erl_interface: Add bitstring and export fun support

25 files changed, 506 insertions, 106 deletions

diff --git a/lib/erl_interface/doc/src/ei.xml b/lib/erl_interface/doc/src/ei.xml
index d0d472c42b..254ae27cc8 100644
--- a/lib/erl_interface/doc/src/ei.xml
+++ b/lib/erl_interface/doc/src/ei.xml
@@ -183,6 +183,35 @@ typedef enum {
       </func>
 
       <func>
+          <name since="OTP @OTP-15712@"><ret>int</ret><nametext>ei_decode_bitstring(const char *buf, int *index, void *p, size_t plen, size_t *bitsp)</nametext></name>
+          <fsummary>Decode a bitstring.</fsummary>
+          <desc>
+            <p>Decodes a bitstring from the binary format.</p>
+	    <taglist>
+	      <tag><c>p</c></tag>
+	      <item><p>Either <c>NULL</c> or points to a buffer where the bytes of the
+	        bitstring will be written.</p>
+	      </item>
+	      <tag><c>plen</c></tag>
+	      <item><p>The max size of the bitstring in <em>bytes</em>, that is the
+	        size of the buffer if <c>p != NULL</c>.</p>
+	      </item>
+	      <tag><c>*bitsp</c></tag>
+	      <item><p>If <c>bitsp</c> is not <c>NULL</c>, set to the actual
+	        number of <em>bits</em> of the bitstring.</p>
+	      </item>
+	    </taglist>
+	    <p>Returns <c>0</c> if it was a bitstring no longer than <c>plen</c>
+	      bytes. The actual length of the bitstring will be
+	      <c>(*bitsp+7)/8</c> bytes. If <c>(*bitsp % 8) > 0</c> only the high
+	      <c>(*bitsp % 8)</c> bits of the last byte are significant.</p>
+	    <p>Number of bits may be divisible by 8, which means a binary
+	      decodable by <c>ei_decode_binary</c> is also decodable by
+	      <c>ei_decode_bitstring</c>.</p>
+          </desc>
+      </func>
+
+      <func>
           <name since=""><ret>int</ret><nametext>ei_decode_boolean(const char *buf, int *index, int *p)</nametext></name>
           <fsummary>Decode a boolean.</fsummary>
           <desc>
@@ -461,6 +490,18 @@ typedef enum {
     </func>
 
     <func>
+      <name since="OTP @OTP-15712@"><ret>int</ret><nametext>ei_encode_bitstring(char *buf, int *index, const void *p, size_t bits)</nametext></name>
+      <name since="OTP @OTP-15712@"><ret>int</ret><nametext>ei_x_encode_bitstring(ei_x_buff* x, const void *p, size_t bits)</nametext></name>
+      <fsummary>Encode a bitstring.</fsummary>
+      <desc>
+        <p>Encodes a bitstring in the binary format. The data is at
+          <c>p</c>. The size of the data is <c>bits</c> bits or
+	  <c>(bits+7)/8</c> bytes. If <c>(bits%8) > 0</c> only the high
+	  <c>(bits%8)</c> bits of the last byte are significant.</p>
+      </desc>
+    </func>
+
+    <func>
       <name since=""><ret>int</ret><nametext>ei_encode_boolean(char *buf, int *index, int p)</nametext></name>
       <name since=""><ret>int</ret><nametext>ei_x_encode_boolean(ei_x_buff* x, int p)</nametext></name>
       <fsummary>Encode a boolean.</fsummary>
diff --git a/lib/erl_interface/include/ei.h b/lib/erl_interface/include/ei.h
index 056acf9749..591367dc95 100644
--- a/lib/erl_interface/include/ei.h
+++ b/lib/erl_interface/include/ei.h
@@ -154,11 +154,14 @@ typedef LONG_PTR ssize_t; /* Sigh... */
 #define ERL_STRING_EXT        'k'
 #define ERL_LIST_EXT          'l'
 #define ERL_BINARY_EXT        'm'
+#define ERL_BIT_BINARY_EXT    'M'
 #define ERL_SMALL_BIG_EXT     'n'
 #define ERL_LARGE_BIG_EXT     'o'
 #define ERL_NEW_FUN_EXT	      'p'
 #define ERL_MAP_EXT           't'
 #define ERL_FUN_EXT	      'u'
+#define ERL_EXPORT_EXT        'q'
+
  
 #define ERL_NEW_CACHE         'N' /* c nodes don't know these two */
 #define ERL_CACHED_ATOM       'C'
@@ -269,15 +272,23 @@ typedef struct {
 typedef struct {
     long arity;
     char module[MAXATOMLEN_UTF8];
-    erlang_char_encoding module_org_enc;
-    char md5[16];
-    long index;
-    long old_index;
-    long uniq;
-    long n_free_vars;
-    erlang_pid pid;
-    long free_var_len;
-    char* free_vars;
+    enum { EI_FUN_CLOSURE, EI_FUN_EXPORT } type;
+    union {
+        struct {
+            char md5[16];
+            long index;
+            long old_index;
+            long uniq;
+            long n_free_vars;
+            erlang_pid pid;
+            long free_var_len;
+            char* free_vars;
+        } closure;
+        struct {
+            char* func;
+            int func_allocated;
+        } export;
+    } u;
 } erlang_fun;
 
