Re: [PATCH] refs.c: change read_ref_at to use the reflog iterators

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Ronnie Sahlberg <sahlberg@xxxxxxxxxx> writes:

> read_ref_at has its own parsing of the reflog file for no really good reason
> so lets change this to use the existing reflog iterators. This removes one
> instance where we manually unmarshall the reflog file format.
>
> Log messages for errors are changed slightly. We no longer print the file
> name for the reflog, instead we refer to it as 'Log for ref <refname>'.
> This might be a minor useability regression, but I don't really think so, since
> experienced users would know where the log is anyway and inexperienced users
> would not know what to do about/how to repair 'Log ... has gap ...' anyway.
>
> Adapt the t1400 test to handle the cahnge in log messages.
>
> Signed-off-by: Ronnie Sahlberg <sahlberg@xxxxxxxxxx>
> ---
>  refs.c                | 217 ++++++++++++++++++++++++++++----------------------
>  t/t1400-update-ref.sh |   4 +-
>  2 files changed, 122 insertions(+), 99 deletions(-)

After reading the log message "we are removing one redundant
implementation", I would have expected that such a change would
remove a lot more lines than it would add.  Seeing the diffstat, I
have to wonder if the fact that we need more lines to reuse the API
is an indication that the reflog iterator API is overly cumbersome
to use, perhaps requiring too much boilerplate or something.

The update in the error message may be a side-effect, but I think it
is a change in the good direction.

Thanks.

