Bump actions/checkout from 3 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v3...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/ci.yml

@@ -8,13 +8,13 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        go: [ '1.18', '1.17', '1.16', '1.15' ]
+        go: [ '1.20', '1.19', '1.18', '1.17', '1.16' ]
         os: [ ubuntu-latest, macOS-latest, windows-latest ]
     name: ${{ matrix.os }} Go ${{ matrix.go }} Tests
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Setup go
-        uses: actions/setup-go@v3
+        uses: actions/setup-go@v4
         with:
           go-version: ${{ matrix.go }}
       - run: go test

.github/workflows/codeql-analysis.yml

@@ -38,7 +38,7 @@ jobs:
 
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL

.github/workflows/release.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Generate build files
         uses: thatisuday/go-cross-build@v1.0.2
         with:

README.md

@@ -75,8 +75,8 @@ import _ "github.com/joho/godotenv/autoload"
 While `.env` in the project root is the default, you don't have to be constrained, both examples below are 100% legit
 
 ```go
-_ = godotenv.Load("somerandomfile")
-_ = godotenv.Load("filenumberone.env", "filenumbertwo.env")
+godotenv.Load("somerandomfile")
+godotenv.Load("filenumberone.env", "filenumbertwo.env")
 ```
 
 If you want to be really fancy with your env file you can do comments and exports (below is a valid env file)
@@ -153,6 +153,8 @@ godotenv -f /some/path/to/.env some_command with some args
 
 If you don't specify `-f` it will fall back on the default of loading `.env` in `PWD`
 
+By default, it won't override existing environment variables; you can do that with the `-o` flag.
+
 ### Writing Env Files
 
 Godotenv can also write a map representing the environment to a correctly-formatted and escaped file

cmd/godotenv/cmd.go

@@ -15,13 +15,15 @@ func main() {
 	flag.BoolVar(&showHelp, "h", false, "show help")
 	var rawEnvFilenames string
 	flag.StringVar(&rawEnvFilenames, "f", "", "comma separated paths to .env files")
+	var overload bool
+	flag.BoolVar(&overload, "o", false, "override existing .env variables")
 
 	flag.Parse()
 
 	usage := `
 Run a process with an env setup from a .env file
 
-godotenv [-f ENV_FILE_PATHS] COMMAND_ARGS
+godotenv [-o] [-f ENV_FILE_PATHS] COMMAND_ARGS
 
 ENV_FILE_PATHS: comma separated paths to .env files
 COMMAND_ARGS: command and args you want to run
@@ -47,7 +49,7 @@ example
 	cmd := args[0]
 	cmdArgs := args[1:]
 
-	err := godotenv.Exec(envFilenames, cmd, cmdArgs)
+	err := godotenv.Exec(envFilenames, cmd, cmdArgs, overload)
 	if err != nil {
 		log.Fatal(err)
 	}

fixtures/comments.env

@@ -0,0 +1,4 @@
+# Full line comment
+foo=bar # baz
+bar=foo#baz
+baz="foo"#bar

fixtures/equals.env

@@ -1,2 +1 @@
 export OPTION_A='postgres://localhost:5432/database?sslmode=disable'
-

fixtures/plain.env

@@ -5,3 +5,4 @@ OPTION_D =4
 OPTION_E = 5
 OPTION_F = 
 OPTION_G=
+OPTION_H=1 2

fixtures/quoted.env

@@ -7,3 +7,13 @@ OPTION_F="2"
 OPTION_G=""
 OPTION_H="\n"
 OPTION_I = "echo 'asd'"
+OPTION_J='line 1
+line 2'
+OPTION_K='line one
+this is \'quoted\'
+one more line'
+OPTION_L="line 1
+line 2"
+OPTION_M="line one
+this is \"quoted\"
+one more line"

godotenv.go

@@ -14,13 +14,11 @@
 package godotenv
 
 import (
-	"bufio"
-	"errors"
+	"bytes"
 	"fmt"
 	"io"
 	"os"
 	"os/exec"
-	"regexp"
 	"sort"
 	"strconv"
 	"strings"
@@ -28,6 +26,17 @@ import (
 
 const doubleQuoteSpecialChars = "\\\n\r\"!$`"
 
