Version 4

This change makes massive, incompatible updates to the project resulting in a
bump to version 4.  The code has been reworked to be more modular and simpler.
It takes lessons from the current building of Cloud Native Buildpacks to
become more idiomatic go.  Finally, the input flags are now POSIX-style rather
than Go style.

.gitignore

@@ -1,27 +1,17 @@
-# Compiled Object files, Static and Dynamic libs (Shared Objects)
-*.o
-*.a
-*.so
+# Copyright 2015-2018 the original author or authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
-# Folders
-_obj
-_test
-.idea
-
-# Architecture specific extensions/prefixes
-*.[568vq]
-[568vq].out
-
-*.cgo1.go
-*.cgo2.c
-_cgo_defun.c
-_cgo_gotypes.go
-_cgo_export.*
-
-_testmain.go
-
-*.exe
-*.test
-*.prof
-
-java-buildpack-memory-calculator*
+.idea/
+bin/
+*.iml

calculator/calculator.go

@@ -0,0 +1,113 @@
+/*
+ * Copyright 2015-2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package calculator
+
+import (
+	"fmt"
+
+	"github.com/cloudfoundry/java-buildpack-memory-calculator/flags"
+	"github.com/cloudfoundry/java-buildpack-memory-calculator/memory"
+)
+
+type Calculator struct {
+	HeadRoom         *flags.HeadRoom
+	JvmOptions       *flags.JVMOptions
+	LoadedClassCount *flags.LoadedClassCount
+	ThreadCount      *flags.ThreadCount
+	TotalMemory      *flags.TotalMemory
+}
+
+func (c Calculator) Calculate() ([]fmt.Stringer, error) {
+	var options []fmt.Stringer
+
+	j := c.JvmOptions
+	if j == nil {
+		j = &flags.JVMOptions{}
+	}
+
+	headRoom := c.headRoom()
+
+	directMemory := j.MaxDirectMemory
+	if directMemory == nil {
+		d := memory.DefaultMaxDirectMemory
+		directMemory = &d
+		options = append(options, *directMemory)
+	}
+
+	metaspace := j.MaxMetaspace
+	if metaspace == nil {
+		m := c.metaspace()
+		metaspace = &m
+		options = append(options, *metaspace)
+	}
+
+	reservedCodeCache := j.ReservedCodeCache
+	if reservedCodeCache == nil {
+		r := memory.DefaultReservedCodeCache
+		reservedCodeCache = &r
+		options = append(options, *reservedCodeCache)
+	}
+
+	stack := j.Stack
+	if stack == nil {
+		s := memory.DefaultStack
+		stack = &s
+		options = append(options, *stack)
+	}
+
+	overhead := c.overhead(headRoom, directMemory, metaspace, reservedCodeCache, stack)
+	available := memory.Size(*c.TotalMemory)
+
+	if overhead > available {
+		return nil, fmt.Errorf("allocated memory is greater than %s available for allocation: %s, %s, %s, %s x %d threads",
+			available, directMemory, metaspace, reservedCodeCache, stack, *c.ThreadCount)
+	}
+
+	heap := j.MaxHeap
+	if heap == nil {
+		h := c.heap(overhead)
+		heap = &h
+		options = append(options, *heap)
+	}
+
+	if overhead+memory.Size(*heap) > available {
+		return nil, fmt.Errorf("allocated memory is greater than %s available for allocation: %s, %s, %s, %s, %s x %d threads",
+			available, directMemory, heap, metaspace, reservedCodeCache, stack, *c.ThreadCount)
+	}
+
+	return options, nil
+}
+
+func (c Calculator) headRoom() memory.Size {
+	return memory.Size(float64(*c.TotalMemory) * (float64(*c.HeadRoom) / 100))
+}
+
+func (c Calculator) heap(overhead memory.Size) memory.MaxHeap {
+	return memory.MaxHeap(memory.Size(*c.TotalMemory) - overhead)
+}
+
+func (c Calculator) metaspace() memory.MaxMetaspace {
+	return memory.MaxMetaspace((*c.LoadedClassCount * 5800) + 14000000)
+}
+
+func (c Calculator) overhead(headRoom memory.Size, directMemory *memory.MaxDirectMemory, metaspace *memory.MaxMetaspace, reservedCodeCache *memory.ReservedCodeCache, stack *memory.Stack) memory.Size {
+	return headRoom +
+		memory.Size(*directMemory) +
+		memory.Size(*metaspace) +
+		memory.Size(*reservedCodeCache) +
+		memory.Size(int64(*stack)*int64(*c.ThreadCount))
+}