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NAME

       ei - Routines for handling the Erlang binary term format.

DESCRIPTION

   Note:
       The support for VxWorks is deprecated as of OTP 22, and will be removed in OTP 23.

       The  library  ei contains macros and functions to encode and decode the Erlang binary term
       format.

       ei allows you to convert atoms, lists, numbers,  and  binaries  to  and  from  the  binary
       format.  This is useful when writing port programs and drivers. ei uses a given buffer, no
       dynamic memory (except ei_decode_fun()) and is often quite fast.

       ei also handles C-nodes, C-programs that talks Erlang distribution with Erlang  nodes  (or
       other  C-nodes)  using  the  Erlang  distribution  format.  The  difference between ei and
       erl_interface is that ei uses the binary format directly when sending and receiving terms.
       It  is  also  thread safe, and using threads, one process can handle multiple C-nodes. The
       erl_interface library is built on top of ei, but of legacy reasons, it does not allow  for
       multiple C-nodes. In general, ei is the preferred way of doing C-nodes.

       The decode and encode functions use a buffer and an index into the buffer, which points at
       the point where to encode and decode. The index is updated to point right after  the  term
       encoded/decoded.  No  checking  is  done  whether  the  term fits in the buffer or not. If
       encoding goes outside the buffer, the program can crash.

       All functions take two parameters:

         * buf is a pointer to the buffer where the binary data is or will be.

         * index is a pointer to an index into the buffer. This parameter is incremented with the
           size of the term decoded/encoded.

       The data is thus at buf[*index] when an ei function is called.

       All  encode  functions  assume  that  the buf and index parameters point to a buffer large
       enough for the data. To get the size of an encoded term, without encoding  it,  pass  NULL
       instead  of a buffer pointer. Parameter index is incremented, but nothing will be encoded.
       This is the way in ei to "preflight" term encoding.

       There are also encode functions that use a dynamic buffer. It is often more convenient  to
       use  these to encode data. All encode functions comes in two versions; those starting with
       ei_x use a dynamic buffer.

       All functions return 0 if successful, otherwise -1 (for example, if a term is not  of  the
       expected type, or the data to decode is an invalid Erlang term).

       Some  of  the  decode functions need a pre-allocated buffer. This buffer must be allocated
       large enough, and for non-compound types  the  ei_get_type()  function  returns  the  size
       required (notice that for strings an extra byte is needed for the NULL-terminator).

DATA TYPES

         erlang_char_encoding:

         typedef enum {
             ERLANG_ASCII = 1,
             ERLANG_LATIN1 = 2,
             ERLANG_UTF8 = 4
         } erlang_char_encoding;

           The  character  encodings used for atoms. ERLANG_ASCII represents 7-bit ASCII. Latin-1
           and UTF-8 are different extensions of 7-bit ASCII.  All  7-bit  ASCII  characters  are
           valid Latin-1 and UTF-8 characters. ASCII and Latin-1 both represent each character by
           one byte. An UTF-8 character can consist of 1-4 bytes. Notice that these constants are
           bit-flags and can be combined with bitwise OR.

EXPORTS

       int ei_decode_atom(const char *buf, int *index, char *p)

              Decodes  an  atom  from  the binary format. The NULL-terminated name of the atom is
              placed at p. At most MAXATOMLEN bytes can be placed in the buffer.

       int ei_decode_atom_as(const char *buf, int *index, char *p, int plen, erlang_char_encoding
       want, erlang_char_encoding* was, erlang_char_encoding* result)

              Decodes  an  atom  from  the binary format. The NULL-terminated name of the atom is
              placed in buffer at p of length plen bytes.

              The wanted string encoding is specified by want. The original encoding used in  the
              binary  format  (Latin-1  or  UTF-8) can be obtained from *was. The encoding of the
              resulting string (7-bit ASCII, Latin-1, or UTF-8) can  be  obtained  from  *result.
              Both  was and result can be NULL. *result can differ from want if want is a bitwise
              OR'd combination like ERLANG_LATIN1|ERLANG_UTF8 or if *result turns out to be  pure
              7-bit ASCII (compatible with both Latin-1 and UTF-8).

