/****************************************************************************
*
* MODULE:       Vector library 
*   	    	
* AUTHOR(S):    Dave Gerdes, Radim Blazek
*
* PURPOSE:      Lower level functions for reading/writing/manipulating vectors.
*
* COPYRIGHT:    (C) 2001 by the GRASS Development Team
*
*               This program is free software under the GNU General Public
*   	    	License (>=v2). Read the file COPYING that comes with GRASS
*   	    	for details.
*
*****************************************************************************/
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include "gis.h"
#include "Vect.h"

/* 
*  Note: seems that the time is almost the same for both cases: 
*        - reading from file 
*        - load whole file to memory and read from memory
*/ 

/* Get GVFILE position.
*
*  Returns: current file position
*/           
long 
dig_ftell ( GVFILE *file )
{
    if ( file->loaded )  /* using memory */
	return ( file->current - file->start);
	
    return ( ftell ( file->file ) );
}

/* Set GVFILE position.
*
*  Returns: 0 OK, -1 error
*/           
int 
dig_fseek ( GVFILE *file, long offset, int whence )
{
    if ( file->loaded ) {  /* using memory */
	switch ( whence ) {
	    case SEEK_SET:
	        file->current = file->start + offset ;
                break;
	    case SEEK_CUR:
	        file->current += offset ;
                break;
	    case SEEK_END:
	        file->current = file->start + file->size + offset ;
                break;
	}
        return 0;
    }
	
    return ( fseek ( file->file, offset, whence ) );
}

/* Rewind  GVFILE position.
*
*  Returns: nothing
*/           
void
dig_rewind ( GVFILE *file )
{
    if ( file->loaded ) {  /* using memory */
	file->current = file->start;
    } else {
        rewind ( file->file );
    }
}

/* Flush GVFILE.
*
*  Returns: nothing
*/           
int
dig_fflush ( GVFILE *file )
{
    if ( file->loaded ) {  /* using memory */
	return 0;
    } else {
        return ( fflush ( file->file ) );
    }
}

/* Read GVFILE.
*
*  Returns: number of read members
*/           
size_t
dig_fread ( void *ptr, size_t size, size_t nmemb, GVFILE *file )
{
    long tot;
    size_t cnt;

    if ( file->loaded ) {  /* using memory */
	if ( file->current >= file->end ) { /* EOF */
	    return 0;
	}
	tot = size * nmemb;
	cnt = nmemb;
	if ( file->current + tot > file->end ) {
	   tot = file->end - file->current ;
	   cnt = (int) tot / size;
	}
	memcpy ( ptr, file->current, tot);
	file->current += tot;
	return ( cnt );
    }
    return ( fread (ptr, size, nmemb, file->file) );
}

/* Write GVFILE.
*
*  Returns: number of items written
*/           
size_t
dig_fwrite ( void *ptr, size_t size, size_t nmemb, GVFILE *file )
{
    if ( file->loaded ) {  /* using memory */
	G_fatal_error ( "Writing to file loaded to memory not supported" );
    }

    return fwrite (ptr, size, nmemb, file->file);
}

/* Init GVFILE.
*
*  Returns: nothing
*/           
void
dig_file_init ( GVFILE *file )
{
    file->file = NULL;
    file->start = NULL;
    file->current = NULL;
    file->end = NULL;
    file->size = 0;
    file->alloc = 0;
    file->loaded = 0;
}

/* Load opened GVFILE to memory.
*  Warning: position in file is set to the beginning.
*
*  Returns: 1 loaded, 0, not loaded, -1 Error
*/           
int
dig_file_load ( GVFILE *file )
{
    int ret, mode, load;
    char *cmode;
    unsigned size;
    struct stat sbuf;
    
    G_debug (2, "dig_file_load ()" );

    if ( file->file == NULL ) {
       G_warning ("Cannot load file to memory, file not open.");
       return -1;
    }

    /* Get mode */
    mode = GV_MEMORY_NEVER;
    cmode = G__getenv("GV_MEMORY");
    if ( cmode != NULL ) {
	if ( G_strcasecmp ( cmode, "ALWAYS" ) == 0 )
	    mode = GV_MEMORY_ALWAYS;
	else if ( G_strcasecmp ( cmode, "NEVER" ) == 0 )
	    mode = GV_MEMORY_NEVER;
	else if ( G_strcasecmp ( cmode, "AUTO" ) == 0 )
	    mode = GV_MEMORY_AUTO;
	else 
	    G_warning ("Vector memory mode not supported, using 'AUTO'");
    }
    G_debug (2, "  requested mode = %d", mode );


    fstat ( fileno (file->file), &sbuf );
    size = sbuf.st_size;
    
    G_debug (2, "  size = %u", size );

    /* Decide if the file should be loaded */
    /* TODO: I don't know how to get size of free memory (portability) to decide if load or not for auto */
    if ( mode == GV_MEMORY_AUTO ) mode = GV_MEMORY_NEVER;
    if ( mode == GV_MEMORY_ALWAYS ) load = 1; else load = 0;
    
    if ( load ) {
	file->start = G_malloc ( size );
	if ( file->start == NULL ) return -1;

	fseek (file->file, 0L, 0);
	ret = fread ( file->start, size, 1, file->file ); /* Better to read in smaller portions? */
	fseek (file->file, 0L, 0); /* reset to the beginning */
	
	if (ret <= 0) {
	    G_free ( file->start );
	    return -1;
	}

	file->alloc = size;
	file->size = size;
	file->current = file->start;
	file->end = file->start + size;

	file->loaded = 1;
	G_debug (2, "  file was loaded to the memory" );
        return 1;
    } else {
	G_debug (2, "  file was not loaded to the memory" );
    }

    return 0;
}

/* Free GVFILE.
*
*  Returns: nothing
*/           
void
dig_file_free ( GVFILE *file )
{
    if ( file->loaded ) {
        G_free ( file->start );
        file->loaded = 0;
        file->alloc = 0;
    }
}