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Introduce table coding system for program memory savings #70

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Introduce table coding system for program memory savings #70

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32ff91d
introduce skeleton for table coding system
tpwrules Jul 20, 2024
b9e5198
table code types containing primitive and void fields
tpwrules Jul 20, 2024
5ccd484
table code types containing static arrays
tpwrules Jul 20, 2024
e8d1797
table code dynamic arrays, including tail array optimization
tpwrules Jul 20, 2024
dd2aca9
table code types containing unions
tpwrules Jul 21, 2024
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354 changes: 354 additions & 0 deletions canard.c
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Original file line number Diff line number Diff line change
Expand Up @@ -994,6 +994,68 @@ void canardEncodeScalar(void* destination,
copyBitArray(&storage.bytes[0], 0, bit_length, (uint8_t*) destination, bit_offset);
}

#if CANARD_ENABLE_TABLE_DECODING
bool canardTableDecodeMessage(const CanardCodingTable* table,
const CanardRxTransfer* transfer,
void* msg)
{
#if CANARD_ENABLE_TAO_OPTION
if (transfer->tao && (transfer->payload_len > table->max_size)) {
return true; // invalid length
}
#endif

uint32_t bit_ofs = 0;
const CanardCodingTableEntry* entry = &table->entries[0];
const CanardCodingTableEntry* entry_last = &table->entries[table->entries_max];
if (tableDecodeCore(entry, entry_last, transfer, &bit_ofs, msg,
#if CANARD_ENABLE_TAO_OPTION
transfer->tao
#else
true
#endif
)) {
return true; // decode failure
}

const uint32_t byte_len = (bit_ofs+7U)/8U;
#if CANARD_ENABLE_TAO_OPTION
// if this could be CANFD then the dlc could indicating more bytes than
// we actually have
if (!transfer->tao) {
return byte_len > transfer->payload_len;
}
#endif
return byte_len != transfer->payload_len;
}
#endif

#if CANARD_ENABLE_TABLE_ENCODING
uint32_t canardTableEncodeMessage(const CanardCodingTable* table,
uint8_t* buffer,
const void* msg
#if CANARD_ENABLE_TAO_OPTION
, bool tao
#endif
)
{
memset(buffer, 0, table->max_size);

uint32_t bit_ofs = 0;
const CanardCodingTableEntry* entry = &table->entries[0];
const CanardCodingTableEntry* entry_last = &table->entries[table->entries_max];
tableEncodeCore(entry, entry_last, buffer, &bit_ofs, msg,
#if CANARD_ENABLE_TAO_OPTION
tao
#else
true
#endif
);

return ((bit_ofs+7)/8);
}
#endif

void canardReleaseRxTransferPayload(CanardInstance* ins, CanardRxTransfer* transfer)
{
while (transfer->payload_middle != NULL)
Expand Down Expand Up @@ -1825,6 +1887,298 @@ CANARD_INTERNAL void swapByteOrder(void* data, unsigned size)
}
}

/**
* Table coding functions
*/
#if CANARD_ENABLE_TABLE_DECODING
CANARD_INTERNAL bool tableDecodeCore(const CanardCodingTableEntry* entry,
const CanardCodingTableEntry* entry_last,
const CanardRxTransfer* transfer,
uint32_t* bit_ofs,
void* msg,
bool tao)
{
do {
void* p = (char*)msg + entry->offset;
uint8_t type = entry->type;
uint8_t bitlen = entry->bitlen;

switch (type) {
case CANARD_TABLE_CODING_UNSIGNED:
case CANARD_TABLE_CODING_SIGNED:
case CANARD_TABLE_CODING_FLOAT: {
canardDecodeScalar(transfer, *bit_ofs, bitlen, type != CANARD_TABLE_CODING_UNSIGNED, p);
if (type == CANARD_TABLE_CODING_FLOAT && bitlen == 16) {
uint16_t float16_val = (uint16_t)*(int16_t*)p;
*(float*)p = canardConvertFloat16ToNativeFloat(float16_val);
}

