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const std = @import("std");
const varint = @import("varint.zig");
const record = @import("record.zig");
/// Get the rootpage number for a table by name
pub fn getRootpage(allocator: std.mem.Allocator, file: *std.fs.File, page_size: u16, table_name: []const u8) !u32 {
var buf: [2]u8 = undefined;
_ = try file.seekTo(103);
_ = try file.read(&buf);
const num_cells = std.mem.readInt(u16, &buf, .big);
var cell_pointers = try allocator.alloc(u16, num_cells);
defer allocator.free(cell_pointers);
for (0..num_cells) |i| {
_ = try file.seekTo(108 + i * 2);
_ = try file.read(&buf);
cell_pointers[i] = std.mem.readInt(u16, &buf, .big);
}
var page_data = try allocator.alloc(u8, page_size);
defer allocator.free(page_data);
_ = try file.seekTo(0);
_ = try file.read(page_data);
for (0..num_cells) |i| {
if (cell_pointers[i] >= page_data.len) continue;
const cell_data = page_data[cell_pointers[i]..];
var parsed = varint.parse(cell_data);
var pos = parsed.len;
if (pos >= cell_data.len) continue;
parsed = varint.parse(cell_data[pos..]);
pos += parsed.len;
if (pos >= cell_data.len) continue;
const record_data = cell_data[pos..];
parsed = varint.parse(record_data);
const header_size = parsed.value;
if (header_size > record_data.len) continue;
var header_pos = parsed.len;
var serial_types: [5]u64 = undefined;
for (0..5) |col| {
if (header_pos >= header_size) break;
parsed = varint.parse(record_data[header_pos..]);
serial_types[col] = parsed.value;
header_pos += parsed.len;
}
const type_st = serial_types[0];
const name_st = serial_types[1];
const rootpage_st = serial_types[3];
var body_pos: usize = header_size;
const type_result = record.readString(record_data[body_pos..], type_st);
if (!std.mem.eql(u8, type_result.value, "table")) continue;
body_pos += type_result.len;
const name_result = record.readString(record_data[body_pos..], name_st);
if (!std.mem.eql(u8, name_result.value, table_name)) continue;
body_pos += name_result.len;
body_pos += (serial_types[2] - 13) / 2;
const rootpage_result = record.readInt(record_data[body_pos..], rootpage_st);
return @as(u32, @intCast(rootpage_result.value));
}
return error.TableNotFound;
}
/// Get CREATE TABLE SQL for a table
pub fn getCreateTableSQL(allocator: std.mem.Allocator, file: *std.fs.File, page_size: u16, table_name: []const u8) ![]const u8 {
var buf: [2]u8 = undefined;
_ = try file.seekTo(103);
_ = try file.read(&buf);
const num_cells = std.mem.readInt(u16, &buf, .big);
var cell_pointers = try allocator.alloc(u16, num_cells);
defer allocator.free(cell_pointers);
for (0..num_cells) |i| {
_ = try file.seekTo(108 + i * 2);
_ = try file.read(&buf);
cell_pointers[i] = std.mem.readInt(u16, &buf, .big);
}
var page_data = try allocator.alloc(u8, page_size);
defer allocator.free(page_data);
_ = try file.seekTo(0);
_ = try file.read(page_data);
for (0..num_cells) |i| {
if (cell_pointers[i] >= page_data.len) continue;
const cell_data = page_data[cell_pointers[i]..];
var parsed = varint.parse(cell_data);
var pos = parsed.len;
if (pos >= cell_data.len) continue;
parsed = varint.parse(cell_data[pos..]);
pos += parsed.len;
if (pos >= cell_data.len) continue;
const record_data = cell_data[pos..];
parsed = varint.parse(record_data);
const header_size = parsed.value;
if (header_size > record_data.len) continue;
var header_pos = parsed.len;
var serial_types: [5]u64 = undefined;
for (0..5) |col| {
if (header_pos >= header_size) break;
parsed = varint.parse(record_data[header_pos..]);
serial_types[col] = parsed.value;
header_pos += parsed.len;
}
const type_st = serial_types[0];
const name_st = serial_types[1];
const sql_st = serial_types[4];
var body_pos: usize = header_size;
const type_result = record.readString(record_data[body_pos..], type_st);
if (!std.mem.eql(u8, type_result.value, "table")) continue;
body_pos += type_result.len;
const name_result = record.readString(record_data[body_pos..], name_st);
if (!std.mem.eql(u8, name_result.value, table_name)) continue;
body_pos += name_result.len;
body_pos += (serial_types[2] - 13) / 2;
const rootpage_result = record.readInt(record_data[body_pos..], serial_types[3]);
body_pos += rootpage_result.len;
const sql_result = record.readString(record_data[body_pos..], sql_st);
return try allocator.dupe(u8, sql_result.value);
}
return error.TableNotFound;
}
/// Parse column index from CREATE TABLE SQL
pub fn parseColumnIndex(sql: []const u8, column_name: []const u8) !usize {
var in_parens = false;
var paren_start: usize = 0;
for (sql, 0..) |c, i| {
if (c == '(') {
if (!in_parens) {
paren_start = i + 1;
in_parens = true;
}
} else if (c == ')') {
if (in_parens) {
const columns_part = sql[paren_start..i];
var column_idx: usize = 0;
var start: usize = 0;
var in_col = false;
for (columns_part, 0..) |ch, j| {
if (!in_col) {
if (ch != ' ' and ch != '\t' and ch != '\n' and ch != '\r') {
start = j;
in_col = true;
}
} else {
if (ch == ',' or j == columns_part.len - 1) {
var end = j;
if (j == columns_part.len - 1 and ch != ',') {
end = j + 1;
}
const col_def = columns_part[start..end];
var space_idx: usize = 0;
for (col_def, 0..) |col_ch, col_i| {
if (col_ch == ' ' or col_ch == '\t') {
space_idx = col_i;
break;
}
}
const col_name = if (space_idx > 0) col_def[0..space_idx] else col_def;
if (std.mem.eql(u8, col_name, column_name)) {
return column_idx;
}
column_idx += 1;
in_col = false;
}
}
}
}
}
}
return error.ColumnNotFound;
}
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