Circbuf for write buffer

Wiebe Cazemier
1 parent ae95e6dc
Showing 4 changed files with 49 additions and 78 deletions
cirbuf.cpp
cirbuf.h
client.cpp
client.h
@@ -25,13 +25,13 @@ CirBuf::~CirBuf()
         free(buf);
 }
-int CirBuf::usedBytes() const
+uint CirBuf::usedBytes() const
 {
     int result = (head - tail) & (size-1);
     return result;
 }
-int CirBuf::freeSpace() const
+uint CirBuf::freeSpace() const
 {
     int result = (tail - (head + 1)) & (size-1);
     return result;
@@ -99,7 +99,7 @@ void CirBuf::doubleSize()
     head = tail + usedBytes();
     size = newSize;
-    std::cout << "New read buf size: " << size << std::endl;
+    std::cout << "New buf size: " << size << std::endl;
 #ifdef TESTING
     memset(&buf[head], 5, maxWriteSize() + 2);
@@ -20,8 +20,8 @@ public:
     CirBuf(size_t size);
     ~CirBuf();
-    int usedBytes() const;
-    int freeSpace() const;
+    uint usedBytes() const;
+    uint freeSpace() const;
     int maxWriteSize() const;
     int maxReadSize() const;
     char *headPtr();
@@ -8,24 +8,16 @@
 Client::Client(int fd, ThreadData_p threadData) :
     fd(fd),
     readbuf(CLIENT_BUFFER_SIZE),
+    writebuf(CLIENT_BUFFER_SIZE),
     threadData(threadData)
 {
     int flags = fcntl(fd, F_GETFL);
     fcntl(fd, F_SETFL, flags | O_NONBLOCK);
-    char *writebuf = (char*)malloc(CLIENT_BUFFER_SIZE);
-
-    if (writebuf == NULL)
-    {
-        throw std::runtime_error("Malloc error constructing client.");
-    }
-
-    this->writebuf = writebuf;
 }
 Client::~Client()
 {
     close(fd);
-    free(writebuf);
 }
 // Do this from a place you'll know ownwership of the shared_ptr is being given up everywhere, so the close happens when the last owner gives it up.
@@ -89,25 +81,44 @@ void Client::writeMqttPacket(const MqttPacket &amp;packet)
 {
     std::lock_guard<std::mutex> locker(writeBufMutex);
-    if (packet.packetType == PacketType::PUBLISH && wwi > CLIENT_MAX_BUFFER_SIZE)
-        return;
-
-    if (packet.getSizeIncludingNonPresentHeader() > getWriteBufMaxWriteSize())
-        growWriteBuffer(packet.getSizeIncludingNonPresentHeader());
+    if (packet.getSizeIncludingNonPresentHeader() > writebuf.freeSpace())
+    {
+        if (packet.packetType == PacketType::PUBLISH && writebuf.getSize() >= CLIENT_MAX_BUFFER_SIZE)
+            return;
+        writebuf.doubleSize();
+    }
     if (!packet.containsFixedHeader())
     {
-        writebuf[wwi++] = packet.getFirstByte();
+        writebuf.headPtr()[0] = packet.getFirstByte();
+        writebuf.advanceHead(1);
         RemainingLength r = packet.getRemainingLength();
-        std::memcpy(&writebuf[wwi], r.bytes, r.len);
-        wwi += r.len;
-    }
-    std::memcpy(&writebuf[wwi], &packet.getBites()[0], packet.getBites().size());
-    wwi += packet.getBites().size();
+        ssize_t len_left = r.len;
+        int src_i = 0;
+        while (len_left > 0)
+        {
+            const size_t len = std::min<int>(len_left, writebuf.maxWriteSize());
+            std::memcpy(writebuf.headPtr(), &r.bytes[src_i], len);
+            writebuf.advanceHead(len);
+            src_i += len;
+            len_left -= len;
+        }
+        assert(len_left == 0);
+        assert(src_i == r.len);
+    }
-    assert(wwi >= static_cast<int>(packet.getSizeIncludingNonPresentHeader()));
-    assert(wwi <= static_cast<int>(writeBufsize));
+    ssize_t len_left = packet.getBites().size();
+    int src_i = 0;
+    while (len_left > 0)
+    {
+        const size_t len = std::min<int>(len_left, writebuf.maxWriteSize());
