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/* |
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* gzlog.c |
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* Copyright (C) 2004, 2008, 2012, 2016, 2019 Mark Adler, all rights reserved |
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* For conditions of distribution and use, see copyright notice in gzlog.h |
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* version 2.3, 25 May 2019 |
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*/ |
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/* |
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gzlog provides a mechanism for frequently appending short strings to a gzip |
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file that is efficient both in execution time and compression ratio. The |
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strategy is to write the short strings in an uncompressed form to the end of |
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the gzip file, only compressing when the amount of uncompressed data has |
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reached a given threshold. |
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gzlog also provides protection against interruptions in the process due to |
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system crashes. The status of the operation is recorded in an extra field |
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in the gzip file, and is only updated once the gzip file is brought to a |
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valid state. The last data to be appended or compressed is saved in an |
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auxiliary file, so that if the operation is interrupted, it can be completed |
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the next time an append operation is attempted. |
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gzlog maintains another auxiliary file with the last 32K of data from the |
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compressed portion, which is preloaded for the compression of the subsequent |
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data. This minimizes the impact to the compression ratio of appending. |
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*/ |
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/* |
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Operations Concept: |
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Files (log name "foo"): |
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foo.gz -- gzip file with the complete log |
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foo.add -- last message to append or last data to compress |
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foo.dict -- dictionary of the last 32K of data for next compression |
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foo.temp -- temporary dictionary file for compression after this one |
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foo.lock -- lock file for reading and writing the other files |
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foo.repairs -- log file for log file recovery operations (not compressed) |
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gzip file structure: |
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- fixed-length (no file name) header with extra field (see below) |
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- compressed data ending initially with empty stored block |
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- uncompressed data filling out originally empty stored block and |
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subsequent stored blocks as needed (16K max each) |
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- gzip trailer |
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- no junk at end (no other gzip streams) |
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When appending data, the information in the first three items above plus the |
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foo.add file are sufficient to recover an interrupted append operation. The |
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extra field has the necessary information to restore the start of the last |
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stored block and determine where to append the data in the foo.add file, as |
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well as the crc and length of the gzip data before the append operation. |
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The foo.add file is created before the gzip file is marked for append, and |
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deleted after the gzip file is marked as complete. So if the append |
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operation is interrupted, the data to add will still be there. If due to |
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some external force, the foo.add file gets deleted between when the append |
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operation was interrupted and when recovery is attempted, the gzip file will |
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still be restored, but without the appended data. |
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When compressing data, the information in the first two items above plus the |
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foo.add file are sufficient to recover an interrupted compress operation. |
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The extra field has the necessary information to find the end of the |
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compressed data, and contains both the crc and length of just the compressed |
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data and of the complete set of data including the contents of the foo.add |
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file. |
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Again, the foo.add file is maintained during the compress operation in case |
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of an interruption. If in the unlikely event the foo.add file with the data |
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to be compressed is missing due to some external force, a gzip file with |
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just the previous compressed data will be reconstructed. In this case, all |
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of the data that was to be compressed is lost (approximately one megabyte). |
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This will not occur if all that happened was an interruption of the compress |
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operation. |
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The third state that is marked is the replacement of the old dictionary with |
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the new dictionary after a compress operation. Once compression is |
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complete, the gzip file is marked as being in the replace state. This |
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completes the gzip file, so an interrupt after being so marked does not |
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result in recompression. Then the dictionary file is replaced, and the gzip |
