fixed unprepared result set parsing (crystal-lang#37)

Fixes crystal-lang#36

spec/db_spec.cr

@@ -176,4 +176,24 @@ DB::DriverSpecs(MySql::Any).run do
       fail("Expected no exception, but got \"#{e.message}\"")
     end
   end
+
+  it "allows unprepared statement queries" do |db|
+    db.exec %(create table if not exists a (i int not null, str text not null);)
+    db.exec %(insert into a (i, str) values (23, "bai bai");)
+
+    2.times do |i|
+      DB.open db.uri do |db|
+        begin
+          db.unprepared.query("SELECT i, str FROM a WHERE i = 23") do |rs|
+            rs.each do
+              rs.read(Int32).should eq 23
+              rs.read(String).should eq "bai bai"
+            end
+          end
+        rescue e
+          fail("Expected no exception, but got \"#{e.message}\"")
+        end
+      end
+    end
+  end
 end

src/mysql/text_result_set.cr

@@ -5,7 +5,7 @@ class MySql::TextResultSet < DB::ResultSet
 
   @conn : MySql::Connection
   @row_packet : MySql::ReadPacket?
-  @header : UInt8
+  @first_byte : UInt8
 
   def initialize(statement, column_count)
     super(statement)
@@ -16,8 +16,9 @@ class MySql::TextResultSet < DB::ResultSet
 
     @column_index = 0 # next column index to return
 
-    @header = 0u8
+    @first_byte = 0u8
     @eof_reached = false
+    @first_row_packet = false
   end
 
   def do_close
@@ -41,13 +42,14 @@ class MySql::TextResultSet < DB::ResultSet
 
     @row_packet = row_packet = @conn.build_read_packet
 
-    @header = row_packet.read_byte!
-    if @header == 0xfe # EOF
+    @first_byte = row_packet.read_byte!
+    if @first_byte == 0xfe # EOF
       @eof_reached = true
       return false
     end
 
     @column_index = 0
+    @first_row_packet = true
     # TODO remove row_packet.read(@null_bitmap_slice)
     return true
   end
@@ -63,13 +65,20 @@ class MySql::TextResultSet < DB::ResultSet
   def read
     row_packet = @row_packet.not_nil!
 
-    is_nil = @header == 0xfb
+    if @first_row_packet
+      current_byte = @first_byte
+      @first_row_packet = false
+    else
+      current_byte = row_packet.read_byte!
+    end
+
+    is_nil = current_byte == 0xfb
     col = @column_index
     @column_index += 1
     if is_nil
       nil
     else
-      length = row_packet.read_lenenc_int(@header)
+      length = row_packet.read_lenenc_int(current_byte)
       val = row_packet.read_string(length)
       val = @columns[col].column_type.parse(val)