Buffer increase (#738)

Increase Scanner buffer size for Stanza reader

Author: strajansebastian

AUTHORS

@@ -32,3 +32,4 @@ List of contributors, in chronological order:
 * Ludovico Cavedon (https://github.com/cavedon)
 * Petr Jediny (https://github.com/pjediny)
 * Maximilian Stein (https://github.com/steinymity)
+* Strajan Sebastian (https://github.com/strajansebastian)

deb/format.go

@@ -11,6 +11,9 @@ import (
 // Stanza or paragraph of Debian control file
 type Stanza map[string]string
 
+// MaxFieldSize is maximum stanza field size in bytes
+const MaxFieldSize = 2 * 1024 * 1024
+
 // Canonical order of fields in stanza
 // Taken from: http://bazaar.launchpad.net/~ubuntu-branches/ubuntu/vivid/apt/vivid/view/head:/apt-pkg/tagfile.cc#L504
 var (
@@ -214,7 +217,10 @@ type ControlFileReader struct {
 
 // NewControlFileReader creates ControlFileReader, it wraps with buffering
 func NewControlFileReader(r io.Reader) *ControlFileReader {
-	return &ControlFileReader{scanner: bufio.NewScanner(bufio.NewReaderSize(r, 32768))}
+	scnr := bufio.NewScanner(bufio.NewReaderSize(r, 32768))
+	scnr.Buffer(nil, MaxFieldSize)
+
+	return &ControlFileReader{scanner: scnr}
 }
 
 // ReadStanza reeads one stanza from control file

deb/format_test.go

@@ -3,6 +3,7 @@ package deb
 import (
 	"bufio"
 	"bytes"
+	"os"
 	"strings"
 
 	. "gopkg.in/check.v1"
@@ -135,6 +136,17 @@ func (s *ControlFileSuite) TestCanonicalCase(c *C) {
 	c.Check(canonicalCase("packaGe-lIst"), Equals, "Package-List")
 }
 
+func (s *ControlFileSuite) TestLongFields(c *C) {
+	f, err := os.Open("long.stanza")
+	c.Assert(err, IsNil)
+	defer f.Close()
+
+	r := NewControlFileReader(f)
+	stanza, e := r.ReadStanza(false)
+	c.Assert(e, IsNil)
+	c.Assert(len(stanza["Provides"]), Equals, 586929)
+}
+
 func (s *ControlFileSuite) BenchmarkReadStanza(c *C) {
 	for i := 0; i < c.N; i++ {
 		reader := bytes.NewBufferString(controlFile)