task_log_buffer_host.cpp

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#ifdef USE_HOST
 
#include "task_log_buffer_host.h"
 
#ifdef USE_ESPHOME_TASK_LOG_BUFFER
 
#include "esphome/core/log.h"
#include <algorithm>
#include <cstdio>
 
namespace esphome::logger {
 
int TaskLogBuffer::acquire_write_slot_() {
  // Try to reserve a slot using compare-and-swap
  size_t current_reserve = this->reserve_index_.load(std::memory_order_relaxed);
 
  while (true) {
    // Calculate next index (with wrap-around)
    size_t next_reserve = (current_reserve + 1) % ESPHOME_TASK_LOG_BUFFER_SIZE;
 
    // Check if buffer would be full
    // Buffer is full when next write position equals read position
    size_t current_read = this->read_index_.load(std::memory_order_acquire);
    if (next_reserve == current_read) {
      return -1;  // Buffer full
    }
 
    // Try to claim this slot
    if (this->reserve_index_.compare_exchange_weak(current_reserve, next_reserve, std::memory_order_acq_rel,
                                                   std::memory_order_relaxed)) {
      return static_cast<int>(current_reserve);
    }
    // If CAS failed, current_reserve was updated, retry with new value
  }
}
 
void TaskLogBuffer::commit_write_slot_(int slot_index) {
  // Mark the slot as ready for reading
  this->slots_[slot_index].ready.store(true, std::memory_order_release);
 
  // Try to advance the write_index if we're the next expected commit
  // This ensures messages are read in order
  size_t expected = slot_index;
  size_t next = (slot_index + 1) % ESPHOME_TASK_LOG_BUFFER_SIZE;
 
  // We only advance write_index if this slot is the next one expected
  // This handles out-of-order commits correctly
  while (true) {
    if (!this->write_index_.compare_exchange_weak(expected, next, std::memory_order_release,
                                                  std::memory_order_relaxed)) {
      // Someone else advanced it or we're not next in line, that's fine
      break;
    }
 
    // Successfully advanced, check if next slot is also ready
    expected = next;
    next = (next + 1) % ESPHOME_TASK_LOG_BUFFER_SIZE;
    if (!this->slots_[expected].ready.load(std::memory_order_acquire)) {
      break;
    }
  }
}
 
bool TaskLogBuffer::send_message_thread_safe(uint8_t level, const char *tag, uint16_t line, const char *thread_name,
                                             const char *format, va_list args) {
  // Acquire a slot
  int slot_index = this->acquire_write_slot_();
  if (slot_index < 0) {
    return false;  // Buffer full
  }
 
  LogMessage &msg = this->slots_[slot_index];
 
  // Fill in the message header
  msg.level = level;
  msg.tag = tag;
  msg.line = line;
 
  // Store the thread name now to avoid crashes if thread exits before processing
  if (thread_name != nullptr) {
    strncpy(msg.thread_name, thread_name, sizeof(msg.thread_name) - 1);
    msg.thread_name[sizeof(msg.thread_name) - 1] = '\0';
  } else {
    msg.thread_name[0] = '\0';
  }
 
  // Format the message text
  int ret = vsnprintf(msg.text, sizeof(msg.text), format, args);
  if (ret < 0) {
    // Formatting error - still commit the slot but with empty text
    msg.text[0] = '\0';
    msg.text_length = 0;
  } else {
    msg.text_length = static_cast<uint16_t>(std::min(static_cast<size_t>(ret), sizeof(msg.text) - 1));
  }
 
  // Remove trailing newlines
  while (msg.text_length > 0 && msg.text[msg.text_length - 1] == '\n') {
    msg.text_length--;
  }
  msg.text[msg.text_length] = '\0';
 
  // Commit the slot
  this->commit_write_slot_(slot_index);
 
  return true;
}
 
bool TaskLogBuffer::borrow_message_main_loop(LogMessage *&message, uint16_t &text_length) {
  size_t current_read = this->read_index_.load(std::memory_order_relaxed);
  size_t current_write = this->write_index_.load(std::memory_order_acquire);
 
  // Check if buffer is empty
  if (current_read == current_write) {
    return false;
  }
 
  // Check if the slot is ready (should always be true if write_index advanced)
  LogMessage &msg = this->slots_[current_read];
  if (!msg.ready.load(std::memory_order_acquire)) {
    return false;
  }
 
  message = &msg;
  text_length = msg.text_length;
  return true;
}
 
void TaskLogBuffer::release_message_main_loop() {
  size_t current_read = this->read_index_.load(std::memory_order_relaxed);
 
  // Clear the ready flag
  this->slots_[current_read].ready.store(false, std::memory_order_release);
 
  // Advance read index
  size_t next_read = (current_read + 1) % ESPHOME_TASK_LOG_BUFFER_SIZE;
  this->read_index_.store(next_read, std::memory_order_release);
}
 
}  // namespace esphome::logger
 
#endif  // USE_ESPHOME_TASK_LOG_BUFFER
#endif  // USE_HOST