This patch offers a generic interface to allow temp files to be
cached while using an instance of the 'Git' package. If many
temp files are created and destroyed during the execution of a
program, this caching mechanism can help reduce the amount of
files created and destroyed by the filesystem.
The temp_acquire method provides a weak guarantee that a temp
file will not be stolen by subsequent requests. If a file is
locked when another acquire request is made, a simple error is
thrown.
Signed-off-by: Marcus Griep <marcus@xxxxxxxx>
---
perl/Git.pm | 125 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 123 insertions(+), 2 deletions(-)
diff --git a/perl/Git.pm b/perl/Git.pm
index e1ca5b4..405f68f 100644
--- a/perl/Git.pm
+++ b/perl/Git.pm
@@ -57,7 +57,8 @@ require Exporter;
command_output_pipe command_input_pipe command_close_pipe
command_bidi_pipe command_close_bidi_pipe
version exec_path hash_object git_cmd_try
- remote_refs);
+ remote_refs
+ temp_acquire temp_release temp_reset);
=head1 DESCRIPTION
@@ -99,7 +100,9 @@ use Carp qw(carp croak); # but croak is bad - throw instead
use Error qw(:try);
use Cwd qw(abs_path);
use IPC::Open2 qw(open2);
-
+use File::Temp ();
+require File::Spec;
+use Fcntl qw(SEEK_SET SEEK_CUR);
}
@@ -933,6 +936,124 @@ sub _close_cat_blob {
delete @$self{@vars};
}
+
+{ # %TEMP_* Lexical Context
+
+my (%TEMP_LOCKS, %TEMP_FILES);
+
+=item temp_acquire ( NAME )
+
+Attempts to retreive the temporary file mapped to the string C<NAME>. If an
+associated temp file has not been created this session or was closed, it is
+created, cached, and set for autoflush and binmode.
+
+Internally locks the file mapped to C<NAME>. This lock must be released with
+C<temp_release()> when the temp file is no longer needed. Subsequent attempts
+to retrieve temporary files mapped to the same C<NAME> while still locked will
+cause an error. This locking mechanism provides a weak guarantee and is not
+threadsafe. It does provide some error checking to help prevent temp file refs
+writing over one another.
+
+In general, the L<File::Handle> returned should not be closed by consumers as
+it defeats the purpose of this caching mechanism. If you need to close the temp
+file handle, then you should use L<File::Temp> or another temp file faculty
+directly. If a handle is closed and then requested again, then a warning will
+issue.
+
+=cut
+
+sub temp_acquire {
+ my ($self, $name) = _maybe_self(@_);
+
+ my $temp_fd = _temp_cache($name);
+
+ $TEMP_LOCKS{$temp_fd} = 1;
+ $temp_fd;
+}
+
+=item temp_release ( NAME )
+
+=item temp_release ( FILEHANDLE )
+
+Releases a lock acquired through C<temp_acquire()>. Can be called either with
+the C<NAME> mapping used when acquiring the temp file or with the C<FILEHANDLE>
+referencing a locked temp file.
+
+Warns if an attempt is made to release a file that is not locked.
+
+The temp file will be truncated before being released. This can help to reduce
+disk I/O where the system is smart enough to detect the truncation while data
+is in the output buffers. Beware that after the temp file is released and
+truncated, any operations on that file may fail miserably until it is
+re-acquired. All contents are lost between each release and acquire mapped to
+the same string.
+
+=cut
+
+sub temp_release {
+ my ($self, $temp_fd, $trunc) = _maybe_self(@_);
+
+ if (ref($temp_fd) ne 'File::Temp') {
+ $temp_fd = $TEMP_FILES{$temp_fd};
+ }
+ unless ($TEMP_LOCKS{$temp_fd}) {
+ carp "Attempt to release temp file '",
+ $temp_fd, "' that has not been locked";
+ }
+ temp_reset($temp_fd) if $trunc and $temp_fd->opened;
+
+ $TEMP_LOCKS{$temp_fd} = 0;
+ undef;
+}
+
+sub _temp_cache {
+ my ($name) = @_;
+
+ my $temp_fd = \$TEMP_FILES{$name};
+ if (defined $$temp_fd and $$temp_fd->opened) {
+ if ($TEMP_LOCKS{$$temp_fd}) {
+ throw Error::Simple("Temp file with moniker '",
+ $name, "' already in use");
+ }
+ } else {
+ if (defined $$temp_fd) {
+ # then we're here because of a closed handle.
+ carp "Temp file '", $name,
+ "' was closed. Opening replacement.";
+ }
+ $$temp_fd = File::Temp->new(
+ TEMPLATE => 'Git_XXXXXX',
+ DIR => File::Spec->tmpdir
+ ) or throw Error::Simple("couldn't open new temp file");
+ $$temp_fd->autoflush;
+ binmode $$temp_fd;
+ }
+ $$temp_fd;
+}
+
+=item temp_reset ( FILEHANDLE )
+
+Truncates and resets the position of the C<FILEHANDLE>.
+
+=cut
+
+sub temp_reset {
+ my ($self, $temp_fd) = _maybe_self(@_);
+
+ truncate $temp_fd, 0
+ or throw Error::Simple("couldn't truncate file");
+ sysseek($temp_fd, 0, SEEK_SET) and seek($temp_fd, 0, SEEK_SET)
+ or throw Error::Simple("couldn't seek to beginning of file");
+ sysseek($temp_fd, 0, SEEK_CUR) == 0 and tell($temp_fd) == 0
+ or throw Error::Simple("expected file position to be reset");
+}
+
+sub END {
+ unlink values %TEMP_FILES if %TEMP_FILES;
+}
+
+} # %TEMP_* Lexical Context
+
=back
=head1 ERROR HANDLING
--
1.6.0.rc2.6.g8eda3
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