1 files changed, 111 insertions, 0 deletions
diff --git a/js/src/jslog2.cpp b/js/src/jslog2.cpp
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+++ b/js/src/jslog2.cpp
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+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (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.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is Mozilla Communicator client code, released
+ * March 31, 1998.
+ *
+ * The Initial Developer of the Original Code is
+ * Netscape Communications Corporation.
+ * Portions created by the Initial Developer are Copyright (C) 1998
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either of the GNU General Public License Version 2 or later (the "GPL"),
+ * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+#include "jsstdint.h"
+#include "jsbit.h"
+#include "jsutil.h"
+
+/*
+ * Check that we can use js_bitscan_clz32 to implement JS_FLOOR_LOG2 and
+ * JS_FLOOR_LOG2W and js_bitscan_clz64 to implement JS_FLOOR_LOG2W on 64-bit
+ * systems.
+ */
+#ifdef JS_HAS_BUILTIN_BITSCAN32
+JS_STATIC_ASSERT(sizeof(unsigned int) == sizeof(JSUint32));
+JS_STATIC_ASSERT_IF(JS_BYTES_PER_WORD == 4,
+                    sizeof(unsigned int) == sizeof(JSUword));
+#endif
+#ifdef JS_HAS_BUILTIN_BITSCAN64
+JS_STATIC_ASSERT_IF(JS_BYTES_PER_WORD == 8,
+                    sizeof(unsigned long long) == sizeof(JSUword));
+#endif
+
+/*
+ * Compute the log of the least power of 2 greater than or equal to n
+ */
+JS_PUBLIC_API(JSIntn)
+JS_CeilingLog2(JSUint32 n)
+{
+    JSIntn log2;
+
+    JS_CEILING_LOG2(log2, n);
+    return log2;
+}
+
+/*
+ * Compute the log of the greatest power of 2 less than or equal to n.
+ * This really just finds the highest set bit in the word.
+ */
+JS_PUBLIC_API(JSIntn)
+JS_FloorLog2(JSUint32 n)
+{
+    JSIntn log2;
+
+    JS_FLOOR_LOG2(log2, n);
+    return log2;
+}
+
+/*
+ * js_FloorLog2wImpl has to be defined only for 64-bit non-GCC case.
+ */
+#if !defined(JS_HAS_BUILTIN_BITSCAN64) && JS_BYTES_PER_WORD == 8
+
+size_t
+js_FloorLog2wImpl(size_t n)
+{
+    size_t log2, m;
+
+    JS_ASSERT(n != 0);
+
+    log2 = 0;
+    m = n >> 32;
+    if (m != 0) { n = m; log2 = 32; }
+    m = n >> 16;
+    if (m != 0) { n = m; log2 |= 16; }
+    m = n >> 8;
+    if (m != 0) { n = m; log2 |= 8; }
+    m = n >> 4;
+    if (m != 0) { n = m; log2 |= 4; }
+    m = n >> 2;
+    if (m != 0) { n = m; log2 |= 2; }
+    log2 |= (n >> 1);
+
+    return log2;
+}
+
+#endif