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NAME

       erl_marshal - Encoding and Decoding of Erlang terms

DESCRIPTION

       This module contains functions for encoding Erlang terms into a sequence of bytes, and for
       decoding Erlang terms from a sequence of bytes.

EXPORTS

       int erl_compare_ext(bufp1, bufp2)

              Types:

                 unsigned char *bufp1,*bufp2;

              This function compares two encoded terms.

              bufp1 is a buffer containing an encoded Erlang term term1.

              bufp2 is a buffer containing an encoded Erlang term term2.

              The function returns 0 if the terms are equal, -1 if term1 is less than term2, or 1
              if term2 is less than term1.

       ETERM *erl_decode(bufp)
       ETERM *erl_decode_buf(bufpp)

              Types:

                 unsigned char *bufp;
                 unsigned char **bufpp;

              erl_decode()  and  erl_decode_buf()  decode the contents of a buffer and return the
              corresponding Erlang term. erl_decode_buf() provides a simple mechanism for dealing
              with several encoded terms stored consecutively in the buffer.

              bufp is a pointer to a buffer containing one or more encoded Erlang terms.

              bufpp  is  the  address  of  a  buffer  pointer.  The  buffer  contains one or more
              consecutively   encoded   Erlang   terms.   Following   a   successful   call    to
              erl_decode_buf(), bufpp will be updated so that it points to the next encoded term.

              erl_decode()  returns  an  Erlang  term  corresponding  to  the contents of bufp on
              success, or NULL on failure. erl_decode_buf() returns an Erlang term  corresponding
              to  the first of the consecutive terms in bufpp and moves bufpp forward to point to
              the next term in the buffer. On failure, each of the functions returns NULL.

       int erl_encode(term, bufp)
       int erl_encode_buf(term, bufpp)

              Types:

                 ETERM *term;
                 unsigned char *bufp;
                 unsigned char **bufpp;

              erl_encode() and erl_encode_buf() encode Erlang  terms  into  external  format  for
              storage  or transmission. erl_encode_buf() provides a simple mechanism for encoding
              several terms consecutively in the same buffer.

              term is an Erlang term to be encoded.

              bufp is a pointer to a buffer containing one or more encoded Erlang terms.

              bufpp is a pointer to a pointer to a buffer containing one  or  more  consecutively
              encoded  Erlang  terms. Following a successful call to erl_encode_buf(), bufpp will
              be updated so that it points to the position for the next encoded term.

              These functions returns the number  of  bytes  written  to  buffer  if  successful,
              otherwise returns 0.

              Note  that  no  bounds  checking  is  done  on  the  buffer.  It  is  the  caller's
              responsibility to make sure that the buffer is large enough  to  hold  the  encoded
              terms.  You  can  either use a static buffer that is large enough to hold the terms
              you expect to need in your program, or use erl_term_len() to  determine  the  exact
              requirements for a given term.

              The  following  can help you estimate the buffer requirements for a term. Note that
              this information is implementation specific, and may change in future versions.  If
              you are unsure, use erl_term_len().

              Erlang terms are encoded with a 1 byte tag that identifies the type of object, a 2-
              or 4-byte length field, and then the data itself. Specifically:

                Tuples:
                  need 5 bytes, plus the space for each element.

                Lists:
                  need 5 bytes, plus the space for each element, and 1 additional  byte  for  the
                  empty list at the end.

                Strings and atoms:
                  need  3  bytes,  plus  1  byte  for  each  character  (the terminating 0 is not
                  encoded). Really long strings (more than 64k characters) are encoded as  lists.
                  Atoms cannot contain more than 256 characters.

                Integers:
                  need 5 bytes.

                Characters:
                  (integers < 256) need 2 bytes.

                Floating point numbers:
                  need 32 bytes.

                Pids:
                  need 10 bytes, plus the space for the node name, which is an atom.

                Ports and Refs:
                  need 6 bytes, plus the space for the node name, which is an atom.

              The  total space required will be the result calculated from the information above,
              plus 1 additional byte for a version identifier.

       int erl_ext_size(bufp)

              Types:

                 unsigned char *bufp;

              This function returns the number of elements in an encoded term.

       unsigned char erl_ext_type(bufp)

              Types:

                 unsigned char *bufp;

              This function identifies and returns the type of Erlang term encoded in  a  buffer.
              It will skip a trailing magic identifier. Returns 0 if the type can't be determined
              or one of

                * ERL_INTEGER

                * ERL_ATOM

                * ERL_PID /* Erlang process identifier */

                * ERL_PORT

                * ERL_REF /* Erlang reference */

                * ERL_EMPTY_LIST

                * ERL_LIST

                * ERL_TUPLE

                * ERL_FLOAT

                * ERL_BINARY

                * ERL_FUNCTION

       unsigned char *erl_peek_ext(bufp, pos)

              Types:

                 unsigned char *bufp;
                 int pos;

              This function is used for stepping over one or more encoded terms in a  buffer,  in
              order to directly access a later term.

              bufp is a pointer to a buffer containing one or more encoded Erlang terms.

              pos indicates how many terms to step over in the buffer.

              The  function returns a pointer to a sub-term that can be used in a subsequent call
              to erl_decode() in order to retrieve the term at that  position.  If  there  is  no
              term, or pos would exceed the size of the terms in the buffer, NULL is returned.

       int erl_term_len(t)

              Types:

                 ETERM *t;

              This  function  determines  the  buffer  space that would be needed by t if it were
              encoded into Erlang external format by erl_encode().

              The size in bytes is returned.