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https://github.com/golang/go
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net/textproto: faster header canonicalization with fewer allocations
By keeping a single copy of the strings that commonly show up in headers, we can avoid one string allocation per header. benchmark old ns/op new ns/op delta BenchmarkReadMIMEHeader 19590 10824 -44.75% BenchmarkUncommon 3168 1861 -41.26% benchmark old allocs new allocs delta BenchmarkReadMIMEHeader 32 25 -21.88% BenchmarkUncommon 5 5 0.00% R=bradfitz, golang-dev, dave, rsc, jra CC=golang-dev https://golang.org/cl/6721055
This commit is contained in:
Jeff R. Allen
Brad Fitzpatrick
parent
73c67606e9
commit
7e7b89f7d0
@ -486,6 +486,7 @@ func (r *Reader) ReadMIMEHeader() (MIMEHeader, error) {
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// letter and any letter following a hyphen to upper case;
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// the rest are converted to lowercase. For example, the
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// canonical key for "accept-encoding" is "Accept-Encoding".
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// MIME header keys are assumed to be ASCII only.
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func CanonicalMIMEHeaderKey(s string) string {
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// Quick check for canonical encoding.
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upper := true
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@ -502,28 +503,90 @@ func CanonicalMIMEHeaderKey(s string) string {
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return s
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}
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const toLower = 'a' - 'A'
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// canonicalMIMEHeaderKey is like CanonicalMIMEHeaderKey but is
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// allowed to mutate the provided byte slice before returning the
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// string.
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func canonicalMIMEHeaderKey(a []byte) string {
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// Look for it in commonHeaders , so that we can avoid an
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// allocation by sharing the strings among all users
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// of textproto. If we don't find it, a has been canonicalized
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// so just return string(a).
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upper := true
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lo := 0
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hi := len(commonHeaders)
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for i := 0; i < len(a); i++ {
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// Canonicalize: first letter upper case
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// and upper case after each dash.
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// (Host, User-Agent, If-Modified-Since).
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// MIME headers are ASCII only, so no Unicode issues.
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upper := true
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for i, v := range a {
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if v == ' ' {
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if a[i] == ' ' {
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a[i] = '-'
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upper = true
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continue
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}
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if upper && 'a' <= v && v <= 'z' {
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a[i] = v + 'A' - 'a'
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c := a[i]
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if upper && 'a' <= c && c <= 'z' {
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c -= toLower
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} else if !upper && 'A' <= c && c <= 'Z' {
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c += toLower
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}
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if !upper && 'A' <= v && v <= 'Z' {
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a[i] = v + 'a' - 'A'
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a[i] = c
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upper = c == '-' // for next time
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if lo < hi {
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for lo < hi && (len(commonHeaders[lo]) <= i || commonHeaders[lo][i] < c) {
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lo++
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}
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upper = v == '-'
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for hi > lo && commonHeaders[hi-1][i] > c {
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hi--
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}
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}
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}
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if lo < hi && len(commonHeaders[lo]) == len(a) {
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return commonHeaders[lo]
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}
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return string(a)
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}
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var commonHeaders = []string{
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"Accept",
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"Accept-Charset",
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"Accept-Encoding",
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"Accept-Language",
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"Accept-Ranges",
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"Cache-Control",
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"Cc",
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"Connection",
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"Content-Id",
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"Content-Language",
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"Content-Length",
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"Content-Transfer-Encoding",
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"Content-Type",
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"Date",
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"Dkim-Signature",
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"Etag",
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"Expires",
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"From",
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"Host",
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"If-Modified-Since",
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"If-None-Match",
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"In-Reply-To",
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"Last-Modified",
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"Location",
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"Message-Id",
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"Mime-Version",
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"Pragma",
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"Received",
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"Return-Path",
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"Server",
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"Set-Cookie",
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"Subject",
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"To",
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"User-Agent",
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"Via",
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"X-Forwarded-For",
