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Add support for conditional requests (#162)
Add support for conditional requests (#162)
This change pulls in some code copied from net/http's fs.go so that we can support If-Match/If-None-Match requests. This will make it easy to put a caching proxy in front of linx-server instances. Request validation will still happen as long as the proxy can contact the origin, so expiration and deletion will still work as expected under normal circumstances.pull/170/head v2.1.3
mutantmonkey
6 years ago
committed by
Andrei Marcu
Andrei Marcu
3 changed files with 262 additions and 13 deletions
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Copyright (c) 2009 The Go Authors. All rights reserved. |
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Redistribution and use in source and binary forms, with or without |
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modification, are permitted provided that the following conditions are |
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met: |
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* Redistributions of source code must retain the above copyright |
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notice, this list of conditions and the following disclaimer. |
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* Redistributions in binary form must reproduce the above |
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copyright notice, this list of conditions and the following disclaimer |
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in the documentation and/or other materials provided with the |
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distribution. |
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* Neither the name of Google Inc. nor the names of its |
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contributors may be used to endorse or promote products derived from |
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this software without specific prior written permission. |
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
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A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
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OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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@ -0,0 +1,218 @@ |
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// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// HTTP file system request handler
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package httputil |
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import ( |
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"net/http" |
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"net/textproto" |
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"strings" |
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"time" |
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) |
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// scanETag determines if a syntactically valid ETag is present at s. If so,
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// the ETag and remaining text after consuming ETag is returned. Otherwise,
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// it returns "", "".
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func scanETag(s string) (etag string, remain string) { |
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s = textproto.TrimString(s) |
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start := 0 |
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if strings.HasPrefix(s, "W/") { |
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start = 2 |
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} |
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if len(s[start:]) < 2 || s[start] != '"' { |
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return "", "" |
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} |
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// ETag is either W/"text" or "text".
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// See RFC 7232 2.3.
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for i := start + 1; i < len(s); i++ { |
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c := s[i] |
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switch { |
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// Character values allowed in ETags.
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case c == 0x21 || c >= 0x23 && c <= 0x7E || c >= 0x80: |
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case c == '"': |
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return s[:i+1], s[i+1:] |
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default: |
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return "", "" |
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} |
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} |
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return "", "" |
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} |
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// etagStrongMatch reports whether a and b match using strong ETag comparison.
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// Assumes a and b are valid ETags.
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func etagStrongMatch(a, b string) bool { |
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return a == b && a != "" && a[0] == '"' |
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} |
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// etagWeakMatch reports whether a and b match using weak ETag comparison.
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// Assumes a and b are valid ETags.
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func etagWeakMatch(a, b string) bool { |
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return strings.TrimPrefix(a, "W/") == strings.TrimPrefix(b, "W/") |
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} |
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// condResult is the result of an HTTP request precondition check.
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// See https://tools.ietf.org/html/rfc7232 section 3.
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type condResult int |
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const ( |
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condNone condResult = iota |
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condTrue |
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condFalse |
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) |
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func checkIfMatch(w http.ResponseWriter, r *http.Request) condResult { |
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im := r.Header.Get("If-Match") |
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if im == "" { |
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return condNone |
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} |
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for { |
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im = textproto.TrimString(im) |
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if len(im) == 0 { |
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break |
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} |
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if im[0] == ',' { |
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im = im[1:] |
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continue |
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} |
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if im[0] == '*' { |
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return condTrue |
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} |
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etag, remain := scanETag(im) |
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if etag == "" { |
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break |
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} |
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if etagStrongMatch(etag, w.Header().Get("Etag")) { |
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return condTrue |
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} |
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im = remain |
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} |
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return condFalse |
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} |
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func checkIfUnmodifiedSince(r *http.Request, modtime time.Time) condResult { |
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ius := r.Header.Get("If-Unmodified-Since") |
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if ius == "" || isZeroTime(modtime) { |
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return condNone |
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} |
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if t, err := http.ParseTime(ius); err == nil { |
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// The Date-Modified header truncates sub-second precision, so
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// use mtime < t+1s instead of mtime <= t to check for unmodified.
