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YeltsinDB
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Remove magic numbers from code

master
Yury Kurlykov 2019-11-24 20:30:51 +10:00
parent c26bc18d8d
commit 8d56569dd5
1 changed files with 42 additions and 15 deletions
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57
src/ydb.c
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@ -13,10 +13,6 @@ extern "C" {
#include <YeltsinDB/table_page.h>
#include <YeltsinDB/ydb.h>
/** @todo These things:
* - Page data (current, maybe cache next and prev too)
* - MAYBE query caching
*/
struct __YDB_Engine {
uint8_t ver_major; /**< A major version of loaded table. */
uint8_t ver_minor; /**< A minor version of loaded table. */
@ -37,6 +33,38 @@ struct __YDB_Engine {
FILE *fd; /**< Current table data file descriptor. */
};
struct __data_offsets {
YDB_Offset signature,
ver_major,
ver_minor,
first_page_offset,
last_page_offset,
last_free_page_offset,
meta_end;
};
struct __page_offsets {
YDB_Offset flags,
next_page_offset,
row_count,
meta_end;
};
static const struct __data_offsets v0_offsets = {
.signature = 0,
.ver_major = 4,
.ver_minor = 5,
.first_page_offset = 6,
.last_page_offset = 14,
.last_free_page_offset = 22,
.meta_end = 30
};
static const struct __page_offsets v0_page_offsets = {
.flags = 0,
.next_page_offset = 1,
.row_count = 9,
.meta_end = 11
};
YDB_Engine *ydb_init_instance() {
YDB_Engine *new_instance = calloc(1, sizeof(YDB_Engine));
return new_instance;
@ -66,11 +94,10 @@ static YDB_Error __ydb_read_page(YDB_Engine *inst) {
YDB_Flags page_flags = p_data[0];
YDB_Offset next;
YDB_PageSize row_count;
memcpy(&next, p_data + sizeof(page_flags), sizeof(next));
memcpy(&row_count, p_data + sizeof(page_flags) + sizeof(next), sizeof(row_count));
memcpy(&next, p_data + v0_page_offsets.next_page_offset, sizeof(next));
memcpy(&row_count, p_data + v0_page_offsets.row_count, sizeof(row_count));
//TODO move it to consts. Also page meta size could differ in different major versions.
const YDB_PageSize meta_size = sizeof(page_flags) + sizeof(next) + sizeof(row_count);
const YDB_PageSize meta_size = v0_page_offsets.meta_end;
const YDB_PageSize data_size = YDB_TABLE_PAGE_SIZE - meta_size;
YDB_TablePage *p = ydb_page_alloc(data_size);
@ -97,7 +124,7 @@ static YDB_Offset __ydb_allocate_page_and_seek(YDB_Engine *inst) {
result = ftell(inst->fd);
// Write next page offset in the previous page
fseek(inst->fd, inst->last_page_offset + 1, SEEK_SET); // Skip page flag
fseek(inst->fd, inst->last_page_offset + v0_page_offsets.next_page_offset, SEEK_SET); // Skip page flag
fwrite(&result, sizeof(result), 1, inst->fd);
// Allocate an empty chunk
@ -108,7 +135,7 @@ static YDB_Offset __ydb_allocate_page_and_seek(YDB_Engine *inst) {
// Write last page offset
inst->last_page_offset = result;
fseek(inst->fd, 14, SEEK_SET); // TODO move magic offsets somewhere
fseek(inst->fd, v0_offsets.last_page_offset, SEEK_SET);
fwrite(&inst->last_page_offset, sizeof(YDB_Offset), 1, inst->fd);
fflush(inst->fd);
} else {
@ -116,7 +143,7 @@ static YDB_Offset __ydb_allocate_page_and_seek(YDB_Engine *inst) {
result = inst->last_free_page_offset;
// Read last free page offset after allocation
fseek(inst->fd, result + 1, SEEK_SET); // Skip flag
fseek(inst->fd, result + v0_page_offsets.next_page_offset, SEEK_SET); // Skip flag
fread(&(inst->last_free_page_offset), sizeof(YDB_Offset), 1, inst->fd);
fseek(inst->fd, -(long)(sizeof(YDB_Offset) + 1), SEEK_CUR);
@ -127,7 +154,7 @@ static YDB_Offset __ydb_allocate_page_and_seek(YDB_Engine *inst) {
fwrite(page_header, sizeof(page_header)-1, 1, inst->fd);
// Write last free page offset after allocation in file
fseek(inst->fd, 22, SEEK_SET); // Skip unneeded data TODO beautify it
fseek(inst->fd, v0_offsets.last_free_page_offset, SEEK_SET);
fwrite(&(inst->last_free_page_offset), sizeof(YDB_Offset), 1, inst->fd);
}
fflush(inst->fd);
@ -306,12 +333,12 @@ YDB_Error ydb_append_page(YDB_Engine* instance, YDB_TablePage* page) {
THROW_IF_NULL(instance, YDB_ERR_INSTANCE_NOT_INITIALIZED);
THROW_IF_NULL(instance->in_use, YDB_ERR_INSTANCE_NOT_IN_USE);
YDB_Offset new_page_offset = __ydb_allocate_page_and_seek(instance);
__ydb_allocate_page_and_seek(instance);
YDB_PageSize rc = ydb_page_row_count_get(page);
YDB_Flags f = ydb_page_flags_get(page);
YDB_Offset next = 0;
char d[YDB_TABLE_PAGE_SIZE - 11]; // TODO move magic numbers somewhere
char d[YDB_TABLE_PAGE_SIZE - v0_page_offsets.meta_end];
ydb_page_data_seek(page, 0);
if (ydb_page_data_read(page, d, sizeof(d))) {
return YDB_ERR_UNKNOWN; // FIXME
@ -353,7 +380,7 @@ YDB_Error ydb_replace_current_page(YDB_Engine *instance, YDB_TablePage *page) {
fwrite(&row_cnt, sizeof(row_cnt), 1, instance->fd);
// Write data
char page_data[YDB_TABLE_PAGE_SIZE - 11]; // TODO move magic numbers somewhere
char page_data[YDB_TABLE_PAGE_SIZE - v0_page_offsets.meta_end];
ydb_page_data_seek(page, 0);
if (ydb_page_data_read(page, page_data, sizeof(page_data))) {
return YDB_ERR_UNKNOWN; // FIXME