1062 lines
41 KiB
C
1062 lines
41 KiB
C
/*
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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 the compress recovery, a missing foo.add file results in foo.gz
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being 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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abandoned, delete it, and try the exclusive create again. Save the lock
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file modify time for verification of ownership. Return 0 on success, or -1
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on failure, usually due to an access restriction or invalid path. Note that
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if stat() or unlink() fails, it may be due to another process noticing the
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abandoned lock file a smidge sooner and deleting it, so those are not
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flagged as an error. */
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local int log_lock(struct log *log)
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{
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int fd;
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struct stat st;
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strcpy(log->end, ".lock");
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while ((fd = open(log->path, O_CREAT | O_EXCL, 0644)) < 0) {
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if (errno != EEXIST)
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return -1;
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if (stat(log->path, &st) == 0 && time(NULL) - st.st_mtime > PATIENCE) {
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unlink(log->path);
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continue;
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}
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sleep(2); /* relinquish the CPU for two seconds while waiting */
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}
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close(fd);
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if (stat(log->path, &st) == 0)
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log->lock = st.st_mtime;
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return 0;
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}
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/* Update the modify time of the lock file to now, in order to prevent another
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task from thinking that the lock is stale. Save the lock file modify time
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for verification of ownership. */
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local void log_touch(struct log *log)
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{
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struct stat st;
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strcpy(log->end, ".lock");
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utimes(log->path, NULL);
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if (stat(log->path, &st) == 0)
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log->lock = st.st_mtime;
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}
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/* Check the log file modify time against what is expected. Return true if
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this is not our lock. If it is our lock, touch it to keep it. */
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local int log_check(struct log *log)
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{
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struct stat st;
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strcpy(log->end, ".lock");
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if (stat(log->path, &st) || st.st_mtime != log->lock)
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return 1;
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log_touch(log);
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return 0;
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}
