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ardupilot/libraries/DataFlash/DataFlash_File.cpp

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/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
/*
DataFlash logging - file oriented variant
This uses posix file IO to create log files called logs/NN.bin in the
given directory
SD Card Rates on PixHawk:
- deletion rate seems to be ~50 files/second.
- stat seems to be ~150/second
- readdir loop of 511 entry directory ~62,000 microseconds
*/
#include <AP_HAL/AP_HAL.h>
#if HAL_OS_POSIX_IO
#include "DataFlash_File.h"
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <assert.h>
#include <AP_Math/AP_Math.h>
#include <stdio.h>
#include <time.h>
#include <dirent.h>
#include <AP_HAL/utility/RingBuffer.h>
#ifdef __APPLE__
#include <sys/param.h>
#include <sys/mount.h>
#else
#include <sys/statfs.h>
#endif
extern const AP_HAL::HAL& hal;
#define MAX_LOG_FILES 500U
#define DATAFLASH_PAGE_SIZE 1024UL
/*
constructor
*/
DataFlash_File::DataFlash_File(DataFlash_Class &front, const char *log_directory) :
DataFlash_Backend(front),
_write_fd(-1),
_read_fd(-1),
_read_fd_log_num(0),
_read_offset(0),
_write_offset(0),
_initialised(false),
_open_error(false),
_log_directory(log_directory),
_writebuf(NULL),
_writebuf_size(16*1024),
#if defined(CONFIG_ARCH_BOARD_PX4FMU_V1)
// V1 gets IO errors with larger than 512 byte writes
_writebuf_chunk(512),
#elif defined(CONFIG_ARCH_BOARD_VRBRAIN_V45)
_writebuf_chunk(512),
#elif defined(CONFIG_ARCH_BOARD_VRBRAIN_V51)
_writebuf_chunk(512),
#elif defined(CONFIG_ARCH_BOARD_VRBRAIN_V52)
_writebuf_chunk(512),
#elif defined(CONFIG_ARCH_BOARD_VRUBRAIN_V51)
_writebuf_chunk(512),
#elif defined(CONFIG_ARCH_BOARD_VRUBRAIN_V52)
_writebuf_chunk(512),
#elif defined(CONFIG_ARCH_BOARD_VRHERO_V10)
_writebuf_chunk(512),
#else
_writebuf_chunk(4096),
#endif
_writebuf_head(0),
_writebuf_tail(0),
_last_write_time(0),
_perf_write(hal.util->perf_alloc(AP_HAL::Util::PC_ELAPSED, "DF_write")),
_perf_fsync(hal.util->perf_alloc(AP_HAL::Util::PC_ELAPSED, "DF_fsync")),
_perf_errors(hal.util->perf_alloc(AP_HAL::Util::PC_COUNT, "DF_errors")),
_perf_overruns(hal.util->perf_alloc(AP_HAL::Util::PC_COUNT, "DF_overruns"))
{}
// initialisation
void DataFlash_File::Init(const struct LogStructure *structure, uint8_t num_types)
{
DataFlash_Backend::Init(structure, num_types);
// create the log directory if need be
int ret;
struct stat st;
#if CONFIG_HAL_BOARD == HAL_BOARD_PX4 || CONFIG_HAL_BOARD == HAL_BOARD_VRBRAIN
// try to cope with an existing lowercase log directory
// name. NuttX does not handle case insensitive VFAT well
DIR *d = opendir("/fs/microsd/APM");
if (d != NULL) {
for (struct dirent *de=readdir(d); de; de=readdir(d)) {
if (strcmp(de->d_name, "logs") == 0) {
rename("/fs/microsd/APM/logs", "/fs/microsd/APM/OLDLOGS");
break;
}
}
closedir(d);
}
#endif
const char* custom_dir = hal.util->get_custom_log_directory();
if (custom_dir != NULL){
_log_directory = custom_dir;
}
ret = stat(_log_directory, &st);
if (ret == -1) {
ret = mkdir(_log_directory, 0777);
}
if (ret == -1) {
hal.console->printf("Failed to create log directory %s\n", _log_directory);
return;
}
if (_writebuf != NULL) {
free(_writebuf);
_writebuf = NULL;
}
/*
if we can't allocate the full writebuf then try reducing it
until we can allocate it
*/
while (_writebuf == NULL && _writebuf_size >= _writebuf_chunk) {
_writebuf = (uint8_t *)malloc(_writebuf_size);
if (_writebuf == NULL) {
_writebuf_size /= 2;
}
}
if (_writebuf == NULL) {
hal.console->printf("Out of memory for logging\n");
return;
}
_writebuf_head = _writebuf_tail = 0;
_initialised = true;
hal.scheduler->register_io_process(FUNCTOR_BIND_MEMBER(&DataFlash_File::_io_timer, void));
}
bool DataFlash_File::file_exists(const char *filename) const
{
struct stat st;
if (stat(filename, &st) == -1) {
// hopefully errno==ENOENT. If some error occurs it is
// probably better to assume this file exists.
