| /* gzlog.h | |
| Copyright (C) 2004, 2008, 2012 Mark Adler, all rights reserved | |
| version 2.2, 14 Aug 2012 | |
| This software is provided 'as-is', without any express or implied | |
| warranty. In no event will the author be held liable for any damages | |
| arising from the use of this software. | |
| Permission is granted to anyone to use this software for any purpose, | |
| including commercial applications, and to alter it and redistribute it | |
| freely, subject to the following restrictions: | |
| 1. The origin of this software must not be misrepresented; you must not | |
| claim that you wrote the original software. If you use this software | |
| in a product, an acknowledgment in the product documentation would be | |
| appreciated but is not required. | |
| 2. Altered source versions must be plainly marked as such, and must not be | |
| misrepresented as being the original software. | |
| 3. This notice may not be removed or altered from any source distribution. | |
| Mark Adler madler@alumni.caltech.edu | |
| */ | |
| /* Version History: | |
| 1.0 26 Nov 2004 First version | |
| 2.0 25 Apr 2008 Complete redesign for recovery of interrupted operations | |
| Interface changed slightly in that now path is a prefix | |
| Compression now occurs as needed during gzlog_write() | |
| gzlog_write() now always leaves the log file as valid gzip | |
| 2.1 8 Jul 2012 Fix argument checks in gzlog_compress() and gzlog_write() | |
| 2.2 14 Aug 2012 Clean up signed comparisons | |
| */ | |
| /* | |
| The gzlog object allows writing short messages to a gzipped log file, | |
| opening the log file locked for small bursts, and then closing it. The log | |
| object works by appending stored (uncompressed) data to the gzip file until | |
| 1 MB has been accumulated. At that time, the stored data is compressed, and | |
| replaces the uncompressed data in the file. The log file is truncated to | |
| its new size at that time. After each write operation, the log file is a | |
| valid gzip file that can decompressed to recover what was written. | |
| The gzlog operations can be interrupted at any point due to an application or | |
| system crash, and the log file will be recovered the next time the log is | |
| opened with gzlog_open(). | |
| */ | |
| /* gzlog object type */ | |
| typedef void gzlog; | |
| /* Open a gzlog object, creating the log file if it does not exist. Return | |
| NULL on error. Note that gzlog_open() could take a while to complete if it | |
| has to wait to verify that a lock is stale (possibly for five minutes), or | |
| if there is significant contention with other instantiations of this object | |
| when locking the resource. path is the prefix of the file names created by | |
| this object. If path is "foo", then the log file will be "foo.gz", and | |
| other auxiliary files will be created and destroyed during the process: | |
| "foo.dict" for a compression dictionary, "foo.temp" for a temporary (next) | |
| dictionary, "foo.add" for data being added or compressed, "foo.lock" for the | |
| lock file, and "foo.repairs" to log recovery operations performed due to | |
| interrupted gzlog operations. A gzlog_open() followed by a gzlog_close() | |
| will recover a previously interrupted operation, if any. */ | |
| gzlog *gzlog_open(char *path); | |
| /* Write to a gzlog object. Return zero on success, -1 if there is a file i/o | |
| error on any of the gzlog files (this should not happen if gzlog_open() | |
| succeeded, unless the device has run out of space or leftover auxiliary | |
| files have permissions or ownership that prevent their use), -2 if there is | |
| a memory allocation failure, or -3 if the log argument is invalid (e.g. if | |
| it was not created by gzlog_open()). This function will write data to the | |
| file uncompressed, until 1 MB has been accumulated, at which time that data | |
| will be compressed. The log file will be a valid gzip file upon successful | |
| return. */ | |
| int gzlog_write(gzlog *log, void *data, size_t len); | |
| /* Force compression of any uncompressed data in the log. This should be used | |
| sparingly, if at all. The main application would be when a log file will | |
| not be appended to again. If this is used to compress frequently while | |
| appending, it will both significantly increase the execution time and | |
| reduce the compression ratio. The return codes are the same as for | |
| gzlog_write(). */ | |
| int gzlog_compress(gzlog *log); | |
| /* Close a gzlog object. Return zero on success, -3 if the log argument is | |
| invalid. The log object is freed, and so cannot be referenced again. */ | |
| int gzlog_close(gzlog *log); | |