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file is marked as completed. This state prevents the possibility of |
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restarting compression with the wrong dictionary file. |
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All three operations are wrapped by a lock/unlock procedure. In order to |
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gain exclusive access to the log files, first a foo.lock file must be |
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exclusively created. When all operations are complete, the lock is |
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released by deleting the foo.lock file. If when attempting to create the |
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lock file, it already exists and the modify time of the lock file is more |
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than five minutes old (set by the PATIENCE define below), then the old |
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lock file is considered stale and deleted, and the exclusive creation of |
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the lock file is retried. To assure that there are no false assessments |
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of the staleness of the lock file, the operations periodically touch the |
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lock file to update the modified date. |
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Following is the definition of the extra field with all of the information |
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required to enable the above append and compress operations and their |
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recovery if interrupted. Multi-byte values are stored little endian |
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(consistent with the gzip format). File pointers are eight bytes long. |
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The crc's and lengths for the gzip trailer are four bytes long. (Note that |
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the length at the end of a gzip file is used for error checking only, and |
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for large files is actually the length modulo 2^32.) The stored block |
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length is two bytes long. The gzip extra field two-byte identification is |
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"ap" for append. It is assumed that writing the extra field to the file is |
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an "atomic" operation. That is, either all of the extra field is written |
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to the file, or none of it is, if the operation is interrupted right at the |
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point of updating the extra field. This is a reasonable assumption, since |
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the extra field is within the first 52 bytes of the file, which is smaller |
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than any expected block size for a mass storage device (usually 512 bytes or |
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larger). |
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Extra field (35 bytes): |
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- Pointer to first stored block length -- this points to the two-byte length |
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of the first stored block, which is followed by the two-byte, one's |
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complement of that length. The stored block length is preceded by the |
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three-bit header of the stored block, which is the actual start of the |
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stored block in the deflate format. See the bit offset field below. |
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- Pointer to the last stored block length. This is the same as above, but |
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for the last stored block of the uncompressed data in the gzip file. |
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Initially this is the same as the first stored block length pointer. |
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When the stored block gets to 16K (see the MAX_STORE define), then a new |
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stored block as added, at which point the last stored block length pointer |
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is different from the first stored block length pointer. When they are |
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different, the first bit of the last stored block header is eight bits, or |
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one byte back from the block length. |
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- Compressed data crc and length. This is the crc and length of the data |
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that is in the compressed portion of the deflate stream. These are used |
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only in the event that the foo.add file containing the data to compress is |
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lost after a compress operation is interrupted. |
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- Total data crc and length. This is the crc and length of all of the data |
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stored in the gzip file, compressed and uncompressed. It is used to |
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reconstruct the gzip trailer when compressing, as well as when recovering |
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interrupted operations. |
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- Final stored block length. This is used to quickly find where to append, |
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and allows the restoration of the original final stored block state when |
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an append operation is interrupted. |
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- First stored block start as the number of bits back from the final stored |
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block first length byte. This value is in the range of 3..10, and is |
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stored as the low three bits of the final byte of the extra field after |
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subtracting three (0..7). This allows the last-block bit of the stored |
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block header to be updated when a new stored block is added, for the case |
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when the first stored block and the last stored block are the same. (When |
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they are different, the numbers of bits back is known to be eight.) This |
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also allows for new compressed data to be appended to the old compressed |
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data in the compress operation, overwriting the previous first stored |