return false;
}
return true;
}
bool DataFlash_File::log_exists(const uint16_t lognum) const
{
char *filename = _log_file_name(lognum);
if (filename == NULL) {
// internal_error();
return false; // ?!
}
bool ret = file_exists(filename);
free(filename);
return ret;
}
void DataFlash_File::periodic_fullrate(const uint32_t now)
{
DataFlash_Backend::push_log_blocks();
}
uint16_t DataFlash_File::bufferspace_available()
{
uint16_t _head;
return (BUF_SPACE(_writebuf)) - critical_message_reserved_space();
}
// return true for CardInserted() if we successfully initialised
bool DataFlash_File::CardInserted(void)
{
return _initialised && !_open_error;
}
// returns the amount of disk space available in _log_directory (in bytes)
// returns -1 on error
int64_t DataFlash_File::disk_space_avail()
{
struct statfs stats;
if (statfs(_log_directory, &stats) < 0) {
return -1;
}
return (((int64_t)stats.f_bavail) * stats.f_bsize);
}
// returns the total amount of disk space (in use + available) in
// _log_directory (in bytes).
// returns -1 on error
int64_t DataFlash_File::disk_space()
{
struct statfs stats;
if (statfs(_log_directory, &stats) < 0) {
return -1;
}
return (((int64_t)stats.f_blocks) * stats.f_bsize);
}
// returns the available space in _log_directory as a percentage
// returns -1.0f on error
float DataFlash_File::avail_space_percent()
{
int64_t avail = disk_space_avail();
if (avail == -1) {
return -1.0f;
}
int64_t space = disk_space();
if (space == -1) {
return -1.0f;
}
return (avail/(float)space) * 100;
}
// find_oldest_log - find oldest log in _log_directory
// returns 0 if no log was found
uint16_t DataFlash_File::find_oldest_log()
{
uint16_t last_log_num = find_last_log();
if (last_log_num == 0) {
return 0;
}
uint16_t current_oldest_log = 0; // 0 is invalid
// We could count up to find_last_log(), but if people start
// relying on the min_avail_space_percent feature we could end up
// doing a *lot* of asprintf()s and stat()s
DIR *d = opendir(_log_directory);
if (d == NULL) {
// internal_error();
return 0;
}
// we only remove files which look like xxx.BIN
for (struct dirent *de=readdir(d); de; de=readdir(d)) {
uint8_t length = strlen(de->d_name);
if (length < 5) {
// not long enough for \d+[.]BIN
continue;
}
if (strncmp(&de->d_name[length-4], ".BIN", 4)) {
// doesn't end in .BIN
continue;
}
uint16_t thisnum = strtoul(de->d_name, NULL, 10);
if (thisnum > MAX_LOG_FILES) {
// ignore files above our official maximum...
continue;
}
if (current_oldest_log == 0) {
current_oldest_log = thisnum;
} else {
if (current_oldest_log <= last_log_num) {
if (thisnum > last_log_num) {
current_oldest_log = thisnum;
} else if (thisnum < current_oldest_log) {
current_oldest_log = thisnum;
}
} else { // current_oldest_log > last_log_num
if (thisnum > last_log_num) {
if (thisnum < current_oldest_log) {
current_oldest_log = thisnum;
}
}
}
}
}
closedir(d);
return current_oldest_log;
}
void DataFlash_File::Prep_MinSpace()
{
const uint16_t first_log_to_remove = find_oldest_log();
if (first_log_to_remove == 0) {
// no files to remove
return;
}
uint16_t log_to_remove = first_log_to_remove;
uint16_t count = 0;
do {
float avail = avail_space_percent();
if (is_equal(avail, -1.0f)) {
// internal_error()
break;
}
if (avail >= min_avail_space_percent) {
break;
}
if (count++ > MAX_LOG_FILES+10) {
// *way* too many deletions going on here. Possible internal error.
