replace #62 with more portable nif (courtesy of @benoitc)

.gitignore

@@ -3,6 +3,7 @@ rebar3.crashdump
 _*
 .eunit
 *.o
+*.so
 *.beam
 *.plt
 *.swp

c_src/Makefile

@@ -0,0 +1,82 @@
+# Based on c_src.mk from erlang.mk by Loic Hoguin <essen@ninenines.eu>
+
+CURDIR := $(shell pwd)
+BASEDIR := $(abspath $(CURDIR)/..)
+
+PROJECT := prometheus_nif
+
+ERTS_INCLUDE_DIR ?= $(shell erl -noshell -s init stop -eval "io:format(\"~s/erts-~s/include/\", [code:root_dir(), erlang:system_info(version)]).")
+ERL_INTERFACE_INCLUDE_DIR ?= $(shell erl -noshell -s init stop -eval "io:format(\"~s\", [code:lib_dir(erl_interface, include)]).")
+ERL_INTERFACE_LIB_DIR ?= $(shell erl -noshell -s init stop -eval "io:format(\"~s\", [code:lib_dir(erl_interface, lib)]).")
+
+C_SRC_DIR = $(CURDIR)
+C_SRC_OUTPUT ?= $(CURDIR)/../priv/$(PROJECT).so
+
+# System type and C compiler/flags.
+
+UNAME_SYS := $(shell uname -s)
+ifeq ($(UNAME_SYS), Darwin)
+	CC ?= cc
+	CFLAGS ?= -O3 -std=c99 -arch x86_64 -finline-functions -Wall -Wmissing-prototypes
+	CXXFLAGS ?= -O3 -arch x86_64 -std=c++11 -finline-functions -Wall
+	LDFLAGS ?= -arch x86_64 -flat_namespace -undefined suppress
+else ifeq ($(UNAME_SYS), FreeBSD)
+	CC ?= clang
+	CXX ?= clang++
+	CFLAGS ?= -O3 -std=c99 -finline-functions -Wall -Wmissing-prototypes
+	CXXFLAGS ?= -O3 -std=c++11 -finline-functions -Wall
+else ifeq ($(UNAME_SYS), Linux)
+	CC ?= gcc
+	CXX ?= g++
+	CFLAGS ?= -O3 -std=c99 -finline-functions -Wall -Wmissing-prototypes
+	CXXFLAGS ?= -O3 -std=c++11 -finline-functions -Wall
+endif
+
+CFLAGS += -fPIC -I $(ERTS_INCLUDE_DIR) -I $(ERL_INTERFACE_INCLUDE_DIR)
+CXXFLAGS += -fPIC -I $(ERTS_INCLUDE_DIR) -I $(ERL_INTERFACE_INCLUDE_DIR) -std=c++11
+
+LDLIBS += -L $(ERL_INTERFACE_LIB_DIR) -lerl_interface -lei
+
+ifeq ($(UNAME_SYS), OpenBSD)
+	LDLIBS += -lestdc++
+else
+	LDLIBS += -lstdc++
+endif
+
+LDFLAGS += -shared
+
+# Verbosity.
+
+c_verbose_0 = @echo " C     " $(?F);
+c_verbose = $(c_verbose_$(V))
+
+cpp_verbose_0 = @echo " CPP   " $(?F);
+cpp_verbose = $(cpp_verbose_$(V))
+
+link_verbose_0 = @echo " LD    " $(@F);
+link_verbose = $(link_verbose_$(V))
+
+SOURCES := $(shell find $(C_SRC_DIR) -type f \( -name "*.c" -o -name "*.C" -o -name "*.cc" -o -name "*.cpp" \))
+OBJECTS = $(addsuffix .o, $(basename $(SOURCES)))
+
+COMPILE_C = $(c_verbose) $(CC) $(CFLAGS) $(CPPFLAGS) -c
+COMPILE_CPP = $(cpp_verbose) $(CXX) $(CXXFLAGS) $(CPPFLAGS) -c
+
+$(C_SRC_OUTPUT): $(OBJECTS)
+	@mkdir -p $(BASEDIR)/priv/
+	$(link_verbose) $(CC) $(OBJECTS) $(LDFLAGS) $(LDLIBS) -o $(C_SRC_OUTPUT)
+
+%.o: %.c
+	$(COMPILE_C) $(OUTPUT_OPTION) $<
+
+%.o: %.cc
+	$(COMPILE_CPP) $(OUTPUT_OPTION) $<
+
+%.o: %.C
+	$(COMPILE_CPP) $(OUTPUT_OPTION) $<
+
+%.o: %.cpp
+	$(COMPILE_CPP) $(OUTPUT_OPTION) $<
+
+clean:
+	@rm -f $(C_SRC_OUTPUT) $(OBJECTS)

