small_vector_test.cc

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/*
                          Aleph_w
 
  Data structures & Algorithms
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
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*/
 
#include <memory>
#include <stdexcept>
#include <string>
#include <type_traits>
#include <vector>
 
#include <gtest/gtest.h>
 
#include <tpl_small_vector.H>
 
using Aleph::SmallVector;
 
namespace
{
// Instrumented element type: counts live instances so tests can prove that
// placement-constructed elements are destroyed exactly once.
struct Probe
{
  static int live;
  int value = 0;
 
  Probe() { ++live; }
  explicit Probe(int v) : value(v) { ++live; }
  Probe(const Probe &p) : value(p.value) { ++live; }
  Probe(Probe &&p) noexcept : value(p.value) { ++live; }
  Probe &operator=(const Probe &) = default;
  Probe &operator=(Probe &&) noexcept = default;
  ~Probe() { --live; }
};
 
int Probe::live = 0;
 
struct Throwing_Copy
{
  static int live;
  static int copies;
  static int throw_after;
  int value = 0;
 
  explicit Throwing_Copy(int v) : value(v) { ++live; }
 
  Throwing_Copy(const Throwing_Copy &x) : value(x.value)
  {
    if (throw_after >= 0 and copies++ >= throw_after)
      throw std::runtime_error("copy failed");
    ++live;
  }
 
  Throwing_Copy(Throwing_Copy &&x) noexcept : value(x.value) { ++live; }
 
  Throwing_Copy &operator=(const Throwing_Copy &) = default;
  Throwing_Copy &operator=(Throwing_Copy &&) noexcept = default;
 
  ~Throwing_Copy() { --live; }
 
  static void reset(int limit = -1)
  {
    copies = 0;
    throw_after = limit;
  }
};
 
int Throwing_Copy::live = 0;
int Throwing_Copy::copies = 0;
int Throwing_Copy::throw_after = -1;
 
struct Throwing_Move
{
  int value = 0;
 
  Throwing_Move() = default;
  explicit Throwing_Move(int v) : value(v) {}
  Throwing_Move(const Throwing_Move &) = delete;
  Throwing_Move(Throwing_Move &&x) noexcept(false) : value(x.value) {}
  Throwing_Move &operator=(const Throwing_Move &) = delete;
  Throwing_Move &operator=(Throwing_Move &&) noexcept(false) = default;
};
 
static_assert(noexcept(std::declval<SmallVector<int, 2> &>().swap
                       (std::declval<SmallVector<int, 2> &>())));
static_assert(not noexcept(std::declval<SmallVector<Throwing_Move, 2> &>().swap
                           (std::declval<SmallVector<Throwing_Move, 2> &>())));
}  // namespace
 
TEST(SmallVector, StaysInlineUpToNThenSpills)
{
  SmallVector<int, 4> v;
  EXPECT_TRUE(v.is_small());
  EXPECT_EQ(v.capacity(), 4u);
  EXPECT_TRUE(v.is_empty());
 
  for (int i = 0; i < 4; ++i)
    v.append(i);
  EXPECT_TRUE(v.is_small());  // exactly N elements: still inline
  EXPECT_EQ(v.size(), 4u);
 
  v.append(4);  // spill
  EXPECT_FALSE(v.is_small());
  EXPECT_GE(v.capacity(), 5u);
  ASSERT_EQ(v.size(), 5u);
  for (int i = 0; i < 5; ++i)
    EXPECT_EQ(v[i], i);  // values preserved across the spill
}
 
TEST(SmallVector, InlineBufferIsInsideTheObject)
{
  SmallVector<int, 4> v;
  v.append(1);
  const char *obj = reinterpret_cast<const char *>(&v);
  const char *elem = reinterpret_cast<const char *>(v.data());
  EXPECT_GE(elem, obj);
  EXPECT_LT(elem, obj + sizeof(v));
 
  for (int i = 0; i < 10; ++i)
    v.append(i);
  const char *heap_elem = reinterpret_cast<const char *>(v.data());
  EXPECT_TRUE(heap_elem < obj or heap_elem >= obj + sizeof(v));
}
 