 /* a big */
@@ -515,7 +526,9 @@ int ei_x_encode_atom_len(ei_x_buff* x, const char* s, int len);
 int ei_x_encode_atom_len_as(ei_x_buff* x, const char* s, int len,
 			  erlang_char_encoding from, erlang_char_encoding to);
 int ei_encode_binary(char *buf, int *index, const void *p, long len);
+int ei_encode_bitstring(char *buf, int *index, const void *p, size_t bits);
 int ei_x_encode_binary(ei_x_buff* x, const void* s, int len);
+int ei_x_encode_bitstring(ei_x_buff* x, const void* p, size_t bits);
 int ei_encode_pid(char *buf, int *index, const erlang_pid *p);
 int ei_x_encode_pid(ei_x_buff* x, const erlang_pid* pid);
 int ei_encode_fun(char* buf, int* index, const erlang_fun* p);
@@ -565,6 +578,7 @@ int ei_decode_string(const char *buf, int *index, char *p);
 int ei_decode_atom(const char *buf, int *index, char *p);
 int ei_decode_atom_as(const char *buf, int *index, char *p, int destlen, erlang_char_encoding want, erlang_char_encoding* was, erlang_char_encoding* result);
 int ei_decode_binary(const char *buf, int *index, void *p, long *len);
+int ei_decode_bitstring(const char *buf, int *index, void *p, size_t plen, size_t *bitsp);
 int ei_decode_fun(const char* buf, int* index, erlang_fun* p);
 void free_fun(erlang_fun* f);
 int ei_decode_pid(const char *buf, int *index, erlang_pid *p);
diff --git a/lib/erl_interface/src/connect/ei_connect.c b/lib/erl_interface/src/connect/ei_connect.c
index e75c4aadb5..0cbad235cc 100644
--- a/lib/erl_interface/src/connect/ei_connect.c
+++ b/lib/erl_interface/src/connect/ei_connect.c
@@ -1846,6 +1846,7 @@ static int send_name_or_challenge(ei_socket_callbacks *cbs,
     const char* function[] = {"SEND_NAME", "SEND_CHALLENGE"};
     int err;
     ssize_t len;
+    unsigned int flags;
 
     if (f_chall)
 	siz += 4;
@@ -1867,7 +1868,7 @@ static int send_name_or_challenge(ei_socket_callbacks *cbs,
     }
     put8(s, 'n');
     put16be(s, version);
-    put32be(s, (DFLAG_EXTENDED_REFERENCES
+    flags = (DFLAG_EXTENDED_REFERENCES
 		| DFLAG_DIST_MONITOR
 		| DFLAG_EXTENDED_PIDS_PORTS
 		| DFLAG_FUN_TAGS
@@ -1876,7 +1877,14 @@ static int send_name_or_challenge(ei_socket_callbacks *cbs,
 		| DFLAG_SMALL_ATOM_TAGS
 		| DFLAG_UTF8_ATOMS
 		| DFLAG_MAP_TAG
-		| DFLAG_BIG_CREATION));
+		| DFLAG_BIG_CREATION
+                | DFLAG_EXPORT_PTR_TAG
+                | DFLAG_BIT_BINARIES);
+    if (ei_internal_use_21_bitstr_expfun()) {
+        flags &= ~(DFLAG_EXPORT_PTR_TAG
+                   | DFLAG_BIT_BINARIES);
+    }
+    put32be(s, flags);
     if (f_chall)
 	put32be(s, challenge);
     memcpy(s, nodename, strlen(nodename));
diff --git a/lib/erl_interface/src/connect/ei_connect_int.h b/lib/erl_interface/src/connect/ei_connect_int.h
index 0bcccaa84b..b41a5f2b23 100644
--- a/lib/erl_interface/src/connect/ei_connect_int.h
+++ b/lib/erl_interface/src/connect/ei_connect_int.h
@@ -102,6 +102,8 @@ extern int h_errno;
 #define DFLAG_FUN_TAGS            16
 #define DFLAG_NEW_FUN_TAGS        0x80
 #define DFLAG_EXTENDED_PIDS_PORTS 0x100
+#define DFLAG_EXPORT_PTR_TAG      0x200
+#define DFLAG_BIT_BINARIES        0x400
 #define DFLAG_NEW_FLOATS          0x800
 #define DFLAG_SMALL_ATOM_TAGS     0x4000
 #define DFLAG_UTF8_ATOMS          0x10000
diff --git a/lib/erl_interface/src/decode/decode_binary.c b/lib/erl_interface/src/decode/decode_binary.c
index 5b8d234984..2799438bef 100644
--- a/lib/erl_interface/src/decode/decode_binary.c
+++ b/lib/erl_interface/src/decode/decode_binary.c
@@ -40,4 +40,40 @@ int ei_decode_binary(const char *buf, int *index, void *p, long *lenp)
   return 0; 
 }
 
+int ei_decode_bitstring(const char *buf, int *index, void *p, size_t plen,
+                        size_t *bitsp)
+{
+  const char *s = buf + *index;
+  const char *s0 = s;
+  unsigned long len;
+  unsigned char last_bits;
+  const unsigned char tag = get8(s);
+
+  if (tag == ERL_BINARY_EXT) {
+      long bytes;
+      int ret = ei_decode_binary(buf, index, p, &bytes);
+      if (bitsp)
+          *bitsp = (size_t)bytes * 8;
+      return ret;
+  }
+
+  if (tag != ERL_BIT_BINARY_EXT)
+      return -1;
+
+  len = get32be(s);
+  last_bits = get8(s);
+
+  if (len > plen || ((last_bits==0) != (len==0)) || last_bits > 8)
+      return -1;
+
+  if (p)
+      memcpy(p, s, len);
+  s += len;
+
+  if (bitsp)
+      *bitsp = (len == 0) ? 0 : ((len-1) * 8) + last_bits;
+
+  *index += s-s0;
+  return 0;
+}
 
diff --git a/lib/erl_interface/src/decode/decode_fun.c b/lib/erl_interface/src/decode/decode_fun.c
index f944c028af..32a950433e 100644
--- a/lib/erl_interface/src/decode/decode_fun.c
+++ b/lib/erl_interface/src/decode/decode_fun.c
@@ -33,22 +33,20 @@ int ei_decode_fun(const char *buf, int *index, erlang_fun *p)
     int i, ix, ix0, n;
     erlang_pid* p_pid;
     char* p_module;
-    erlang_char_encoding* p_module_org_enc;
     long* p_index;
     long* p_uniq;
     long* p_old_index;
 
     if (p != NULL) {
-	p_pid = &p->pid;
+	p_pid = &p->u.closure.pid;
 	p_module = &p->module[0];
-	p_module_org_enc = &p->module_org_enc;
-	p_index = &p->index;
-	p_uniq = &p->uniq;
-	p_old_index = &p->old_index;
+	p_index = &p->u.closure.index;
+	p_uniq = &p->u.closure.uniq;
+	p_old_index = &p->u.closure.old_index;
     }
     else {
-	p_pid = NULL; p_module = NULL; p_module_org_enc = NULL;
 	p_index = NULL; p_uniq = NULL; p_old_index = NULL;
+	p_pid = NULL; p_module = NULL;
     }
 
