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JK: Wayne Davison. New function for creating a chunk from an existing buffer.
http://lists.w3.org/Archives/Public/www-lib/2000JulSep/0192.html

/*								      HTChunk.c
**	CHUNK HANDLING:	FLEXIBLE ARRAYS
**
**	(c) COPYRIGHT MIT 1995.
**	Please first read the full copyright statement in the file COPYRIGH.
**	@(#) $Id: HTChunk.c,v 2.27 2000/09/01 13:47:14 kahan Exp $
**
** history:	AL, HF	28 Apr 94, Now chunk->data is filled by '\0' so
**			that the string is terminated at any time. That makes
**			HTChunk_terminate not needed any more, but never mind.
**		EGP	15 Mar 96, Added CString conversions.
**
*/

/* Library include files */
#include "wwwsys.h"
#include "HTUtils.h"
#include "HTChunk.h"				         /* Implemented here */

struct _HTChunk {
    int		size;		/* In bytes			*/
    int		growby;		/* Allocation unit in bytes	*/
    int		allocated;	/* Current size of *data	*/
    char *	data;		/* Pointer to malloced area or 0 */
};	

/* --------------------------------------------------------------------------*/

/*	Create a chunk with a certain allocation unit
**	--------------
*/
PUBLIC HTChunk * HTChunk_new (int grow)
{
    HTChunk * ch;
    if ((ch = (HTChunk  *) HT_CALLOC(1, sizeof(HTChunk))) == NULL)
        HT_OUTOFMEM("HTChunk_new");
    ch->growby = grow;
    return ch;
}


/*	Clear a chunk of all data
**	--------------------------
**	Zero the space but do NOT HT_FREE it. We zero because we promise to have
**	a NUL terminated string at all times.
*/
PUBLIC void HTChunk_clear (HTChunk * ch)
{
    if (ch) {
	ch->size = 0;
	if (ch->data) memset((void *) ch->data, '\0', ch->allocated);
    }
}


/*	Free a chunk
**	------------
*/
PUBLIC void HTChunk_delete (HTChunk * ch)
{
    if (ch) {
	HT_FREE(ch->data);
    	HT_FREE(ch);
    }
}

PUBLIC char * HTChunk_data (HTChunk * ch)
{
    return ch ? ch->data : NULL;
}

PUBLIC int HTChunk_size (HTChunk * ch)
{
    return ch ? ch->size : -1;
}

PUBLIC BOOL HTChunk_truncate (HTChunk * ch, int length)
{
    if (ch && length >= 0 && length < ch->size) {
	memset(ch->data+length, '\0', ch->size-length);
	ch->size = length;
	return YES;
    }
    return NO;
}

/*      Set the "size" of the Chunk's data
**      -----------------------------------
** The actual allocated length must  be at least 1 byte longer to hold the
** mandatory null terminator. 
*/
PUBLIC BOOL HTChunk_setSize (HTChunk * ch, int length)
{
    if (ch && length >= 0) {
	if (length < ch->size)
	    memset(ch->data+length, '\0', ch->size-length);
	else if (length >= ch->allocated)
	    HTChunk_ensure(ch, length - ch->size);
	ch->size = length;
	return YES;
    }
    return NO;
}

/*	Create a chunk from an allocated string
**	---------------------------------------
*/
PUBLIC HTChunk * HTChunk_fromCString (char * str, int grow)
{
    HTChunk * ch;
    ch = HTChunk_new(grow);
    if (str) {
	ch->data = str;			/* can't handle non-allocated str */
	ch->size = strlen(str);
	ch->allocated = ch->size + 1; /* [SIC] bobr */
    }
    return ch;
}

/*	Create a chunk from an allocated buffer
**	---------------------------------------
*/
PUBLIC HTChunk * HTChunk_fromBuffer (char * buf, int buflen, int size, int grow)
{
    HTChunk * ch;
    ch = HTChunk_new(grow);
    if (buf) {
	ch->data = buf;
	ch->size = ch->allocated = buflen;
	if (size < buflen)
	    HTChunk_setSize(ch, size);	/* This ensures the end is 0-filled */
    }
    return ch;
}

/*	Free a chunk but keep the data
**	------------------------------
*/
PUBLIC char * HTChunk_toCString (HTChunk * ch)
{
    char * ret = 0;
    if (ch) {
	ret = ch->data;
    	HT_FREE(ch);
    }
    return ret;
}

/*	Append a character
**	------------------
*/
PUBLIC void HTChunk_putc (HTChunk * ch, char c)
{
    if (ch) {	
	if (!ch->data || ch->size >= ch->allocated-1) { /* [SIC] bobr */
	    if (ch->data) {
		if ((ch->data = (char  *) HT_REALLOC(ch->data,ch->allocated+ch->growby)) == NULL)
		    HT_OUTOFMEM("HTChunk_putc");
		memset((void *) (ch->data + ch->allocated), '\0', ch->growby);
	    } else {
		if ((ch->data = (char  *) HT_CALLOC(1, ch->allocated+ch->growby)) == NULL)
		    HT_OUTOFMEM("HTChunk_putc");
	    }
	    ch->allocated += ch->growby;
	}
	*(ch->data+ch->size++) = c;
    }
}

/*	Append a string
**	---------------
*/
PUBLIC void HTChunk_puts (HTChunk * ch, const char * s)
{
    HTChunk_putb(ch, s, (int) strlen(s));
}

/*	Append a block
**	---------------
**	The string is always zero terminated
*/
PUBLIC void HTChunk_putb (HTChunk * ch, const char * block, int len)
{
    if (ch && block && len) {
	int needed = ch->size+len;
	if (needed >= ch->allocated) {
	    ch->allocated = needed - needed%ch->growby + ch->growby;
	    if (ch->data) {
		if ((ch->data = (char *) HT_REALLOC(ch->data, ch->allocated)) == NULL)
		    HT_OUTOFMEM("HTChunk_putb");
	        memset((void *) (ch->data + needed), '\0', ch->allocated-needed);
	    } else {
		if ((ch->data = (char *) HT_CALLOC(1, ch->allocated)) == NULL)
		    HT_OUTOFMEM("HTChunk_putb");
	    }
	}
	memcpy((void *) (ch->data+ch->size), block, len);
	ch->size = needed;
    }
}

PUBLIC void HTChunk_terminate (HTChunk * ch)
{
    HTChunk_putc(ch, '\0');
}

/*	Ensure a certain size
**	---------------------
*/
PUBLIC void HTChunk_ensure (HTChunk * ch, int len)
{
    if (ch && len > 0) {
	int needed = ch->size+len;
	if (needed >= ch->allocated) {
	    ch->allocated = needed - needed%ch->growby + ch->growby;
	    if (ch->data) {
		if ((ch->data = (char  *) HT_REALLOC(ch->data, ch->allocated)) == NULL)
		    HT_OUTOFMEM("HTChunk_ensure");
	        memset((void *) (ch->data + ch->size), '\0', ch->allocated-ch->size);
	    } else {
		if ((ch->data = (char  *) HT_CALLOC(1, ch->allocated)) == NULL)
		    HT_OUTOFMEM("HTChunk_ensure");
	    }
	}
    }
#if 0
    if (needed <= ch->allocated) return;
    ch->allocated = needed-1 - ((needed-1) % ch->growby)
    			     + ch->growby; /* Round up */
    ch->data = ch->data ? (char *)realloc(ch->data, ch->allocated)
			: (char *)HT_MALLOC(ch->allocated);
    if (ch->data == NULL) HT_OUTOFMEM(__FILE__, "HTChunk_ensure");
#endif
}