Generate tables for libcanard table coding system

dronecan_dsdlc_helpers.py

@@ -270,3 +270,145 @@ def mkdir_p(path):
             pass
         else:
             raise
+
+def build_coding_table(msg_underscored_name, msg_union, msg_max_bitlen, msg_fields):
+    if len(msg_fields) == 0: # cheaper to encode an empty message without a table
+        return None
+    if int((msg_max_bitlen+7)/8) > 65535: # too big to encode
+        return None
+
+    table = _build_coding_table_core(msg_underscored_name, msg_union, msg_fields, True)
+    if table is None: return None
+    if len(table) > 65536: # too big to encode
+        return None
+
+    # turn table description into a list of strings
+    table_str = []
+    for kind, relative, *params in table:
+        if kind is None:
+            # number of list items must exactly equal number of entries!
+            table_str.append("// auxiliary entry")
+        else:
+            params = ", ".join(str(v) for v in params)
+            table_str.append(f"{kind}({params}),")
+
+    return table_str
+
+def _build_coding_table_core(obj_underscored_name, obj_union, obj_fields, tao):
+    table = []
+
+    if obj_union: # unions are a special case
+        if len(obj_fields) == 0 or len(obj_fields) > 255: # out of range to encode
+            return None
+
+        # entries to describe the union
+        table.append(("CANARD_TABLE_CODING_ENTRIES_UNION", False,
+            f"offsetof(struct {obj_underscored_name}, {obj_fields[0].name})", len(obj_fields),
+            union_msg_tag_bitlen_from_num_fields(len(obj_fields)),
+            f"offsetof(struct {obj_underscored_name}, union_tag)"
+        ))
+        table.append((None, None)) # dummy auxiliary entry for accurate entry count
+
+        field_entries = []
+        for field in obj_fields:
+            t = field.type
+
+            if isinstance(t, dronecan.dsdl.parser.CompoundType):
+                sub = _build_coding_table_core(field.name, t.union, t.fields, tao)
+            else:
+                sub = _build_coding_table_core(field.name, False, [t], tao)
+            if sub is None: return None
+            if len(sub) > 255: # too many entries to encode
+                return None
+
+            # entry to describe this field
+            table.append(("CANARD_TABLE_CODING_ENTRY_UNION_FIELD", True, len(sub)))
+
+            for s_kind, s_relative, *s_params in sub:
+                if s_kind is None:
+                    field_entries.append((None, None))
+                else:
+                    # all entries must have a relative offset
+                    field_entries.append((s_kind, True, *s_params))
+
+        table.extend(field_entries)
+        return table
+
+    for field_idx, field in enumerate(obj_fields):
+        tao_eligible = tao and field_idx == len(obj_fields)-1
+        if isinstance(field, dronecan.dsdl.parser.Type):
+            t = field
+            offset = 0
+        else:
+            t = field.type
+            offset = f"offsetof(struct {obj_underscored_name}, {field.name})"
+        field_name = t.full_name.replace('.', '_').split("[")[0]
+        if isinstance(t, dronecan.dsdl.parser.PrimitiveType):
+            if t.kind == t.KIND_BOOLEAN or t.kind == t.KIND_UNSIGNED_INT:
+                ts = "CANARD_TABLE_CODING_UNSIGNED"
+            elif t.kind == t.KIND_SIGNED_INT:
+                ts = "CANARD_TABLE_CODING_SIGNED"
+            elif t.kind == t.KIND_FLOAT:
+                ts = "CANARD_TABLE_CODING_FLOAT"