     switch (get8(s)) {
@@ -63,7 +61,7 @@ int ei_decode_fun(const char *buf, int *index, erlang_fun *p)
 	    return -1;
 	/* then the module (atom) */
 	if (ei_decode_atom_as(s, &ix, p_module, MAXATOMLEN_UTF8, ERLANG_UTF8,
-			      p_module_org_enc, NULL) < 0)
+                              NULL, NULL) < 0)
 	    return -1;
 	/* then the index */
 	if (ei_decode_long(s, &ix, p_index) < 0)
@@ -78,11 +76,11 @@ int ei_decode_fun(const char *buf, int *index, erlang_fun *p)
 		return -1;
 	}
 	if (p != NULL) {
-	    p->n_free_vars = n;
-	    p->free_var_len = ix - ix0;
-	    p->free_vars = ei_malloc(ix - ix0);
-	    if (!(p->free_vars)) return -1;
-	    memcpy(p->free_vars, s + ix0, ix - ix0);
+	    p->u.closure.n_free_vars = n;
+	    p->u.closure.free_var_len = ix - ix0;
+	    p->u.closure.free_vars = ei_malloc(ix - ix0);
+	    if (!(p->u.closure.free_vars)) return -1;
+	    memcpy(p->u.closure.free_vars, s + ix0, ix - ix0);
 	}
 	s += ix;
 	*index += s-s0;
@@ -93,20 +91,23 @@ int ei_decode_fun(const char *buf, int *index, erlang_fun *p)
 	n = get32be(s);
 	/* then the arity */
 	i = get8(s);
-	if (p != NULL) p->arity = i;
-	/* then md5 */
-	if (p != NULL) memcpy(p->md5, s, 16);
+	if (p != NULL) {
+            p->type = EI_FUN_CLOSURE;
+            p->arity = i;
+            /* then md5 */
+            memcpy(p->u.closure.md5, s, 16);
+        }
 	s += 16;
 	/* then index */
 	i = get32be(s);
-	if (p != NULL) p->index = i;
+	if (p != NULL) p->u.closure.index = i;
 	/* then the number of free vars (environment) */
 	i = get32be(s);
-	if (p != NULL) p->n_free_vars = i;
+	if (p != NULL) p->u.closure.n_free_vars = i;
 	/* then the module (atom) */
 	ix = 0;
 	if (ei_decode_atom_as(s, &ix, p_module, MAXATOMLEN_UTF8, ERLANG_UTF8,
-			      p_module_org_enc, NULL) < 0)
+                              NULL, NULL) < 0)
 	    return -1;
 	/* then the old_index */
 	if (ei_decode_long(s, &ix, p_old_index) < 0)
@@ -122,17 +123,56 @@ int ei_decode_fun(const char *buf, int *index, erlang_fun *p)
 	n = n - (s - s0) + 1;
 	if (n < 0) return -1;
 	if (p != NULL) {
-	    p->free_var_len = n;
+	    p->u.closure.free_var_len = n;
 	    if (n > 0) {
-		p->free_vars = malloc(n);
-		if (!(p->free_vars)) return -1;
-		memcpy(p->free_vars, s, n);
+		p->u.closure.free_vars = malloc(n);
+		if (!(p->u.closure.free_vars)) return -1;
+		memcpy(p->u.closure.free_vars, s, n);
 	    }
 	}
 	s += n;
 	*index += s-s0;
         return 0;
 	break;
+    case ERL_EXPORT_EXT: {
+        char* p_func;
+        long* p_arity;
+        int used;
+
+        if (p) {
+            p->type = EI_FUN_EXPORT;
+            p_arity = &p->arity;
+        }
+        else {
+            p_arity = NULL;
+        }
+        if (ei_decode_atom_as(s, &ix, p_module, MAXATOMLEN_UTF8, ERLANG_UTF8,
+                              NULL, NULL) < 0)
+            return -1;
+        if (p) {
+            /* try use module buffer for function name */
+            used = strlen(p->module) + 1;
+            p_func = p->module + used;
+            p->u.export.func = p_func;
+            p->u.export.func_allocated = 0;
+        }
+        else {
+            used = 0;
+            p_func = NULL;
+        }
+        while (ei_decode_atom_as(s, &ix, p_func, MAXATOMLEN_UTF8-used,
+                                 ERLANG_UTF8, NULL, NULL) < 0) {
+            if (!used)
+                return -1;
+            p_func = malloc(MAXATOMLEN_UTF8);
+            p->u.export.func = p_func;
+            p->u.export.func_allocated = 1;
+            used = 0;
+        }
+        if (ei_decode_long(s, &ix, p_arity) < 0)
+            return -1;
+        return 0;
+    }
     default:
 	return -1;
     }
@@ -140,6 +180,14 @@ int ei_decode_fun(const char *buf, int *index, erlang_fun *p)
 
 void free_fun(erlang_fun* f)
 {
-  if (f->free_var_len > 0)
-      ei_free(f->free_vars);
+    switch (f->type) {
+    case EI_FUN_CLOSURE:
+        if (f->u.closure.free_var_len > 0)
+            ei_free(f->u.closure.free_vars);
+        break;
+    case EI_FUN_EXPORT:
+        if (f->u.export.func_allocated)
+            ei_free(f->u.export.func);
+        break;
+    }
 }
diff --git a/lib/erl_interface/src/decode/decode_skip.c b/lib/erl_interface/src/decode/decode_skip.c
index a9f6242e35..11d3bc1786 100644
--- a/lib/erl_interface/src/decode/decode_skip.c
+++ b/lib/erl_interface/src/decode/decode_skip.c
@@ -21,6 +21,14 @@
 #include "eiext.h"
 #include "decode_skip.h"
 
