From 114b5812f6283f2325fc31e186b26c6d76f9551a Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter.wuille@gmail.com>
Date: Thu, 29 Oct 2015 07:11:24 +0100
Subject: Prevector type

---
 src/prevector.h | 486 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 486 insertions(+)
 create mode 100644 src/prevector.h

(limited to 'src/prevector.h')

diff --git a/src/prevector.h b/src/prevector.h
new file mode 100644
index 0000000000..3e80ef5d33
--- /dev/null
+++ b/src/prevector.h
@@ -0,0 +1,486 @@
+#ifndef _BITCOIN_PREVECTOR_H_
+#define _BITCOIN_PREVECTOR_H_
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+
+#include <iterator>
+
+#pragma pack(push, 1)
+/** Implements a drop-in replacement for std::vector<T> which stores up to N
+ *  elements directly (without heap allocation). The types Size and Diff are
+ *  used to store element counts, and can be any unsigned + signed type.
+ *
+ *  Storage layout is either:
+ *  - Direct allocation:
+ *    - Size _size: the number of used elements (between 0 and N)
+ *    - T direct[N]: an array of N elements of type T
+ *      (only the first _size are initialized).
+ *  - Indirect allocation:
+ *    - Size _size: the number of used elements plus N + 1
+ *    - Size capacity: the number of allocated elements
+ *    - T* indirect: a pointer to an array of capacity elements of type T
+ *      (only the first _size are initialized).
+ *
+ *  The data type T must be movable by memmove/realloc(). Once we switch to C++,
+ *  move constructors can be used instead.
+ */
+template<unsigned int N, typename T, typename Size = uint32_t, typename Diff = int32_t>
+class prevector {
+public:
+    typedef Size size_type;
+    typedef Diff difference_type;
+    typedef T value_type;
+    typedef value_type& reference;
+    typedef const value_type& const_reference;
+    typedef value_type* pointer;
+    typedef const value_type* const_pointer;
+
+    class iterator {
+        T* ptr;
+    public:
+        typedef Diff difference_type;
+        typedef T value_type;
+        typedef T* pointer;
+        typedef T& reference;
+        typedef std::random_access_iterator_tag iterator_category;
+        iterator(T* ptr_) : ptr(ptr_) {}
+        T& operator*() const { return *ptr; }
+        T* operator->() const { return ptr; }
+        T& operator[](size_type pos) { return ptr[pos]; }
+        const T& operator[](size_type pos) const { return ptr[pos]; }
+        iterator& operator++() { ptr++; return *this; }
+        iterator& operator--() { ptr--; return *this; }
+        iterator operator++(int) { iterator copy(*this); ++(*this); return copy; }
+        iterator operator--(int) { iterator copy(*this); --(*this); return copy; }
+        difference_type friend operator-(iterator a, iterator b) { return (&(*a) - &(*b)); }
+        iterator operator+(size_type n) { return iterator(ptr + n); }
+        iterator& operator+=(size_type n) { ptr += n; return *this; }
+        iterator operator-(size_type n) { return iterator(ptr - n); }
+        iterator& operator-=(size_type n) { ptr -= n; return *this; }
+        bool operator==(iterator x) const { return ptr == x.ptr; }
+        bool operator!=(iterator x) const { return ptr != x.ptr; }
+        bool operator>=(iterator x) const { return ptr >= x.ptr; }
+        bool operator<=(iterator x) const { return ptr <= x.ptr; }
+        bool operator>(iterator x) const { return ptr > x.ptr; }
+        bool operator<(iterator x) const { return ptr < x.ptr; }
+    };
+
+    class reverse_iterator {
+        T* ptr;
+    public:
+        typedef Diff difference_type;
+        typedef T value_type;
+        typedef T* pointer;
+        typedef T& reference;
+        typedef std::bidirectional_iterator_tag iterator_category;
+        reverse_iterator(T* ptr_) : ptr(ptr_) {}
+        T& operator*() { return *ptr; }
+        const T& operator*() const { return *ptr; }
+        T* operator->() { return ptr; }
+        const T* operator->() const { return ptr; }
+        reverse_iterator& operator--() { ptr++; return *this; }
+        reverse_iterator& operator++() { ptr--; return *this; }
+        reverse_iterator operator++(int) { reverse_iterator copy(*this); ++(*this); return copy; }
+        reverse_iterator operator--(int) { reverse_iterator copy(*this); --(*this); return copy; }
+        bool operator==(reverse_iterator x) const { return ptr == x.ptr; }