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/* Unlock a previously acquired lock, but only if it's ours. */
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local void log_unlock(struct log *log)
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{
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if (log_check(log))
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return;
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strcpy(log->end, ".lock");
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unlink(log->path);
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log->lock = 0;
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}
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/* Check the gzip header and read in the extra field, filling in the values in
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the log structure. Return op on success or -1 if the gzip header was not as
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expected. op is the current operation in progress last written to the extra
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field. This assumes that the gzip file has already been opened, with the
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file descriptor log->fd. */
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local int log_head(struct log *log)
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{
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int op;
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unsigned char buf[HEAD + EXTRA];
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if (lseek(log->fd, 0, SEEK_SET) < 0 ||
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read(log->fd, buf, HEAD + EXTRA) != HEAD + EXTRA ||
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memcmp(buf, log_gzhead, HEAD)) {
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return -1;
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}
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log->first = PULL8(buf + HEAD);
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log->last = PULL8(buf + HEAD + 8);
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log->ccrc = PULL4(buf + HEAD + 16);
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log->clen = PULL4(buf + HEAD + 20);
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log->tcrc = PULL4(buf + HEAD + 24);
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log->tlen = PULL4(buf + HEAD + 28);
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log->stored = PULL2(buf + HEAD + 32);
|
|
log->back = 3 + (buf[HEAD + 34] & 7);
|
|
op = (buf[HEAD + 34] >> 3) & 3;
|
|
return op;
|
|
}
|
|
|
|
/* Write over the extra field contents, marking the operation as op. Use fsync
|
|
to assure that the device is written to, and in the requested order. This
|
|
operation, and only this operation, is assumed to be atomic in order to
|
|
assure that the log is recoverable in the event of an interruption at any
|
|
point in the process. Return -1 if the write to foo.gz failed. */
|
|
local int log_mark(struct log *log, int op)
|
|
{
|
|
int ret;
|
|
unsigned char ext[EXTRA];
|
|
|
|
PUT8(ext, log->first);
|
|
PUT8(ext + 8, log->last);
|
|
PUT4(ext + 16, log->ccrc);
|
|
PUT4(ext + 20, log->clen);
|
|
PUT4(ext + 24, log->tcrc);
|
|
PUT4(ext + 28, log->tlen);
|
|
PUT2(ext + 32, log->stored);
|
|
ext[34] = log->back - 3 + (op << 3);
|
|
fsync(log->fd);
|
|
ret = lseek(log->fd, HEAD, SEEK_SET) < 0 ||
|
|
write(log->fd, ext, EXTRA) != EXTRA ? -1 : 0;
|
|
fsync(log->fd);
|
|
return ret;
|
|
}
|
|
|
|
/* Rewrite the last block header bits and subsequent zero bits to get to a byte
|
|
boundary, setting the last block bit if last is true, and then write the
|
|
remainder of the stored block header (length and one's complement). Leave
|
|
the file pointer after the end of the last stored block data. Return -1 if
|
|
there is a read or write failure on the foo.gz file */
|
|
local int log_last(struct log *log, int last)
|
|
{
|
|
int back, len, mask;
|
|
unsigned char buf[6];
|
|
|
|
/* determine the locations of the bytes and bits to modify */
|
|
back = log->last == log->first ? log->back : 8;
|
|
len = back > 8 ? 2 : 1; /* bytes back from log->last */
|
|
mask = 0x80 >> ((back - 1) & 7); /* mask for block last-bit */
|
