123 lines
3.4 KiB
C++
123 lines
3.4 KiB
C++
/***
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Oak - Non-Linear Video Editor
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Copyright (C) 2026 Oak Team
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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***/
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#ifndef IPC_SHAREDMEMORYREGION_H
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#define IPC_SHAREDMEMORYREGION_H
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#include <cstddef>
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#include <QString>
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namespace olive
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{
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namespace ipc
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{
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/**
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* @brief A named, fixed-size shared memory segment mapped into the process address space.
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*
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* One process Create()s the segment (owner); the peer process Attach()es to it by the same key.
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* The mapping is a raw contiguous byte range accessible via data() — the IPC ring buffers and frame
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* slot pools are laid out inside it. Nothing here is locked; synchronization is entirely the
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* caller's responsibility via the lock-free structures placed in the mapping.
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*
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* We deliberately use the raw OS primitives (POSIX shm_open + mmap, Windows CreateFileMapping +
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* MapViewOfFile) rather than QSharedMemory: QSharedMemory carries an implicit semaphore and a 1-byte
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* header convention, attaches/detaches with reference counting we don't want, and historically has
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* cross-platform lifetime quirks. For a render pipeline pushing large frames we want a plain mmap.
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*/
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class SharedMemoryRegion {
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public:
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enum Mode {
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/// Create (and own) the segment. Fails if it already exists; unlinks on destruction.
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kCreate,
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/// Attach to a segment created by the peer. Does not unlink on destruction.
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kAttach
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};
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SharedMemoryRegion();
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~SharedMemoryRegion();
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SharedMemoryRegion(const SharedMemoryRegion &) = delete;
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SharedMemoryRegion &operator=(const SharedMemoryRegion &) = delete;
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/**
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* @brief Open the segment identified by `key` with the given `size` in bytes.
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*
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* `key` is a short identifier (no leading slash needed; the platform prefix is added internally).
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* Returns true on success. On failure, error() carries a human-readable reason.
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*/
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bool Open(const QString &key, size_t size, Mode mode);
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/**
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* @brief Unmap and (if owner) unlink the segment. Called automatically by the destructor.
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*/
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void Close();
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bool IsValid() const
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{
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return data_ != nullptr;
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}
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void *data() const
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{
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return data_;
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}
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size_t size() const
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{
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return size_;
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}
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const QString &key() const
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{
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return key_;
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}
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const QString &error() const
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{
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return error_;
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}
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/**
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* @brief Build a unique segment key for a worker, e.g. "olive-rw-<pid>-<index>".
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*
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* Centralized so the owner and the spawned worker agree on the same name.
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*/
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static QString MakeKey(qint64 owner_pid, int worker_index);
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private:
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QString key_;
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size_t size_;
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void *data_;
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Mode mode_;
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QString error_;
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#if defined(Q_OS_WIN)
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void *handle_; // HANDLE from CreateFileMapping/OpenFileMapping
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#else
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int fd_; // file descriptor from shm_open
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QString shm_name_; // the platform-prefixed name actually passed to shm_open
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#endif
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};
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} // namespace ipc
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} // namespace olive
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#endif // IPC_SHAREDMEMORYREGION_H
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