+        std::memcpy(writebuf.headPtr(), &packet.getBites()[src_i], len);
+        writebuf.advanceHead(len);
+        src_i += len;
+        len_left -= len;
+    }
+    assert(len_left == 0);
     if (packet.packetType == PacketType::DISCONNECT)
         setReadyForDisconnect();
@@ -135,11 +146,13 @@ void Client::writePingResp()
     std::cout << "Sending ping response to " << repr() << std::endl;
-    if (2 > getWriteBufMaxWriteSize())
-        growWriteBuffer(CLIENT_BUFFER_SIZE);
+    if (2 > writebuf.freeSpace())
+        writebuf.doubleSize();
-    writebuf[wwi++] = 0b11010000;
-    writebuf[wwi++] = 0;
+    writebuf.headPtr()[0] = 0b11010000;
+    writebuf.advanceHead(1);
+    writebuf.headPtr()[0] = 0;
+    writebuf.advanceHead(1);
     setReadyForWriting(true);
 }
@@ -155,10 +168,10 @@ bool Client::writeBufIntoFd()
         return false;
     int n;
-    while ((n = write(fd, &writebuf[wri], getWriteBufBytesUsed())) != 0)
+    while ((n = write(fd, writebuf.tailPtr(), writebuf.maxReadSize())) != 0)
     {
         if (n > 0)
-            wri += n;
+            writebuf.advanceTail(n);
         if (n < 0)
         {
             if (errno == EINTR)
@@ -170,13 +183,7 @@ bool Client::writeBufIntoFd()
         }
     }
-    if (wri == wwi)
-    {
-        wri = 0;
-        wwi = 0;
-
-        setReadyForWriting(false);
-    }
+    setReadyForWriting(writebuf.usedBytes() > 0);
     return true;
 }
@@ -189,24 +196,6 @@ std::string Client::repr()
     return a.str();
 }
-void Client::growWriteBuffer(size_t add_size)
-{
-    if (add_size == 0)
-        return;
-
-    const size_t grow_by = std::max<size_t>(add_size, writeBufsize*2);
-    const size_t newBufSize = writeBufsize + grow_by;
-    char *writebuf = (char*)realloc(this->writebuf, newBufSize);
-
-    if (writebuf == NULL)
-        throw std::runtime_error("Memory allocation failure in growWriteBuffer()");
-
-    this->writebuf = writebuf;
-    writeBufsize = newBufSize;
-
-    std::cout << "New write buf size: " << writeBufsize << std::endl;
-}
-
 void Client::setReadyForWriting(bool val)
 {
     if (disconnecting)
@@ -25,10 +25,7 @@ class Client
     CirBuf readbuf;
-    char *writebuf = NULL; // With many clients, it may not be smart to keep a (big) buffer around.
-    size_t writeBufsize = CLIENT_BUFFER_SIZE;
-    int wwi = 0;
-    int wri = 0;
+    CirBuf writebuf;
     bool authenticated = false;
     bool connectPacketSeen = false;
@@ -50,21 +47,6 @@ class Client
     std::mutex writeBufMutex;
-    size_t getWriteBufMaxWriteSize()
-    {
-        size_t available = writeBufsize - wwi;
-        return available;
-    }
-
-    // Note: this is not the inverse of free space, because there can be non-used lead-in in the buffer!
-    size_t getWriteBufBytesUsed()
-    {
-        return wwi - wri;
-    };
-
-    void growWriteBuffer(size_t add_size);
-
-
     void setReadyForWriting(bool val);
     void setReadyForReading(bool val);
@@ -90,7 +72,7 @@ public:
     void writeMqttPacket(const MqttPacket &packet);
     void writeMqttPacketAndBlameThisClient(const MqttPacket &packet);
     bool writeBufIntoFd();
-    bool readyForDisconnecting() const { return disconnectWhenBytesWritten && wwi == wri && wwi == 0; }
+    bool readyForDisconnecting() const { return disconnectWhenBytesWritten && writebuf.usedBytes() == 0; }
     // Do this before calling an action that makes this client ready for writing, so that the EPOLLOUT will handle it.
     void setReadyForDisconnect() { disconnectWhenBytesWritten = true; }