/* gzlog.h

  Copyright (C) 2004 Mark Adler, all rights reserved

  version 1.0, 26 Nov 2004

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

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

  arising from the use of this software.

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

  including commercial applications, and to alter it and redistribute it

  freely, subject to the following restrictions:

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

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

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

     appreciated but is not required.

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

     misrepresented as being the original software.

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

  Mark Adler    madler@alumni.caltech.edu

 */

/*

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

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

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

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

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

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

   decompressed to recover what was written.

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

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

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

   data between those pointers is uncompressed.

 */

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

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

   there is difficulty in locking the file. */

void *gzlog_open(char *path);

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

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

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

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

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

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

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

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

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

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

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

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

 */

int gzlog_close(void *log);