162 lines
4.2 KiB
Go
162 lines
4.2 KiB
Go
/*
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HTTP Content-Type Autonegotiation.
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The functions in this package implement the behaviour specified in
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http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
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Copyright (c) 2011, Open Knowledge Foundation Ltd.
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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 copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the
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distribution.
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Neither the name of the Open Knowledge Foundation Ltd. nor the
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names of its contributors may be used to endorse or promote
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products derived from this software without specific prior written
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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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HOLDER 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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*/
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package goautoneg
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import (
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"sort"
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"strconv"
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"strings"
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)
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// Structure to represent a clause in an HTTP Accept Header
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type Accept struct {
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Type, SubType string
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Q float64
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Params map[string]string
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}
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// For internal use, so that we can use the sort interface
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type accept_slice []Accept
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func (accept accept_slice) Len() int {
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slice := []Accept(accept)
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return len(slice)
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}
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func (accept accept_slice) Less(i, j int) bool {
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slice := []Accept(accept)
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ai, aj := slice[i], slice[j]
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if ai.Q > aj.Q {
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return true
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}
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if ai.Type != "*" && aj.Type == "*" {
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return true
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}
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if ai.SubType != "*" && aj.SubType == "*" {
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return true
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}
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return false
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}
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func (accept accept_slice) Swap(i, j int) {
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slice := []Accept(accept)
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slice[i], slice[j] = slice[j], slice[i]
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}
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// Parse an Accept Header string returning a sorted list
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// of clauses
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func ParseAccept(header string) (accept []Accept) {
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parts := strings.Split(header, ",")
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accept = make([]Accept, 0, len(parts))
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for _, part := range parts {
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part := strings.Trim(part, " ")
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a := Accept{}
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a.Params = make(map[string]string)
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a.Q = 1.0
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mrp := strings.Split(part, ";")
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media_range := mrp[0]
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sp := strings.Split(media_range, "/")
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a.Type = strings.Trim(sp[0], " ")
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switch {
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case len(sp) == 1 && a.Type == "*":
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a.SubType = "*"
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case len(sp) == 2:
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a.SubType = strings.Trim(sp[1], " ")
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default:
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continue
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}
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if len(mrp) == 1 {
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accept = append(accept, a)
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continue
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}
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for _, param := range mrp[1:] {
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sp := strings.SplitN(param, "=", 2)
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if len(sp) != 2 {
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continue
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}
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token := strings.Trim(sp[0], " ")
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if token == "q" {
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a.Q, _ = strconv.ParseFloat(sp[1], 32)
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} else {
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a.Params[token] = strings.Trim(sp[1], " ")
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}
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}
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accept = append(accept, a)
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}
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slice := accept_slice(accept)
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sort.Sort(slice)
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return
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}
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// Negotiate the most appropriate content_type given the accept header
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// and a list of alternatives.
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func Negotiate(header string, alternatives []string) (content_type string) {
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asp := make([][]string, 0, len(alternatives))
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for _, ctype := range alternatives {
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asp = append(asp, strings.SplitN(ctype, "/", 2))
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}
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for _, clause := range ParseAccept(header) {
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for i, ctsp := range asp {
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if clause.Type == ctsp[0] && clause.SubType == ctsp[1] {
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content_type = alternatives[i]
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return
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}
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if clause.Type == ctsp[0] && clause.SubType == "*" {
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content_type = alternatives[i]
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return
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}
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if clause.Type == "*" && clause.SubType == "*" {
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content_type = alternatives[i]
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return
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}
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}
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}
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return
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}
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