feat add dispatcher

3party/libelfin/elf/mmap_loader.cc

@@ -0,0 +1,60 @@
+// Copyright (c) 2013 Austin T. Clements. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+
+#include "elf++.hh"
+
+#include <system_error>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+using namespace std;
+
+ELFPP_BEGIN_NAMESPACE
+
+class mmap_loader : public loader
+{
+        void *base;
+        size_t lim;
+
+public:
+        mmap_loader(int fd)
+        {
+                off_t end = lseek(fd, 0, SEEK_END);
+                if (end == (off_t)-1)
+                        throw system_error(errno, system_category(),
+                                           "finding file length");
+                lim = end;
+
+                base = mmap(nullptr, lim, PROT_READ, MAP_SHARED, fd, 0);
+                if (base == MAP_FAILED)
+                        throw system_error(errno, system_category(),
+                                           "mmap'ing file");
+                close(fd);
+        }
+
+        ~mmap_loader()
+        {
+                munmap(base, lim);
+        }
+
+        const void *load(off_t offset, size_t size)
+        {
+                if (offset + size > lim)
+                        throw range_error("offset exceeds file size");
+                return (const char*)base + offset;
+        }
+};
+
+std::shared_ptr<loader>
+create_mmap_loader(int fd)
+{
+        return make_shared<mmap_loader>(fd);
+}
+
+ELFPP_END_NAMESPACE