//// Dis VM// File: vm_memory.h// Author: arr// #ifndef _DISVM_SRC_INCLUDE_VM_MEMORY_H_#define _DISVM_SRC_INCLUDE_VM_MEMORY_H_ #include <cstdint>#include <cassert>#include <limits>#include <mutex>#include <memory>#include <bitset>#include <functional>#include "runtime.h" namespace disvm{    namespace runtime    {        class global_alloc_lock_t final        {        public:            global_alloc_lock_t(const global_alloc_lock_t &) = delete;            global_alloc_lock_t& operator=(const global_alloc_lock_t &) = delete;             global_alloc_lock_t(global_alloc_lock_t &&);             ~global_alloc_lock_t();         private:            bool _owner;            global_alloc_lock_t(bool owner);            friend global_alloc_lock_t get_global_alloc_lock();        };         // Take the global allocation lock for the VM heap.        // While this lock is taken all further allocations will block.        global_alloc_lock_t get_global_alloc_lock();         // Allocate memory from the VM heap        void *alloc_memory(std::size_t amount_in_bytes);         template<typename T>        T *alloc_memory(std::size_t amount_in_bytes = sizeof(T))        {            return reinterpret_cast<T *>(alloc_memory(amount_in_bytes));        }         // Allocate memory from the VM heap and initialize to 0.        void *calloc_memory(std::size_t amount_in_bytes);         template<typename T>        T *calloc_memory(std::size_t amount_in_bytes = sizeof(T))        {            return reinterpret_cast<T *>(calloc_memory(amount_in_bytes));        }         // Free memory on the VM heap        void free_memory(void *memory);         // Initialize supplied memory based on the type descriptor        void init_memory(const type_descriptor_t &type_desc, void *data);         // Destroy supplied memory based on the type descriptor        void destroy_memory(const type_descriptor_t &type_desc, void *data);         // Increment the ref count of all points in the supplied memory allocation        void inc_ref_count_in_memory(const type_descriptor_t &type_desc, void *data);         // Decrement the ref count and if 0 free the allocation        void dec_ref_count_and_free(vm_alloc_t *alloc);         // Callback for a pointer field supplying the pointer and byte offset        using pointer_field_callback_t = std::function<void(pointer_t, std::size_t)>;         // The callback will be called on all non-null pointer fields.        inline void enum_pointer_fields(const type_descriptor_t &type_desc, void *data, pointer_field_callback_t callback)        {            assert(data != nullptr && callback != nullptr);            if (type_desc.size_in_bytes == 0)                return;             auto offset_accum = std::size_t{ 0 };            auto memory = reinterpret_cast<word_t *>(data);            for (auto i = word_t{ 0 }; i < type_desc.map_in_bytes; ++i, memory += 8, offset_accum += 8)            {                const auto words8 = type_desc.pointer_map[i];                if (words8 != 0)                {                    const auto flags = std::bitset<sizeof(words8) * 8>{ words8 };                     // Enumerating the flags in reverse order so memory access is sequential.                    if (flags[7] && (memory[0] != runtime_constants::nil)) callback(reinterpret_cast<pointer_t>(memory[0]), offset_accum);                    if (flags[6] && (memory[1] != runtime_constants::nil)) callback(reinterpret_cast<pointer_t>(memory[1]), offset_accum + (1 * sizeof(pointer_t)));                    if (flags[5] && (memory[2] != runtime_constants::nil)) callback(reinterpret_cast<pointer_t>(memory[2]), offset_accum + (2 * sizeof(pointer_t)));                    if (flags[4] && (memory[3] != runtime_constants::nil)) callback(reinterpret_cast<pointer_t>(memory[3]), offset_accum + (3 * sizeof(pointer_t)));                    if (flags[3] && (memory[4] != runtime_constants::nil)) callback(reinterpret_cast<pointer_t>(memory[4]), offset_accum + (4 * sizeof(pointer_t)));                    if (flags[2] && (memory[5] != runtime_constants::nil)) callback(reinterpret_cast<pointer_t>(memory[5]), offset_accum + (5 * sizeof(pointer_t)));                    if (flags[1] && (memory[6] != runtime_constants::nil)) callback(reinterpret_cast<pointer_t>(memory[6]), offset_accum + (6 * sizeof(pointer_t)));                    if (flags[0] && (memory[7] != runtime_constants::nil)) callback(reinterpret_cast<pointer_t>(memory[7]), offset_accum + (7 * sizeof(pointer_t)));                }            }        }         // Check if a specific pointer-sized offset in a type represents a pointer        inline bool is_offset_pointer(const type_descriptor_t &type_desc, std::size_t offset)        {            if (type_desc.size_in_bytes == 0)                return false;             assert(offset < static_cast<std::size_t>(std::numeric_limits<word_t>::max()));            const auto byte_offset = static_cast<word_t>(offset / 8);             // Highest order bit is the first field            const auto bit_offset = 7 - (offset % 8);            if (byte_offset < type_desc.map_in_bytes)            {                const auto words8 = type_desc.pointer_map[byte_offset];                if (words8 != 0)                {                    const auto flags = std::bitset<sizeof(words8) * 8>{ words8 };                    return flags[bit_offset];                }            }             return false;        }    }} #endif // _DISVM_SRC_INCLUDE_VM_MEMORY_H_