Checkpointing.

include/messageFormat.h

@@ -13,9 +13,18 @@ namespace storagemanager
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wunused-variable"
 
-// all msgs to and from StorageManager begin with this magic
+// all msgs to and from StorageManager begin with this magic and a payload length
 static const uint SM_MSG_START=0xbf65a7e1;
 
+// for read/write/append, which may break a message into chunks, messages not the 
+// beginning or end of the larger message will preface a chunk with this magic 
+static const uint SM_MSG_CONT=0xfa371bd2;
+
+// for read/write/append, the last chunk of a message should begin with this magic
+static const uint SM_MSG_END=0x9d5bc31b;
+
+static const uint SM_HEADER_LEN = 8;
+
 // the unix socket StorageManager is listening on
 static const char *socket_name = "\0storagemanager";
 
@@ -47,6 +56,8 @@ enum Opcodes {
 
     On success, what follows is any output parameters from the call.
     
+    TBD: Require filenames to be NULL-terminated.  Currently they are not.
+
     OPEN
     ----
     command format:
@@ -66,7 +77,7 @@ enum Opcodes {
     WRITE
     -----
     command format:
-    1-byte opcode|4-byte filename length|filename|size_t count|off_t offset|data
+    1-byte opcode|size_t count|off_t offset|4-byte filename length|filename|data
 
     response format:
 

src/OpenTask.cpp

@@ -0,0 +1,47 @@
+
+
+#include "OpenTask.h"
+#include <sys/stat.h>
+
+using namespace std;
+
+namespace storagemanager
+{
+
+OpenTask::OpenTask(int sock, uint len) : PosixTask(sock, len)
+{
+}
+
+void OpenTask::run()
+{
+    /*
+        get the parameters
+        call IOManager to do the work
+        return the result
+    */
+    bool success;
+    uint8_t *buf = alloca(max(getLength(), sizeof(struct stat) + SM_HEADER_LEN));
+    
+    success = read(&buf, getLength());
+    if (!success)
+    {
+        handleError("OpenTask read", errno);
+        return;
+    }
+    
+    uint32_t flen = *((uint32_t *) &buf[0]);
+    string filename((char *) &buf[4], flen);   // might want to require filenames to be NULL-terminated for efficiency
+    int openmode = *((int *) &buf[4+flen]);
+    
+    // IOC->open(filename, openmode, &buf[SM_HEADER_LEN])
+    
+    // stand-in dummy response
+    uint32_t *buf32 = (uint32_t *) &buf[0];
+    buf32[0] = SM_MSG_START;
+    buf32[1] = sizeof(struct stat);
+    success = write(buf, sizeof(struct stat) + SM_HEADER_LEN);
+    if (!success)
+        handleError("OpenTask write", errno);
+}
+
+}

src/OpenTask.h

@@ -10,10 +10,14 @@ namespace storagemanager
 class OpenTask : public PosixTask
 {
     public:
-        OpenTask(int _sock, uint length) : PosixTask(_sock)
-        WORKING HERE
+        OpenTask(int sock, uint length);
+        virtual ~OpenTask();
         
-}
+        void run();
+    
+    private:
+        OpenTask();
+};
 
 
 }

src/PosixTask.cpp

@@ -1,56 +1,152 @@
 
 #include "PosixTask.h"
-
+#include <sys/types.h>
+#include <sys/socket.h>
 
 namespace storagemanager
 {
 
-PosixTask::PosixTask(int _sock, uint _length) : sock(_sock), remainingLength(_length)
+PosixTask::PosixTask(int _sock, uint _length) : 
+    sock(_sock),
+    totalLength(_length),
+    remainingLengthInStream(_length),
+    remainingLengthForCaller(_length),
+    bufferPos(0),
+    bufferLen(0),
+    socketReturned(false)
 {
 }
 
 PosixTask::~PosixTask()
 {
-    // return the socket
+    if (!socketReturned)
+        returnSocket();
 }
 
-void PosixTask::handleError(int errCode)
+void PosixTask::handleError(const char *name, int errCode)
 {
     char buf[80];
+    
+    // send an error response if possible
+    int32_t *buf32;
+    buf32[0] = SM_MSG_START;
+    buf32[1] = 8;
+    buf32[2] = -1;
+    buf32[3] = errCode;
+    write(buf32, 16);
+    
     // TODO: construct and log a message
-    cout << "PosixTask caught an error reading from a socket: " << strerror_r(errCode, buf, 80) << endl;
+    cout << name << " caught an error reading from a socket: " << strerror_r(errCode, buf, 80) << endl;
+    socketError();
 }
 
