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Tidy up comments.

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This commit is contained in:
Andrew Wood
2026-04-15 22:00:50 +01:00
parent 2e08bbb20a
commit 39c7d4f586
1 changed files with 85 additions and 70 deletions
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src/pv/loop.c
+85 -70
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@@ -1,5 +1,6 @@
/*
* Functions providing the main transfer or file descriptor watching loop.
* Functions providing the main transfer loop, the file descriptor watching
* loop, and the query loop (watching another PV process).
*
* Copyright 2002-2008, 2010, 2012-2015, 2017, 2021, 2023-2026 Andrew Wood
*
@@ -55,7 +56,7 @@ static long ldsqrt(long double value)
/*
* If the flag is set to say that a terminal resize signal was received,
* clear the flag and resize the display, and return true.
* clear the flag, resize the display, and return true.
*/
static bool pv__resize_display_on_signal(pvstate_t state)
{
@@ -95,7 +96,7 @@ static void pv__show_stats(pvstate_t state)
long double rate_mean, rate_variance, rate_deviation;
int stats_size;
/* flawfinder: made safe by use of pv_snprintf() */
/* flawfinder: made safe by use of pv_snprintf(). */
rate_mean = state->calc.rate_sum / ((long double) (state->calc.measurements_taken));
rate_variance =
@@ -126,7 +127,7 @@ static void pv__show_stats(pvstate_t state)
char msg_buf[256]; /* flawfinder: ignore */
int msg_size;
/* flawfinder: made safe by use of pv_snprintf() */
/* flawfinder: made safe by use of pv_snprintf(). */
memset(msg_buf, 0, sizeof(msg_buf));
msg_size = pv_snprintf(msg_buf, sizeof(msg_buf), "%s\n", _("rate not measured"));
@@ -151,8 +152,8 @@ static long double pv__elapsed_transfer_time(const struct timespec *loop_start_t
memset(&transfer_elapsed, 0, sizeof(transfer_elapsed));
/*
* Calculate the effective start time: the time we actually started,
* plus the total time we spent stopped.
* Calculate the effective start time: the time the loop started,
* plus the total time spent stopped.
*/
pv_elapsedtime_add(&effective_start_time, loop_start_time, total_stoppage_time);
@@ -211,6 +212,7 @@ static void pv__monitor_exchange(pvstate_t state)
result = select(max_fd + 1, &readfds, &writefds, &exceptfds, &tv);
/* End the loop if the select() failed or there's no action to take. */
if (result <= 0)
break;
@@ -222,13 +224,16 @@ static void pv__monitor_exchange(pvstate_t state)
off_t otherside_transferred;
ssize_t nread;
/* Read the position of the other monitor. */
otherside_transferred = 0;
nread = read(state->control.othermonitor_read_fd, &otherside_transferred, /* flawfinder: ignore */
sizeof(otherside_transferred));
/*
* flawfinder rationale: no buffer overflow possible
* as we read a fixed size to a fixed point.
* as the read() is of a fixed size, to a fixed
* position.
*/
if (0 == nread) {
@@ -255,6 +260,8 @@ static void pv__monitor_exchange(pvstate_t state)
) {
ssize_t nwritten;
/* Write the current position to the other monitor. */
nwritten =
write(state->control.othermonitor_write_fd, &(state->transfer.transferred),
sizeof(state->transfer.transferred));
@@ -282,7 +289,7 @@ static void pv__monitor_exchange(pvstate_t state)
/*
* Pipe data from a list of files to standard output, giving information
* Transfer data from a list of files to standard output, giving information
* about the transfer on standard error according to the given options.
*
* Returns nonzero on error.
@@ -301,6 +308,8 @@ int pv_main_loop(pvstate_t state)
bool output_is_pipe;
/*
* Notes on line mode:
*
* "written" is ALWAYS bytes written by the last transfer.
*
* "lineswritten" is the lines written by the last transfer,
@@ -337,15 +346,21 @@ int pv_main_loop(pvstate_t state)
}
/*
* Note that we could reduce the size of the output pipe buffer like
* this, to avoid the case where we write a load of data and it just
* goes into the buffer so we think we're done, but the consumer
* takes ages to process it:
* There can be a problem where data is written to the output and
* from the writer's point of view, it's complete, but because the
* consumer is processing it slowly, the data is really sitting in
* the pipe buffer between the writer and the consumer. This gives
* a misleading impression of progress.
*
* It could be avoided by reducing the size of the pipe buffer:
*
* fcntl(output_fd, F_SETPIPE_SZ, 4096);
*
* If we can peek at how much has been consumed by the other end, we
* don't need to.
* That isn't always available, and can have side effects such as
* reducing efficiency. Instead, if the FIONREAD ioctl is
* available, the amount of data waiting in the pipe buffer is
* checked ("written_but_not_consumed"), and used to adjust the
* reported progress.