c_src/atoms.h

@@ -0,0 +1,19 @@
+/* Copyright (c) 2017, Benoit Chesneau <bchesneau@gmail.com>.
+ *
+ * This file is part of instrument released under the MIT license.
+ * See the NOTICE for more information.
+ */
+
+#ifndef ATOMS_H
+#define ATOMS_H
+
+namespace prometheus {
+    extern ERL_NIF_TERM ATOM_OK;
+    extern ERL_NIF_TERM ATOM_ERROR;
+    extern ERL_NIF_TERM ATOM_EINVAL;
+    extern ERL_NIF_TERM ATOM_BADARG;
+
+} // namespace prometheus
+
+
+#endif // ATOMS_H

c_src/prometheus_nif.cc

@@ -0,0 +1,195 @@
+/* Copyright (c) 2017, Benoit Chesneau <bchesneau@gmail.com>.
+ *
+ * This file is part of prometheus released under the MIT license.
+ * See the NOTICE for more information.
+ */
+
+#include <syslog.h>
+
+#include <new>
+#include <stdexcept>
+
+#include "prometheus_nif.h"
+
+#include "erl_nif.h"
+
+#ifndef ATOMS_H
+#include "atoms.h"
+#endif
+
+#include "value.h"
+
+
+static ErlNifFunc nif_funcs[] =
+{
+    {"new_value", 0, prometheus::NewValue},
+    {"inc_value", 1, prometheus::IncValue},
+    {"inc_value", 2, prometheus::IncValue},
+    {"dec_value", 1, prometheus::DecValue},
+    {"dec_value", 2, prometheus::DecValue},
+    {"set_value", 2, prometheus::SetValue},
+    {"get_value", 1, prometheus::GetValue}
+};
+
+namespace prometheus {
+
+    ERL_NIF_TERM ATOM_OK;
+    ERL_NIF_TERM ATOM_ERROR;
+    ERL_NIF_TERM ATOM_EINVAL;
+    ERL_NIF_TERM ATOM_BADARG;
+
+
+    ErlNifResourceType *m_Value_RESOURCE;
+
+    void
+    value_resource_cleanup(ErlNifEnv *env, void *res)
+    {
+
+    }
+
+    void
+    CreateValueType(ErlNifEnv *env)
+    {
+        ErlNifResourceFlags flags = (ErlNifResourceFlags)(ERL_NIF_RT_CREATE | ERL_NIF_RT_TAKEOVER);
+        m_Value_RESOURCE = enif_open_resource_type(env, NULL, "prometheus_Value", value_resource_cleanup, flags, NULL);
+        return;
+    }
+
+    ERL_NIF_TERM
+    NewValue(
+        ErlNifEnv* env,
+        int argc,
+        const ERL_NIF_TERM argv[])
+    {
+        prometheus::Value * value;
+        void *alloc_ptr;
+        alloc_ptr = enif_alloc_resource(m_Value_RESOURCE, sizeof(prometheus::Value));
+        value = new(alloc_ptr) prometheus::Value();
+        ERL_NIF_TERM result = enif_make_resource(env, value);
+        enif_release_resource(value);
+        return enif_make_tuple2(env, ATOM_OK, result);
+    }
+
+    ERL_NIF_TERM
+    IncValue(
+        ErlNifEnv* env,
+        int argc,
+        const ERL_NIF_TERM argv[])
+    {
+        prometheus::Value* value_ptr;
+
+        if(!enif_get_resource(env, argv[0], m_Value_RESOURCE, (void **) &value_ptr))
+            return enif_make_badarg(env);
+
+        if(argc > 1)
+        {
+            double v;
+            if (!enif_get_double(env, argv[1], &v))
+                return enif_make_badarg(env);    
+            value_ptr->Increment(v);
+        }
+        else
+        {
+            value_ptr->Increment();
+        }
+
+        return ATOM_OK;
+    }
+
+    ERL_NIF_TERM
+    DecValue(
+        ErlNifEnv* env,
+        int argc,
+        const ERL_NIF_TERM argv[])
+    {
+        prometheus::Value* value_ptr;
+
+        if(!enif_get_resource(env, argv[0], m_Value_RESOURCE, (void **) &value_ptr))
+            return enif_make_badarg(env);
+
+        if(argc > 1)
+        {
+            double v;
+            if (!enif_get_double(env, argv[1], &v))
+                return enif_make_badarg(env);    
+            value_ptr->Decrement(v);
+        }
+        else
+        {
+            value_ptr->Decrement();
+        }
+
+        return ATOM_OK;
+    }
+
+    ERL_NIF_TERM
+    SetValue(
+        ErlNifEnv* env,
+        int argc,
+        const ERL_NIF_TERM argv[])
+    {
+        prometheus::Value* value_ptr;
+
+        if(!enif_get_resource(env, argv[0], m_Value_RESOURCE, (void **) &value_ptr))
+            return enif_make_badarg(env);
+
+        double v;
+        if (!enif_get_double(env, argv[1], &v))
+            return enif_make_badarg(env);    
+        value_ptr->Set(v);
+
+        return ATOM_OK;
+    }
+
+    ERL_NIF_TERM
+    GetValue(
+        ErlNifEnv* env,
+        int argc,
+        const ERL_NIF_TERM argv[])
+    {
+        prometheus::Value* value_ptr;
+
+        if(!enif_get_resource(env, argv[0], m_Value_RESOURCE, (void **) &value_ptr))
+            return enif_make_badarg(env);
+
+        double v;
+        v = value_ptr->GetValue();
+        return enif_make_double(env, v);
+    }
+
+} // namespace prometheus
+
+
+/*nif initialization  */
+
+static void on_unload(ErlNifEnv *env, void *priv_data)
+{
+}
+
+
+static int on_load(ErlNifEnv* env, void** priv_data, ERL_NIF_TERM load_info)
+{
+    try
+    {
+        prometheus::CreateValueType(env);
+
+#define ATOM(Id, Value) { Id = enif_make_atom(env, Value); }
+        // initialize the atoms
+        ATOM(prometheus::ATOM_OK, "ok");
+        ATOM(prometheus::ATOM_ERROR, "error");
+        ATOM(prometheus::ATOM_EINVAL, "einval");
+        ATOM(prometheus::ATOM_BADARG, "badarg");
+#undef ATOM
+
+        return 0;
+
+    }
+    catch(...)
+    {
+    return -1;
+    }
+}
+
+extern "C" {
+    ERL_NIF_INIT(prometheus_value, nif_funcs, &on_load, NULL, NULL, &on_unload);
+}