|
|
|
/* get the byte to modify (one or two back) into buf[0] -- don't need to
|
|
read the byte if the last-bit is eight bits back, since in that case
|
|
the entire byte will be modified */
|
|
buf[0] = 0;
|
|
if (back != 8 && (lseek(log->fd, log->last - len, SEEK_SET) < 0 ||
|
|
read(log->fd, buf, 1) != 1))
|
|
return -1;
|
|
|
|
/* change the last-bit of the last stored block as requested -- note
|
|
that all bits above the last-bit are set to zero, per the type bits
|
|
of a stored block being 00 and per the convention that the bits to
|
|
bring the stream to a byte boundary are also zeros */
|
|
buf[1] = 0;
|
|
buf[2 - len] = (*buf & (mask - 1)) + (last ? mask : 0);
|
|
|
|
/* write the modified stored block header and lengths, move the file
|
|
pointer to after the last stored block data */
|
|
PUT2(buf + 2, log->stored);
|
|
PUT2(buf + 4, log->stored ^ 0xffff);
|
|
return lseek(log->fd, log->last - len, SEEK_SET) < 0 ||
|
|
write(log->fd, buf + 2 - len, len + 4) != len + 4 ||
|
|
lseek(log->fd, log->stored, SEEK_CUR) < 0 ? -1 : 0;
|
|
}
|
|
|
|
/* Append len bytes from data to the locked and open log file. len may be zero
|
|
if recovering and no .add file was found. In that case, the previous state
|
|
of the foo.gz file is restored. The data is appended uncompressed in
|
|
deflate stored blocks. Return -1 if there was an error reading or writing
|
|
the foo.gz file. */
|
|
local int log_append(struct log *log, unsigned char *data, size_t len)
|
|
{
|
|
uint put;
|
|
off_t end;
|
|
unsigned char buf[8];
|
|
|
|
/* set the last block last-bit and length, in case recovering an
|
|
interrupted append, then position the file pointer to append to the
|
|
block */
|
|
if (log_last(log, 1))
|
|
return -1;
|
|
|
|
/* append, adding stored blocks and updating the offset of the last stored
|
|
block as needed, and update the total crc and length */
|
|
while (len) {
|
|
/* append as much as we can to the last block */
|
|
put = (MAX_STORE << 10) - log->stored;
|
|
if (put > len)
|
|
put = (uint)len;
|
|
if (put) {
|
|
if (write(log->fd, data, put) != put)
|
|
return -1;
|
|
BAIL(1);
|
|
log->tcrc = crc32(log->tcrc, data, put);
|
|
log->tlen += put;
|
|
log->stored += put;
|
|
data += put;
|
|
len -= put;
|
|
}
|
|
|
|
/* if we need to, add a new empty stored block */
|
|
if (len) {
|
|
/* mark current block as not last */
|
|
if (log_last(log, 0))
|
|
return -1;
|
|
|
|
/* point to new, empty stored block */
|
|
log->last += 4 + log->stored + 1;
|
|
log->stored = 0;
|
|
}
|
|
|
|
/* mark last block as last, update its length */
|
|
if (log_last(log, 1))
|
|
return -1;
|
|
BAIL(2);
|
|
}
|
|
|
|
/* write the new crc and length trailer, and truncate just in case (could
|
|
be recovering from partial append with a missing foo.add file) */
|
|
PUT4(buf, log->tcrc);
|
|
PUT4(buf + 4, log->tlen);
|
|
if (write(log->fd, buf, 8) != 8 ||
|
|
(end = lseek(log->fd, 0, SEEK_CUR)) < 0 || ftruncate(log->fd, end))
|
|
return -1;
|
|
|
|
/* write the extra field, marking the log file as done, delete .add file */
|
|
if (log_mark(log, NO_OP))
|
|
return -1;
|
|
strcpy(log->end, ".add");
|
|
unlink(log->path); /* ignore error, since may not exist */
|
|
return 0;
|
|
}
|
|
|
|
/* Replace the foo.dict file with the foo.temp file. Also delete the foo.add
|
|
file, since the compress operation may have been interrupted before that was
|
|
done. Returns 1 if memory could not be allocated, or -1 if reading or
|
|
writing foo.gz fails, or if the rename fails for some reason other than
|
|
foo.temp not existing. foo.temp not existing is a permitted error, since
|
|
the replace operation may have been interrupted after the rename is done,
|
|
but before foo.gz is marked as complete. */
|
|
local int log_replace(struct log *log)
|
|
{
|
|
int ret;
|
|
char *dest;
|
|
|
|
/* delete foo.add file */
|
|
strcpy(log->end, ".add");
|
|
unlink(log->path); /* ignore error, since may not exist */
|
|
BAIL(3);
|
|
|
|
/* rename foo.name to foo.dict, replacing foo.dict if it exists */
|
|
strcpy(log->end, ".dict");
|
|
dest = malloc(strlen(log->path) + 1);
|
|
if (dest == NULL)
|
|
return -2;
|
|
strcpy(dest, log->path);
|
|
strcpy(log->end, ".temp");
|
|
ret = rename(log->path, dest);
|
|
free(dest);
|
|
if (ret && errno != ENOENT)
|
|
return -1;
|
|
BAIL(4);
|
|
|
|
