374 lines
12 KiB
C
374 lines
12 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <YeltsinDB/error_code.h>
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#include <YeltsinDB/constants.h>
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#include <YeltsinDB/macro.h>
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#include <YeltsinDB/table_page.h>
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#include <YeltsinDB/ydb.h>
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/** @todo These things:
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* - Page data (current, maybe cache next and prev too)
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* - MAYBE query caching
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*/
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struct __YDB_Engine {
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uint8_t ver_major; /**< A major version of loaded table. */
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uint8_t ver_minor; /**< A minor version of loaded table. */
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YDB_Offset first_page_offset; /**< A location of the first page in file. */
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YDB_Offset last_page_offset; /**< A location of the last page in file. */
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YDB_Offset last_free_page_offset; /**< A location of last free page in file. */
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YDB_Offset prev_page_offset; /**< A location of previous page in file. */
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YDB_Offset curr_page_offset; /**< A location of current page in file. */
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YDB_Offset next_page_offset; /**< A location of next page in file. */
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int64_t current_page_index; /**< Current page index in range [0, page_count). */
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YDB_TablePage *curr_page; /**< A pointer to the current page. */
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uint8_t in_use; /**< "In use" flag. */
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char *filename; /**< Current table data file name. */
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FILE *fd; /**< Current table data file descriptor. */
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};
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YDB_Engine *ydb_init_instance() {
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YDB_Engine *new_instance = calloc(1, sizeof(YDB_Engine));
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return new_instance;
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}
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void ydb_terminate_instance(YDB_Engine *instance) {
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ydb_unload_table(instance);
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// And after all that, the instance could be freed
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free(instance);
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}
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// Internal usage only!
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// Its only purpose to read page data and set next_page offset.
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// You should write prev_page offset on your own.
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inline YDB_Error __ydb_read_page(YDB_Engine *inst) {
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THROW_IF_NULL(inst, YDB_ERR_INSTANCE_NOT_INITIALIZED);
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fseek(inst->fd, inst->curr_page_offset, SEEK_SET);
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char p_data[YDB_TABLE_PAGE_SIZE];
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size_t bytes_read = fread(p_data, 1, YDB_TABLE_PAGE_SIZE, inst->fd);
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if (bytes_read != YDB_TABLE_PAGE_SIZE) {
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return YDB_ERR_TABLE_DATA_CORRUPTED;
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}
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YDB_Flags page_flags = p_data[0];
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YDB_Offset next;
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YDB_PageSize row_count;
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memcpy(&next, p_data + sizeof(page_flags), sizeof(next));
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memcpy(&row_count, p_data + sizeof(page_flags) + sizeof(next), sizeof(row_count));
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//TODO move it to consts. Also page meta size could differ in different major versions.
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const YDB_PageSize meta_size = sizeof(page_flags) + sizeof(next) + sizeof(row_count);
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const YDB_PageSize data_size = YDB_TABLE_PAGE_SIZE - meta_size;
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YDB_TablePage *p = ydb_page_alloc(data_size);
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ydb_page_flags_set(p, page_flags);
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ydb_page_row_count_set(p, row_count);
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YDB_Error write_status = ydb_page_data_write(p, p_data + meta_size, data_size);
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if (write_status) return write_status;
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inst->curr_page = p;
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inst->next_page_offset = next;
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return YDB_ERR_SUCCESS;
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}
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// Moves file position to allocated block.
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// Also changes last_free_page_offset.
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inline YDB_Offset __ydb_allocate_page_and_seek(YDB_Engine *inst) {
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YDB_Offset result = 0;
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// If no free pages in the table, then...
