add Ruby bootstrapping code

src/main.cc

@@ -1,4 +1,77 @@
+#include <ruby.h>
+#include <string>
+#include <stdio.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+VALUE svi_ruby_protect_eval_string_rescue(VALUE exception, VALUE exception_object)
+{
+    *(bool *)exception = true;
+    fprintf(stderr, "Unhandled exception: %s\n",
+            rb_obj_classname(exception_object));
+    return Qnil;
+}
+
+VALUE ruby_protect_eval_string(const char * ruby_expression, bool * exception)
+{
+    *exception = false;
+    return rb_rescue((VALUE(*)(...))rb_eval_string, (VALUE)ruby_expression,
+            (VALUE(*)(...))svi_ruby_protect_eval_string_rescue, (VALUE)exception);
+}
+
+static char * read_file(const char * filename)
+{
+    int fd = ::open(filename, O_RDONLY, 0);
+    if (fd < 0)
+    {
+        return nullptr;
+    }
+    off_t size = ::lseek(fd, 0, SEEK_END);
+    if (size <= 0)
+    {
+        return nullptr;
+    }
+    ::lseek(fd, 0, SEEK_SET);
+    char * buffer = new char[size];
+    off_t n_bytes_read = 0u;
+    for (;;)
+    {
+        off_t rd_size = ::read(fd, &buffer[n_bytes_read], size - n_bytes_read);
+        if (rd_size <= 0)
+            break;
+        n_bytes_read += rd_size;
+        if (n_bytes_read >= size)
+            break;
+    }
+    ::close(fd);
+    if (n_bytes_read == size)
+    {
+        return buffer;
+    }
+    else
+    {
+        delete[] buffer;
+        return nullptr;
+    }
+}
+
 int main(int argc, char * argv[])
 {
-    return 0;
+    static const char * ruby_startup_file = SHARE_DIR "/svi.rb";
+    bool exception = false;
+    char * ruby_startup = read_file(ruby_startup_file);
+    if (ruby_startup == nullptr)
+    {
+        fprintf(stderr, "Error opening %s\n", ruby_startup_file);
+        return 1;
+    }
+    {
+        RUBY_INIT_STACK;
+        ruby_init();
+        ruby_protect_eval_string(ruby_startup, &exception);
+    }
+    delete[] ruby_startup;
+    return exception ? 1 : 0;
 }