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90 lines
4.3 KiB
C
90 lines
4.3 KiB
C
/* gzlog.h
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Copyright (C) 2004, 2008 Mark Adler, all rights reserved
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version 2.0, 25 Apr 2008
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the author be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source distribution.
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Mark Adler madler@alumni.caltech.edu
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*/
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/* Version History:
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1.0 26 Nov 2004 First version
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2.0 25 Apr 2008 Complete redesign for recovery of interrupted operations
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Interface changed slightly in that now path is a prefix
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Compression now occurs as needed during gzlog_write()
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gzlog_write() now always leaves the log file as valid gzip
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*/
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/*
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The gzlog object allows writing short messages to a gzipped log file,
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opening the log file locked for small bursts, and then closing it. The log
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object works by appending stored (uncompressed) data to the gzip file until
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1 MB has been accumulated. At that time, the stored data is compressed, and
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replaces the uncompressed data in the file. The log file is truncated to
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its new size at that time. After each write operation, the log file is a
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valid gzip file that can decompressed to recover what was written.
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The gzlog operations can be interupted at any point due to an application or
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system crash, and the log file will be recovered the next time the log is
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opened with gzlog_open().
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*/
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#ifndef GZLOG_H
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#define GZLOG_H
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/* gzlog object type */
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typedef void gzlog;
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/* Open a gzlog object, creating the log file if it does not exist. Return
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NULL on error. Note that gzlog_open() could take a while to complete if it
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has to wait to verify that a lock is stale (possibly for five minutes), or
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if there is significant contention with other instantiations of this object
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when locking the resource. path is the prefix of the file names created by
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this object. If path is "foo", then the log file will be "foo.gz", and
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other auxiliary files will be created and destroyed during the process:
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"foo.dict" for a compression dictionary, "foo.temp" for a temporary (next)
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dictionary, "foo.add" for data being added or compressed, "foo.lock" for the
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lock file, and "foo.repairs" to log recovery operations performed due to
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interrupted gzlog operations. A gzlog_open() followed by a gzlog_close()
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will recover a previously interrupted operation, if any. */
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gzlog *gzlog_open(char *path);
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/* Write to a gzlog object. Return zero on success, -1 if there is a file i/o
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error on any of the gzlog files (this should not happen if gzlog_open()
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succeeded, unless the device has run out of space or leftover auxiliary
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files have permissions or ownership that prevent their use), -2 if there is
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a memory allocation failure, or -3 if the log argument is invalid (e.g. if
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it was not created by gzlog_open()). This function will write data to the
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file uncompressed, until 1 MB has been accumulated, at which time that data
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will be compressed. The log file will be a valid gzip file upon successful
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return. */
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int gzlog_write(gzlog *log, void *data, size_t len);
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/* Force compression of any uncompressed data in the log. This should be used
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sparingly, if at all. The main application would be when a log file will
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not be appended to again. If this is used to compress frequently while
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appending, it will both significantly increase the execution time and
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reduce the compression ratio. The return codes are the same as for
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gzlog_write(). */
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int gzlog_compress(gzlog *log);
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/* Close a gzlog object. Return zero on success, -3 if the log argument is
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invalid. The log object is freed, and so cannot be referenced again. */
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int gzlog_close(gzlog *log);
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#endif
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