9e052883 |
1 | /* gzlog.h |
2 | Copyright (C) 2004, 2008, 2012 Mark Adler, all rights reserved |
3 | version 2.2, 14 Aug 2012 |
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 | 2.1 8 Jul 2012 Fix argument checks in gzlog_compress() and gzlog_write() |
31 | 2.2 14 Aug 2012 Clean up signed comparisons |
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 interrupted 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 |