+            table.append(("CANARD_TABLE_CODING_ENTRY_PRIMITIVE", False, offset, ts, t.bitlen))
+        elif isinstance(t, dronecan.dsdl.parser.VoidType):
+            table.append(("CANARD_TABLE_CODING_ENTRY_VOID", True, t.bitlen))
+        elif isinstance(t, dronecan.dsdl.parser.CompoundType):
+            sub = _build_coding_table_core(field_name, t.union, t.fields, tao_eligible) # build the compound table
+            if sub is None: return None
+
+            # prepend offset to each entry that's not relative
+            for s_kind, s_relative, *s_params in sub:
+                if s_kind is None:
+                    table.append((None, None))
+                else:
+                    if not s_relative: # not relative, needs offset adjusted
+                        if s_kind.startswith("CANARD_TABLE_CODING_ENTRIES_ARRAY_DYNAMIC") \
+                                or s_kind == "CANARD_TABLE_CODING_ENTRIES_UNION": # has a second offset
+                            s_params = (*s_params[:-1], f"{offset}+{s_params[-1]}")
+                        table.append((s_kind, s_relative, f"{offset}+{s_params[0]}", *s_params[1:]))
+                    else:
+                        table.append((s_kind, s_relative, *s_params))
+        elif isinstance(t, dronecan.dsdl.parser.ArrayType):
+            if t.max_size > 65535: # too big to encode
+                return None
+
+            use_tao = t.mode == t.MODE_DYNAMIC and tao_eligible and t.value_type.get_min_bitlen() >= 8
+
+            if isinstance(t.value_type, dronecan.dsdl.parser.CompoundType):
+                sub = _build_coding_table_core(field_name, t.value_type.union, t.value_type.fields, tao_eligible and not use_tao)
+            else:
+                sub = _build_coding_table_core(field_name, False, [t.value_type], tao_eligible and not use_tao)
+            if sub is None: return None
+            if len(sub) == 0: # array of empty objects???
+                assert False
+            if len(sub) > 256: # too many entries to encode
+                return None
+
+            # entries for the array itself
+            if t.mode == t.MODE_STATIC:
+                table.append(("CANARD_TABLE_CODING_ENTRIES_ARRAY_STATIC", False,
+                    offset, len(sub), f"sizeof({dronecan_type_to_ctype(t.value_type)})", t.max_size
+                ))
+                table.append((None, None)) # dummy auxiliary entry for accurate entry count
+            elif t.mode == t.MODE_DYNAMIC:
+                # same cdef as field_cdef
+                cdef = 'struct { uint%u_t len; %s data[%u]; }' % (c_int_type_bitlen(array_len_field_bitlen(t)), dronecan_type_to_ctype(t.value_type), t.max_size)
+                table.append((f"CANARD_TABLE_CODING_ENTRIES_ARRAY_DYNAMIC", False,
+                    f"{offset}+offsetof({cdef}, data)", 1 if use_tao else 0, len(sub), f"sizeof({dronecan_type_to_ctype(t.value_type)})", t.max_size,
+                    t.max_size.bit_length(), f"{offset}+offsetof({cdef}, len)"
+                ))
+                table.extend(((None, None),)*2) # dummy auxiliary entries for accurate entry count
+            else:
+                assert False # unknown type
+
+            for s_kind, s_relative, *s_params in sub:
+                if s_kind is None:
+                    table.append((None, None))
+                else:
+                    # all entries must have a relative offset
+                    table.append((s_kind, True, *s_params))
+        else:
+            assert False # unknown type
+
+    return table