+// Parse reads an env file from io.Reader, returning a map of keys and values.
+func Parse(r io.Reader) (map[string]string, error) {
+	var buf bytes.Buffer
+	_, err := io.Copy(&buf, r)
+	if err != nil {
+		return nil, err
+	}
+
+	return UnmarshalBytes(buf.Bytes())
+}
+
 // Load will read your env file(s) and load them into ENV for this process.
 //
 // Call this function as close as possible to the start of your program (ideally in main).
@@ -96,37 +105,17 @@ func Read(filenames ...string) (envMap map[string]string, err error) {
 	return
 }
 
-// Parse reads an env file from io.Reader, returning a map of keys and values.
-func Parse(r io.Reader) (envMap map[string]string, err error) {
-	envMap = make(map[string]string)
-
-	var lines []string
-	scanner := bufio.NewScanner(r)
-	for scanner.Scan() {
-		lines = append(lines, scanner.Text())
-	}
-
-	if err = scanner.Err(); err != nil {
-		return
-	}
-
-	for _, fullLine := range lines {
-		if !isIgnoredLine(fullLine) {
-			var key, value string
-			key, value, err = parseLine(fullLine, envMap)
-
-			if err != nil {
-				return
-			}
-			envMap[key] = value
-		}
-	}
-	return
-}
-
 // Unmarshal reads an env file from a string, returning a map of keys and values.
 func Unmarshal(str string) (envMap map[string]string, err error) {
-	return Parse(strings.NewReader(str))
+	return UnmarshalBytes([]byte(str))
+}
+
+// UnmarshalBytes parses env file from byte slice of chars, returning a map of keys and values.
+func UnmarshalBytes(src []byte) (map[string]string, error) {
+	out := make(map[string]string)
+	err := parseBytes(src, out)
+
+	return out, err
 }
 
 // Exec loads env vars from the specified filenames (empty map falls back to default)
@@ -135,9 +124,15 @@ func Unmarshal(str string) (envMap map[string]string, err error) {
 // Simply hooks up os.Stdin/err/out to the command and calls Run().
 //
 // If you want more fine grained control over your command it's recommended
-// that you use `Load()` or `Read()` and the `os/exec` package yourself.
-func Exec(filenames []string, cmd string, cmdArgs []string) error {
-	Load(filenames...)
+// that you use `Load()`, `Overload()` or `Read()` and the `os/exec` package yourself.
+func Exec(filenames []string, cmd string, cmdArgs []string, overload bool) error {
+	op := Load
+	if overload {
+		op = Overload
+	}
+	if err := op(filenames...); err != nil {
+		return err
+	}
 
 	command := exec.Command(cmd, cmdArgs...)
 	command.Stdin = os.Stdin
@@ -161,8 +156,7 @@ func Write(envMap map[string]string, filename string) error {
 	if err != nil {
 		return err
 	}
-	file.Sync()
-	return err
+	return file.Sync()
 }
 
 // Marshal outputs the given environment as a dotenv-formatted environment file.
@@ -202,7 +196,7 @@ func loadFile(filename string, overload bool) error {
 
 	for key, value := range envMap {
 		if !currentEnv[key] || overload {
-			os.Setenv(key, value)
+			_ = os.Setenv(key, value)
 		}
 	}
 
@@ -219,135 +213,6 @@ func readFile(filename string) (envMap map[string]string, err error) {
 	return Parse(file)
 }
 