              This  function  fails  if  the  atom  is too long for the buffer or if it cannot be
              represented with encoding want.

              This function was introduced in Erlang/OTP R16 as part of a first step  to  support
              UTF-8 atoms.

       int ei_decode_bignum(const char *buf, int *index, mpz_t obj)

              Decodes  an  integer  in  the  binary  format  to  a GMP mpz_t integer. To use this
              function, the ei library must be configured and compiled to use the GMP library.

       int ei_decode_binary(const char *buf, int *index, void *p, long *len)

              Decodes a binary from the binary format. Parameter len is set to the actual size of
              the  binary.  Notice  that ei_decode_binary() assumes that there is enough room for
              the binary. The size required can be fetched by ei_get_type().

       int ei_decode_bitstring(const char  *buf,  int  *index,  const  char  **pp,  unsigned  int
       *bitoffsp, size_t *nbitsp)

              Decodes a bit string from the binary format.

                pp:
                  Either  NULL  or *pp returns a pointer to the first byte of the bit string. The
                  returned bit string is readable as long as the buffer  pointed  to  by  buf  is
                  readable and not written to.

                bitoffsp:
                  Either  NULL  or  *bitoffsp returns the number of unused bits in the first byte
                  pointed to by *pp. The value of *bitoffsp is between 0 and 7.  Unused  bits  in
                  the first byte are the most significant bits.

                nbitsp:
                  Either NULL or *nbitsp returns the length of the bit string in bits.

              Returns 0 if it was a bit string term.

              The  number  of  bytes  pointed  to  by  *pp,  which are part of the bit string, is
              (*bitoffsp + *nbitsp + 7)/8. If (*bitoffsp + *bitsp)%8 > 0 then only  (*bitoffsp  +
              *bitsp)%8  bits  of  the  last  byte are used. Unused bits in the last byte are the
              least significant bits.

              The values of unused bits in the first and last byte are undefined  and  cannot  be
              relied on.

              Number  of  bits  may  be  divisible  by  8,  which  means  a  binary  decodable by
              ei_decode_binary is also decodable by ei_decode_bitstring.

       int ei_decode_boolean(const char *buf, int *index, int *p)

              Decodes a boolean value from the binary format. A boolean is actually an atom, true
              decodes 1 and false decodes 0.

       int ei_decode_char(const char *buf, int *index, char *p)

              Decodes a char (8-bit) integer between 0-255 from the binary format. For historical
              reasons the returned integer is of type char.  Your  C  code  is  to  consider  the
              returned  value  to be of type unsigned char even if the C compilers and system can
              define char to be signed.

       int ei_decode_double(const char *buf, int *index, double *p)

              Decodes a double-precision (64-bit) floating point number from the binary format.

       int ei_decode_ei_term(const char* buf, int* index, ei_term* term)

              Decodes any term, or at least tries to. If the term pointed at  by  *index  in  buf
              fits  in the term union, it is decoded, and the appropriate field in term->value is
              set, and *index is incremented by the term size.

              The function returns 1 on successful decoding, -1 on error, and 0 if the term seems
              alright,  but  does  not  fit in the term structure. If 1 is returned, the index is
              incremented, and term contains the decoded term.

              The term structure contains the arity for a tuple  or  list,  size  for  a  binary,
              string,  or atom. It contains a term if it is any of the following: integer, float,
              atom, pid, port, or ref.

       int ei_decode_fun(const char *buf, int *index, erlang_fun *p)
       void free_fun(erlang_fun* f)

              Decodes a fun from the binary format. Parameter p is to be  NULL  or  point  to  an
              erlang_fun  structure. This is the only decode function that allocates memory. When
              the erlang_fun is no longer needed, it is to be freed with free_fun. (This  has  to
              do with the arbitrary size of the environment for a fun.)

       int ei_decode_list_header(const char *buf, int *index, int *arity)

              Decodes a list header from the binary format. The number of elements is returned in
              arity. The arity+1 elements follow (the last one is the tail of the list,  normally
              an empty list). If arity is 0, it is an empty list.