templates/msg.c.em

@@ -11,14 +11,27 @@
 #include <test_helpers.h>
 #endif
 
-uint32_t @(msg_underscored_name)_encode(@(msg_c_type)* msg, uint8_t* buffer
+@{coding_table = build_coding_table(msg_underscored_name, msg_union, msg_max_bitlen, msg_fields)}
+@[if coding_table is not None]
+#if CANARD_ENABLE_TABLE_ENCODING || CANARD_ENABLE_TABLE_DECODING
+const CanardCodingTable _@(msg_underscored_name)_coding_table = {
+    .max_size = @(msg_define_name.upper())_MAX_SIZE,
+    .entries_max = @(len(coding_table))-1,
+    .entries = {
+@("\n".join("        "+e for e in coding_table))
+    },
+};
+#endif
+@[end if]
+
+uint32_t _@(msg_underscored_name)_encode(@(msg_c_type)* msg, uint8_t* buffer
 #if CANARD_ENABLE_TAO_OPTION
     , bool tao
 #endif
 ) {
     uint32_t bit_ofs = 0;
     memset(buffer, 0, @(msg_define_name.upper())_MAX_SIZE);
-    _@(msg_underscored_name)_encode(buffer, &bit_ofs, msg, 
+    __@(msg_underscored_name)_encode(buffer, &bit_ofs, msg,
 #if CANARD_ENABLE_TAO_OPTION
     tao
 #else
@@ -31,14 +44,14 @@ uint32_t @(msg_underscored_name)_encode(@(msg_c_type)* msg, uint8_t* buffer
 /*
   return true if the decode is invalid
  */
-bool @(msg_underscored_name)_decode(const CanardRxTransfer* transfer, @(msg_c_type)* msg) {
+bool _@(msg_underscored_name)_decode(const CanardRxTransfer* transfer, @(msg_c_type)* msg) {
 #if CANARD_ENABLE_TAO_OPTION
     if (transfer->tao && (transfer->payload_len > @(msg_define_name.upper())_MAX_SIZE)) {
         return true; /* invalid payload length */
     }
 #endif
     uint32_t bit_ofs = 0;
-    if (_@(msg_underscored_name)_decode(transfer, &bit_ofs, msg,
+    if (__@(msg_underscored_name)_decode(transfer, &bit_ofs, msg,
 #if CANARD_ENABLE_TAO_OPTION
     transfer->tao
 #else

templates/msg.h.em

@@ -69,18 +69,76 @@ extern "C"
 {
 #endif
 
-uint32_t @(msg_underscored_name)_encode(@(msg_c_type)* msg, uint8_t* buffer
+uint32_t _@(msg_underscored_name)_encode(@(msg_c_type)* msg, uint8_t* buffer
 #if CANARD_ENABLE_TAO_OPTION
     , bool tao
 #endif
 );
-bool @(msg_underscored_name)_decode(const CanardRxTransfer* transfer, @(msg_c_type)* msg);
+bool _@(msg_underscored_name)_decode(const CanardRxTransfer* transfer, @(msg_c_type)* msg);
+
+@{coding_table = build_coding_table(msg_underscored_name, msg_union, msg_max_bitlen, msg_fields)}
+@[if coding_table is not None]
+#if CANARD_ENABLE_TABLE_ENCODING || CANARD_ENABLE_TABLE_DECODING
+extern const CanardCodingTable _@(msg_underscored_name)_coding_table;
+#endif
+@[end if]
+
+static inline uint32_t @(msg_underscored_name)_encode(@(msg_c_type)* msg, uint8_t* buffer
+#if CANARD_ENABLE_TAO_OPTION
+    , bool tao
+#endif
+) {
+@[if msg_max_bitlen == 0]
+    (void)msg;
+    (void)buffer;
+#if CANARD_ENABLE_TAO_OPTION
+    (void)tao;
+#endif
+
+    return 0; // 0-length message encodes to 0 bytes
+@[else]
+@[if coding_table is not None]
+#if CANARD_ENABLE_TABLE_ENCODING
+    if (sizeof(@(msg_c_type)) <= 65535) { // ensure offsets fit in table
+        return canardTableEncodeMessage(&_@(msg_underscored_name)_coding_table, buffer, msg
+#if CANARD_ENABLE_TAO_OPTION
+        , tao
+#endif
+        );
+    }
+#endif
+@[end if]
+    return _@(msg_underscored_name)_encode(msg, buffer
+#if CANARD_ENABLE_TAO_OPTION
+    , tao
+#endif
+    );
+@[end if]
+}
+
+static inline bool @(msg_underscored_name)_decode(const CanardRxTransfer* transfer, @(msg_c_type)* msg) {
+@[if msg_max_bitlen == 0]
+    (void)msg;
+
+    // all transports accurately convey a payload length of 0 bytes so any payload is an error
+    return transfer->payload_len != 0;
+@[else]
+@[if coding_table is not None]
+#if CANARD_ENABLE_TABLE_DECODING
+    if (sizeof(@(msg_c_type)) <= 65535) { // ensure offsets fit in table
+        return canardTableDecodeMessage(&_@(msg_underscored_name)_coding_table, transfer, msg);
+    }
+#endif
+@[end if]
+    return _@(msg_underscored_name)_decode(transfer, msg);
+@[end if]
+}
 