-var exportRegex = regexp.MustCompile(`^\s*(?:export\s+)?(.*?)\s*$`)
-
-func parseLine(line string, envMap map[string]string) (key string, value string, err error) {
-	if len(line) == 0 {
-		err = errors.New("zero length string")
-		return
-	}
-
-	// ditch the comments (but keep quoted hashes)
-	if strings.Contains(line, "#") {
-		segmentsBetweenHashes := strings.Split(line, "#")
-		quotesAreOpen := false
-		var segmentsToKeep []string
-		for _, segment := range segmentsBetweenHashes {
-			if strings.Count(segment, "\"") == 1 || strings.Count(segment, "'") == 1 {
-				if quotesAreOpen {
-					quotesAreOpen = false
-					segmentsToKeep = append(segmentsToKeep, segment)
-				} else {
-					quotesAreOpen = true
-				}
-			}
-
-			if len(segmentsToKeep) == 0 || quotesAreOpen {
-				segmentsToKeep = append(segmentsToKeep, segment)
-			}
-		}
-
-		line = strings.Join(segmentsToKeep, "#")
-	}
-
-	firstEquals := strings.Index(line, "=")
-	firstColon := strings.Index(line, ":")
-	splitString := strings.SplitN(line, "=", 2)
-	if firstColon != -1 && (firstColon < firstEquals || firstEquals == -1) {
-		//this is a yaml-style line
-		splitString = strings.SplitN(line, ":", 2)
-	}
-
-	if len(splitString) != 2 {
-		err = errors.New("Can't separate key from value")
-		return
-	}
-
-	// Parse the key
-	key = splitString[0]
-	if strings.HasPrefix(key, "export") {
-		key = strings.TrimPrefix(key, "export")
-	}
-	key = strings.TrimSpace(key)
-
-	key = exportRegex.ReplaceAllString(splitString[0], "$1")
-
-	// Parse the value
-	value = parseValue(splitString[1], envMap)
-	return
-}
-
-var (
-	singleQuotesRegex  = regexp.MustCompile(`\A'(.*)'\z`)
-	doubleQuotesRegex  = regexp.MustCompile(`\A"(.*)"\z`)
-	escapeRegex        = regexp.MustCompile(`\\.`)
-	unescapeCharsRegex = regexp.MustCompile(`\\([^$])`)
-)
-
-func parseValue(value string, envMap map[string]string) string {
-
-	// trim
-	value = strings.Trim(value, " ")
-
-	// check if we've got quoted values or possible escapes
-	if len(value) > 1 {
-		singleQuotes := singleQuotesRegex.FindStringSubmatch(value)
-
-		doubleQuotes := doubleQuotesRegex.FindStringSubmatch(value)
-
-		if singleQuotes != nil || doubleQuotes != nil {
-			// pull the quotes off the edges
-			value = value[1 : len(value)-1]
-		}
-
-		if doubleQuotes != nil {
-			// expand newlines
-			value = escapeRegex.ReplaceAllStringFunc(value, func(match string) string {
-				c := strings.TrimPrefix(match, `\`)
-				switch c {
-				case "n":
-					return "\n"
-				case "r":
-					return "\r"
-				default:
-					return match
-				}
-			})
-			// unescape characters
-			value = unescapeCharsRegex.ReplaceAllString(value, "$1")
-		}
-
-		if singleQuotes == nil {
-			value = expandVariables(value, envMap)
-		}
-	}
-
-	return value
-}
-
-var expandVarRegex = regexp.MustCompile(`(\\)?(\$)(\()?\{?([A-Z0-9_]+)?\}?`)
-
-func expandVariables(v string, m map[string]string) string {
-	return expandVarRegex.ReplaceAllStringFunc(v, func(s string) string {
-		submatch := expandVarRegex.FindStringSubmatch(s)
-
-		if submatch == nil {
-			return s
-		}
-		if submatch[1] == "\\" || submatch[2] == "(" {
-			return submatch[0][1:]
-		} else if submatch[4] != "" {
-			return m[submatch[4]]
-		}
-		return s
-	})
-}
-
-func isIgnoredLine(line string) bool {
-	trimmedLine := strings.TrimSpace(line)
-	return len(trimmedLine) == 0 || strings.HasPrefix(trimmedLine, "#")
-}
-
 func doubleQuoteEscape(line string) string {
 	for _, c := range doubleQuoteSpecialChars {
 		toReplace := "\\" + string(c)

