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asn1: Circular types and Topo. sort declarations

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Many external ASN.1 modules that we have imported over time define types
like this:

  Foo ::= SEQUENCE { bar Bar }
  Bar ::= SEQUENCE { aMember INTEGER }

and before this change one had to re-order the definitions so that the
one for `Bar` came first.  No more.

We can now have out of order definitions in ASN.1 modules and the
compiler will topologically sort output C type declarations so that one
no longer has to manually sort types in ASN.1 modules when importing
them.

Besides that, it is now possible to create circular data types using
OPTIONAL since we generate such fields as pointers (which can then be
pointers to incomplete struct declarations):

  Circular ::= SEQUENCE {
          name UTF8String,
          next Circular OPTIONAL
  }

Circular types aren't necessarily useful, but they have been used in the
past.  E.g., the rpc.mountd protocol uses a circular type as a linked
list -- it should just have used an array, of course, as that's
semantically equivalent but more space efficient in its encoding, but
the point is that such types exist out there.
This commit is contained in:
Nicolas Williams
2020-12-24 03:18:28 -06:00
parent 5b978c7437
commit 83d4c6ddb5
8 changed files with 367 additions and 30 deletions
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254
lib/asn1/gen.c
View File

@@ -752,9 +752,12 @@ define_type (int level, const char *name, const char *basename, Type *t, int typ
switch (t->type) {
case TType:
space(level);
fprintf (headerfile, "%s %s;\n", t->symbol->gen_name, name);
fprintf(headerfile, "%s %s;\n", t->symbol->gen_name, name);
break;
case TInteger:
if (t->symbol && t->symbol->emitted_definition)
break;
space(level);
if(t->members) {
Member *m;
@@ -768,11 +771,11 @@ define_type (int level, const char *name, const char *basename, Type *t, int typ
label_prefix, label_prefix_sep,
m->gen_name, m->val, last_member_p(m));
}
fprintf (headerfile, "} %s;\n", name);
fprintf(headerfile, "} %s;\n", name);
} else if (t->range == NULL) {
fprintf (headerfile, "heim_integer %s;\n", name);
fprintf(headerfile, "heim_integer %s;\n", name);
} else if (t->range->min < INT_MIN && t->range->max <= INT64_MAX) {
fprintf (headerfile, "int64_t %s;\n", name);
fprintf(headerfile, "int64_t %s;\n", name);
} else if (t->range->min >= 0 && t->range->max > UINT_MAX) {
fprintf (headerfile, "uint64_t %s;\n", name);
} else if (t->range->min >= INT_MIN && t->range->max <= INT_MAX) {
@@ -798,6 +801,10 @@ define_type (int level, const char *name, const char *basename, Type *t, int typ
size_t max_memno = 0;
size_t bitset_size;
if (t->symbol && t->symbol->emitted_definition)
break;
memset(&i, 0, sizeof(i));
/*
* range.max implies the size of the base unsigned integer used for the
* bitfield members. If it's less than or equal to UINT_MAX, then that
@@ -827,7 +834,7 @@ define_type (int level, const char *name, const char *basename, Type *t, int typ
fprintf (headerfile, "heim_bit_string %s;\n", name);
else {
int pos = 0;
getnewbasename(&newbasename, typedefp, basename, name);
getnewbasename(&newbasename, typedefp || level == 0, basename, name);
fprintf (headerfile, "struct %s {\n", newbasename);
HEIM_TAILQ_FOREACH(m, t->members, members) {
@@ -876,6 +883,9 @@ define_type (int level, const char *name, const char *basename, Type *t, int typ
case TEnumerated: {
Member *m;
if (t->symbol && t->symbol->emitted_definition)
break;
label_prefix = prefix_enum ? name : (enum_prefix ? enum_prefix : "");
label_prefix_sep = prefix_enum ? "_" : "";
space(level);
@@ -897,7 +907,7 @@ define_type (int level, const char *name, const char *basename, Type *t, int typ
case TSequence: {
Member *m;
getnewbasename(&newbasename, typedefp, basename, name);
getnewbasename(&newbasename, typedefp || level == 0, basename, name);
space(level);
fprintf (headerfile, "struct %s {\n", newbasename);
@@ -927,12 +937,11 @@ define_type (int level, const char *name, const char *basename, Type *t, int typ
Type i;
struct range range = { 0, UINT_MAX };
getnewbasename(&newbasename, typedefp, basename, name);
getnewbasename(&newbasename, typedefp || level == 0, basename, name);
memset(&i, 0, sizeof(i));
i.type = TInteger;
i.range = &range;
i.members = NULL;
i.constraint = NULL;
space(level);
fprintf (headerfile, "struct %s {\n", newbasename);
@@ -955,13 +964,13 @@ define_type (int level, const char *name, const char *basename, Type *t, int typ
fprintf (headerfile, "heim_general_string %s;\n", name);
break;
case TTag:
define_type (level, name, basename, t->subtype, typedefp, preservep);
define_type (level, name, basename, t->subtype, typedefp, preservep);
break;
case TChoice: {
int first = 1;
Member *m;
getnewbasename(&newbasename, typedefp, basename, name);
getnewbasename(&newbasename, typedefp || level == 0, basename, name);
space(level);
fprintf (headerfile, "struct %s {\n", newbasename);