*/
pv_crs_init(&(state->cursor), &(state->control), &(state->flags));
@@ -394,7 +409,7 @@ int pv_main_loop(pvstate_t state)
}
/*
* Exit early if there was no readable input file.
* Return early if there was no readable input file.
*/
if (input_fd < 0) {
if (state->control.cursor)
@@ -402,7 +417,7 @@ int pv_main_loop(pvstate_t state)
return state->status.exit_status;
}
#if HAVE_POSIX_FADVISE
/* Advise the OS that we will only be reading sequentially. */
/* Advise the OS that reads will all be sequential. */
(void) posix_fadvise(input_fd, 0, 0, POSIX_FADV_SEQUENTIAL);
#endif
@@ -418,8 +433,8 @@ int pv_main_loop(pvstate_t state)
#if HAVE_STRUCT_STAT_ST_BLKSIZE
/*
* Set target buffer size if the initial file's block size can be
* read and we weren't given a target buffer size.
* Set the target buffer size if the initial file's block size can
* be read and a target buffer size wasn't explicitly set already.
*/
if (0 == state->control.target_buffer_size) {
struct stat sb;
@@ -485,8 +500,8 @@ int pv_main_loop(pvstate_t state)
}
/*
* If we have to stop at "size" bytes, make sure we don't
* try to write more than we're allowed to.
* If stopping at "size" bytes, restrict "cansend" to keep
* within that limit, and flag EOF when it is reached.
*/
if ((0 < state->control.size) && (state->control.stop_at_size)) {
if ((state->control.size < (state->transfer.total_written + cansend))
@@ -559,9 +574,9 @@ int pv_main_loop(pvstate_t state)
if (output_is_pipe && !state->control.linemode) {
/*
* Writing bytes to a pipe - the amount transferred
* to the receiver is the total amount we've
* written, minus what's sitting in the pipe buffer
* waiting for the receiver to consume it.
* to the receiver is the total amount written,
* minus what's sitting in the pipe buffer waiting
* for the receiver to consume it.
*/
state->transfer.transferred -= state->transfer.written_but_not_consumed;
@@ -569,12 +584,12 @@ int pv_main_loop(pvstate_t state)
&& NULL != state->transfer.line_positions) {
/*
* Writing lines to a pipe - similar to above, but
* we have to work out how many lines the
* yet-to-be-consumed data in the buffer equates to.
* with the added complication of having to
* determine how many lines the yet-to-be-consumed
* data in the buffer equates to.
*
* To do this, we walk backwards through our record
* of the line positions in the output we've
* written.
* To do this, walk backwards through the record of
* the line positions in the output.
*/
off_t last_consumed_position =
state->transfer.last_output_position - state->transfer.written_but_not_consumed;
@@ -586,10 +601,10 @@ int pv_main_loop(pvstate_t state)
* positions[head-2] = position of second last separator written
* etc
*
* We start at [head-1] and go backwards, wrapping
* Start at [head-1] and go backwards, wrapping
* around as it's a circular buffer, stopping at the
* length (number of positions stored), or when we
* have gone before the last consumed position.
* length (number of positions stored), or after
* going before the last consumed position.
*/
for (line_from_end = 0; line_from_end < state->transfer.line_positions_length; line_from_end++) {
size_t array_index;
@@ -620,7 +635,7 @@ int pv_main_loop(pvstate_t state)
eof_in = false;
eof_out = false;
#if HAVE_POSIX_FADVISE
/* Advise the OS that we will only be reading sequentially. */
/* Advise the OS that reads will all be sequential. */
(void) posix_fadvise(input_fd, 0, 0, POSIX_FADV_SEQUENTIAL);
#endif
}
@@ -630,9 +645,9 @@ int pv_main_loop(pvstate_t state)
pv_elapsedtime_read(&cur_time);
/*
* If we've read everything and written everything, and the
* output pipe buffer is empty, then set the final update
* flag, and force a display update.
* If everything has been read and written, and the output
* pipe buffer is empty, then set the final update flag, and
* force a display update.
*/
if (eof_in && eof_out && 0 == state->transfer.written_but_not_consumed) {
final_update = true;
@@ -650,9 +665,9 @@ int pv_main_loop(pvstate_t state)
}
/*
* If we've read everything and written everything, and the
* output pipe buffer is NOT empty, then pause a short while
* so we don't spin in a tight loop waiting for the output
* If everything has been read and written, and the output
* pipe buffer is NOT empty, then pause a short while to
* avoid spinning in a tight loop waiting for the output
* buffer to empty (#164).
*/
if (eof_in && eof_out && state->transfer.written_but_not_consumed > 0) {
@@ -661,10 +676,10 @@ int pv_main_loop(pvstate_t state)
}
/*
* If -W was given, we don't output anything until we have
* written a byte (or line, in line mode), at which point
* we then count time as if we started when the first byte
* was received.