// internal_error();
break;
}
char *filename_to_remove = _log_file_name(log_to_remove);
if (filename_to_remove == NULL) {
// internal_error();
break;
}
if (file_exists(filename_to_remove)) {
hal.console->printf("Removing (%s) for minimum-space requirements (%.2f%% < %.0f%%)\n",
filename_to_remove, avail, min_avail_space_percent);
if (unlink(filename_to_remove) == -1) {
hal.console->printf("Failed to remove %s: %s\n", filename_to_remove, strerror(errno));
free(filename_to_remove);
if (errno == ENOENT) {
// corruption - should always have a continuous
// sequence of files... however, there may be still
// files out there, so keep going.
} else {
// internal_error();
break;
}
} else {
free(filename_to_remove);
}
}
log_to_remove++;
if (log_to_remove > MAX_LOG_FILES) {
log_to_remove = 1;
}
} while (log_to_remove != first_log_to_remove);
}
void DataFlash_File::Prep() {
if (hal.util->get_soft_armed()) {
// do not want to do any filesystem operations while we are e.g. flying
return;
}
Prep_MinSpace();
}
bool DataFlash_File::NeedPrep()
{
if (!CardInserted()) {
// should not have been called?!
return false;
}
if (avail_space_percent() < min_avail_space_percent) {
return true;
}
return false;
}
/*
construct a log file name given a log number.
Note: Caller must free.
*/
char *DataFlash_File::_log_file_name(const uint16_t log_num) const
{
char *buf = NULL;
if (asprintf(&buf, "%s/%u.BIN", _log_directory, (unsigned)log_num) == 0) {
return NULL;
}
return buf;
}
/*
return path name of the lastlog.txt marker file
Note: Caller must free.
*/
char *DataFlash_File::_lastlog_file_name(void) const
{
char *buf = NULL;
if (asprintf(&buf, "%s/LASTLOG.TXT", _log_directory) == 0) {
return NULL;
}
return buf;
}
// remove all log files
void DataFlash_File::EraseAll()
{
uint16_t log_num;
stop_logging();
for (log_num=1; log_num<=MAX_LOG_FILES; log_num++) {
char *fname = _log_file_name(log_num);
if (fname == NULL) {
break;
}
unlink(fname);
free(fname);
}
char *fname = _lastlog_file_name();
if (fname != NULL) {
unlink(fname);
free(fname);
}
}
/* Write a block of data at current offset */
bool DataFlash_File::WritePrioritisedBlock(const void *pBuffer, uint16_t size, bool is_critical)
{
if (_write_fd == -1 || !_initialised || _open_error || !_writes_enabled) {
return false;
}
if (! WriteBlockCheckStartupMessages()) {
_dropped++;
return false;
}
uint16_t _head;
uint16_t space = BUF_SPACE(_writebuf);
if (_writing_startup_messages &&
_front._startup_messagewriter.fmt_done()) {
// the state machine has called us, and it has finished
// writing format messages out. It can always get back to us
// with more messages later, so let's leave room for other
// things:
if (space < non_messagewriter_message_reserved_space()) {
// this message isn't dropped, it will be sent again...
return false;
}
} else {
// we reserve some amount of space for critical messages:
if (!is_critical && space < critical_message_reserved_space()) {
_dropped++;
return false;
}
}
// if no room for entire message - drop it:
if (space < size) {
hal.util->perf_count(_perf_overruns);
_dropped++;
return false;
}
if (_writebuf_tail < _head) {
// perform as single memcpy
assert(_writebuf_tail+size <= _writebuf_size);
memcpy(&_writebuf[_writebuf_tail], pBuffer, size);
BUF_ADVANCETAIL(_writebuf, size);
} else {
// perform as two memcpy calls
uint16_t n = _writebuf_size - _writebuf_tail;
if (n > size) n = size;
assert(_writebuf_tail+n <= _writebuf_size);
memcpy(&_writebuf[_writebuf_tail], pBuffer, n);
BUF_ADVANCETAIL(_writebuf, n);
pBuffer = (const void *)(((const uint8_t *)pBuffer) + n);
n = size - n;
if (n > 0) {
assert(_writebuf_tail+n <= _writebuf_size);
memcpy(&_writebuf[_writebuf_tail], pBuffer, n);
BUF_ADVANCETAIL(_writebuf, n);
}
}
return true;
}
/*
read a packet. The header bytes have already been read.
