Commit | Line | Data |
---|---|---|
5ca28f79 L |
1 | /* gzlog.h |
2 | Copyright (C) 2004, 2008 Mark Adler, all rights reserved | |
3 | version 2.0, 25 Apr 2008 | |
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 | |
30 | */ | |
31 | ||
32 | /* | |
33 | The gzlog object allows writing short messages to a gzipped log file, | |
34 | opening the log file locked for small bursts, and then closing it. The log | |
35 | object works by appending stored (uncompressed) data to the gzip file until | |
36 | 1 MB has been accumulated. At that time, the stored data is compressed, and | |
37 | replaces the uncompressed data in the file. The log file is truncated to | |
38 | its new size at that time. After each write operation, the log file is a | |
39 | valid gzip file that can decompressed to recover what was written. | |
40 | ||
41 | The gzlog operations can be interupted at any point due to an application or | |
42 | system crash, and the log file will be recovered the next time the log is | |
43 | opened with gzlog_open(). | |
44 | */ | |
45 | ||
46 | #ifndef GZLOG_H | |
47 | #define GZLOG_H | |
48 | ||
49 | /* gzlog object type */ | |
50 | typedef void gzlog; | |
51 | ||
52 | /* Open a gzlog object, creating the log file if it does not exist. Return | |
53 | NULL on error. Note that gzlog_open() could take a while to complete if it | |
54 | has to wait to verify that a lock is stale (possibly for five minutes), or | |
55 | if there is significant contention with other instantiations of this object | |
56 | when locking the resource. path is the prefix of the file names created by | |
57 | this object. If path is "foo", then the log file will be "foo.gz", and | |
58 | other auxiliary files will be created and destroyed during the process: | |
59 | "foo.dict" for a compression dictionary, "foo.temp" for a temporary (next) | |
60 | dictionary, "foo.add" for data being added or compressed, "foo.lock" for the | |
61 | lock file, and "foo.repairs" to log recovery operations performed due to | |
62 | interrupted gzlog operations. A gzlog_open() followed by a gzlog_close() | |
63 | will recover a previously interrupted operation, if any. */ | |
64 | gzlog *gzlog_open(char *path); | |
65 | ||
66 | /* Write to a gzlog object. Return zero on success, -1 if there is a file i/o | |
67 | error on any of the gzlog files (this should not happen if gzlog_open() | |
68 | succeeded, unless the device has run out of space or leftover auxiliary | |
69 | files have permissions or ownership that prevent their use), -2 if there is | |
70 | a memory allocation failure, or -3 if the log argument is invalid (e.g. if | |
71 | it was not created by gzlog_open()). This function will write data to the | |
72 | file uncompressed, until 1 MB has been accumulated, at which time that data | |
73 | will be compressed. The log file will be a valid gzip file upon successful | |
74 | return. */ | |
75 | int gzlog_write(gzlog *log, void *data, size_t len); | |
76 | ||
77 | /* Force compression of any uncompressed data in the log. This should be used | |
78 | sparingly, if at all. The main application would be when a log file will | |
79 | not be appended to again. If this is used to compress frequently while | |
80 | appending, it will both significantly increase the execution time and | |
81 | reduce the compression ratio. The return codes are the same as for | |
82 | gzlog_write(). */ | |
83 | int gzlog_compress(gzlog *log); | |
84 | ||
85 | /* Close a gzlog object. Return zero on success, -3 if the log argument is | |
86 | invalid. The log object is freed, and so cannot be referenced again. */ | |
87 | int gzlog_close(gzlog *log); | |
88 | ||
89 | #endif |