From 226873219bd11dbf800f44e6ca9dfa4068290247 Mon Sep 17 00:00:00 2001
From: Chewing_Bever <roosensjef@gmail.com>
Date: Wed, 8 Nov 2023 10:40:12 +0100
Subject: [PATCH] refactor(lsm): slightly clean up disk write code

---
 lsm/src/store/lsm_store_disk_write.c | 60 ++++++++++++----------------
 1 file changed, 25 insertions(+), 35 deletions(-)

diff --git a/lsm/src/store/lsm_store_disk_write.c b/lsm/src/store/lsm_store_disk_write.c
index 8b02319..9813f40 100644
--- a/lsm/src/store/lsm_store_disk_write.c
+++ b/lsm/src/store/lsm_store_disk_write.c
@@ -22,7 +22,18 @@ static lsm_error lsm_entry_write_str(FILE *f, lsm_str *s) {
   return lsm_error_ok;
 }
 
-lsm_error lsm_entry_write_db(uint64_t *size, FILE *db_file, lsm_entry *entry) {
+static lsm_error lsm_seek(FILE *f, uint64_t pos) {
+  if (fseek(f, pos, SEEK_SET) != 0) {
+    return lsm_error_failed_io;
+  }
+
+  return lsm_error_ok;
+}
+
+lsm_error lsm_entry_write_db(uint64_t *size, FILE *db_file, lsm_entry *entry,
+                             uint64_t pos) {
+  LSM_RES(lsm_seek(db_file, pos));
+
   // First we write how many attributes follow
   LSM_RES(lsm_entry_write_uint64_t(db_file, entry->attrs.count));
   *size = sizeof(uint64_t);
@@ -42,7 +53,8 @@ lsm_error lsm_entry_write_db(uint64_t *size, FILE *db_file, lsm_entry *entry) {
 }
 
 lsm_error lsm_entry_write_idx(uint64_t *size, FILE *idx_file, lsm_entry *entry,
-                              uint64_t offset, uint64_t len) {
+                              uint64_t offset, uint64_t len, uint64_t pos) {
+  LSM_RES(lsm_seek(idx_file, pos));
   LSM_RES(lsm_entry_write_uint64_t(idx_file, lsm_str_len(entry->key)));
   LSM_RES(lsm_entry_write_str(idx_file, entry->key));
   LSM_RES(lsm_entry_write_uint64_t(idx_file, offset));
@@ -56,16 +68,9 @@ lsm_error lsm_entry_write_idx(uint64_t *size, FILE *idx_file, lsm_entry *entry,
 lsm_error lsm_entry_sync(lsm_store *store, lsm_entry_handle *handle) {
   pthread_mutex_lock(&store->db_lock);
 
-  // Append entry to end of database file
-  if (fseek(store->db_file, store->db_file_size, SEEK_SET) != 0) {
-    pthread_mutex_unlock(&store->db_lock);
-
-    return lsm_error_failed_io;
-  }
-
   uint64_t entry_size;
-  lsm_error res =
-      lsm_entry_write_db(&entry_size, store->db_file, handle->wrapper->entry);
+  lsm_error res = lsm_entry_write_db(
+      &entry_size, store->db_file, handle->wrapper->entry, store->db_file_size);
   fflush(store->db_file);
 
   if (res != lsm_error_ok) {
@@ -82,40 +87,25 @@ lsm_error lsm_entry_sync(lsm_store *store, lsm_entry_handle *handle) {
   // Append entry to index file
   pthread_mutex_lock(&store->idx_lock);
 
-  if (fseek(store->idx_file, store->idx_file_size, SEEK_SET) != 0) {
-    printf("failed seek, %lu\n", store->idx_file_size);
-    pthread_mutex_unlock(&store->idx_lock);
-
-    return lsm_error_failed_io;
-  }
-
-  res = lsm_entry_write_idx(&entry_size, store->idx_file,
-                            handle->wrapper->entry, entry_index, entry_size);
+  res =
+      lsm_entry_write_idx(&entry_size, store->idx_file, handle->wrapper->entry,
+                          entry_index, entry_size, store->idx_file_size);
 
   if (res == lsm_error_ok) {
     // Update the counter at the beginning of the file
+    rewind(store->idx_file);
+
     uint64_t new_block_count = store->idx_file_block_count + 1;
 
-    if (fseek(store->idx_file, 0, SEEK_SET) != 0) {
-      pthread_mutex_unlock(&store->idx_lock);
+    res = lsm_entry_write_uint64_t(store->idx_file, new_block_count);
 
-      return lsm_error_failed_io;
+    if (res == lsm_error_ok) {
+      store->idx_file_size += entry_size;
+      store->idx_file_block_count = new_block_count;
     }
-
-    size_t r = fwrite(&new_block_count, sizeof(uint64_t), 1, store->idx_file);
-
-    if (r != lsm_error_ok) {
-      pthread_mutex_unlock(&store->idx_lock);
-
-      return res;
-    }
-
-    store->idx_file_size += entry_size;
-    store->idx_file_block_count = new_block_count;
   }
 
   fflush(store->idx_file);
-
   pthread_mutex_unlock(&store->idx_lock);
 
   return res;