Method do_write_cache

phx_percona/percona/sql/binlog.cc:5801–6038

*/

int MYSQL_BIN_LOG::do_write_cache(THD *thd, IO_CACHE *cache)
{
  DBUG_ENTER("MYSQL_BIN_LOG::do_write_cache(IO_CACHE *)");

  DBUG_EXECUTE_IF("simulate_do_write_cache_failure",
                  {
                    /* 
                       see binlog_cache_data::write_event() that reacts on
                       @c simulate_disk_full_at_flush_pending.
                    */
                    DBUG_SET("-d,simulate_do_write_cache_failure");
                    DBUG_RETURN(ER_ERROR_ON_WRITE);
                  });

  if (reinit_io_cache(cache, READ_CACHE, 0, 0, 0))
    DBUG_RETURN(ER_ERROR_ON_WRITE);
  uint length= my_b_bytes_in_cache(cache), group, carry, hdr_offs;
  ulong remains= 0; // part of unprocessed yet netto length of the event
  long val;
  ulong end_log_pos_inc= 0; // each event processed adds BINLOG_CHECKSUM_LEN 2 t
  uchar header[LOG_EVENT_HEADER_LEN];
  ha_checksum crc= 0, crc_0= 0; // assignments to keep compiler happy
  my_bool do_checksum= (binlog_checksum_options != BINLOG_CHECKSUM_ALG_OFF);
  uchar buf[BINLOG_CHECKSUM_LEN];

  // while there is just one alg the following must hold:
  DBUG_ASSERT(!do_checksum ||
              binlog_checksum_options == BINLOG_CHECKSUM_ALG_CRC32);

  /*
    The events in the buffer have incorrect end_log_pos data
    (relative to beginning of group rather than absolute),
    so we'll recalculate them in situ so the binlog is always
    correct, even in the middle of a group. This is possible
    because we now know the start position of the group (the
    offset of this cache in the log, if you will); all we need
    to do is to find all event-headers, and add the position of
    the group to the end_log_pos of each event.  This is pretty
    straight forward, except that we read the cache in segments,
    so an event-header might end up on the cache-border and get
    split.
  */

  group= (uint)my_b_tell(&log_file);
  DBUG_PRINT("debug", ("length: %llu, group: %llu",
                       (ulonglong) length, (ulonglong) group));
  hdr_offs= carry= 0;
  if (do_checksum)
    crc= crc_0= my_checksum(0L, NULL, 0);

  if (DBUG_EVALUATE_IF("fault_injection_crc_value", 1, 0))
    crc= crc - 1;

  do
  {
    /*
      if we only got a partial header in the last iteration,
      get the other half now and process a full header.