net: add CVectorWriter and CNetMsgMaker

CVectorWriter is useful for overwriting or appending an existing byte vector. CNetMsgMaker is a shortcut for creating messages on-the-fly which are suitable for pushing to CConnman. (cherry picked from commit 2ec935d)
zingolabs · Oct 14, 2021 · 878e63c · 878e63c
1 parent 5c34bff
commit 878e63c
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Showing 5 changed files with 178 additions and 2 deletions.
diff --git a/src/Makefile.am b/src/Makefile.am
@@ -175,6 +175,7 @@ BITCOIN_CORE_H = \
   net.h \
   netaddress.h \
   netbase.h \
+  netmessagemaker.h \
   noui.h \
   policy/fees.h \
   policy/policy.h \

diff --git a/src/net.h b/src/net.h
@@ -23,6 +23,7 @@
 #include <atomic>
 #include <deque>
 #include <stdint.h>
+#include <vector>
 
 #ifndef WIN32
 #include <arpa/inet.h>
@@ -214,8 +215,18 @@ class CNodeStats
     std::string addrLocal;
 };
 
-
-
+struct CSerializedNetMsg
+{
+    CSerializedNetMsg() = default;
+    CSerializedNetMsg(CSerializedNetMsg&&) = default;
+    CSerializedNetMsg& operator=(CSerializedNetMsg&&) = default;
+    // No copying, only moves.
+    CSerializedNetMsg(const CSerializedNetMsg& msg) = delete;
+    CSerializedNetMsg& operator=(const CSerializedNetMsg&) = delete;
+
+    std::vector<unsigned char> data;
+    std::string command;
+};
 
 class CNetMessage {
 public:

diff --git a/src/netmessagemaker.h b/src/netmessagemaker.h
@@ -0,0 +1,36 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2016 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_NETMESSAGEMAKER_H
+#define BITCOIN_NETMESSAGEMAKER_H
+
+#include "net.h"
+#include "serialize.h"
+
+class CNetMsgMaker
+{
+public:
+    CNetMsgMaker(int nVersionIn) : nVersion(nVersionIn){}
+
+    template <typename... Args>
+    CSerializedNetMsg Make(int nFlags, std::string sCommand, Args&&... args)
+    {
+        CSerializedNetMsg msg;
+        msg.command = std::move(sCommand);
+        CVectorWriter{ SER_NETWORK, nFlags | nVersion, msg.data, 0, std::forward<Args>(args)... };
+        return msg;
+    }
+
+    template <typename... Args>
+    CSerializedNetMsg Make(std::string sCommand, Args&&... args)
+    {
+        return Make(0, std::move(sCommand), std::forward<Args>(args)...);
+    }
+
+private:
+    const int nVersion;
+};
+
+#endif // BITCOIN_NETMESSAGEMAKER_H
diff --git a/src/streams.h b/src/streams.h
@@ -115,6 +115,75 @@ OverrideStream<S> WithVersion(S* s, int nVersion)
     return OverrideStream<S>(s, s->GetType(), nVersion);
 }
 
+/* Minimal stream for overwriting and/or appending to an existing byte vector
+ *
+ * The referenced vector will grow as necessary
+ */
+class CVectorWriter
+{
+ public:
+
+/*
+ * @param[in]  nTypeIn Serialization Type
+ * @param[in]  nVersionIn Serialization Version (including any flags)
+ * @param[in]  vchDataIn  Referenced byte vector to overwrite/append
+ * @param[in]  nPosIn Starting position. Vector index where writes should start. The vector will initially
+ *                    grow as necessary to  max(index, vec.size()). So to append, use vec.size().
+*/
+    CVectorWriter(int nTypeIn, int nVersionIn, std::vector<unsigned char>& vchDataIn, size_t nPosIn) : nType(nTypeIn), nVersion(nVersionIn), vchData(vchDataIn), nPos(nPosIn)
+    {
+        if(nPos > vchData.size())
+            vchData.resize(nPos);
+    }
+/*
+ * (other params same as above)
+ * @param[in]  args  A list of items to serialize starting at nPos.
+*/
+    template <typename... Args>
+    CVectorWriter(int nTypeIn, int nVersionIn, std::vector<unsigned char>& vchDataIn, size_t nPosIn, Args&&... args) : CVectorWriter(nTypeIn, nVersionIn, vchDataIn, nPosIn)
+    {
+        ::SerializeMany(*this, std::forward<Args>(args)...);
+    }
+    void write(const char* pch, size_t nSize)
+    {
+        assert(nPos <= vchData.size());
+        size_t nOverwrite = std::min(nSize, vchData.size() - nPos);
+        if (nOverwrite) {
+            memcpy(vchData.data() + nPos, reinterpret_cast<const unsigned char*>(pch), nOverwrite);
+        }
+        if (nOverwrite < nSize) {
+            vchData.insert(vchData.end(), reinterpret_cast<const unsigned char*>(pch) + nOverwrite, reinterpret_cast<const unsigned char*>(pch) + nSize);
+        }
+        nPos += nSize;
+    }
+    template<typename T>
+    CVectorWriter& operator<<(const T& obj)
+    {
+        // Serialize to this stream
+        ::Serialize(*this, obj);
+        return (*this);
+    }
+    int GetVersion() const
+    {
+        return nVersion;
+    }
+    int GetType() const
+    {
+        return nType;
+    }
+    void seek(size_t nSize)
+    {
+        nPos += nSize;
+        if(nPos > vchData.size())
+            vchData.resize(nPos);
+    }
+private:
+    const int nType;
+    const int nVersion;
+    std::vector<unsigned char>& vchData;
+    size_t nPos;
+};
+
 /** Double ended buffer combining vector and stream-like interfaces.
  *
  * >> and << read and write unformatted data using the above serialization templates.

