initial commit

include/adc_sweep/shm_stack.hpp

@@ -0,0 +1,82 @@
+#pragma once
+
+#include <atomic>
+#include <cstddef>
+#include <cstdint>
+#include <optional>
+#include <string>
+#include <vector>
+
+#include "adc_sweep/sweep_core.hpp"
+
+namespace adc_sweep {
+
+constexpr uint32_t kShmMagic = 0x53575041;  // "AWPS"
+constexpr uint32_t kShmVersion = 1;
+
+struct alignas(64) ShmHeader {
+    uint32_t magic;
+    uint32_t version;
+    uint32_t capacity;
+    uint32_t sweep_width;
+    uint32_t slot_stride;
+    uint32_t reserved0;
+    uint64_t producer_seq;
+    std::atomic<uint64_t> write_seq;
+    std::atomic<uint32_t> latest_slot;
+    uint32_t reserved1;
+    uint8_t reserved2[64 - 48];
+};
+static_assert(sizeof(ShmHeader) == 64, "ShmHeader must stay fixed size");
+
+struct SweepSlotHeader {
+    std::atomic<uint64_t> seq;
+    uint64_t ts_mono_ns;
+    uint32_t sweep_idx;
+    int32_t ch_primary;
+    uint32_t ch_mask;
+    uint32_t reserved;
+    float n_valid;
+    float min;
+    float max;
+    float mean;
+    float std;
+    float dt_ms;
+};
+
+class ShmSweepStackWriter {
+public:
+    ShmSweepStackWriter(std::string shm_name, uint32_t capacity, uint32_t sweep_width);
+    ~ShmSweepStackWriter();
+
+    bool open_or_create(std::string& err);
+    void close();
+    bool publish(const SweepResult& result, std::string& err);
+
+    uint32_t capacity() const { return capacity_; }
+    uint32_t sweep_width() const { return sweep_width_; }
+
+private:
+    SweepSlotHeader* slot_header(uint32_t slot_idx);
+    float* slot_sweep_data(uint32_t slot_idx);
+
+    std::string shm_name_;
+    uint32_t capacity_;
+    uint32_t sweep_width_;
+    uint32_t slot_stride_;
+    int shm_fd_ = -1;
+    void* mapped_ = nullptr;
+    size_t mapped_size_ = 0;
+    ShmHeader* header_ = nullptr;
+    uint64_t next_seq_ = 1;
+};
+
+struct LatestSnapshot {
+    uint64_t seq = 0;
+    SweepMeta meta;
+    std::vector<float> sweep;
+};
+
+std::optional<LatestSnapshot> read_latest_snapshot(void* mapped, uint32_t capacity, uint32_t sweep_width, uint32_t slot_stride);
+
+}  // namespace adc_sweep