*bit_ofs += bitlen;
break;
}

case CANARD_TABLE_CODING_VOID:
// nothing to decode for void
*bit_ofs += bitlen;
break;

case CANARD_TABLE_CODING_ARRAY_STATIC: {
const CanardCodingTableEntry* aux = ++entry;
const CanardCodingTableEntry* array_entry = ++entry;
const CanardCodingTableEntry* array_entry_last = array_entry + bitlen;
entry = array_entry_last; // point entry to last for ++entry at end of loop

uint16_t elems = aux->type | ((uint16_t)aux->bitlen << 8);
while (elems--) {
if (tableDecodeCore(array_entry, array_entry_last, transfer, bit_ofs, p, !elems && tao)) {
return true;
}
p = (char*)p + aux->offset;
}

break;
}

case CANARD_TABLE_CODING_ARRAY_DYNAMIC:
case CANARD_TABLE_CODING_ARRAY_DYNAMIC_TAO: {
const CanardCodingTableEntry* aux = ++entry;
const CanardCodingTableEntry* aux2 = ++entry;
const CanardCodingTableEntry* array_entry = ++entry;
const CanardCodingTableEntry* array_entry_last = array_entry + bitlen;
entry = array_entry_last; // point entry to last for ++entry at end of loop

uint16_t max_len = aux->type | ((uint16_t)aux->bitlen << 8);
void* len_p = ((char*)msg + aux2->offset);
uint8_t len_bitlen = aux2->bitlen;
if (type != CANARD_TABLE_CODING_ARRAY_DYNAMIC_TAO || !tao) {
// not using TAO
canardDecodeScalar(transfer, *bit_ofs, len_bitlen, false, len_p);
*bit_ofs += len_bitlen;

uint16_t elems;
if (len_bitlen <= 8) {
elems = *(uint8_t*)len_p;
} else { // 16 bits is max supported len
elems = *(uint16_t*)len_p;
}
if (elems > max_len) {
return true; // invalid value
}

while (elems--) {
if (tableDecodeCore(array_entry, array_entry_last, transfer, bit_ofs, p, !elems && tao)) {
return true;
}
p = (char*)p + aux->offset;
}
} else {
// TAO optimization in play
uint16_t elems = 0;
// TAO requires the element size to be at least 8 bits so if we have less we know we are done
uint32_t max_bits = (transfer->payload_len*8)-7;
while (max_bits > *bit_ofs) {
if (!max_len-- || tableDecodeCore(array_entry, array_entry_last, transfer, bit_ofs, p, false)) {
return true;
}
p = (char*)p + aux->offset;
elems++;
}
if (len_bitlen <= 8) {
*(uint8_t*)len_p = (uint8_t)elems;
} else { // 16 bits is max supported len
*(uint16_t*)len_p = elems;
}
}

break;
}

case CANARD_TABLE_CODING_UNION: {
uint8_t num_tags = bitlen;
const CanardCodingTableEntry* aux = ++entry;
const CanardCodingTableEntry* union_header = ++entry;
const CanardCodingTableEntry* union_entry = union_header + num_tags;

uint8_t union_tag;
uint8_t tag_bitlen = aux->bitlen;
canardDecodeScalar(transfer, *bit_ofs, tag_bitlen, false, &union_tag);
*bit_ofs += tag_bitlen;
if (union_tag >= num_tags) {
return true; // invalid value
}

void* tag_p = (char*)msg + aux->offset;
// we know 254 is the max tag value, but the chars taken is compiler dependent
if (sizeof(CanardCodingTableUnionEnum) == sizeof(uint8_t)) {
*(uint8_t*)tag_p = union_tag;
} else if (sizeof(CanardCodingTableUnionEnum) == sizeof(uint16_t)) {
*(uint16_t*)tag_p = union_tag;
} else if (sizeof(CanardCodingTableUnionEnum) == sizeof(uint32_t)) {
*(uint32_t*)tag_p = union_tag;
} else {
*(uint64_t*)tag_p = union_tag;
}

// check each tag so we can keep track of the entry pointers
for (uint8_t tag=0; tag<num_tags; tag++) {
uint8_t num_entries = (union_header++)->bitlen;
if (num_entries && tag == union_tag) { // can't decode 0 entries, so check that in addition to match
tableDecodeCore(union_entry, union_entry+num_entries-1, transfer, bit_ofs, p, tao);
}
union_entry += num_entries;
}

entry = union_entry - 1; // point entry to last for ++entry at end of loop

break;
}

default:
return true; // invalid type
}
} while (++entry <= entry_last);

return false; // success
}
#endif

#if CANARD_ENABLE_TABLE_ENCODING
CANARD_INTERNAL void tableEncodeCore(const CanardCodingTableEntry* entry,
const CanardCodingTableEntry* entry_last,
uint8_t* buffer,
uint32_t* bit_ofs,
const void* msg,
bool tao)
{
do {
const void* p = (const char*)msg + entry->offset;
uint8_t type = entry->type;
uint8_t bitlen = entry->bitlen;

switch (type) {
case CANARD_TABLE_CODING_UNSIGNED:
case CANARD_TABLE_CODING_SIGNED:
case CANARD_TABLE_CODING_FLOAT: {
uint16_t float16_val;
if (type == CANARD_TABLE_CODING_FLOAT && bitlen == 16) {
float16_val = canardConvertNativeFloatToFloat16(*(const float*)p);
p = &float16_val;
}
canardEncodeScalar(buffer, *bit_ofs, bitlen, p);

