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puddly
213ddf8823
Compared to the baseline, -456 bytes of flash (90% of no lookup) but claw back 3x the performance
42 lines
1.4 KiB
C++
42 lines
1.4 KiB
C++
#include "ash_protocol.h"
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namespace esphome::zigbee_proxy {
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static const uint16_t CRC_NIBBLE_TABLE[16] = {0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7,
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0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF};
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uint16_t ash_crc16(const uint8_t *data, size_t length, uint16_t init) {
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uint16_t crc = init;
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for (size_t i = 0; i < length; i++) {
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crc = static_cast<uint16_t>(crc << 4) ^ CRC_NIBBLE_TABLE[(crc >> 12) ^ (data[i] >> 4)];
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crc = static_cast<uint16_t>(crc << 4) ^ CRC_NIBBLE_TABLE[(crc >> 12) ^ (data[i] & 0x0F)];
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}
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return crc;
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}
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// Appends a byte with ASH stuffing; the caller sized `output` for the worst case.
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static void append_byte_stuffed(uint8_t *output, size_t &pos, uint8_t byte) {
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if (ash_is_reserved(byte)) {
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output[pos++] = ASH_ESCAPE_BYTE;
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output[pos++] = byte ^ ASH_XOR_BYTE;
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} else {
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output[pos++] = byte;
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}
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}
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size_t ash_build_ack_frame(uint8_t *output, uint8_t ack_num) {
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// ACK control byte: 100nrPPP, where PPP is the next frame number expected
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const uint8_t control = 0x80 | (ack_num & ASH_MAX_SEQUENCE);
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const uint16_t crc = ash_crc16(&control, 1);
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size_t pos = 0;
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output[pos++] = ASH_FLAG_BYTE;
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append_byte_stuffed(output, pos, control);
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append_byte_stuffed(output, pos, (crc >> 8) & 0xFF);
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append_byte_stuffed(output, pos, crc & 0xFF);
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output[pos++] = ASH_FLAG_BYTE;
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return pos;
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}
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} // namespace esphome::zigbee_proxy
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