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[api] Inline varint encoding in write_plaintext_header

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Replace two out-of-line encode_varint_to_buffer calls with direct
byte writes using the already-computed varint lengths. Eliminates
function call overhead (register save/restore) from the batch loop
and removes the 34-byte out-of-line encode_varint_to_buffer function
which had no other callers.
This commit is contained in:
J. Nick Koston
2026-04-01 22:43:58 -10:00
parent 1f455e7737
commit a8c6c55de2
1 changed files with 24 additions and 5 deletions
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esphome/components/api/api_frame_helper_plaintext.cpp
+24 -5
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@@ -276,12 +276,31 @@ ESPHOME_ALWAYS_INLINE static inline uint8_t write_plaintext_header(uint8_t *buf_
// So we write the header starting at offset + HEADER_PADDING - total_header_len
uint32_t header_offset = APIPlaintextFrameHelper::HEADER_PADDING - total_header_len;
// Write the plaintext header
buf_start[header_offset] = 0x00; // indicator
// Write the plaintext header with inline varint encoding.
// We already know the varint lengths so we can write the exact bytes directly
// without a generic loop, avoiding function call overhead.
uint8_t *p = buf_start + header_offset;
*p++ = 0x00; // indicator
// Encode varints directly into buffer
encode_varint_to_buffer(msg.payload_size, buf_start + header_offset + 1);
encode_varint_to_buffer(msg.message_type, buf_start + header_offset + 1 + size_varint_len);
// Encode payload size varint (1-3 bytes)
uint16_t size_val = msg.payload_size;
if (size_varint_len >= 2) {
*p++ = static_cast<uint8_t>(size_val | 0x80);
size_val >>= 7;
if (size_varint_len == 3) {
*p++ = static_cast<uint8_t>(size_val | 0x80);
size_val >>= 7;
}
}
*p++ = static_cast<uint8_t>(size_val);
// Encode message type varint (1-2 bytes)
if (type_varint_len == 2) {
*p++ = static_cast<uint8_t>(msg.message_type | 0x80);
*p = static_cast<uint8_t>(msg.message_type >> 7);
} else {
*p = msg.message_type;
}
return total_header_len;
}