mchapman/zlib
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

zlib 1.2.3.4

Browse Source
This commit is contained in:
Mark Adler
2011-09-09 23:26:40 -07:00
parent 639be99788
commit f6194ef39a
45 changed files with 3663 additions and 873 deletions
Download Patch File Download Diff File Expand all files Collapse all files

87
examples/gzlog.h
View File

@@ -1,6 +1,6 @@
/* gzlog.h
Copyright (C) 2004 Mark Adler, all rights reserved
version 1.0, 26 Nov 2004
Copyright (C) 2004, 2008 Mark Adler, all rights reserved
version 2.0, 25 Apr 2008
This software is provided 'as-is', without any express or implied
warranty. In no event will the author be held liable for any damages
@@ -21,38 +21,69 @@
Mark Adler madler@alumni.caltech.edu
*/
/* Version History:
1.0 26 Nov 2004 First version
2.0 25 Apr 2008 Complete redesign for recovery of interrupted operations
Interface changed slightly in that now path is a prefix
Compression now occurs as needed during gzlog_write()
gzlog_write() now always leaves the log file as valid gzip
*/
/*
The gzlog object allows writing short messages to a gzipped log file,
opening the log file locked for small bursts, and then closing it. The log
object works by appending stored data to the gzip file until 1 MB has been
accumulated. At that time, the stored data is compressed, and replaces the
uncompressed data in the file. The log file is truncated to its new size at
that time. After closing, the log file is always valid gzip file that can
decompressed to recover what was written.
object works by appending stored (uncompressed) data to the gzip file until
1 MB has been accumulated. At that time, the stored data is compressed, and
replaces the uncompressed data in the file. The log file is truncated to
its new size at that time. After each write operation, the log file is a
valid gzip file that can decompressed to recover what was written.
A gzip header "extra" field contains two file offsets for appending. The
first points to just after the last compressed data. The second points to
the last stored block in the deflate stream, which is empty. All of the
data between those pointers is uncompressed.
The gzlog operations can be interupted at any point due to an application or
system crash, and the log file will be recovered the next time the log is
opened with gzlog_open().
*/
#ifndef GZLOG_H
#define GZLOG_H
/* gzlog object type */
typedef void gzlog;
/* Open a gzlog object, creating the log file if it does not exist. Return
NULL on error. Note that gzlog_open() could take a long time to return if
there is difficulty in locking the file. */
void *gzlog_open(char *path);
NULL on error. Note that gzlog_open() could take a while to complete if it
has to wait to verify that a lock is stale (possibly for five minutes), or
if there is significant contention with other instantiations of this object
when locking the resource. path is the prefix of the file names created by
this object. If path is "foo", then the log file will be "foo.gz", and
other auxiliary files will be created and destroyed during the process:
"foo.dict" for a compression dictionary, "foo.temp" for a temporary (next)
dictionary, "foo.add" for data being added or compressed, "foo.lock" for the
lock file, and "foo.repairs" to log recovery operations performed due to
interrupted gzlog operations. A gzlog_open() followed by a gzlog_close()
will recover a previously interrupted operation, if any. */
gzlog *gzlog_open(char *path);
/* Write to a gzlog object. Return non-zero on error. This function will
simply write data to the file uncompressed. Compression of the data
will not occur until gzlog_close() is called. It is expected that
gzlog_write() is used for a short message, and then gzlog_close() is
called. If a large amount of data is to be written, then the application
should write no more than 1 MB at a time with gzlog_write() before
calling gzlog_close() and then gzlog_open() again. */
int gzlog_write(void *log, char *data, size_t len);
/* Write to a gzlog object. Return zero on success, -1 if there is a file i/o
error on any of the gzlog files (this should not happen if gzlog_open()
succeeded, unless the device has run out of space or leftover auxiliary
files have permissions or ownership that prevent their use), -2 if there is
a memory allocation failure, or -3 if the log argument is invalid (e.g. if
it was not created by gzlog_open()). This function will write data to the
file uncompressed, until 1 MB has been accumulated, at which time that data
will be compressed. The log file will be a valid gzip file upon successful
return. */
int gzlog_write(gzlog *log, void *data, size_t len);
/* Close a gzlog object. Return non-zero on error. The log file is locked
until this function is called. This function will compress stored data
at the end of the gzip file if at least 1 MB has been accumulated. Note
that the file will not be a valid gzip file until this function completes.
*/
int gzlog_close(void *log);
/* Force compression of any uncompressed data in the log. This should be used
sparingly, if at all. The main application would be when a log file will
not be appended to again. If this is used to compress frequently while
appending, it will both significantly increase the execution time and
reduce the compression ratio. The return codes are the same as for
gzlog_write(). */
int gzlog_compress(gzlog *log);
/* Close a gzlog object. Return zero on success, -3 if the log argument is
invalid. The log object is freed, and so cannot be referenced again. */
int gzlog_close(gzlog *log);
#endif