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[api] Add constexpr optimizations to protobuf encoding

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This commit is contained in:
J. Nick Koston
2025-08-11 14:36:31 -05:00
parent 45b88f2da9
commit 1bd4098cea
1 changed files with 36 additions and 40 deletions
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76
esphome/components/api/proto.h
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@@ -15,6 +15,23 @@
namespace esphome::api {
// Helper functions for ZigZag encoding/decoding
static constexpr uint32_t encode_zigzag32(int32_t value) {
return (static_cast<uint32_t>(value) << 1) ^ (static_cast<uint32_t>(value >> 31));
}
static constexpr uint64_t encode_zigzag64(int64_t value) {
return (static_cast<uint64_t>(value) << 1) ^ (static_cast<uint64_t>(value >> 63));
}
static constexpr int32_t decode_zigzag32(uint32_t value) {
return (value & 1) ? static_cast<int32_t>(~(value >> 1)) : static_cast<int32_t>(value >> 1);
}
static constexpr int64_t decode_zigzag64(uint64_t value) {
return (value & 1) ? static_cast<int64_t>(~(value >> 1)) : static_cast<int64_t>(value >> 1);
}
/*
* StringRef Ownership Model for API Protocol Messages
* ===================================================
@@ -87,33 +104,25 @@ class ProtoVarInt {
return {}; // Incomplete or invalid varint
}
uint16_t as_uint16() const { return this->value_; }
uint32_t as_uint32() const { return this->value_; }
uint64_t as_uint64() const { return this->value_; }
bool as_bool() const { return this->value_; }
int32_t as_int32() const {
constexpr uint16_t as_uint16() const { return this->value_; }
constexpr uint32_t as_uint32() const { return this->value_; }
constexpr uint64_t as_uint64() const { return this->value_; }
constexpr bool as_bool() const { return this->value_; }
constexpr int32_t as_int32() const {
// Not ZigZag encoded
return static_cast<int32_t>(this->as_int64());
}
int64_t as_int64() const {
constexpr int64_t as_int64() const {
// Not ZigZag encoded
return static_cast<int64_t>(this->value_);
}
int32_t as_sint32() const {
constexpr int32_t as_sint32() const {
// with ZigZag encoding
if (this->value_ & 1) {
return static_cast<int32_t>(~(this->value_ >> 1));
} else {
return static_cast<int32_t>(this->value_ >> 1);
}
return decode_zigzag32(static_cast<uint32_t>(this->value_));
}
int64_t as_sint64() const {
constexpr int64_t as_sint64() const {
// with ZigZag encoding
if (this->value_ & 1) {
return static_cast<int64_t>(~(this->value_ >> 1));
} else {
return static_cast<int64_t>(this->value_ >> 1);
}
return decode_zigzag64(this->value_);
}
/**
* Encode the varint value to a pre-allocated buffer without bounds checking.
@@ -309,22 +318,10 @@ class ProtoWriteBuffer {
this->encode_uint64(field_id, static_cast<uint64_t>(value), force);
}
void encode_sint32(uint32_t field_id, int32_t value, bool force = false) {
uint32_t uvalue;
if (value < 0) {
uvalue = ~(value << 1);
} else {
uvalue = value << 1;
}
this->encode_uint32(field_id, uvalue, force);
this->encode_uint32(field_id, encode_zigzag32(value), force);
}
void encode_sint64(uint32_t field_id, int64_t value, bool force = false) {
uint64_t uvalue;
if (value < 0) {
uvalue = ~(value << 1);
} else {
uvalue = value << 1;
}
this->encode_uint64(field_id, uvalue, force);
this->encode_uint64(field_id, encode_zigzag64(value), force);
}
void encode_message(uint32_t field_id, const ProtoMessage &value, bool force = false);
std::vector<uint8_t> *get_buffer() const { return buffer_; }
@@ -395,7 +392,7 @@ class ProtoSize {
* @param value The uint32_t value to calculate size for
* @return The number of bytes needed to encode the value
*/
static inline uint32_t varint(uint32_t value) {
static constexpr uint32_t varint(uint32_t value) {
// Optimized varint size calculation using leading zeros
// Each 7 bits requires one byte in the varint encoding
if (value < 128)
@@ -419,7 +416,7 @@ class ProtoSize {
* @param value The uint64_t value to calculate size for
* @return The number of bytes needed to encode the value
*/
static inline uint32_t varint(uint64_t value) {
static constexpr uint32_t varint(uint64_t value) {
// Handle common case of values fitting in uint32_t (vast majority of use cases)
if (value <= UINT32_MAX) {
return varint(static_cast<uint32_t>(value));
@@ -450,7 +447,7 @@ class ProtoSize {
* @param value The int32_t value to calculate size for
* @return The number of bytes needed to encode the value
*/
static inline uint32_t varint(int32_t value) {
static constexpr uint32_t varint(int32_t value) {
// Negative values are sign-extended to 64 bits in protocol buffers,
// which always results in a 10-byte varint for negative int32
if (value < 0) {
@@ -466,7 +463,7 @@ class ProtoSize {
* @param value The int64_t value to calculate size for
* @return The number of bytes needed to encode the value
*/
static inline uint32_t varint(int64_t value) {
static constexpr uint32_t varint(int64_t value) {
// For int64_t, we convert to uint64_t and calculate the size
// This works because the bit pattern determines the encoding size,
// and we've handled negative int32 values as a special case above
@@ -480,7 +477,7 @@ class ProtoSize {
* @param type The wire type value (from the WireType enum in the protobuf spec)
* @return The number of bytes needed to encode the field ID and wire type
*/
static inline uint32_t field(uint32_t field_id, uint32_t type) {
static constexpr uint32_t field(uint32_t field_id, uint32_t type) {
uint32_t tag = (field_id << 3) | (type & 0b111);
return varint(tag);
}
@@ -607,9 +604,8 @@ class ProtoSize {
*/
inline void add_sint32_force(uint32_t field_id_size, int32_t value) {
// Always calculate size when force is true
// ZigZag encoding for sint32: (n << 1) ^ (n >> 31)
uint32_t zigzag = (static_cast<uint32_t>(value) << 1) ^ (static_cast<uint32_t>(value >> 31));
total_size_ += field_id_size + varint(zigzag);
// ZigZag encoding for sint32
total_size_ += field_id_size + varint(encode_zigzag32(value));
}
/**