00001 /******************************************************************************* 00002 00003 @file ProtocolReader.d 00004 00005 Copyright (C) 2004 Kris Bell 00006 00007 This software is provided 'as-is', without any express or implied 00008 warranty. In no event will the authors be held liable for damages 00009 of any kind arising from the use of this software. 00010 00011 Permission is hereby granted to anyone to use this software for any 00012 purpose, including commercial applications, and to alter it and/or 00013 redistribute it freely, subject to the following restrictions: 00014 00015 1. The origin of this software must not be misrepresented; you must 00016 not claim that you wrote the original software. If you use this 00017 software in a product, an acknowledgment within documentation of 00018 said product would be appreciated but is not required. 00019 00020 2. Altered source versions must be plainly marked as such, and must 00021 not be misrepresented as being the original software. 00022 00023 3. This notice may not be removed or altered from any distribution 00024 of the source. 00025 00026 00027 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 00028 00029 00030 @version Initial version, July 2004 00031 @author Kris 00032 00033 00034 *******************************************************************************/ 00035 00036 module mango.cluster.qos.socket.ProtocolReader; 00037 00038 private import mango.io.Exception, 00039 mango.io.PickleReader, 00040 mango.io.EndianReader; 00041 00042 private import mango.cluster.model.ICluster; 00043 00044 /******************************************************************************* 00045 00046 Objects passed around a cluster are prefixed with a header, so the 00047 receiver can pick them apart correctly. This header consists of: 00048 00049 - the packet size, including the header (16 bits) 00050 - a command code (8 bits) 00051 - the length of the channel name (8 bits) 00052 - the channel name 00053 - the payload (an IPickle class) 00054 00055 Everything is written in Network order (big endian). 00056 00057 *******************************************************************************/ 00058 00059 class ProtocolReader : PickleReader 00060 { 00061 /*********************************************************************** 00062 00063 Construct a ProtocolReader upon the given buffer. As 00064 Objects are serialized, their content is written to this 00065 buffer. The buffer content is then typically flushed to 00066 some external conduit, such as a file or socket. 00067 00068 Note that serialized data is always in Network order. 00069 00070 ***********************************************************************/ 00071 00072 this (IBuffer buffer) 00073 in { 00074 assert (buffer); 00075 } 00076 body 00077 { 00078 super (buffer); 00079 } 00080 00081 /*********************************************************************** 00082 00083 Return the payload if there was one, null otherwise. 00084 00085 ***********************************************************************/ 00086 00087 IPayload getPayload (inout char[] channel, inout char[] element, inout ubyte cmd) 00088 { 00089 int position = buffer.getPosition; 00090 00091 ushort size; 00092 ubyte versn; 00093 00094 get (size); 00095 get (cmd); 00096 get (versn); 00097 00098 // avoid allocation for these two strings 00099 get (channel); 00100 get (element); 00101 00102 // is there a payload attached? 00103 if (size > (buffer.getPosition - position)) 00104 return cast(IPayload) thaw (); 00105 00106 return null; 00107 } 00108 00109 /*********************************************************************** 00110 00111 Return a duplicated slice of the buffer representing the 00112 recieved payload. This is a bit of a hack, but eliminates 00113 a reasonable amount of overhead. Note that the channel/key 00114 text is retained right at the start of the buffer, allowing 00115 the writer to toss the whole thing back without any further 00116 munging. 00117 00118 ***********************************************************************/ 00119 00120 ClusterContent getPacket (inout char[] channel, inout char[] element, inout ubyte cmd) 00121 { 00122 ushort size; 00123 ubyte versn; 00124 00125 // load up the length first. 00126 get (size); 00127 //printf ("size: %d\n", cast(int) size); 00128 00129 // read the header 00130 get (cmd); 00131 00132 // read the version stamp 00133 get (versn); 00134 00135 // subtract header size 00136 size -= buffer.getPosition; 00137 00138 if (buffer.get (size, false) is null) 00139 throw new IOException ("payload too large to fit within buffer"); 00140 00141 // duplicate the remaining packet (with channel/key text) 00142 ClusterContent content = cast(ClusterContent) buffer.toString().dup; 00143 00144 // get a slice upon the channel name. Note this is 00145 // dup'd as part of the payload 00146 get (channel); 00147 00148 // get a slice upon the element name. Note this is 00149 // dup'd as part of the payload 00150 get (element); 00151 00152 // return the dup'd payload (including channel/key text) 00153 return content; 00154 } 00155 } 00156