Reduce nesting in message loops

conn.go

@@ -211,7 +211,11 @@ func Connect(config ConnConfig) (c *Conn, err error) {
 	for {
 		var t byte
 		var r *MessageReader
-		if t, r, err = c.rxMsg(); err == nil {
+		t, r, err = c.rxMsg()
+		if err != nil {
+			return nil, err
+		}
+
 		switch t {
 		case backendKeyData:
 			c.rxBackendKeyData(r)
@@ -229,9 +233,6 @@ func Connect(config ConnConfig) (c *Conn, err error) {
 				return nil, err
 			}
 		}
-		} else {
-			return nil, err
-		}
 	}
 }
 
@@ -305,32 +306,37 @@ func (c *Conn) selectFunc(sql string, onDataRow func(*DataRowReader) error, argu
 		return
 	}
 
+	var softErr error
+
 	for {
-		if t, r, rxErr := c.rxMsg(); rxErr == nil {
+		var t byte
+		var r *MessageReader
+		t, r, err = c.rxMsg()
+		if err != nil {
+			return err
+		}
+
 		switch t {
 		case readyForQuery:
 			c.rxReadyForQuery(r)
-				return
+			return softErr
 		case rowDescription:
 			fields = c.rxRowDescription(r)
 		case dataRow:
-				if err == nil {
+			if softErr == nil {
 				var drr *DataRowReader
-					drr, err = newDataRowReader(r, fields)
+				drr, softErr = newDataRowReader(r, fields)
-					if err == nil {
+				if softErr == nil {
-						err = onDataRow(drr)
+					softErr = onDataRow(drr)
 				}
 			}
 		case commandComplete:
 		case bindComplete:
 		default:
-				if e := c.processContextFreeMsg(t, r); e != nil && err == nil {
+			if e := c.processContextFreeMsg(t, r); e != nil && softErr == nil {
-					err = e
+				softErr = e
 			}
 		}
-		} else {
-			return rxErr
-		}
 	}
 }
 
@@ -456,44 +462,50 @@ func (c *Conn) SelectValueTo(w io.Writer, sql string, arguments ...interface{})
 	}
 
 	var numRowsFound int64
+	var softErr error
 
 	for {
-		if t, bodySize, rxErr := c.rxMsgHeader(); rxErr == nil {
+		var t byte
+		var bodySize int32
+
+		t, bodySize, err = c.rxMsgHeader()
+		if err != nil {
+			return err
+		}
+
 		if t == dataRow {
 			numRowsFound++
 
 			if numRowsFound > 1 {
-					err = NotSingleRowError{RowCount: numRowsFound}
+				softErr = NotSingleRowError{RowCount: numRowsFound}
 			}
 
-				if err != nil {
+			if softErr != nil {
 				c.rxMsgBody(bodySize) // Read and discard rest of message
 				continue
 			}
 
-				err = c.rxDataRowValueTo(w, bodySize)
+			softErr = c.rxDataRowValueTo(w, bodySize)
 		} else {
 			var body *bytes.Buffer
-				if body, rxErr = c.rxMsgBody(bodySize); rxErr == nil {
+			body, err = c.rxMsgBody(bodySize)
+			if err != nil {
+				return err
+			}
+
 			r := newMessageReader(body)
 			switch t {
 			case readyForQuery:
 				c.rxReadyForQuery(r)
-						return
+				return softErr
 			case rowDescription:
 			case commandComplete:
 			case bindComplete:
 			default:
-						if e := c.processContextFreeMsg(t, r); e != nil && err == nil {
+				if e := c.processContextFreeMsg(t, r); e != nil && softErr == nil {
-							err = e
+					softErr = e
 				}
 			}
-				} else {
-					return rxErr
-				}
-			}
-		} else {
-			return rxErr
 		}
 	}
 }
@@ -610,8 +622,16 @@ func (c *Conn) Prepare(name, sql string) (err error) {
 
 	ps := preparedStatement{Name: name}
 
+	var softErr error
+
 	for {
-		if t, r, rxErr := c.rxMsg(); rxErr == nil {
+		var t byte
+		var r *MessageReader
+		t, r, err := c.rxMsg()
+		if err != nil {
+			return err
+		}
+
 		switch t {
 		case parseComplete:
 		case parameterDescription:
@@ -628,15 +648,12 @@ func (c *Conn) Prepare(name, sql string) (err error) {
 		case readyForQuery:
 			c.rxReadyForQuery(r)
 			c.preparedStatements[name] = &ps
-				return
+			return softErr
 		default:
-				if e := c.processContextFreeMsg(t, r); e != nil && err == nil {
+			if e := c.processContextFreeMsg(t, r); e != nil && softErr == nil {
-					err = e
+				softErr = e
 			}
 		}
-		} else {
-			return rxErr
-		}
 	}
 }
 
@@ -844,25 +861,30 @@ func (c *Conn) Execute(sql string, arguments ...interface{}) (commandTag Command
 		return
 	}
 
+	var softErr error
+
 	for {
-		if t, r, rxErr := c.rxMsg(); rxErr == nil {
+		var t byte
+		var r *MessageReader
+		t, r, err = c.rxMsg()
+		if err != nil {
+			return commandTag, err
+		}
+
 		switch t {
 		case readyForQuery:
 			c.rxReadyForQuery(r)
-				return
+			return commandTag, softErr
 		case rowDescription:
 		case dataRow:
 		case bindComplete:
 		case commandComplete:
 			commandTag = CommandTag(r.ReadCString())
 		default:
-				if e := c.processContextFreeMsg(t, r); e != nil && err == nil {
+			if e := c.processContextFreeMsg(t, r); e != nil && softErr == nil {
-					err = e
+				softErr = e
 			}
 		}
-		} else {
-			return "", rxErr
-		}
 	}
 }