big_buffer.c

seed格式数据解压程序,地震分析人员必备

/*===========================================================================*/
/* DMC interim out |        big_buffer.c                   | Utility         */
/*===========================================================================*/
/*
	Name:		big_buffer.c
	Purpose:	make large contiguous dynamic buffers
	Usage:		err = big_buffer( bottom, top, size )
	Input:		char *bottom	bottom of existing buffer or NULL
				char *top		top of used part of buffer or NULL
								(points to lastused+1)
				int	size		chunk size for allocation
	Output:		err				fatal if allocation error
	Externals:	
	Warnings:	
	Errors:		
	Fatals:		allocation error
	Called by:	
	Calls to:	
	Algorithm:	if no buffer exists now, one of "size" bytes is created.
				If one exists, it is expanded to the next multiple of
				"size" larger than the current top-bottom contents.
	Notes:		
				The intent is that you will make "size" the largest
				chunk which you will ever need to add in one call,
				and stick with that constant size for the rest of
				the calls. You must "free( bottom )" when you are
				finished with the buffer, or it will stick around
				until the program exits.
	Problems:	
	References:	
	Language:	ansi C
	Revisions:	03/10/89	mark wiederspahn	written

				16apr91		mw		change
									change the way expansion is checked;
									previous scheme was conservative in
									keeping an extra Lrecl bytes of memory
									above the necessary chunk.
*/

#include "output.h"

int big_buffer( bottom, top, size )
char	**bottom;		/* buffer limits now */
char	**top;
int		size;			/* how much to grow it (bytes) */
{

int		length;			/* how big now */
int		err;			/* status */

	if( Debug > D_MAX ) fprintf( D_OUT,"[big_buffer] start\n");

	if( *bottom > *top )
		err = error_handler( FATAL,"[big_buffer] bad args" );

	err = FALSE;
	if( *bottom == NULL || *top == NULL )
	{
		if( (*bottom =
			(char *)malloc( (unsigned)(size*sizeof(char)) ) ) == NULL )
			err = error_handler( FATAL,"[big_buffer] malloc failed" );
		*top = *bottom;
		length = 0;
	}
	else
	{
		length = (int)(*top - *bottom);
		size = ( ( (length+(size-1)) / size) + 1) * size;
		if( (*bottom =
			(char *)realloc( *bottom, (unsigned)size ) ) == NULL )
			err = error_handler( FATAL,"[big_buffer] realloc failed" );
		*top = *bottom + length*sizeof( char );
	}

	if( Debug >= D_SOME )
		fprintf( D_OUT,"[big_buffer] btls = %d %d %d %d\n",
			(int)*bottom,(int)*top,length,size );

	if( Debug > D_MAX ) fprintf( D_OUT,"[big_buffer] end\n");
	return( err );
}