SMFS reference

SMFS is a Secure Memory File System (as exported to functionality modules (FMs)).

It allows FMs to store keys into tamper-protected battery-backed Static RAM (SRAM)

It has the following general specifications:

• Arbitrary depth directory structure supported.

• File names are any character other than '\' or '/'.

• Path separator is '/' (the Windows '\' is not allowed)

• Files are of fixed size and initialized with zeros when created.

• Directories will expand in size as needed to fit more files.

This topic describes important SMFS constants, SMFS error codes, the file attributes structure, and SMFS function descriptions.

Important SMFS constants

• Max file name length is 31

• Max path length is 100

• Max number of open files is 32

• Max number of file search handles is 16

SMFS Error codes

File attributes structure (SmFsAttr)

This structure holds the file or directory attributes.

Synopsis

SmFsAttr {
unsigned int Size;  
unsigned int isDir;
   };

Members

Size: Current file size in bytes or directory size in entries

isDir: Flag specifying if file is a directory

Function descriptions

This section contains descriptions of the following functions:

• SmFsCreateDir

• SmFsCloseFile

• SmFsCalcFree

• SmFsCreateFile

• SmFsDeleteFile

• SmFsFindFile

• SmFsFindFileClose

• SmFsFindFileInit

• SmFsGetFileAttr

• SmFsGetOpenFileAttr

• SmFsOpenFile

• SmFsReadFile

• SmFsRenameFile

• SmFsWriteFile

SmFsCreateDir

Allocates SRAM memory and a directory entry for a directory.

Synopsis

int SmFsCreateDir(const char * name,

unsigned int entries);

Return value

Returns 0 for success or an error condition.

SmFsCloseFile

Close the file by removing it from the file descriptor table.

Synopsis

int SmFsCloseFile( SMFS_HANDLE fh);

Return value

Returns 0 or an error condition.

SmFsCalcFree

Synopsis

unsigned int SmFsCalcFree( void );

Return value

Returns amount of free memory (in bytes) in the file system.

SmFsCreateFile

Allocates SRAM memory and a directory entry for a file. Once a file has been created, its size can not be changed.

Synopsis

int SmFsCreateFile(const char * name,
unsigned int len);

Return value

Returns 0 for success or an error condition.

SmFsDeleteFile

Deletes a file from secure memory by removing the directory entry and zeroing out its data area.

Synopsis

int SmFsDeleteFile(const char * name);

Return value

Returns 0 or an error condition.

SmFsFindFile

Fetch name of next directory entry from file search context.

Synopsis

int SmFsFindFile( int sh,
    char * name,
    unsigned int size
);

Return value

Returns 0 or an error condition.

SmFsFindFileClose

Close a file search context.

Synopsis

int SmFsFindFileClose( int sh);

Return value

Returns 0 or an error condition.

SmFsFindFileInit

Creates a file iteration context.

Wild cards are:

? - match any character

* - match many characters

Synopsis

int SmFsFindFileInit(

    int *sh,
    const char * path,
    const char * pattern
);

Return value

Returns 0 or an error condition.

SmFsGetFileAttr

Get attributes of an open file. Returns an attributes structure for the unopen file ‘name’.

Synopsis

int SmFsGetFileAttr( const char * name,
SmFsAttr * a);

Return value

Returns 0 or an error condition.

SmFsGetOpenFileAttr

Returns an attribute structure for the open file ‘name’.

Synopsis

int SmFsGetOpenFileAttr( SMFS_HANDLE fh,
SmFSAttr * a);

Return value

Returns 0 or an error condition.

SmFsOpenFile

Finds the file and creates an entry for it in the file descriptor table. The table index returned in ‘fh’ and is used by other file functions.

Synopsis

int SmFsOpenFile( SMFS_HANDLE * fh,,
const char * name,);

Return value

Returns 0 or an error condition.

SmFsReadFile

Reads data from file.

Synopsis

int SmFsReadFile( SMFS_HANDLE fh,
unsigned int offset,
char *buf,
unsigned int bc);

Return value

Returns 0 or an error condition.

SmFsRenameFile

Renames a file.

Synopsis

int SmFsRenameFile( const char * oldName,
       const char * newName
      );

Return value

Returns 0 or an error condition.

SmFsWriteFile

Write data to file.

Synopsis

int SmFsWriteFile( SMFS_HANDLE fh,
unsigned int offset,
char *buf,unsigned int bc);

Return value

Returns 0 or an error condition.