1 /* gzlog.h

     2   Copyright (C) 2004 Mark Adler, all rights reserved

     3   version 1.0, 26 Nov 2004

     4 

     5   This software is provided 'as-is', without any express or implied

     6   warranty.  In no event will the author be held liable for any damages

     7   arising from the use of this software.

     8 

     9   Permission is granted to anyone to use this software for any purpose,

    10   including commercial applications, and to alter it and redistribute it

    11   freely, subject to the following restrictions:

    12 

    13   1. The origin of this software must not be misrepresented; you must not

    14      claim that you wrote the original software. If you use this software

    15      in a product, an acknowledgment in the product documentation would be

    16      appreciated but is not required.

    17   2. Altered source versions must be plainly marked as such, and must not be

    18      misrepresented as being the original software.

    19   3. This notice may not be removed or altered from any source distribution.

    20 

    21   Mark Adler    madler@alumni.caltech.edu

    22  */

    23 

    24 /*

    25    The gzlog object allows writing short messages to a gzipped log file,

    26    opening the log file locked for small bursts, and then closing it.  The log

    27    object works by appending stored data to the gzip file until 1 MB has been

    28    accumulated.  At that time, the stored data is compressed, and replaces the

    29    uncompressed data in the file.  The log file is truncated to its new size at

    30    that time.  After closing, the log file is always valid gzip file that can

    31    decompressed to recover what was written.

    32 

    33    A gzip header "extra" field contains two file offsets for appending.  The

    34    first points to just after the last compressed data.  The second points to

    35    the last stored block in the deflate stream, which is empty.  All of the

    36    data between those pointers is uncompressed.

    37  */

    38 

    39 /* Open a gzlog object, creating the log file if it does not exist.  Return

    40    NULL on error.  Note that gzlog_open() could take a long time to return if

    41    there is difficulty in locking the file. */

    42 void *gzlog_open(char *path);

    43 

    44 /* Write to a gzlog object.  Return non-zero on error.  This function will

    45    simply write data to the file uncompressed.  Compression of the data

    46    will not occur until gzlog_close() is called.  It is expected that

    47    gzlog_write() is used for a short message, and then gzlog_close() is

    48    called.  If a large amount of data is to be written, then the application

    49    should write no more than 1 MB at a time with gzlog_write() before

    50    calling gzlog_close() and then gzlog_open() again. */

    51 int gzlog_write(void *log, char *data, size_t len);

    52 

    53 /* Close a gzlog object.  Return non-zero on error.  The log file is locked

    54    until this function is called.  This function will compress stored data

    55    at the end of the gzip file if at least 1 MB has been accumulated.  Note

    56    that the file will not be a valid gzip file until this function completes.

    57  */

    58 int gzlog_close(void *log);