Reogranised usr files and updated readme.

src/usr/usr.cpp

@@ -0,0 +1,78 @@
+#include <cstdio>
+#include <iostream>
+#include <unistd.h>
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include "../shared.h"
+#include "usr.h"
+
+using namespace std;
+using namespace shared;
+
+namespace usr
+{
+
+map<string, ContractUser> users;
+
+void add_user(string pubkeyb64)
+{
+    if (users.count(pubkeyb64) == 1)
+    {
+        cerr << pubkeyb64 << " already exist. Cannot add user.\n";
+        return;
+    }
+
+    int inpipe[2];
+    int outpipe[2];
+    if (pipe(inpipe) != 0 || pipe(outpipe) != 0) {
+        cerr << "User pipe creation failed. pubkey:" << pubkeyb64 << endl;
+        return;
+    }
+
+    users.insert(pair<string, ContractUser>(pubkeyb64, ContractUser(pubkeyb64, inpipe, outpipe)));
+}
+
+void remove_user(string pubkeyb64)
+{
+    if (users.count(pubkeyb64) == 0)
+    {
+        cerr << pubkeyb64 << " does not exist. Cannot remove user.\n";
+        return;
+    }
+
+    auto itr = users.find(pubkeyb64);
+    ContractUser user = itr->second;
+    close(user.inpipe[0]);
+    close(user.inpipe[1]);
+    close(user.outpipe[0]);
+    close(user.outpipe[1]);
+
+    users.erase(itr);
+}
+
+//Read per-user outputs produced by the contract process.
+int read_contract_user_outputs()
+{
+    for (auto& [pk, user] : users)
+    {
+        int fdout = user.outpipe[0];
+        int bytes_available = 0;
+        ioctl(fdout, FIONREAD, &bytes_available);
+
+        if (bytes_available > 0)
+        {
+            unsigned char data[bytes_available];
+            read(fdout, data, bytes_available);
+
+            //Replace the existing user buffer with new buffer
+            vector<unsigned char> buffer(data, data + bytes_available);
+            user.outbuffer.swap(buffer);
+
+            cout << "Read " + to_string(bytes_available) << " bytes into user output buffer. user:" + user.pubkeyb64 << endl;
+        }
+    }
+
+    return 1;
+}
+
+} // namespace usr