Remove redundant copy in ParseToProtobuf, require Go 1.20+ (#139)

Author: asmyasnikov

.github/workflows/ci.yml

@@ -13,9 +13,6 @@ jobs:
       matrix:
         go: ['1.20', '1.21']
         os: ['ubuntu-latest', 'windows-latest']
-        include:
-        - go: 1.16 # Oldest Go version still tested (Windows requires 1.20+ due to https://github.com/golang/go/issues/57455)
-          os: ubuntu-latest
     runs-on: ${{ matrix.os }}
     steps:
     - name: Set up Go 1.x

go.mod

@@ -1,8 +1,10 @@
 module github.com/pganalyze/pg_query_go/v6
 
-go 1.14
+go 1.20
 
 require (
 	github.com/google/go-cmp v0.5.5
 	google.golang.org/protobuf v1.31.0
 )
+
+require golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 // indirect

parser/parser.go

@@ -101,7 +101,7 @@ func ScanToProtobuf(input string) (result []byte, err error) {
 }
 
 // ParseToProtobuf - Parses the given SQL statement into a parse tree (Protobuf format)
-func ParseToProtobuf(input string) (result []byte, err error) {
+func ParseToProtobuf(input string) ([]byte, error) {
 	inputC := C.CString(input)
 	defer C.free(unsafe.Pointer(inputC))
 
@@ -110,13 +110,10 @@ func ParseToProtobuf(input string) (result []byte, err error) {
 	defer C.pg_query_free_protobuf_parse_result(resultC)
 
 	if resultC.error != nil {
-		err = newPgQueryError(resultC.error)
-		return
+		return nil, newPgQueryError(resultC.error)
 	}
 
-	result = []byte(C.GoStringN(resultC.parse_tree.data, C.int(resultC.parse_tree.len)))
-
-	return
+	return toBytes(C.GoStringN(resultC.parse_tree.data, C.int(resultC.parse_tree.len))), nil
 }
 
 // DeparseFromProtobuf - Deparses the given Protobuf format parse tree into a SQL statement

parser/string_to_bytes.go

@@ -0,0 +1,14 @@
+//go:build go1.20
+// +build go1.20
+
+package parser
+
+import "unsafe"
+
+func toBytes(s string) (b []byte) {
+	if s == "" {
+		return nil
+	}
+	
+	return unsafe.Slice(unsafe.StringData(s), len(s))
+}