zlib/examples/gzlog.c

40    - compressed data ending initially with empty stored block
41    - uncompressed data filling out originally empty stored block and
42      subsequent stored blocks as needed (16K max each)
49    stored block and determine where to append the data in the foo.add file, as
95    recovery if interrupted.  Multi-byte values are stored little endian
99    for large files is actually the length modulo 2^32.)  The stored block
110    - Pointer to first stored block length -- this points to the two-byte length
111      of the first stored block, which is followed by the two-byte, one's
112      complement of that length.  The stored block length is preceded by the
113      three-bit header of the stored block, which is the actual start of the
114      stored block in the deflate format.  See the bit offset field below.
115    - Pointer to the last stored block length.  This is the same as above, but
116      for the last stored block of the uncompressed data in the gzip file.
117      Initially this is the same as the first stored block length pointer.
118      When the stored block gets to 16K (see the MAX_STORE define), then a new
119      stored block as added, at which point the last stored block length pointer
120      is different from the first stored block length pointer.  When they are
121      different, the first bit of the last stored block header is eight bits, or
128      stored in the gzip file, compressed and uncompressed.  It is used to
131    - Final stored block length.  This is used to quickly find where to append,
132      and allows the restoration of the original final stored block state when
134    - First stored block start as the number of bits back from the final stored
136      stored as the low three bits of the final byte of the extra field after
137      subtracting three (0..7).  This allows the last-block bit of the stored
138      block header to be updated when a new stored block is added, for the case
139      when the first stored block and the last stored block are the same.  (When
142      data in the compress operation, overwriting the previous first stored
168    + Restore the original last-block bit and stored block length of the last
169      stored block from the information in the extra field, in case a previous
171    - Append the provided data to the last stored block, creating new stored
172      blocks as needed and updating the stored blocks last-block bits and
183    - Read all of the uncompressed data in the stored blocks in foo.gz and write
200      written over by a last-bit-set empty stored block.
203    - Write over the extra field with the updated stored block offsets, bits
260 /* maximum stored block size in Kbytes -- must be in 1..63 */
263 /* number of stored Kbytes to trigger compression (must be >= 32 to allow
265    discard the stored block headers contribution of five bytes each) */
294     off_t first;    /* offset of first stored block first length byte */
296     uint stored;    /* bytes currently in last stored block */
297     off_t last;     /* offset of last stored block first length byte */
320     52, 0, 0, 0, 0, 0, 0, 0,    /* offset of first stored block length */
321     52, 0, 0, 0, 0, 0, 0, 0,    /* offset of last stored block length */
324     0, 0,                       /* final stored block data length */
332     1, 0, 0, 0xff, 0xff,        /* empty stored block (last) */
426     log->stored = PULL2(buf + HEAD + 32);
448     PUT2(ext + 32, log->stored);
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
480     /* change the last-bit of the last stored block as requested -- note
482        of a stored block being 00 and per the convention that the bits to
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);
493            lseek(log->fd, log->stored, SEEK_CUR) < 0 ? -1 : 0;
499    deflate stored blocks.  Return -1 if there was an error reading or writing
513     /* append, adding stored blocks and updating the offset of the last stored
517         put = (MAX_STORE << 10) - log->stored;
526             log->stored += put;
531         /* if we need to, add a new empty stored block */
537             /* point to new, empty stored block */
538             log->last += 4 + log->stored + 1;
539             log->stored = 0;
600    overwrites the previous uncompressed data, which was stored in foo.add
605    appending a final empty stored block and the gzip trailer.  Return -1 if
701     log->stored = 0;
928           log->stored;
947         if (lseek(log->fd, 0, SEEK_CUR) != log->last + 4 + log->stored)
974         log->stored = 0;
1032     if (((log->last - log->first) >> 10) + (log->stored >> 10) < TRIGGER)