SkTemplates.h | Explore in Territory

/*
 * Copyright 2006 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkTemplates_DEFINED
#define SkTemplates_DEFINED

#include "include/private/base/SkAlign.h"
#include "include/private/base/SkAssert.h"
#include "include/private/base/SkDebug.h"
#include "include/private/base/SkMalloc.h"
#include "include/private/base/SkTLogic.h"
#include "include/private/base/SkTo.h"

#include <array>
#include <cstddef>
#include <cstdint>
#include <cstring>
#include <memory>
#include <type_traits>
#include <utility>


/** \file SkTemplates.h

    This file contains light-weight template classes for type-safe and exception-safe
    resource management.
*/

/**
 *  Marks a local variable as known to be unused (to avoid warnings).
 *  Note that this does *not* prevent the local variable from being optimized away.
 */
template<typename T> inline void sk_ignore_unused_variable(const T&) { … }

/**
 * This is a general purpose absolute-value function.
 * See SkAbs32 in (SkSafe32.h) for a 32-bit int specific version that asserts.
 */
template <typename T> static inline T SkTAbs(T value) { … }

/**
 *  Returns a pointer to a D which comes immediately after S[count].
 */
template <typename D, typename S> inline D* SkTAfter(S* ptr, size_t count = 1) { … }

/**
 *  Returns a pointer to a D which comes byteOffset bytes after S.
 */
template <typename D, typename S> inline D* SkTAddOffset(S* ptr, ptrdiff_t byteOffset) { … }

template <typename T, T* P> struct SkOverloadedFunctionObject { … };

SkFunctionObject;

/** \class SkAutoTCallVProc

    Call a function when this goes out of scope. The template uses two
    parameters, the object, and a function that is to be called in the destructor.
    If release() is called, the object reference is set to null. If the object
    reference is null when the destructor is called, we do not call the
    function.
*/
template <typename T, void (*P)(T*)> class SkAutoTCallVProc
    : public std::unique_ptr<T, SkFunctionObject<P>> { … };


namespace skia_private {
/** Allocate an array of T elements, and free the array in the destructor
 */
template <typename T> class AutoTArray  { … };

/** Wraps AutoTArray, with room for kCountRequested elements preallocated.
 */
template <int kCountRequested, typename T> class AutoSTArray { … };

/** Manages an array of T elements, freeing the array in the destructor.
 *  Does NOT call any constructors/destructors on T (T must be POD).
 */
template <typename T,
          typename = std::enable_if_t<std::is_trivially_default_constructible<T>::value &&
                                      std::is_trivially_destructible<T>::value>>
class AutoTMalloc  {
public:
    /** Takes ownership of the ptr. The ptr must be a value which can be passed to sk_free. */
    explicit AutoTMalloc(T* ptr = nullptr) : … { … }

    /** Allocates space for 'count' Ts. */
    explicit AutoTMalloc(size_t count)
        : … { … }

    AutoTMalloc(AutoTMalloc&&) = default;
    AutoTMalloc& operator=(AutoTMalloc&&) = default;

    /** Resize the memory area pointed to by the current ptr preserving contents. */
    void realloc(size_t count) { … }

    /** Resize the memory area pointed to by the current ptr without preserving contents. */
    T* reset(size_t count = 0) { … }

    T* get() const { … }

    operator T*() { return fPtr.get(); }

    operator const T*() const { return fPtr.get(); }

    T& operator[](int index) { … }

    const T& operator[](int index) const { … }

    /** Aliases matching other types, like std::vector. */
    const T* data() const { … }
    T* data() { … }

    /**
     *  Transfer ownership of the ptr to the caller, setting the internal
     *  pointer to NULL. Note that this differs from get(), which also returns
     *  the pointer, but it does not transfer ownership.
     */
    T* release() { … }

private:
    std::unique_ptr<T, SkOverloadedFunctionObject<void(void*), sk_free>> fPtr;
};

template <size_t kCountRequested,
          typename T,
          typename = std::enable_if_t<std::is_trivially_default_constructible<T>::value &&
                                      std::is_trivially_destructible<T>::value>>
class AutoSTMalloc {
public:
    AutoSTMalloc() : … { … }

    AutoSTMalloc(size_t count) { … }

    AutoSTMalloc(AutoSTMalloc&&) = delete;
    AutoSTMalloc(const AutoSTMalloc&) = delete;
    AutoSTMalloc& operator=(AutoSTMalloc&&) = delete;
    AutoSTMalloc& operator=(const AutoSTMalloc&) = delete;

    ~AutoSTMalloc() { … }

    // doesn't preserve contents
    T* reset(size_t count) { … }

    T* get() const { … }

    operator T*() {
        return fPtr;
    }

    operator const T*() const {
        return fPtr;
    }

    T& operator[](int index) { … }

    const T& operator[](int index) const { … }

    /** Aliases matching other types, like std::vector. */
    const T* data() const { … }
    T* data() { … }

    // Reallocs the array, can be used to shrink the allocation.  Makes no attempt to be intelligent
    void realloc(size_t count) { … }

private:
    // Since we use uint32_t storage, we might be able to get more elements for free.
    static const size_t kCountWithPadding = SkAlign4(kCountRequested*sizeof(T)) / sizeof(T);
#if defined(SK_BUILD_FOR_GOOGLE3)
    // Stack frame size is limited for SK_BUILD_FOR_GOOGLE3. 4k is less than the actual max, but some functions
    // have multiple large stack allocations.
    static const size_t kMaxBytes = 4 * 1024;
    static const size_t kCount = kCountRequested * sizeof(T) > kMaxBytes
        ? kMaxBytes / sizeof(T)
        : kCountWithPadding;
#else
    static const size_t kCount = kCountWithPadding;
#endif

    T*          fPtr;
    union {
        uint32_t    fStorage32[SkAlign4(kCount*sizeof(T)) >> 2];
        T           fTStorage[1];   // do NOT want to invoke T::T()
    };
};

UniqueVoidPtr;

}  // namespace skia_private

template<typename C, std::size_t... Is>
constexpr auto SkMakeArrayFromIndexSequence(C c, std::index_sequence<Is...> is)
-> std::array<decltype(c(std::declval<typename decltype(is)::value_type>())), sizeof...(Is)> { … }

template<size_t N, typename C> constexpr auto SkMakeArray(C c)
-> std::array<decltype(c(std::declval<typename std::index_sequence<N>::value_type>())), N> { … }

#endif
chromium/third_party/skia/include/private/base/SkTemplates.h