TEST(SmallVector, ElementLifetimesAreBalanced)
{
  ASSERT_EQ(Probe::live, 0);
  {
    SmallVector<Probe, 2> v;
    v.emplace_back(1);
    v.emplace_back(2);
    EXPECT_EQ(Probe::live, 2);
    v.emplace_back(3);  // spill: old elements destroyed, new ones created
    EXPECT_EQ(Probe::live, 3);
    v.pop_back();
    EXPECT_EQ(Probe::live, 2);
    v.clear();
    EXPECT_EQ(Probe::live, 0);
    v.emplace_back(9);
    EXPECT_EQ(Probe::live, 1);
  }
  EXPECT_EQ(Probe::live, 0);  // destructor cleaned everything
}
 
TEST(SmallVector, FailedConstructorsCleanPartialElements)
{
  ASSERT_EQ(Throwing_Copy::live, 0);
 
  {
    Throwing_Copy value(1);
    Throwing_Copy::reset(1);
    EXPECT_THROW((SmallVector<Throwing_Copy, 2>(3, value)),
                 std::runtime_error);
    EXPECT_EQ(Throwing_Copy::live, 1);
  }
  EXPECT_EQ(Throwing_Copy::live, 0);
 
  Throwing_Copy::reset(1);
  EXPECT_THROW((SmallVector<Throwing_Copy, 2>
                {Throwing_Copy(1), Throwing_Copy(2), Throwing_Copy(3)}),
               std::runtime_error);
  EXPECT_EQ(Throwing_Copy::live, 0);
 
  {
    std::vector<Throwing_Copy> src;
    src.emplace_back(1);
    src.emplace_back(2);
    src.emplace_back(3);
    ASSERT_EQ(Throwing_Copy::live, 3);
    Throwing_Copy::reset(1);
    EXPECT_THROW((SmallVector<Throwing_Copy, 2>(src.begin(), src.end())),
                 std::runtime_error);
    EXPECT_EQ(Throwing_Copy::live, 3);
  }
  EXPECT_EQ(Throwing_Copy::live, 0);
 
  {
    SmallVector<Throwing_Copy, 2> src;
    src.emplace_back(1);
    src.emplace_back(2);
    src.emplace_back(3);
    ASSERT_EQ(Throwing_Copy::live, 3);
    Throwing_Copy::reset(1);
    EXPECT_THROW((SmallVector<Throwing_Copy, 2>(src)), std::runtime_error);
    EXPECT_EQ(Throwing_Copy::live, 3);
  }
  EXPECT_EQ(Throwing_Copy::live, 0);
}
 
TEST(SmallVector, MoveOnlyElementsAreSupported)
{
  SmallVector<std::unique_ptr<int>, 2> v;
  v.append(std::make_unique<int>(1));
  v.append(std::make_unique<int>(2));
  v.append(std::make_unique<int>(3));  // spill with move-only type
  ASSERT_EQ(v.size(), 3u);
  EXPECT_EQ(*v[0], 1);
  EXPECT_EQ(*v[2], 3);
 
  std::unique_ptr<int> p = v.remove_last();
  EXPECT_EQ(*p, 3);
  EXPECT_EQ(v.size(), 2u);
 
  SmallVector<std::unique_ptr<int>, 2> moved = std::move(v);
  ASSERT_EQ(moved.size(), 2u);
  EXPECT_EQ(*moved[1], 2);
}
 
TEST(SmallVector, CopySemanticsInBothModes)
{
  SmallVector<std::string, 4> inline_v = {"a", "b"};
  SmallVector<std::string, 4> c1 = inline_v;
  EXPECT_EQ(c1, inline_v);
  c1[0] = "zzz";
  EXPECT_EQ(inline_v[0], "a");  // deep copy
 