+        bool operator!=(reverse_iterator x) const { return ptr != x.ptr; }
+    };
+
+    class const_iterator {
+        const T* ptr;
+    public:
+        typedef Diff difference_type;
+        typedef const T value_type;
+        typedef const T* pointer;
+        typedef const T& reference;
+        typedef std::random_access_iterator_tag iterator_category;
+        const_iterator(const T* ptr_) : ptr(ptr_) {}
+        const_iterator(iterator x) : ptr(&(*x)) {}
+        const T& operator*() const { return *ptr; }
+        const T* operator->() const { return ptr; }
+        const T& operator[](size_type pos) const { return ptr[pos]; }
+        const_iterator& operator++() { ptr++; return *this; }
+        const_iterator& operator--() { ptr--; return *this; }
+        const_iterator operator++(int) { const_iterator copy(*this); ++(*this); return copy; }
+        const_iterator operator--(int) { const_iterator copy(*this); --(*this); return copy; }
+        difference_type friend operator-(const_iterator a, const_iterator b) { return (&(*a) - &(*b)); }
+        const_iterator operator+(size_type n) { return const_iterator(ptr + n); }
+        const_iterator& operator+=(size_type n) { ptr += n; return *this; }
+        const_iterator operator-(size_type n) { return const_iterator(ptr - n); }
+        const_iterator& operator-=(size_type n) { ptr -= n; return *this; }
+        bool operator==(const_iterator x) const { return ptr == x.ptr; }
+        bool operator!=(const_iterator x) const { return ptr != x.ptr; }
+        bool operator>=(const_iterator x) const { return ptr >= x.ptr; }
+        bool operator<=(const_iterator x) const { return ptr <= x.ptr; }
+        bool operator>(const_iterator x) const { return ptr > x.ptr; }
+        bool operator<(const_iterator x) const { return ptr < x.ptr; }
+    };
+
+    class const_reverse_iterator {
+        const T* ptr;
+    public:
+        typedef Diff difference_type;
+        typedef const T value_type;
+        typedef const T* pointer;
+        typedef const T& reference;
+        typedef std::bidirectional_iterator_tag iterator_category;
+        const_reverse_iterator(T* ptr_) : ptr(ptr_) {}
+        const_reverse_iterator(reverse_iterator x) : ptr(&(*x)) {}
+        const T& operator*() const { return *ptr; }
+        const T* operator->() const { return ptr; }
+        const_reverse_iterator& operator--() { ptr++; return *this; }
+        const_reverse_iterator& operator++() { ptr--; return *this; }
+        const_reverse_iterator operator++(int) { const_reverse_iterator copy(*this); ++(*this); return copy; }
+        const_reverse_iterator operator--(int) { const_reverse_iterator copy(*this); --(*this); return copy; }
+        bool operator==(const_reverse_iterator x) const { return ptr == x.ptr; }
+        bool operator!=(const_reverse_iterator x) const { return ptr != x.ptr; }
+    };
+
+private:
+    size_type _size;
+    union {
+        char direct[sizeof(T) * N];
+        struct {
+            size_type capacity;
+            char* indirect;
+        };
+    } _union;
+
+    T* direct_ptr(difference_type pos) { return reinterpret_cast<T*>(_union.direct) + pos; }
+    const T* direct_ptr(difference_type pos) const { return reinterpret_cast<const T*>(_union.direct) + pos; }
+    T* indirect_ptr(difference_type pos) { return reinterpret_cast<T*>(_union.indirect) + pos; }
+    const T* indirect_ptr(difference_type pos) const { return reinterpret_cast<const T*>(_union.indirect) + pos; }
+    bool is_direct() const { return _size <= N; }
+
+    void change_capacity(size_type new_capacity) {
+        if (new_capacity <= N) {
+            if (!is_direct()) {
+                T* indirect = indirect_ptr(0);
+                T* src = indirect;
+                T* dst = direct_ptr(0);
+                memcpy(dst, src, size() * sizeof(T));
+                free(indirect);
+                _size -= N + 1;
+            }
+        } else {
+            if (!is_direct()) {
+                _union.indirect = static_cast<char*>(realloc(_union.indirect, ((size_t)sizeof(T)) * new_capacity));
+                _union.capacity = new_capacity;
+            } else {
+                char* new_indirect = static_cast<char*>(malloc(((size_t)sizeof(T)) * new_capacity));
+                T* src = direct_ptr(0);
+                T* dst = reinterpret_cast<T*>(new_indirect);
+                memcpy(dst, src, size() * sizeof(T));