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block, or for the compressed data to be terminated and a valid gzip file |
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reconstructed on the off chance that a compression operation was |
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interrupted and the data to compress in the foo.add file was deleted. |
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- The operation in process. This is the next two bits in the last byte (the |
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bits under the mask 0x18). The are interpreted as 0: nothing in process, |
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1: append in process, 2: compress in process, 3: replace in process. |
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- The top three bits of the last byte in the extra field are reserved and |
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are currently set to zero. |
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Main procedure: |
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- Exclusively create the foo.lock file using the O_CREAT and O_EXCL modes of |
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the system open() call. If the modify time of an existing lock file is |
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more than PATIENCE seconds old, then the lock file is deleted and the |
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exclusive create is retried. |
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- Load the extra field from the foo.gz file, and see if an operation was in |
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progress but not completed. If so, apply the recovery procedure below. |
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- Perform the append procedure with the provided data. |
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- If the uncompressed data in the foo.gz file is 1MB or more, apply the |
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compress procedure. |
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- Delete the foo.lock file. |
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Append procedure: |
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- Put what to append in the foo.add file so that the operation can be |
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restarted if this procedure is interrupted. |
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- Mark the foo.gz extra field with the append operation in progress. |
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+ Restore the original last-block bit and stored block length of the last |
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stored block from the information in the extra field, in case a previous |
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append operation was interrupted. |
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- Append the provided data to the last stored block, creating new stored |
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blocks as needed and updating the stored blocks last-block bits and |
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lengths. |
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- Update the crc and length with the new data, and write the gzip trailer. |
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- Write over the extra field (with a single write operation) with the new |
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pointers, lengths, and crc's, and mark the gzip file as not in process. |
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Though there is still a foo.add file, it will be ignored since nothing |
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is in process. If a foo.add file is leftover from a previously |
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completed operation, it is truncated when writing new data to it. |
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- Delete the foo.add file. |
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Compress and replace procedures: |
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- Read all of the uncompressed data in the stored blocks in foo.gz and write |
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it to foo.add. Also write foo.temp with the last 32K of that data to |
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provide a dictionary for the next invocation of this procedure. |
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- Rewrite the extra field marking foo.gz with a compression in process. |
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* If there is no data provided to compress (due to a missing foo.add file |
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when recovering), reconstruct and truncate the foo.gz file to contain |
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only the previous compressed data and proceed to the step after the next |
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one. Otherwise ... |
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- Compress the data with the dictionary in foo.dict, and write to the |
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foo.gz file starting at the bit immediately following the last previously |
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compressed block. If there is no foo.dict, proceed anyway with the |
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compression at slightly reduced efficiency. (For the foo.dict file to be |
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missing requires some external failure beyond simply the interruption of |
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a compress operation.) During this process, the foo.lock file is |
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periodically touched to assure that that file is not considered stale by |
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another process before we're done. The deflation is terminated with a |
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non-last empty static block (10 bits long), that is then located and |
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written over by a last-bit-set empty stored block. |
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- Append the crc and length of the data in the gzip file (previously |
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calculated during the append operations). |
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- Write over the extra field with the updated stored block offsets, bits |
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back, crc's, and lengths, and mark foo.gz as in process for a replacement |
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of the dictionary. |
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@ Delete the foo.add file. |
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- Replace foo.dict with foo.temp. |
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- Write over the extra field, marking foo.gz as complete. |
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Recovery procedure: |
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- If not a replace recovery, read in the foo.add file, and provide that data |
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to the appropriate recovery below. If there is no foo.add file, provide |
