HttpCacheVary.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / xsp / System / Web / HttpCacheVary.cs / 1 / HttpCacheVary.cs
                        

                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

/* 
 * Cache Vary class.  Wraps Vary header 
 *
 * Copyright (c) 1998 Microsoft Corporation 
 */

namespace System.Web {
    using System.Text; 
    using System.Runtime.InteropServices;
    using System.Web.Util; 
    using System.Security.Permissions; 

 
    /// 
    ///    Indicates that a cache should contain multiple
    ///       representations for a particular Uri. This class is an encapsulation that
    ///       provides a rich, type-safe way to set the Vary header. 
    /// 
    [AspNetHostingPermission(SecurityAction.LinkDemand, Level=AspNetHostingPermissionLevel.Minimal)] 
    public sealed class HttpCacheVaryByHeaders { 
        bool            _isModified;
        bool            _varyStar; 
        HttpDictionary  _headers;

        internal HttpCacheVaryByHeaders() {
            Reset(); 
        }
 
        internal void Reset() { 
            _isModified = false;
            _varyStar = false; 
            _headers = null;
        }

        /* 
         * Reset based on the cached vary headers.
         */ 
        internal void ResetFromHeaders(String[] headers) { 
            int i, n;
 
            if (headers == null) {
                _isModified = false;
                _varyStar = false;
                _headers = null; 
            }
            else { 
                _isModified = true; 
                if (headers[0].Equals("*")) {
                    Debug.Assert(headers.Length == 1, "headers.Length == 1"); 

                    _varyStar = true;
                    _headers = null;
                } 
                else {
                    _varyStar = false; 
                    _headers = new HttpDictionary(); 
                    for (i = 0, n = headers.Length; i < n; i++) {
                        _headers.SetValue(headers[i], headers[i]); 
                    }
                }
            }
        } 

        internal bool IsModified() { 
            return _isModified; 
        }
 
        /*
         * Construct header value string
         */
        internal String ToHeaderString() { 
            StringBuilder   s;
            Object          item; 
            int             i, n; 

            if (_varyStar) { 
                return "*";
            }
            else if (_headers != null) {
                s = new StringBuilder(); 

                for (i = 0, n = _headers.Size; i < n; i++) { 
                    item = _headers.GetValue(i); 
                    if (item != null) {
                        HttpCachePolicy.AppendValueToHeader(s, (String)item); 
                    }
                }

                if (s.Length > 0) 
                    return s.ToString();
            } 
 
            return null;
        } 

        /*
         * Returns the headers, for package access only.
         * 
         * @return the headers.
         */ 
        internal String[] GetHeaders() { 
            String[]    s = null;
            Object      item; 
            int         i, j, c, n;

            if (_varyStar) {
                return new String[1] {"*"}; 
            }
            else if (_headers != null) { 
                n = _headers.Size; 
                c = 0;
                for (i = 0; i < n; i++) { 
                    item = _headers.GetValue(i);
                    if (item != null) {
                        c++;
                    } 
                }
 
                if (c > 0) { 
                    s = new string[c];
                    j = 0; 
                    for (i = 0; i < n; i++) {
                        item = _headers.GetValue(i);
                        if (item != null) {
                            s[j] = (String) item; 
                            j++;
                        } 
                    } 

                    Debug.Assert(j == c, "j == c"); 
                }
            }

            return s; 
        }
 
        // 
        // Public methods and properties
        // 


        /// 
        ///    Sets the "Vary: *" header and causes all other Vary: 
        ///       header information to be dropped.
        ///  
        public void VaryByUnspecifiedParameters() { 
            _isModified = true;
            _varyStar = true; 
            _headers = null;
        }

        internal bool GetVaryByUnspecifiedParameters() { 
            return _varyStar;
        } 
 
        /*
         * Vary by accept types 
         */

        /// 
        ///    Retrieves or assigns a value indicating whether the cache should vary by Accept types. This causes the 
        ///       Vary: header to include an Accept field.
        ///  
        public bool AcceptTypes { 
            get {
                return this["Accept"]; 
            }

            set {
                _isModified = true; 
                this["Accept"] = value;
            } 
        } 

        /* 
         * Vary by accept language
         */

        ///  
        ///     Retrieves or assigns a Boolean value indicating whether
        ///       the cache should vary by user language. 
        ///  
        public bool UserLanguage {
            get { 
                return this["Accept-Language"];
            }

            set { 
                _isModified = true;
                this["Accept-Language"] = value; 
            } 
        }
 
        /*
         * Vary by user agent
         */
 
        /// 
        ///     Retrieves or assigns a Boolean value indicating whether 
        ///       the cache should vary by user agent. 
        /// 
        public bool UserAgent { 
            get {
                return this["User-Agent"];
            }
 
            set {
                _isModified = true; 
                this["User-Agent"] = value; 
            }
        } 

        /*
         * Vary by charset
         */ 

        ///  
        ///     Retrieves or assigns a value indicating whether the 
        ///       cache should vary by browser character set.
        ///  
        public bool UserCharSet {
            get {
                return this["Accept-Charset"];
            } 

            set { 
                _isModified = true; 
                this["Accept-Charset"] = value;
            } 
        }

        /*
         * Vary by a given header 
         */
 
        ///  
        ///     Default property.
        ///       Indexed property indicating that a cache should (or should not) vary according 
        ///       to a custom header.
        /// 
        public bool this[String header]
        { 
            get {
                if (header == null) { 
                    throw new ArgumentNullException("header"); 
                }
 
                if (header.Equals("*")) {
                    return _varyStar;
                }
                else { 
                    return (_headers != null && _headers.GetValue(header) != null);
                } 
            } 

            set { 
                if (header == null) {
                    throw new ArgumentNullException("header");
                }
 
                /*
                 * Since adding a Vary header is more restrictive, we don't 
                 * want components to be able to set a Vary header to false 
                 * if another component has set it to true.
                 */ 
                if (value == false) {
                    return;
                }
 
                _isModified = true;
 
                if (header.Equals("*")) { 
                    VaryByUnspecifiedParameters();
                } 
                else {
                    // set value to header if true or null if false
                    if (!_varyStar) {
                        if (_headers == null) { 
                            _headers = new HttpDictionary();
                        } 
 
                        _headers.SetValue(header, header);
                    } 
                }
            }
        }
    } 
}

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