+                _union.indirect = new_indirect;
+                _union.capacity = new_capacity;
+                _size += N + 1;
+            }
+        }
+    }
+
+    T* item_ptr(difference_type pos) { return is_direct() ? direct_ptr(pos) : indirect_ptr(pos); }
+    const T* item_ptr(difference_type pos) const { return is_direct() ? direct_ptr(pos) : indirect_ptr(pos); }
+
+public:
+    void assign(size_type n, const T& val) {
+        clear();
+        if (capacity() < n) {
+            change_capacity(n);
+        }
+        while (size() < n) {
+            _size++;
+            new(static_cast<void*>(item_ptr(size() - 1))) T(val);
+        }
+    }
+
+    template<typename InputIterator>
+    void assign(InputIterator first, InputIterator last) {
+        size_type n = last - first;
+        clear();
+        if (capacity() < n) {
+            change_capacity(n);
+        }
+        while (first != last) {
+            _size++;
+            new(static_cast<void*>(item_ptr(size() - 1))) T(*first);
+            ++first;
+        }
+    }
+
+    prevector() : _size(0) {}
+
+    explicit prevector(size_type n) : _size(0) {
+        resize(n);
+    }
+
+    explicit prevector(size_type n, const T& val = T()) : _size(0) {
+        change_capacity(n);
+        while (size() < n) {
+            _size++;
+            new(static_cast<void*>(item_ptr(size() - 1))) T(val);
+        }
+    }
+
+    template<typename InputIterator>
+    prevector(InputIterator first, InputIterator last) : _size(0) {
+        size_type n = last - first;
+        change_capacity(n);
+        while (first != last) {
+            _size++;
+            new(static_cast<void*>(item_ptr(size() - 1))) T(*first);
+            ++first;
+        }
+    }
+
+    prevector(const prevector<N, T, Size, Diff>& other) : _size(0) {
+        change_capacity(other.size());
+        const_iterator it = other.begin();
+        while (it != other.end()) {
+            _size++;
+            new(static_cast<void*>(item_ptr(size() - 1))) T(*it);
+            ++it;
+        }
+    }
+
+    prevector& operator=(const prevector<N, T, Size, Diff>& other) {
+        if (&other == this) {
+            return *this;
+        }
+        resize(0);
+        change_capacity(other.size());
+        const_iterator it = other.begin();
+        while (it != other.end()) {
+            _size++;
+            new(static_cast<void*>(item_ptr(size() - 1))) T(*it);
+            ++it;
+        }
+        return *this;
+    }
+
+    size_type size() const {
+        return is_direct() ? _size : _size - N - 1;
+    }
+
+    bool empty() const {
+        return size() == 0;
+    }
+
+    iterator begin() { return iterator(item_ptr(0)); }
+    const_iterator begin() const { return const_iterator(item_ptr(0)); }
+    iterator end() { return iterator(item_ptr(size())); }
+    const_iterator end() const { return const_iterator(item_ptr(size())); }
+
+    reverse_iterator rbegin() { return reverse_iterator(item_ptr(size() - 1)); }
+    const_reverse_iterator rbegin() const { return const_reverse_iterator(item_ptr(size() - 1)); }
+    reverse_iterator rend() { return reverse_iterator(item_ptr(-1)); }
+    const_reverse_iterator rend() const { return const_reverse_iterator(item_ptr(-1)); }
+
+    size_t capacity() const {
+        if (is_direct()) {
+            return N;
+        } else {
+            return _union.capacity;
+        }
+    }
+
+    T& operator[](size_type pos) {
+        return *item_ptr(pos);
+    }
+
+    const T& operator[](size_type pos) const {
+        return *item_ptr(pos);
+    }
+
+    void resize(size_type new_size) {
+        while (size() > new_size) {
+            item_ptr(size() - 1)->~T();
+            _size--;
+        }
+        if (new_size > capacity()) {
+            change_capacity(new_size);
+        }
+        while (size() < new_size) {
+            _size++;
+            new(static_cast<void*>(item_ptr(size() - 1))) T();
+        }
+    }
+
+    void reserve(size_type new_capacity) {
+        if (new_capacity > capacity()) {
+            change_capacity(new_capacity);
+        }
+    }
+
+    void shrink_to_fit() {
+        change_capacity(size());
+    }
+
+    void clear() {
+        resize(0);
+    }
+
+    iterator insert(iterator pos, const T& value) {
+        size_type p = pos - begin();
+        size_type new_size = size() + 1;
+        if (capacity() < new_size) {