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if (inst->last_free_page_offset == 0) {
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// Return the end of the file where a new page will be allocated
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fseek(inst->fd, 0, SEEK_END);
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result = ftell(inst->fd);
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// Write next page offset in the previous page
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fseek(inst->fd, inst->last_page_offset + 1, SEEK_SET); // Skip page flag
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fwrite(&result, sizeof(result), 1, inst->fd);
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// Allocate an empty chunk
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fseek(inst->fd, 0, SEEK_END);
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char* new_page_data = calloc(1, YDB_TABLE_PAGE_SIZE);
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fwrite(new_page_data, YDB_TABLE_PAGE_SIZE, 1, inst->fd);
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free(new_page_data);
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// Write last page offset
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inst->last_page_offset = result;
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fseek(inst->fd, 14, SEEK_SET); // TODO move magic offsets somewhere
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fwrite(&inst->last_page_offset, sizeof(YDB_Offset), 1, inst->fd);
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fflush(inst->fd);
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} else {
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// Return last free page offset
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result = inst->last_free_page_offset;
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// Read last free page offset after allocation
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fseek(inst->fd, result + 1, SEEK_SET); // Skip flag
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fread(&(inst->last_free_page_offset), sizeof(YDB_Offset), 1, inst->fd);
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fseek(inst->fd, -(long)(sizeof(YDB_Offset) + 1), SEEK_CUR);
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// Rewrite page header
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char page_header[] = "\x00" // No flags
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"\x00\x00\x00\x00\x00\x00\x00\x00" // No next page
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"\x00\x00"; // No rows
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fwrite(page_header, sizeof(page_header)-1, 1, inst->fd);
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// Write last free page offset after allocation in file
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fseek(inst->fd, 22, SEEK_SET); // Skip unneeded data TODO beautify it
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fwrite(&(inst->last_free_page_offset), sizeof(YDB_Offset), 1, inst->fd);
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}
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fflush(inst->fd);
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fseek(inst->fd, result, SEEK_SET);
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return result;
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}
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YDB_Error ydb_load_table(YDB_Engine *instance, const char *path) {
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THROW_IF_NULL(instance, YDB_ERR_INSTANCE_NOT_INITIALIZED);
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THROW_IF_NULL(!instance->in_use, YDB_ERR_INSTANCE_IN_USE);
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instance->in_use = -1; // unsigned value overflow to fill all the bits
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instance->filename = strdup(path);
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if (access(instance->filename, F_OK) == -1) {
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// TODO: Windows does not check W_OK correctly, use other methods.
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// TODO: if can't read/write, throw other error
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return YDB_ERR_TABLE_NOT_EXIST;
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}
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instance->fd = fopen(instance->filename, "rb+");
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THROW_IF_NULL(instance->fd, YDB_ERR_UNKNOWN); // TODO file open error
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char signature[4];
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fread(signature, 1, 4, instance->fd);
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int signature_match = memcmp(signature, YDB_TABLE_FILE_SIGN, 4) == 0;
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if (!signature_match) {
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return YDB_ERR_TABLE_DATA_CORRUPTED;
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}
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fread(&(instance->ver_major), sizeof(instance->ver_major), 1, instance->fd);
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fread(&(instance->ver_minor), sizeof(instance->ver_minor), 1, instance->fd);
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if (instance->ver_major != 0) { // TODO proper version check
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return YDB_ERR_TABLE_DATA_VERSION_MISMATCH;
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}
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fread(&(instance->first_page_offset), sizeof(YDB_Offset), 1, instance->fd);
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fread(&(instance->last_page_offset), sizeof(YDB_Offset), 1, instance->fd);
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fread(&(instance->last_free_page_offset), sizeof(YDB_Offset), 1, instance->fd);
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// TODO check offsets
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instance->curr_page_offset = instance->first_page_offset;
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return __ydb_read_page(instance);
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}
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YDB_Error ydb_unload_table(YDB_Engine *instance) {
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THROW_IF_NULL(instance, YDB_ERR_INSTANCE_NOT_INITIALIZED);
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THROW_IF_NULL(instance->in_use, YDB_ERR_INSTANCE_NOT_IN_USE);
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THROW_IF_NULL(instance->curr_page, YDB_ERR_PAGE_NOT_INITIALIZED);
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YDB_Engine *i = instance;
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i->ver_major = 0;
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i->ver_minor = 0;
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i->first_page_offset = 0;
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i->last_page_offset = 0;
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i->last_free_page_offset = 0;
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i->prev_page_offset = 0;
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i->curr_page_offset = 0;
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i->next_page_offset = 0;
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i->current_page_index = 0;
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ydb_page_free(i->curr_page);
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i->curr_page = NULL;
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free(i->filename);
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fclose(i->fd);
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// Unset "in use" flag
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instance->in_use = 0;
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return YDB_ERR_SUCCESS;
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}
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YDB_Error ydb_create_table(YDB_Engine *instance, const char *path) {
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THROW_IF_NULL(instance, YDB_ERR_INSTANCE_NOT_INITIALIZED);
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THROW_IF_NULL(!instance->in_use, YDB_ERR_INSTANCE_IN_USE);
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if (access(instance->filename, F_OK) != -1) {
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// TODO: Windows does not check W_OK correctly, use other methods.
