| 1 | /* gzlog.h
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| 2 | Copyright (C) 2004, 2008, 2012 Mark Adler, all rights reserved
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| 3 | version 2.2, 14 Aug 2012
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| 4 |
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| 5 | This software is provided 'as-is', without any express or implied
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| 6 | warranty. In no event will the author be held liable for any damages
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| 7 | arising from the use of this software.
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| 8 |
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| 9 | Permission is granted to anyone to use this software for any purpose,
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| 10 | including commercial applications, and to alter it and redistribute it
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| 11 | freely, subject to the following restrictions:
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| 12 |
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| 13 | 1. The origin of this software must not be misrepresented; you must not
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| 14 | claim that you wrote the original software. If you use this software
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| 15 | in a product, an acknowledgment in the product documentation would be
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| 16 | appreciated but is not required.
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| 17 | 2. Altered source versions must be plainly marked as such, and must not be
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| 18 | misrepresented as being the original software.
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| 19 | 3. This notice may not be removed or altered from any source distribution.
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| 20 |
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| 21 | Mark Adler madler@alumni.caltech.edu
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| 22 | */
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| 23 |
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| 24 | /* Version History:
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| 25 | 1.0 26 Nov 2004 First version
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| 26 | 2.0 25 Apr 2008 Complete redesign for recovery of interrupted operations
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| 27 | Interface changed slightly in that now path is a prefix
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| 28 | Compression now occurs as needed during gzlog_write()
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| 29 | gzlog_write() now always leaves the log file as valid gzip
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| 30 | 2.1 8 Jul 2012 Fix argument checks in gzlog_compress() and gzlog_write()
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| 31 | 2.2 14 Aug 2012 Clean up signed comparisons
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| 32 | */
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| 33 |
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| 34 | /*
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| 35 | The gzlog object allows writing short messages to a gzipped log file,
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| 36 | opening the log file locked for small bursts, and then closing it. The log
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| 37 | object works by appending stored (uncompressed) data to the gzip file until
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| 38 | 1 MB has been accumulated. At that time, the stored data is compressed, and
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| 39 | replaces the uncompressed data in the file. The log file is truncated to
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| 40 | its new size at that time. After each write operation, the log file is a
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| 41 | valid gzip file that can decompressed to recover what was written.
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| 42 |
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| 43 | The gzlog operations can be interupted at any point due to an application or
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| 44 | system crash, and the log file will be recovered the next time the log is
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| 45 | opened with gzlog_open().
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| 46 | */
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| 47 |
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| 48 | #ifndef GZLOG_H
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| 49 | #define GZLOG_H
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| 50 |
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| 51 | /* gzlog object type */
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| 52 | typedef void gzlog;
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| 53 |
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| 54 | /* Open a gzlog object, creating the log file if it does not exist. Return
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| 55 | NULL on error. Note that gzlog_open() could take a while to complete if it
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| 56 | has to wait to verify that a lock is stale (possibly for five minutes), or
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| 57 | if there is significant contention with other instantiations of this object
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| 58 | when locking the resource. path is the prefix of the file names created by
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| 59 | this object. If path is "foo", then the log file will be "foo.gz", and
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| 60 | other auxiliary files will be created and destroyed during the process:
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| 61 | "foo.dict" for a compression dictionary, "foo.temp" for a temporary (next)
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| 62 | dictionary, "foo.add" for data being added or compressed, "foo.lock" for the
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| 63 | lock file, and "foo.repairs" to log recovery operations performed due to
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| 64 | interrupted gzlog operations. A gzlog_open() followed by a gzlog_close()
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| 65 | will recover a previously interrupted operation, if any. */
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| 66 | gzlog *gzlog_open(char *path);
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| 67 |
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| 68 | /* Write to a gzlog object. Return zero on success, -1 if there is a file i/o
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| 69 | error on any of the gzlog files (this should not happen if gzlog_open()
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| 70 | succeeded, unless the device has run out of space or leftover auxiliary
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| 71 | files have permissions or ownership that prevent their use), -2 if there is
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| 72 | a memory allocation failure, or -3 if the log argument is invalid (e.g. if
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| 73 | it was not created by gzlog_open()). This function will write data to the
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| 74 | file uncompressed, until 1 MB has been accumulated, at which time that data
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| 75 | will be compressed. The log file will be a valid gzip file upon successful
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| 76 | return. */
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| 77 | int gzlog_write(gzlog *log, void *data, size_t len);
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| 78 |
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| 79 | /* Force compression of any uncompressed data in the log. This should be used
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| 80 | sparingly, if at all. The main application would be when a log file will
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| 81 | not be appended to again. If this is used to compress frequently while
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| 82 | appending, it will both significantly increase the execution time and
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| 83 | reduce the compression ratio. The return codes are the same as for
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| 84 | gzlog_write(). */
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| 85 | int gzlog_compress(gzlog *log);
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| 86 |
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| 87 | /* Close a gzlog object. Return zero on success, -3 if the log argument is
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| 88 | invalid. The log object is freed, and so cannot be referenced again. */
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| 89 | int gzlog_close(gzlog *log);
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| 90 |
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| 91 | #endif
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