> diff --git a/refs.c b/refs.c
> index 6898263..99d4832 100644
> --- a/refs.c
> +++ b/refs.c
> @@ -2936,109 +2936,132 @@ static char *ref_msg(const char *line, const char *endp)
>  	return xmemdupz(line, ep - line);
>  }
>  
> +struct read_ref_at_cb {
> +	const char *refname;
> +	unsigned long at_time;
> +	int cnt;
> +	int reccnt;
> +	unsigned char *sha1;
> +	int found_it;
> +
> +	char osha1[20];
> +	char nsha1[20];
> +	int tz;
> +	unsigned long date;
> +	char **msg;
> +	unsigned long *cutoff_time;
> +	int *cutoff_tz;
> +	int *cutoff_cnt;
> +};
> +
> +static int read_ref_at_ent(unsigned char *osha1, unsigned char *nsha1,
> +		const char *email, unsigned long timestamp, int tz,
> +		const char *message, void *cb_data)
> +{
> +	struct read_ref_at_cb *cb = cb_data;
> +
> +	cb->reccnt++;
> +	cb->tz = tz;
> +	cb->date = timestamp;
> +
> +	if (timestamp <= cb->at_time || cb->cnt == 0) {
> +		if (cb->msg)
> +			*cb->msg = xstrdup(message);
> +		if (cb->cutoff_time)
> +			*cb->cutoff_time = timestamp;
> +		if (cb->cutoff_tz)
> +			*cb->cutoff_tz = tz;
> +		if (cb->cutoff_cnt)
> +			*cb->cutoff_cnt = cb->reccnt - 1;
> +
> +		/*
> +		 * we have not yet updated cb->[n|o]sha1 so they still
> +		 * hold the values for the previous record.
> +		 */
> +		if (!is_null_sha1(cb->osha1)) {
> +			hashcpy(cb->sha1, nsha1);
> +			if (hashcmp(cb->osha1, nsha1))
> +				warning("Log for ref %s has gap after %s.",
> +					cb->refname, show_date(cb->date, cb->tz, DATE_RFC2822));
> +		}
> +		else if (cb->date == cb->at_time)
> +			hashcpy(cb->sha1, nsha1);
> +		else
> +			if (hashcmp(nsha1, cb->sha1))
> +				warning("Log for ref %s unexpectedly ended on %s.",
> +					cb->refname, show_date(cb->date, cb->tz,
> +							   DATE_RFC2822));
> +
> +		/* 
> +		 * return 1. Not to signal an error but to break the loop
> +		 * since we have found the entry we want.
> +		 */
> +		hashcpy(cb->osha1, osha1);
> +		hashcpy(cb->nsha1, nsha1);
> +		cb->found_it = 1;
> +		return 1;
> +	}
> +
> +	hashcpy(cb->osha1, osha1);
> +	hashcpy(cb->nsha1, nsha1);
> +	if (cb->cnt > 0)
> +		cb->cnt--;
> +
> +	return 0;
> +}
> +
> +static int read_ref_at_ent_oldest(unsigned char *osha1, unsigned char *nsha1,
> +				  const char *email, unsigned long timestamp,
> +				  int tz, const char *message, void *cb_data)
> +{
> +	struct read_ref_at_cb *cb = cb_data;
> +
> +	if (cb->msg)
> +		*cb->msg = xstrdup(message);
> +	if (cb->cutoff_time)
> +		*cb->cutoff_time = timestamp;
> +	if (cb->cutoff_tz)
> +		*cb->cutoff_tz = tz;
> +	if (cb->cutoff_cnt)
> +		*cb->cutoff_cnt = cb->reccnt - 1;
> +
> +	hashcpy(cb->sha1, osha1);
> +	if (is_null_sha1(cb->sha1))
> +		hashcpy(cb->sha1, nsha1);
> +
> +	/* 
> +	 * return 1. Not to signal an error but to break the loop
> +	 * since we have found the entry we want.
> +	 */
> +	return 1;
> +}
> +
>  int read_ref_at(const char *refname, unsigned long at_time, int cnt,
>  		unsigned char *sha1, char **msg,
>  		unsigned long *cutoff_time, int *cutoff_tz, int *cutoff_cnt)
>  {
> -	const char *logfile, *logdata, *logend, *rec, *lastgt, *lastrec;
> -	char *tz_c;
> -	int logfd, tz, reccnt = 0;
> -	struct stat st;
> -	unsigned long date;
> -	unsigned char logged_sha1[20];
> -	void *log_mapped;
> -	size_t mapsz;
> +	struct read_ref_at_cb cb;
>  
> -	logfile = git_path("logs/%s", refname);
> -	logfd = open(logfile, O_RDONLY, 0);
> -	if (logfd < 0)
> -		die_errno("Unable to read log '%s'", logfile);
> -	fstat(logfd, &st);
> -	if (!st.st_size)
> -		die("Log %s is empty.", logfile);
> -	mapsz = xsize_t(st.st_size);
> -	log_mapped = xmmap(NULL, mapsz, PROT_READ, MAP_PRIVATE, logfd, 0);
> -	logdata = log_mapped;
> -	close(logfd);
> +	memset(&cb, 0, sizeof(cb));