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// TODO: if can't read/write, throw other error
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return YDB_ERR_TABLE_EXIST;
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}
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FILE *f = fopen(path, "wb");
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char tpl[] = YDB_TABLE_FILE_SIGN
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"\x00\x01"
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"\x00\x00\x00\x00\x00\x00\x00\x1E"
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"\x00\x00\x00\x00\x00\x00\x00\x1E"
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"\x00\x00\x00\x00\x00\x00\x00\x00";
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fwrite(tpl, sizeof(tpl)-1, 1, f);
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char *first_page = calloc(1, YDB_TABLE_PAGE_SIZE);
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fwrite(first_page, YDB_TABLE_PAGE_SIZE, 1, f);
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free(first_page);
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fclose(f);
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return ydb_load_table(instance, path);
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}
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int64_t ydb_tell_page(YDB_Engine *instance) {
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THROW_IF_NULL(instance, YDB_ERR_INSTANCE_NOT_INITIALIZED);
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THROW_IF_NULL(instance->in_use, YDB_ERR_INSTANCE_NOT_IN_USE);
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return instance->current_page_index;
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}
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YDB_Error ydb_next_page(YDB_Engine *instance) {
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THROW_IF_NULL(instance, YDB_ERR_INSTANCE_NOT_INITIALIZED);
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THROW_IF_NULL(instance->in_use, YDB_ERR_INSTANCE_NOT_IN_USE);
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THROW_IF_NULL(instance->next_page_offset, YDB_ERR_NO_MORE_PAGES);
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instance->prev_page_offset = instance->curr_page_offset;
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instance->curr_page_offset = instance->next_page_offset;
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++(instance->current_page_index);
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return __ydb_read_page(instance);
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}
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YDB_Error ydb_seek_page(YDB_Engine *instance, int64_t index) {
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THROW_IF_NULL(instance, YDB_ERR_INSTANCE_NOT_INITIALIZED);
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THROW_IF_NULL(instance->in_use, YDB_ERR_INSTANCE_NOT_IN_USE);
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if (index < 0) {
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return YDB_ERR_PAGE_INDEX_OUT_OF_RANGE;
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}
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// Save current state
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YDB_Offset prev_page_offset = instance->prev_page_offset;
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YDB_Offset curr_page_offset = instance->curr_page_offset;
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YDB_Offset next_page_offset = instance->next_page_offset;
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int64_t curr_page_index = instance->current_page_index;
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if (index < instance->current_page_index) {
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instance->prev_page_offset = 0;
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instance->curr_page_offset = instance->first_page_offset;
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instance->current_page_index = 0;
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__ydb_read_page(instance);
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}
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while (instance->current_page_index != index) {
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YDB_Error status = ydb_next_page(instance);
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if (status != YDB_ERR_SUCCESS) {
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instance->prev_page_offset = prev_page_offset;
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instance->curr_page_offset = curr_page_offset;
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instance->next_page_offset = next_page_offset;
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instance->current_page_index = curr_page_index;
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__ydb_read_page(instance);
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return status;
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}
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}
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return YDB_ERR_SUCCESS;
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}
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YDB_TablePage* ydb_get_current_page(YDB_Engine *instance) {
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THROW_IF_NULL(instance, NULL);
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THROW_IF_NULL(instance->in_use, NULL);
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return instance->curr_page;
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}
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YDB_Error ydb_append_page(YDB_Engine* instance, YDB_TablePage* page) {
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THROW_IF_NULL(instance, YDB_ERR_INSTANCE_NOT_INITIALIZED);