c_src/prometheus_nif.h

@@ -0,0 +1,31 @@
+/* Copyright (c) 2017, Benoit Chesneau <bchesneau@gmail.com>.
+ *
+ * This file is part of instrument released under the MIT license.
+ * See the NOTICE for more information.
+ */
+
+
+#ifndef INCL_instrument_H
+#define INCL_instrument_H
+
+extern "C" {
+#include "erl_nif.h"
+
+ERL_NIF_TERM instrument_new_value(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
+ERL_NIF_TERM instrument_inc_value(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
+ERL_NIF_TERM instrument_dec_value(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
+ERL_NIF_TERM instrument_set_value(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
+ERL_NIF_TERM instrument_get_value(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
+}
+
+namespace prometheus {
+
+ERL_NIF_TERM NewValue(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
+ERL_NIF_TERM IncValue(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
+ERL_NIF_TERM DecValue(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
+ERL_NIF_TERM SetValue(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
+ERL_NIF_TERM GetValue(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
+
+} // namespace instrument
+
+#endif

c_src/value.cc

@@ -0,0 +1,42 @@
+/* Copyright (c) 2017, Benoit Chesneau <bchesneau@gmail.com>.
+ *
+ * This file is part of instrument released under the MIT license.
+ * See the NOTICE for more information.
+ */
+
+#include "value.h"
+
+namespace prometheus {
+
+Value::Value() : value_{0} {}
+
+Value::Value(double value) : value_{value} {}
+
+void Value::Increment() { Increment(1.0); }
+void Value::Increment(double value) {
+  if (value < 0.0) {
+    return;
+  }
+  Change(value);
+}
+
+void Value::Decrement() { Decrement(1.0); }
+
+void Value::Decrement(double value) {
+  if (value < 0.0) {
+    return;
+  }
+  Change(-1.0 * value);
+}
+
+void Value::Set(double value) { value_.store(value); }
+
+void Value::Change(double value) {
+  auto current = value_.load();
+  while (!value_.compare_exchange_weak(current, current + value))
+    ;
+}
+
+double Value::GetValue() const { return value_; }
+
+}