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Improve the performance of Go generated marshaling/encoding code (#65)
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@leighmcculloch
leighmcculloch authored Nov 6, 2021
1 parent f04dc8f commit 92a28e1
Showing 1 changed file with 222 additions and 6 deletions.
228 changes: 222 additions & 6 deletions lib/xdrgen/generators/go.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -16,8 +16,20 @@ def generate
private

def render_typedef(out, typedef)
out.puts "type #{name typedef} #{reference typedef.declaration.type}"

# Typedefs that wrap a pointer type are not well supported in Go because
# Go does not allow pointer types to have methods. This prevents us from
# defining the EncodeTo method on these types which is very inconvenient
# for the render functions that generate structs that contain these
# types, because xdrgen doesn't know in that moment they are a type
# without EncodeTo. Since this type cannot have its own methods, we make
# it a type alias so at least it inherits the EncodeTo method from the
# aliased type. This is a bit of a hack, and the hack will only work as
# long as the aliased type is another defined type that has an EncodeTo.
if typedef.sub_type == :optional
out.puts "type #{name typedef} = #{reference typedef.declaration.type}"
else
out.puts "type #{name typedef} #{reference typedef.declaration.type}"
end

# write sizing restrictions
case typedef.declaration
Expand Down Expand Up @@ -165,19 +177,28 @@ def render_definition(out, defn)
case defn
when AST::Definitions::Struct ;
render_struct out, defn
render_struct_encode_to_interface out, defn
render_binary_interface out, name(defn)
render_xdr_type_interface out, name(defn)
when AST::Definitions::Enum ;
render_enum out, defn
render_enum_encode_to_interface out, defn
render_binary_interface out, name(defn)
render_xdr_type_interface out, name(defn)
when AST::Definitions::Union ;
render_union out, defn
render_union_encode_to_interface out, defn
render_binary_interface out, name(defn)
render_xdr_type_interface out, name(defn)
when AST::Definitions::Typedef ;
render_typedef out, defn
# TODO: Support defining binary interface on typedefs with optional
# types. https://github.com/stellar/xdrgen/issues/61
# Typedefs that wrap a pointer type are not supported in Go because Go
# does not allow pointer types to have methods. Don't define methods
# for the type because that will be a Go compiler error.
if defn.sub_type != :optional
render_typedef_encode_to_interface out, defn
render_binary_interface out, name(defn)
render_xdr_type_interface out, name(defn)
end
when AST::Definitions::Const ;
render_const out, defn
Expand Down Expand Up @@ -315,11 +336,73 @@ def render_union(out, union)
out.break
end

def render_struct_encode_to_interface(out, struct)
name = name(struct)
out.puts "// EncodeTo encodes this value using the Encoder."
out.puts "func (s *#{name}) EncodeTo(e *xdr.Encoder) error {"
out.puts " var err error"
struct.members.each do |m|
mn = name(m)
render_encode_to_body(out, "s.#{mn}", m.type, self_encode: false)
end
out.puts " return nil"
out.puts "}"
out.break
end

def render_union_encode_to_interface(out, union)
name = name(union)
out.puts "// EncodeTo encodes this value using the Encoder."
out.puts "func (s #{name}) EncodeTo(e *xdr.Encoder) error {"
out.puts " _, err := e.EncodeInt(int32(s.#{name(union.discriminant)}))"
out.puts " if err != nil {"
out.puts " return err"
out.puts " }"
switch_for(out, union, "s.#{name(union.discriminant)}") do |arm, kase|
out2 = StringIO.new
if arm.void?
"// Void"
else
mn = name(arm)
render_encode_to_body(out2, "(*s.#{mn})", arm.type, self_encode: false)
out2.string
end
end
out.puts " return err"
out.puts "}"
out.break
end

def render_enum_encode_to_interface(out, typedef)
name = name(typedef)
type = typedef
out.puts "// EncodeTo encodes this value using the Encoder."
out.puts "func (s #{name}) EncodeTo(e *xdr.Encoder) error {"
out.puts " var err error"
render_encode_to_body(out, "s", type, self_encode: true)
out.puts " return nil"
out.puts "}"
out.break
end

def render_typedef_encode_to_interface(out, typedef)
name = name(typedef)
type = typedef.declaration.type
out.puts "// EncodeTo encodes this value using the Encoder."
out.puts "func (s #{name}) EncodeTo(e *xdr.Encoder) error {"
out.puts " var err error"
render_encode_to_body(out, "s", type, self_encode: true)
out.puts " return nil"
out.puts "}"
out.break
end

def render_binary_interface(out, name)
out.puts "// MarshalBinary implements encoding.BinaryMarshaler."
out.puts "func (s #{name}) MarshalBinary() ([]byte, error) {"
out.puts " b := new(bytes.Buffer)"
out.puts " _, err := Marshal(b, s)"
out.puts " b := bytes.Buffer{}"
out.puts " e := xdr.NewEncoder(&b)"
out.puts " err := s.EncodeTo(e)"
out.puts " return b.Bytes(), err"
out.puts "}"
out.break
Expand All @@ -336,6 +419,126 @@ def render_binary_interface(out, name)
out.break
end

