/* cStringBuffer: a file-like string buffer.
   Copyright (C) 2004 Mooneer Salem <mooneer@translator.cx>

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

/* Include necessary includes. */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <assert.h>
#include <unistd.h>
#include "config.h"

#ifdef HAVE_PTHREAD_H
#include <pthread.h>
#endif

#include "csb_private.h"
#include "csb.h"

/* csb_addchunk(): Increase the size of the buffer by BUFFER_INCREMENT.
   Parameters:
     buf: The buffer to operate on.
   Returns: nothing.
*/
void csb_addchunk(csb_buf *buf) /*@modifies buf->length, buf->string, buf->fileptr@*/ {
	/* Declare variables. */
	size_t position;
	char *newstring;

	/* Check to see we have a valid buffer. */
	assert(buf != NULL && buf->string != NULL);

	/* Save a copy of the current file position; it may change. */
	position = csb_tellpos(buf);

	/* Call realloc() to increase the size of the string. It must increase
	   by the next multiple of BUFFER_INCREMENT; however, there is a compile
	   flag that will use powers of 2 instead to reduce the number of realloc()
	   calls needed (not recommended unless you want to waste lots of RAM). */
#ifdef CSB_OPTIMIZE_AND_EAT_RAM
	buf->length = BUFFER_INCREMENT * (1 << ++buf->multipletwo);
#else
	buf->length = BUFFER_INCREMENT * (buf->length / BUFFER_INCREMENT + 1);
#endif
	newstring = malloc(buf->length);
	if (newstring == NULL) {
		/* eek! return! */
		return;
	}

	/* Copy string to new string. */
	memcpy(newstring, buf->string, buf->stringsize);
	free(buf->string);
	buf->string = newstring;

#ifdef CSB_DEBUG
	memset(buf->string + (buf->length - 1024), '\b', 1024);
#endif

	/* Reset file pointer to its previous position. */
	CSB_SEEK_NORESET(buf, position);
}

/* csb_align(): align a number on a boundary.
   Parameters:
     n: The number to align.
     grain: The boundary to align on.
   Returns: the aligned number.
*/
static size_t csb_align (size_t n, size_t grain) /*@*/
{
	const size_t remainder = n % grain;
	return (remainder > 0 ? n + (grain - remainder) : n);
} 

/* csb_prealloc(): Preallocate a set amount of space for the string.
   Parameters:
     buf: The buffer to operate on.
     length: The amount to allocate.
   Returns: true on success, false otherwise.
*/
int csb_prealloc(csb_buf *buf, size_t length) /*@modifies buf->string, buf->length, buf->fileptr@*/ {
	/* Declare variables. */
	size_t position = csb_tellpos(buf);
	char *newstring;

	/* Perform sanity checks to make sure we have a valid buffer. */
	assert(buf != NULL && buf->string != NULL);

	/* Round the length up to the next multiple of BUFFER_INCREMENT, and 
	   then allocate the memory. */
	buf->length = csb_align (length, BUFFER_INCREMENT);
	newstring = malloc(buf->length);
	if (newstring == NULL) {
		/* Return false, the reallocation wasn't successful. */
		return (FALSE);
	}

	/* Copy the string from the old variable to the new one. */
	memcpy(newstring, buf->string, buf->stringsize);
	free(buf->string);
	buf->string = newstring;

	/* Reset the position of the file pointer. */
	CSB_SEEK_NORESET(buf, position);

	/* Return true; it was a success. */
	return(TRUE);
}