*bit_ofs += bitlen;
break;
}

case CANARD_TABLE_CODING_VOID:
// void encoding is taken care of by memset to 0 in the wrapper
*bit_ofs += bitlen;
break;

case CANARD_TABLE_CODING_ARRAY_STATIC: {
const CanardCodingTableEntry* aux = ++entry;
const CanardCodingTableEntry* array_entry = ++entry;
const CanardCodingTableEntry* array_entry_last = array_entry + bitlen;
entry = array_entry_last; // point entry to last for ++entry at end of loop

uint16_t elems = aux->type | ((uint16_t)aux->bitlen << 8);
while (elems--) {
tableEncodeCore(array_entry, array_entry_last, buffer, bit_ofs, p, !elems && tao);
p = (const char*)p + aux->offset;
}

break;
}

case CANARD_TABLE_CODING_ARRAY_DYNAMIC:
case CANARD_TABLE_CODING_ARRAY_DYNAMIC_TAO: {
const CanardCodingTableEntry* aux = ++entry;
const CanardCodingTableEntry* aux2 = ++entry;
const CanardCodingTableEntry* array_entry = ++entry;
const CanardCodingTableEntry* array_entry_last = array_entry + bitlen;
entry = array_entry_last; // point entry to last for ++entry at end of loop

uint16_t max_len = aux->type | ((uint16_t)aux->bitlen << 8);
const void* len_p = (const char*)msg + aux2->offset;
uint8_t len_bitlen = aux2->bitlen;

uint16_t elems;
if (len_bitlen <= 8) {
elems = *(const uint8_t*)len_p;
} else { // 16 bits is max supported len
elems = *(const uint16_t*)len_p;
}
if (elems > max_len) {
elems = max_len;
}

if (type != CANARD_TABLE_CODING_ARRAY_DYNAMIC_TAO || !tao) {
// encode the length value we have clamped to the maximum
uint8_t elems_8;
if (len_bitlen <= 8) {
elems_8 = (uint8_t)elems;
len_p = &elems_8;
} else { // 16 bits is max supported len
len_p = &elems;
}
canardEncodeScalar(buffer, *bit_ofs, len_bitlen, len_p);
*bit_ofs += len_bitlen;
}

int element_tao = type != CANARD_TABLE_CODING_ARRAY_DYNAMIC_TAO && tao;
while (elems--) {
tableEncodeCore(array_entry, array_entry_last, buffer, bit_ofs, p, !elems && element_tao);
p = (const char*)p + aux->offset;
}

break;
}

case CANARD_TABLE_CODING_UNION: {
uint8_t num_fields = bitlen;
const CanardCodingTableEntry* aux = ++entry;
const CanardCodingTableEntry* union_header = ++entry;
const CanardCodingTableEntry* union_entry = union_header + num_fields;

const void* tag_p = (const char*)msg + aux->offset;
uint8_t union_tag;
// we know 254 is the max tag value, but the chars taken is compiler dependent
if (sizeof(CanardCodingTableUnionEnum) == sizeof(uint8_t)) {
union_tag = (uint8_t)*(const uint8_t*)tag_p;
} else if (sizeof(CanardCodingTableUnionEnum) == sizeof(uint16_t)) {
union_tag = (uint16_t)*(const uint16_t*)tag_p;
} else if (sizeof(CanardCodingTableUnionEnum) == sizeof(uint32_t)) {
union_tag = (uint32_t)*(const uint32_t*)tag_p;
} else {
union_tag = (uint64_t)*(const uint64_t*)tag_p;
}
// the native type is an enum so assume it can't be out of range

uint8_t tag_bitlen = aux->bitlen;
canardEncodeScalar(buffer, *bit_ofs, tag_bitlen, &union_tag);
*bit_ofs += tag_bitlen;

// check each tag so we can keep track of the entry pointers
for (uint8_t tag=0; tag<num_fields; tag++) {
uint8_t num_entries = (union_header++)->bitlen;
if (num_entries && tag == union_tag) { // can't encode 0 entries, so check that in addition to match
tableEncodeCore(union_entry, union_entry+num_entries-1, buffer, bit_ofs, p, tao);
}
union_entry += num_entries;
}

entry = union_entry - 1; // point entry to last for ++entry at end of loop

break;
}

default:
return; // invalid type
}
} while (++entry <= entry_last);
}
#endif

/*
* CRC functions
*/
Expand Down
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