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a zero data length to the recovery. In that case, the append recovery |
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restores the foo.gz to the previous compressed + uncompressed data state. |
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For the compress recovery, a missing foo.add file results in foo.gz being |
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restored to the previous compressed-only data state. |
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- Append recovery: |
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- Pick up append at + step above |
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- Compress recovery: |
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- Pick up compress at * step above |
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- Replace recovery: |
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- Pick up compress at @ step above |
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- Log the repair with a date stamp in foo.repairs |
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*/ |
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#include <sys/types.h> |
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#include <stdio.h> /* rename, fopen, fprintf, fclose */ |
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#include <stdlib.h> /* malloc, free */ |
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#include <string.h> /* strlen, strrchr, strcpy, strncpy, strcmp */ |
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#include <fcntl.h> /* open */ |
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#include <unistd.h> /* lseek, read, write, close, unlink, sleep, */ |
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/* ftruncate, fsync */ |
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#include <errno.h> /* errno */ |
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#include <time.h> /* time, ctime */ |
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#include <sys/stat.h> /* stat */ |
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#include <sys/time.h> /* utimes */ |
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#include "zlib.h" /* crc32 */ |
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#include "gzlog.h" /* header for external access */ |
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#define local static |
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typedef unsigned int uint; |
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typedef unsigned long ulong; |
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/* Macro for debugging to deterministically force recovery operations */ |
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#ifdef GZLOG_DEBUG |
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#include <setjmp.h> /* longjmp */ |
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jmp_buf gzlog_jump; /* where to go back to */ |
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int gzlog_bail = 0; /* which point to bail at (1..8) */ |
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int gzlog_count = -1; /* number of times through to wait */ |
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# define BAIL(n) do { if (n == gzlog_bail && gzlog_count-- == 0) \ |
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longjmp(gzlog_jump, gzlog_bail); } while (0) |
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#else |
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# define BAIL(n) |
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#endif |
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/* how old the lock file can be in seconds before considering it stale */ |
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#define PATIENCE 300 |
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/* maximum stored block size in Kbytes -- must be in 1..63 */ |
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#define MAX_STORE 16 |
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/* number of stored Kbytes to trigger compression (must be >= 32 to allow |
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dictionary construction, and <= 204 * MAX_STORE, in order for >> 10 to |
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discard the stored block headers contribution of five bytes each) */ |
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#define TRIGGER 1024 |
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/* size of a deflate dictionary (this cannot be changed) */ |
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#define DICT 32768U |
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/* values for the operation (2 bits) */ |
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#define NO_OP 0 |
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#define APPEND_OP 1 |
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#define COMPRESS_OP 2 |
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#define REPLACE_OP 3 |
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/* macros to extract little-endian integers from an unsigned byte buffer */ |
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#define PULL2(p) ((p)[0]+((uint)((p)[1])<<8)) |
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#define PULL4(p) (PULL2(p)+((ulong)PULL2(p+2)<<16)) |
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#define PULL8(p) (PULL4(p)+((off_t)PULL4(p+4)<<32)) |
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/* macros to store integers into a byte buffer in little-endian order */ |
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#define PUT2(p,a) do {(p)[0]=a;(p)[1]=(a)>>8;} while(0) |
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#define PUT4(p,a) do {PUT2(p,a);PUT2(p+2,a>>16);} while(0) |
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#define PUT8(p,a) do {PUT4(p,a);PUT4(p+4,a>>32);} while(0) |
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/* internal structure for log information */ |
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#define LOGID "\106\035\172" /* should be three non-zero characters */ |
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struct log { |
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char id[4]; /* contains LOGID to detect inadvertent overwrites */ |
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int fd; /* file descriptor for .gz file, opened read/write */ |
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char *path; /* allocated path, e.g. "/var/log/foo" or "foo" */ |
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char *end; /* end of path, for appending suffices such as ".gz" */ |
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off_t first; /* offset of first stored block first length byte */ |
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int back; /* location of first block id in bits back from first */ |
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uint stored; /* bytes currently in last stored block */ |
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off_t last; /* offset of last stored block first length byte */ |
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ulong ccrc; /* crc of compressed data */ |
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ulong clen; /* length (modulo 2^32) of compressed data */ |
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ulong tcrc; /* crc of total data */ |
