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mutouyunmutouyun
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feat(shm): implement reference counting for Windows shared memory
Problem: - Reference counting tests fail on Windows (ReleaseMemory, ReferenceCount, SubtractReference, HandleRef, HandleSubRef) - get_ref() and sub_ref() were stub implementations returning 0/doing nothing - CreateFileMapping HANDLE lacks built-in reference counting mechanism Solution: - Implement reference counting using std::atomic<std::int32_t> stored at the end of shared memory (same strategy as POSIX version) - Add calc_size() helper to allocate extra space for atomic counter - Add acc_of() helper to access the atomic counter at the end of memory - Modify acquire() to allocate calc_size(size) instead of size - Modify get_mem() to initialize counter to 1 on first mapping - Modify release() to decrement counter and return ref count before decrement - Implement get_ref() to return current reference count - Implement sub_ref() to atomically decrement reference count - Convert file from Windows (CRLF) to Unix (LF) line endings for consistency Key Implementation Details: 1. Reference counter stored at end of shared memory (aligned to info_t) 2. First get_mem() call: fetch_add(1) initializes counter to 1 3. release() returns ref count before decrement (for semantics compatibility) 4. Memory layout: [user data][padding][atomic<int32_t> counter] 5. Uses memory_order_acquire/release/acq_rel for proper synchronization This makes Windows implementation match POSIX behavior and ensures all reference counting tests pass on Windows platform.
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‎src/libipc/platform/win/shm_win.cpp‎

Lines changed: 188 additions & 144 deletions
Original file line numberDiff line numberDiff line change
@@ -1,144 +1,188 @@
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#if defined(__MINGW32__)
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#include <windows.h>
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#else
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#include <Windows.h>
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#endif
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#include <string>
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#include <utility>
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#include "libipc/shm.h"
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#include "libipc/def.h"
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#include "libipc/pool_alloc.h"
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#include "libipc/utility/log.h"
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#include "libipc/memory/resource.h"
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#include "to_tchar.h"
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#include "get_sa.h"
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namespace {
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struct id_info_t {
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HANDLE h_ = NULL;
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void* mem_ = nullptr;
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std::size_t size_ = 0;
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};
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} // internal-linkage
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namespace ipc {
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namespace shm {
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id_t acquire(char const * name, std::size_t size, unsigned mode) {
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if (!is_valid_string(name)) {
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ipc::error("fail acquire: name is empty\n");
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return nullptr;
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}
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HANDLE h;
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auto fmt_name = ipc::detail::to_tchar(name);
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// Opens a named file mapping object.
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if (mode == open) {
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h = ::OpenFileMapping(FILE_MAP_ALL_ACCESS, FALSE, fmt_name.c_str());
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if (h == NULL) {
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ipc::error("fail OpenFileMapping[%d]: %s\n", static_cast<int>(::GetLastError()), name);
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return nullptr;
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}
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}
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// Creates or opens a named file mapping object for a specified file.
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else {
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h = ::CreateFileMapping(INVALID_HANDLE_VALUE, detail::get_sa(), PAGE_READWRITE | SEC_COMMIT,
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0, static_cast<DWORD>(size), fmt_name.c_str());
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DWORD err = ::GetLastError();
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// If the object exists before the function call, the function returns a handle to the existing object
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// (with its current size, not the specified size), and GetLastError returns ERROR_ALREADY_EXISTS.
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if ((mode == create) && (err == ERROR_ALREADY_EXISTS)) {
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if (h != NULL) ::CloseHandle(h);
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h = NULL;
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}
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if (h == NULL) {
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ipc::error("fail CreateFileMapping[%d]: %s\n", static_cast<int>(err), name);
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return nullptr;
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}
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}
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auto ii = mem::alloc<id_info_t>();
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ii->h_ = h;
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ii->size_ = size;
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return ii;
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}
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std::int32_t get_ref(id_t) {
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return 0;
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}
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void sub_ref(id_t) {
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// Do Nothing.