              Notice  that  lists  are encoded as strings if they consist entirely of integers in
              the range 0..255. This function do not decode such strings, use  ei_decode_string()
              instead.

       int ei_decode_long(const char *buf, int *index, long *p)

              Decodes a long integer from the binary format. If the code is 64 bits, the function
              ei_decode_long() is the same as ei_decode_longlong().

       int ei_decode_longlong(const char *buf, int *index, long long *p)

              Decodes a GCC long long or Visual C++ __int64  (64-bit)  integer  from  the  binary
              format. This function is missing in the VxWorks port.

       int ei_decode_map_header(const char *buf, int *index, int *arity)

              Decodes  a  map  header  from  the  binary format. The number of key-value pairs is
              returned in *arity. Keys and values follow in this order: K1, V1, K2, V2, ...,  Kn,
              Vn.  This  makes  a total of arity*2 terms. If arity is zero, it is an empty map. A
              correctly encoded map does not have duplicate keys.

       int ei_decode_pid(const char *buf, int *index, erlang_pid *p)

              Decodes a process identifier (pid) from the binary format.

       int ei_decode_port(const char *buf, int *index, erlang_port *p)

              Decodes a port identifier from the binary format.

       int ei_decode_ref(const char *buf, int *index, erlang_ref *p)

              Decodes a reference from the binary format.

       int ei_decode_string(const char *buf, int *index, char *p)

              Decodes a string from the binary format. A string in Erlang is a list  of  integers
              between  0  and  255. Notice that as the string is just a list, sometimes lists are
              encoded as strings by term_to_binary/1, even if it was not intended.

              The string is copied to p, and enough space must be allocated. The returned  string
              is NULL-terminated, so you must add an extra byte to the memory requirement.

       int ei_decode_term(const char *buf, int *index, void *t)

              Decodes a term from the binary format. The term is return in t as a ETERM*, so t is
              actually an ETERM** (see erl_eterm). The term is later to be deallocated.

          Note:
              This function is deprecated as of OTP 22 and will be removed  in  OTP  23  together
              with the old legacy erl_interface library (functions with prefix erl_).

       int ei_decode_trace(const char *buf, int *index, erlang_trace *p)

              Decodes an Erlang trace token from the binary format.

       int ei_decode_tuple_header(const char *buf, int *index, int *arity)

              Decodes  a  tuple  header,  the  number of elements is returned in arity. The tuple
              elements follow in order in the buffer.

       int ei_decode_ulong(const char *buf, int *index, unsigned long *p)

              Decodes an unsigned long integer from the binary format. If the code  is  64  bits,
              the function ei_decode_ulong() is the same as ei_decode_ulonglong().

       int ei_decode_ulonglong(const char *buf, int *index, unsigned long long *p)

              Decodes  a  GCC  unsigned long long or Visual C++ unsigned __int64 (64-bit) integer
              from the binary format. This function is missing in the VxWorks port.

       int ei_decode_version(const char *buf, int *index, int *version)

              Decodes the version magic number for the Erlang binary term format. It must be  the
              first token in a binary term.

       int ei_encode_atom(char *buf, int *index, const char *p)
       int ei_encode_atom_len(char *buf, int *index, const char *p, int len)
       int ei_x_encode_atom(ei_x_buff* x, const char *p)
       int ei_x_encode_atom_len(ei_x_buff* x, const char *p, int len)

              Encodes  an  atom  in  the  binary  format.  Parameter p is the name of the atom in
              Latin-1 encoding. Only up to MAXATOMLEN-1 bytes are encoded.  The  name  is  to  be
              NULL-terminated, except for the ei_x_encode_atom_len() function.

