GavinRay97

Build a PostgreSQL Wire Protocol Server in Vanilla JDK 21

• Build a PostgreSQL Wire Protocol Server in Vanilla JDK 21
  • Outline
  • Introduction to the PostgreSQL Wire Protocol
  • Step 1: Doing The Simplest Thing That Could Possibly Work (TM)
    • Step 1.1 - Initial Server Skeleton
      • Connecting to the Server with psql
    • Step 1.2 - Responding to the SSL Negotiation message and the Startup Message
• Step 1.3 - Differentiating between the SSL/Authentication request, and Command messages

GavinRay97

Setting up a Modern C++20/23 Environment

This document describes configuring a development environment for modern C++. Some of the flags and warnings in this document are not common knowledge, or found in the documentation of the respective toolchain.

Compiler

Below is the compiler configuration we'll use

Common Flags

GavinRay97

#include <iostream>

// clang-format off
#include <gcc-plugin.h>
#include <context.h>
#include <plugin-version.h>
#include <tree.h>
#include <gimple.h>
#include <tree-pass.h>
#include <gimple-iterator.h>

GavinRay97

#include <iostream>

// clang-format off
#include <gcc-plugin.h>
#include <context.h>
#include <plugin-version.h>
#include <tree.h>
#include <gimple.h>
#include <tree-pass.h>
#include <gimple-iterator.h>

GavinRay97

digraph state_machine {
  rankdir=LR;
  size="8,5"
  node [shape = doublecircle, style=filled, fillcolor=lightblue]; WaitingForQuery;
  node [shape = doublecircle, style=filled, fillcolor=maroon] GotErrorResponseDuringSimpleQuery;
  node [shape = circle, style=filled, fillcolor=lightgrey];
  InitializingBackend -> GotCommandComplete [ label = "PG3ReadyForQuery", color=green ];
  InitializingBackend -> InitializingBackend [ label = "PG3BackendKeyData", color=orange ];
  GotDataRow -> GotErrorResponseDuringSimpleQuery [ label = "PG3ErrorResponse", color=red ];
  GotDataRow -> GotCommandComplete [ label = "PG3CommandComplete", color=green ];

GavinRay97

{
    "AuthenticationOk": {
        "type": "backend",
        "fields": [
            {
                "name": "Byte1('R')",
                "type": "Byte1",
                "description": "Identifies the message as an authentication request.",
                "value": "'R'"
            },

GavinRay97

// Regex for lines like "Terminate (F)"
// Where the first group is the name of the message and the second is the kind (Backend/Frontend)
const pgMessageTypeRegex = /^(?<command>\w+) \((?<kind>\w)\)$/gm

// Regex for the type of a variable, like:
// - Int16, Int32, Byten, Byte4, String
// - Byte1('S')
// - Int32(4)
// - Int16[N]
// Where:

GavinRay97

import fs from "node:fs"

const postgresWireProtocolDocs = `
AuthenticationOk (B)
Byte1('R')
Identifies the message as an authentication request.

Int32(8)
Length of message contents in bytes, including self.

GavinRay97

// Generated by blah blah blah

public class PostgresTypes {

	public static class Backend {
		public static class AuthenticationOk {
			/** Identifies the message as an authentication request. */
			byte field1_Byte1 = 'R';
			/** Length of message contents in bytes, including self. */
			int field2_Int32 = 8;

GavinRay97

#include <atomic>
#include <cassert>
#include <cstdint>
#include <cstdio>
#include <optional>

// A word-aligned, atomic tagged pointer.
// Uses both the upper 16 bits for storage, and the lower 3 bits for tagging.
//
//   64                48                32                16