*/
bool DataFlash_File::ReadBlock(void *pkt, uint16_t size)
{
if (_read_fd == -1 || !_initialised || _open_error) {
return false;
}
memset(pkt, 0, size);
if (::read(_read_fd, pkt, size) != size) {
return false;
}
_read_offset += size;
return true;
}
/*
find the highest log number
*/
uint16_t DataFlash_File::find_last_log()
{
unsigned ret = 0;
char *fname = _lastlog_file_name();
if (fname == NULL) {
return ret;
}
FILE *f = ::fopen(fname, "r");
free(fname);
if (f != NULL) {
char buf[10];
memset(buf, 0, sizeof(buf));
// PX4 doesn't have fscanf()
if (fread(buf, 1, sizeof(buf)-1, f) > 0) {
sscanf(buf, "%u", &ret);
}
fclose(f);
}
return ret;
}
uint32_t DataFlash_File::_get_log_size(const uint16_t log_num) const
{
char *fname = _log_file_name(log_num);
if (fname == NULL) {
return 0;
}
struct stat st;
if (::stat(fname, &st) != 0) {
free(fname);
return 0;
}
free(fname);
return st.st_size;
}
uint32_t DataFlash_File::_get_log_time(const uint16_t log_num) const
{
char *fname = _log_file_name(log_num);
if (fname == NULL) {
return 0;
}
struct stat st;
if (::stat(fname, &st) != 0) {
free(fname);
return 0;
}
free(fname);
return st.st_mtime;
}
/*
convert a list entry number back into a log number (which can then
be converted into a filename). A "list entry number" is a sequence
where the oldest log has a number of 1, the second-from-oldest 2,
and so on. Thus the highest list entry number is equal to the
number of logs.
*/
uint16_t DataFlash_File::_log_num_from_list_entry(const uint16_t list_entry)
{
uint16_t oldest_log = find_oldest_log();
if (oldest_log == 0) {
// We don't have any logs...
return 0;
}
uint32_t log_num = oldest_log + list_entry - 1;
if (log_num > MAX_LOG_FILES) {
log_num -= MAX_LOG_FILES;
}
return (uint16_t)log_num;
}
/*
find the number of pages in a log
*/
void DataFlash_File::get_log_boundaries(const uint16_t list_entry, uint16_t & start_page, uint16_t & end_page)
{
const uint16_t log_num = _log_num_from_list_entry(list_entry);
if (log_num == 0) {
// that failed - probably no logs
start_page = 0;
end_page = 0;
return;
}
start_page = 0;
end_page = _get_log_size(log_num) / DATAFLASH_PAGE_SIZE;
}
/*
find the number of pages in a log
*/
int16_t DataFlash_File::get_log_data(const uint16_t list_entry, const uint16_t page, const uint32_t offset, const uint16_t len, uint8_t *data)
{
if (!_initialised || _open_error) {
return -1;
}
const uint16_t log_num = _log_num_from_list_entry(list_entry);
if (log_num == 0) {
// that failed - probably no logs
return -1;
}
if (_read_fd != -1 && log_num != _read_fd_log_num) {
::close(_read_fd);
_read_fd = -1;
}
if (_read_fd == -1) {
char *fname = _log_file_name(log_num);
if (fname == NULL) {
return -1;
}
stop_logging();
_read_fd = ::open(fname, O_RDONLY);
if (_read_fd == -1) {
_open_error = true;
int saved_errno = errno;
::printf("Log read open fail for %s - %s\n",
fname, strerror(saved_errno));
hal.console->printf("Log read open fail for %s - %s\n",
fname, strerror(saved_errno));
free(fname);
return -1;
}
free(fname);
_read_offset = 0;
_read_fd_log_num = log_num;
}
uint32_t ofs = page * (uint32_t)DATAFLASH_PAGE_SIZE + offset;
/*
this rather strange bit of code is here to work around a bug
in file offsets in NuttX. Every few hundred blocks of reads
(starting at around 350k into a file) NuttX will get the
wrong offset for sequential reads. The offset it gets is
typically 128k earlier than it should be. It turns out that
calling lseek() with 0 offset and SEEK_CUR works around the
bug. We can remove this once we find the real bug.
