path: root/PORTING

It is my intention to make migrating code using one version of GMime
to another as easy as I can and so for the most part, I will try not
to break API/ABI compatability between versions, however this isn't
always easy to do.

This document is intended to help developers port their application(s)
from one version of GMime to another. For each new major release, I
will attempt to list the main things to watch out for when migrating
to the new release from the prior version.


Porting from GMime 2.4 to GMime 2.6
-----------------------------------

After releasing GMime 2.4, it was discovered that
g_mime_stream_length() still returned ssize_t which, on 32bit systems,
meant that the function was useless if the actual stream was larger
than 2GB (which could happen if GMime was built with large file
support).

As I fixed this, I also found some API inconsistencies which I felt I
might as well fix up since I had to break API/ABI compatibility with
2.4 anyway.

Most notable in GMime 2.6 is the lack of GMimeSession which has been
dropped in favor of a much simpler callback
mechanism. GMimeCipherContexts constructors now take a
password_request callback function rather than forcing you to subclass
GMimeSession to get this functionality.

Other API changes include:

- GMimeBestEncoding has been renamed to GMimeEncodingConstraint

- GMimeSignatureValidity has been dropped in favor of
  GMimeSignatureList which is simply a collection of signatures.

- GMimeSigner has been replaced by GMimeSignature and GMimeCertificate
  which added a number of new fields and accessors making it much more
  complete.

- GMimeCipherContext has been renamed to GMimeCryptoContext and the
  method names for this class have also been renamed in a similar
  fashion.

- g_mime_crypto_context_encrypt() now takes a digest algorithm
  argument which is used when the 'sign' argument is TRUE.

- g_mime_multipart_encrypted_encrypt() also now takes a digest
  algorithm argument which it passes along to
  g_mime_crypto_context_encrypt().

- g_mime_crypto_context_decrypt() now returns a GMimeDecryptResult
  which contains a list of signatures (if signed), a list of
  recipients that the stream had been encrypted to, and also the
  cipher and digest algorithms used.

- g_mime_multipart_encrypted_decrypt() no longer caches the decrypted
  part and also now takes a GMimeSignatureList** output argument
  which it sets in place of having to call
  g_mime_multipart_encrypted_get_signature_validity() afterward.

For convenience, GMime 2.6 source packages include a shell-script to
aid in porting applications using GMime 2.4 to the 2.6 API. You can
find this script under the tools/ directory, named
`gmime-port-2-4-to-2-6.sh'.


Porting from GMime 2.2 to GMime 2.4
-----------------------------------

GMime 2.4 has had a number of API changes since GMime 2.2. To start,
ALL public APIs that used to use off_t in GMime 2.2 now use gint64 so
that the API and ABI do not change based on whether or not large file
support is enabled.

In addition, all of the functions marked as deprecated in 2.0 and 2.2
were removed (usually they had equivalent functionality in a parent
class).

Many functions have also been renamed for better clarity and/or
consistency. For convenience, GMime 2.4 source packages include a
shell-script to aid in porting applications using GMime 2.2 (should
work for most GMime 2.0 applications as well) to the 2.4 API. You can
find this script under the tools/ directory, named
`gmime-port-2-2-to-2-4.sh'.

This script won't fix everything, but it should help quite a bit.

Beyond that, a few methods have changed in other ways:

- g_mime_cipher_context_sign() still returns int, but if the value
  isn't -1 (failure), then it will represent a GMimeCipherHash that it
  used for signing. This is useful, for example, when the requested
  hash was GMIME_CIPHER_HASH_DEFAULT.

- g_mime_cipher_context_decrypt() now returns a GMimeSignatureValidty
  on success and NULL on failure. This is needed in case the encrypted
  stream was also signed.

- g_mime_multipart_encrypted_encrypt() now takes a boolean 'sign'
  argument to allow the caller to request encrypting and signing in a
  single pass.

Several structs have also been rewritten to subclass GObject like
GMimeContentType and GMimeContentDisposition as well as
InternetAddress and InternetAddressList.

Not only have InternetAddress and InternetAddressList been ported to
GObject, but they have also undergone other design
changes. InternetAddress is now a base class for
InternetAddressMailbox and InternetAddressGroup, meaning that
InternetAddress no longer contains a union for group/addr fields.

All functions that return a GObject have been changed to not add a ref
to the object returned, meaning that it is no longer necessary to call
g_object_unref() on MIME parts returned from functions like
g_mime_message_get_mime_part() or g_mime_multipart_get_part(). This
was done to be more consistent with the Gtk+ API.


Porting from GMime 2.0 to GMime 2.2
-----------------------------------

Note: GMime 2.2 is both API and ABI compatible with GMime 2.0 meaning
that any program written for GMime 2.0 will compile fine with GMime
2.2 and any program linked against GMime 2.0's libraries will also
work with GMime 2.2's libraries.

Most of the changes made between 2.0 and 2.2 were internal but there
are a few API changes you should be aware of (as these interfaces will
be deprecated in some future version, probably 3.0).