  SmallVector<std::string, 2> heap_v = {"a", "b", "c", "d"};
  EXPECT_FALSE(heap_v.is_small());
  SmallVector<std::string, 2> c2 = heap_v;
  EXPECT_EQ(c2, heap_v);
 
  SmallVector<std::string, 2> small_src = {"s"};
  c2 = small_src;  // copy assignment: heap-mode target, inline-mode source
  ASSERT_EQ(c2.size(), 1u);
  EXPECT_EQ(c2[0], "s");
}
 
TEST(SmallVector, MoveSemanticsInBothModes)
{
  // Inline mode: elements are moved one by one; source is emptied.
  SmallVector<std::string, 4> a = {"x", "y"};
  SmallVector<std::string, 4> ma = std::move(a);
  ASSERT_EQ(ma.size(), 2u);
  EXPECT_EQ(ma[0], "x");
  EXPECT_TRUE(a.is_empty());
 
  // Heap mode: the buffer is stolen in O(1); source returns to inline.
  SmallVector<std::string, 2> b = {"1", "2", "3"};
  const std::string *heap_data = b.data();
  SmallVector<std::string, 2> mb = std::move(b);
  EXPECT_EQ(mb.data(), heap_data);  // pointer stolen, no element moves
  EXPECT_TRUE(b.is_empty());
  EXPECT_TRUE(b.is_small());
  b.append("reuse");  // source is reusable after move
  EXPECT_EQ(b[0], "reuse");
}
 
TEST(SmallVector, InsertAndEraseAtPosition)
{
  SmallVector<int, 4> v = {1, 2, 4};
  v.insert(2, 3);  // {1, 2, 3, 4}
  ASSERT_EQ(v.size(), 4u);
  for (int i = 0; i < 4; ++i)
    EXPECT_EQ(v[i], i + 1);
 
  v.insert(0, 0);  // {0, 1, 2, 3, 4} — forces spill
  EXPECT_FALSE(v.is_small());
  EXPECT_EQ(v[0], 0);
  EXPECT_EQ(v[4], 4);
 
  v.insert(v.size(), 5);  // append via insert at end
  EXPECT_EQ(v.get_last(), 5);
 
  v.erase(0);  // {1, 2, 3, 4, 5}
  EXPECT_EQ(v.get_first(), 1);
  v.erase(v.size() - 1);  // {1, 2, 3, 4}
  EXPECT_EQ(v.get_last(), 4);
  EXPECT_EQ(v.size(), 4u);
 
  EXPECT_THROW(v.insert(v.size() + 1, 9), std::out_of_range);
  EXPECT_THROW(v.erase(v.size()), std::out_of_range);
}
 
TEST(SmallVector, CheckedAndUncheckedAccess)
{
  SmallVector<int, 4> v = {10, 20};
  EXPECT_EQ(v[1], 20);
  EXPECT_EQ(v(0), 10);
  EXPECT_THROW((void) v[2], std::out_of_range);
 
  const SmallVector<int, 4> &cv = v;
  EXPECT_EQ(cv[0], 10);
  EXPECT_THROW((void) cv[5], std::out_of_range);
 
  SmallVector<int, 4> e;
  EXPECT_THROW((void) e.get_first(), std::underflow_error);
  EXPECT_THROW((void) e.get_last(), std::underflow_error);
  EXPECT_THROW((void) e.remove_last(), std::underflow_error);
  EXPECT_THROW(e.pop_back(), std::underflow_error);
}
 
TEST(SmallVector, IterationAndRangeFor)
{
  SmallVector<int, 3> v = {1, 2, 3, 4};  // heap mode
  int sum = 0;
  for (int x : v)
    sum += x;
  EXPECT_EQ(sum, 10);
 
  for (int &x : v)
    x *= 2;
  EXPECT_EQ(v[3], 8);
 