# render_encode_to_body assumes there is an `e` variable containing an
# xdr.Encoder, and a variable defined by `name` that is the value to
# encode.
def render_encode_to_body(out, var, type, self_encode:)
optional = type.sub_type == :optional
if optional
out.puts " _, err = e.EncodeBool(#{var} != nil)"
out.puts " if err != nil {"
out.puts " return err"
out.puts " }"
out.puts " if #{var} != nil {"
var = "(*#{var})"
end
case type
when AST::Typespecs::UnsignedHyper
out.puts " _, err = e.EncodeUhyper(uint64(#{var}))"
when AST::Typespecs::Hyper
out.puts " _, err = e.EncodeHyper(int64(#{var}))"
when AST::Typespecs::UnsignedInt
out.puts " _, err = e.EncodeUint(uint32(#{var}))"
when AST::Typespecs::Int, AST::Definitions::Enum
out.puts " _, err = e.EncodeInt(int32(#{var}))"
when AST::Typespecs::String
out.puts " _, err = e.EncodeString(string(#{var}))"
when AST::Typespecs::Opaque
if type.fixed?
out.puts " _, err = e.EncodeFixedOpaque(#{var}[:])"
else
out.puts " _, err = e.EncodeOpaque(#{var}[:])"
end
when AST::Typespecs::Simple
case type.sub_type
when :simple, :optional
optional_within = type.is_a?(AST::Identifier) && type.resolved_type.sub_type == :optional
if optional_within
out.puts " _, err = e.EncodeBool(#{var} != nil)"
out.puts " if err != nil {"
out.puts " return err"
out.puts " }"
out.puts " if #{var} != nil {"
var = "(*#{var})"
end
var = "#{name type}(#{var})" if self_encode
out.puts " err = #{var}.EncodeTo(e)"
if optional_within
out.puts " }"
end
when :array
out.puts " for i := 0; i < len(#{var}); i++ {"
element_var = "#{var}[i]"
optional_within = type.is_a?(AST::Identifier) && type.resolved_type.sub_type == :optional
if optional_within
out.puts " _, err = e.EncodeBool(#{element_var} != nil)"
out.puts " if err != nil {"
out.puts " return err"
out.puts " }"
out.puts " if #{element_var} != nil {"
var = "(*#{element_var})"
end
out.puts " err = #{element_var}.EncodeTo(e)"
out.puts " if err != nil {"
out.puts " return err"
out.puts " }"
if optional_within
out.puts " }"
end
out.puts " }"
when :var_array
out.puts " _, err = e.EncodeUint(uint32(len(#{var})))"
out.puts " if err != nil {"
out.puts " return err"
out.puts " }"
out.puts " for i := 0; i < len(#{var}); i++ {"
element_var = "#{var}[i]"
optional_within = type.is_a?(AST::Identifier) && type.resolved_type.sub_type == :optional
if optional_within
out.puts " _, err = e.EncodeBool(#{element_var} != nil)"
out.puts " if err != nil {"
out.puts " return err"
out.puts " }"
out.puts " if #{element_var} != nil {"
var = "(*#{element_var})"
end
out.puts " err = #{element_var}.EncodeTo(e)"
out.puts " if err != nil {"
out.puts " return err"
out.puts " }"
if optional_within
out.puts " }"
end
out.puts " }"
else
raise "Unknown sub_type: #{type.sub_type}"
end
when AST::Definitions::Base
if self_encode
out.puts " err = #{name type}(#{var}).EncodeTo(e)"
else
out.puts " err = #{var}.EncodeTo(e)"
end
else
out.puts " _, err = e.Encode(#{var})"
end
if optional
out.puts " }"
end
out.puts " if err != nil {"
out.puts " return err"
out.puts " }"
end

def render_xdr_type_interface(out, name)
out.puts "// xdrType signals that this type is an type representing"
out.puts "// representing XDR values defined by this package."
out.puts "func (s #{name}) xdrType() {}"
out.break
out.puts "var _ xdrType = (*#{name})(nil)"
out.break
end

def render_top_matter(out)
out.puts <<-EOS.strip_heredoc
// Package #{@namespace || "main"} is generated from:
Expand All @@ -354,6 +557,10 @@ def render_top_matter(out)
"github.com/stellar/go-xdr/xdr3"
)
type xdrType interface {
xdrType()
}
// Unmarshal reads an xdr element from `r` into `v`.
func Unmarshal(r io.Reader, v interface{}) (int, error) {
// delegate to xdr package's Unmarshal
Expand All @@ -362,6 +569,15 @@ def render_top_matter(out)
// Marshal writes an xdr element `v` into `w`.
func Marshal(w io.Writer, v interface{}) (int, error) {
if _, ok := v.(xdrType); ok {
if bm, ok := v.(encoding.BinaryMarshaler); ok {
b, err := bm.MarshalBinary()
if err != nil {
return 0, err
}
return w.Write(b)
}
}
// delegate to xdr package's Marshal
return xdr.Marshal(w, v)
}
Expand Down

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