* If -W was given, produce no display until one byte (or
* line, in line mode) has been written, at which point the
* transfer time is counted as if it started when that first
* byte was received.
*/
if (state->control.wait) {
/* Restart the loop if nothing written yet. */
@@ -680,13 +695,13 @@ int pv_main_loop(pvstate_t state)
/*
* Reset the timer offset counter now that data
* transfer has begun, otherwise if we had been
* stopped and started (with ^Z / SIGTSTOP)
* previously (while waiting for data), the timers
* will be wrongly offset.
* transfer has begun. Otherwise, if there had
* already been a stop and start (with ^Z /
* SIGTSTOP) while waiting for data, the timers
* would be wrongly offset.
*
* While we reset the offset counter we must disable
* SIGTSTOP so things don't mess up.
* While this reset is being done, SIGTSTOP must be
* disabled so it doesn't update the offset again.
*/
pv_sig_nopause();
pv_elapsedtime_read(&start_time);
@@ -706,8 +721,8 @@ int pv_main_loop(pvstate_t state)
pv__elapsed_transfer_time(&start_time, &cur_time, &(state->signal.total_stoppage_time));
/*
* Just go round the loop again if there's no display and
* we're not reporting statistics.
* Restart the loop if there's no display and statistics are
* not being reported.
*/
if (state->control.no_display && !state->control.show_stats) {
continue;
@@ -770,20 +785,20 @@ int pv_main_loop(pvstate_t state)
static bool format_contains_name(const char *format_string)
{
while ('\0' != format_string[0]) {
/* If we're not on a '%' character, move on. */
/* If not on a '%' character, move on. */
if ('%' != format_string[0]) {
format_string++;
continue;
}
/* Move past the '%'. */
format_string++;
/* Early return if we've run out of string. */
/* Early return if the string ran out. */
if ('\0' == format_string[0])
return false;
/* If we've found "%N", return true. */
/* True result if "%N" was found. */
if ('N' == format_string[0])
return true;
/* If we've found "%%", move on and go back round the loop. */
/* If "%%" was found, move past it and go back round the loop. */
if ('%' == format_string[0]) {
format_string++;
continue;
@@ -833,8 +848,8 @@ static void pv_watchfd_update_format_string(pvstate_t state)
/*
* Make sure there's a format string, and then insert %N into it if
* it's not present AND we're either watching more than one item, or
* the item we're watching is a whole PID, not a single FD.
* it's not present AND either more than one item is being watched,
* or the item being watched is a whole PID, not a single FD.
*/
original_format_string = state->control.format_string;
if (NULL == original_format_string)
@@ -1053,11 +1068,11 @@ int pv_watchfd_loop(pvstate_t state)
pv_elapsedtime_copy(&next_update, &cur_time);
/*
* Resize the display, if a resize signal was received.
* If a resize signal was received, resize the display.
*
* We also set a local flag to tell the display loop below
* to trigger a name reset and display reparse for every FD
* output line, to inherit the size change.
* This also sets a local flag to tell the display loop
* below to trigger a name reset and display reparse for
* every FD output line, to inherit the size change.
*/
terminal_resized = pv__resize_display_on_signal(state);
@@ -1115,7 +1130,7 @@ int pv_watchfd_loop(pvstate_t state)
if (info_item->unused)
continue;
/* No more lines if we've filled the display. */
/* No more lines if the display is full. */
if (displayed_lines >= (int) (state->control.height))
break;
@@ -1231,9 +1246,9 @@ int pv_watchfd_loop(pvstate_t state)
/*@-mustfreeonly@ */
state->control.name = NULL;
/*
* splint warns of a memory leak, but we'd
* set name to be an alias of display_name,
* so nothing is lost here.
* splint warns of a memory leak, but name
* was an alias of display_name, so nothing
* is lost here.
*/
/*@+mustfreeonly@ */
@@ -1243,8 +1258,8 @@ int pv_watchfd_loop(pvstate_t state)
}
/*
* Write blank lines if we're writing fewer lines than last
* time.
* Write extra blank lines if fewer lines were written than
* last time around the loop.
*/
blank_lines = prev_displayed_lines - displayed_lines;
prev_displayed_lines = displayed_lines;
@@ -1371,8 +1386,8 @@ int pv_query_loop(pvstate_t state, pid_t query)
pv_elapsedtime_read(&cur_time);
/*
* Just go round the loop again if there's no display and
* we're not reporting statistics.
* If there's no display and statistics aren't being
* reported, do nothing but go round the loop again.
*/
if (state->control.no_display && !state->control.show_stats) {
pv_nanosleep(50000000);
@@ -1380,8 +1395,8 @@ int pv_query_loop(pvstate_t state, pid_t query)
}
/*
* If -W was given, we don't output anything until something
* has been transferred.
* If -W was given, produce no display until something has
* been transferred.
*/
if (state->control.wait) {
/* Restart the loop if nothing written yet. */