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| @@ -2,6 +2,7 @@ #include <stdio.h> #include <stdlib.h> #include <string.h> +#include <stdint.h>
typedef struct { char* buffer; @@ -10,6 +11,105 @@ typedef struct { } InputBuffer;
+typedef enum { EXECUTE_SUCCESS, EXECUTE_TABLE_FULL } ExecuteResult; + +typedef enum { + META_COMMAND_SUCCESS, + META_COMMAND_UNRECOGNIZED_COMMAND +} MetaCommandResult; + +typedef enum { + PREPARE_SUCCESS, + PREPARE_SYNTAX_ERROR, + PREPARE_UNRECOGNIZED_STATEMENT + } PrepareResult; + +typedef enum { STATEMENT_INSERT, STATEMENT_SELECT } StatementType; + +#define COLUMN_USERNAME_SIZE 32 +#define COLUMN_EMAIL_SIZE 255 +typedef struct { + uint32_t id; + char username[COLUMN_USERNAME_SIZE]; + char email[COLUMN_EMAIL_SIZE]; +} Row; + +typedef struct { + StatementType type; + Row row_to_insert; +} Statement; + +#define size_of_attribute(Struct, Attribute) sizeof(((Struct*)0)->Attribute) + +const uint32_t ID_SIZE = size_of_attribute(Row, id); +const uint32_t USERNAME_SIZE = size_of_attribute(Row, username); +const uint32_t EMAIL_SIZE = size_of_attribute(Row, email); +const uint32_t ID_OFFSET = 0; +const uint32_t USERNAME_OFFSET = ID_OFFSET + ID_SIZE; +const uint32_t EMAIL_OFFSET = USERNAME_OFFSET + USERNAME_SIZE; +const uint32_t ROW_SIZE = ID_SIZE + USERNAME_SIZE + EMAIL_SIZE; + +const uint32_t PAGE_SIZE = 4096; +#define TABLE_MAX_PAGES 100 +const uint32_t ROWS_PER_PAGE = PAGE_SIZE / ROW_SIZE; +const uint32_t TABLE_MAX_ROWS = ROWS_PER_PAGE * TABLE_MAX_PAGES; + +typedef struct { + uint32_t num_rows; + void* pages[TABLE_MAX_PAGES]; +} Table; + +void print_row(Row* row) { + printf("(%d, %s, %s)\n", row->id, row->username, row->email); +} + +void serialize_row(Row* source, void* destination) { + memcpy(destination + ID_OFFSET, &(source->id), ID_SIZE); + memcpy(destination + USERNAME_OFFSET, &(source->username), USERNAME_SIZE); + memcpy(destination + EMAIL_OFFSET, &(source->email), EMAIL_SIZE); +} + +void deserialize_row(void *source, Row* destination) { + memcpy(&(destination->id), source + ID_OFFSET, ID_SIZE); + memcpy(&(destination->username), source + USERNAME_OFFSET, USERNAME_SIZE); + memcpy(&(destination->email), source + EMAIL_OFFSET, EMAIL_SIZE); +} + +void* row_slot(Table* table, uint32_t row_num) { + uint32_t page_num = row_num / ROWS_PER_PAGE; + void *page = table->pages[page_num]; + if (page == NULL) { + + page = table->pages[page_num] = malloc(PAGE_SIZE); + } + uint32_t row_offset = row_num % ROWS_PER_PAGE; + uint32_t byte_offset = row_offset * ROW_SIZE; + return page + byte_offset; +} + +Table* new_table() { + Table* table = malloc(sizeof(Table)); + table->num_rows = 0; + for (uint32_t i = 0; i < TABLE_MAX_PAGES; i++) { + table->pages[i] = NULL; + } + return table; +} + +void free_table(Table* table) { + for (int i = 0; table->pages[i]; i++) { + free(table->pages[i]); + } + free(table); +} + InputBuffer* new_input_buffer() { InputBuffer* input_buffer = malloc(sizeof(InputBuffer)); input_buffer->buffer = NULL; @@ -40,17 +140,105 @@ void close_input_buffer(InputBuffer* input_buffer) { free(input_buffer); }
+MetaCommandResult do_meta_command(InputBuffer* input_buffer, Table *table) { + if (strcmp(input_buffer->buffer, ".exit") == 0) { + close_input_buffer(input_buffer); + free_table(table); + exit(EXIT_SUCCESS); + } else { + return META_COMMAND_UNRECOGNIZED_COMMAND; + } +} + +PrepareResult prepare_statement(InputBuffer* input_buffer, + Statement* statement) { + if (strncmp(input_buffer->buffer, "insert", 6) == 0) { + statement->type = STATEMENT_INSERT; + int args_assigned = sscanf( + input_buffer->buffer, "insert %d %s %s", &(statement->row_to_insert.id), + statement->row_to_insert.username, statement->row_to_insert.email + ); + if (args_assigned < 3) { + return PREPARE_SYNTAX_ERROR; + } + return PREPARE_SUCCESS; + } + if (strcmp(input_buffer->buffer, "select") == 0) { + statement->type = STATEMENT_SELECT; + return PREPARE_SUCCESS; + } + + return PREPARE_UNRECOGNIZED_STATEMENT; +} + +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); + + serialize_row(row_to_insert, row_slot(table, table->num_rows)); + table->num_rows += 1; + + return EXECUTE_SUCCESS; +} + +ExecuteResult execute_select(Statement* statement, Table* table) { + Row row; + for (uint32_t i = 0; i < table->num_rows; i++) { + deserialize_row(row_slot(table, i), &row); + print_row(&row); + } + return EXECUTE_SUCCESS; +} + +ExecuteResult execute_statement(Statement* statement, Table *table) { + switch (statement->type) { + case (STATEMENT_INSERT): + return execute_insert(statement, table); + case (STATEMENT_SELECT): + return execute_select(statement, table); + } +} + int main(int argc, char* argv[]) { + Table* table = new_table(); InputBuffer* input_buffer = new_input_buffer(); while (true) { print_prompt(); read_input(input_buffer);
- if (strcmp(input_buffer->buffer, ".exit") == 0) { - close_input_buffer(input_buffer); - exit(EXIT_SUCCESS); - } else { - printf("Unrecognized command '%s'.\n", input_buffer->buffer); + if (input_buffer->buffer[0] == '.') { + switch (do_meta_command(input_buffer, table)) { + case (META_COMMAND_SUCCESS): + continue; + case (META_COMMAND_UNRECOGNIZED_COMMAND): + printf("Unrecognized command '%s'\n", input_buffer->buffer); + continue; + } + } + + Statement statement; + switch (prepare_statement(input_buffer, &statement)) { + case (PREPARE_SUCCESS): + break; + case (PREPARE_SYNTAX_ERROR): + printf("Syntax error. Could not parse statement.\n"); + continue; + case (PREPARE_UNRECOGNIZED_STATEMENT): + printf("Unrecognized keyword at start of '%s'.\n", + input_buffer->buffer); + continue; + } + + switch (execute_statement(&statement, table)) { + case (EXECUTE_SUCCESS): + printf("Executed.\n"); + break; + case (EXECUTE_TABLE_FULL): + printf("Error: Table full.\n"); + break; } } }
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