper));
+
   *out = entry;
 
   return lsm_error_ok;
 }
 
-lsm_error lsm_store_data_append(lsm_store *store, lsm_entry *entry, lsm_str *data) {
+lsm_error lsm_store_data_write(lsm_store *store, lsm_entry *entry,
+                               lsm_str *data) {
   uint64_t new_len = entry->data.len + lsm_str_len(data);
+  const char *data_s = lsm_str_ptr(data);
 
   // Data is in memory and still fits -> keep it in memory
   if ((new_len <= LSM_STORE_DISK_THRESHOLD) && (!entry->data.on_disk)) {
@@ -67,7 +112,7 @@ lsm_error lsm_store_data_append(lsm_store *store, lsm_entry *entry, lsm_str *dat
       return lsm_error_failed_alloc;
     }
 
-    memcpy(&buf[entry->data.len], lsm_str_ptr(data), lsm_str_len(data));
+    memcpy(&buf[entry->data.len], data_s, lsm_str_len(data));
     entry->data.value.ptr = buf;
     entry->data.len = new_len;
   }
@@ -75,7 +120,28 @@ lsm_error lsm_store_data_append(lsm_store *store, lsm_entry *entry, lsm_str *dat
   else {
     // Data is not yet on disk, so we create the file
     if (!entry->data.on_disk) {
+      char path[store->data_path->len + entry->key->len + 2];
+      sprintf(path, "%s/%s", lsm_str_ptr(store->data_path),
+              lsm_str_ptr(entry->key));
 
+      FILE *f = fopen(path, "w");
+
+      if (f == NULL) {
+        return lsm_error_failed_io;
+      }
+
+      entry->data.value.file = f;
+      entry->data.on_disk = true;
+
+      // TODO free old buff, write original data to file
+    }
+
+    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,
+                        entry->data.value.file);
     }
   }
 

lsm/src/store/lsm_store_entry.c

@@ -1,4 +1,5 @@
 #include <fcntl.h>
+#include <pthread.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -17,6 +18,20 @@ lsm_error lsm_entry_init(lsm_entry **ptr) {
   return lsm_error_ok;
 }
 
+lsm_error lsm_entry_wrapper_init(lsm_entry_wrapper **ptr) {
+  lsm_entry_wrapper *wrap = calloc(1, sizeof(lsm_entry_wrapper));
+
+  if (wrap == NULL) {
+    return lsm_error_failed_alloc;
+  }
+
+  pthread_rwlock_init(&wrap->lock, NULL);
+
+  *ptr = wrap;
+
+  return lsm_error_ok;
+}
+
 bool lsm_entry_attr_present(lsm_entry *entry, lsm_attr_type type) {
   return (entry->attrs.bitmap & type) != 0;
 }