diff options
Diffstat (limited to 'erts/doc/src/erl_ext_dist.xml')
| -rw-r--r-- | erts/doc/src/erl_ext_dist.xml | 163 |
1 files changed, 77 insertions, 86 deletions
diff --git a/erts/doc/src/erl_ext_dist.xml b/erts/doc/src/erl_ext_dist.xml index 4f799f8f34..b7090d0472 100644 --- a/erts/doc/src/erl_ext_dist.xml +++ b/erts/doc/src/erl_ext_dist.xml @@ -5,7 +5,7 @@ <header> <copyright> <year>2007</year> - <year>2016</year> + <year>2017</year> <holder>Ericsson AB, All Rights Reserved</holder> </copyright> <legalnotice> @@ -51,7 +51,7 @@ term into the external format. To convert binary data encoding to a term, the BIF <seealso marker="erts:erlang#binary_to_term/1"> - <c>erlang:binary_to_term/1</c>c></seealso> is used. + <c>erlang:binary_to_term/1</c></seealso> is used. </p> <p> The distribution does this implicitly when sending messages across @@ -119,27 +119,18 @@ <tcaption>Compressed Data Format when Expanded</tcaption></table> <marker id="utf8_atoms"/> <note> - <p>As from ERTS 5.10 (OTP R16) support - for UTF-8 encoded atoms has been introduced in the external format. - However, only characters that can be encoded using Latin-1 (ISO-8859-1) - are currently supported in atoms. The support for UTF-8 encoded atoms - in the external format has been implemented to be able to support - all Unicode characters in atoms in <em>some future release</em>. - Until full Unicode support for atoms has been introduced, - it is an <em>error</em> to pass atoms containing - characters that cannot be encoded in Latin-1, and <em>the behavior is - undefined</em>.</p> - <p>When distribution flag <seealso marker="erl_dist_protocol#dflags"> - <c>DFLAG_UTF8_ATOMS</c></seealso> has been exchanged between both nodes - in the <seealso marker="erl_dist_protocol#distribution_handshake"> - distribution handshake</seealso>, all atoms in the distribution header - are encoded in UTF-8, otherwise in Latin-1. The two - new tags <seealso marker="#ATOM_UTF8_EXT"><c>ATOM_UTF8_EXT</c></seealso> - and <seealso marker="#SMALL_ATOM_UTF8_EXT"> - <c>SMALL_ATOM_UTF8_EXT</c></seealso> - are only used if the distribution flag <c>DFLAG_UTF8_ATOMS</c> has - been exchanged between nodes, or if an atom containing characters - that cannot be encoded in Latin-1 is encountered.</p> + <p>As from ERTS 9.0 (OTP 20), atoms may contain any Unicode + characters and are always encoded using the UTF-8 external formats + <seealso marker="#ATOM_UTF8_EXT"><c>ATOM_UTF8_EXT</c></seealso> + or <seealso marker="#SMALL_ATOM_UTF8_EXT"><c>SMALL_ATOM_UTF8_EXT</c></seealso>. + The old Latin-1 formats <seealso marker="#ATOM_EXT"><c>ATOM_EXT</c></seealso> + and <seealso marker="#SMALL_ATOM_EXT"><c>SMALL_ATOM_EXT</c></seealso> + are deprecated and are only kept for backward + compatibility when decoding terms encoded by older nodes.</p> + <p>Support for UTF-8 encoded atoms in the external format has been + available since ERTS 5.10 (OTP R16). This abillity allows such old nodes + to decode, store and encode any Unicode atoms received from a new OTP 20 + node.</p> <p>The maximum number of allowed characters in an atom is 255. In the UTF-8 case, each character can need 4 bytes to be encoded.</p> </note> @@ -395,28 +386,6 @@ </section> <section> - <marker id="ATOM_EXT"/> - <title>ATOM_EXT</title> - <table align="left"> - <row> - <cell align="center">1</cell> - <cell align="center">2</cell> - <cell align="center">Len</cell> - </row> - <row> - <cell align="center"><c>100</c></cell> - <cell align="center"><c>Len</c></cell> - <cell align="center"><c>AtomName</c></cell> - </row> - <tcaption>ATOM_EXT</tcaption></table> - <p> - An atom is stored with a 2 byte unsigned length in big-endian order, - followed by <c>Len</c> numbers of 8-bit Latin-1 characters that forms - the <c>AtomName</c>. The maximum allowed value for <c>Len</c> is 255. - </p> - </section> - - <section> <marker id="REFERENCE_EXT"/> <title>REFERENCE_EXT</title> <table align="left"> @@ -437,8 +406,8 @@ Encodes a reference object (an object generated with <seealso marker="erlang:make_ref/0">erlang:make_ref/0</seealso>). The <c>Node</c> term is an encoded atom, that is, - <seealso marker="#ATOM_EXT"><c>ATOM_EXT</c></seealso>, - <seealso marker="#SMALL_ATOM_EXT"><c>SMALL_ATOM_EXT</c></seealso>, or + <seealso marker="#ATOM_UTF8_EXT"><c>ATOM_UTF8_EXT</c></seealso>, + <seealso