  EXPECT_EQ(static_cast<size_t>(v.end() - v.begin()), v.size());
}
 
TEST(SmallVector, AlephConventionsEmptyClearTraverse)
{
  SmallVector<int, 4> v = {1, 2, 3};
 
  int sum = 0;
  EXPECT_TRUE(v.traverse([&sum] (int &x) { sum += x; return true; }));
  EXPECT_EQ(sum, 6);
 
  int visited = 0;
  const SmallVector<int, 4> &cv = v;
  EXPECT_FALSE(cv.traverse([&visited] (const int &x)
  {
    ++visited;
    return x < 2;
  }));
  EXPECT_EQ(visited, 2);
 
  v.empty();  // Aleph convention: empty() clears
  EXPECT_TRUE(v.is_empty());
  EXPECT_EQ(v.size(), 0u);
}
 
TEST(SmallVector, ReserveGrowsAndKeepsElements)
{
  SmallVector<int, 2> v = {7, 8};
  EXPECT_TRUE(v.is_small());
  v.reserve(100);
  EXPECT_FALSE(v.is_small());
  EXPECT_GE(v.capacity(), 100u);
  EXPECT_EQ(v[0], 7);
  EXPECT_EQ(v[1], 8);
 
  const int *p = v.data();
  for (int i = 0; i < 90; ++i)
    v.append(i);
  EXPECT_EQ(v.data(), p);  // no reallocation within reserved capacity
}
 
TEST(SmallVector, ReserveDetectsCapacityOverflow)
{
  SmallVector<int, 2> v;
  EXPECT_THROW(v.reserve(static_cast<size_t>(-1)), std::overflow_error);
  EXPECT_TRUE(v.is_empty());
  EXPECT_TRUE(v.is_small());
}
 
TEST(SmallVector, RangeConstructorAndFillConstructor)
{
  const std::vector<int> src = {5, 6, 7, 8, 9};
  SmallVector<int, 2> v(src.begin(), src.end());
  ASSERT_EQ(v.size(), 5u);
  EXPECT_EQ(v[4], 9);
 
  SmallVector<std::string, 4> f(3, "ho");
  ASSERT_EQ(f.size(), 3u);
  EXPECT_EQ(f[2], "ho");
  EXPECT_TRUE(f.is_small());
}
 
TEST(SmallVector, EqualityAcrossDifferentInlineCapacities)
{
  SmallVector<int, 2> a = {1, 2, 3};
  SmallVector<int, 8> b = {1, 2, 3};
  EXPECT_TRUE(a == b);
  b.append(4);
  EXPECT_TRUE(a != b);
}
 
TEST(SmallVector, SwapInAllModeCombinations)
{
  // heap <-> heap: O(1) pointer swap.
  SmallVector<int, 2> h1 = {1, 2, 3};
  SmallVector<int, 2> h2 = {9, 8, 7, 6};
  const int *p1 = h1.data();
  const int *p2 = h2.data();
  h1.swap(h2);
  EXPECT_EQ(h1.data(), p2);
  EXPECT_EQ(h2.data(), p1);
  EXPECT_EQ(h1.size(), 4u);
  EXPECT_EQ(h2.size(), 3u);
 
  // inline <-> heap.
  SmallVector<int, 4> s1 = {1};
  SmallVector<int, 4> s2 = {9, 8, 7, 6, 5};
  s1.swap(s2);
  EXPECT_EQ(s1.size(), 5u);
  EXPECT_EQ(s1[0], 9);
  EXPECT_EQ(s2.size(), 1u);
  EXPECT_EQ(s2[0], 1);
}
 
TEST(SmallVector, AppendRangeTrivialTypeStaysInlineThenSpillsCorrectly)
{
  // char is trivially copyable: append_range should take the memcpy path.
  const char src[] = {'a', 'b', 'c', 'd', 'e', 'f'};
 