/* mark the foo.gz file as done */
|
|
return log_mark(log, NO_OP);
|
|
}
|
|
|
|
/* Compress the len bytes at data and append the compressed data to the
|
|
foo.gz deflate data immediately after the previous compressed data. This
|
|
overwrites the previous uncompressed data, which was stored in foo.add
|
|
and is the data provided in data[0..len-1]. If this operation is
|
|
interrupted, it picks up at the start of this routine, with the foo.add
|
|
file read in again. If there is no data to compress (len == 0), then we
|
|
simply terminate the foo.gz file after the previously compressed data,
|
|
appending a final empty stored block and the gzip trailer. Return -1 if
|
|
reading or writing the log.gz file failed, or -2 if there was a memory
|
|
allocation failure. */
|
|
local int log_compress(struct log *log, unsigned char *data, size_t len)
|
|
{
|
|
int fd;
|
|
uint got, max;
|
|
ssize_t dict;
|
|
off_t end;
|
|
z_stream strm;
|
|
unsigned char buf[DICT];
|
|
|
|
/* compress and append compressed data */
|
|
if (len) {
|
|
/* set up for deflate, allocating memory */
|
|
strm.zalloc = Z_NULL;
|
|
strm.zfree = Z_NULL;
|
|
strm.opaque = Z_NULL;
|
|
if (deflateInit2(&strm, Z_DEFAULT_COMPRESSION, Z_DEFLATED, -15, 8,
|
|
Z_DEFAULT_STRATEGY) != Z_OK)
|
|
return -2;
|
|
|
|
/* read in dictionary (last 32K of data that was compressed) */
|
|
strcpy(log->end, ".dict");
|
|
fd = open(log->path, O_RDONLY, 0);
|
|
if (fd >= 0) {
|
|
dict = read(fd, buf, DICT);
|
|
close(fd);
|
|
if (dict < 0) {
|
|
deflateEnd(&strm);
|
|
return -1;
|
|
}
|
|
if (dict)
|
|
deflateSetDictionary(&strm, buf, (uint)dict);
|
|
}
|
|
log_touch(log);
|
|
|
|
/* prime deflate with last bits of previous block, position write
|
|
pointer to write those bits and overwrite what follows */
|
|
if (lseek(log->fd, log->first - (log->back > 8 ? 2 : 1),
|
|
SEEK_SET) < 0 ||
|
|
read(log->fd, buf, 1) != 1 || lseek(log->fd, -1, SEEK_CUR) < 0) {
|
|
deflateEnd(&strm);
|
|
return -1;
|
|
}
|
|
deflatePrime(&strm, (8 - log->back) & 7, *buf);
|
|
|
|
/* compress, finishing with a partial non-last empty static block */
|
|
strm.next_in = data;
|
|
max = (((uint)0 - 1) >> 1) + 1; /* in case int smaller than size_t */
|
|
do {
|
|
strm.avail_in = len > max ? max : (uint)len;
|
|
len -= strm.avail_in;
|
|
do {
|
|
strm.avail_out = DICT;
|
|
strm.next_out = buf;
|
|
deflate(&strm, len ? Z_NO_FLUSH : Z_PARTIAL_FLUSH);
|
|
got = DICT - strm.avail_out;
|
|
if (got && write(log->fd, buf, got) != got) {
|
|
deflateEnd(&strm);
|
|
return -1;
|
|
}
|
|
log_touch(log);
|
|
} while (strm.avail_out == 0);
|
|
} while (len);
|
|
deflateEnd(&strm);
|
|
BAIL(5);
|
|
|
|
/* find start of empty static block -- scanning backwards the first one
|
|
bit is the second bit of the block, if the last byte is zero, then
|
|
we know the byte before that has a one in the top bit, since an
|
|
empty static block is ten bits long */
|
|
if ((log->first = lseek(log->fd, -1, SEEK_CUR)) < 0 ||
|
|
read(log->fd, buf, 1) != 1)
|
|
return -1;
|
|
log->first++;
|
|
if (*buf) {
|
|
log->back = 1;
|
|
while ((*buf & ((uint)1 << (8 - log->back++))) == 0)
|
|
; /* guaranteed to terminate, since *buf != 0 */
|
|
}
|
|
else
|
|
log->back = 10;
|
|
|
|
/* update compressed crc and length */
|
|
log->ccrc = log->tcrc;
|
|
log->clen = log->tlen;
|
|
}
|
|
else {
|
|
/* no data to compress -- fix up existing gzip stream */
|
|
log->tcrc = log->ccrc;
|
|
log->tlen = log->clen;
|
|
}
|
|
|
|
/* complete and truncate gzip stream */
|
|
log->last = log->first;
|
|
log->stored = 0;
|
|
PUT4(buf, log->tcrc);
|
|
PUT4(buf + 4, log->tlen);
|
|
if (log_last(log, 1) || write(log->fd, buf, 8) != 8 ||
|
|
(end = lseek(log->fd, 0, SEEK_CUR)) < 0 || ftruncate(log->fd, end))
|
|
return -1;
|
|
BAIL(6);
|
|
|
|
/* mark as being in the replace operation */
|
|
if (log_mark(log, REPLACE_OP))
|
|
return -1;
|
|
|
|
/* execute the replace operation and mark the file as done */
|
|
return log_replace(log);
|
|
}
|
|
|
|
/* log a repair record to the .repairs file */
|
|
local void log_log(struct log *log, int op, char *record)
|
|
{
|
|
time_t now;
|
|
FILE *rec;
|
|
|
|
now = time(NULL);
|
|
strcpy(log->end, ".repairs");
|
|
rec = fopen(log->path, "a");
|
|
if (rec == NULL)
|
|
return;
|
|
fprintf(rec, "%.24s %s recovery: %s\n", ctime(&now), op == APPEND_OP ?