*/
if (ofs / 4096 != (ofs+len) / 4096) {
off_t seek_current = ::lseek(_read_fd, 0, SEEK_CUR);
if (seek_current != (off_t)_read_offset) {
::lseek(_read_fd, _read_offset, SEEK_SET);
}
}
if (ofs != _read_offset) {
::lseek(_read_fd, ofs, SEEK_SET);
_read_offset = ofs;
}
int16_t ret = (int16_t)::read(_read_fd, data, len);
if (ret > 0) {
_read_offset += ret;
}
return ret;
}
/*
find size and date of a log
*/
void DataFlash_File::get_log_info(const uint16_t list_entry, uint32_t &size, uint32_t &time_utc)
{
uint16_t log_num = _log_num_from_list_entry(list_entry);
if (log_num == 0) {
// that failed - probably no logs
size = 0;
time_utc = 0;
return;
}
size = _get_log_size(log_num);
time_utc = _get_log_time(log_num);
}
/*
get the number of logs - note that the log numbers must be consecutive
*/
uint16_t DataFlash_File::get_num_logs()
{
uint16_t ret = 0;
uint16_t high = find_last_log();
uint16_t i;
for (i=high; i>0; i--) {
if (! log_exists(i)) {
break;
}
ret++;
}
if (i == 0) {
for (i=MAX_LOG_FILES; i>high; i--) {
if (! log_exists(i)) {
break;
}
ret++;
}
}
return ret;
}
/*
stop logging
*/
void DataFlash_File::stop_logging(void)
{
if (_write_fd != -1) {
int fd = _write_fd;
_write_fd = -1;
log_write_started = false;
::close(fd);
}
}
/*
start writing to a new log file
*/
uint16_t DataFlash_File::start_new_log(void)
{
stop_logging();
if (_open_error) {
// we have previously failed to open a file - don't try again
// to prevent us trying to open files while in flight
return 0xFFFF;
}
if (_read_fd != -1) {
::close(_read_fd);
_read_fd = -1;
}
uint16_t log_num = find_last_log();
// re-use empty logs if possible
if (_get_log_size(log_num) > 0 || log_num == 0) {
log_num++;
}
if (log_num > MAX_LOG_FILES) {
log_num = 1;
}
char *fname = _log_file_name(log_num);
_write_fd = ::open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666);
if (_write_fd == -1) {
_initialised = false;
_open_error = true;
int saved_errno = errno;
::printf("Log open fail for %s - %s\n",
fname, strerror(saved_errno));
hal.console->printf("Log open fail for %s - %s\n",
fname, strerror(saved_errno));
free(fname);
return 0xFFFF;
}
free(fname);
_write_offset = 0;
_writebuf_head = 0;
_writebuf_tail = 0;
log_write_started = true;
// now update lastlog.txt with the new log number
fname = _lastlog_file_name();
FILE *f = ::fopen(fname, "w");
fprintf(f, "%u\r\n", (unsigned)log_num);
fclose(f);
free(fname);
return log_num;
}
/*
Read the log and print it on port
*/
void DataFlash_File::LogReadProcess(const uint16_t list_entry,
uint16_t start_page, uint16_t end_page,
print_mode_fn print_mode,
AP_HAL::BetterStream *port)
{
uint8_t log_step = 0;
if (!_initialised || _open_error) {
return;
}
const uint16_t log_num = _log_num_from_list_entry(list_entry);
if (log_num == 0) {
return;
}
if (_read_fd != -1) {
::close(_read_fd);
_read_fd = -1;
}
char *fname = _log_file_name(log_num);
if (fname == NULL) {
return;
}
_read_fd = ::open(fname, O_RDONLY);
free(fname);
if (_read_fd == -1) {
return;
}
_read_fd_log_num = log_num;
_read_offset = 0;
if (start_page != 0) {
::lseek(_read_fd, start_page * DATAFLASH_PAGE_SIZE, SEEK_SET);
_read_offset = start_page * DATAFLASH_PAGE_SIZE;
}
uint8_t log_counter = 0;
while (true) {
uint8_t data;
if (::read(_read_fd, &data, 1) != 1) {
// reached end of file
break;
}
_read_offset++;
// This is a state machine to read the packets
switch(log_step) {
case 0:
if (data == HEAD_BYTE1) {
log_step++;
}
break;
case 1:
if (data == HEAD_BYTE2) {
log_step++;
} else {
log_step = 0;
}
break;
case 2:
log_step = 0;
_print_log_entry(data, print_mode, port);
log_counter++;
if (log_counter == 10) {