+            change_capacity(new_size + (new_size >> 1));
+        }
+        memmove(item_ptr(p + 1), item_ptr(p), (size() - p) * sizeof(T));
+        _size++;
+        new(static_cast<void*>(item_ptr(p))) T(value);
+        return iterator(item_ptr(p));
+    }
+
+    void insert(iterator pos, size_type count, const T& value) {
+        size_type p = pos - begin();
+        size_type new_size = size() + count;
+        if (capacity() < new_size) {
+            change_capacity(new_size + (new_size >> 1));
+        }
+        memmove(item_ptr(p + count), item_ptr(p), (size() - p) * sizeof(T));
+        _size += count;
+        for (size_type i = 0; i < count; i++) {
+            new(static_cast<void*>(item_ptr(p + i))) T(value);
+        }
+    }
+
+    template<typename InputIterator>
+    void insert(iterator pos, InputIterator first, InputIterator last) {
+        size_type p = pos - begin();
+        difference_type count = last - first;
+        size_type new_size = size() + count;
+        if (capacity() < new_size) {
+            change_capacity(new_size + (new_size >> 1));
+        }
+        memmove(item_ptr(p + count), item_ptr(p), (size() - p) * sizeof(T));
+        _size += count;
+        while (first != last) {
+            new(static_cast<void*>(item_ptr(p))) T(*first);
+            ++p;
+            ++first;
+        }
+    }
+
+    iterator erase(iterator pos) {
+        (*pos).~T();
+        memmove(&(*pos), &(*pos) + 1, ((char*)&(*end())) - ((char*)(1 + &(*pos))));
+        _size--;
+        return pos;
+    }
+
+    iterator erase(iterator first, iterator last) {
+        iterator p = first;
+        char* endp = (char*)&(*end());
+        while (p != last) {
+            (*p).~T();
+            _size--;
+            ++p;
+        }
+        memmove(&(*first), &(*last), endp - ((char*)(&(*last))));
+        return first;
+    }
+
+    void push_back(const T& value) {
+        size_type new_size = size() + 1;
+        if (capacity() < new_size) {
+            change_capacity(new_size + (new_size >> 1));
+        }
+        new(item_ptr(size())) T(value);
+        _size++;
+    }
+
+    void pop_back() {
+        _size--;
+    }
+
+    T& front() {
+        return *item_ptr(0);
+    }
+
+    const T& front() const {
+        return *item_ptr(0);
+    }
+
+    T& back() {
+        return *item_ptr(size() - 1);
+    }
+
+    const T& back() const {
+        return *item_ptr(size() - 1);
+    }
+
+    void swap(prevector<N, T, Size, Diff>& other) {
+        if (_size & other._size & 1) {
+            std::swap(_union.capacity, other._union.capacity);
+            std::swap(_union.indirect, other._union.indirect);
+        } else {
+            std::swap(_union, other._union);
+        }
+        std::swap(_size, other._size);
+    }
+
+    ~prevector() {
+        clear();
+        if (!is_direct()) {
+            free(_union.indirect);
+            _union.indirect = NULL;
+        }
+    }
+
+    bool operator==(const prevector<N, T, Size, Diff>& other) const {
+        if (other.size() != size()) {
+            return false;
+        }
+        const_iterator b1 = begin();
+        const_iterator b2 = other.begin();
+        const_iterator e1 = end();
+        while (b1 != e1) {
+            if ((*b1) != (*b2)) {
+                return false;
+            }
+            ++b1;
+            ++b2;
+        }
+        return true;
+    }
+
+    bool operator!=(const prevector<N, T, Size, Diff>& other) const {
+        return !(*this == other);
+    }
+
+    bool operator<(const prevector<N, T, Size, Diff>& other) const {
+        if (size() < other.size()) {
+            return true;
+        }
+        if (size() > other.size()) {
+            return false;
+        }
+        const_iterator b1 = begin();
+        const_iterator b2 = other.begin();
+        const_iterator e1 = end();
+        while (b1 != e1) {
+            if ((*b1) < (*b2)) {
+                return true;
+            }
+            if ((*b2) < (*b1)) {
+                return false;
+            }
+            ++b1;
+            ++b2;
+        }
+        return false;
+    }
+
+    size_t allocated_memory() const {
+        if (is_direct()) {
+            return 0;
+        } else {
+            return ((size_t)(sizeof(T))) * _union.capacity;
+        }
+    }
+};
+#pragma pack(pop)
+
+#endif
-- 
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