+#ifdef HAVE_STDINT_H
+#  include <stdint.h>
+#endif
+
+#ifndef SIZE_MAX
+#  define SIZE_MAX (~((size_t)0))
+#endif
+
 int ei_skip_term(const char* buf, int* index)
 {
     int i, n, ty;
@@ -79,6 +87,10 @@ int ei_skip_term(const char* buf, int* index)
 	if (ei_decode_binary(buf, index, NULL, NULL) < 0)
 	    return -1;
 	break;
+    case ERL_BIT_BINARY_EXT:
+        if (ei_decode_bitstring(buf, index, NULL, SIZE_MAX, NULL) < 0)
+            return -1;
+        break;
     case ERL_SMALL_INTEGER_EXT:
     case ERL_INTEGER_EXT:
 	if (ei_decode_long(buf, index, NULL) < 0) return -1;
diff --git a/lib/erl_interface/src/encode/encode_binary.c b/lib/erl_interface/src/encode/encode_binary.c
index 4471c51769..4aa9f6bc16 100644
--- a/lib/erl_interface/src/encode/encode_binary.c
+++ b/lib/erl_interface/src/encode/encode_binary.c
@@ -40,3 +40,27 @@ int ei_encode_binary(char *buf, int *index, const void *p, long len)
   return 0; 
 }
 
+int ei_encode_bitstring(char *buf, int *index, const void *p, size_t bits)
+{
+  char *s = buf + *index;
+  char *s0 = s;
+  size_t bytes = (bits + 7) / 8;
+  char last_bits = bits % 8;
+
+  if (bytes == 0 || last_bits == 0)
+      return ei_encode_binary(buf, index, p, bytes);
+
+  if (!buf) s += 6;
+  else {
+      put8(s, ERL_BIT_BINARY_EXT);
+      put32be(s, bytes);
+      put8(s, last_bits);
+      memcpy(s, p, bytes);
+      s[bytes-1] &= (0xff << (8-last_bits));
+  }
+  s += bytes;
+
+  *index += s-s0;
+
+  return 0;
+}
diff --git a/lib/erl_interface/src/encode/encode_fun.c b/lib/erl_interface/src/encode/encode_fun.c
index 3bfc7530d1..38ba7c5b30 100644
--- a/lib/erl_interface/src/encode/encode_fun.c
+++ b/lib/erl_interface/src/encode/encode_fun.c
@@ -26,56 +26,72 @@ int ei_encode_fun(char *buf, int *index, const erlang_fun *p)
 {
     int ix = *index;
 
-    if (p->arity == -1) {
-	/* ERL_FUN_EXT */
-	if (buf != NULL) {
-	    char* s = buf + ix;
-	    put8(s, ERL_FUN_EXT);
-	    put32be(s, p->n_free_vars);
-	}
-	ix += sizeof(char) + 4;
-	if (ei_encode_pid(buf, &ix, &p->pid) < 0)
-	    return -1;
-	if (ei_encode_atom_as(buf, &ix, p->module, ERLANG_UTF8, p->module_org_enc) < 0)
-	    return -1;
-	if (ei_encode_long(buf, &ix, p->index) < 0)
-	    return -1;
-	if (ei_encode_long(buf, &ix, p->uniq) < 0)
-	    return -1;
-	if (buf != NULL)
-	    memcpy(buf + ix, p->free_vars, p->free_var_len);
-	ix += p->free_var_len;
-    } else {
-	char *size_p;
-	/* ERL_NEW_FUN_EXT */
-	if (buf != NULL) {
-	    char* s = buf + ix;
-	    put8(s, ERL_NEW_FUN_EXT);
-	    size_p = s;
-	    s += 4;
-	    put8(s, p->arity);
-	    memcpy(s, p->md5, sizeof(p->md5));
-	    s += sizeof(p->md5);
-	    put32be(s, p->index);
-	    put32be(s, p->n_free_vars);
-	} else
-	    size_p = NULL;
-	ix += 1 + 4 + 1 + sizeof(p->md5) + 4 + 4;
-	if (ei_encode_atom_as(buf, &ix, p->module, ERLANG_UTF8, p->module_org_enc) < 0)
-	    return -1;
-	if (ei_encode_long(buf, &ix, p->old_index) < 0)
-	    return -1;
-	if (ei_encode_long(buf, &ix, p->uniq) < 0)
-	    return -1;
-	if (ei_encode_pid(buf, &ix, &p->pid) < 0)
-	    return -1;
-	if (buf != NULL)
-	    memcpy(buf + ix, p->free_vars, p->free_var_len);
-	ix += p->free_var_len;
-	if (size_p != NULL) {
-	    int sz = buf + ix - size_p;
-	    put32be(size_p, sz);
+    switch (p->type) {
+    case EI_FUN_CLOSURE:
+	if (p->arity == -1) {
+	    /* ERL_FUN_EXT */
+	    if (buf != NULL) {
+		char* s = buf + ix;
+		put8(s, ERL_FUN_EXT);
+		put32be(s, p->u.closure.n_free_vars);
+	    }
+	    ix += sizeof(char) + 4;
+	    if (ei_encode_pid(buf, &ix, &p->u.closure.pid) < 0)
+		return -1;
+	    if (ei_encode_atom_as(buf, &ix, p->module, ERLANG_UTF8, ERLANG_UTF8) < 0)
+		return -1;
+	    if (ei_encode_long(buf, &ix, p->u.closure.index) < 0)
+		return -1;
+	    if (ei_encode_long(buf, &ix, p->u.closure.uniq) < 0)
+		return -1;
+	    if (buf != NULL)
+		memcpy(buf + ix, p->u.closure.free_vars, p->u.closure.free_var_len);
+	    ix += p->u.closure.free_var_len;
+	} else {
+	    char *size_p;
+	    if (buf != NULL) {
+		char* s = buf + ix;
+		put8(s, ERL_NEW_FUN_EXT);
+		size_p = s;
+		s += 4;
+		put8(s, p->arity);
+		memcpy(s, p->u.closure.md5, sizeof(p->u.closure.md5));
+		s += sizeof(p->u.closure.md5);
+		put32be(s, p->u.closure.index);
+		put32be(s, p->u.closure.n_free_vars);
+	    } else
+		size_p = NULL;
+	    ix += 1 + 4 + 1 + sizeof(p->u.closure.md5) + 4 + 4;
+	    if (ei_encode_atom_as(buf, &ix, p->module, ERLANG_UTF8, ERLANG_UTF8) < 0)
+		return -1;
+	    if (ei_encode_long(buf, &ix, p->u.closure.old_index) < 0)
+		return -1;
+	    if (ei_encode_long(buf, &ix, p->u.closure.uniq) < 0)
+		return -1;
+	    if (ei_encode_pid(buf, &ix, &p->u.closure.pid) < 0)
+		return -1;
+	    if (buf != NULL)
+		memcpy(buf + ix, p->u.closure.free_vars, p->u.closure.free_var_len);
+	    ix += p->u.closure.free_var_len;
+	    if (size_p != NULL) {
+		int sz = buf + ix - size_p;
+		put32be(size_p, sz);
+	    }
 	}
+	break;
+    case EI_FUN_EXPORT:
+        if (buf != NULL) {
+            char* s = buf + ix;
+            put8(s, ERL_EXPORT_EXT);
+        }
+        ix++;
+        if (ei_encode_atom_as(buf, &ix, p->module, ERLANG_UTF8, ERLANG_UTF8) < 0)
+            return -1;
+        if (ei_encode_atom_as(buf, &ix, p->u.export.func, ERLANG_UTF8, ERLANG_UTF8) < 0)
+            return -1;
+        if (ei_encode_long(buf, &ix, p->arity) < 0)
+            return -1;
+        break;
     }
     *index = ix;
     return 0;
diff --git a/lib/erl_interface/src/misc/ei_compat.c b/lib/erl_interface/src/misc/ei_compat.c
index ff94e144ee..787895992e 100644
--- a/lib/erl_interface/src/misc/ei_compat.c
+++ b/lib/erl_interface/src/misc/ei_compat.c
@@ -22,14 +22,22 @@
 #include "ei.h"
 #include "ei_internal.h"
 