 #if defined(CANARD_DSDLC_INTERNAL)
 @{indent = 0}@{ind = '    '*indent}@
-static inline void _@(msg_underscored_name)_encode(uint8_t* buffer, uint32_t* bit_ofs, @(msg_c_type)* msg, bool tao);
-static inline bool _@(msg_underscored_name)_decode(const CanardRxTransfer* transfer, uint32_t* bit_ofs, @(msg_c_type)* msg, bool tao);
-void _@(msg_underscored_name)_encode(uint8_t* buffer, uint32_t* bit_ofs, @(msg_c_type)* msg, bool tao) {
+static inline void __@(msg_underscored_name)_encode(uint8_t* buffer, uint32_t* bit_ofs, @(msg_c_type)* msg, bool tao);
+static inline bool __@(msg_underscored_name)_decode(const CanardRxTransfer* transfer, uint32_t* bit_ofs, @(msg_c_type)* msg, bool tao);
+void __@(msg_underscored_name)_encode(uint8_t* buffer, uint32_t* bit_ofs, @(msg_c_type)* msg, bool tao) {
 @{indent += 1}@{ind = '    '*indent}@
 @(ind)(void)buffer;
 @(ind)(void)bit_ofs;
@@ -101,7 +159,7 @@ void _@(msg_underscored_name)_encode(uint8_t* buffer, uint32_t* bit_ofs, @(msg_c
 @{indent += 1}@{ind = '    '*indent}@
 @[      end if]@
 @[      if field.type.category == field.type.CATEGORY_COMPOUND]@
-@(ind)_@(underscored_name(field.type))_encode(buffer, bit_ofs, &msg->@(field.name), @('tao' if (field == msg_fields[-1] or msg_union) else 'false'));
+@(ind)__@(underscored_name(field.type))_encode(buffer, bit_ofs, &msg->@(field.name), @('tao' if (field == msg_fields[-1] or msg_union) else 'false'));
 @[      elif field.type.category == field.type.CATEGORY_PRIMITIVE]@
 @[        if field.type.kind == field.type.KIND_FLOAT and field.type.bitlen == 16]@
 @(ind){
@@ -144,7 +202,7 @@ void _@(msg_underscored_name)_encode(uint8_t* buffer, uint32_t* bit_ofs, @(msg_c
 @[          end if]@
 @(ind)*bit_ofs += @(field.type.value_type.bitlen);
 @[        elif field.type.value_type.category == field.type.value_type.CATEGORY_COMPOUND]@
-@(ind)_@(underscored_name(field.type.value_type))_encode(buffer, bit_ofs, &msg->@(field_get_data(field))[i], @[if field == msg_fields[-1] and field.type.value_type.get_min_bitlen() < 8]tao && i==msg->@(field.name).len@[else]false@[end if]@);
+@(ind)__@(underscored_name(field.type.value_type))_encode(buffer, bit_ofs, &msg->@(field_get_data(field))[i], @[if field == msg_fields[-1] and field.type.value_type.get_min_bitlen() < 8]tao && i==msg->@(field.name).len@[else]false@[end if]@);
 @[        end if]@
 @{indent -= 1}@{ind = '    '*indent}@
 @(ind)}
@@ -167,7 +225,7 @@ void _@(msg_underscored_name)_encode(uint8_t* buffer, uint32_t* bit_ofs, @(msg_c
 /*
  decode @(msg_underscored_name), return true on failure, false on success
 */
-bool _@(msg_underscored_name)_decode(const CanardRxTransfer* transfer, uint32_t* bit_ofs, @(msg_c_type)* msg, bool tao) {
