1 files changed, 147 insertions, 0 deletions
diff --git a/storage/tokudb/tokudb_math.h b/storage/tokudb/tokudb_math.h
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+++ b/storage/tokudb/tokudb_math.h
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+/* -*- mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
+// vim: ft=cpp:expandtab:ts=8:sw=4:softtabstop=4:
+#ident "$Id$"
+/*======
+This file is part of TokuDB
+
+
+Copyright (c) 2006, 2015, Percona and/or its affiliates. All rights reserved.
+
+    TokuDBis is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License, version 2,
+    as published by the Free Software Foundation.
+
+    TokuDB is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with TokuDB.  If not, see <http://www.gnu.org/licenses/>.
+
+======= */
+
+#ident "Copyright (c) 2006, 2015, Percona and/or its affiliates. All rights reserved."
+
+#if !defined(_TOKUDB_MATH_H)
+#define _TOKUDB_MATH_H
+
+namespace tokudb {
+
+// Add and subtract ints with overflow detection.
+// Overflow detection adapted from "Hackers Delight", Henry S. Warren
+
+// Return a bit mask for bits 0 .. length_bits-1
+TOKUDB_UNUSED(static uint64_t uint_mask(uint length_bits));
+static uint64_t uint_mask(uint length_bits) {
+    return length_bits == 64 ? ~0ULL : (1ULL<<length_bits)-1;
+}
+
+// Return the highest unsigned int with a given number of bits
+TOKUDB_UNUSED(static uint64_t uint_high_endpoint(uint length_bits));
+static uint64_t uint_high_endpoint(uint length_bits) {
+    return uint_mask(length_bits);
+}
+
+// Return the lowest unsigned int with a given number of bits
+TOKUDB_UNUSED(static uint64_t uint_low_endpoint(uint length_bits));
+static uint64_t uint_low_endpoint(TOKUDB_UNUSED(uint length_bits)) {
+    return 0;
+}
+
+// Add two unsigned integers with max maximum value.
+// If there is an overflow then set the sum to the max.
+// Return the sum and the overflow.
+TOKUDB_UNUSED(static uint64_t uint_add(
+    uint64_t x,
+    uint64_t y,
+    uint length_bits,
+    bool* over));
+static uint64_t uint_add(uint64_t x, uint64_t y, uint length_bits, bool *over) {
+    uint64_t mask = uint_mask(length_bits);
+    assert_always((x & ~mask) == 0);
+    assert_always((y & ~mask) == 0);
+    uint64_t s = (x + y) & mask;
+    *over = s < x;     // check for overflow
+    return s;
+}
+
+// Subtract two unsigned ints with max maximum value.
+// If there is an over then set the difference to 0.
+// Return the difference and the overflow.
+TOKUDB_UNUSED(static uint64_t uint_sub(
+    uint64_t x,
+    uint64_t y,
+    uint length_bits,
+    bool* over));
+static uint64_t uint_sub(uint64_t x, uint64_t y, uint length_bits, bool *over) {
+    uint64_t mask = uint_mask(length_bits);
+    assert_always((x & ~mask) == 0);
+    assert_always((y & ~mask) == 0);
+    uint64_t s = (x - y) & mask;
+    *over = s > x;    // check for overflow
+    return s;
+}
+
+// Return the highest int with a given number of bits
+TOKUDB_UNUSED(static int64_t int_high_endpoint(uint length_bits));
+static int64_t int_high_endpoint(uint length_bits) {
+    return (1ULL<<(length_bits-1))-1;
+}
+
+// Return the lowest int with a given number of bits
+TOKUDB_UNUSED(static int64_t int_low_endpoint(uint length_bits));
+static int64_t int_low_endpoint(uint length_bits) {
+    int64_t mask = uint_mask(length_bits);
+    return (1ULL<<(length_bits-1)) | ~mask;
+}
+
+// Sign extend to 64 bits an int with a given number of bits
+TOKUDB_UNUSED(static int64_t int_sign_extend(int64_t n, uint length_bits));
+static int64_t int_sign_extend(int64_t n, uint length_bits) {
+    if (n & (1ULL<<(length_bits-1)))
+        n |= ~uint_mask(length_bits);
+    return n;
+}
+
+// Add two signed ints with max maximum value.
+// If there is an overflow then set the sum to the max or the min of the int range,
+// depending on the sign bit.
+// Sign extend to 64 bits.
+// Return the sum and the overflow.
+TOKUDB_UNUSED(static int64_t int_add(
+    int64_t x,
+    int64_t y,
+    uint length_bits,
+    bool* over));
+static int64_t int_add(int64_t x, int64_t y, uint length_bits, bool *over) {
+    int64_t mask = uint_mask(length_bits);
+    int64_t n = (x + y) & mask;
+    *over = (((n ^ x) & (n ^ y)) >> (length_bits-1)) & 1;    // check for overflow
+    if (n & (1LL<<(length_bits-1)))
+        n |= ~mask;    // sign extend
+    return n;
+}
+
+// Subtract two signed ints.
+// If there is an overflow then set the sum to the max or the min of the int range,
+// depending on the sign bit.
+// Sign extend to 64 bits.
+// Return the sum and the overflow.
+TOKUDB_UNUSED(static int64_t int_sub(
+    int64_t x,
+    int64_t y,
+    uint length_bits,
+    bool* over));
+static int64_t int_sub(int64_t x, int64_t y, uint length_bits, bool *over) {
+    int64_t mask = uint_mask(length_bits);
+    int64_t n = (x - y) & mask;
+    *over = (((x ^ y) & (n ^ x)) >> (length_bits-1)) & 1;    // check for overflow
+    if (n & (1LL<<(length_bits-1)))
+        n |= ~mask;    // sign extend
+    return n;
+}
+
+} // namespace tokudb
+
+#endif