-#define EI_COMPAT_NO_REL (~((unsigned) 0))
+#include <limits.h>
 
-static unsigned compat_rel = EI_COMPAT_NO_REL;
+#ifndef EI_COMPAT
+#  define EI_COMPAT UINT_MAX
+#endif
+
+static unsigned compat_rel = EI_COMPAT;
 
 void
 ei_set_compat_rel(unsigned rel)
 {
-    if (compat_rel == EI_COMPAT_NO_REL)
-	compat_rel = rel;
+    compat_rel = rel;
+}
+
+int ei_internal_use_21_bitstr_expfun(void)
+{
+    return compat_rel < 22;
 }
 
diff --git a/lib/erl_interface/src/misc/ei_decode_term.c b/lib/erl_interface/src/misc/ei_decode_term.c
index 63a7034508..8a4f7cc30d 100644
--- a/lib/erl_interface/src/misc/ei_decode_term.c
+++ b/lib/erl_interface/src/misc/ei_decode_term.c
@@ -87,6 +87,14 @@ int ei_decode_ei_term(const char* buf, int* index, ei_term* term)
     case ERL_BINARY_EXT:
 	term->size = get32be(s);
 	return 0;
+    case ERL_BIT_BINARY_EXT: {
+        int bytes = get32be(s);
+        int last_bits = get8(s);
+        if (((last_bits==0) != (bytes==0)) || last_bits > 8)
+            return -1;
+        term->size = bytes;
+        return 0;
+    }
     case ERL_SMALL_BIG_EXT:
 	if ((term->arity = get8(s)) != 4) return -1;
 	sign = get8(s);
diff --git a/lib/erl_interface/src/misc/ei_internal.h b/lib/erl_interface/src/misc/ei_internal.h
index 17abe6cf90..ab12597c86 100644
--- a/lib/erl_interface/src/misc/ei_internal.h
+++ b/lib/erl_interface/src/misc/ei_internal.h
@@ -157,6 +157,8 @@ int ei_init_connect(void);
 
 void ei_trace_printf(const char *name, int level, const char *format, ...);
 
+int ei_internal_use_21_bitstr_expfun(void);
+
 int ei_get_cbs_ctx__(ei_socket_callbacks **cbs, void **ctx, int fd);
 
 #endif /* _EI_INTERNAL_H */
diff --git a/lib/erl_interface/src/misc/ei_printterm.c b/lib/erl_interface/src/misc/ei_printterm.c
index e83f29b0c1..a89b990ac1 100644
--- a/lib/erl_interface/src/misc/ei_printterm.c
+++ b/lib/erl_interface/src/misc/ei_printterm.c
@@ -249,6 +249,34 @@ static int print_term(FILE* fp, ei_x_buff* x,
 	xputc('>', fp, x); ++ch_written;
 	ei_free(p);
 	break;
+    case ERL_BIT_BINARY_EXT: {
+        size_t bits;
+        int trunc = 0;
+        p = ei_malloc(n);
+        if (p == NULL) goto err;
+        if (ei_decode_bitstring(buf, index, p, n, &bits) < 0) {
+            ei_free(p);
+            goto err;
+        }
+        ch_written += xprintf(fp, x, "#Bits<");
+        m = (bits+7) / 8;
+        if (m > BINPRINTSIZE) {
+            m = BINPRINTSIZE;
+            trunc = 1;
+        }
+        --m;
+        for (i = 0; i < m; ++i) {
+            ch_written += xprintf(fp, x, "%d,", p[i]);
+        }
+        ch_written += xprintf(fp, x, "%d", p[i]);
+        if (trunc)
+            ch_written += xprintf(fp, x, ",...");
+        else if (bits % 8 != 0)
+            ch_written += xprintf(fp, x, ":%u", (unsigned)(bits % 8));
+        xputc('>', fp, x); ++ch_written;
+        ei_free(p);
+        break;
+    }
     case ERL_SMALL_INTEGER_EXT:
     case ERL_INTEGER_EXT:
 	if (ei_decode_long(buf, index, &l) < 0) goto err;
diff --git a/lib/erl_interface/src/misc/ei_x_encode.c b/lib/erl_interface/src/misc/ei_x_encode.c
index 4ff5974663..2da271795f 100644
--- a/lib/erl_interface/src/misc/ei_x_encode.c
+++ b/lib/erl_interface/src/misc/ei_x_encode.c
@@ -117,6 +117,16 @@ int ei_x_encode_binary(ei_x_buff* x, const void* p, int len)
     return ei_encode_binary(x->buff, &x->index, p, len);
 }
 