|
|
"append" : (op == COMPRESS_OP ? "compress" : "replace"), record);
|
|
fclose(rec);
|
|
return;
|
|
}
|
|
|
|
/* Recover the interrupted operation op. First read foo.add for recovering an
|
|
append or compress operation. Return -1 if there was an error reading or
|
|
writing foo.gz or reading an existing foo.add, or -2 if there was a memory
|
|
allocation failure. */
|
|
local int log_recover(struct log *log, int op)
|
|
{
|
|
int fd, ret = 0;
|
|
unsigned char *data = NULL;
|
|
size_t len = 0;
|
|
struct stat st;
|
|
|
|
/* log recovery */
|
|
log_log(log, op, "start");
|
|
|
|
/* load foo.add file if expected and present */
|
|
if (op == APPEND_OP || op == COMPRESS_OP) {
|
|
strcpy(log->end, ".add");
|
|
if (stat(log->path, &st) == 0 && st.st_size) {
|
|
len = (size_t)(st.st_size);
|
|
if ((off_t)len != st.st_size ||
|
|
(data = malloc(st.st_size)) == NULL) {
|
|
log_log(log, op, "allocation failure");
|
|
return -2;
|
|
}
|
|
if ((fd = open(log->path, O_RDONLY, 0)) < 0) {
|
|
free(data);
|
|
log_log(log, op, ".add file read failure");
|
|
return -1;
|
|
}
|
|
ret = (size_t)read(fd, data, len) != len;
|
|
close(fd);
|
|
if (ret) {
|
|
free(data);
|
|
log_log(log, op, ".add file read failure");
|
|
return -1;
|
|
}
|
|
log_log(log, op, "loaded .add file");
|
|
}
|
|
else
|
|
log_log(log, op, "missing .add file!");
|
|
}
|
|
|
|
/* recover the interrupted operation */
|
|
switch (op) {
|
|
case APPEND_OP:
|
|
ret = log_append(log, data, len);
|
|
break;
|
|
case COMPRESS_OP:
|
|
ret = log_compress(log, data, len);
|
|
break;
|
|
case REPLACE_OP:
|
|
ret = log_replace(log);
|
|
}
|
|
|
|
/* log status */
|
|
log_log(log, op, ret ? "failure" : "complete");
|
|
|
|
/* clean up */
|
|
if (data != NULL)
|
|
free(data);
|
|
return ret;
|
|
}
|
|
|
|
/* Close the foo.gz file (if open) and release the lock. */
|
|
local void log_close(struct log *log)
|
|
{
|
|
if (log->fd >= 0)
|
|
close(log->fd);
|
|
log->fd = -1;
|
|
log_unlock(log);
|
|
}
|
|
|
|
/* Open foo.gz, verify the header, and load the extra field contents, after
|
|
first creating the foo.lock file to gain exclusive access to the foo.*
|
|
files. If foo.gz does not exist or is empty, then write the initial header,
|
|
extra, and body content of an empty foo.gz log file. If there is an error
|
|
creating the lock file due to access restrictions, or an error reading or
|
|
writing the foo.gz file, or if the foo.gz file is not a proper log file for
|
|
this object (e.g. not a gzip file or does not contain the expected extra
|
|
field), then return true. If there is an error, the lock is released.
