Print heap histogram

Also:
* Avoid unhelpful compiler warnings
* Capture common code in a macro

Note: it would have been nice to alias the closure type, but
rust-lang/rfcs#1733 is not yet implemented and macros
can't cope (rust-lang/rust#24010).

src/agentcontroller/controller.rs

@@ -15,6 +15,7 @@
  */
 
 pub struct AgentController<'a> {
+    #[allow(dead_code)] // TODO: revisit this once port is complete
     jvmti: ::env::JvmTiEnv,
     heuristic: Box<super::Heuristic + 'a>,
     actions: Vec<Box<super::Action>>
@@ -126,9 +127,9 @@ mod tests {
         ac.on_oom(dummy_jni_env(), 0);
     }
 
-    unsafe extern "C" fn test_get_env(vm: *mut ::jvmti::JavaVM,
-                                      penv: *mut *mut ::std::os::raw::c_void,
-                                      version: ::jvmti::jint)
+    unsafe extern "C" fn test_get_env(_: *mut ::jvmti::JavaVM,
+                                      _: *mut *mut ::std::os::raw::c_void,
+                                      _: ::jvmti::jint)
                                       -> ::jvmti::jint {
         0
     }

src/agentcontroller/heaphistogram.rs

@@ -14,19 +14,48 @@
  * limitations under the License.
  */
 
+use env::JvmTI;
+use std::io::Write;
+use std::io::stdout;
+use heap::Tagger;
+use heap::Tag;
+use heap::Stats;
+use heap::Record;
+use heap::Print;
+
 pub struct HeapHistogram {
     jvmti: ::env::JvmTiEnv,
 }
 
 impl HeapHistogram {
-    pub fn new(jvmti: ::env::JvmTiEnv) -> Result<Self, ::jvmti::jint> {
+    pub fn new(mut jvmti: ::env::JvmTiEnv) -> Result<Self, ::jvmti::jint> {
+        jvmti.enable_object_tagging()?;
         Ok(Self {
-            jvmti: jvmti
+            jvmti: jvmti,
         })
     }
+
+    pub fn print(&self, writer: &mut Write) {
+        let mut tagger = Tagger::new();
+
+        // Tag all loaded classes so we can determine each object's class signature during heap traversal.
+        self.jvmti.tag_loaded_classes(&mut tagger);
+
+        let mut heap_stats = Stats::new();
+
+        // Traverse the live heap and add objects to the heap stats.
+        self.jvmti.traverse_live_heap(|class_tag: ::jvmti::jlong, size: ::jvmti::jlong| {
+            if let Some(sig) = tagger.class_signature(class_tag) {
+                heap_stats.recordObject(sig, size);
+            }
+        });
+
+        heap_stats.print(writer);
+    }
 }
 
 impl super::Action for HeapHistogram {
-    fn on_oom(&self, jni_env: ::env::JniEnv, resource_exhaustion_flags: ::jvmti::jint) {
+    fn on_oom(&self, _: ::env::JniEnv, _: ::jvmti::jint) {
+        self.print(&mut stdout());
     }
 }

src/agentcontroller/kill.rs

@@ -30,6 +30,7 @@ impl Kill {
         }
     }
 
+    #[cfg(test)]
     pub fn setSignal(&mut self, signal: c_int) {
         self.signal = signal;
     }
@@ -93,7 +94,7 @@ mod tests {
                                                 signal::SaFlags::empty(),
                                                 signal::SigSet::empty());
         unsafe {
-            signal::sigaction(signal::SIGUSR1, &sig_action);
+            signal::sigaction(signal::SIGUSR1, &sig_action).unwrap();
         }
     }
 }