transmission/libtransmission/ptrarray.cc

// This file Copyright 2008-2022 Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.

#include <algorithm>
#include <cstring> /* memmove */

#include "ptrarray.h"
#include "tr-assert.h"
#include "tr-macros.h"
#include "utils.h"

static auto constexpr Floor = int{ 32 };

int tr_lowerBound(
    void const* key,
    void const* base,
    size_t nmemb,
    size_t size,
    tr_voidptr_compare_func compar,
    bool* exact_match)
{
    size_t first = 0;
    auto const* cbase = static_cast<char const*>(base);
    bool exact = false;

    while (nmemb != 0)
    {
        size_t const half = nmemb / 2;
        size_t const middle = first + half;
        int const c = (*compar)(key, cbase + size * middle);

        if (c <= 0)
        {
            if (c == 0)
            {
                exact = true;
            }

            nmemb = half;
        }
        else
        {
            first = middle + 1;
            nmemb = nmemb - half - 1;
        }
    }

    *exact_match = exact;
    return first;
}

void tr_ptrArrayDestruct(tr_ptrArray* p, PtrArrayForeachFunc func)
{
    TR_ASSERT(p != nullptr);
    TR_ASSERT(p->items != nullptr || p->n_items == 0);

    if (func != nullptr)
    {
        tr_ptrArrayForeach(p, func);
    }

    tr_free(p->items);
}

void tr_ptrArrayForeach(tr_ptrArray* t, PtrArrayForeachFunc func)
{
    TR_ASSERT(t != nullptr);
    TR_ASSERT(t->items != nullptr || t->n_items == 0);
    TR_ASSERT(func != nullptr);

    for (int i = 0; i < t->n_items; ++i)
    {
        func(t->items[i]);
    }
}

void** tr_ptrArrayPeek(tr_ptrArray* t, int* size)
{
    *size = t->n_items;
    return t->items;
}

int tr_ptrArrayInsert(tr_ptrArray* t, void* ptr, int pos)
{
    if (t->n_items >= t->n_alloc)
    {
        t->n_alloc = std::max(Floor, t->n_alloc * 2);
        t->items = tr_renew(void*, t->items, t->n_alloc);
    }

    if (pos < 0 || pos > t->n_items)
    {
        pos = t->n_items;
    }
    else
    {
        memmove(t->items + pos + 1, t->items + pos, sizeof(void*) * (t->n_items - pos));
    }

    t->items[pos] = ptr;
    t->n_items++;
    return pos;
}

void tr_ptrArrayErase(tr_ptrArray* t, int begin, int end)
{
    if (end < 0)
    {
        end = t->n_items;
    }

    TR_ASSERT(begin >= 0);
    TR_ASSERT(begin < end);
    TR_ASSERT(end <= t->n_items);

    memmove(t->items + begin, t->items + end, sizeof(void*) * (t->n_items - end));

    t->n_items -= end - begin;
}

/**
***
**/

int tr_ptrArrayLowerBound(tr_ptrArray const* t, void const* ptr, tr_voidptr_compare_func compare, bool* exact_match)
{
    int pos = -1;
    bool match = false;

    if (t->n_items == 0)
    {
        pos = 0;
    }
    else
    {
        int first = 0;
        int last = t->n_items - 1;

        for (;;)
        {
            int const half = (last - first) / 2;
            int const c = compare(t->items[first + half], ptr);

            if (c < 0)
            {
                int const new_first = first + half + 1;

                if (new_first > last)
                {
                    pos = new_first;
                    break;
                }

                first = new_first;
            }
            else if (c > 0)
            {
                int const new_last = first + half - 1;

                if (new_last < first)
                {
                    pos = first;
                    break;
                }

                last = new_last;
            }
            else
            {
                match = true;
                pos = first + half;
                break;
            }
        }
    }

    if (exact_match != nullptr)
    {
        *exact_match = match;
    }

    return pos;
}

#ifndef TR_ENABLE_ASSERTS

#define assertArrayIsSortedAndUnique(array, compare) /* no-op */
#define assertIndexIsSortedAndUnique(array, pos, compare) /* no-op */

#else

static void assertArrayIsSortedAndUnique(tr_ptrArray const* t, tr_voidptr_compare_func compare)
{
    if (t->items == nullptr)
    {
        TR_ASSERT(t->n_items == 0);
    }
    else
    {
        for (int i = 0; i < t->n_items - 2; ++i)
        {
            TR_ASSERT(compare(t->items[i], t->items[i + 1]) < 0);
        }
    }
}

static void assertIndexIsSortedAndUnique(tr_ptrArray const* t, int pos, tr_voidptr_compare_func compare)
{
    if (pos > 0)
    {
        TR_ASSERT(compare(t->items[pos - 1], t->items[pos]) < 0);
    }

    if (pos + 1 < t->n_items)
    {
        TR_ASSERT(compare(t->items[pos], t->items[pos + 1]) < 0);
    }
}

#endif

int tr_ptrArrayInsertSorted(tr_ptrArray* t, void* ptr, tr_voidptr_compare_func compare)
{
    assertArrayIsSortedAndUnique(t, compare);

    int const pos = tr_ptrArrayLowerBound(t, ptr, compare, nullptr);
    int const ret = tr_ptrArrayInsert(t, ptr, pos);

    assertIndexIsSortedAndUnique(t, ret, compare);
    return ret;
}

void* tr_ptrArrayFindSorted(tr_ptrArray* t, void const* ptr, tr_voidptr_compare_func compare)
{
    bool match = false;
    int const pos = tr_ptrArrayLowerBound(t, ptr, compare, &match);
    return match ? t->items[pos] : nullptr;
}

static void* tr_ptrArrayRemoveSortedValue(tr_ptrArray* t, void const* ptr, tr_voidptr_compare_func compare)
{
    void* ret = nullptr;

    assertArrayIsSortedAndUnique(t, compare);

    bool match = false;
    int const pos = tr_ptrArrayLowerBound(t, ptr, compare, &match);

    if (match)
    {
        ret = t->items[pos];
        TR_ASSERT(compare(ret, ptr) == 0);
        tr_ptrArrayErase(t, pos, pos + 1);
    }

    TR_ASSERT(ret == nullptr || compare(ret, ptr) == 0);
    return ret;
}

void tr_ptrArrayRemoveSortedPointer(tr_ptrArray* t, void const* ptr, tr_voidptr_compare_func compare)
{
    [[maybe_unused]] void const* removed = tr_ptrArrayRemoveSortedValue(t, ptr, compare);

    TR_ASSERT(removed != nullptr);
    TR_ASSERT(removed == ptr);
    TR_ASSERT(tr_ptrArrayFindSorted(t, ptr, compare) == nullptr);
}

void* tr_ptrArrayNth(tr_ptrArray* array, int i)
{
    TR_ASSERT(array != nullptr);
    TR_ASSERT(i >= 0);
    TR_ASSERT(i < array->n_items);

    return array->items[i];
}