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1 /* gzlog.h |
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2 Copyright (C) 2004 Mark Adler, all rights reserved |
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3 version 1.0, 26 Nov 2004 |
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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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24 /* |
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25 The gzlog object allows writing short messages to a gzipped log file, |
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26 opening the log file locked for small bursts, and then closing it. The log |
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27 object works by appending stored data to the gzip file until 1 MB has been |
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28 accumulated. At that time, the stored data is compressed, and replaces the |
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29 uncompressed data in the file. The log file is truncated to its new size at |
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30 that time. After closing, the log file is always valid gzip file that can |
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31 decompressed to recover what was written. |
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32 |
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33 A gzip header "extra" field contains two file offsets for appending. The |
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34 first points to just after the last compressed data. The second points to |
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35 the last stored block in the deflate stream, which is empty. All of the |
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36 data between those pointers is uncompressed. |
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37 */ |
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38 |
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39 /* Open a gzlog object, creating the log file if it does not exist. Return |
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40 NULL on error. Note that gzlog_open() could take a long time to return if |
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41 there is difficulty in locking the file. */ |
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42 void *gzlog_open(char *path); |
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43 |
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44 /* Write to a gzlog object. Return non-zero on error. This function will |
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45 simply write data to the file uncompressed. Compression of the data |
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46 will not occur until gzlog_close() is called. It is expected that |
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47 gzlog_write() is used for a short message, and then gzlog_close() is |
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48 called. If a large amount of data is to be written, then the application |
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49 should write no more than 1 MB at a time with gzlog_write() before |
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50 calling gzlog_close() and then gzlog_open() again. */ |
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51 int gzlog_write(void *log, char *data, size_t len); |
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52 |
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53 /* Close a gzlog object. Return non-zero on error. The log file is locked |
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54 until this function is called. This function will compress stored data |
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55 at the end of the gzip file if at least 1 MB has been accumulated. Note |
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56 that the file will not be a valid gzip file until this function completes. |
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57 */ |
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58 int gzlog_close(void *log); |