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Reference Guide
MPSendRecv.cxx
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1/* @(#)root/multiproc:$Id$ */
2// Author: Enrico Guiraud July 2015
3
4/*************************************************************************
5 * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers. *
6 * All rights reserved. *
7 * *
8 * For the licensing terms see $ROOTSYS/LICENSE. *
9 * For the list of contributors see $ROOTSYS/README/CREDITS. *
10 *************************************************************************/
11
12#include "MPSendRecv.h"
13#include "TBufferFile.h"
14#include "MPCode.h"
15#include <memory> //unique_ptr
16
17//////////////////////////////////////////////////////////////////////////
18/// Send a message with the specified code on the specified socket.
19/// This standalone function can be used to send a code
20/// on a given socket. It does not check whether the socket connection is
21/// in a valid state. The message code can then be retrieved via MPRecv().\n
22/// **Note:** only objects the headers of which have been parsed by
23/// cling can be sent by MPSend(). User-defined types can be made available to
24/// cling via a call like `gSystem->ProcessLine("#include \"header.h\"")`.
25/// Pointer types are not supported (with the exception of const char*),
26/// but the user can simply dereference the pointer and send the
27/// pointed object instead.\n
28/// **Note:** for readability, codes should be enumerated as in EMPCode.\n
29/// \param s a pointer to a valid TSocket. No validity checks are performed\n
30/// \param code the code to be sent
31/// \return the number of bytes sent, as per TSocket::SendRaw
32int MPSend(TSocket *s, unsigned code)
33{
35 wBuf.WriteUInt(code);
36 wBuf.WriteULong(0);
37 return s->SendRaw(wBuf.Buffer(), wBuf.Length());
38}
39
40
41//////////////////////////////////////////////////////////////////////////
42/// Receive message from a socket.
43/// This standalone function can be used to read a message that
44/// has been sent via MPSend(). The smart pointer contained in the returned
45/// ::MPCodeBufPair is null if the message does not contain an object,
46/// otherwise it points to a TBufferFile.
47/// To retrieve the object from the buffer different methods must be used
48/// depending on the type of the object to be read:\n
49/// * non-pointer built-in types: TBufferFile::operator>> must be used\n
50/// * c-strings: TBufferFile::ReadString must be used\n
51/// * class types: TBufferFile::ReadObjectAny must be used\n
52/// \param s a pointer to a valid TSocket. No validity checks are performed\n
53/// \return ::MPCodeBufPair, i.e. an std::pair containing message code and (possibly) object
55{
56 char *rawbuf = new char[sizeof(UInt_t)];
57 //receive message code
58 unsigned nBytes = s->RecvRaw(rawbuf, sizeof(UInt_t));
59 if (nBytes == 0) {
60 return std::make_pair(MPCode::kRecvError, nullptr);
61 }
62 //read message code
63 TBufferFile bufReader(TBuffer::kRead, sizeof(UInt_t), rawbuf, false);
64 unsigned code;
65 bufReader.ReadUInt(code);
66 delete [] rawbuf;
67
68 //receive object size
69 //ULong_t is sent as 8 bytes irrespective of the size of the type
70 rawbuf = new char[8];
71 s->RecvRaw(rawbuf, 8);
72 bufReader.SetBuffer(rawbuf, 8, false);
73 ULong_t classBufSize;
74 bufReader.ReadULong(classBufSize);
75 delete [] rawbuf;
76
77 //receive object if needed
78 std::unique_ptr<TBufferFile> objBuf; //defaults to nullptr
79 if (classBufSize != 0) {
80 char *classBuf = new char[classBufSize];
81 s->RecvRaw(classBuf, classBufSize);
82 objBuf.reset(new TBufferFile(TBuffer::kRead, classBufSize, classBuf, true)); //the buffer is deleted by TBuffer's dtor
83 }
84
85 return std::make_pair(code, std::move(objBuf));
86}
MPCodeBufPair MPRecv(TSocket *s)
Receive message from a socket.
Definition: MPSendRecv.cxx:54
int MPSend(TSocket *s, unsigned code)
Send a message with the specified code on the specified socket.
Definition: MPSendRecv.cxx:32
std::pair< unsigned, std::unique_ptr< TBufferFile > > MPCodeBufPair
An std::pair that wraps the code and optional object contained in a message.
Definition: MPSendRecv.h:32
unsigned int UInt_t
Definition: RtypesCore.h:46
unsigned long ULong_t
Definition: RtypesCore.h:55
The concrete implementation of TBuffer for writing/reading to/from a ROOT file or socket.
Definition: TBufferFile.h:47
void WriteUInt(UInt_t i) override
Definition: TBufferFile.h:314
void WriteULong(ULong_t l) override
Definition: TBufferFile.h:328
void ReadUInt(UInt_t &i) override
Definition: TBufferFile.h:405
void ReadULong(ULong_t &l) override
Definition: TBufferFile.h:419
@ kWrite
Definition: TBuffer.h:73
@ kRead
Definition: TBuffer.h:73
void SetBuffer(void *buf, UInt_t bufsiz=0, Bool_t adopt=kTRUE, ReAllocCharFun_t reallocfunc=0)
Sets a new buffer in an existing TBuffer object.
Definition: TBuffer.cxx:187
Int_t Length() const
Definition: TBuffer.h:100
char * Buffer() const
Definition: TBuffer.h:96
@ kRecvError
Error while reading from the socket.
Definition: MPCode.h:51
static constexpr double s