+int ei_x_encode_bitstring(ei_x_buff* x, const void* p, size_t bits)
+{
+    int i = x->index;
+    if (ei_encode_bitstring(NULL, &i, p, bits) == -1)
+      return -1;
+    if (!x_fix_buff(x, i))
+	return -1;
+    return ei_encode_bitstring(x->buff, &x->index, p, bits);
+}
+
 int ei_x_encode_long(ei_x_buff* x, long n)
 {
     int i = x->index;
diff --git a/lib/erl_interface/src/misc/get_type.c b/lib/erl_interface/src/misc/get_type.c
index aa8ea1176b..eef58a9363 100644
--- a/lib/erl_interface/src/misc/get_type.c
+++ b/lib/erl_interface/src/misc/get_type.c
@@ -57,6 +57,7 @@ int ei_get_type(const char *buf, const int *index, int *type, int *len)
   case ERL_LIST_EXT:
   case ERL_MAP_EXT:
   case ERL_BINARY_EXT:
+  case ERL_BIT_BINARY_EXT:
     *len = get32be(s);
     break;
     
diff --git a/lib/erl_interface/src/misc/show_msg.c b/lib/erl_interface/src/misc/show_msg.c
index ad003605ad..2d49eb6449 100644
--- a/lib/erl_interface/src/misc/show_msg.c
+++ b/lib/erl_interface/src/misc/show_msg.c
@@ -24,6 +24,13 @@
 #include <stdlib.h>
 #include <stdarg.h>
 #include <string.h>
+#ifdef HAVE_STDINT_H
+#  include <stdint.h>
+#endif
+
+#ifndef SIZE_MAX
+#  define SIZE_MAX (~((size_t)0))
+#endif
 
 #include <sys/types.h>
 
@@ -455,6 +462,12 @@ static void show_term(const char *termbuf, int *index, FILE *stream)
 	fprintf(stream,"#Bin<%ld>",num);
 	break;
     
+    case ERL_BIT_BINARY_EXT: {
+        size_t bits;
+        ei_decode_bitstring(termbuf, index, NULL, SIZE_MAX, &bits);
+        fprintf(stream, "#Bits<%lu>", (unsigned long)bits);
+        break;
+    }
     case ERL_LARGE_BIG_EXT:
 	/* doesn't actually decode - just skip over it */
 	/* FIXME if GMP, what to do here?? */
diff --git a/lib/erl_interface/test/all_SUITE_data/ei_runner.h b/lib/erl_interface/test/all_SUITE_data/ei_runner.h
index 2608661303..7c874ac82e 100644
--- a/lib/erl_interface/test/all_SUITE_data/ei_runner.h
+++ b/lib/erl_interface/test/all_SUITE_data/ei_runner.h
@@ -53,6 +53,7 @@ void free_packet(char*);
 
 #define fail(reason) do_fail(__FILE__, __LINE__, reason)
 #define fail1(reason, a1) do_fail(__FILE__, __LINE__, reason, a1)
+#define fail2(reason, a1, a2) do_fail(__FILE__, __LINE__, reason, a1, a2)
 #define report(ok) do_report(__FILE__, __LINE__, ok)
 
 void do_report(char* file, int line, int ok);
diff --git a/lib/erl_interface/test/ei_accept_SUITE.erl b/lib/erl_interface/test/ei_accept_SUITE.erl
index 9c9c3f86b6..f40c67375b 100644
--- a/lib/erl_interface/test/ei_accept_SUITE.erl
+++ b/lib/erl_interface/test/ei_accept_SUITE.erl
@@ -43,8 +43,12 @@ init_per_testcase(Case, Config) ->
     runner:init_per_testcase(?MODULE, Case, Config).
 
 ei_accept(Config) when is_list(Config) ->
+    ei_accept_do(Config, 0),   % default
+    ei_accept_do(Config, 21).  % ei_set_compat_rel
+
+ei_accept_do(Config, CompatRel) ->
     P = runner:start(Config, ?interpret),
-    0 = ei_connect_init(P, 42, erlang:get_cookie(), 0),
+    0 = ei_connect_init(P, 42, erlang:get_cookie(), 0, CompatRel),
 
     Myname = hd(tl(string:tokens(atom_to_list(node()), "@"))),
     io:format("Myname ~p ~n",  [Myname]),
@@ -52,15 +56,18 @@ ei_accept(Config) when is_list(Config) ->
     io:format("EINode ~p ~n",  [EINode]),
 
     %% We take this opportunity to also test export-funs and bit-strings
-    %% with (ugly) tuple fallbacks.
+    %% with (ugly) tuple fallbacks in OTP 21 and older.
     %% Test both toward pending connection and established connection.
     RealTerms = [<<1:1>>,     fun lists:map/2],
-    Fallbacks = [{<<128>>,1}, {lists,map}],
+    EncTerms = case CompatRel of
+                   0 -> RealTerms;
+                   21 -> [{<<128>>,1}, {lists,map}]
+                end,
 
     Self = self(),
     Funny = fun() -> hello end,
     TermToSend = {call, Self, "Test", Funny, RealTerms},
-    TermToGet  = {call, Self, "Test", Funny, Fallbacks},
+    TermToGet  = {call, Self, "Test", Funny, EncTerms},
     Port = 6543,
     {ok, ListenFd} = ei_publish(P, Port),
     {any, EINode} ! TermToSend,
@@ -94,7 +101,7 @@ ei_threaded_accept(Config) when is_list(Config) ->
 %% Test erlang:monitor toward erl_interface "processes"
 monitor_ei_process(Config) when is_list(Config) ->
     P = runner:start(Config, ?interpret),
-    0 = ei_connect_init(P, 42, erlang:get_cookie(), 0),
+    0 = ei_connect_init(P, 42, erlang:get_cookie(), 0, 0),
 
     Myname = hd(tl(string:tokens(atom_to_list(node()), "@"))),
     io:format("Myname ~p ~n",  [Myname]),
@@ -167,8 +174,8 @@ start_einode(Einode, N, Host) ->
 
 %%% Interface functions for ei (erl_interface) functions.
 
