[959f7df2] | 1 | /* gzlog.h |
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[21a750bb] | 2 | Copyright (C) 2004, 2008 Mark Adler, all rights reserved |
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| 3 | version 2.0, 25 Apr 2008 |
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[959f7df2] | 4 | |
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| 5 | This software is provided 'as-is', without any express or implied |
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| 6 | warranty. In no event will the author be held liable for any damages |
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| 7 | arising from the use of this software. |
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| 8 | |
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| 9 | Permission is granted to anyone to use this software for any purpose, |
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| 10 | including commercial applications, and to alter it and redistribute it |
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| 11 | freely, subject to the following restrictions: |
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| 12 | |
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| 13 | 1. The origin of this software must not be misrepresented; you must not |
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| 14 | claim that you wrote the original software. If you use this software |
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| 15 | in a product, an acknowledgment in the product documentation would be |
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| 16 | appreciated but is not required. |
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| 17 | 2. Altered source versions must be plainly marked as such, and must not be |
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| 18 | misrepresented as being the original software. |
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| 19 | 3. This notice may not be removed or altered from any source distribution. |
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| 20 | |
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| 21 | Mark Adler madler@alumni.caltech.edu |
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| 22 | */ |
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| 23 | |
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[21a750bb] | 24 | /* Version History: |
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| 25 | 1.0 26 Nov 2004 First version |
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| 26 | 2.0 25 Apr 2008 Complete redesign for recovery of interrupted operations |
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| 27 | Interface changed slightly in that now path is a prefix |
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| 28 | Compression now occurs as needed during gzlog_write() |
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| 29 | gzlog_write() now always leaves the log file as valid gzip |
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| 30 | */ |
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| 31 | |
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[959f7df2] | 32 | /* |
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| 33 | The gzlog object allows writing short messages to a gzipped log file, |
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| 34 | opening the log file locked for small bursts, and then closing it. The log |
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[21a750bb] | 35 | object works by appending stored (uncompressed) data to the gzip file until |
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| 36 | 1 MB has been accumulated. At that time, the stored data is compressed, and |
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| 37 | replaces the uncompressed data in the file. The log file is truncated to |
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| 38 | its new size at that time. After each write operation, the log file is a |
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| 39 | valid gzip file that can decompressed to recover what was written. |
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| 40 | |
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| 41 | The gzlog operations can be interupted at any point due to an application or |
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| 42 | system crash, and the log file will be recovered the next time the log is |
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| 43 | opened with gzlog_open(). |
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[959f7df2] | 44 | */ |
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| 45 | |
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[21a750bb] | 46 | #ifndef GZLOG_H |
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| 47 | #define GZLOG_H |
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| 48 | |
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| 49 | /* gzlog object type */ |
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| 50 | typedef void gzlog; |
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| 51 | |
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[959f7df2] | 52 | /* Open a gzlog object, creating the log file if it does not exist. Return |
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[21a750bb] | 53 | NULL on error. Note that gzlog_open() could take a while to complete if it |
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| 54 | has to wait to verify that a lock is stale (possibly for five minutes), or |
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| 55 | if there is significant contention with other instantiations of this object |
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| 56 | when locking the resource. path is the prefix of the file names created by |
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| 57 | this object. If path is "foo", then the log file will be "foo.gz", and |
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| 58 | other auxiliary files will be created and destroyed during the process: |
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| 59 | "foo.dict" for a compression dictionary, "foo.temp" for a temporary (next) |
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| 60 | dictionary, "foo.add" for data being added or compressed, "foo.lock" for the |
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| 61 | lock file, and "foo.repairs" to log recovery operations performed due to |
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| 62 | interrupted gzlog operations. A gzlog_open() followed by a gzlog_close() |
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| 63 | will recover a previously interrupted operation, if any. */ |
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| 64 | gzlog *gzlog_open(char *path); |
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| 65 | |
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| 66 | /* Write to a gzlog object. Return zero on success, -1 if there is a file i/o |
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| 67 | error on any of the gzlog files (this should not happen if gzlog_open() |
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| 68 | succeeded, unless the device has run out of space or leftover auxiliary |
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| 69 | files have permissions or ownership that prevent their use), -2 if there is |
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| 70 | a memory allocation failure, or -3 if the log argument is invalid (e.g. if |
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| 71 | it was not created by gzlog_open()). This function will write data to the |
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| 72 | file uncompressed, until 1 MB has been accumulated, at which time that data |
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| 73 | will be compressed. The log file will be a valid gzip file upon successful |
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| 74 | return. */ |
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| 75 | int gzlog_write(gzlog *log, void *data, size_t len); |
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| 76 | |
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| 77 | /* Force compression of any uncompressed data in the log. This should be used |
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| 78 | sparingly, if at all. The main application would be when a log file will |
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| 79 | not be appended to again. If this is used to compress frequently while |
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| 80 | appending, it will both significantly increase the execution time and |
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| 81 | reduce the compression ratio. The return codes are the same as for |
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| 82 | gzlog_write(). */ |
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| 83 | int gzlog_compress(gzlog *log); |
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| 84 | |
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| 85 | /* Close a gzlog object. Return zero on success, -3 if the log argument is |
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| 86 | invalid. The log object is freed, and so cannot be referenced again. */ |
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| 87 | int gzlog_close(gzlog *log); |
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| 88 | |
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| 89 | #endif |
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