godotenv_test.go

@@ -12,9 +12,14 @@ import (
 var noopPresets = make(map[string]string)
 
 func parseAndCompare(t *testing.T, rawEnvLine string, expectedKey string, expectedValue string) {
-	key, value, _ := parseLine(rawEnvLine, noopPresets)
-	if key != expectedKey || value != expectedValue {
-		t.Errorf("Expected '%v' to parse as '%v' => '%v', got '%v' => '%v' instead", rawEnvLine, expectedKey, expectedValue, key, value)
+	result, err := Unmarshal(rawEnvLine)
+
+	if err != nil {
+		t.Errorf("Expected %q to parse as %q: %q, errored %q", rawEnvLine, expectedKey, expectedValue, err)
+		return
+	}
+	if result[expectedKey] != expectedValue {
+		t.Errorf("Expected '%v' to parse as '%v' => '%v', got %q instead", rawEnvLine, expectedKey, expectedValue, result)
 	}
 }
 
@@ -35,7 +40,7 @@ func loadEnvAndCompareValues(t *testing.T, loader func(files ...string) error, e
 		envValue := os.Getenv(k)
 		v := expectedValues[k]
 		if envValue != v {
-			t.Errorf("Mismatch for key '%v': expected '%v' got '%v'", k, v, envValue)
+			t.Errorf("Mismatch for key '%v': expected '%#v' got '%#v'", k, v, envValue)
 		}
 	}
 }
@@ -80,6 +85,7 @@ func TestReadPlainEnv(t *testing.T) {
 		"OPTION_E": "5",
 		"OPTION_F": "",
 		"OPTION_G": "",
+		"OPTION_H": "1 2",
 	}
 
 	envMap, err := Read(envFileName)
@@ -153,6 +159,7 @@ func TestLoadPlainEnv(t *testing.T) {
 		"OPTION_C": "3",
 		"OPTION_D": "4",
 		"OPTION_E": "5",
+		"OPTION_H": "1 2",
 	}
 
 	loadEnvAndCompareValues(t, Load, envFileName, expectedValues, noopPresets)
@@ -189,6 +196,10 @@ func TestLoadQuotedEnv(t *testing.T) {
 		"OPTION_G": "",
 		"OPTION_H": "\n",
 		"OPTION_I": "echo 'asd'",
+		"OPTION_J": "line 1\nline 2",
+		"OPTION_K": "line one\nthis is \\'quoted\\'\none more line",
+		"OPTION_L": "line 1\nline 2",
+		"OPTION_M": "line one\nthis is \"quoted\"\none more line",
 	}
 
 	loadEnvAndCompareValues(t, Load, envFileName, expectedValues, noopPresets)
@@ -268,7 +279,34 @@ func TestExpanding(t *testing.T) {
 			}
 		})
 	}
+}
 
+func TestVariableStringValueSeparator(t *testing.T) {
+	input := "TEST_URLS=\"stratum+tcp://stratum.antpool.com:3333\nstratum+tcp://stratum.antpool.com:443\""
+	want := map[string]string{
+		"TEST_URLS": "stratum+tcp://stratum.antpool.com:3333\nstratum+tcp://stratum.antpool.com:443",
+	}
+	got, err := Parse(strings.NewReader(input))
+	if err != nil {
+		t.Error(err)
+	}
+
+	if len(got) != len(want) {
+		t.Fatalf(
+			"unexpected value:\nwant:\n\t%#v\n\ngot:\n\t%#v", want, got)
+	}
+
+	for k, wantVal := range want {
+		gotVal, ok := got[k]
+		if !ok {
+			t.Fatalf("key %q doesn't present in result", k)
+		}
+		if wantVal != gotVal {
+			t.Fatalf(
+				"mismatch in %q value:\nwant:\n\t%s\n\ngot:\n\t%s", k,
+				wantVal, gotVal)
+		}
+	}
 }
 
 func TestActualEnvVarsAreLeftAlone(t *testing.T) {
@@ -337,6 +375,9 @@ func TestParsing(t *testing.T) {
 	// expect(env('foo=bar ')).to eql('foo' => 'bar') # not 'bar '
 	parseAndCompare(t, "FOO=bar ", "FOO", "bar")
 