-ei_connect_init(P, Num, Cookie, Creation) ->
-    send_command(P, ei_connect_init, [Num,Cookie,Creation]),
+ei_connect_init(P, Num, Cookie, Creation, Compat) ->
+    send_command(P, ei_connect_init, [Num,Cookie,Creation,Compat]),
     case get_term(P) of
         {term,Int} when is_integer(Int) -> Int
     end.
diff --git a/lib/erl_interface/test/ei_accept_SUITE_data/ei_accept_test.c b/lib/erl_interface/test/ei_accept_SUITE_data/ei_accept_test.c
index d85b2d38c7..09b0b5440b 100644
--- a/lib/erl_interface/test/ei_accept_SUITE_data/ei_accept_test.c
+++ b/lib/erl_interface/test/ei_accept_SUITE_data/ei_accept_test.c
@@ -58,7 +58,7 @@ static struct {
     int num_args;		/* Number of arguments. */
     void (*func)(char* buf, int len);
 } commands[] = {
-    "ei_connect_init",  3, cmd_ei_connect_init,
+    "ei_connect_init",  4, cmd_ei_connect_init,
     "ei_publish", 	1, cmd_ei_publish,
     "ei_accept", 	1, cmd_ei_accept,
     "ei_receive",  	1, cmd_ei_receive,
@@ -106,18 +106,25 @@ TESTCASE(interpret)
 static void cmd_ei_connect_init(char* buf, int len)
 {
     int index = 0, r = 0;
-    long l;
-    char b[100];
+    long num, creation;
+    unsigned long compat;
+    char node_name[100];
     char cookie[MAXATOMLEN], * cp = cookie;
     ei_x_buff res;
-    if (ei_decode_long(buf, &index, &l) < 0)
+    if (ei_decode_long(buf, &index, &num) < 0)
 	fail("expected int");
-    sprintf(b, "c%d", l);
+    sprintf(node_name, "c%d", num);
     if (ei_decode_atom(buf, &index, cookie) < 0)
 	fail("expected atom (cookie)");
     if (cookie[0] == '\0')
 	cp = NULL;
-    r = ei_connect_init(&ec, b, cp, 0);
+    if (ei_decode_long(buf, &index, &creation) < 0)
+	fail("expected int");
+    if (ei_decode_long(buf, &index, &compat) < 0)
+	fail("expected uint");
+    if (compat)
+        ei_set_compat_rel(compat);
+    r = ei_connect_init(&ec, node_name, cp, creation);
     ei_x_new_with_version(&res);
     ei_x_encode_long(&res, r);
     send_bin_term(&res);
diff --git a/lib/erl_interface/test/ei_connect_SUITE.erl b/lib/erl_interface/test/ei_connect_SUITE.erl
index 75b6bf18da..6184ce801b 100644
--- a/lib/erl_interface/test/ei_connect_SUITE.erl
+++ b/lib/erl_interface/test/ei_connect_SUITE.erl
@@ -79,9 +79,10 @@ ei_send_funs(Config) when is_list(Config) ->
     {ok,Fd} = ei_connect(P, node()),
 
     Fun1 = fun ei_send/1,
-    Fun2 = fun(X) -> P, X, Fd, Fun1 end,
+    Fun2 = fun(X) -> {P, X, Fd, Fun1} end,
+    Bits = <<1,2,3:5>>,
 
-    AMsg={Fun1,Fun2},
+    AMsg={Fun1,Fun2,Bits},
     %%AMsg={wait_with_funs, new_dist_format},
     ok = ei_send_funs(P, Fd, self(), AMsg),
     EIMsg = receive M -> M end,
diff --git a/lib/erl_interface/test/ei_connect_SUITE_data/ei_connect_test.c b/lib/erl_interface/test/ei_connect_SUITE_data/ei_connect_test.c
index b002871ffe..7c9e79f837 100644
--- a/lib/erl_interface/test/ei_connect_SUITE_data/ei_connect_test.c
+++ b/lib/erl_interface/test/ei_connect_SUITE_data/ei_connect_test.c
@@ -209,6 +209,8 @@ static void cmd_ei_send_funs(char* buf, int len)
     erlang_pid pid;
     ei_x_buff x;
     erlang_fun fun1, fun2;
+    unsigned char bitstring[10];
+    size_t bits;
 
     if (ei_decode_long(buf, &index, &fd) < 0)
 	fail("expected long");
@@ -216,20 +218,24 @@ static void cmd_ei_send_funs(char* buf, int len)
 	fail("expected pid (node)");
     if (ei_decode_tuple_header(buf, &index, &n) < 0)
 	fail("expected tuple");
-    if (n != 2)
+    if (n != 3)
 	fail("expected tuple");
     if (ei_decode_fun(buf, &index, &fun1) < 0)
 	fail("expected Fun1");
     if (ei_decode_fun(buf, &index, &fun2) < 0)
 	fail("expected Fun2");
+    if (ei_decode_bitstring(buf, &index, bitstring, sizeof(bitstring), &bits) < 0)
+	fail("expected bitstring");
     if (ei_x_new_with_version(&x) < 0)
 	fail("ei_x_new_with_version");
-    if (ei_x_encode_tuple_header(&x, 2) < 0)
+    if (ei_x_encode_tuple_header(&x, 3) < 0)
 	fail("encode tuple header");
     if (ei_x_encode_fun(&x, &fun1) < 0)
 	fail("encode fun1");
     if (ei_x_encode_fun(&x, &fun2) < 0)
 	fail("encode fun2");
+    if (ei_x_encode_bitstring(&x, bitstring, bits) < 0)
+	fail("encode bitstring");
     free_fun(&fun1);
     free_fun(&fun2);
     send_errno_result(ei_send(fd, &pid, x.buff, x.index));
diff --git a/lib/erl_interface/test/ei_decode_SUITE.erl b/lib/erl_interface/test/ei_decode_SUITE.erl
index 75560ea7c9..e005ec89c7 100644
--- a/lib/erl_interface/test/ei_decode_SUITE.erl
+++ b/lib/erl_interface/test/ei_decode_SUITE.erl
@@ -194,6 +194,9 @@ test_ei_decode_misc(Config) when is_list(Config) ->
     send_term_as_binary(P,<<>>),
     send_term_as_binary(P,<<"ÅÄÖåäö">>),
 
