From e41352b24e29eba43d00a3fd117befaef1d594bc Mon Sep 17 00:00:00 2001 From: Marcus Griep Date: Tue, 12 Aug 2008 12:00:18 -0400 Subject: [PATCH] Git.pm: Add faculties to allow temp files to be cached 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 Acked-by: Eric Wong --- perl/Git.pm | 125 +++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 123 insertions(+), 2 deletions(-) diff --git a/perl/Git.pm b/perl/Git.pm index e1ca5b4a22..405f68fc39 100644 --- a/perl/Git.pm +++ b/perl/Git.pm @@ -57,7 +57,8 @@ =head1 SYNOPSIS 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 @@ =head1 DESCRIPTION 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 @$self{@vars}; } + +{ # %TEMP_* Lexical Context + +my (%TEMP_LOCKS, %TEMP_FILES); + +=item temp_acquire ( NAME ) + +Attempts to retreive the temporary file mapped to the string C. If an +associated temp file has not been created this session or was closed, it is +created, cached, and set for autoflush and binmode. + +Internally locks the file mapped to C. This lock must be released with +C when the temp file is no longer needed. Subsequent attempts +to retrieve temporary files mapped to the same C while still locked will +cause an error. This locking mechanism provides a weak guarantee and is not +threadsafe. It does provide some error checking to help prevent temp file refs +writing over one another. + +In general, the L returned should not be closed by consumers as +it defeats the purpose of this caching mechanism. If you need to close the temp +file handle, then you should use L or another temp file faculty +directly. If a handle is closed and then requested again, then a warning will +issue. + +=cut + +sub temp_acquire { + my ($self, $name) = _maybe_self(@_); + + my $temp_fd = _temp_cache($name); + + $TEMP_LOCKS{$temp_fd} = 1; + $temp_fd; +} + +=item temp_release ( NAME ) + +=item temp_release ( FILEHANDLE ) + +Releases a lock acquired through C. Can be called either with +the C mapping used when acquiring the temp file or with the C +referencing a locked temp file. + +Warns if an attempt is made to release a file that is not locked. + +The temp file will be truncated before being released. This can help to reduce +disk I/O where the system is smart enough to detect the truncation while data +is in the output buffers. Beware that after the temp file is released and +truncated, any operations on that file may fail miserably until it is +re-acquired. All contents are lost between each release and acquire mapped to +the same string. + +=cut + +sub temp_release { + my ($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. + +=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 -- GitLab