+	// unquoted internal whitespace is preserved
+	parseAndCompare(t, `KEY=value value`, "KEY", "value value")
+
 	// it 'ignores inline comments' do
 	// expect(env("foo=bar # this is foo")).to eql('foo' => 'bar')
 	parseAndCompare(t, "FOO=bar # this is foo", "FOO", "bar")
@@ -359,10 +400,8 @@ func TestParsing(t *testing.T) {
 	parseAndCompare(t, `FOO="bar\\r\ b\az"`, "FOO", "bar\\r baz")
 
 	parseAndCompare(t, `="value"`, "", "value")
-	parseAndCompare(t, `KEY="`, "KEY", "\"")
-	parseAndCompare(t, `KEY="value`, "KEY", "\"value")
 
-	// leading whitespace should be ignored
+	// unquoted whitespace around keys should be ignored
 	parseAndCompare(t, " KEY =value", "KEY", "value")
 	parseAndCompare(t, "   KEY=value", "KEY", "value")
 	parseAndCompare(t, "\tKEY=value", "KEY", "value")
@@ -370,40 +409,45 @@ func TestParsing(t *testing.T) {
 	// it 'throws an error if line format is incorrect' do
 	// expect{env('lol$wut')}.to raise_error(Dotenv::FormatError)
 	badlyFormattedLine := "lol$wut"
-	_, _, err := parseLine(badlyFormattedLine, noopPresets)
+	_, err := Unmarshal(badlyFormattedLine)
 	if err == nil {
 		t.Errorf("Expected \"%v\" to return error, but it didn't", badlyFormattedLine)
 	}
 }
 
 func TestLinesToIgnore(t *testing.T) {
-	// it 'ignores empty lines' do
-	// expect(env("\n \t  \nfoo=bar\n \nfizz=buzz")).to eql('foo' => 'bar', 'fizz' => 'buzz')
-	if !isIgnoredLine("\n") {
-		t.Error("Line with nothing but line break wasn't ignored")
+	cases := map[string]struct {
+		input string
+		want  string
+	}{
+		"Line with nothing but line break": {
+			input: "\n",
+		},
+		"Line with nothing but windows-style line break": {
+			input: "\r\n",
+		},
+		"Line full of whitespace": {
+			input: "\t\t ",
+		},
+		"Comment": {
+			input: "# Comment",
+		},
+		"Indented comment": {
+			input: "\t # comment",
+		},
+		"non-ignored value": {
+			input: `export OPTION_B='\n'`,
+			want:  `export OPTION_B='\n'`,
+		},
 	}
 
-	if !isIgnoredLine("\r\n") {
-		t.Error("Line with nothing but windows-style line break wasn't ignored")
+	for n, c := range cases {
+		t.Run(n, func(t *testing.T) {
+			got := string(getStatementStart([]byte(c.input)))
+			if got != c.want {
+				t.Errorf("Expected:\t %q\nGot:\t %q", c.want, got)
 			}
-
-	if !isIgnoredLine("\t\t ") {
-		t.Error("Line full of whitespace wasn't ignored")
-	}
-
-	// it 'ignores comment lines' do
-	// expect(env("\n\n\n # HERE GOES FOO \nfoo=bar")).to eql('foo' => 'bar')
-	if !isIgnoredLine("# comment") {
-		t.Error("Comment wasn't ignored")
-	}
-
-	if !isIgnoredLine("\t#comment") {
-		t.Error("Indented comment wasn't ignored")
-	}
-
-	// make sure we're not getting false positives
-	if isIgnoredLine(`export OPTION_B='\n'`) {
-		t.Error("ignoring a perfectly valid line to parse")
+		})
 	}
 }
 