+    send_term_as_binary(P,<<1, 2, 3:5>>),
+    send_term_as_binary(P,<<1:1>>),
+
     %    send_term_as_binary(P,{}),
     %    send_term_as_binary(P,[]),
 
diff --git a/lib/erl_interface/test/ei_decode_SUITE_data/ei_decode_test.c b/lib/erl_interface/test/ei_decode_SUITE_data/ei_decode_test.c
index 66cdf2f502..d39970a857 100644
--- a/lib/erl_interface/test/ei_decode_SUITE_data/ei_decode_test.c
+++ b/lib/erl_interface/test/ei_decode_SUITE_data/ei_decode_test.c
@@ -317,6 +317,69 @@ static void decode_bin(int exp_size, const char* val, int exp_len)
     free_packet(buf);
 }
 
+static void decode_bits(int exp_size, const char* val, size_t exp_bits)
+{
+    char p[1024];
+    char *buf;
+    size_t bits;
+    int size1 = 0;
+    int size2 = 0;
+    int err;
+    message("ei_decode_bitstring should be %d bits", (int)exp_bits);
+    buf = read_packet(NULL);
+    err = ei_decode_bitstring(buf+1, &size1, NULL, sizeof(p), &bits);
+    message("err = %d, size = %d, len = %d, expected size = %d, expected bits = %d\n",\
+            err,size1, (int)bits, exp_size, (int)exp_bits);
+
+    if (err != 0) {
+        if (err != -1) {
+            fail("returned non zero but not -1 if NULL pointer");
+        } else {
+            fail("returned non zero");
+        }
+        return;
+    }
+
+    if (bits != exp_bits) {
+        fail("number of bits is not correct");
+        return;
+    }
+
+    err = ei_decode_bitstring(buf+1, &size2, p, sizeof(p), &bits);
+    message("err = %d, size = %d, len = %d, expected size = %d, expected len = %d\n",\
+            err,size2, (int)bits, exp_size, (int)exp_bits);
+    if (err != 0) {
+        if (err != -1) {
+            fail("returned non zero but not -1 if NULL pointer");
+        } else {
+            fail("returned non zero");
+        }
+        return;
+    }
+
+    if (bits != exp_bits) {
+        fail("bits is not correct");
+        return;
+    }
+
+    if (memcmp(p, val, (exp_bits+7)/8) != 0) {
+        fail("value is not correct");
+        return;
+    }
+
+    if (size1 != size2) {
+        fail("size with and without pointer differs");
+        return;
+    }
+
+    if (size1 != exp_size) {
+        fail2("size of encoded data is incorrect %d != %d", size1, exp_size);
+        return;
+    }
+    free_packet(buf);
+}
+
+
 /* ******************************************************************** */
 
 TESTCASE(test_ei_decode_long)
@@ -648,6 +711,14 @@ TESTCASE(test_ei_decode_misc)
     decode_bin(5, "", 0);
     decode_bin(11, "������", 6);
 
+#define LAST_BYTE(V, BITS) ((V) << (8-(BITS)))
+    {
+        unsigned char bits1[] = {1, 2, LAST_BYTE(3,5) };
+        unsigned char bits2[] = {LAST_BYTE(1,1) };
+        decode_bits(9, bits1, 21);
+        decode_bits(7, bits2, 1);
+    }
+
     /* FIXME check \0 in strings and atoms? */
 /*
     EI_ENCODE_1(decode_tuple_header, 0);
diff --git a/lib/erl_interface/test/ei_decode_encode_SUITE.erl b/lib/erl_interface/test/ei_decode_encode_SUITE.erl
index 0f23cdfbb9..d8b0bce3ae 100644
--- a/lib/erl_interface/test/ei_decode_encode_SUITE.erl
+++ b/lib/erl_interface/test/ei_decode_encode_SUITE.erl
@@ -120,6 +120,8 @@ test_ei_decode_encode(Config) when is_list(Config) ->
     send_rec(P, #{key => value}),
     send_rec(P, maps:put(Port, Ref, #{key => value, key2 => Pid})),
 
+    [send_rec(P, <<16#dec0deb175:B/little>>) || B <- lists:seq(0,48)],
+
     runner:recv_eot(P),
     ok.
 
diff --git a/lib/erl_interface/test/ei_decode_encode_SUITE_data/ei_decode_encode_test.c b/lib/erl_interface/test/ei_decode_encode_SUITE_data/ei_decode_encode_test.c
index 55d9ed1b1a..f9c05b2739 100644
--- a/lib/erl_interface/test/ei_decode_encode_SUITE_data/ei_decode_encode_test.c
+++ b/lib/erl_interface/test/ei_decode_encode_SUITE_data/ei_decode_encode_test.c
@@ -40,6 +40,12 @@ typedef struct
     erlang_char_encoding enc;
 }my_atom;
 
+typedef struct
+{
+    char bytes[MAXATOMLEN_UTF8];
+    size_t nbits;
+}my_bitstring;
+
 struct my_obj {
     union {
 	erlang_fun fun;
@@ -49,6 +55,7 @@ struct my_obj {
 	erlang_trace trace;
 	erlang_big big;
 	my_atom atom;
+        my_bitstring bits;
 
 	int arity;
     }u;
@@ -119,6 +126,26 @@ struct Type my_atom_type = {
     (encodeFT*)ei_encode_my_atom, (x_encodeFT*)ei_x_encode_my_atom
 };
 
+int ei_decode_my_bits(const char *buf, int *index, my_bitstring* a)
+{
+    return ei_decode_bitstring(buf, index, (a ? a->bytes : NULL),
+                               sizeof(a->bytes),
+                               (a ? &a->nbits : NULL));
+}
+int ei_encode_my_bits(char *buf, int *index, my_bitstring* a)
+{
+    return ei_encode_bitstring(buf, index, a->bytes, a->nbits);
+}
+int ei_x_encode_my_bits(ei_x_buff* x, my_bitstring* a)
+{
+    return ei_x_encode_bitstring(x, a->bytes, a->nbits);
+}
+
+struct Type my_bitstring_type = {
+    "bits", "my_bitstring", (decodeFT*)ei_decode_my_bits,
+    (encodeFT*)ei_encode_my_bits, (x_encodeFT*)ei_x_encode_my_bits
+};
+
 
 int my_decode_tuple_header(const char *buf, int *index, struct my_obj* obj)
 {
@@ -537,6 +564,10 @@ TESTCASE(test_ei_decode_encode)
 	decode_encode(map, 7);
     }
 
+    for (i=0; i <= 48; i++) {
+        decode_encode_one(&my_bitstring_type);
+    }
+
     report(1);
 }