Started with database connection

app/node_modules/mysql2/lib/commands/prepare.js

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+'use strict';
+
+const Packets = require('../packets/index.js');
+const Command = require('./command.js');
+const CloseStatement = require('./close_statement.js');
+const Execute = require('./execute.js');
+
+class PreparedStatementInfo {
+  constructor(query, id, columns, parameters, connection) {
+    this.query = query;
+    this.id = id;
+    this.columns = columns;
+    this.parameters = parameters;
+    this.rowParser = null;
+    this._connection = connection;
+  }
+
+  close() {
+    return this._connection.addCommand(new CloseStatement(this.id));
+  }
+
+  execute(parameters, callback) {
+    if (typeof parameters === 'function') {
+      callback = parameters;
+      parameters = [];
+    }
+    return this._connection.addCommand(
+      new Execute({ statement: this, values: parameters }, callback)
+    );
+  }
+}
+
+class Prepare extends Command {
+  constructor(options, callback) {
+    super();
+    this.query = options.sql;
+    this.onResult = callback;
+    this.id = 0;
+    this.fieldCount = 0;
+    this.parameterCount = 0;
+    this.fields = [];
+    this.parameterDefinitions = [];
+    this.options = options;
+  }
+
+  start(packet, connection) {
+    const Connection = connection.constructor;
+    this.key = Connection.statementKey(this.options);
+    const statement = connection._statements.get(this.key);
+    if (statement) {
+      if (this.onResult) {
+        this.onResult(null, statement);
+      }
+      return null;
+    }
+    const cmdPacket = new Packets.PrepareStatement(
+      this.query,
+      connection.config.charsetNumber,
+      this.options.values
+    );
+    connection.writePacket(cmdPacket.toPacket(1));
+    return Prepare.prototype.prepareHeader;
+  }
+
+  prepareHeader(packet, connection) {
+    const header = new Packets.PreparedStatementHeader(packet);
+    this.id = header.id;
+    this.fieldCount = header.fieldCount;
+    this.parameterCount = header.parameterCount;
+    if (this.parameterCount > 0) {
+      return Prepare.prototype.readParameter;
+    } if (this.fieldCount > 0) {
+      return Prepare.prototype.readField;
+    } 
+    return this.prepareDone(connection);
+  }
+
+  readParameter(packet, connection) {
+    // there might be scenarios when mysql server reports more parameters than
+    // are actually present in the array of parameter definitions.
+    // if EOF packet is received we switch to "read fields" state if there are
+    // any fields reported by the server, otherwise we finish the command.
+    if (packet.isEOF()) {
+      if (this.fieldCount > 0) {
+        return Prepare.prototype.readField;
+      }
+      return this.prepareDone(connection);
+    }
+    const def = new Packets.ColumnDefinition(packet, connection.clientEncoding);
+    this.parameterDefinitions.push(def);
+    if (this.parameterDefinitions.length === this.parameterCount) {
+      return Prepare.prototype.parametersEOF;
+    }
+    return this.readParameter;
+  }
+
+  readField(packet, connection) {
+    if (packet.isEOF()) {
+      return this.prepareDone(connection);
+    }
+    const def = new Packets.ColumnDefinition(packet, connection.clientEncoding);
+    this.fields.push(def);
+    if (this.fields.length === this.fieldCount) {
+      return Prepare.prototype.fieldsEOF;
+    }
+    return Prepare.prototype.readField;
+  }
+
+  parametersEOF(packet, connection) {
+    if (!packet.isEOF()) {
+      return connection.protocolError('Expected EOF packet after parameters');
+    }
+    if (this.fieldCount > 0) {
+      return Prepare.prototype.readField;
+    } 
+    return this.prepareDone(connection);
+    
+  }
+
+  fieldsEOF(packet, connection) {
+    if (!packet.isEOF()) {
+      return connection.protocolError('Expected EOF packet after fields');
+    }
+    return this.prepareDone(connection);
+  }
+
+  prepareDone(connection) {
+    const statement = new PreparedStatementInfo(
+      this.query,
+      this.id,
+      this.fields,
+      this.parameterDefinitions,
+      connection
+    );
+    connection._statements.set(this.key, statement);
+    if (this.onResult) {
+      this.onResult(null, statement);
+    }
+    return null;
+  }
+}
+
+module.exports = Prepare;