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ulong tlen; /* length (modulo 2^32) of total data */ |
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time_t lock; /* last modify time of our lock file */ |
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}; |
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/* gzip header for gzlog */ |
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local unsigned char log_gzhead[] = { |
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0x1f, 0x8b, /* magic gzip id */ |
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8, /* compression method is deflate */ |
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4, /* there is an extra field (no file name) */ |
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0, 0, 0, 0, /* no modification time provided */ |
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0, 0xff, /* no extra flags, no OS specified */ |
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39, 0, 'a', 'p', 35, 0 /* extra field with "ap" subfield */ |
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/* 35 is EXTRA, 39 is EXTRA + 4 */ |
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}; |
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#define HEAD sizeof(log_gzhead) /* should be 16 */ |
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/* initial gzip extra field content (52 == HEAD + EXTRA + 1) */ |
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local unsigned char log_gzext[] = { |
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52, 0, 0, 0, 0, 0, 0, 0, /* offset of first stored block length */ |
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52, 0, 0, 0, 0, 0, 0, 0, /* offset of last stored block length */ |
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0, 0, 0, 0, 0, 0, 0, 0, /* compressed data crc and length */ |
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0, 0, 0, 0, 0, 0, 0, 0, /* total data crc and length */ |
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0, 0, /* final stored block data length */ |
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5 /* op is NO_OP, last bit 8 bits back */ |
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}; |
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#define EXTRA sizeof(log_gzext) /* should be 35 */ |
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/* initial gzip data and trailer */ |
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local unsigned char log_gzbody[] = { |
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1, 0, 0, 0xff, 0xff, /* empty stored block (last) */ |
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0, 0, 0, 0, /* crc */ |
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0, 0, 0, 0 /* uncompressed length */ |
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}; |
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#define BODY sizeof(log_gzbody) |
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/* Exclusively create foo.lock in order to negotiate exclusive access to the |
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foo.* files. If the modify time of an existing lock file is greater than |
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PATIENCE seconds in the past, then consider the lock file to have been |
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342
|
abandoned, delete it, and try the exclusive create again. Save the lock |
|
343
|
file modify time for verification of ownership. Return 0 on success, or -1 |
|
344
|
on failure, usually due to an access restriction or invalid path. Note that |
|
345
|
if stat() or unlink() fails, it may be due to another process noticing the |
|
346
|
abandoned lock file a smidge sooner and deleting it, so those are not |
|
347
|
flagged as an error. */ |
|
348
|
local int log_lock(struct log *log) |
|
349
|
{ |
|
350
|
int fd; |
|
351
|
struct stat st; |
|
352
|
|
|
353
|
strcpy(log->end, ".lock"); |
|
354
|
while ((fd = open(log->path, O_CREAT | O_EXCL, 0644)) < 0) { |
|
355
|
if (errno != EEXIST) |
|
356
|
return -1; |
|
357
|
if (stat(log->path, &st) == 0 && time(NULL) - st.st_mtime > PATIENCE) { |
|
358
|
unlink(log->path); |
|
359
|
continue; |
|
360
|
} |
|
361
|
sleep(2); /* relinquish the CPU for two seconds while waiting */ |
|
362
|
} |
|
363
|
close(fd); |
|
364
|
if (stat(log->path, &st) == 0) |
|
365
|
log->lock = st.st_mtime; |
|
366
|
return 0; |
|
367
|
} |
|
368
|
|
|
369
|
/* Update the modify time of the lock file to now, in order to prevent another |
|
370
|
task from thinking that the lock is stale. Save the lock file modify time |
|
371
|
for verification of ownership. */ |
|
372
|
local void log_touch(struct log *log) |
|
373
|
{ |
|
374
|
struct stat st; |
|
375
|
|
|
376
|
strcpy(log->end, ".lock"); |
|
377
|
utimes(log->path, NULL); |
|
378
|
if (stat(log->path, &st) == 0) |
|
379
|
log->lock = st.st_mtime; |
|
380
|
} |
|
381
|
|
|
382
|
/* Check the log file modify time against what is expected. Return true if |
|
383
|
this is not our lock. If it is our lock, touch it to keep it. */ |
|
384
|
local int log_check(struct log *log) |
|
385
|
{ |
|
386
|
struct stat st; |
|
387
|
|
|
388
|
strcpy(log->end, ".lock"); |
|
389
|
if (stat(log->path, &st) || st.st_mtime != log->lock) |
|
390
|
return 1; |
|
391
|
log_touch(log); |
|
392
|
return 0; |
|
393
|
} |
|
394
|
|
|
395
|
/* Unlock a previously acquired lock, but only if it's ours. */ |
|
396
|
local void log_unlock(struct log *log) |
|
397
|
{ |
|
398
|
if (log_check(log)) |
|
399
|
return; |
|
400
|
strcpy(log->end, ".lock"); |
|
401
|
unlink(log->path); |
|
402
|
log->lock = 0; |
|
403
|
} |
|
404
|
|
|
405
|
/* Check the gzip header and read in the extra field, filling in the values in |
|
406
|
the log structure. Return op on success or -1 if the gzip header was not as |
|
407
|
expected. op is the current operation in progress last written to the extra |
|
408
|
field. This assumes that the gzip file has already been opened, with the |
|
409
|
file descriptor log->fd. */ |
|
410
|
local int log_head(struct log *log) |
|
411
|
{ |
|
412
|
int op; |
|
413
|
unsigned char buf[HEAD + EXTRA]; |
|
414
|
|
|
415
|
if (lseek(log->fd, 0, SEEK_SET) < 0 || |
|
416
|
read(log->fd, buf, HEAD + EXTRA) != HEAD + EXTRA || |
|
417
|
memcmp(buf, log_gzhead, HEAD)) { |
|
418
|
return -1; |
|
419
|
} |
|
420
|
log->first = PULL8(buf + HEAD); |
|
421
|
log->last = PULL8(buf + HEAD + 8); |
|
422
|
log->ccrc = PULL4(buf + HEAD + 16); |
|
423
|
log->clen = PULL4(buf + HEAD + 20); |
|
424
|
log->tcrc = PULL4(buf + HEAD + 24); |
|
425
|
log->tlen = PULL4(buf + HEAD + 28); |
|
426
|
log->stored = PULL2(buf + HEAD + 32); |
|
427
|
log->back = 3 + (buf[HEAD + 34] & 7); |
|
428
|
op = (buf[HEAD + 34] >> 3) & 3; |
|
429
|
return op; |
|
430
|
} |
|
431
|
|
|
432
|
/* Write over the extra field contents, marking the operation as op. Use fsync |
|
433
|
to assure that the device is written to, and in the requested order. This |
|
434
|
operation, and only this operation, is assumed to be atomic in order to |
|
435
|
assure that the log is recoverable in the event of an interruption at any |
|
436
|
point in the process. Return -1 if the write to foo.gz failed. */ |
|
437
|
local int log_mark(struct log *log, int op) |
|
438
|
{ |
|
439
|
int ret; |
|
440
|
unsigned char ext[EXTRA]; |
|
441
|
|
|
442
|
PUT8(ext, log->first); |
|
443
|
PUT8(ext + 8, log->last); |
|
444
|
PUT4(ext + 16, log->ccrc); |
|
445
|