-/* Optimization.  Make this read larger chunks into a buffer & supply data from that when possible. */
-int PosixTask::read(vector<uint8_t> *buf, uint offset, uint length)
+void PosixTask::returnSocket()
 {
-    if (length > remainingLength)
-        length = remainingLength;
+    socketReturned = true;
+}
 
-    uint originalSize = buf->size();
-    buf->resize(originalSize + length);
+void PosixTask::socketError()
+{
+    socketReturned = true;
+}
+
+uint PosixTask::getRemainingLength()
+{
+    return remainingLengthForCaller;
+}
+
+uint PosixTask::getLength()
+{
+    return totalLength;
+}
+
+bool PosixTask::read(uint8_t *buf, uint length)
+{
+    if (length > remainingLengthForCaller)
+        length = remainingLengthForCaller;
     
     uint count = 0;
     int err;
+    
+    // copy data from the local buffer first.
+    uint dataInBuffer = bufferLen - bufferPos;
+    if (length <= dataInBuffer)
+    {
+        memcpy(buf, &localBuffer[bufferPos], length);
+        count = length;
+        bufferPos += length;
+        remainingLengthForCaller -= length;
+    }
+    else if (dataInBuffer > 0)
+    {
+        memcpy(buf, &localBuffer[bufferPos], dataInBuffer);
+        count = dataInBuffer;
+        bufferPos += dataInBuffer;
+        remainingLengthForCaller -= dataInBuffer;
+    }
+    
+    // read the remaining requested amount from the stream.
+    // ideally, combine the recv here with the recv below that refills the local
+    // buffer.
     while (count < length)
     {
-        /* TODO: need a timeout here? */
-        err = ::read(sock, &(*buf)[count + offset], length - count);
-        if (err < 0) {
-            buf->resize(originalSize);
-            handleError(errno);
-            return -1;
-        }
-        else if (err == 0) {
-            buf->resize(originalSize);
-            handleError(0);
-            return -1;
-        }
+        err = ::recv(sock, &buf[count], length - count, 0);
+        if (err <= 0)
+            return false;
+
         count += err;
-        remainingLength -= err;
+        remainingLengthInStream -= err;
+        remainingLengthForCaller -= err;
     }
-    return count;
+    
+    /* The caller's request has been satisfied here.  If there is remaining data in the stream
+    get what's available. */
+    if (remainingLengthInStream > 0)
+    {
+        // Reset the buffer to allow a larger read.
+        if (bufferLen == bufferPos)
+        {
+            bufferLen = 0;
+            bufferPos = 0;
+        }
+        else if (bufferLen - bufferPos < 1024)  // if < 1024 in the buffer, move data to the front
+        {
+            memmove(buffer, &buffer[bufferPos], bufferLen - bufferPos);
+            bufferLen -= bufferPos;
+            bufferPos = 0;
+        }
+        
+        uint toRead = min(remainingLengthInStream, bufferSize - bufferLen);
+        err = ::recv(sock, &localBuffer[bufferLen], toRead, MSG_NOBLOCK);
+        // ignoring errors here since the request has been satisfied successfully.
+        // errors will be caught by the next read
+        if (err > 0) 
+        {
+            bufferLen += err;
+            remainingLengthInStream -= err;
+        }
+    }
+    return true;
 }
 
+bool PosixTask::write(uint8_t *buf, uint len)
+{
+    int err;
+    uint count = 0;
+    
+    while (count < len)
+    {
+        err = ::write(sock, &buf[count], len - count);
+        if (err < 0)
+            return false;
+        count += err;
+    }
+    return true;
+}
+
+bool PosixTask::write(const vector<uint8_t> &buf)
+{
+    return write(&buf[0], buf.size());
+}
 
 }

src/PosixTask.h

@@ -14,19 +14,27 @@ class PosixTask
         virtual void run() = 0;
         
     protected:
-        int read(std::vector<uint8_t> *buf, uint offset, uint length);
+        int read(uint8_t *buf, uint length);
         bool write(const std::vector<uint8_t> &buf);
+        bool write(void *buf, uint length);
+        uint getLength();  // returns the total length of the msg
+        uint getRemainingLength();   // returns the remaining length from the caller's perspective
+        void handleError(const char *name, int errCode);
+        void returnSocket();
+        void socketError();
         
     private:
         PosixTask();
         