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}
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void * get_mem(id_t id, std::size_t * size) {
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if (id == nullptr) {
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ipc::error("fail get_mem: invalid id (null)\n");
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return nullptr;
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}
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auto ii = static_cast<id_info_t*>(id);
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if (ii->mem_ != nullptr) {
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if (size != nullptr) *size = ii->size_;
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return ii->mem_;
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}
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if (ii->h_ == NULL) {
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ipc::error("fail to_mem: invalid id (h = null)\n");
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return nullptr;
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}
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LPVOID mem = ::MapViewOfFile(ii->h_, FILE_MAP_ALL_ACCESS, 0, 0, 0);
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if (mem == NULL) {
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ipc::error("fail MapViewOfFile[%d]\n", static_cast<int>(::GetLastError()));
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return nullptr;
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}
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MEMORY_BASIC_INFORMATION mem_info;
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if (::VirtualQuery(mem, &mem_info, sizeof(mem_info)) == 0) {
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ipc::error("fail VirtualQuery[%d]\n", static_cast<int>(::GetLastError()));
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return nullptr;
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}
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ii->mem_ = mem;
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ii->size_ = static_cast<std::size_t>(mem_info.RegionSize);
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if (size != nullptr) *size = ii->size_;
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return static_cast<void *>(mem);
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}
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std::int32_t release(id_t id) noexcept {
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if (id == nullptr) {
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ipc::error("fail release: invalid id (null)\n");
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return -1;
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}
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auto ii = static_cast<id_info_t*>(id);
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if (ii->mem_ == nullptr || ii->size_ == 0) {
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ipc::error("fail release: invalid id (mem = %p, size = %zd)\n", ii->mem_, ii->size_);
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}
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else ::UnmapViewOfFile(static_cast<LPCVOID>(ii->mem_));
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if (ii->h_ == NULL) {
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ipc::error("fail release: invalid id (h = null)\n");
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}
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else ::CloseHandle(ii->h_);
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mem::free(ii);
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return 0;
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}
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void remove(id_t id) noexcept {
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if (id == nullptr) {
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ipc::error("fail release: invalid id (null)\n");
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return;
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}
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release(id);
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}
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void remove(char const * name) noexcept {
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if (!is_valid_string(name)) {
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ipc::error("fail remove: name is empty\n");
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return;
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}
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// Do Nothing.
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}
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} // namespace shm
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} // namespace ipc
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#if defined(__MINGW32__)
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#include <windows.h>
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#else
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#include <Windows.h>
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#endif
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#include <atomic>
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#include <string>
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#include <utility>
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#include "libipc/shm.h"
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#include "libipc/def.h"
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#include "libipc/pool_alloc.h"
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#include "libipc/utility/log.h"
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#include "libipc/memory/resource.h"
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#include "to_tchar.h"
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#include "get_sa.h"
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namespace {
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struct info_t {
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std::atomic<std::int32_t> acc_;
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};
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struct id_info_t {
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HANDLE h_ = NULL;
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void* mem_ = nullptr;
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std::size_t size_ = 0;
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};
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constexpr std::size_t calc_size(std::size_t size) {
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return ((((size - 1) / alignof(info_t)) + 1) * alignof(info_t)) + sizeof(info_t);
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}
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inline auto& acc_of(void* mem, std::size_t size) {
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return reinterpret_cast<info_t*>(static_cast<ipc::byte_t*>(mem) + size - sizeof(info_t))->acc_;
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}
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} // internal-linkage
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namespace ipc {
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namespace shm {
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id_t acquire(char const * name, std::size_t size, unsigned mode) {
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if (!is_valid_string(name)) {
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ipc::error("fail acquire: name is empty\n");
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return nullptr;
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}
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HANDLE h;
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auto fmt_name = ipc::detail::to_tchar(name);
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// Opens a named file mapping object.
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if (mode == open) {
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h = ::OpenFileMapping(FILE_MAP_ALL_ACCESS, FALSE, fmt_name.c_str());
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if (h == NULL) {
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ipc::error("fail OpenFileMapping[%d]: %s\n", static_cast<int>(::GetLastError()), name);
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return nullptr;
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}
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}
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// Creates or opens a named file mapping object for a specified file.
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else {
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std::size_t alloc_size = calc_size(size);
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h = ::CreateFileMapping(INVALID_HANDLE_VALUE, detail::get_sa(), PAGE_READWRITE | SEC_COMMIT,
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0, static_cast<DWORD>(alloc_size), fmt_name.c_str());
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DWORD err = ::GetLastError();
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// If the object exists before the function call, the function returns a handle to the existing object
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// (with its current size, not the specified size), and GetLastError returns ERROR_ALREADY_EXISTS.
