| 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 |