From 980e409768d4fbf94bcd87b572bb357253a69921 Mon Sep 17 00:00:00 2001
From: Alexander Udalov <Alexander.Udalov@jetbrains.com>
Date: Thu, 20 Jun 2013 19:50:17 +0400
Subject: [PATCH] Optimize integer progression iterators

With the help of ProgressionUtil hasNext and next* consist now of only several
bytecode instructions
---
 runtime/src/jet/ByteProgressionIterator.java  | 18 +++++++++++++----
 runtime/src/jet/CharProgressionIterator.java  | 18 +++++++++++++----
 runtime/src/jet/IntProgressionIterator.java   | 20 ++++++++++++-------
 runtime/src/jet/LongProgressionIterator.java  | 20 ++++++++++++-------
 runtime/src/jet/ShortProgressionIterator.java | 18 +++++++++++++----
 5 files changed, 68 insertions(+), 26 deletions(-)

diff --git a/runtime/src/jet/ByteProgressionIterator.java b/runtime/src/jet/ByteProgressionIterator.java
index 85243e18f2f..fc5fc8417bc 100644
--- a/runtime/src/jet/ByteProgressionIterator.java
+++ b/runtime/src/jet/ByteProgressionIterator.java
@@ -16,26 +16,36 @@
 
 package jet;
 
+import jet.runtime.ProgressionUtil;
+
 class ByteProgressionIterator extends ByteIterator {
     private int next;
-    private final byte end;
     private final int increment;
+    private final byte finalElement;
+    private boolean hasNext;
 
     public ByteProgressionIterator(byte start, byte end, int increment) {
         this.next = start;
-        this.end = end;
         this.increment = increment;
+
+        this.finalElement = (byte) ProgressionUtil.getProgressionFinalElement(start, end, increment);
+        this.hasNext = increment < 0 ? start > end : start < end;
     }
 
     @Override
     public boolean hasNext() {
-        return increment > 0 ? next <= end : next >= end;
+        return hasNext;
     }
 
     @Override
     public byte nextByte() {
         int value = next;
-        next += increment;
+        if (value == finalElement) {
+            hasNext = false;
+        }
+        else {
+            next += increment;
+        }
         return (byte) value;
     }
 }
diff --git a/runtime/src/jet/CharProgressionIterator.java b/runtime/src/jet/CharProgressionIterator.java
index dc608162f9f..cb09aeb5347 100644
--- a/runtime/src/jet/CharProgressionIterator.java
+++ b/runtime/src/jet/CharProgressionIterator.java
@@ -16,26 +16,36 @@
 
 package jet;
 
+import jet.runtime.ProgressionUtil;
+
 class CharProgressionIterator extends CharIterator {
     private int next;
-    private final char end;
     private final int increment;
+    private final char finalElement;
+    private boolean hasNext;
 
     public CharProgressionIterator(char start, char end, int increment) {
         this.next = start;
-        this.end = end;
         this.increment = increment;
+
+        this.finalElement = (char) ProgressionUtil.getProgressionFinalElement(start, end, increment);
+        this.hasNext = increment < 0 ? start > end : start < end;
     }
 
     @Override
     public boolean hasNext() {
-        return increment > 0 ? next <= end : next >= end;
+        return hasNext;
     }
 
     @Override
     public char nextChar() {
         int value = next;
-        next += increment;
+        if (value == finalElement) {
+            hasNext = false;
+        }
+        else {
+            next += increment;
+        }
         return (char) value;
     }
 }
diff --git a/runtime/src/jet/IntProgressionIterator.java b/runtime/src/jet/IntProgressionIterator.java
index 3d7dda17af8..0b6f9bb5175 100644
--- a/runtime/src/jet/IntProgressionIterator.java
+++ b/runtime/src/jet/IntProgressionIterator.java
@@ -16,29 +16,35 @@
 
 package jet;
 
+import jet.runtime.ProgressionUtil;
+
 class IntProgressionIterator extends IntIterator {
     private int next;
-    private final int end;
     private final int increment;
-    private boolean overflowHappened = false;
+    private final int finalElement;
+    private boolean hasNext;
 
     public IntProgressionIterator(int start, int end, int increment) {
         this.next = start;
-        this.end = end;
         this.increment = increment;
+
+        this.finalElement = ProgressionUtil.getProgressionFinalElement(start, end, increment);
+        this.hasNext = increment < 0 ? start > end : start < end;
     }
 
     @Override
     public boolean hasNext() {
-        return !overflowHappened && (increment > 0 ? next <= end : next >= end);
+        return hasNext;
     }
 
     @Override
     public int nextInt() {
         int value = next;
-        next += increment;
-        if ((increment > 0) != (next > value)) {
-            overflowHappened = true;
+        if (value == finalElement) {
+            hasNext = false;
+        }
+        else {
+            next += increment;
         }
         return value;
     }
diff --git a/runtime/src/jet/LongProgressionIterator.java b/runtime/src/jet/LongProgressionIterator.java
index f6c613cf3fa..70493e39972 100644
--- a/runtime/src/jet/LongProgressionIterator.java
+++ b/runtime/src/jet/LongProgressionIterator.java
@@ -16,29 +16,35 @@
 
 package jet;
 
+import jet.runtime.ProgressionUtil;
+
 class LongProgressionIterator extends LongIterator {
     private long next;
-    private final long end;
     private final long increment;
-    private boolean overflowHappened = false;
+    private final long finalElement;
+    private boolean hasNext;
 
     public LongProgressionIterator(long start, long end, long increment) {
         this.next = start;
-        this.end = end;
         this.increment = increment;
+
+        this.finalElement = ProgressionUtil.getProgressionFinalElement(start, end, increment);
+        this.hasNext = increment < 0 ? start > end : start < end;
     }
 
     @Override
     public boolean hasNext() {
-        return !overflowHappened && (increment > 0 ? next <= end : next >= end);
+        return hasNext;
     }
 
     @Override
     public long nextLong() {
         long value = next;
-        next += increment;
-        if ((increment > 0) != (next > value)) {
-            overflowHappened = true;
+        if (value == finalElement) {
+            hasNext = false;
+        }
+        else {
+            next += increment;
         }
         return value;
     }
diff --git a/runtime/src/jet/ShortProgressionIterator.java b/runtime/src/jet/ShortProgressionIterator.java
index cd3b77200f9..d3da9e80326 100644
--- a/runtime/src/jet/ShortProgressionIterator.java
+++ b/runtime/src/jet/ShortProgressionIterator.java
@@ -16,26 +16,36 @@
 
 package jet;
 
+import jet.runtime.ProgressionUtil;
+
 class ShortProgressionIterator extends ShortIterator {
     private int next;
-    private final short end;
     private final int increment;
+    private final short finalElement;
+    private boolean hasNext;
 
     public ShortProgressionIterator(short start, short end, int increment) {
         this.next = start;
-        this.end = end;
         this.increment = increment;
+
+        this.finalElement = (short) ProgressionUtil.getProgressionFinalElement(start, end, increment);
+        this.hasNext = increment < 0 ? start > end : start < end;
     }
 
     @Override
     public boolean hasNext() {
-        return increment > 0 ? next <= end : next >= end;
+        return hasNext;
     }
 
     @Override
     public short nextShort() {
         int value = next;
-        next += increment;
+        if (value == finalElement) {
+            hasNext = false;
+        }
+        else {
+            next += increment;
+        }
         return (short) value;
     }
 }