api_overflow_buffer.h

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#pragma once
#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <sys/types.h>
 
#include "esphome/core/defines.h"
#ifdef USE_API
 
#include "esphome/components/socket/headers.h"
#include "esphome/components/socket/socket.h"
#include "api_buffer.h"
 
namespace esphome::api {
 
class APIOverflowBuffer {
 public:
  bool empty() const { return this->count_ == 0; }
 
  ssize_t try_drain(socket::Socket *socket);
 
  bool enqueue_iov(const struct iovec *iov, int iovcnt, size_t total_len, size_t skip);
 
  void release() {
    if (this->count_ == 0) {
      this->buf_.release();
    } else {
      this->release_when_drained_ = true;
    }
  }
 
 protected:
  static constexpr size_t LEN_PREFIX = 2;
  static constexpr size_t BYTES_PER_SLOT = 2048;
  // Reserve in 256 byte steps so a creeping high-water mark settles quickly
  static constexpr size_t GROW_QUANTUM = 256;
  // Lone message ceiling, rounded down so reserve_for() never exceeds the buffer limit
  static constexpr size_t MAX_LONE_BYTES = APIBuffer::MAX_SIZE & ~(GROW_QUANTUM - 1);
  static constexpr size_t MAX_BYTES = std::min(API_MAX_SEND_QUEUE * BYTES_PER_SLOT, MAX_LONE_BYTES);
  static constexpr size_t reserve_for(size_t want) { return (want + GROW_QUANTUM - 1) & ~(GROW_QUANTUM - 1); }
 
  APIBuffer buf_;
  uint16_t head_{0};  // offset of the front message's length prefix; bytes before it are sent
  uint8_t count_{0};
  // socket->write() can re-enter the send path (log from an lwip callback):
  // a nested drain makes no progress and a nested enqueue never moves storage
  bool draining_ : 1 {false};
  bool release_when_drained_ : 1 {false};
};
 
}  // namespace esphome::api
 
#endif  // USE_API