+bool __@(msg_underscored_name)_decode(const CanardRxTransfer* transfer, uint32_t* bit_ofs, @(msg_c_type)* msg, bool tao) {
 @{indent += 1}@{ind = '    '*indent}@
 @(ind)(void)transfer;
 @(ind)(void)bit_ofs;
@@ -194,7 +252,7 @@ bool _@(msg_underscored_name)_decode(const CanardRxTransfer* transfer, uint32_t*
 @{indent += 1}@{ind = '    '*indent}@
 @[      end if]@
 @[      if field.type.category == field.type.CATEGORY_COMPOUND]@
-@(ind)if (_@(underscored_name(field.type))_decode(transfer, bit_ofs, &msg->@(field.name), @('tao' if (field == msg_fields[-1] or msg_union) else 'false'))) {return true;}
+@(ind)if (__@(underscored_name(field.type))_decode(transfer, bit_ofs, &msg->@(field.name), @('tao' if (field == msg_fields[-1] or msg_union) else 'false'))) {return true;}
 @[      elif field.type.category == field.type.CATEGORY_PRIMITIVE]@
 @[        if field.type.kind == field.type.KIND_FLOAT and field.type.bitlen == 16]@
 @(ind){
@@ -235,7 +293,7 @@ bool _@(msg_underscored_name)_decode(const CanardRxTransfer* transfer, uint32_t*
 @(ind)uint32_t max_bits = (transfer->payload_len*8)-7; // TAO elements must be >= 8 bits
 @(ind)while (max_bits > *bit_ofs) {
 @{indent += 1}@{ind = '    '*indent}@
-@(ind)if (!max_len-- || _@(underscored_name(field.type.value_type))_decode(transfer, bit_ofs, &msg->@(field_get_data(field))[msg->@(field.name).len], @[if field == msg_fields[-1] and field.type.value_type.get_min_bitlen() < 8]tao && i==msg->@(field.name).len@[else]false@[end if]@)) {return true;}
+@(ind)if (!max_len-- || __@(underscored_name(field.type.value_type))_decode(transfer, bit_ofs, &msg->@(field_get_data(field))[msg->@(field.name).len], @[if field == msg_fields[-1] and field.type.value_type.get_min_bitlen() < 8]tao && i==msg->@(field.name).len@[else]false@[end if]@)) {return true;}
 @(ind)msg->@(field.name).len++;
 @{indent -= 1}@{ind = '    '*indent}@
 @(ind)}
@@ -269,7 +327,7 @@ bool _@(msg_underscored_name)_decode(const CanardRxTransfer* transfer, uint32_t*
 @[          end if]@
 @(ind)*bit_ofs += @(field.type.value_type.bitlen);
 @[        elif field.type.value_type.category == field.type.value_type.CATEGORY_COMPOUND]@
-@(ind)if (_@(underscored_name(field.type.value_type))_decode(transfer, bit_ofs, &msg->@(field_get_data(field))[i], @[if field == msg_fields[-1] and field.type.value_type.get_min_bitlen() < 8]tao && i==msg->@(field.name).len@[else]false@[end if]@)) {return true;}
+@(ind)if (__@(underscored_name(field.type.value_type))_decode(transfer, bit_ofs, &msg->@(field_get_data(field))[i], @[if field == msg_fields[-1] and field.type.value_type.get_min_bitlen() < 8]tao && i==msg->@(field.name).len@[else]false@[end if]@)) {return true;}
 @[        end if]@
 @{indent -= 1}@{ind = '    '*indent}@
 @(ind)}