       int ei_encode_atom_as(char *buf, int *index, const char *p, erlang_char_encoding from_enc,
       erlang_char_encoding to_enc)
       int   ei_encode_atom_len_as(char   *buf,   int   *index,   const   char   *p,   int   len,
       erlang_char_encoding from_enc, erlang_char_encoding to_enc)
       int  ei_x_encode_atom_as(ei_x_buff*  x,  const  char  *p,  erlang_char_encoding  from_enc,
       erlang_char_encoding to_enc)
       int ei_x_encode_atom_len_as(ei_x_buff* x, const char  *p,  int  len,  erlang_char_encoding
       from_enc, erlang_char_encoding to_enc)

              Encodes  an  atom  in  the  binary format. Parameter p is the name of the atom with
              character encoding from_enc (ASCII, Latin-1, or UTF-8). The  name  must  either  be
              NULL-terminated or a function variant with a len parameter must be used.

              The encoding fails if p is not a valid string in encoding from_enc.

              Argument  to_enc  is  ignored. As from Erlang/OTP 20 the encoding is always done in
              UTF-8 which is readable by nodes as old as Erlang/OTP R16.

       int ei_encode_bignum(char *buf, int *index, mpz_t obj)
       int ei_x_encode_bignum(ei_x_buff *x, mpz_t obj)

              Encodes a GMP mpz_t integer to binary format. To use this function, the ei  library
              must be configured and compiled to use the GMP library.

       int ei_encode_binary(char *buf, int *index, const void *p, long len)
       int ei_x_encode_binary(ei_x_buff* x, const void *p, long len)

              Encodes a binary in the binary format. The data is at p, of len bytes length.

       int  ei_encode_bitstring(char  *buf,  int  *index,  const  char *p, size_t bitoffs, size_t
       nbits)
       int ei_x_encode_bitstring(ei_x_buff* x, const char *p, size_t bitoffs, size_t nbits)

              Encodes a bit string in the binary format.

              The data is at p. The length of the bit string is nbits  bits.  The  first  bitoffs
              bits of the data at p are unused. The first byte which is part of the bit string is
              p[bitoffs/8]. The bitoffs%8 most significant bits of the  first  byte  p[bitoffs/8]
              are unused.

              The  number of bytes which is part of the bit string is (bitoffs + nbits + 7)/8. If
              (bitoffs + nbits)%8 > 0 then only (bitoffs + nbits)%8 bits of  the  last  byte  are
              used. Unused bits in the last byte are the least significant bits.

              The values of unused bits are disregarded and does not need to be cleared.

       int ei_encode_boolean(char *buf, int *index, int p)
       int ei_x_encode_boolean(ei_x_buff* x, int p)

              Encodes a boolean value as the atom true if p is not zero, or false if p is zero.

       int ei_encode_char(char *buf, int *index, char p)
       int ei_x_encode_char(ei_x_buff* x, char p)

              Encodes  a  char  (8-bit)  as  an  integer  between 0-255 in the binary format. For
              historical reasons the integer argument is of type char. Your C code is to consider
              the  specified  argument  to  be  of type unsigned char even if the C compilers and
              system may define char to be signed.

       int ei_encode_double(char *buf, int *index, double p)
       int ei_x_encode_double(ei_x_buff* x, double p)

              Encodes a double-precision (64-bit) floating point number in the binary format.

              Returns -1 if the floating point number is not finite.

       int ei_encode_empty_list(char* buf, int* index)
       int ei_x_encode_empty_list(ei_x_buff* x)

              Encodes an empty list. It is often used at the tail of a list.

       int ei_encode_fun(char *buf, int *index, const erlang_fun *p)
       int ei_x_encode_fun(ei_x_buff* x, const erlang_fun* fun)

              Encodes a fun in the binary format. Parameter p points to an erlang_fun  structure.
              The  erlang_fun is not freed automatically, the free_fun is to be called if the fun
              is not needed after encoding.

       int ei_encode_list_header(char *buf, int *index, int arity)
       int ei_x_encode_list_header(ei_x_buff* x, int arity)

              Encodes a list header, with a specified arity.  The  next  arity+1  terms  are  the
              elements (actually its arity cons cells) and the tail of the list. Lists and tuples
              are encoded recursively, so that a list can contain another list or tuple.