  SmallVector<char, 4> v;
  v.append_range(src, 3);
  EXPECT_TRUE(v.is_small());
  ASSERT_EQ(v.size(), 3u);
  for (size_t i = 0; i < 3; ++i)
    EXPECT_EQ(v[i], src[i]);
 
  v.append_range(src + 3, 1);  // exactly fills the inline capacity (4)
  EXPECT_TRUE(v.is_small());
  ASSERT_EQ(v.size(), 4u);
 
  v.append_range(src + 4, 2);  // spills to heap
  EXPECT_FALSE(v.is_small());
  ASSERT_EQ(v.size(), 6u);
  for (size_t i = 0; i < 6; ++i)
    EXPECT_EQ(v[i], src[i]);  // values preserved across the spill
}
 
TEST(SmallVector, AppendRangeOfZeroIsANoOp)
{
  SmallVector<int, 4> v = {1, 2, 3};
  v.append_range(nullptr, 0);  // count == 0: first is never read
  EXPECT_EQ(v.size(), 3u);
  EXPECT_TRUE(v.is_small());
}
 
TEST(SmallVector, AppendRangeRejectsNullSourceWhenCountIsPositive)
{
  SmallVector<int, 4> v = {1, 2, 3};
  EXPECT_THROW(v.append_range(nullptr, 1), std::invalid_argument);
  // Rejected before touching the vector: size/contents unchanged.
  EXPECT_EQ(v.size(), 3u);
  EXPECT_EQ(v[0], 1);
  EXPECT_EQ(v[1], 2);
  EXPECT_EQ(v[2], 3);
}
 
TEST(SmallVector, AppendRangeSingleCallGrowsAtMostOnce)
{
  // Appending a range larger than the remaining inline capacity in one
  // append_range() call should grow exactly once to fit the whole range,
  // not incrementally (verified indirectly: capacity right after the call
  // already accommodates the full new size without a second, separate
  // growth having been needed -- consistent with a single `grow()` call).
  SmallVector<int, 2> v = {1};
  const int src[] = {2, 3, 4, 5, 6};
  v.append_range(src, 5);
  ASSERT_EQ(v.size(), 6u);
  EXPECT_GE(v.capacity(), 6u);
  for (size_t i = 0; i < 5; ++i)
    EXPECT_EQ(v[i + 1], src[i]);
}
 
TEST(SmallVector, AppendRangeNonTrivialTypeKeepsLifetimesBalanced)
{
  ASSERT_EQ(Probe::live, 0);
  {
    Probe src[3] = {Probe(1), Probe(2), Probe(3)};
    EXPECT_EQ(Probe::live, 3);
 
    SmallVector<Probe, 2> v;
    v.append_range(src, 3);  // spills: goes through the placement-new path
    EXPECT_EQ(Probe::live, 6);  // 3 sources + 3 copies
    ASSERT_EQ(v.size(), 3u);
    EXPECT_EQ(v[0].value, 1);
    EXPECT_EQ(v[1].value, 2);
    EXPECT_EQ(v[2].value, 3);
  }
  EXPECT_EQ(Probe::live, 0);  // both the sources and the copies were destroyed
}
 
TEST(SmallVector, AppendRangeFailedCopyLeavesSizeUnchangedAndNoLeak)
{
  ASSERT_EQ(Throwing_Copy::live, 0);
 
  Throwing_Copy src[4] = {Throwing_Copy(1), Throwing_Copy(2),
                           Throwing_Copy(3), Throwing_Copy(4)};
  {
    SmallVector<Throwing_Copy, 8> v;  // stays inline: exercises the
                                       // placement-new-loop branch, not a
                                       // reallocation-triggered one.
    Throwing_Copy::reset(2);  // 3rd element's copy throws
    EXPECT_THROW(v.append_range(src, 4), std::runtime_error);
    // Strong guarantee: no partially-copied elements remain visible.
    EXPECT_EQ(v.size(), 0u);
    EXPECT_EQ(Throwing_Copy::live, 4);  // only the 4 sources are still alive
  }
  Throwing_Copy::reset(-1);
  EXPECT_EQ(Throwing_Copy::live, 4);
}