Revert "SERVER-36108 speed up BSONArrayBuilder by counting in decimal"

This reverts commit ce9968b484b95fe3f08ffe1d15791e8fadc9e854.

7 files changed, 36 insertions, 344 deletions

diff --git a/src/mongo/bson/SConscript b/src/mongo/bson/SConscript
index f1d9ab122ea..fbe9ef1dae0 100644
--- a/src/mongo/bson/SConscript
+++ b/src/mongo/bson/SConscript
@@ -65,16 +65,6 @@ env.CppUnitTest(
     ],
 )
 
-env.Benchmark(
-    target='bsonobjbuilder_bm',
-    source=[
-        'bsonobjbuilder_bm.cpp',
-    ],
-    LIBDEPS=[
-        '$BUILD_DIR/mongo/base',
-    ],
-)
-
 env.CppUnitTest(
     target='bsonelement_test',
     source=[
diff --git a/src/mongo/bson/bsonobjbuilder.h b/src/mongo/bson/bsonobjbuilder.h
index ef92065d9a0..6162495c1cd 100644
--- a/src/mongo/bson/bsonobjbuilder.h
+++ b/src/mongo/bson/bsonobjbuilder.h
@@ -48,7 +48,7 @@
 #include "mongo/bson/util/builder.h"
 #include "mongo/platform/decimal128.h"
 #include "mongo/stdx/type_traits.h"
-#include "mongo/util/decimal_counter.h"
+#include "mongo/util/itoa.h"
 
 namespace mongo {
 
@@ -810,20 +810,20 @@ private:
 
 class BSONArrayBuilder {
 public:
-    BSONArrayBuilder() {}
-    BSONArrayBuilder(BufBuilder& _b) : _b(_b) {}
-    BSONArrayBuilder(int initialSize) : _b(initialSize) {}
+    BSONArrayBuilder() : _i(0), _b() {}
+    BSONArrayBuilder(BufBuilder& _b) : _i(0), _b(_b) {}
+    BSONArrayBuilder(int initialSize) : _i(0), _b(initialSize) {}
 
     template <typename T>
     BSONArrayBuilder& append(const T& x) {
-        _b.append(_fieldCount, x);
-        ++_fieldCount;
+        ItoA itoa(_i++);
+        _b.append(itoa, x);
         return *this;
     }
 
     BSONArrayBuilder& append(const BSONElement& e) {
-        _b.appendAs(e, _fieldCount);
-        ++_fieldCount;
+        ItoA itoa(_i++);
+        _b.appendAs(e, itoa);
         return *this;
     }
 
@@ -833,19 +833,19 @@ public:
 
     template <typename T>
     BSONArrayBuilder& operator<<(const T& x) {
-        _b << _fieldCount << x;
-        ++_fieldCount;
+        ItoA itoa(_i++);
+        _b << itoa << x;
         return *this;
     }
 
     void appendNull() {
-        _b.appendNull(_fieldCount);
-        ++_fieldCount;
+        ItoA itoa(_i++);
+        _b.appendNull(itoa);
     }
 
     void appendUndefined() {
-        _b.appendUndefined(_fieldCount);
-        ++_fieldCount;
+        ItoA itoa(_i++);
+        _b.appendUndefined(itoa);
     }
 
     /**
@@ -875,57 +875,59 @@ public:
 
     // These two just use next position
     BufBuilder& subobjStart() {
-        return _b.subobjStart(_fieldCount++);
+        ItoA itoa(_i++);
+        return _b.subobjStart(itoa);
     }
     BufBuilder& subarrayStart() {
-        return _b.subarrayStart(_fieldCount++);
+        ItoA itoa(_i++);
+        return _b.subarrayStart(itoa);
     }
 
     BSONArrayBuilder& appendRegex(StringData regex, StringData options = "") {
-        _b.appendRegex(_fieldCount, regex, options);
-        ++_fieldCount;
+        ItoA itoa(_i++);
+        _b.appendRegex(itoa, regex, options);
         return *this;
     }
 
     BSONArrayBuilder& appendBinData(int len, BinDataType type, const void* data) {
-        _b.appendBinData(_fieldCount, len, type, data);
-        ++_fieldCount;
+        ItoA itoa(_i++);
+        _b.appendBinData(itoa, len, type, data);
         return *this;
     }
 
     BSONArrayBuilder& appendCode(StringData code) {
-        _b.appendCode(_fieldCount, code);
-        ++_fieldCount;
+        ItoA itoa(_i++);
+        _b.appendCode(itoa, code);
         return *this;
     }
 