              For example, to encode the list [c, d, [e | f]]:

              ei_encode_list_header(buf, &i, 3);
              ei_encode_atom(buf, &i, "c");
              ei_encode_atom(buf, &i, "d");
              ei_encode_list_header(buf, &i, 1);
              ei_encode_atom(buf, &i, "e");
              ei_encode_atom(buf, &i, "f");
              ei_encode_empty_list(buf, &i);

          Note:
              It may seem that there is no way to create a list without  knowing  the  number  of
              elements  in advance. But indeed there is a way. Notice that the list [a, b, c] can
              be written as [a | [b | [c]]]. Using this, a list can be written as conses.

              To encode a list, without knowing the arity in advance:

              while (something()) {
                  ei_x_encode_list_header(&x, 1);
                  ei_x_encode_ulong(&x, i); /* just an example */
              }
              ei_x_encode_empty_list(&x);

       int ei_encode_long(char *buf, int *index, long p)
       int ei_x_encode_long(ei_x_buff* x, long p)

              Encodes a long integer in the binary format. If the code is 64 bits,  the  function
              ei_encode_long() is the same as ei_encode_longlong().

       int ei_encode_longlong(char *buf, int *index, long long p)
       int ei_x_encode_longlong(ei_x_buff* x, long long p)

              Encodes  a  GCC  long  long  or  Visual  C++ __int64 (64-bit) integer in the binary
              format. This function is missing in the VxWorks port.

       int ei_encode_map_header(char *buf, int *index, int arity)
       int ei_x_encode_map_header(ei_x_buff* x, int arity)

              Encodes a map header, with a specified arity. The next arity*2 terms  encoded  will
              be  the  keys and values of the map encoded in the following order: K1, V1, K2, V2,
              ..., Kn, Vn.

              For example, to encode the map #{a => "Apple", b => "Banana"}:

              ei_x_encode_map_header(&x, 2);
              ei_x_encode_atom(&x, "a");
              ei_x_encode_string(&x, "Apple");
              ei_x_encode_atom(&x, "b");
              ei_x_encode_string(&x, "Banana");

              A correctly encoded map cannot have duplicate keys.

       int ei_encode_pid(char *buf, int *index, const erlang_pid *p)
       int ei_x_encode_pid(ei_x_buff* x, const erlang_pid *p)

              Encodes an Erlang process identifier (pid) in the binary format. Parameter p points
              to   an  erlang_pid  structure  (which  should  have  been  obtained  earlier  with
              ei_decode_pid()).

       int ei_encode_port(char *buf, int *index, const erlang_port *p)
       int ei_x_encode_port(ei_x_buff* x, const erlang_port *p)

              Encodes an Erlang port in the binary format. Parameter p points  to  a  erlang_port
              structure (which should have been obtained earlier with ei_decode_port()).

       int ei_encode_ref(char *buf, int *index, const erlang_ref *p)
       int ei_x_encode_ref(ei_x_buff* x, const erlang_ref *p)

              Encodes  an  Erlang  reference  in  the  binary  format.  Parameter  p  points to a
              erlang_ref   structure   (which   should   have   been   obtained   earlier    with
              ei_decode_ref()).

       int ei_encode_string(char *buf, int *index, const char *p)
       int ei_encode_string_len(char *buf, int *index, const char *p, int len)
       int ei_x_encode_string(ei_x_buff* x, const char *p)
       int ei_x_encode_string_len(ei_x_buff* x, const char* s, int len)

              Encodes  a  string  in  the  binary  format.  (A string in Erlang is a list, but is
              encoded as a character array in the binary format.)  The  string  is  to  be  NULL-
              terminated, except for the ei_x_encode_string_len() function.

       int ei_encode_term(char *buf, int *index, void *t)
       int ei_x_encode_term(ei_x_buff* x, void *t)

              Encodes  an ETERM, as obtained from erl_interface. Parameter t is actually an ETERM
              pointer. This function does not free the ETERM.

