source: xtideuniversalbios/tags/Serial_Server_for_v2.0.0_beta1/library/File.h@ 565

//======================================================================
//
// Project:     XTIDE Universal BIOS, Serial Port Server
//
// File:        file.h - File access via standard "stdio.h" routines
//
// Routines for accessing the file system using generic routines, which
// should work on all systems.  The issue with using these is that 
// ftell() and fseek() are limited to 2 GB files (signed 32-bit quantities)
// and there is no standard for 64-bit quantities.  So, look for a 
// OS specific version of this file in the distribution, such as 
// win32/win32file.h which may be in use instead.
// 

#include <stdio.h>

class FileAccess
{
public:
    int Create( char *p_name )
    {
        fp = fopen( p_name, "r" );

        if( fp )
        {
            log( 0, "'%s' file already exists", p_name );
            fclose( fp );
            return( 0 );
        }
        
        if( !(fp = fopen( p_name, "w" )) )
            log( -1, "Could not create file '%s'", p_name );

        name = p_name;
        
        return( 1 );
    }

    void Open( char *p_name )
    {
        fp = fopen( p_name, "r+" );
        if( !fp )
            log( -1, "Could not Open '%s'", p_name );
        name = p_name;
    }

    void Close()
    {
        if( fp )
            fclose( fp );
        fp = NULL;
    }

    unsigned long SizeSectors(void)
    {
        long filesize;

        fseek( fp, 0, SEEK_END );
        filesize = ftell( fp );

        if( filesize == 0 || filesize == -1L )
            log( -1, "Could not get file size for '%s', file possibly larger than 2 GB", name );

        if( filesize & 0x1ff )
            log( -1, "'%s' not made up of 512 byte sectors", name );

        return( filesize >> 9 );     // 512 bytes per sector
    }

    void SeekSectors( unsigned long lba )
    {
        if( fseek( fp, lba * 512, SEEK_SET ) )
            log( -1, "'%s', Failed to seek to lba=%lu", name, lba );
    }

    void Read( void *buff, unsigned long len )
    {
        if( fread( buff, 1, 512, fp ) != 512 )
            log( -1, "'%s', Failed to read sector", name );
    }

    void Write( void *buff, unsigned long len )
    {
        if( fwrite( buff, 1, 512, fp ) != 512 )
            log( -1, "'%s', Failed to write sector", name );
    }

    FileAccess()
    {
        fp = NULL;
        name = NULL;
    }

    const static unsigned long MaxSectors = 4194303;  // limited by signed 32-bit file sizes 
#define USAGE_MAXSECTORS "2048 MB (signed 32-bit file size limit)"

private:
    FILE *fp;
    char *name;
};