- g_mime_utils_8bit_header_decode() has been split into 2
functions. We now have g_mime_utils_header_decode_text() and
g_mime_utils_header_decode_phrase(). header_decode_text() no longer
requires encoded-words to be rfc822 atoms. header_decode_phrase() is
still strict in that encoded-words MUST be valid rfc822 atoms.

- g_mime_utils_8bit_header_encode() has been renamed to
g_mime_utils_header_encode_text() to be more clear as to what type of
header this is supposed to encode. If you haven't guessed, this
function is for encoding rfc822 'text' headers (such as Subject).

- g_mime_utils_8bit_header_encode_phrase() has been renamed to
g_mime_utils_header_encode_phrase() mostly for consistancy with the
previous 2 changes.

- g_mime_charset_name() has been renamed to
g_mime_charset_iconv_name() for clarity.

- g_mime_charset_locale_name() has been renamed to
g_mime_locale_charset(). Hmmm, was this a bad rename?

- g_mime_cipher_context_verify() no longer returns a
GMimeCipherValidity, instead it returns a GMimeSignatureValidity which
is far more useful. Never fear, you may still use the
GMimeCipherValidity APIs for the time being - they work fine given a
GMimeSignatureValidity structure.

- g_mime_multipart_signed_verify() also now returns a
GMimeSignatureValidity structure rather than a GMimeCipherValidity
structure. See changes to g_mime_cipher_context_verify() for details.


Porting from GMime 1.0 to GMime 2.0
-----------------------------------

The major change here is that I've dropped my own base object class
and have replaced it with GObject from glib-2.0. This should be a
pleasant change since you (the developer) will now be able to do many
more things such as setting arbitrary data on all GMime objects. For
additional information about GObject, please see the GObject Reference
Manual at http://developer.gnome.org/doc/API/2.0/gobject/

- The first thing you need to know is that any function returning a
non-const pointer to any object /must/ be unref'd when you are done
with it. Since all objects in GMime now subclass GObject, you may
safely use g_object_unref() (GMimeStream's may also be unref'd
using g_mime_stream_unref(), but either way is fine).

Don't forget that g_mime_part_get_content_object() returns a
ref-counted GMimeDataWrapper object now, and so you /must/ unref it
when you have finished using it. You must also remember to unref any
GMimeDataWrapper object that you /set/ on a GMimePart using
g_mime_part_set_content_object() as the GMimePart will now ref the
content object that you set on it.

- GMimeMultipart is a new class which is to be used for all multipart
MIME parts rather than GMimePart (as in 1.0). There are also some
subclasses of GMimeMultipart for other things.

- g_mime_part_[g,s]et_boundary() have been removed (see above). You
must now create a GMimeMultipart object and use
g_mime_multipart_[g,s]et_boundary().

- g_mime_part_add_subpart() has been replaced with
g_mime_multipart_add_part().

- g_mime_part_foreach() has been replaced with
g_mime_multipart_foreach() and/or g_mime_message_foreach_part().

- g_mime_part_get_subpart_from_content_id() has been replaced with
g_mime_multipart_get_subpart_from_content_id().

- Another new class is GMimeMessagePart which is to be used for all
MIME parts containing an rfc822 message. All 1.0 GMimePart's
representing message/rfc822 parts (as well as message/news parts?)
need to be migrated over to be GMimeMessagePart objects.

- GMimeMessagePartial is another class meant for handling the
message/partial MIME type. All 1.0 GMimePart's holding data of this
type should be replaced with GMimeMessagePartial objects.

- g_mime_message_write_to_stream() and g_mime_part_write_to_stream()
functions have been consolidated into a virtual method. Replace calls
to these functions with g_mime_object_write_to_stream(). Note: while
g_mime_part_write_to_stream() and g_mime_message_write_to_stream()
still exist, it is suggested you migrate to
g_mime_object_write_to_stream(). Same goes for g_mime_part_to_string()
and g_mime_message_to_string().

- GMimeMessage's structure has changed a bit. You will not be able to
do message->header, instead you want to do ((GMimeObject *)
message)->header.

- g_mime_message_set_message_id() now takes a message_id argument
without the encapsulating <>'s (it now just takes the addr-spec
portion of the msg-id).

- GMimeFilterFrom has changed slightly, you will want to replace all
calls to g_mime_filter_from_new () with g_mime_filter_from_new
(GMIME_FILTER_FROM_MODE_DEFAULT) (GMIME_FILTER_FROM_MODE_DEFAULT is
equivalent to (int) 0).

- GMimeParser has had a number of API additions, but
g_mime_parser_construct_part() and g_mime_parser_construct_message()
still exist, however they no longer take a GMimeStream
argument. Instead, they take a GMimeParser object.



If you find more trouble spots when porting your code from one version
of GMime to a later version, please feel free to send me additional
notes to add to this porting document.

					-- fejj@gnome.org