esphome_syslog.cpp

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#include "esphome_syslog.h"
 
#include "esphome/components/logger/logger.h"
#include "esphome/core/application.h"
#include "esphome/core/time.h"
 
namespace esphome::syslog {
 
// Map log levels to syslog severity using an array, indexed by ESPHome log level (1-7)
constexpr int LOG_LEVEL_TO_SYSLOG_SEVERITY[] = {
    3,  // NONE
    3,  // ERROR
    4,  // WARN
    5,  // INFO
    6,  // CONFIG
    7,  // DEBUG
    7,  // VERBOSE
    7   // VERY_VERBOSE
};
 
void Syslog::setup() {
  logger::global_logger->add_log_callback(
      this, [](void *self, uint8_t level, const char *tag, const char *message, size_t message_len) {
        static_cast<Syslog *>(self)->on_log(level, tag, message, message_len);
      });
}
 
void Syslog::on_log(uint8_t level, const char *tag, const char *message, size_t message_len) {
  this->log_(level, tag, message, message_len);
}
 
void Syslog::log_(const int level, const char *tag, const char *message, size_t message_len) const {
  if (level > this->log_level_)
    return;
  // Syslog PRI calculation: facility * 8 + severity
  int severity = 7;
  if ((unsigned) level <= 7) {
    severity = LOG_LEVEL_TO_SYSLOG_SEVERITY[level];
  }
  int pri = this->facility_ * 8 + severity;
 
  size_t len = message_len;
  // remove color formatting
  if (this->strip_ && message[0] == 0x1B && len > 11) {
    message += 7;
    len -= 11;
  }
 
  // Build syslog packet on stack (508 bytes chosen as practical limit for syslog over UDP)
  char packet[508];
  size_t offset = 0;
  size_t remaining = sizeof(packet);
 
  // Write PRI - abort if this fails as packet would be malformed
  offset = buf_append_printf(packet, sizeof(packet), 0, "<%d>", pri);
  if (offset == 0) {
    return;  // PRI always produces at least "<0>" (3 chars), so 0 means error
  }
  remaining -= offset;
 
  // Write timestamp directly into packet (RFC 5424: use "-" if time not valid or strftime fails)
  auto now = this->time_->now();
  size_t ts_written = now.is_valid() ? now.strftime(packet + offset, remaining, "%b %e %H:%M:%S") : 0;
  if (ts_written > 0) {
    offset += ts_written;
  } else if (remaining > 0) {
    packet[offset++] = '-';
  }
 
  // Write hostname, tag, and message
  offset = buf_append_printf(packet, sizeof(packet), offset, " %s %s: %.*s", App.get_name().c_str(), tag, (int) len,
                             message);
  // Clamp to exclude null terminator position if buffer was filled
  if (offset >= sizeof(packet)) {
    offset = sizeof(packet) - 1;
  }
 
  if (offset > 0) {
    this->parent_->send_packet(reinterpret_cast<const uint8_t *>(packet), offset);
  }
}
 
}  // namespace esphome::syslog