     BSONArrayBuilder& appendCodeWScope(StringData code, const BSONObj& scope) {
-        _b.appendCodeWScope(_fieldCount, code, scope);
-        ++_fieldCount;
+        ItoA itoa(_i++);
+        _b.appendCodeWScope(itoa, code, scope);
         return *this;
     }
 
     BSONArrayBuilder& appendTimeT(time_t dt) {
-        _b.appendTimeT(_fieldCount, dt);
-        ++_fieldCount;
+        ItoA itoa(_i++);
+        _b.appendTimeT(itoa, dt);
         return *this;
     }
 
     BSONArrayBuilder& appendDate(Date_t dt) {
-        _b.appendDate(_fieldCount, dt);
-        ++_fieldCount;
+        ItoA itoa(_i++);
+        _b.appendDate(itoa, dt);
         return *this;
     }
 
     BSONArrayBuilder& appendBool(bool val) {
-        _b.appendBool(_fieldCount, val);
-        ++_fieldCount;
+        ItoA itoa(_i++);
+        _b.appendBool(itoa, val);
         return *this;
     }
 
     BSONArrayBuilder& appendTimestamp(unsigned long long ts) {
-        _b.appendTimestamp(_fieldCount, ts);
-        ++_fieldCount;
+        ItoA itoa(_i++);
+        _b.appendTimestamp(itoa, ts);
         return *this;
     }
 
@@ -937,7 +939,7 @@ public:
         return _b.len();
     }
     int arrSize() const {
-        return _fieldCount;
+        return _i;
     }
 
     BufBuilder& bb() {
@@ -945,7 +947,7 @@ public:
     }
 
 private:
-    DecimalCounter<uint32_t> _fieldCount;
+    std::uint32_t _i;
     BSONObjBuilder _b;
 };
 
diff --git a/src/mongo/bson/bsonobjbuilder_bm.cpp b/src/mongo/bson/bsonobjbuilder_bm.cpp
deleted file mode 100644
index 53410f72615..00000000000
--- a/src/mongo/bson/bsonobjbuilder_bm.cpp
+++ /dev/null
@@ -1,52 +0,0 @@
-/**
- *    Copyright (C) 2018 MongoDB Inc.
- *
- *    This program is free software: you can redistribute it and/or  modify
- *    it under the terms of the GNU Affero General Public License, version 3,
- *    as published by the Free Software Foundation.
- *
- *    This program 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 Affero General Public License for more details.
- *
- *    You should have received a copy of the GNU Affero General Public License
- *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
- *
- *    As a special exception, the copyright holders give permission to link the
- *    code of portions of this program with the OpenSSL library under certain
- *    conditions as described in each individual source file and distribute
- *    linked combinations including the program with the OpenSSL library. You
- *    must comply with the GNU Affero General Public License in all respects for
- *    all of the code used other than as permitted herein. If you modify file(s)
- *    with this exception, you may extend this exception to your version of the
- *    file(s), but you are not obligated to do so. If you do not wish to do so,
- *    delete this exception statement from your version. If you delete this
- *    exception statement from all source files in the program, then also delete
- *    it in the license file.
- */
-
-#include "mongo/platform/basic.h"
-
-#include <benchmark/benchmark.h>
-
-#include "mongo/bson/bsonobjbuilder.h"
-
-namespace mongo {
-
-void BM_arrayBuilder(benchmark::State& state) {
-    size_t totalBytes = 0;
-    for (auto _ : state) {
-        benchmark::ClobberMemory();
-        BSONArrayBuilder array;
-        for (auto j = 0; j < state.range(0); j++)
-            array.append(j);
-        totalBytes += array.len();
-        benchmark::DoNotOptimize(array.done());
-    }
-    state.SetBytesProcessed(totalBytes);
-}
-
-BENCHMARK(BM_arrayBuilder)->Ranges({{{1}, {100'000}}});
-
-}  // namespace mongo
diff --git a/src/mongo/util/SConscript b/src/mongo/util/SConscript
index 7935d4930ec..ffca101f781 100644
--- a/src/mongo/util/SConscript
+++ b/src/mongo/util/SConscript
@@ -608,13 +608,6 @@ env.Library(
 )
 
 env.CppUnitTest(
-    target='decimal_counter_test',
-    source=[
-        'decimal_counter_test.cpp',
-    ],
-)
-
-env.CppUnitTest(
     target='itoa_test',
     source=[
         'itoa_test.cpp',
@@ -692,15 +685,6 @@ env.CppUnitTest(
 )
 
