Substitute old pktline encoder/decoder with new pktline scanner (#84)

* replace old pktline package with new pktline scanner

* remove error checks on pktline.NewFromString

* fix deppend bug

* reduce memory garbage when pktline.NewFromStrings

* improve int to hex conversion to help gc

* make intToHex func private

* clean function names

1 files changed, 208 insertions, 0 deletions

diff --git a/formats/packp/pktline/scanner_test.go b/formats/packp/pktline/scanner_test.go
new file mode 100644
index 0000000..08ca51f
--- /dev/null
+++ b/formats/packp/pktline/scanner_test.go
@@ -0,0 +1,208 @@
+package pktline_test
+
+import (
+	"fmt"
+	"io"
+	"strings"
+
+	"gopkg.in/src-d/go-git.v4/formats/packp/pktline"
+
+	. "gopkg.in/check.v1"
+)
+
+type SuiteScanner struct{}
+
+var _ = Suite(&SuiteScanner{})
+
+func (s *SuiteScanner) TestInvalid(c *C) {
+	for _, test := range [...]string{
+		"0001", "0002", "0003", "0004",
+		"0001asdfsadf", "0004foo",
+		"fff1", "fff2",
+		"gorka",
+		"0", "003",
+		"   5a", "5   a", "5   \n",
+		"-001", "-000",
+	} {
+		r := strings.NewReader(test)
+		sc := pktline.NewScanner(r)
+		_ = sc.Scan()
+		c.Assert(sc.Err(), ErrorMatches, pktline.ErrInvalidPktLen.Error(),
+			Commentf("data = %q", test))
+	}
+}
+
+func (s *SuiteScanner) TestEmptyReader(c *C) {
+	r := strings.NewReader("")
+	sc := pktline.NewScanner(r)
+	hasPayload := sc.Scan()
+	c.Assert(hasPayload, Equals, false)
+	c.Assert(sc.Err(), Equals, nil)
+}
+
+func (s *SuiteScanner) TestFlush(c *C) {
+	r, err := pktline.NewFromStrings("")
+	c.Assert(err, IsNil)
+	sc := pktline.NewScanner(r)
+	c.Assert(sc.Scan(), Equals, true)
+	payload := sc.Bytes()
+	c.Assert(len(payload), Equals, 0)
+}
+
+func (s *SuiteScanner) TestPktLineTooShort(c *C) {
+	r := strings.NewReader("010cfoobar")
+
+	sc := pktline.NewScanner(r)
+
+	c.Assert(sc.Scan(), Equals, false)
+	c.Assert(sc.Err(), ErrorMatches, "unexpected EOF")
+}
+
+func (s *SuiteScanner) TestScanAndPayload(c *C) {
+	for _, test := range [...]string{
+		"a",
+		"a\n",
+		strings.Repeat("a", 100),
+		strings.Repeat("a", 100) + "\n",
+		strings.Repeat("\x00", 100),
+		strings.Repeat("\x00", 100) + "\n",
+		strings.Repeat("a", pktline.MaxPayloadSize),
+		strings.Repeat("a", pktline.MaxPayloadSize-1) + "\n",
+	} {
+		r, err := pktline.NewFromStrings(test)
+		c.Assert(err, IsNil, Commentf("input len=%x, contents=%.10q\n", len(test), test))
+		sc := pktline.NewScanner(r)
+
+		c.Assert(sc.Scan(), Equals, true,
+			Commentf("test = %.20q...", test))
+		obtained := sc.Bytes()
+		c.Assert(obtained, DeepEquals, []byte(test),
+			Commentf("in = %.20q out = %.20q", test, string(obtained)))
+	}
+}
+
+func (s *SuiteScanner) TestSkip(c *C) {
+	for _, test := range [...]struct {
+		input    []string
+		n        int
+		expected []byte
+	}{
+		{
+			input: []string{
+				"first",
+				"second",
+				"third",
+				""},
+			n:        1,
+			expected: []byte("second"),
+		},
+		{
+			input: []string{
+				"first",
+				"second",
+				"third",
+				""},
+			n:        2,
+			expected: []byte("third"),
+		},
+	} {
+		r, err := pktline.NewFromStrings(test.input...)
+		c.Assert(err, IsNil)
+		sc := pktline.NewScanner(r)
+		for i := 0; i < test.n; i++ {
+			c.Assert(sc.Scan(), Equals, true,
+				Commentf("scan error = %s", sc.Err()))
+		}
+		c.Assert(sc.Scan(), Equals, true,
+			Commentf("scan error = %s", sc.Err()))
+		obtained := sc.Bytes()
+		c.Assert(obtained, DeepEquals, test.expected,
+			Commentf("\nin = %.20q\nout = %.20q\nexp = %.20q",
+				test.input, obtained, test.expected))
+	}
+}
+
+func (s *SuiteScanner) TestEOF(c *C) {
+	r, err := pktline.NewFromStrings("first", "second")
+	c.Assert(err, IsNil)
+	sc := pktline.NewScanner(r)
+	for sc.Scan() {
+	}
+	c.Assert(sc.Err(), IsNil)
+}
+
+// A section are several non flush-pkt lines followed by a flush-pkt, which
+// how the git protocol sends long messages.
+func (s *SuiteScanner) TestReadSomeSections(c *C) {
+	nSections := 2
+	nLines := 4
+	data := sectionsExample(c, nSections, nLines)
+	sc := pktline.NewScanner(data)
+
+	sectionCounter := 0
+	lineCounter := 0
+	for sc.Scan() {
+		if len(sc.Bytes()) == 0 {
+			sectionCounter++
+		}
+		lineCounter++
+	}
+	c.Assert(sc.Err(), IsNil)
+	c.Assert(sectionCounter, Equals, nSections)
+	c.Assert(lineCounter, Equals, (1+nLines)*nSections)
+}
+
+// returns nSection sections, each of them with nLines pkt-lines (not
+// counting the flush-pkt:
+//
+// 0009 0.0\n
+// 0009 0.1\n
+// ...
+// 0000
+// and so on
+func sectionsExample(c *C, nSections, nLines int) io.Reader {
+	ss := []string{}
+	for section := 0; section < nSections; section++ {
+		for line := 0; line < nLines; line++ {
+			line := fmt.Sprintf(" %d.%d\n", section, line)
+			ss = append(ss, line)
+		}
+		ss = append(ss, "")
+	}
+
+	ret, err := pktline.NewFromStrings(ss...)
+	c.Assert(err, IsNil)
+
+	return ret
+}
+
+func ExampleScanner() {
+	// A reader is needed as input.
+	input := strings.NewReader("000ahello\n" +
+		"000bworld!\n" +
+		"0000",
+	)
+
+	// Create the scanner...
+	s := pktline.NewScanner(input)
+
+	// and scan every pkt-line found in the input.
+	for s.Scan() {
+		payload := s.Bytes()
+		if len(payload) == 0 { // zero sized payloads correspond to flush-pkts.
+			fmt.Println("FLUSH-PKT DETECTED\n")
+		} else { // otherwise, you will be able to access the full payload.
+			fmt.Printf("PAYLOAD = %q\n", string(payload))
+		}
+	}
+
+	// this will catch any error when reading from the input, if any.
+	if s.Err() != nil {
+		fmt.Println(s.Err())
+	}
+
+	// Output:
+	// PAYLOAD = "hello\n"
+	// PAYLOAD = "world!\n"
+	// FLUSH-PKT DETECTED
+}