@@ -1050,24 +1059,229 @@ define_type (int level, const char *name, const char *basename, Type *t, int typ
default:
abort ();
}
if (newbasename)
free(newbasename);
free(newbasename);
}
static void
declare_type(const Symbol *s, Type *t, int typedefp)
{
char *newbasename = NULL;
if (typedefp)
fprintf(headerfile, "typedef ");
switch (t->type) {
case TType:
define_type(0, s->gen_name, s->gen_name, s->type, TRUE, TRUE);
if (template_flag)
generate_template_type_forward(s->gen_name);
emitted_declaration(s);
return;
case TInteger:
case TBoolean:
case TOctetString:
case TBitString:
case TEnumerated:
case TGeneralizedTime:
case TGeneralString:
case TTeletexString:
case TUTCTime:
case TUTF8String:
case TPrintableString:
case TIA5String:
case TBMPString:
case TUniversalString:
case TVisibleString:
case TOID :
case TNull:
define_type(0, s->gen_name, s->gen_name, s->type, TRUE, TRUE);
if (template_flag)
generate_template_type_forward(s->gen_name);
emitted_declaration(s);
emitted_definition(s);
return;
case TTag:
declare_type(s, t->subtype, FALSE);
emitted_declaration(s);
return;
default:
break;
}
switch (t->type) {
case TSet:
case TSequence:
getnewbasename(&newbasename, TRUE, s->gen_name, s->gen_name);
fprintf(headerfile, "struct %s %s;\n", newbasename, s->gen_name);
break;
case TSetOf:
case TSequenceOf:
getnewbasename(&newbasename, TRUE, s->gen_name, s->gen_name);
fprintf(headerfile, "struct %s %s;\n", newbasename, s->gen_name);
break;
case TChoice:
getnewbasename(&newbasename, TRUE, s->gen_name, s->gen_name);
fprintf(headerfile, "struct %s %s;\n", newbasename, s->gen_name);
break;
default:
abort ();
}
free(newbasename);
emitted_declaration(s);
}
static void generate_subtypes_header_helper(const Member *m);
static void generate_type_header(const Symbol *);
static void
generate_subtypes_header_helper(const Member *m)
{
Member *sm;
Symbol *s;
if (m->ellipsis)
return;
if (m->type->symbol && (s = getsym(m->type->symbol->name)) &&
!s->emitted_definition) {
/* A field of some named type; recurse */
if (!m->optional && !m->defval)
generate_type_header(s);
return;
}
if (!m->type->subtype && !m->type->members)
return;
if (m->type->type == TTag &&
m->type->subtype && m->type->subtype->symbol &&
(s = getsym(m->type->subtype->symbol->name))) {
if (!m->optional && !m->defval)
generate_type_header(s);
return;
}
if (m->type->subtype) {
switch (m->type->subtype->type) {
case TSet:
case TSequence:
case TChoice:
break;
default:
return;
}
/* A field of some anonymous (inlined) structured type */
HEIM_TAILQ_FOREACH(sm, m->type->subtype->members, members) {
generate_subtypes_header_helper(sm);
}
}
if (m->type->members) {
HEIM_TAILQ_FOREACH(sm, m->type->members, members) {
generate_subtypes_header_helper(sm);
}
}
}
static void
generate_subtypes_header(const Symbol *s)
{
Type *t = s->type;
Member *m;
/*
* Recurse down structured types to make sure top-level types get
* defined before they are referenced.
*
* We'll take care to skip OPTIONAL member fields of constructed types so
* that we can have circular types like:
*
* Foo ::= SEQUENCE {
* bar Bar OPTIONAL
* }
*
* Bar ::= SEQUENCE {
* foo Foo OPTIONAL
* }
*
* not unlike XDR, which uses `*' to mean "optional", except in XDR it's
* called a "pointer". With some care we should be able to eventually
* support the silly XDR linked list example:
*
* ListOfFoo ::= SEQUENCE {
* someField SomeType,
* next ListOfFoo OPTIONAL
* }
*
* Not that anyone needs it -- just use a SEQUENCE OF and be done.
*/
while (t->type == TTag && t->subtype) {
switch (t->subtype->type) {
case TTag:
case TSet:
case TSequence:
case TChoice:
t = t->subtype;
continue;
default:
break;
}
break;
}
switch (t->type) {
default: return;
case TType:
if (t->symbol && (s = getsym(t->symbol->name)))
generate_type_header(s);
return;
case TSet:
case TSequence:
case TChoice:
break;
}
HEIM_TAILQ_FOREACH(m, t->members, members) {
generate_subtypes_header_helper(m);
}
}
static void
generate_type_header (const Symbol *s)
{
int preservep = preserve_type(s->name) ? TRUE : FALSE;
fprintf (headerfile, "/*\n");
fprintf (headerfile, "%s ::= ", s->name);
/*
* Recurse down the types of member fields of `s' to make sure that
* referenced types have had their definitions emitted already if the
* member fields are not OPTIONAL/DEFAULTed.
*/
if (s->type)
generate_subtypes_header(s);
if (!s->type)
return;
fprintf(headerfile, "/*\n");
fprintf(headerfile, "%s ::= ", s->name);
define_asn1 (0, s->type);
fprintf (headerfile, "\n*/\n\n");
fprintf(headerfile, "\n*/\n\n");
fprintf (headerfile, "typedef ");
define_type (0, s->gen_name, s->gen_name, s->type, TRUE, preservep);
if (s->emitted_definition)
return;
fprintf (headerfile, "\n");
fprintf(headerfile, "typedef ");
define_type(0, s->gen_name, s->gen_name, s->type, TRUE,
preserve_type(s->name) ? TRUE : FALSE);
fprintf(headerfile, "\n");
if (template_flag)
generate_template_type_forward(s->gen_name);
emitted_definition(s);
}
void
generate_type_header_forwards(const Symbol *s)
{
declare_type(s, s->type, TRUE);
fprintf(headerfile, "\n");
}
void