 env.Benchmark(
-    target='decimal_counter_bm',
-    source=[
-        'decimal_counter_bm.cpp',
-    ],
-    LIBDEPS=[
-    ],
-)
-
-env.Benchmark(
     target='future_bm',
     source=[
         'future_bm.cpp',
diff --git a/src/mongo/util/decimal_counter.h b/src/mongo/util/decimal_counter.h
deleted file mode 100644
index 13b9f886127..00000000000
--- a/src/mongo/util/decimal_counter.h
+++ /dev/null
@@ -1,103 +0,0 @@
-/**
- *    Copyright (C) 2018 MongoDB, Inc.
- *
- *    This program is free software: you can redistribute it and/or  modify
- *    it under the terms of the GNU Affero General Public License, version 3,
- *    as published by the Free Software Foundation.
- *
- *    This program 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 Affero General Public License for more details.
- *
- *    You should have received a copy of the GNU Affero General Public License
- *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
- *
- *    As a special exception, the copyright holders give permission to link the
- *    code of portions of this program with the OpenSSL library under certain
- *    conditions as described in each individual source file and distribute
- *    linked combinations including the program with the OpenSSL library. You
- *    must comply with the GNU Affero General Public License in all respects for
- *    all of the code used other than as permitted herein. If you modify file(s)
- *    with this exception, you may extend this exception to your version of the
- *    file(s), but you are not obligated to do so. If you do not wish to do so,
- *    delete this exception statement from your version. If you delete this
- *    exception statement from all source files in the program, then also delete
- *    it in the license file.
- */
-
-#pragma once
-
-#include <cstdint>
-#include <limits>
-
-#include "mongo/base/string_data.h"
-
-namespace mongo {
-/**
- * Stores unsigned counter as well as its decimal ASCII representation, avoiding the need for
- * separate binary to decimal conversions. This speeds up code that needs string representations
- * for all counter values.
- */
-template <typename T>
-class DecimalCounter {
-public:
-    static_assert(std::is_unsigned<T>::value, "DecimalCounter requires an unsigned type");
-    constexpr operator StringData() const {
-        return {_digits, static_cast<size_t>(_lastDigitIndex + 1)};
-    }
-    constexpr operator uint32_t() const {
-        return _counter;
-    }
-
-    /**
-     *  Increments the counter and its decimal representation. The decimal representation wraps
-     *  independently of the binary counter.
-     */
-    constexpr DecimalCounter<T>& operator++() {
-        // Common case: just increment the last digit and we're done with the string part.
-        char* lastPtr = _digits + _lastDigitIndex;
-        if (MONGO_unlikely((*lastPtr)++ == '9')) {
-            // Let zeroPtr point at the first char in the string, such that it and all digits
-            // after need to change to zeroes.
-            char* zeroPtr = lastPtr;
-            while (zeroPtr > _digits && zeroPtr[-1] == '9')
-                --zeroPtr;
-
-            // If digits wasn't all nines, increment the first non-nine.
-            if (zeroPtr > _digits) {
-                zeroPtr[-1]++;
-            } else if (lastPtr < _digits + sizeof(_digits) - 2) {
-                // Rare case: new power of 10 increases string length, so start with a one.
-                *zeroPtr++ = '1';
-                _lastDigitIndex++;
-                lastPtr++;
-            }
-            // Zero out the rest.
-            do {
-                *zeroPtr++ = '0';
-            } while (zeroPtr <= lastPtr);
-        }
-        if (MONGO_unlikely(++_counter == 0))
-            *this = {};
-        return *this;
-    }
-
-    /**
-     *  Post-inrement version of operator++. Typically slower than pre-increment due to the need
-     *  to return the pre-image by value.
-     */
-    constexpr DecimalCounter<T> operator++(int) {
-        auto pre = *this;
-        operator++();
-        return pre;
-    }
-
-private:
-    // Add 1, because digit10 is 1 less than the maximum number of digits, and 1 for the final '\0'.
-    static constexpr size_t kBufSize = std::numeric_limits<T>::digits10 + 2;
-    char _digits[kBufSize] = {'0'};  // Remainder is zero-initialized.
-    uint8_t _lastDigitIndex = 0;     // Indicates the last digit in _digits.
-    T _counter = 0;
-};
-}
diff --git a/src/mongo/util/decimal_counter_bm.cpp b/src/mongo/util/decimal_counter_bm.cpp
deleted file mode 100644
index 4dad2e17940..00000000000
--- a/src/mongo/util/decimal_counter_bm.cpp
+++ /dev/null
@@ -1,76 +0,0 @@
-/**
- *    Copyright (C) 2018 MongoDB Inc.