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"X-Imforwards",
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"X-Powered-By",
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}
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@ -24,6 +24,7 @@ var canonicalHeaderKeyTests = []canonicalHeaderKeyTest{
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{"uSER-aGENT", "User-Agent"},
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{"user-agent", "User-Agent"},
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{"USER-AGENT", "User-Agent"},
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{"üser-agenT", "üser-Agent"}, // non-ASCII unchanged
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}
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func TestCanonicalMIMEHeaderKey(t *testing.T) {
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@ -241,18 +242,94 @@ func TestRFC959Lines(t *testing.T) {
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}
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}
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func TestCommonHeaders(t *testing.T) {
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// need to disable the commonHeaders-based optimization
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// during this check, or we'd not be testing anything
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oldch := commonHeaders
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commonHeaders = []string{}
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defer func() { commonHeaders = oldch }()
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last := ""
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for _, h := range oldch {
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if last > h {
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t.Errorf("%v is out of order", h)
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}
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if last == h {
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t.Errorf("%v is duplicated", h)
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}
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if canon := CanonicalMIMEHeaderKey(h); h != canon {
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t.Errorf("%v is not canonical", h)
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}
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last = h
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}
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}
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var clientHeaders = strings.Replace(`Host: golang.org
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Connection: keep-alive
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Cache-Control: max-age=0
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Accept: application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
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User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US) AppleWebKit/534.3 (KHTML, like Gecko) Chrome/6.0.472.63 Safari/534.3
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Accept-Encoding: gzip,deflate,sdch
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Accept-Language: en-US,en;q=0.8,fr-CH;q=0.6
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Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
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COOKIE: __utma=000000000.0000000000.0000000000.0000000000.0000000000.00; __utmb=000000000.0.00.0000000000; __utmc=000000000; __utmz=000000000.0000000000.00.0.utmcsr=code.google.com|utmccn=(referral)|utmcmd=referral|utmcct=/p/go/issues/detail
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Non-Interned: test
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`, "\n", "\r\n", -1)
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var serverHeaders = strings.Replace(`Content-Type: text/html; charset=utf-8
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Content-Encoding: gzip
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Date: Thu, 27 Sep 2012 09:03:33 GMT
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Server: Google Frontend
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Cache-Control: private
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Content-Length: 2298
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VIA: 1.1 proxy.example.com:80 (XXX/n.n.n-nnn)
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Connection: Close
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Non-Interned: test
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`, "\n", "\r\n", -1)
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func BenchmarkReadMIMEHeader(b *testing.B) {
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var buf bytes.Buffer
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br := bufio.NewReader(&buf)
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r := NewReader(br)
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for i := 0; i < b.N; i++ {
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buf.WriteString("User-Agent: not mozilla\r\nContent-Length: 23452\r\nContent-Type: text/html; charset-utf8\r\nFoo-Bar: foobar\r\nfoo-bar: some more string\r\n\r\n")
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var want int
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var find string
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if (i & 1) == 1 {
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buf.WriteString(clientHeaders)
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want = 10
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find = "Cookie"
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} else {
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buf.WriteString(serverHeaders)
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want = 9
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find = "Via"
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}
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h, err := r.ReadMIMEHeader()
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if err != nil {
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b.Fatal(err)
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}
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if len(h) != 4 {
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b.Fatalf("want 4")
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if len(h) != want {
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b.Fatalf("wrong number of headers: got %d, want %d", len(h), want)
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}
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if _, ok := h[find]; !ok {
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b.Fatalf("did not find key %s", find)
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}
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}
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}
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func BenchmarkUncommon(b *testing.B) {
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var buf bytes.Buffer
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br := bufio.NewReader(&buf)
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r := NewReader(br)
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for i := 0; i < b.N; i++ {
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buf.WriteString("uncommon-header-for-benchmark: foo\r\n\r\n")
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h, err := r.ReadMIMEHeader()
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if err != nil {
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b.Fatal(err)
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}
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if _, ok := h["Uncommon-Header-For-Benchmark"]; !ok {
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b.Fatal("Missing result header.")
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}
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}
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}
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