          Note:
              These functions are deprecated as of OTP 22 and will be removed in OTP 23  together
              with the old legacy erl_interface library (functions with prefix erl_).

       int ei_encode_trace(char *buf, int *index, const erlang_trace *p)
       int ei_x_encode_trace(ei_x_buff* x, const erlang_trace *p)

              Encodes  an  Erlang  trace  token  in  the  binary  format. Parameter p points to a
              erlang_trace  structure   (which   should   have   been   obtained   earlier   with
              ei_decode_trace()).

       int ei_encode_tuple_header(char *buf, int *index, int arity)
       int ei_x_encode_tuple_header(ei_x_buff* x, int arity)

              Encodes  a  tuple header, with a specified arity. The next arity terms encoded will
              be the elements of the tuple. Tuples and lists are encoded recursively, so  that  a
              tuple can contain another tuple or list.

              For example, to encode the tuple {a, {b, {}}}:

              ei_encode_tuple_header(buf, &i, 2);
              ei_encode_atom(buf, &i, "a");
              ei_encode_tuple_header(buf, &i, 2);
              ei_encode_atom(buf, &i, "b");
              ei_encode_tuple_header(buf, &i, 0);

       int ei_encode_ulong(char *buf, int *index, unsigned long p)
       int ei_x_encode_ulong(ei_x_buff* x, unsigned long p)

              Encodes  an unsigned long integer in the binary format. If the code is 64 bits, the
              function ei_encode_ulong() is the same as ei_encode_ulonglong().

       int ei_encode_ulonglong(char *buf, int *index, unsigned long long p)
       int ei_x_encode_ulonglong(ei_x_buff* x, unsigned long long p)

              Encodes a GCC unsigned long long or Visual C++ unsigned __int64 (64-bit) integer in
              the binary format. This function is missing in the VxWorks port.

       int ei_encode_version(char *buf, int *index)
       int ei_x_encode_version(ei_x_buff* x)

              Encodes  a version magic number for the binary format. Must be the first token in a
              binary term.

       int ei_get_type(const char *buf, const int *index, int *type, int *size)

              Returns the type in *type and size in *size of the encoded term.  For  strings  and
              atoms,  size  is  the  number of characters not including the terminating NULL. For
              binaries and bitstrings, *size is the number of bytes. For lists, tuples and  maps,
              *size  is the arity of the object. For other types, *size is 0. In all cases, index
              is left unchanged.

       int ei_init(void)

              Initialize the ei library. This function should be  called  once  (and  only  once)
              before  calling  any  other  functionality  in  the  ei  library. However, note the
              exception below.

              If the ei library is used together with the erl_interface  library,  this  function
              should  not  be called directly. It will be called by the erl_init() function which
              should be used to initialize the combination of the two libraries instead.

              On success zero is returned. On failure a posix error code is returned.

       int ei_print_term(FILE* fp, const char* buf, int* index)
       int ei_s_print_term(char** s, const char* buf, int* index)

              Prints a term, in clear text, to the file specified by fp, or the buffer pointed to
              by s. It tries to resemble the term printing in the Erlang shell.

              In  ei_s_print_term(),  parameter s is to point to a dynamically (malloc) allocated
              string of BUFSIZ bytes or a NULL pointer. The string can be reallocated (and *s can
              be  updated)  by  this  function  if the result is more than BUFSIZ characters. The
              string returned is NULL-terminated.

              The return value is the number of characters written to the file or string,  or  -1
              if buf[index] does not contain a valid term. Unfortunately, I/O errors on fp is not
              checked.

              Argument index is updated, that is,  this  function  can  be  viewed  as  a  decode
              function that decodes a term into a human-readable format.

       void ei_set_compat_rel(release_number)

              Types:

                 unsigned release_number;

              In  general,  the  ei  library is guaranteed to be compatible with other Erlang/OTP
              components that are 2 major releases older or newer than the ei library itself.