@@ -424,6 +468,17 @@ func TestErrorParsing(t *testing.T) {
 	}
 }
 
+func TestComments(t *testing.T) {
+	envFileName := "fixtures/comments.env"
+	expectedValues := map[string]string{
+		"foo": "bar",
+		"bar": "foo#baz",
+		"baz": "foo",
+	}
+
+	loadEnvAndCompareValues(t, Load, envFileName, expectedValues, noopPresets)
+}
+
 func TestWrite(t *testing.T) {
 	writeAndCompare := func(env string, expected string) {
 		envMap, _ := Unmarshal(env)
@@ -472,3 +527,110 @@ func TestRoundtrip(t *testing.T) {
 
 	}
 }
+
+func TestTrailingNewlines(t *testing.T) {
+	cases := map[string]struct {
+		input string
+		key   string
+		value string
+	}{
+		"Simple value without trailing newline": {
+			input: "KEY=value",
+			key:   "KEY",
+			value: "value",
+		},
+		"Value with internal whitespace without trailing newline": {
+			input: "KEY=value value",
+			key:   "KEY",
+			value: "value value",
+		},
+		"Value with internal whitespace with trailing newline": {
+			input: "KEY=value value\n",
+			key:   "KEY",
+			value: "value value",
+		},
+		"YAML style - value with internal whitespace without trailing newline": {
+			input: "KEY: value value",
+			key:   "KEY",
+			value: "value value",
+		},
+		"YAML style - value with internal whitespace with trailing newline": {
+			input: "KEY: value value\n",
+			key:   "KEY",
+			value: "value value",
+		},
+	}
+
+	for n, c := range cases {
+		t.Run(n, func(t *testing.T) {
+			result, err := Unmarshal(c.input)
+			if err != nil {
+				t.Errorf("Input: %q Unexpected error:\t%q", c.input, err)
+			}
+			if result[c.key] != c.value {
+				t.Errorf("Input %q Expected:\t %q/%q\nGot:\t %q", c.input, c.key, c.value, result)
+			}
+		})
+	}
+}
+
+func TestWhitespace(t *testing.T) {
+	cases := map[string]struct {
+		input string
+		key   string
+		value string
+	}{
+		"Leading whitespace": {
+			input: " A=a\n",
+			key: "A",
+			value: "a",
+		},
+		"Leading tab": {
+			input: "\tA=a\n",
+			key: "A",
+			value: "a",
+		},
+		"Leading mixed whitespace": {
+			input: " \t \t\n\t \t A=a\n",
+			key: "A",
+			value: "a",
+		},
+		"Leading whitespace before export": {
+			input: " \t\t export    A=a\n",
+			key: "A",
+			value: "a",
+		},
+		"Trailing whitespace": {
+			input: "A=a \t \t\n",
+			key: "A",
+			value: "a",
+		},
+		"Trailing whitespace with export": {
+			input: "export A=a\t \t \n",
+			key: "A",
+			value: "a",
+		},
+		"No EOL": {
+			input: "A=a",
+			key: "A",
+			value: "a",
+		},
+		"Trailing whitespace with no EOL": {
+			input: "A=a ",
+			key: "A",
+			value: "a",
+		},
+	}
+
+	for n, c := range cases {
+		t.Run(n, func(t *testing.T) {
+			result, err := Unmarshal(c.input)
+			if err != nil {
+				t.Errorf("Input: %q Unexpected error:\t%q", c.input, err)
+			}
+			if result[c.key] != c.value {
+				t.Errorf("Input %q Expected:\t %q/%q\nGot:\t %q", c.input, c.key, c.value, result)
+			}
+		})
+	}
+}