log_counter = 0;
::lseek(_read_fd, 0, SEEK_CUR);
}
break;
}
if (_read_offset >= (end_page+1) * DATAFLASH_PAGE_SIZE) {
break;
}
}
::close(_read_fd);
_read_fd = -1;
}
/*
this is a lot less verbose than the block interface. Dumping 2Gbyte
of logs a page at a time isn't so useful. Just pull the SD card out
and look at it on your PC
*/
void DataFlash_File::DumpPageInfo(AP_HAL::BetterStream *port)
{
port->printf_P(PSTR("DataFlash: num_logs=%u\n"),
(unsigned)get_num_logs());
}
void DataFlash_File::ShowDeviceInfo(AP_HAL::BetterStream *port)
{
port->printf_P(PSTR("DataFlash logs stored in %s\n"),
_log_directory);
}
/*
list available log numbers
*/
void DataFlash_File::ListAvailableLogs(AP_HAL::BetterStream *port)
{
uint16_t num_logs = get_num_logs();
if (num_logs == 0) {
port->printf_P(PSTR("\nNo logs\n\n"));
return;
}
port->printf_P(PSTR("\n%u logs\n"), (unsigned)num_logs);
for (uint16_t i=1; i<=num_logs; i++) {
uint16_t log_num = _log_num_from_list_entry(i);
char *filename = _log_file_name(log_num);
if (filename != NULL) {
struct stat st;
if (stat(filename, &st) == 0) {
struct tm *tm = gmtime(&st.st_mtime);
port->printf_P(PSTR("Log %u in %s of size %u %u/%u/%u %u:%u\n"),
(unsigned)i,
filename,
(unsigned)st.st_size,
(unsigned)tm->tm_year+1900,
(unsigned)tm->tm_mon+1,
(unsigned)tm->tm_mday,
(unsigned)tm->tm_hour,
(unsigned)tm->tm_min);
}
free(filename);
}
}
port->println();
}
#if CONFIG_HAL_BOARD == HAL_BOARD_SITL || CONFIG_HAL_BOARD == HAL_BOARD_LINUX
void DataFlash_File::flush(void)
{
uint16_t _tail;
uint32_t tnow = hal.scheduler->micros();
hal.scheduler->suspend_timer_procs();
while (_write_fd != -1 && _initialised && !_open_error &&
BUF_AVAILABLE(_writebuf)) {
// convince the IO timer that it really is OK to write out
// less than _writebuf_chunk bytes:
_last_write_time = tnow - 2000000;
_io_timer();
}
hal.scheduler->resume_timer_procs();
if (_write_fd != -1) {
::fsync(_write_fd);
}
}
#endif
void DataFlash_File::_io_timer(void)
{
uint16_t _tail;
if (_write_fd == -1 || !_initialised || _open_error) {
return;
}
uint16_t nbytes = BUF_AVAILABLE(_writebuf);
if (nbytes == 0) {
return;
}
uint32_t tnow = hal.scheduler->micros();
if (nbytes < _writebuf_chunk &&
tnow - _last_write_time < 2000000UL) {
// write in _writebuf_chunk-sized chunks, but always write at
// least once per 2 seconds if data is available
return;
}
hal.util->perf_begin(_perf_write);
_last_write_time = tnow;
if (nbytes > _writebuf_chunk) {
// be kind to the FAT PX4 filesystem
nbytes = _writebuf_chunk;
}
if (_writebuf_head > _tail) {
// only write to the end of the buffer
nbytes = min(nbytes, _writebuf_size - _writebuf_head);
}
// try to align writes on a 512 byte boundary to avoid filesystem
// reads
if ((nbytes + _write_offset) % 512 != 0) {
uint32_t ofs = (nbytes + _write_offset) % 512;
if (ofs < nbytes) {
nbytes -= ofs;
}
}
assert(_writebuf_head+nbytes <= _writebuf_size);
ssize_t nwritten = ::write(_write_fd, &_writebuf[_writebuf_head], nbytes);
if (nwritten <= 0) {
hal.util->perf_count(_perf_errors);
close(_write_fd);
_write_fd = -1;
_initialised = false;
} else {
_write_offset += nwritten;
/*
the best strategy for minimising corruption on microSD cards
seems to be to write in 4k chunks and fsync the file on each
chunk, ensuring the directory entry is updated after each
write.
*/
BUF_ADVANCEHEAD(_writebuf, nwritten);
#if CONFIG_HAL_BOARD != HAL_BOARD_SITL && CONFIG_HAL_BOARD_SUBTYPE != HAL_BOARD_SUBTYPE_LINUX_NONE
::fsync(_write_fd);
#endif
}
hal.util->perf_end(_perf_write);
}
#endif // HAL_OS_POSIX_IO
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