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if modtime.Before(t.Add(1 * time.Second)) { |
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return condTrue |
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} |
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return condFalse |
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} |
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return condNone |
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} |
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func checkIfNoneMatch(w http.ResponseWriter, r *http.Request) condResult { |
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inm := r.Header.Get("If-None-Match") |
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if inm == "" { |
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return condNone |
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} |
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buf := inm |
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for { |
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buf = textproto.TrimString(buf) |
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if len(buf) == 0 { |
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break |
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} |
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if buf[0] == ',' { |
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buf = buf[1:] |
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} |
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if buf[0] == '*' { |
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return condFalse |
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} |
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etag, remain := scanETag(buf) |
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if etag == "" { |
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break |
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} |
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if etagWeakMatch(etag, w.Header().Get("Etag")) { |
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return condFalse |
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} |
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buf = remain |
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} |
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return condTrue |
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} |
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func checkIfModifiedSince(r *http.Request, modtime time.Time) condResult { |
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if r.Method != "GET" && r.Method != "HEAD" { |
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return condNone |
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} |
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ims := r.Header.Get("If-Modified-Since") |
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if ims == "" || isZeroTime(modtime) { |
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return condNone |
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} |
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t, err := http.ParseTime(ims) |
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if err != nil { |
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return condNone |
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} |
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// The Date-Modified header truncates sub-second precision, so
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// use mtime < t+1s instead of mtime <= t to check for unmodified.
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if modtime.Before(t.Add(1 * time.Second)) { |
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return condFalse |
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} |
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return condTrue |
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} |
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var unixEpochTime = time.Unix(0, 0) |
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// isZeroTime reports whether t is obviously unspecified (either zero or Unix()=0).
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func isZeroTime(t time.Time) bool { |
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return t.IsZero() || t.Equal(unixEpochTime) |
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} |
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func setLastModified(w http.ResponseWriter, modtime time.Time) { |
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if !isZeroTime(modtime) { |
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w.Header().Set("Last-Modified", modtime.UTC().Format(http.TimeFormat)) |
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} |
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} |
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func writeNotModified(w http.ResponseWriter) { |
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// RFC 7232 section 4.1:
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// a sender SHOULD NOT generate representation metadata other than the
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// above listed fields unless said metadata exists for the purpose of
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// guiding cache updates (e.g., Last-Modified might be useful if the
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// response does not have an ETag field).
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h := w.Header() |
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delete(h, "Content-Type") |
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delete(h, "Content-Length") |
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if h.Get("Etag") != "" { |
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delete(h, "Last-Modified") |
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} |
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w.WriteHeader(http.StatusNotModified) |
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} |
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// CheckPreconditions evaluates request preconditions and reports whether a precondition
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// resulted in sending StatusNotModified or StatusPreconditionFailed.
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func CheckPreconditions(w http.ResponseWriter, r *http.Request, modtime time.Time) (done bool) { |
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// This function carefully follows RFC 7232 section 6.
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ch := checkIfMatch(w, r) |
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if ch == condNone { |
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ch = checkIfUnmodifiedSince(r, modtime) |
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} |
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if ch == condFalse { |
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w.WriteHeader(http.StatusPreconditionFailed) |
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return true |
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} |
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switch checkIfNoneMatch(w, r) { |
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case condFalse: |
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if r.Method == "GET" || r.Method == "HEAD" { |
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writeNotModified(w) |
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return true |
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} else { |
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w.WriteHeader(http.StatusPreconditionFailed) |
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return true |
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} |
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case condNone: |
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if checkIfModifiedSince(r, modtime) == condFalse { |
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writeNotModified(w) |
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return true |
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} |
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} |
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return false |
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} |
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