Add DataRowReader and change Connection.SelectFunc to use it

Preparatory step for structure binding. refs #11

data_row_reader.go

@@ -0,0 +1,97 @@
+package pgx
+
+import (
+	"strconv"
+)
+
+type DataRowReader struct {
+	mr     *MessageReader
+	fields []FieldDescription
+}
+
+func newDataRowReader(mr *MessageReader, fields []FieldDescription) (r *DataRowReader) {
+	r = new(DataRowReader)
+	r.mr = mr
+	r.fields = fields
+
+	fieldCount := int(mr.ReadInt16())
+	if fieldCount != len(fields) {
+		panic("Row description field count and data row field count do not match")
+	}
+
+	return
+}
+
+func (r *DataRowReader) ReadString() string {
+	size := r.mr.ReadInt32()
+	if size == -1 {
+		panic("Unexpected null")
+	}
+
+	return r.mr.ReadByteString(size)
+}
+
+func (r *DataRowReader) ReadInt64() int64 {
+	size := r.mr.ReadInt32()
+	if size == -1 {
+		panic("Unexpected null")
+	}
+
+	i64, err := strconv.ParseInt(r.mr.ReadByteString(size), 10, 64)
+	if err != nil {
+		panic("Number too large")
+	}
+	return i64
+}
+
+func (r *DataRowReader) ReadInt32() int32 {
+	size := r.mr.ReadInt32()
+	if size == -1 {
+		panic("Unexpected null")
+	}
+
+	i64, err := strconv.ParseInt(r.mr.ReadByteString(size), 10, 32)
+	if err != nil {
+		panic("Number too large")
+	}
+	return int32(i64)
+}
+
+func (r *DataRowReader) ReadInt16() int16 {
+	size := r.mr.ReadInt32()
+	if size == -1 {
+		panic("Unexpected null")
+	}
+
+	i64, err := strconv.ParseInt(r.mr.ReadByteString(size), 10, 16)
+	if err != nil {
+		panic("Number too large")
+	}
+	return int16(i64)
+}
+
+func (r *DataRowReader) ReadFloat64() float64 {
+	size := r.mr.ReadInt32()
+	if size == -1 {
+		panic("Unexpected null")
+	}
+
+	f64, err := strconv.ParseFloat(r.mr.ReadByteString(size), 64)
+	if err != nil {
+		panic("Number too large")
+	}
+	return f64
+}
+
+func (r *DataRowReader) ReadFloat32() float32 {
+	size := r.mr.ReadInt32()
+	if size == -1 {
+		panic("Unexpected null")
+	}
+
+	f64, err := strconv.ParseFloat(r.mr.ReadByteString(size), 32)
+	if err != nil {
+		panic("Number too large")
+	}
+	return float32(f64)
+}