parser.go

@@ -0,0 +1,271 @@
+package godotenv
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"regexp"
+	"strings"
+	"unicode"
+)
+
+const (
+	charComment       = '#'
+	prefixSingleQuote = '\''
+	prefixDoubleQuote = '"'
+
+	exportPrefix = "export"
+)
+
+func parseBytes(src []byte, out map[string]string) error {
+	src = bytes.Replace(src, []byte("\r\n"), []byte("\n"), -1)
+	cutset := src
+	for {
+		cutset = getStatementStart(cutset)
+		if cutset == nil {
+			// reached end of file
+			break
+		}
+
+		key, left, err := locateKeyName(cutset)
+		if err != nil {
+			return err
+		}
+
+		value, left, err := extractVarValue(left, out)
+		if err != nil {
+			return err
+		}
+
+		out[key] = value
+		cutset = left
+	}
+
+	return nil
+}
+
+// getStatementPosition returns position of statement begin.
+//
+// It skips any comment line or non-whitespace character.
+func getStatementStart(src []byte) []byte {
+	pos := indexOfNonSpaceChar(src)
+	if pos == -1 {
+		return nil
+	}
+
+	src = src[pos:]
+	if src[0] != charComment {
+		return src
+	}
+
+	// skip comment section
+	pos = bytes.IndexFunc(src, isCharFunc('\n'))
+	if pos == -1 {
+		return nil
+	}
+
+	return getStatementStart(src[pos:])
+}
+
+// locateKeyName locates and parses key name and returns rest of slice
+func locateKeyName(src []byte) (key string, cutset []byte, err error) {
+	// trim "export" and space at beginning
+	src = bytes.TrimLeftFunc(src, isSpace)
+	if bytes.HasPrefix(src, []byte(exportPrefix)) {
+		trimmed := bytes.TrimPrefix(src, []byte(exportPrefix))
+		if bytes.IndexFunc(trimmed, isSpace) == 0 {
+			src = bytes.TrimLeftFunc(trimmed, isSpace)
+		}
+	}
+
+	// locate key name end and validate it in single loop
+	offset := 0
+loop:
+	for i, char := range src {
+		rchar := rune(char)
+		if isSpace(rchar) {
+			continue
+		}
+
+		switch char {
+		case '=', ':':
+			// library also supports yaml-style value declaration
+			key = string(src[0:i])
+			offset = i + 1
+			break loop
+		case '_':
+		default:
+			// variable name should match [A-Za-z0-9_.]
+			if unicode.IsLetter(rchar) || unicode.IsNumber(rchar) || rchar == '.' {
+				continue
+			}
+
+			return "", nil, fmt.Errorf(
+				`unexpected character %q in variable name near %q`,
+				string(char), string(src))
+		}
+	}
+
+	if len(src) == 0 {
+		return "", nil, errors.New("zero length string")
+	}
+
+	// trim whitespace
+	key = strings.TrimRightFunc(key, unicode.IsSpace)
+	cutset = bytes.TrimLeftFunc(src[offset:], isSpace)
+	return key, cutset, nil
+}
+
+// extractVarValue extracts variable value and returns rest of slice
+func extractVarValue(src []byte, vars map[string]string) (value string, rest []byte, err error) {
+	quote, hasPrefix := hasQuotePrefix(src)
+	if !hasPrefix {
+		// unquoted value - read until end of line
+		endOfLine := bytes.IndexFunc(src, isLineEnd)
+
+		// Hit EOF without a trailing newline
+		if endOfLine == -1 {
+			endOfLine = len(src)
+
+			if endOfLine == 0 {
+				return "", nil, nil
+			}
+		}
+
+		// Convert line to rune away to do accurate countback of runes
+		line := []rune(string(src[0:endOfLine]))
+
+		// Assume end of line is end of var
+		endOfVar := len(line)
+		if endOfVar == 0 {
+			return "", src[endOfLine:], nil
