[GitHub] [ignite] sk0x50 commented on a change in pull request #9177: IGNITE-14893 Fix IndexOutOfBoundsEcxeption in GridCacheWriteBehindStore flushers lookup by key

[GitBox <gi...@apache.org>]

sk0x50 commented on a change in pull request #9177:
URL: https://github.com/apache/ignite/pull/9177#discussion_r661363591



##########
File path: modules/core/src/main/java/org/apache/ignite/internal/util/IgniteUtils.java
##########
@@ -12106,4 +12106,33 @@ public static long uncompressedSize(File zip) throws IOException {
             return size;
         }
     }
+
+    /**
+     * Map object hash to some index between 0 and specified size via modulo operation.
+     *
+     * @param hash Object hash.
+     * @param size Size greater than 0.
+     * @return Calculated index in range [0..size).
+     */
+    public static int hashToIndex(int hash, int size) {
+        return safeAbs(hash % size);
+    }
+
+    /**
+     * Map object hash to some index between 0 and specified size using
+     * approach similar to {@link HashMap#hash(Object)}. In case
+     * <code>size</code> is not a power of 2 we fallback to modulo operation.
+     *
+     * @param hash Object hash.
+     * @param size Size greater than 0.
+     * @return Calculated index in range [0..size).
+     */
+    public static int hashToIndexOpt(int hash, int size, boolean isSizePow2) {
+        int h = (hash ^ (hash >>> 16));
+
+        return isSizePow2

Review comment:
       Well, this implementation relies on the user input and does not explicitly check the fact that the size variable is a power of two.
   It seems to me, it is easy to write a code as follows: hashToIndex(hash, 9, true) that leads to that only two results can be returned in this case - 0 and 8.

##########
File path: modules/core/src/main/java/org/apache/ignite/internal/util/IgniteUtils.java
##########
@@ -12106,4 +12106,33 @@ public static long uncompressedSize(File zip) throws IOException {
             return size;
         }
     }
+
+    /**
+     * Map object hash to some index between 0 and specified size via modulo operation.
+     *
+     * @param hash Object hash.
+     * @param size Size greater than 0.
+     * @return Calculated index in range [0..size).
+     */
+    public static int hashToIndex(int hash, int size) {
+        return safeAbs(hash % size);
+    }
+
+    /**
+     * Map object hash to some index between 0 and specified size using
+     * approach similar to {@link HashMap#hash(Object)}. In case
+     * <code>size</code> is not a power of 2 we fallback to modulo operation.
+     *
+     * @param hash Object hash.
+     * @param size Size greater than 0.
+     * @return Calculated index in range [0..size).
+     */
+    public static int hashToIndexOpt(int hash, int size, boolean isSizePow2) {

Review comment:
       Well, I don't think that you need to provide a unique name here, overloading is enough.

##########
File path: modules/core/src/main/java/org/apache/ignite/internal/util/IgniteUtils.java
##########
@@ -12106,4 +12106,33 @@ public static long uncompressedSize(File zip) throws IOException {
             return size;
         }
     }
+
+    /**
+     * Map object hash to some index between 0 and specified size via modulo operation.
+     *
+     * @param hash Object hash.
+     * @param size Size greater than 0.
+     * @return Calculated index in range [0..size).
+     */
+    public static int hashToIndex(int hash, int size) {
+        return safeAbs(hash % size);
+    }
+
+    /**
+     * Map object hash to some index between 0 and specified size using
+     * approach similar to {@link HashMap#hash(Object)}. In case
+     * <code>size</code> is not a power of 2 we fallback to modulo operation.
+     *
+     * @param hash Object hash.
+     * @param size Size greater than 0.
+     * @return Calculated index in range [0..size).

Review comment:
       Please add to Javadoc a new parameter which is `isSizePow2`.




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