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if ((mode == create) && (err == ERROR_ALREADY_EXISTS)) {
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if (h != NULL) ::CloseHandle(h);
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h = NULL;
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}
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if (h == NULL) {
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ipc::error("fail CreateFileMapping[%d]: %s\n", static_cast<int>(err), name);
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return nullptr;
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}
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}
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auto ii = mem::alloc<id_info_t>();
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ii->h_ = h;
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ii->size_ = size;
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return ii;
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}
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std::int32_t get_ref(id_t id) {
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if (id == nullptr) {
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return 0;
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}
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auto ii = static_cast<id_info_t*>(id);
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if (ii->mem_ == nullptr || ii->size_ == 0) {
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return 0;
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}
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return acc_of(ii->mem_, calc_size(ii->size_)).load(std::memory_order_acquire);
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}
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void sub_ref(id_t id) {
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if (id == nullptr) {
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ipc::error("fail sub_ref: invalid id (null)\n");
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return;
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}
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auto ii = static_cast<id_info_t*>(id);
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if (ii->mem_ == nullptr || ii->size_ == 0) {
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ipc::error("fail sub_ref: invalid id (mem = %p, size = %zd)\n", ii->mem_, ii->size_);
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return;
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}
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acc_of(ii->mem_, calc_size(ii->size_)).fetch_sub(1, std::memory_order_acq_rel);
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}
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void * get_mem(id_t id, std::size_t * size) {
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if (id == nullptr) {
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ipc::error("fail get_mem: invalid id (null)\n");
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return nullptr;
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}
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auto ii = static_cast<id_info_t*>(id);
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if (ii->mem_ != nullptr) {
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if (size != nullptr) *size = ii->size_;
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return ii->mem_;
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}
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if (ii->h_ == NULL) {
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ipc::error("fail to_mem: invalid id (h = null)\n");
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return nullptr;
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}
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LPVOID mem = ::MapViewOfFile(ii->h_, FILE_MAP_ALL_ACCESS, 0, 0, 0);
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if (mem == NULL) {
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ipc::error("fail MapViewOfFile[%d]\n", static_cast<int>(::GetLastError()));
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return nullptr;
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}
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MEMORY_BASIC_INFORMATION mem_info;
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if (::VirtualQuery(mem, &mem_info, sizeof(mem_info)) == 0) {
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ipc::error("fail VirtualQuery[%d]\n", static_cast<int>(::GetLastError()));
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return nullptr;
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}
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std::size_t actual_size = static_cast<std::size_t>(mem_info.RegionSize);
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if (ii->size_ == 0) {
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// Opening existing shared memory
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ii->size_ = actual_size - sizeof(info_t);
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}
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else {
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// Should match the size we allocated in acquire
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ii->size_ = ii->size_; // Keep user-requested size
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}
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ii->mem_ = mem;
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if (size != nullptr) *size = ii->size_;
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// Initialize or increment reference counter
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acc_of(mem, calc_size(ii->size_)).fetch_add(1, std::memory_order_release);
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return static_cast<void *>(mem);
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}
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std::int32_t release(id_t id) noexcept {
150+
if (id == nullptr) {
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ipc::error("fail release: invalid id (null)\n");
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return -1;
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}
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std::int32_t ret = -1;
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auto ii = static_cast<id_info_t*>(id);
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if (ii->mem_ == nullptr || ii->size_ == 0) {
157+
ipc::error("fail release: invalid id (mem = %p, size = %zd)\n", ii->mem_, ii->size_);
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}
159+
else {
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ret = acc_of(ii->mem_, calc_size(ii->size_)).fetch_sub(1, std::memory_order_acq_rel);
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::UnmapViewOfFile(static_cast<LPCVOID>(ii->mem_));
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}
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if (ii->h_ == NULL) {
164+
ipc::error("fail release: invalid id (h = null)\n");
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}
166+
else ::CloseHandle(ii->h_);
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mem::free(ii);
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return ret;
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}
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void remove(id_t id) noexcept {
172+
if (id == nullptr) {
173+
ipc::error("fail release: invalid id (null)\n");
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return;
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}
176+
release(id);
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}
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void remove(char const * name) noexcept {
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if (!is_valid_string(name)) {
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ipc::error("fail remove: name is empty\n");
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return;
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}
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// Do Nothing.
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}
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} // namespace shm
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} // namespace ipc

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