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5ca28f79 | 1 | /* gzlog.h |
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2 | Copyright (C) 2004, 2008, 2012 Mark Adler, all rights reserved |
3 | version 2.2, 14 Aug 2012 | |
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4 | |
5 | This software is provided 'as-is', without any express or implied | |
6 | warranty. In no event will the author be held liable for any damages | |
7 | arising from the use of this software. | |
8 | ||
9 | Permission is granted to anyone to use this software for any purpose, | |
10 | including commercial applications, and to alter it and redistribute it | |
11 | freely, subject to the following restrictions: | |
12 | ||
13 | 1. The origin of this software must not be misrepresented; you must not | |
14 | claim that you wrote the original software. If you use this software | |
15 | in a product, an acknowledgment in the product documentation would be | |
16 | appreciated but is not required. | |
17 | 2. Altered source versions must be plainly marked as such, and must not be | |
18 | misrepresented as being the original software. | |
19 | 3. This notice may not be removed or altered from any source distribution. | |
20 | ||
21 | Mark Adler madler@alumni.caltech.edu | |
22 | */ | |
23 | ||
24 | /* Version History: | |
25 | 1.0 26 Nov 2004 First version | |
26 | 2.0 25 Apr 2008 Complete redesign for recovery of interrupted operations | |
27 | Interface changed slightly in that now path is a prefix | |
28 | Compression now occurs as needed during gzlog_write() | |
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() |
31 | 2.2 14 Aug 2012 Clean up signed comparisons | |
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32 | */ |
33 | ||
34 | /* | |
35 | The gzlog object allows writing short messages to a gzipped log file, | |
36 | opening the log file locked for small bursts, and then closing it. The log | |
37 | object works by appending stored (uncompressed) data to the gzip file until | |
38 | 1 MB has been accumulated. At that time, the stored data is compressed, and | |
39 | replaces the uncompressed data in the file. The log file is truncated to | |
40 | its new size at that time. After each write operation, the log file is a | |
41 | valid gzip file that can decompressed to recover what was written. | |
42 | ||
43 | The gzlog operations can be interupted at any point due to an application or | |
44 | system crash, and the log file will be recovered the next time the log is | |
45 | opened with gzlog_open(). | |
46 | */ | |
47 | ||
48 | #ifndef GZLOG_H | |
49 | #define GZLOG_H | |
50 | ||
51 | /* gzlog object type */ | |
52 | typedef void gzlog; | |
53 | ||
54 | /* Open a gzlog object, creating the log file if it does not exist. Return | |
55 | NULL on error. Note that gzlog_open() could take a while to complete if it | |
56 | has to wait to verify that a lock is stale (possibly for five minutes), or | |
57 | if there is significant contention with other instantiations of this object | |
58 | when locking the resource. path is the prefix of the file names created by | |
59 | this object. If path is "foo", then the log file will be "foo.gz", and | |
60 | other auxiliary files will be created and destroyed during the process: | |
61 | "foo.dict" for a compression dictionary, "foo.temp" for a temporary (next) | |
62 | dictionary, "foo.add" for data being added or compressed, "foo.lock" for the | |
63 | lock file, and "foo.repairs" to log recovery operations performed due to | |
64 | interrupted gzlog operations. A gzlog_open() followed by a gzlog_close() | |
65 | will recover a previously interrupted operation, if any. */ | |
66 | gzlog *gzlog_open(char *path); | |
67 | ||
68 | /* Write to a gzlog object. Return zero on success, -1 if there is a file i/o | |
69 | error on any of the gzlog files (this should not happen if gzlog_open() | |
70 | succeeded, unless the device has run out of space or leftover auxiliary | |
71 | files have permissions or ownership that prevent their use), -2 if there is | |
72 | a memory allocation failure, or -3 if the log argument is invalid (e.g. if | |
73 | it was not created by gzlog_open()). This function will write data to the | |
74 | file uncompressed, until 1 MB has been accumulated, at which time that data | |
75 | will be compressed. The log file will be a valid gzip file upon successful | |
76 | return. */ | |
77 | int gzlog_write(gzlog *log, void *data, size_t len); | |
78 | ||
79 | /* Force compression of any uncompressed data in the log. This should be used | |
80 | sparingly, if at all. The main application would be when a log file will | |
81 | not be appended to again. If this is used to compress frequently while | |
82 | appending, it will both significantly increase the execution time and | |
83 | reduce the compression ratio. The return codes are the same as for | |
84 | gzlog_write(). */ | |
85 | int gzlog_compress(gzlog *log); | |
86 | ||
87 | /* Close a gzlog object. Return zero on success, -3 if the log argument is | |
88 | invalid. The log object is freed, and so cannot be referenced again. */ | |
89 | int gzlog_close(gzlog *log); | |
90 | ||
91 | #endif |