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sd-journal: introduce sd_journal_step_one()

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After the commit 7a4ee86161,
sd_journal_next() following sd_journal_seek_tail() takes no-op,
and we need to call sd_journal_previous(). This may be useful in
some cases, e.g. to fix the issue explained in the previous commit.
This commit is contained in:
Yu Watanabe 2023-05-28 14:20:27 +09:00
parent fb35feae97
commit b78f9481bc
5 changed files with 31 additions and 1 deletions
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3
man/rules/meson.build
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@ -742,7 +742,8 @@ manpages = [
'SD_JOURNAL_FOREACH_BACKWARDS',
'sd_journal_next_skip',
'sd_journal_previous',
'sd_journal_previous_skip'],
'sd_journal_previous_skip',
'sd_journal_step_one'],
''],
['sd_journal_open',
'3',

17
man/sd_journal_next.xml
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@ -18,6 +18,7 @@
<refnamediv>
<refname>sd_journal_next</refname>
<refname>sd_journal_previous</refname>
<refname>sd_journal_step_one</refname>
<refname>sd_journal_next_skip</refname>
<refname>sd_journal_previous_skip</refname>
<refname>SD_JOURNAL_FOREACH</refname>
@ -39,6 +40,12 @@
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_journal_step_one</function></funcdef>
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
<paramdef>int <parameter>advanced</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_journal_next_skip</function></funcdef>
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
@ -77,6 +84,16 @@
<para>Similarly, <function>sd_journal_previous()</function> sets
the read pointer back one entry.</para>
<para><function>sd_journal_step_one()</function> also moves the read pointer. If the current location
is the head of the journal, e.g. when this is called following
<function>sd_journal_seek_head()</function>, then this is equivalent to
<function>sd_journal_next()</function>, and the argument <varname>advanced</varname> will be ignored.
Similary, if the current location is the tail of the journal, e.g. when this is called following
<function>sd_journal_seek_tail()</function>, then this is equivalent to
<function>sd_journal_previous()</function>, and <varname>advanced</varname> will be ignored. Otherwise,
this is equivalent to <function>sd_journal_next()</function> when <varname>advanced</varname> is
non-zero, and <function>sd_journal_previous()</function> when <varname>advanced</varname> is zero.</para>
<para><function>sd_journal_next_skip()</function> and
<function>sd_journal_previous_skip()</function> advance/set back the read pointer by multiple
entries at once, as specified in the <varname>skip</varname> parameter. The <varname>skip</varname>

1
src/libsystemd/libsystemd.sym
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@ -825,4 +825,5 @@ global:
sd_event_trim_memory;
sd_pid_notify_barrier;
sd_event_source_leave_ratelimit;
sd_journal_step_one;
} LIBSYSTEMD_253;

10
src/libsystemd/sd-journal/sd-journal.c
View File

@ -979,6 +979,16 @@ _public_ int sd_journal_previous(sd_journal *j) {
return real_journal_next(j, DIRECTION_UP);
}
_public_ int sd_journal_step_one(sd_journal *j, int advanced) {
assert_return(j, -EINVAL);
if (j->current_location.type == LOCATION_HEAD)
return sd_journal_next(j);
if (j->current_location.type == LOCATION_TAIL)
return sd_journal_previous(j);
return real_journal_next(j, advanced ? DIRECTION_DOWN : DIRECTION_UP);
}
static int real_journal_next_skip(sd_journal *j, direction_t direction, uint64_t skip) {
int c = 0, r;

1
src/systemd/sd-journal.h
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@ -93,6 +93,7 @@ void sd_journal_close(sd_journal *j);
int sd_journal_previous(sd_journal *j);
int sd_journal_next(sd_journal *j);
int sd_journal_step_one(sd_journal *j, int advanced);
int sd_journal_previous_skip(sd_journal *j, uint64_t skip);
int sd_journal_next_skip(sd_journal *j, uint64_t skip);