PUT4(ext + 20, log->clen); |
|
446
|
PUT4(ext + 24, log->tcrc); |
|
447
|
PUT4(ext + 28, log->tlen); |
|
448
|
PUT2(ext + 32, log->stored); |
|
449
|
ext[34] = log->back - 3 + (op << 3); |
|
450
|
fsync(log->fd); |
|
451
|
ret = lseek(log->fd, HEAD, SEEK_SET) < 0 || |
|
452
|
write(log->fd, ext, EXTRA) != EXTRA ? -1 : 0; |
|
453
|
fsync(log->fd); |
|
454
|
return ret; |
|
455
|
} |
|
456
|
|
|
457
|
/* Rewrite the last block header bits and subsequent zero bits to get to a byte |
|
458
|
boundary, setting the last block bit if last is true, and then write the |
|
459
|
remainder of the stored block header (length and one's complement). Leave |
|
460
|
the file pointer after the end of the last stored block data. Return -1 if |
|
461
|
there is a read or write failure on the foo.gz file */ |
|
462
|
local int log_last(struct log *log, int last) |
|
463
|
{ |
|
464
|
int back, len, mask; |
|
465
|
unsigned char buf[6]; |
|
466
|
|
|
467
|
/* determine the locations of the bytes and bits to modify */ |
|
468
|
back = log->last == log->first ? log->back : 8; |
|
469
|
len = back > 8 ? 2 : 1; /* bytes back from log->last */ |
|
470
|
mask = 0x80 >> ((back - 1) & 7); /* mask for block last-bit */ |
|
471
|
|
|
472
|
/* get the byte to modify (one or two back) into buf[0] -- don't need to |
|
473
|
read the byte if the last-bit is eight bits back, since in that case |
|
474
|
the entire byte will be modified */ |
|
475
|
buf[0] = 0; |
|
476
|
if (back != 8 && (lseek(log->fd, log->last - len, SEEK_SET) < 0 || |
|
477
|
read(log->fd, buf, 1) != 1)) |
|
478
|
return -1; |
|
479
|
|
|
480
|
/* change the last-bit of the last stored block as requested -- note |
|
481
|
that all bits above the last-bit are set to zero, per the type bits |
|
482
|
of a stored block being 00 and per the convention that the bits to |
|
483
|
bring the stream to a byte boundary are also zeros */ |
|
484
|
buf[1] = 0; |
|
485
|
buf[2 - len] = (*buf & (mask - 1)) + (last ? mask : 0); |
|
486
|
|
|
487
|
/* write the modified stored block header and lengths, move the file |
|
488
|
pointer to after the last stored block data */ |
|
489
|
PUT2(buf + 2, log->stored); |
|
490
|
PUT2(buf + 4, log->stored ^ 0xffff); |
|
491
|
return lseek(log->fd, log->last - len, SEEK_SET) < 0 || |
|
492
|
write(log->fd, buf + 2 - len, len + 4) != len + 4 || |
|
493
|
lseek(log->fd, log->stored, SEEK_CUR) < 0 ? -1 : 0; |
|
494
|
} |
|
495
|
|
|
496
|
/* Append len bytes from data to the locked and open log file. len may be zero |
|
497
|
if recovering and no .add file was found. In that case, the previous state |
|
498
|
of the foo.gz file is restored. The data is appended uncompressed in |
|
499
|
deflate stored blocks. Return -1 if there was an error reading or writing |
|
500
|
the foo.gz file. */ |
|
501
|
local int log_append(struct log *log, unsigned char *data, size_t len) |
|
502
|
{ |
|
503
|
uint put; |
|
504
|
off_t end; |
|
505
|
unsigned char buf[8]; |
|
506
|
|
|
507
|
/* set the last block last-bit and length, in case recovering an |
|
508
|
interrupted append, then position the file pointer to append to the |
|
509
|
block */ |
|
510
|
if (log_last(log, 1)) |
|
511
|
return -1; |
|
512
|
|
|
513
|
/* append, adding stored blocks and updating the offset of the last stored |
|
514
|
block as needed, and update the total crc and length */ |
|
515
|
while (len) { |
|
516
|
/* append as much as we can to the last block */ |
|
517
|
put = (MAX_STORE << 10) - log->stored; |
|
518
|
if (put > len) |
|
519
|
put = (uint)len; |
|
520
|
if (put) { |
|
521
|
if (write(log->fd, data, put) != put) |
|
522
|
return -1; |
|
523
|
BAIL(1); |
|
524
|
log->tcrc = crc32(log->tcrc, data, put); |
|
525
|
log->tlen += put; |
|
526
|
log->stored += put; |
|
527
|
data += put; |
|
528
|
len -= put; |
|
529
|
} |
|
530
|
|
|
531
|
/* if we need to, add a new empty stored block */ |
|
532
|
if (len) { |
|
533
|
/* mark current block as not last */ |
|
534
|
if (log_last(log, 0)) |
|
535
|
return -1; |
|
536
|
|
|
537
|
/* point to new, empty stored block */ |
|
538
|
log->last += 4 + log->stored + 1; |
|
539
|
log->stored = 0; |
|
540
|
} |
|
541
|
|
|
542
|
/* mark last block as last, update its length */ |
|
543
|
if (log_last(log, 1)) |
|
544
|
return -1; |
|
545
|
BAIL(2); |
|
546
|
} |
|
547
|
|
|
548
|
/* write the new crc and length trailer, and truncate just in case (could |
|
549
|
be recovering from partial append with a missing foo.add file) */ |
|
550
|
PUT4(buf, log->tcrc); |
|
551
|
PUT4(buf + 4, log->tlen); |
|
552
|
if (write(log->fd, buf, 8) != 8 || |
|
553
|
(end = lseek(log->fd, 0, SEEK_CUR)) < 0 || ftruncate(log->fd, end)) |
|
554
|
return -1; |
|
555
|
|
|
556
|
/* write the extra field, marking the log file as done, delete .add file */ |
|
557
|
if (log_mark(log, NO_OP)) |
|
558
|
return -1; |
|
559
|
strcpy(log->end, ".add"); |
|
560
|
unlink(log->path); /* ignore error, since may not exist */ |
|
561
|
return 0; |
|
562
|
} |
|
563
|
|
|
564
|
/* Replace the foo.dict file with the foo.temp file. Also delete the foo.add |
|
565
|
file, since the compress operation may have been interrupted before that was |
|
566
|
done. Returns 1 if memory could not be allocated, or -1 if reading or |
|
567
|
writing foo.gz fails, or if the rename fails for some reason other than |
|
568
|
foo.temp not existing. foo.temp not existing is a permitted error, since |
|
569
|
the replace operation may have been interrupted after the rename is done, |
|
570
|
but before foo.gz is marked as complete. */ |
|
571
|
local int log_replace(struct log *log) |
|
572
|
{ |
|
573
|
int ret; |
|
574
|
char *dest; |
|
575
|
|
|
576
|
/* delete foo.add file */ |
|
577
|
strcpy(log->end, ".add"); |
|
578
|
unlink(log->path); /* ignore error, since may not exist */ |
|
579
|
BAIL(3); |
|
580
|
|
|
581
|
/* rename foo.name to foo.dict, replacing foo.dict if it exists */ |
|
582
|
strcpy(log->end, ".dict"); |
|
583
|
dest = malloc(strlen(log->path) + 1); |
|
584
|
if (dest == NULL) |
|
585
|
return -2; |
|
586
|
strcpy(dest, log->path); |
|
587
|
strcpy(log->end, ".temp"); |
|
588
|
ret = rename(log->path, dest); |
|
589
|
free(dest); |
|
590
|
if (ret && errno != ENOENT) |
|
591
|
return -1; |
|
592
|
BAIL(4); |
|
593
|
|
|
594
|
/* mark the foo.gz file as done */ |
|
595
|
return log_mark(log, NO_OP); |
|
596
|
} |
|
597
|
|
|
598
|
/* Compress the len bytes at data and append the compressed data to the |
|
599
|
foo.gz deflate data immediately after the previous compressed data. This |
|
600
|
overwrites the previous uncompressed data, which was stored in foo.add |
|
601
|
and is the data provided in data[0..len-1]. If this operation is |
|
602
|
interrupted, it picks up at the start of this routine, with the foo.add |
|
603
|
file read in again. If there is no data to compress (len == 0), then we |
|
604
|
simply terminate the foo.gz file after the previously compressed data, |
|
605
|
appending a final empty stored block and the gzip trailer. Return -1 if |
|
606
|
reading or writing the log.gz file failed, or -2 if there was a memory |
|
607
|
allocation failure. */ |
|
608
|
local int log_compress(struct log *log, unsigned char *data, size_t len) |
|
609
|
{ |
|
610
|
int fd; |
|
611
|
uint got, max; |
|
612
|
ssize_t dict; |
|
613
|
off_t end; |
|
614
|
z_stream strm; |
|
615
|
unsigned char buf[DICT]; |
|
616
|
|
|
617
|
/* compress and append compressed data */ |
|
618
|
if (len) { |
|
619
|
/* set up for deflate, allocating memory */ |
|
620
|
strm.zalloc = Z_NULL; |