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THROW_IF_NULL(instance->in_use, YDB_ERR_INSTANCE_NOT_IN_USE);
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YDB_Offset new_page_offset = __ydb_allocate_page_and_seek(instance);
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YDB_PageSize rc = ydb_page_row_count_get(page);
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YDB_Flags f = ydb_page_flags_get(page);
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YDB_Offset next = 0;
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char d[YDB_TABLE_PAGE_SIZE - 11]; // TODO move magic numbers somewhere
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if (ydb_page_data_read(page, d, sizeof(d))) {
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return YDB_ERR_UNKNOWN; // FIXME
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}
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fwrite(&f, sizeof(f), 1, instance->fd);
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fwrite(&next, sizeof(next), 1, instance->fd);
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fwrite(&rc, sizeof(rc), 1, instance->fd);
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fwrite(d, sizeof(d), 1, instance->fd);
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fflush(instance->fd);
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return YDB_ERR_SUCCESS;
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}
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YDB_Error ydb_replace_page(YDB_Engine *instance, YDB_TablePage *page) {
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THROW_IF_NULL(instance, YDB_ERR_INSTANCE_NOT_INITIALIZED);
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THROW_IF_NULL(instance->in_use, YDB_ERR_INSTANCE_NOT_IN_USE);
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THROW_IF_NULL(page, YDB_ERR_PAGE_NOT_INITIALIZED);
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// Seek to current page in file
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fseek(instance->fd, instance->curr_page_offset, SEEK_SET);
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// Write flags
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YDB_Flags page_flags = ydb_page_flags_get(page);
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fwrite(&page_flags, sizeof(YDB_Flags), 1, instance->fd);
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// Skip next page offset
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fseek(instance->fd, sizeof(YDB_Offset), SEEK_CUR);
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// Write row count
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YDB_PageSize row_cnt = ydb_page_row_count_get(page);
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fwrite(&row_cnt, sizeof(row_cnt), 1, instance->fd);
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// Write data
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char page_data[YDB_TABLE_PAGE_SIZE - 11]; // TODO move magic numbers somewhere
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if (ydb_page_data_read(page, page_data, sizeof(page_data))) {
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return YDB_ERR_UNKNOWN; // FIXME
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}
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fwrite(page_data, sizeof(page_data), 1, instance->fd);
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// Flush buffer
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fflush(instance->fd);
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return YDB_ERR_SUCCESS;
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}
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YDB_Error ydb_delete_current_page(YDB_Engine *instance) {
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THROW_IF_NULL(instance, YDB_ERR_INSTANCE_NOT_INITIALIZED);
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THROW_IF_NULL(instance->in_use, YDB_ERR_INSTANCE_NOT_IN_USE);
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// Mark page as deleted
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fseek(instance->fd, instance->curr_page_offset, SEEK_SET);
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fputc(YDB_TABLE_PAGE_FLAG_DELETED, instance->fd);
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// Write last_free_page_offset as the next page for current one
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fwrite(&(instance->last_free_page_offset), sizeof(YDB_Offset), 1, instance->fd);
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// Link the previous page with next one (could be null ptr)
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fseek(instance->fd, instance->prev_page_offset + 1, SEEK_SET); // Skip flags
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fwrite(&(instance->next_page_offset), sizeof(YDB_Offset), 1, instance->fd);
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// If it was the last page, rewrite last_page_offset with prev_page_offset
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if (instance->next_page_offset == 0) {
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fseek(instance->fd, 14, SEEK_SET);
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fwrite(&(instance->prev_page_offset), sizeof(YDB_Offset), 1, instance->fd);
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}
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// Rewrite last_free_page_offset with current offset
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fseek(instance->fd, 22, SEEK_SET);
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fwrite(&(instance->curr_page_offset), sizeof(YDB_Offset), 1, instance->fd);
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// Flush buffer
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fflush(instance->fd);
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return YDB_ERR_SUCCESS;
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}
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