Disk ARchive  2.4.2
Public Member Functions | Protected Member Functions
libdar::tronconneuse Class Reference

this is a partial implementation of the generic_file interface to cypher/decypher data block by block. More...

#include <tronconneuse.hpp>

Inherits libdar::generic_file.

Inherited by libdar::crypto_sym.

List of all members.

Public Member Functions

 tronconneuse (U_32 block_size, generic_file &encrypted_side, bool no_initial_shift, const archive_version &reading_ver)
 This is the constructor.
 tronconneuse (const tronconneuse &ref)
 copy constructor
const tronconneuseoperator= (const tronconneuse &ref)
 assignment operator
virtual ~tronconneuse ()
 destructor
bool skip (const infinint &pos)
 inherited from generic_file
bool skip_to_eof ()
 inherited from generic_file
bool skip_relative (S_I x)
 inherited from generic_file
infinint get_position ()
 inherited from generic_file
void write_end_of_file ()
 in write_only mode indicate that end of file is reached
void set_initial_shift (const infinint &x)
 this method to modify the initial shift. This overrides the constructor "no_initial_shift" of the constructor
void set_callback_trailing_clear_data (infinint(*call_back)(generic_file &below, const archive_version &reading_ver))

Protected Member Functions

virtual U_32 encrypted_block_size_for (U_32 clear_block_size)=0
 defines the size necessary to encrypt a given amount of clear data
virtual U_32 clear_block_allocated_size_for (U_32 clear_block_size)=0
 it may be necessary by the inherited class have few more bytes allocated after the clear data given for encryption
virtual U_32 encrypt_data (const infinint &block_num, const char *clear_buf, const U_32 clear_size, const U_32 clear_allocated, char *crypt_buf, U_32 crypt_size)=0
 this method encrypts the clear data given
virtual U_32 decrypt_data (const infinint &block_num, const char *crypt_buf, const U_32 crypt_size, char *clear_buf, U_32 clear_size)=0
 this method decyphers data

Detailed Description

this is a partial implementation of the generic_file interface to cypher/decypher data block by block.

This class is a pure virtual one, as several calls have to be defined by inherited classes

tronconneuse is either read_only or write_only, read_write is not allowed. The openning mode is defined by encrypted_side's mode. In write_only no skip() is allowed, writing is sequential from the beginning of the file to the end (like writing to a pipe). In read_only all skip() functions are available.

Definition at line 63 of file tronconneuse.hpp.


Constructor & Destructor Documentation

libdar::tronconneuse::tronconneuse ( U_32  block_size,
generic_file encrypted_side,
bool  no_initial_shift,
const archive_version reading_ver 
)

This is the constructor.

Parameters:
[in]block_sizeis the size of block encryption (the size of clear data encrypted toghether).
[in]encrypted_sidewhere encrypted data are read from or written to.
[in]no_initial_shiftassume that no unencrypted data is located at the begining of the underlying file, else this is the position of the encrypted_side at the time of this call that is used as initial_shift
[in]reading_verversion of the archive format
Note:
that encrypted_side is not owned and destroyed by tronconneuse, it must exist during all the life of the tronconneuse object, and is not destroyed by the tronconneuse's destructor

Member Function Documentation

virtual U_32 libdar::tronconneuse::clear_block_allocated_size_for ( U_32  clear_block_size) [protected, pure virtual]

it may be necessary by the inherited class have few more bytes allocated after the clear data given for encryption

Parameters:
[in]clear_block_sizeis the size in byte of the clear data that will be asked to encrypt.
Returns:
the requested allocated buffer size (at least the size of the clear data).
Note:
when giving clear buffer of data of size "clear_block_size" some inherited class may requested that a bit more of data must be allocated. this is to avoid copying data when the algorithm needs to add some data after the clear data before encryption.

Implemented in libdar::crypto_sym.

virtual U_32 libdar::tronconneuse::decrypt_data ( const infinint block_num,
const char *  crypt_buf,
const U_32  crypt_size,
char *  clear_buf,
U_32  clear_size 
) [protected, pure virtual]

this method decyphers data

Parameters:
[in]block_numblock number of the data to decrypt.
[in]crypt_bufpointer to the first byte of encrypted data.
[in]crypt_sizesize of encrypted data to decrypt.
[in,out]clear_bufpointer where to put clear data.
[in]clear_sizeallocated size of clear_buf.
Returns:
is the amount of data put in clear_buf (<= clear_size)

Implemented in libdar::crypto_sym.

virtual U_32 libdar::tronconneuse::encrypt_data ( const infinint block_num,
const char *  clear_buf,
const U_32  clear_size,
const U_32  clear_allocated,
char *  crypt_buf,
U_32  crypt_size 
) [protected, pure virtual]

this method encrypts the clear data given

Parameters:
block_numis the number of the block to which correspond the given data, This is an informational field for inherited classes.
[in]clear_bufpoints to the first byte of clear data to encrypt.
[in]clear_sizeis the length in byte of data to encrypt.
[in]clear_allocatedis the size of the allocated memory (modifiable bytes) in clear_buf: clear_block_allocated_size_for(clear_size)
[in,out]crypt_bufis the area where to put corresponding encrypted data.
[in]crypt_sizeis the allocated memory size for crypt_buf: encrypted_block_size_for(clear_size)
Returns:
is the amount of data put in crypt_buf (<= crypt_size).
Note:
it must respect that : returned value = encrypted_block_size_for(clear_size argument)

Implemented in libdar::crypto_sym.

virtual U_32 libdar::tronconneuse::encrypted_block_size_for ( U_32  clear_block_size) [protected, pure virtual]

defines the size necessary to encrypt a given amount of clear data

Parameters:
[in]clear_block_sizeis the size of the clear block to encrypt.
Returns:
the size of the memory to allocate to receive corresponding encrypted data.
Note:
this implies that encryption algorithm must always generate a fixed size encrypted block of data for a given fixed size block of data. However, the size of the encrypted block of data may differ from the size of the clear block of data

Implemented in libdar::crypto_sym.

void libdar::tronconneuse::set_callback_trailing_clear_data ( infinint(*)(generic_file &below, const archive_version &reading_ver)  call_back) [inline]

let the caller give a callback function that given a generic_file with cyphered data, is able to return the offset of the first clear byte located *after* all the cyphered data, this callback function is used (if defined by the following method), when reaching End of File.

Definition at line 112 of file tronconneuse.hpp.

void libdar::tronconneuse::write_end_of_file ( ) [inline]

in write_only mode indicate that end of file is reached

this call must be called in write mode to purge the internal cache before deleting the object (else some data may be lost) no further write call is allowed

Note:
this call cannot be used from the destructor, because it relies on pure virtual methods

Definition at line 101 of file tronconneuse.hpp.

References libdar::generic_file::is_terminated().


The documentation for this class was generated from the following file:
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