-        void handleError();
-        
         int sock;
-        uint remainingLength;
-        uint8_t buffer[4096];
+        int totalLength;
+        uint remainingLengthInStream;
+        uint remainingLengthForCaller;
+        static const uint bufferSize = 4096;
+        uint8_t localBuffer[bufferSize];
         uint bufferPos;
         uint bufferLen;
+        bool socketReturned;
 };
 
 

src/ProcessTask.cpp

@@ -34,6 +34,7 @@ void ProcessTask::operator()()
     int err;
     uint8_t opcode;
     
+    /* D'oh, a 1-byte read....   TODO! */
     err = ::read(sock, &opcode, 1);
     if (err <= 0)
     {

src/ReadTask.cpp

@@ -0,0 +1,49 @@
+
+#include "ReadTask.h"
+
+using namespace std;
+
+namespace storagemanager
+{
+
+ReadTask::ReadTask(int sock, uint len) : PosixTask(sock, len)
+{
+}
+
+ReadTask::~ReadTask()
+{
+}
+
+void ReadTask::run()
+{
+
+    // get the parameters
+    bool success;
+    uint8_t *buf = alloca(getLength());
+    int boff = 0;
+    success = read(&buf, getLength());
+    uint flen = *((uint *) &buf[0])
+    boff += 4;
+    string filename(&buf[boff], flen);
+    boff += flen;
+    size_t count = *((size_t *) &buf[boff]);
+    boff += sizeof(size_t);
+    off_t offset = *((off_t *) &buf[boff]);
+    
+    // read from IOC, write to the socket
+    vector<uint8_t> outbuf;
+    outbuf.resize(count + SM_HEADER_LEN);
+    uint32_t *outbuf32 = (uint32_t *) &outbuf[0];
+    outbuf32[0] = SM_MSG_START;
+    outbuf32[1] = length;
+    
+    // do the reading and writing in chunks
+    // IOC->willRead(filename, offset, length);
+    // IOC->read(filename, offset, length, &outbuf[SM_HEADER_LEN]);
+    
+    write(outbuf);
+}
+
+
+
+}

src/ReadTask.h

@@ -0,0 +1,24 @@
+
+
+#ifndef READTASK_H_
+#define READTASH_H_
+
+#include "PosixTask.h"
+
+namespace storagemanager
+{
+
+class ReadTask : PosixTask
+{
+    public:
+        ReadTask(int sock, uint length);
+        virtual ~ReadTask();
+        
+        void run();
+    
+    private:
+        ReadTask();
+};
+
+}
+#endif

src/WriteTask.cpp

@@ -0,0 +1,50 @@
+
+#include "WriteTask.h"
+
+using namespace std;
+
+namespace storagemanager
+{
+
+WriteTask::WriteTask(int sock, uint len) : PosixTask(sock, len)
+{
+}
+
+WriteTask::~WriteTask()
+{
+}
+
+#define check_error(msg) \
+    if (!success) \
+    { \
+        handleError(msg); \
+        return; \
+    }
+
+void WriteTask::run()
+{
+    bool success;
+    uint8_t cmdbuf[1024] = {0};
+
+    success = read(cmdbuf, sizeof(struct cmd_overlay));
+    check_error("WriteTask read");
+    cmd_overlay *cmd = cmdbuf;
+    
+    success = read(&cmdbuf[sizeof(*cmd)], min(cmd->filename_len, 1024 - sizeof(*cmd) - 1));
+    check_error("WriteTask read");
+    
+    size_t count = 0;
+    vector<uint8_t> databuf;
+    databuf.resize(cmd->count);
+    
+    // todo: do this in chunks...
+    while (count < cmd->count)
+    {
+        success = read(&databuf[count], cmd->count - count);
+        check_error("WriteTask read data");
+        count += cmd->count;
+        // IOC->write()
+    }
+}
+
+}

src/WriteTask.h

@@ -0,0 +1,31 @@
+
+
+#ifndef WRITETASK_H_
+#define WRITETASK_H_
+
+#include "PosixTask.h"
+
+namespace storagemanager
+{
+
+class WriteTask : PosixTask
+{
+    public:
+        WriteTask(int sock, uint length);
+        virtual ~WriteTask();
+        
+        void run();
+    
+    private:
+        WriteTask();
+        
+        struct cmd_overlay {
+            size_t count;
+            off_t offset;
+            uint filename_len;
+            char filename[];
+        };
+};
+
+}
+#endif