+		}
+
+		// Work backwards to check if the line ends in whitespace then
+		// a comment (ie asdasd # some comment)
+		for i := endOfVar - 1; i >= 0; i-- {
+			if line[i] == charComment && i > 0 {
+				if isSpace(line[i-1]) {
+					endOfVar = i
+					break
+				}
+			}
+		}
+
+		trimmed := strings.TrimFunc(string(line[0:endOfVar]), isSpace)
+
+		return expandVariables(trimmed, vars), src[endOfLine:], nil
+	}
+
+	// lookup quoted string terminator
+	for i := 1; i < len(src); i++ {
+		if char := src[i]; char != quote {
+			continue
+		}
+
+		// skip escaped quote symbol (\" or \', depends on quote)
+		if prevChar := src[i-1]; prevChar == '\\' {
+			continue
+		}
+
+		// trim quotes
+		trimFunc := isCharFunc(rune(quote))
+		value = string(bytes.TrimLeftFunc(bytes.TrimRightFunc(src[0:i], trimFunc), trimFunc))
+		if quote == prefixDoubleQuote {
+			// unescape newlines for double quote (this is compat feature)
+			// and expand environment variables
+			value = expandVariables(expandEscapes(value), vars)
+		}
+
+		return value, src[i+1:], nil
+	}
+
+	// return formatted error if quoted string is not terminated
+	valEndIndex := bytes.IndexFunc(src, isCharFunc('\n'))
+	if valEndIndex == -1 {
+		valEndIndex = len(src)
+	}
+
+	return "", nil, fmt.Errorf("unterminated quoted value %s", src[:valEndIndex])
+}
+
+func expandEscapes(str string) string {
+	out := escapeRegex.ReplaceAllStringFunc(str, func(match string) string {
+		c := strings.TrimPrefix(match, `\`)
+		switch c {
+		case "n":
+			return "\n"
+		case "r":
+			return "\r"
+		default:
+			return match
+		}
+	})
+	return unescapeCharsRegex.ReplaceAllString(out, "$1")
+}
+
+func indexOfNonSpaceChar(src []byte) int {
+	return bytes.IndexFunc(src, func(r rune) bool {
+		return !unicode.IsSpace(r)
+	})
+}
+
+// hasQuotePrefix reports whether charset starts with single or double quote and returns quote character
+func hasQuotePrefix(src []byte) (prefix byte, isQuored bool) {
+	if len(src) == 0 {
+		return 0, false
+	}
+
+	switch prefix := src[0]; prefix {
+	case prefixDoubleQuote, prefixSingleQuote:
+		return prefix, true
+	default:
+		return 0, false
+	}
+}
+
+func isCharFunc(char rune) func(rune) bool {
+	return func(v rune) bool {
+		return v == char
+	}
+}
+
+// isSpace reports whether the rune is a space character but not line break character
+//
+// this differs from unicode.IsSpace, which also applies line break as space
+func isSpace(r rune) bool {
+	switch r {
+	case '\t', '\v', '\f', '\r', ' ', 0x85, 0xA0:
+		return true
+	}
+	return false
+}
+
+func isLineEnd(r rune) bool {
+	if r == '\n' || r == '\r' {
+		return true
+	}
+	return false
+}
+
+var (
+	escapeRegex        = regexp.MustCompile(`\\.`)
+	expandVarRegex     = regexp.MustCompile(`(\\)?(\$)(\()?\{?([A-Z0-9_]+)?\}?`)
+	unescapeCharsRegex = regexp.MustCompile(`\\([^$])`)
+)
+
+func expandVariables(v string, m map[string]string) string {
+	return expandVarRegex.ReplaceAllStringFunc(v, func(s string) string {
+		submatch := expandVarRegex.FindStringSubmatch(s)
+
+		if submatch == nil {
+			return s
+		}
+		if submatch[1] == "\\" || submatch[2] == "(" {
+			return submatch[0][1:]
+		} else if submatch[4] != "" {
+			return m[submatch[4]]
+		}
+		return s
+	})
+}