Lots of work on debugging diff xmit

luprex/core/cpp/debugcollector.hpp

@@ -0,0 +1,50 @@
+#ifndef DEBUGCOLLECTOR_HPP
+#define DEBUGCOLLECTOR_HPP
+
+#include <vector>
+#include <string>
+#include <memory>
+#include <ostream>
+#include <sstream>
+
+class DebugCollector {
+private:
+    // At any given time, the stringstream may contain one
+    // extra line that hasn't yet been appended to the list of lines.
+    // The flag 'need_flush_' is true if the stringstream contains
+    // an extra line.  In that case, is_regular_ indicates whether
+    // the extra line is a header or a regular line.
+    std::vector<std::string> lines_;
+    std::vector<std::string> targets_;
+    int n_regular_;
+    bool need_flush_;
+    bool is_regular_;
+    bool active_;
+    void flush();
+    bool use(const char *target);
+public:
+    std::ostringstream oss_;
+    DebugCollector();
+    DebugCollector(const std::string &targets);
+    bool do_header();
+    bool do_line();
+    void dump(std::ostream &os);
+    friend class DebugBlock;
+};
+
+class DebugBlock {
+private:
+    DebugCollector *dbc_;
+    int n_regular_;
+    size_t n_lines_;
+    bool active_;
+public:
+    DebugBlock(DebugCollector *dbc, const char *target);
+    ~DebugBlock();
+};
+
+#define DebugHeader(dbc) if (((dbc)!=nullptr) && (dbc)->do_header()) ((dbc)->oss_)
+#define DebugLine(dbc) if (((dbc)!=nullptr) && (dbc)->do_line()) ((dbc)->oss_)
+
+#endif // DEBUGCOLLECTOR_HPP
+