|
|
Otherwise, the lock is left in place. */
|
|
local int log_open(struct log *log)
|
|
{
|
|
int op;
|
|
|
|
/* release open file resource if left over -- can occur if lock lost
|
|
between gzlog_open() and gzlog_write() */
|
|
if (log->fd >= 0)
|
|
close(log->fd);
|
|
log->fd = -1;
|
|
|
|
/* negotiate exclusive access */
|
|
if (log_lock(log) < 0)
|
|
return -1;
|
|
|
|
/* open the log file, foo.gz */
|
|
strcpy(log->end, ".gz");
|
|
log->fd = open(log->path, O_RDWR | O_CREAT, 0644);
|
|
if (log->fd < 0) {
|
|
log_close(log);
|
|
return -1;
|
|
}
|
|
|
|
/* if new, initialize foo.gz with an empty log, delete old dictionary */
|
|
if (lseek(log->fd, 0, SEEK_END) == 0) {
|
|
if (write(log->fd, log_gzhead, HEAD) != HEAD ||
|
|
write(log->fd, log_gzext, EXTRA) != EXTRA ||
|
|
write(log->fd, log_gzbody, BODY) != BODY) {
|
|
log_close(log);
|
|
return -1;
|
|
}
|
|
strcpy(log->end, ".dict");
|
|
unlink(log->path);
|
|
}
|
|
|
|
/* verify log file and load extra field information */
|
|
if ((op = log_head(log)) < 0) {
|
|
log_close(log);
|
|
return -1;
|
|
}
|
|
|
|
/* check for interrupted process and if so, recover */
|
|
if (op != NO_OP && log_recover(log, op)) {
|
|
log_close(log);
|
|
return -1;
|
|
}
|
|
|
|
/* touch the lock file to prevent another process from grabbing it */
|
|
log_touch(log);
|
|
return 0;
|
|
}
|
|
|
|
/* See gzlog.h for the description of the external methods below */
|
|
gzlog *gzlog_open(char *path)
|
|
{
|
|
size_t n;
|
|
struct log *log;
|
|
|
|
/* check arguments */
|
|
if (path == NULL || *path == 0)
|
|
return NULL;
|
|
|
|
/* allocate and initialize log structure */
|
|
log = malloc(sizeof(struct log));
|
|
if (log == NULL)
|
|
return NULL;
|
|
strcpy(log->id, LOGID);
|
|
log->fd = -1;
|
|
|
|
/* save path and end of path for name construction */
|
|
n = strlen(path);
|
|
log->path = malloc(n + 9); /* allow for ".repairs" */
|
|
if (log->path == NULL) {
|
|
free(log);
|
|
return NULL;
|
|
}
|
|
strcpy(log->path, path);
|
|
log->end = log->path + n;
|
|
|
|
/* gain exclusive access and verify log file -- may perform a
|
|
recovery operation if needed */
|
|
if (log_open(log)) {
|
|
free(log->path);
|
|
free(log);
|
|
return NULL;
|
|
}
|
|
|
|
/* return pointer to log structure */
|
|
return log;
|
|
}
|
|
|
|
/* gzlog_compress() return values:
|
|
0: all good
|
|
-1: file i/o error (usually access issue)
|
|
-2: memory allocation failure
|
|
-3: invalid log pointer argument */
|
|
int gzlog_compress(gzlog *logd)
|
|
{
|
|
int fd, ret;
|
|
uint block;
|
|
size_t len, next;
|
|
unsigned char *data, buf[5];
|
|
struct log *log = logd;
|
|
|
|
/* check arguments */
|
|
if (log == NULL || strcmp(log->id, LOGID))
|
|
return -3;
|
|
|
|
/* see if we lost the lock -- if so get it again and reload the extra
|
|
field information (it probably changed), recover last operation if
|
|
necessary */
|
|
if (log_check(log) && log_open(log))
|
|
return -1;
|
|
|
|
/* create space for uncompressed data */
|
|
len = ((size_t)(log->last - log->first) & ~(((size_t)1 << 10) - 1)) +
|
|
log->stored;
|
|
if ((data = malloc(len)) == NULL)
|
|
return -2;
|
|
|
|
/* do statement here is just a cheap trick for error handling */
|
|
do {
|
|
/* read in the uncompressed data */
|
|
