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Reduce mallocs in RowDescription.Decode

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This commit is contained in:
Jack Christensen
2019-04-18 22:33:11 -05:00
parent b2a540ca81
commit 2acb7b6d4e
1 changed files with 22 additions and 13 deletions
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row_description.go
+22 -13
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@@ -30,35 +30,44 @@ type RowDescription struct {
func (*RowDescription) Backend() {} func (*RowDescription) Backend() {}
func (dst *RowDescription) Decode(src []byte) error { func (dst *RowDescription) Decode(src []byte) error {
buf := bytes.NewBuffer(src)
if buf.Len() < 2 { if len(src) < 2 {
return &invalidMessageFormatErr{messageType: "RowDescription"} return &invalidMessageFormatErr{messageType: "RowDescription"}
} }
fieldCount := int(binary.BigEndian.Uint16(buf.Next(2))) fieldCount := int(binary.BigEndian.Uint16(src))
rp := 2
dst.Fields = dst.Fields[0:0] dst.Fields = dst.Fields[0:0]
for i := 0; i < fieldCount; i++ { for i := 0; i < fieldCount; i++ {
var fd FieldDescription var fd FieldDescription
bName, err := buf.ReadBytes(0)
if err != nil { idx := bytes.IndexByte(src[rp:], 0)
return err if idx < 0 {
return &invalidMessageFormatErr{messageType: "RowDescription"}
} }
bName := string(src[rp : rp+idx])
rp += idx + 1
fd.Name = string(bName[:len(bName)-1]) fd.Name = string(bName[:len(bName)-1])
// Since buf.Next() doesn't return an error if we hit the end of the buffer // Since buf.Next() doesn't return an error if we hit the end of the buffer
// check Len ahead of time // check Len ahead of time
if buf.Len() < 18 { if len(src[rp:]) < 18 {
return &invalidMessageFormatErr{messageType: "RowDescription"} return &invalidMessageFormatErr{messageType: "RowDescription"}
} }
fd.TableOID = binary.BigEndian.Uint32(buf.Next(4)) fd.TableOID = binary.BigEndian.Uint32(src[rp:])
fd.TableAttributeNumber = binary.BigEndian.Uint16(buf.Next(2)) rp += 4
fd.DataTypeOID = binary.BigEndian.Uint32(buf.Next(4)) fd.TableAttributeNumber = binary.BigEndian.Uint16(src[rp:])
fd.DataTypeSize = int16(binary.BigEndian.Uint16(buf.Next(2))) rp += 2
fd.TypeModifier = int32(binary.BigEndian.Uint32(buf.Next(4))) fd.DataTypeOID = binary.BigEndian.Uint32(src[rp:])
fd.Format = int16(binary.BigEndian.Uint16(buf.Next(2))) rp += 4
fd.DataTypeSize = int16(binary.BigEndian.Uint16(src[rp:]))
rp += 2
fd.TypeModifier = int32(binary.BigEndian.Uint32(src[rp:]))
rp += 4
fd.Format = int16(binary.BigEndian.Uint16(src[rp:]))
rp += 2
dst.Fields = append(dst.Fields, fd) dst.Fields = append(dst.Fields, fd)
} }