> +	cb.refname = refname;
> +	cb.at_time = at_time;
> +	cb.cnt = cnt;
> +	cb.msg = msg;
> +	cb.cutoff_time = cutoff_time;
> +	cb.cutoff_tz = cutoff_tz;
> +	cb.cutoff_cnt = cutoff_cnt;
> +	cb.sha1 = sha1;
> +
> +	for_each_reflog_ent_reverse(refname, read_ref_at_ent, &cb);
> +
> +	if (!cb.reccnt)
> +		die("Log for %s is empty.", refname);
> +
> +	if (cb.found_it)
> +		return 0;
> +
> +	for_each_reflog_ent(refname, read_ref_at_ent_oldest, &cb);
>  
> -	lastrec = NULL;
> -	rec = logend = logdata + st.st_size;
> -	while (logdata < rec) {
> -		reccnt++;
> -		if (logdata < rec && *(rec-1) == '\n')
> -			rec--;
> -		lastgt = NULL;
> -		while (logdata < rec && *(rec-1) != '\n') {
> -			rec--;
> -			if (*rec == '>')
> -				lastgt = rec;
> -		}
> -		if (!lastgt)
> -			die("Log %s is corrupt.", logfile);
> -		date = strtoul(lastgt + 1, &tz_c, 10);
> -		if (date <= at_time || cnt == 0) {
> -			tz = strtoul(tz_c, NULL, 10);
> -			if (msg)
> -				*msg = ref_msg(rec, logend);
> -			if (cutoff_time)
> -				*cutoff_time = date;
> -			if (cutoff_tz)
> -				*cutoff_tz = tz;
> -			if (cutoff_cnt)
> -				*cutoff_cnt = reccnt - 1;
> -			if (lastrec) {
> -				if (get_sha1_hex(lastrec, logged_sha1))
> -					die("Log %s is corrupt.", logfile);
> -				if (get_sha1_hex(rec + 41, sha1))
> -					die("Log %s is corrupt.", logfile);
> -				if (hashcmp(logged_sha1, sha1)) {
> -					warning("Log %s has gap after %s.",
> -						logfile, show_date(date, tz, DATE_RFC2822));
> -				}
> -			}
> -			else if (date == at_time) {
> -				if (get_sha1_hex(rec + 41, sha1))
> -					die("Log %s is corrupt.", logfile);
> -			}
> -			else {
> -				if (get_sha1_hex(rec + 41, logged_sha1))
> -					die("Log %s is corrupt.", logfile);
> -				if (hashcmp(logged_sha1, sha1)) {
> -					warning("Log %s unexpectedly ended on %s.",
> -						logfile, show_date(date, tz, DATE_RFC2822));
> -				}
> -			}
> -			munmap(log_mapped, mapsz);
> -			return 0;
> -		}
> -		lastrec = rec;
> -		if (cnt > 0)
> -			cnt--;
> -	}
> -
> -	rec = logdata;
> -	while (rec < logend && *rec != '>' && *rec != '\n')
> -		rec++;
> -	if (rec == logend || *rec == '\n')
> -		die("Log %s is corrupt.", logfile);
> -	date = strtoul(rec + 1, &tz_c, 10);
> -	tz = strtoul(tz_c, NULL, 10);
> -	if (get_sha1_hex(logdata, sha1))
> -		die("Log %s is corrupt.", logfile);
> -	if (is_null_sha1(sha1)) {
> -		if (get_sha1_hex(logdata + 41, sha1))
> -			die("Log %s is corrupt.", logfile);
> -	}
> -	if (msg)
> -		*msg = ref_msg(logdata, logend);
> -	munmap(log_mapped, mapsz);
> -
> -	if (cutoff_time)
> -		*cutoff_time = date;
> -	if (cutoff_tz)
> -		*cutoff_tz = tz;
> -	if (cutoff_cnt)
> -		*cutoff_cnt = reccnt;
>  	return 1;
>  }
>  
> diff --git a/t/t1400-update-ref.sh b/t/t1400-update-ref.sh
> index 4e2459a..0218e96 100755
> --- a/t/t1400-update-ref.sh
> +++ b/t/t1400-update-ref.sh
> @@ -235,7 +235,7 @@ test_expect_success \
>  	'rm -f o e &&
>  	 git rev-parse --verify "master@{2005-05-26 23:33:01}" >o 2>e &&
>  	 test '"$B"' = $(cat o) &&
> -	 test "warning: Log .git/logs/'"$m has gap after $gd"'." = "$(cat e)"'
> +	 test "warning: Log for ref '"$m has gap after $gd"'." = "$(cat e)"'
>  test_expect_success \
>  	'Query "master@{2005-05-26 23:38:00}" (middle of history)' \
>  	'rm -f o e &&
> @@ -253,7 +253,7 @@ test_expect_success \
>  	'rm -f o e &&
>  	 git rev-parse --verify "master@{2005-05-28}" >o 2>e &&
>  	 test '"$D"' = $(cat o) &&
> -	 test "warning: Log .git/logs/'"$m unexpectedly ended on $ld"'." = "$(cat e)"'
> +	 test "warning: Log for ref '"$m unexpectedly ended on $ld"'." = "$(cat e)"'
>  
>  
>  rm -f .git/$m .git/logs/$m expect
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