From f85583c4cc240670fb940e2df8f3060b6129dd14 Mon Sep 17 00:00:00 2001
From: Timothy Warren <twarren@nabancard.com>
Date: Mon, 11 Sep 2017 11:49:58 -0400
Subject: [PATCH] Finish step 5

---
 db.c              | 75 +++++++++++++++++++++++++++++++++++++++++++++--
 spec/main_spec.rb |  6 +++-
 2 files changed, 77 insertions(+), 4 deletions(-)

diff --git a/db.c b/db.c
index 2a67162..dea9694 100644
--- a/db.c
+++ b/db.c
@@ -114,8 +114,70 @@ void read_input(InputBuffer* input_buffer) {
     input_buffer->buffer[bytes_read - 1] = 0;
 }
 
-MetaCommandResult do_meta_command(InputBuffer* input_buffer) {
+void pager_flush(Pager* pager, uint32_t page_num, uint32_t size) {
+    if (pager->pages[page_num] == NULL) {
+        printf("Tried to flush null page\n");
+        exit(EXIT_FAILURE);
+    }
+
+    off_t offset = lseek(pager->file_descriptor, page_num * PAGE_SIZE, SEEK_SET);
+
+    if (offset == -1) {
+        printf("Error seeking: %d\n", errno);
+        exit(EXIT_FAILURE);
+    }
+
+    ssize_t bytes_written = write(pager->file_descriptor, pager->pages[page_num], size);
+
+    if (bytes_written == -1) {
+        printf("Error writing: %d\n", errno);
+        exit(EXIT_FAILURE);
+    }
+}
+
+void db_close(Table* table) {
+    Pager* pager = table->pager;
+    uint32_t num_full_pages = table->num_rows / ROWS_PER_PAGE;
+
+    for (uint32_t i = 0; i < num_full_pages; i++) {
+        if (pager->pages[i] == NULL) {
+            continue;
+        }
+        pager_flush(pager, i, PAGE_SIZE);
+        free(pager->pages[i]);
+        pager->pages[i] = NULL;
+    }
+
+    // There may be a partial page to write to the end of the file
+    // This should not be needed after we switch to a B-tree
+    uint32_t num_additional_rows = table->num_rows % ROWS_PER_PAGE;
+    if (num_additional_rows > 0) {
+        uint32_t page_num = num_full_pages;
+        if (pager->pages[page_num] != NULL) {
+            pager_flush(pager, page_num, num_additional_rows * ROW_SIZE);
+            free(pager->pages[page_num]);
+            pager->pages[page_num] = NULL;
+        }
+    }
+
+    int result = close(pager->file_descriptor);
+    if (result == -1) {
+        printf("Error closing db file.\n");
+        exit(EXIT_FAILURE);
+    }
+    for(uint32_t i = 0; i < TABLE_MAX_PAGES; i++) {
+        void* page = pager->pages[i];
+        if (page) {
+            free(page);
+            pager->pages[i] = NULL;
+        }
+    }
+    free(pager);
+}
+
+MetaCommandResult do_meta_command(InputBuffer* input_buffer, Table* table) {
     if (strcmp(input_buffer->buffer, ".exit") == 0) {
+        db_close(table);
         exit(EXIT_SUCCESS);
     } else {
         return META_COMMAND_UNRECOGNIZED_COMMAND;
@@ -285,14 +347,21 @@ Table* db_open(const char* filename) {
 }
 
 int main(int argc, char* argv[]) {
-    Table* table = new_table();
+    if (argc < 2) {
+        printf("Must supply a database filename\n");
+        exit(EXIT_FAILURE);
+    }
+
+    char* filename = argv[1];
+    Table* table = db_open(filename);
+
     InputBuffer* input_buffer = new_input_buffer();
     while (true) {
         print_prompt();
         read_input(input_buffer);
 
         if (input_buffer->buffer[0] == '.') {
-            switch (do_meta_command(input_buffer)) {
+            switch (do_meta_command(input_buffer, table)) {
                 case (META_COMMAND_SUCCESS):
                     continue;
 
diff --git a/spec/main_spec.rb b/spec/main_spec.rb
index bd02bc3..0bd17ea 100644
--- a/spec/main_spec.rb
+++ b/spec/main_spec.rb
@@ -1,7 +1,11 @@
 describe 'database' do
+  before do
+    `rm -rf test.db`
+  end
+
   def run_script(commands)
     raw_output = nil
-    IO.popen("./db", "r+") do |pipe|
+    IO.popen("./db test.db", "r+") do |pipe|
       commands.each do |command|
         pipe.puts command
       end