Explain BufferedReader situation vlang/v#21975

Author: Coachonko

src/protocol.v

@@ -4,24 +4,36 @@ import arrays
 import os
 import io
 import math.big
-import crypto.cipher
+// import crypto.cipher
 import x.crypto.chacha20
 import crypto.sha256
 import net
 
-const plugin_list = 'Srp256,Srp' // LegacyAuth not supported
+const plugin_list = 'Srp256,Srp'
 const buffer_len = 1024
 const max_char_length = 32767
 const blob_segment_size = 32000
 
+const low_priority_todo = 'https://github.com/Coachonko/firebird/blob/pending/TODO.md#low-priority'
+const legacy_auth_error = 'LegacyAuth is not supported: ${low_priority_todo}'
+const arc4_error = 'Arc4 wire encryption plugin is not supported: ${low_priority_todo}'
+
 struct WireChannel {
 mut:
 	conn   net.TcpConn
 	reader &io.BufferedReader
+	// The firebird protocol expects that we are in control of when the writing is flushed.
+	// In some situations it is required that flushing is deferred.
+	// io.BufferedWriter doesn't exist
+	// https://github.com/vlang/v/issues/21975
 	// writer         &io.BufferedWriter
-	plugin        string
-	crypto_reader &cipher.Stream
-	crypto_writer &cipher.Stream
+	plugin string
+	// crypto_reader and crypto_writer should implement cipher.Stream
+	// This allows to use any supported stream cipher
+	// chacha20.Cipher and rc4.Cipher implement the cipher.Stream interface wrong.
+	// https://github.com/vlang/v/issues/21973
+	crypto_reader &chacha20.Cipher // &cipher.Stream
+	crypto_writer &chacha20.Cipher // &cipher.Stream
 }
 
 fn new_wire_channel(conn net.TcpConn) &WireChannel {
@@ -39,18 +51,105 @@ fn new_wire_channel(conn net.TcpConn) &WireChannel {
 
 fn (mut c WireChannel) set_crypt_key(plugin string, session_key []u8, nonce []u8) ! {
 	c.plugin = plugin
+	if plugin == 'Arc4' {
+		return error(firebird.arc4_error)
+	}
+
 	if plugin == 'ChaCha' {
 		mut digest := sha256.new()
 		digest.write(session_key)!
 		key := digest.sum([]u8{})
-		c.crypto_reader = chacha20.new_cipher(key, nonce)! // https://github.com/vlang/v/issues/21973
+		c.crypto_reader = chacha20.new_cipher(key, nonce)!
 		c.crypto_writer = chacha20.new_cipher(key, nonce)!
-	} else if plugin == 'Arc4' {
-		return error('Arc4 wire encryption plugin is not supported: https://github.com/Coachonko/firebird/blob/pending/TODO.md#low-priority')
-	} else {
-		return error('Unknown wire encryption plugin name: ${plugin}')
 	}
-	return
+
+	return error('Unknown wire encryption plugin name: ${plugin}')
+}
+
+fn (mut c WireChannel) read(mut buf []u8) !int {
+	if c.plugin != '' {
+		mut src := []u8{}
+		n := c.reader.read(mut src)!
+		if c.plugin == 'Arc4' {
+			return error(firebird.arc4_error)
+		}
+
+		if c.plugin == 'ChaCha' {
+			c.crypto_reader.xor_key_stream(mut buf, src[0..n])
+		}
+
+		return n
+	}
+
+	return c.reader.read(mut buf)
+}
+
+fn (mut c WireChannel) write(buf []u8) !int {
+	return c.conn.write(buf)!
+}
+
+// fn (mut c WireChannel) write(buf []u8) !int {
+// 	if c.plugin != '' {
+// 		mut dst := []u8{}
+// 		if c.plugin == 'Arc4' {
+// 			return error(firebird.arc4_error)
+// 		}
+
+// 		if c.plugin == 'ChaCha' {
+// 			c.crypto_writer.xor_key_stream(mut dst, buf)
+// 		}
+
+// 		mut written := 0
+// 		for written < buf.len {
+// 			written += c.writer.write(dst[written..])!
+// 		}
+// 		return written
+// 	}
+
+// 	return c.writer.write(mut buf)
+// }
+
+// fn (mut c WireChannel) flush() ! {
+// 	c.writer.flush()!
+// }
+
+fn (mut c WireChannel) close() ! {
+	c.conn.close()!
+}
+
+struct WireProtocol {
+	buf []u8
+
+	conn      WireChannel
+	db_handle i32
+	addr      string
+
+	protocol_version    i32
+	accept_architecture i32
+	accept_type         i32
+	lazy_response_count int
+
+	plugin_name string
+	user        string
+	password    string
+	auth_data   []u8
+
+	charset          string
+	charset_byte_len int
+
+	timezone string
+}
+
+fn new_wire_protocol(addr string, timezone string) !&WireProtocol {
+	conn := net.dial_tcp(addr)!
+	return &WireProtocol{
+		buf: []u8{}
+		conn: new_wire_channel(conn)
+		addr: addr
+		charset: 'UTF8'
+		charset_byte_len: 4
+		timezone: timezone
+	}
 }
 
 fn user_identification(user string, auth_plugin_name string, wire_crypt bool, client_public big.Integer) []u8 {
@@ -94,7 +193,7 @@ fn user_identification(user string, auth_plugin_name string, wire_crypt bool, cl
 		}
 
 		if auth_plugin_name == 'Legacy_Auth' {
-			panic('Unsupported plugin: ${auth_plugin_name}')
+			panic(firebird.legacy_auth_error)
 		}
 		panic('Unknown plugin name: ${auth_plugin_name}')
 	}