marker="#SMALL_ATOM_UTF8_EXT"><c>SMALL_ATOM_UTF8_EXT</c></seealso>, or <seealso marker="#ATOM_CACHE_REF"><c>ATOM_CACHE_REF</c></seealso>. The <c>ID</c> field contains a big-endian unsigned integer, but <em>is to be regarded as uninterpreted data</em>, @@ -777,39 +746,6 @@ </section> <section> - <marker id="SMALL_ATOM_EXT"/> - <title>SMALL_ATOM_EXT</title> - <table align="left"> - <row> - <cell align="center">1</cell> - <cell align="center">1</cell> - <cell align="center">Len</cell> - </row> - <row> - <cell align="center"><c>115</c></cell> - <cell align="center"><c>Len</c></cell> - <cell align="center"><c>AtomName</c></cell> - </row> - <tcaption>SMALL_ATOM_EXT</tcaption></table> - <p> - An atom is stored with a 1 byte unsigned length, - followed by <c>Len</c> numbers of 8-bit Latin-1 characters that - forms the <c>AtomName</c>. Longer atoms can be represented - by <seealso marker="#ATOM_EXT"><c>ATOM_EXT</c></seealso>. - </p> - <note> - <p> - <c>SMALL_ATOM_EXT</c> was introduced in ERTS 5.7.2 and - require an exchange of distribution flag - <seealso marker="erl_dist_protocol#dflags"> - <c>DFLAG_SMALL_ATOM_TAGS</c></seealso> in the - <seealso marker="erl_dist_protocol#distribution_handshake"> - distribution handshake</seealso>. - </p> - </note> - </section> - - <section> <marker id="FUN_EXT"/> <title>FUN_EXT</title> <table align="left"> @@ -843,8 +779,8 @@ <tag><c>Module</c></tag> <item> <p>Encoded as an atom, using - <seealso marker="#ATOM_EXT"><c>ATOM_EXT</c></seealso>, - <seealso marker="#SMALL_ATOM_EXT"><c>SMALL_ATOM_EXT</c></seealso>, + <seealso marker="#ATOM_UTF8_EXT"><c>ATOM_UTF8_EXT</c></seealso>, + <seealso marker="#SMALL_ATOM_UTF8_EXT"><c>SMALL_ATOM_UTF8_EXT</c></seealso>, or <seealso marker="#ATOM_CACHE_REF"> <c>ATOM_CACHE_REF</c></seealso>. This is the module that the fun is implemented in. @@ -938,8 +874,8 @@ <tag><c>Module</c></tag> <item> <p>Encoded as an atom, using - <seealso marker="#ATOM_EXT"><c>ATOM_EXT</c></seealso>, - <seealso marker="#SMALL_ATOM_EXT"><c>SMALL_ATOM_EXT</c></seealso>, + <seealso marker="#ATOM_EXT"><c>ATOM_UTF8_EXT</c></seealso>, + <seealso marker="#SMALL_ATOM_EXT"><c>SMALL_ATOM_UTF8_EXT</c></seealso>, or <seealso marker="#ATOM_CACHE_REF"> <c>ATOM_CACHE_REF</c></seealso>. Is the module that the fun is implemented in. @@ -1001,8 +937,8 @@ </p> <p> <c>Module</c> and <c>Function</c> are atoms - (encoded using <seealso marker="#ATOM_EXT"><c>ATOM_EXT</c></seealso>, - <seealso marker="#SMALL_ATOM_EXT"><c>SMALL_ATOM_EXT</c></seealso>, or + (encoded using <seealso marker="#ATOM_EXT"><c>ATOM_UTF8_EXT</c></seealso>, + <seealso marker="#SMALL_ATOM_EXT"><c>SMALL_ATOM_UTF8_EXT</c></seealso>, or <seealso marker="#ATOM_CACHE_REF"><c>ATOM_CACHE_REF</c></seealso>). </p> <p> @@ -1114,6 +1050,61 @@ in the beginning of this section. </p> </section> + + <section> + <marker id="ATOM_EXT"/> + <title>ATOM_EXT (deprecated)</title> + <table align="left"> + <row> + <cell align="center">1</cell> + <cell align="center">2</cell> + <cell align="center">Len</cell> + </row> + <row> + <cell align="center"><c>100</c></cell> + <cell align="center"><c>Len</c></cell> + <cell align="center"><c>AtomName</c></cell> + </row> + <tcaption>ATOM_EXT</tcaption></table> + <p> + An atom is stored with a 2 byte unsigned length in big-endian order, + followed by <c>Len</c> numbers of 8-bit Latin-1 characters that forms + the <c>AtomName</c>. The maximum allowed value for <c>Len</c> is 255. + </p> + </section> + + <section> + <marker id="SMALL_ATOM_EXT"/> + <title>SMALL_ATOM_EXT (deprecated)</title> + <table align="left"> + <row> + <cell align="center">1</cell> + <cell align="center">1</cell> + <cell align="center">Len</cell> + </row> + <row> + <cell align="center"><c>115</c></cell> + <cell align="center"><c>Len</c></cell> + <cell align="center"><c>AtomName</c></cell> + </row> + <tcaption>SMALL_ATOM_EXT</tcaption></table> + <p> + An atom is stored with a 1 byte unsigned length, + followed by <c>Len</c> numbers of 8-bit Latin-1 characters that + forms the <c>AtomName</c>. + </p> + <note> + <p> + <c>SMALL_ATOM_EXT</c> was introduced in ERTS 5.7.2 and + require an exchange of distribution flag + <seealso marker="erl_dist_protocol#dflags"> + <c>DFLAG_SMALL_ATOM_TAGS</c></seealso> in the + <seealso marker="erl_dist_protocol#distribution_handshake"> + distribution handshake</seealso>. + </p> + </note> + </section> + </chapter> |