|
621
|
strm.zfree = Z_NULL; |
|
622
|
strm.opaque = Z_NULL; |
|
623
|
if (deflateInit2(&strm, Z_DEFAULT_COMPRESSION, Z_DEFLATED, -15, 8, |
|
624
|
Z_DEFAULT_STRATEGY) != Z_OK) |
|
625
|
return -2; |
|
626
|
|
|
627
|
/* read in dictionary (last 32K of data that was compressed) */ |
|
628
|
strcpy(log->end, ".dict"); |
|
629
|
fd = open(log->path, O_RDONLY, 0); |
|
630
|
if (fd >= 0) { |
|
631
|
dict = read(fd, buf, DICT); |
|
632
|
close(fd); |
|
633
|
if (dict < 0) { |
|
634
|
deflateEnd(&strm); |
|
635
|
return -1; |
|
636
|
} |
|
637
|
if (dict) |
|
638
|
deflateSetDictionary(&strm, buf, (uint)dict); |
|
639
|
} |
|
640
|
log_touch(log); |
|
641
|
|
|
642
|
/* prime deflate with last bits of previous block, position write |
|
643
|
pointer to write those bits and overwrite what follows */ |
|
644
|
if (lseek(log->fd, log->first - (log->back > 8 ? 2 : 1), |
|
645
|
SEEK_SET) < 0 || |
|
646
|
read(log->fd, buf, 1) != 1 || lseek(log->fd, -1, SEEK_CUR) < 0) { |
|
647
|
deflateEnd(&strm); |
|
648
|
return -1; |
|
649
|
} |
|
650
|
deflatePrime(&strm, (8 - log->back) & 7, *buf); |
|
651
|
|
|
652
|
/* compress, finishing with a partial non-last empty static block */ |
|
653
|
strm.next_in = data; |
|
654
|
max = (((uint)0 - 1) >> 1) + 1; /* in case int smaller than size_t */ |
|
655
|
do { |
|
656
|
strm.avail_in = len > max ? max : (uint)len; |
|
657
|
len -= strm.avail_in; |
|
658
|
do { |
|
659
|
strm.avail_out = DICT; |
|
660
|
strm.next_out = buf; |
|
661
|
deflate(&strm, len ? Z_NO_FLUSH : Z_PARTIAL_FLUSH); |
|
662
|
got = DICT - strm.avail_out; |
|
663
|
if (got && write(log->fd, buf, got) != got) { |
|
664
|
deflateEnd(&strm); |
|
665
|
return -1; |
|
666
|
} |
|
667
|
log_touch(log); |
|
668
|
} while (strm.avail_out == 0); |
|
669
|
} while (len); |
|
670
|
deflateEnd(&strm); |
|
671
|
BAIL(5); |
|
672
|
|
|
673
|
/* find start of empty static block -- scanning backwards the first one |
|
674
|
bit is the second bit of the block, if the last byte is zero, then |
|
675
|
we know the byte before that has a one in the top bit, since an |
|
676
|
empty static block is ten bits long */ |
|
677
|
if ((log->first = lseek(log->fd, -1, SEEK_CUR)) < 0 || |
|
678
|
read(log->fd, buf, 1) != 1) |
|
679
|
return -1; |
|
680
|
log->first++; |
|
681
|
if (*buf) { |
|
682
|
log->back = 1; |
|
683
|
while ((*buf & ((uint)1 << (8 - log->back++))) == 0) |
|
684
|
; /* guaranteed to terminate, since *buf != 0 */ |
|
685
|
} |
|
686
|
else |
|
687
|
log->back = 10; |
|
688
|
|
|
689
|
/* update compressed crc and length */ |
|
690
|
log->ccrc = log->tcrc; |
|
691
|
log->clen = log->tlen; |
|
692
|
} |
|
693
|
else { |
|
694
|
/* no data to compress -- fix up existing gzip stream */ |
|
695
|
log->tcrc = log->ccrc; |
|
696
|
log->tlen = log->clen; |
|
697
|
} |
|
698
|
|
|
699
|
/* complete and truncate gzip stream */ |
|
700
|
log->last = log->first; |
|
701
|
log->stored = 0; |
|
702
|
PUT4(buf, log->tcrc); |
|
703
|
PUT4(buf + 4, log->tlen); |
|
704
|
if (log_last(log, 1) || write(log->fd, buf, 8) != 8 || |
|
705
|
(end = lseek(log->fd, 0, SEEK_CUR)) < 0 || ftruncate(log->fd, end)) |
|
706
|
return -1; |
|
707
|
BAIL(6); |
|
708
|
|
|
709
|
/* mark as being in the replace operation */ |
|
710
|
if (log_mark(log, REPLACE_OP)) |
|
711
|
return -1; |
|
712
|
|
|
713
|
/* execute the replace operation and mark the file as done */ |
|
714
|
return log_replace(log); |
|
715
|
} |
|
716
|
|
|
717
|
/* log a repair record to the .repairs file */ |
|
718
|
local void log_log(struct log *log, int op, char *record) |
|
719
|
{ |
|
720
|
time_t now; |
|
721
|
FILE *rec; |
|
722
|
|
|
723
|
now = time(NULL); |
|
724
|
strcpy(log->end, ".repairs"); |
|
725
|
rec = fopen(log->path, "a"); |
|
726
|
if (rec == NULL) |
|
727
|
return; |
|
728
|
fprintf(rec, "%.24s %s recovery: %s\n", ctime(&now), op == APPEND_OP ? |
|
729
|
"append" : (op == COMPRESS_OP ? "compress" : "replace"), record); |
|
730
|
fclose(rec); |
|
731
|
return; |
|
732
|
} |
|
733
|
|
|
734
|
/* Recover the interrupted operation op. First read foo.add for recovering an |
|
735
|
append or compress operation. Return -1 if there was an error reading or |
|
736
|
writing foo.gz or reading an existing foo.add, or -2 if there was a memory |
|
737
|
allocation failure. */ |
|
738
|
local int log_recover(struct log *log, int op) |
|
739
|
{ |
|
740
|
int fd, ret = 0; |
|
741
|
unsigned char *data = NULL; |
|
742
|
size_t len = 0; |
|
743
|
struct stat st; |
|
744
|
|
|
745
|
/* log recovery */ |
|
746
|
log_log(log, op, "start"); |
|
747
|
|
|
748
|
/* load foo.add file if expected and present */ |
|
749
|
if (op == APPEND_OP || op == COMPRESS_OP) { |
|
750
|
strcpy(log->end, ".add"); |
|
751
|
if (stat(log->path, &st) == 0 && st.st_size) { |
|
752
|
len = (size_t)(st.st_size); |
|
753
|
if ((off_t)len != st.st_size || |
|
754
|
(data = malloc(st.st_size)) == NULL) { |
|
755
|
log_log(log, op, "allocation failure"); |
|
756
|
return -2; |
|
757
|
} |
|
758
|
if ((fd = open(log->path, O_RDONLY, 0)) < 0) { |
|
759
|
free(data); |
|
760
|
log_log(log, op, ".add file read failure"); |
|
761
|
return -1; |
|
762
|
} |
|
763
|
ret = (size_t)read(fd, data, len) != len; |
|
764
|
close(fd); |
|
765
|
if (ret) { |
|
766
|
free(data); |
|
767
|
log_log(log, op, ".add file read failure"); |
|
768
|
return -1; |
|
769
|
} |
|
770
|
log_log(log, op, "loaded .add file"); |
|
771
|
} |
|
772
|
else |
|
773
|
log_log(log, op, "missing .add file!"); |
|
774
|
} |
|
775
|
|
|
776
|
/* recover the interrupted operation */ |
|
777
|
switch (op) { |
|
778
|
case APPEND_OP: |
|
779
|
ret = log_append(log, data, len); |
|
780
|
break; |
|
781
|
case COMPRESS_OP: |
|
782
|
ret = log_compress(log, data, len); |
|
783
|
break; |
|
784
|
case REPLACE_OP: |
|
785
|
ret = log_replace(log); |
|
786
|
} |
|
787
|
|
|
788
|
/* log status */ |
|
789
|
log_log(log, op, ret ? "failure" : "complete"); |
|
790
|
|
|
791
|
/* clean up */ |
|
792
|
if (data != NULL) |
|
793
|
free(data); |
|
794
|
return ret; |
|
795
|
} |
|
796
|
|
|
797
|
/* Close the foo.gz file (if open) and release the lock. */ |
|
798
|
local void log_close(struct log *log) |
|
799
|
{ |
|
800
|
if (log->fd >= 0) |
|
801
|
close(log->fd); |
|
802
|
log->fd = -1; |
|
803
|
log_unlock(log); |
|
804
|
} |
|
805
|
|
|
806
|
/* Open foo.gz, verify the header, and load the extra field contents, after |
|
807
|
first creating the foo.lock file to gain exclusive access to the foo.* |
|
808
|
files. If foo.gz does not exist or is empty, then write the initial header, |
|
809
|
extra, and body content of an empty foo.gz log file. If there is an error |
|
810
|
creating the lock file due to access restrictions, or an error reading or |
|
811
|
writing the foo.gz file, or if the foo.gz file is not a proper log file for |
|
812
|
this object (e.g. not a gzip file or does not contain the expected extra |
|
813
|
field), then return true. If there is an error, the lock is released. |
|
814
|
Otherwise, the lock is left in place. */ |
|
815
|
local int log_open(struct log *log) |
|
816
|
{ |
|
817
|
int op; |
|
818
|
|
|
819
|
/* release open file resource if left over -- can occur if lock lost |
|
820
|
between gzlog_open() and gzlog_write() */ |
|
821
|
if (log->fd >= 0) |
|
822
|
close(log->fd); |
|
823
|
log->fd = -1; |
|
824
|
|
|
825
|
/* negotiate exclusive access */ |
|
826
|
if (log_lock(log) < 0) |
|
827
|
return -1; |
|
828
|
|
|
829
|
/* open the log file, foo.gz */ |
|
830
|
strcpy(log->end, ".gz"); |
|
831
|