diff --git a/src/test/streams_tests.cpp b/src/test/streams_tests.cpp
@@ -11,6 +11,65 @@
 
 BOOST_FIXTURE_TEST_SUITE(streams_tests, TestingSetup)
 
+BOOST_AUTO_TEST_CASE(streams_vector_writer)
+{
+    unsigned char a(1);
+    unsigned char b(2);
+    unsigned char bytes[] = { 3, 4, 5, 6 };
+    std::vector<unsigned char> vch;
+
+    // Each test runs twice. Serializing a second time at the same starting
+    // point should yield the same results, even if the first test grew the
+    // vector.
+
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 0, a, b);
+    BOOST_CHECK((vch == std::vector<unsigned char>{{1, 2}}));
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 0, a, b);
+    BOOST_CHECK((vch == std::vector<unsigned char>{{1, 2}}));
+    vch.clear();
+
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 2, a, b);
+    BOOST_CHECK((vch == std::vector<unsigned char>{{0, 0, 1, 2}}));
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 2, a, b);
+    BOOST_CHECK((vch == std::vector<unsigned char>{{0, 0, 1, 2}}));
+    vch.clear();
+
+    vch.resize(5, 0);
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 2, a, b);
+    BOOST_CHECK((vch == std::vector<unsigned char>{{0, 0, 1, 2, 0}}));
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 2, a, b);
+    BOOST_CHECK((vch == std::vector<unsigned char>{{0, 0, 1, 2, 0}}));
+    vch.clear();
+
+    vch.resize(4, 0);
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 3, a, b);
+    BOOST_CHECK((vch == std::vector<unsigned char>{{0, 0, 0, 1, 2}}));
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 3, a, b);
+    BOOST_CHECK((vch == std::vector<unsigned char>{{0, 0, 0, 1, 2}}));
+    vch.clear();
+
+    vch.resize(4, 0);
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 4, a, b);
+    BOOST_CHECK((vch == std::vector<unsigned char>{{0, 0, 0, 0, 1, 2}}));
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 4, a, b);
+    BOOST_CHECK((vch == std::vector<unsigned char>{{0, 0, 0, 0, 1, 2}}));
+    vch.clear();
+
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 0, FLATDATA(bytes));
+    BOOST_CHECK((vch == std::vector<unsigned char>{{3, 4, 5, 6}}));
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 0, FLATDATA(bytes));
+    BOOST_CHECK((vch == std::vector<unsigned char>{{3, 4, 5, 6}}));
+    vch.clear();
+
+    vch.resize(4, 8);
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 2, a, FLATDATA(bytes), b);
+    BOOST_CHECK((vch == std::vector<unsigned char>{{8, 8, 1, 3, 4, 5, 6, 2}}));
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 2, a, FLATDATA(bytes), b);
+    BOOST_CHECK((vch == std::vector<unsigned char>{{8, 8, 1, 3, 4, 5, 6, 2}}));
+    vch.clear();
+}
+
+
 BOOST_AUTO_TEST_CASE(streams_buffered_file)
 {
     FILE* file = fopen("streams_test_tmp", "w+b");