Complete step 6

This commit is contained in:
Timothy Warren 2019-03-18 12:12:13 -04:00
parent f85583c4cc
commit 7b36ca8c16

54
db.c
View File

@ -83,6 +83,13 @@ struct Table_t {
};
typedef struct Table_t Table;
struct Cursor_t {
Table* table;
uint32_t row_num;
bool end_of_table; // Indicates a position one past the last element
};
typedef struct Cursor_t Cursor;
InputBuffer* new_input_buffer() {
InputBuffer* input_buffer = malloc(sizeof(InputBuffer));
@ -242,6 +249,24 @@ void deserialize_row(void* source, Row* destination) {
memcpy(&(destination->email), source + EMAIL_OFFSET, EMAIL_SIZE);
}
Cursor* table_start(Table* table) {
Cursor* cursor = malloc(sizeof(Cursor));
cursor->table = table;
cursor->row_num = 0;
cursor->end_of_table = (table->num_rows == 0);
return cursor;
}
Cursor* table_end(Table* table) {
Cursor* cursor = malloc(sizeof(Cursor));
cursor->table = table;
cursor->row_num = table->num_rows;
cursor->end_of_table = true;
return cursor;
}
void* get_page(Pager* pager, uint32_t page_num) {
if (page_num > TABLE_MAX_PAGES) {
printf("Tried to fetch page number out of bounds. %d > %d\n", page_num, TABLE_MAX_PAGES);
@ -273,33 +298,50 @@ void* get_page(Pager* pager, uint32_t page_num) {
return pager->pages[page_num];
}
void* row_slot(Table* table, uint32_t row_num) {
void* cursor_value(Cursor* cursor) {
uint32_t row_num = cursor->row_num;
uint32_t page_num = row_num / ROWS_PER_PAGE;
void* page = get_page(table->pager, page_num);
void* page = get_page(cursor->table->pager, page_num);
uint32_t row_offset = row_num % ROWS_PER_PAGE;
uint32_t byte_offset = row_offset * ROW_SIZE;
return page + byte_offset;
}
void cursor_advance(Cursor* cursor) {
cursor->row_num += 1;
if (cursor->row_num >= cursor->table->num_rows) {
cursor->end_of_table = true;
}
}
ExecuteResult execute_insert(Statement* statement, Table* table) {
if (table->num_rows >= TABLE_MAX_ROWS) {
return EXECUTE_TABLE_FULL;
}
Row* row_to_insert = &(statement->row_to_insert);
Cursor* cursor = table_end(table);
serialize_row(row_to_insert, row_slot(table, table->num_rows));
serialize_row(row_to_insert, cursor_value(cursor));
table->num_rows += 1;
free(cursor);
return EXECUTE_SUCCESS;
}
ExecuteResult execute_select(Statement* statement, Table* table) {
Cursor* cursor = table_start(table);
Row row;
for (uint32_t i = 0; i < table->num_rows; i++) {
deserialize_row(row_slot(table, i), &row);
while (!(cursor->end_of_table)) {
deserialize_row(cursor_value(cursor), &row);
print_row(&row);
cursor_advance(cursor);
}
free(cursor);
return EXECUTE_SUCCESS;
}
@ -335,6 +377,8 @@ Pager* pager_open(const char* filename) {
return pager;
}
Table* db_open(const char* filename) {
Pager* pager = pager_open(filename);
uint32_t num_rows = pager->file_length / ROW_SIZE;