log->fd = open(log->path, O_RDWR | O_CREAT, 0644); |
|
832
|
if (log->fd < 0) { |
|
833
|
log_close(log); |
|
834
|
return -1; |
|
835
|
} |
|
836
|
|
|
837
|
/* if new, initialize foo.gz with an empty log, delete old dictionary */ |
|
838
|
if (lseek(log->fd, 0, SEEK_END) == 0) { |
|
839
|
if (write(log->fd, log_gzhead, HEAD) != HEAD || |
|
840
|
write(log->fd, log_gzext, EXTRA) != EXTRA || |
|
841
|
write(log->fd, log_gzbody, BODY) != BODY) { |
|
842
|
log_close(log); |
|
843
|
return -1; |
|
844
|
} |
|
845
|
strcpy(log->end, ".dict"); |
|
846
|
unlink(log->path); |
|
847
|
} |
|
848
|
|
|
849
|
/* verify log file and load extra field information */ |
|
850
|
if ((op = log_head(log)) < 0) { |
|
851
|
log_close(log); |
|
852
|
return -1; |
|
853
|
} |
|
854
|
|
|
855
|
/* check for interrupted process and if so, recover */ |
|
856
|
if (op != NO_OP && log_recover(log, op)) { |
|
857
|
log_close(log); |
|
858
|
return -1; |
|
859
|
} |
|
860
|
|
|
861
|
/* touch the lock file to prevent another process from grabbing it */ |
|
862
|
log_touch(log); |
|
863
|
return 0; |
|
864
|
} |
|
865
|
|
|
866
|
/* See gzlog.h for the description of the external methods below */ |
|
867
|
gzlog *gzlog_open(char *path) |
|
868
|
{ |
|
869
|
size_t n; |
|
870
|
struct log *log; |
|
871
|
|
|
872
|
/* check arguments */ |
|
873
|
if (path == NULL || *path == 0) |
|
874
|
return NULL; |
|
875
|
|
|
876
|
/* allocate and initialize log structure */ |
|
877
|
log = malloc(sizeof(struct log)); |
|
878
|
if (log == NULL) |
|
879
|
return NULL; |
|
880
|
strcpy(log->id, LOGID); |
|
881
|
log->fd = -1; |
|
882
|
|
|
883
|
/* save path and end of path for name construction */ |
|
884
|
n = strlen(path); |
|
885
|
log->path = malloc(n + 9); /* allow for ".repairs" */ |
|
886
|
if (log->path == NULL) { |
|
887
|
free(log); |
|
888
|
return NULL; |
|
889
|
} |
|
890
|
strcpy(log->path, path); |
|
891
|
log->end = log->path + n; |
|
892
|
|
|
893
|
/* gain exclusive access and verify log file -- may perform a |
|
894
|
recovery operation if needed */ |
|
895
|
if (log_open(log)) { |
|
896
|
free(log->path); |
|
897
|
free(log); |
|
898
|
return NULL; |
|
899
|
} |
|
900
|
|
|
901
|
/* return pointer to log structure */ |
|
902
|
return log; |
|
903
|
} |
|
904
|
|
|
905
|
/* gzlog_compress() return values: |
|
906
|
0: all good |
|
907
|
-1: file i/o error (usually access issue) |
|
908
|
-2: memory allocation failure |
|
909
|
-3: invalid log pointer argument */ |
|
910
|
int gzlog_compress(gzlog *logd) |
|
911
|
{ |
|
912
|
int fd, ret; |
|
913
|
uint block; |
|
914
|
size_t len, next; |
|
915
|
unsigned char *data, buf[5]; |
|
916
|
struct log *log = logd; |
|
917
|
|
|
918
|
/* check arguments */ |
|
919
|
if (log == NULL || strcmp(log->id, LOGID)) |
|
920
|
return -3; |
|
921
|
|
|
922
|
/* see if we lost the lock -- if so get it again and reload the extra |
|
923
|
field information (it probably changed), recover last operation if |
|
924
|
necessary */ |
|
925
|
if (log_check(log) && log_open(log)) |
|
926
|
return -1; |
|
927
|
|
|
928
|
/* create space for uncompressed data */ |
|
929
|
len = ((size_t)(log->last - log->first) & ~(((size_t)1 << 10) - 1)) + |
|
930
|
log->stored; |
|
931
|
if ((data = malloc(len)) == NULL) |
|
932
|
return -2; |
|
933
|
|
|
934
|
/* do statement here is just a cheap trick for error handling */ |
|
935
|
do { |
|
936
|
/* read in the uncompressed data */ |
|
937
|
if (lseek(log->fd, log->first - 1, SEEK_SET) < 0) |
|
938
|
break; |
|
939
|
next = 0; |
|
940
|
while (next < len) { |
|
941
|
if (read(log->fd, buf, 5) != 5) |
|
942
|
break; |
|
943
|
block = PULL2(buf + 1); |
|
944
|
if (next + block > len || |
|
945
|
read(log->fd, (char *)data + next, block) != block) |
|
946
|
break; |
|
947
|
next += block; |
|
948
|
} |
|
949
|
if (lseek(log->fd, 0, SEEK_CUR) != log->last + 4 + log->stored) |
|
950
|
break; |
|
951
|
log_touch(log); |
|
952
|
|
|
953
|
/* write the uncompressed data to the .add file */ |
|
954
|
strcpy(log->end, ".add"); |
|
955
|
fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644); |
|
956
|
if (fd < 0) |
|
957
|
break; |
|
958
|
ret = (size_t)write(fd, data, len) != len; |
|
959
|
if (ret | close(fd)) |
|
960
|
break; |
|
961
|
log_touch(log); |
|
962
|
|
|
963
|
/* write the dictionary for the next compress to the .temp file */ |
|
964
|
strcpy(log->end, ".temp"); |
|
965
|
fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644); |
|
966
|
if (fd < 0) |
|
967
|
break; |
|
968
|
next = DICT > len ? len : DICT; |
|
969
|
ret = (size_t)write(fd, (char *)data + len - next, next) != next; |
|
970
|
if (ret | close(fd)) |
|
971
|
break; |
|
972
|
log_touch(log); |
|
973
|
|
|
974
|
/* roll back to compressed data, mark the compress in progress */ |
|
975
|
log->last = log->first; |
|
976
|
log->stored = 0; |
|
977
|
if (log_mark(log, COMPRESS_OP)) |
|
978
|
break; |
|
979
|
BAIL(7); |
|
980
|
|
|
981
|
/* compress and append the data (clears mark) */ |
|
982
|
ret = log_compress(log, data, len); |
|
983
|
free(data); |
|
984
|
return ret; |
|
985
|
} while (0); |
|
986
|
|
|
987
|
/* broke out of do above on i/o error */ |
|
988
|
free(data); |
|
989
|
return -1; |
|
990
|
} |
|
991
|
|
|
992
|
/* gzlog_write() return values: |
|
993
|
0: all good |
|
994
|
-1: file i/o error (usually access issue) |
|
995
|
-2: memory allocation failure |
|
996
|
-3: invalid log pointer argument */ |
|
997
|
int gzlog_write(gzlog *logd, void *data, size_t len) |
|
998
|
{ |
|
999
|
int fd, ret; |
|
1000
|
struct log *log = logd; |
|
1001
|
|
|
1002
|
/* check arguments */ |
|
1003
|
if (log == NULL || strcmp(log->id, LOGID)) |
|
1004
|
return -3; |
|
1005
|
if (data == NULL || len <= 0) |
|
1006
|
return 0; |
|
1007
|
|
|
1008
|
/* see if we lost the lock -- if so get it again and reload the extra |
|
1009
|
field information (it probably changed), recover last operation if |
|
1010
|
necessary */ |
|
1011
|
if (log_check(log) && log_open(log)) |
|
1012
|
return -1; |
|
1013
|
|
|
1014
|
/* create and write .add file */ |
|
1015
|
strcpy(log->end, ".add"); |
|
1016
|
fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644); |
|
1017
|
if (fd < 0) |
|
1018
|
return -1; |
|
1019
|
ret = (size_t)write(fd, data, len) != len; |
|
1020
|
if (ret | close(fd)) |
|
1021
|
return -1; |
|
1022
|
log_touch(log); |
|
1023
|
|
|
1024
|
/* mark log file with append in progress */ |
|
1025
|
if (log_mark(log, APPEND_OP)) |
|
1026
|
return -1; |
|
1027
|
BAIL(8); |
|
1028
|
|
|
1029
|
/* append data (clears mark) */ |
|
1030
|
if (log_append(log, data, len)) |
|
1031
|
return -1; |
|
1032
|
|
|
1033
|
/* check to see if it's time to compress -- if not, then done */ |
|
1034
|
if (((log->last - log->first) >> 10) + (log->stored >> 10) < TRIGGER) |
|
1035
|
return 0; |
|
1036
|
|
|
1037
|
/* time to compress */ |
|
1038
|
return gzlog_compress(log); |
|
1039
|
} |
|
1040
|
|
|
1041
|
/* gzlog_close() return values: |
|
1042
|
0: ok |
|
1043
|
-3: invalid log pointer argument */ |
|
1044
|
int gzlog_close(gzlog *logd) |
|
1045
|
{ |
|
1046
|
struct log *log = logd; |
|
1047
|
|
|
1048
|
/* check arguments */ |
|
1049
|
if (log == NULL || strcmp(log->id, LOGID)) |
|
1050
|
return -3; |
|
1051
|
|
|
1052
|
/* close the log file and release the lock */ |
|
1053
|
log_close(log); |
|
1054
|
|
|
1055
|
/* free structure and return */ |
|
1056
|
if (log->path != NULL) |
|
1057
|
free(log->path); |
|
1058
|
strcpy(log->id, "bad"); |
|
1059
|
free(log); |
|
1060
|
return 0; |
|
1061
|
} |
|
1062
|
|