if (lseek(log->fd, log->first - 1, SEEK_SET) < 0)
|
|
break;
|
|
next = 0;
|
|
while (next < len) {
|
|
if (read(log->fd, buf, 5) != 5)
|
|
break;
|
|
block = PULL2(buf + 1);
|
|
if (next + block > len ||
|
|
read(log->fd, (char *)data + next, block) != block)
|
|
break;
|
|
next += block;
|
|
}
|
|
if (lseek(log->fd, 0, SEEK_CUR) != log->last + 4 + log->stored)
|
|
break;
|
|
log_touch(log);
|
|
|
|
/* write the uncompressed data to the .add file */
|
|
strcpy(log->end, ".add");
|
|
fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
|
|
if (fd < 0)
|
|
break;
|
|
ret = (size_t)write(fd, data, len) != len;
|
|
if (ret | close(fd))
|
|
break;
|
|
log_touch(log);
|
|
|
|
/* write the dictionary for the next compress to the .temp file */
|
|
strcpy(log->end, ".temp");
|
|
fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
|
|
if (fd < 0)
|
|
break;
|
|
next = DICT > len ? len : DICT;
|
|
ret = (size_t)write(fd, (char *)data + len - next, next) != next;
|
|
if (ret | close(fd))
|
|
break;
|
|
log_touch(log);
|
|
|
|
/* roll back to compressed data, mark the compress in progress */
|
|
log->last = log->first;
|
|
log->stored = 0;
|
|
if (log_mark(log, COMPRESS_OP))
|
|
break;
|
|
BAIL(7);
|
|
|
|
/* compress and append the data (clears mark) */
|
|
ret = log_compress(log, data, len);
|
|
free(data);
|
|
return ret;
|
|
} while (0);
|
|
|
|
/* broke out of do above on i/o error */
|
|
free(data);
|
|
return -1;
|
|
}
|
|
|
|
/* gzlog_write() return values:
|
|
0: all good
|
|
-1: file i/o error (usually access issue)
|
|
-2: memory allocation failure
|
|
-3: invalid log pointer argument */
|
|
int gzlog_write(gzlog *logd, void *data, size_t len)
|
|
{
|
|
int fd, ret;
|
|
struct log *log = logd;
|
|
|
|
/* check arguments */
|
|
if (log == NULL || strcmp(log->id, LOGID))
|
|
return -3;
|
|
if (data == NULL || len <= 0)
|
|
return 0;
|
|
|
|
/* see if we lost the lock -- if so get it again and reload the extra
|
|
field information (it probably changed), recover last operation if
|
|
necessary */
|
|
if (log_check(log) && log_open(log))
|
|
return -1;
|
|
|
|
/* create and write .add file */
|
|
strcpy(log->end, ".add");
|
|
fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
|
|
if (fd < 0)
|
|
return -1;
|
|
ret = (size_t)write(fd, data, len) != len;
|
|
if (ret | close(fd))
|
|
return -1;
|
|
log_touch(log);
|
|
|
|
/* mark log file with append in progress */
|
|
if (log_mark(log, APPEND_OP))
|
|
return -1;
|
|
BAIL(8);
|
|
|
|
/* append data (clears mark) */
|
|
if (log_append(log, data, len))
|
|
return -1;
|
|
|
|
/* check to see if it's time to compress -- if not, then done */
|
|
if (((log->last - log->first) >> 10) + (log->stored >> 10) < TRIGGER)
|
|
return 0;
|
|
|
|
/* time to compress */
|
|
return gzlog_compress(log);
|
|
}
|
|
|
|
/* gzlog_close() return values:
|
|
0: ok
|
|
-3: invalid log pointer argument */
|
|
int gzlog_close(gzlog *logd)
|
|
{
|
|
struct log *log = logd;
|
|
|
|
/* check arguments */
|
|
if (log == NULL || strcmp(log->id, LOGID))
|
|
return -3;
|
|
|
|
/* close the log file and release the lock */
|
|
log_close(log);
|
|
|
|
/* free structure and return */
|
|
if (log->path != NULL)
|
|
free(log->path);
|
|
strcpy(log->id, "bad");
|
|
free(log);
|
|
return 0;
|
|
}
|