              Sometimes an exception to the above rule has to be made to make  new  features  (or
              even  bug  fixes) possible. A call to ei_set_compat_rel(release_number) sets the ei
              library in compatibility mode of OTP release release_number.

              The only useful value for release_number is currently 21. This will only be  useful
              and  have  an  effect  if  bit strings or export funs are received from a connected
              node. Before OTP 22, bit strings and export funs were not  supported  by  ei.  They
              were instead encoded using an undocumented fallback tuple format when sent from the
              emulator to ei:

                Bit string:
                  The term <<42, 1:1>> was encoded as {<<42, 128>>, 1}. The first element of  the
                  tuple  is  a  binary  and  the second element denotes how many bits of the last
                  bytes are part of the bit string. In this example only the most significant bit
                  of the last byte (128) is part of the bit string.

                Export fun:
                  The  term  fun lists:map/2 was encoded as {lists,map}. A tuple with the module,
                  function and a missing arity.

              If ei_set_compat_rel(21) is not called then a  connected  emulator  will  send  bit
              strings  and  export  funs correctly encoded. The functions ei_decode_bitstring and
              ei_decode_fun has to be used to decode such  terms.  Calling  ei_set_compat_rel(21)
              should  only  be  done  as  a workaround to keep an old implementation alive, which
              expects to receive the undocumented tuple formats for  bit  strings  and/or  export
              funs.

          Note:
              If  this  function  is called, it can only be called once and must be called before
              any other functions in the ei library are called.

       int ei_skip_term(const char* buf, int* index)

              Skips a term in the specified buffer;  recursively  skips  elements  of  lists  and
              tuples,  so that a full term is skipped. This is a way to get the size of an Erlang
              term.

              buf is the buffer.

              index is updated to point right after the term in the buffer.

          Note:
              This can be useful when you want to hold arbitrary terms: skip them  and  copy  the
              binary term data to some buffer.

              Returns 0 on success, otherwise -1.

       int ei_x_append(ei_x_buff* x, const ei_x_buff* x2)
       int ei_x_append_buf(ei_x_buff* x, const char* buf, int len)

              Appends data at the end of buffer x.

       int ei_x_format(ei_x_buff* x, const char* fmt, ...)
       int ei_x_format_wo_ver(ei_x_buff* x, const char *fmt, ... )

              Formats  a  term,  given  as a string, to a buffer. Works like a sprintf for Erlang
              terms. fmt contains a format string, with arguments like ~d, to insert  terms  from
              variables. The following formats are supported (with the C types given):

              ~a  An atom, char*
              ~c  A character, char
              ~s  A string, char*
              ~i  An integer, int
              ~l  A long integer, long int
              ~u  A unsigned long integer, unsigned long int
              ~f  A float, float
              ~d  A double float, double float
              ~p  An Erlang pid, erlang_pid*

              For example, to encode a tuple with some stuff:

              ei_x_format("{~a,~i,~d}", "numbers", 12, 3.14159)
              encodes the tuple {numbers,12,3.14159}

              ei_x_format_wo_ver() formats into a buffer, without the initial version byte.

       int ei_x_free(ei_x_buff* x)

              Frees an ei_x_buff buffer. The memory used by the buffer is returned to the OS.

       int ei_x_new(ei_x_buff* x)
       int ei_x_new_with_version(ei_x_buff* x)

              Allocates  a  new  ei_x_buff  buffer.  The  fields  of  the structure pointed to by
              parameter   x   is   filled   in,   and   a   default    buffer    is    allocated.
              ei_x_new_with_version()  also  puts  an  initial version byte, which is used in the
              binary format (so that ei_x_encode_version() will not be needed.)

DEBUG INFORMATION

       Some tips on what to check when the emulator does not seem to receive the terms  that  you
       send:

         * Be careful with the version header, use ei_x_new_with_version() when appropriate.

         * Turn on distribution tracing on the Erlang node.

         * Check the result codes from ei_decode_-calls.

SEE ALSO

       erl_eterm