- *
- *    This program is free software: you can redistribute it and/or  modify
- *    it under the terms of the GNU Affero General Public License, version 3,
- *    as published by the Free Software Foundation.
- *
- *    This program 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 Affero General Public License for more details.
- *
- *    You should have received a copy of the GNU Affero General Public License
- *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
- *
- *    As a special exception, the copyright holders give permission to link the
- *    code of portions of this program with the OpenSSL library under certain
- *    conditions as described in each individual source file and distribute
- *    linked combinations including the program with the OpenSSL library. You
- *    must comply with the GNU Affero General Public License in all respects for
- *    all of the code used other than as permitted herein. If you modify file(s)
- *    with this exception, you may extend this exception to your version of the
- *    file(s), but you are not obligated to do so. If you do not wish to do so,
- *    delete this exception statement from your version. If you delete this
- *    exception statement from all source files in the program, then also delete
- *    it in the license file.
- */
-
-#include "mongo/platform/basic.h"
-
-#include <benchmark/benchmark.h>
-
-#include "mongo/util/decimal_counter.h"
-#include "mongo/util/itoa.h"
-
-namespace mongo {
-
-void BM_decimalCounterPreInc(benchmark::State& state) {
-    DecimalCounter<uint32_t> count;
-    for (auto _ : state) {
-        benchmark::ClobberMemory();
-        benchmark::DoNotOptimize(StringData(++count));
-    }
-}
-
-void BM_decimalCounterPostInc(benchmark::State& state) {
-    DecimalCounter<uint32_t> count;
-    for (auto _ : state) {
-        benchmark::ClobberMemory();
-        benchmark::DoNotOptimize(StringData(count++));
-    }
-}
-
-void BM_ItoACounter(benchmark::State& state) {
-    uint32_t count = 0;
-    for (auto _ : state) {
-        benchmark::ClobberMemory();
-        benchmark::DoNotOptimize(StringData(ItoA(++count)));
-    }
-}
-
-void BM_to_stringCounter(benchmark::State& state) {
-    uint32_t count = 0;
-    std::string str;
-    for (auto _ : state) {
-        benchmark::ClobberMemory();
-        benchmark::DoNotOptimize(std::to_string(++count));
-    }
-}
-
-BENCHMARK(BM_decimalCounterPreInc);
-BENCHMARK(BM_decimalCounterPostInc);
-BENCHMARK(BM_ItoACounter);
-BENCHMARK(BM_to_stringCounter);
-
-}  // namespace mongo
diff --git a/src/mongo/util/decimal_counter_test.cpp b/src/mongo/util/decimal_counter_test.cpp
deleted file mode 100644
index cff11c768a5..00000000000
--- a/src/mongo/util/decimal_counter_test.cpp
+++ /dev/null
@@ -1,53 +0,0 @@
-/**
- * Copyright (C) 2018 MongoDB Inc.
- *
- * This program is free software: you can redistribute it and/or  modify
- * it under the terms of the GNU Affero General Public License, version 3,
- * as published by the Free Software Foundation.
- *
- * This program 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 Affero General Public License for more details.
- *
- * You should have received a copy of the GNU Affero General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- *
- * As a special exception, the copyright holders give permission to link the
- * code of portions of this program with the OpenSSL library under certain
- * conditions as described in each individual source file and distribute
- * linked combinations including the program with the OpenSSL library. You
- * must comply with the GNU Affero General Public License in all respects
- * for all of the code used other than as permitted herein. If you modify
- * file(s) with this exception, you may extend this exception to your
- * version of the file(s), but you are not obligated to do so. If you do not
- * wish to do so, delete this exception statement from your version. If you
- * delete this exception statement from all source files in the program,
- * then also delete it in the license file.
- */
-
-#include "mongo/platform/basic.h"
-
-#include <array>
-#include <cstdint>
-#include <limits>
-
-#include "mongo/base/string_data.h"
-#include "mongo/unittest/unittest.h"
-#include "mongo/util/decimal_counter.h"
-
-namespace {
-using namespace mongo;
-
-TEST(DecimalCounter, CountUntilWrapAround) {
-    DecimalCounter<uint16_t> counter;
-    uint16_t check = 0;
-    do {
-        StringData str = counter;
-        ASSERT_EQ(std::to_string(check), str.toString());
-        ASSERT_EQ(str.rawData()[str.size()], '\0');
-        ASSERT_EQ(uint16_t(++counter), ++check);
-    } while (check);
-    ASSERT_EQ(StringData(counter), "0"_sd);
-}
-}  // namespace