mirror of
https://github.com/mikecarper/MeshCore.git
synced 2026-09-01 23:58:20 +00:00
57 lines
1.5 KiB
C++
57 lines
1.5 KiB
C++
#pragma once
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#include <stddef.h>
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#include <stdint.h>
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namespace mesh {
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inline bool isUtf8Continuation(uint8_t byte) {
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return (byte & 0xC0) == 0x80;
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}
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inline size_t validUtf8PrefixLength(const char* text, size_t max_bytes) {
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if (text == nullptr) return 0;
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size_t offset = 0;
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while (text[offset] != '\0') {
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const uint8_t first = static_cast<uint8_t>(text[offset]);
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size_t sequence_length = 0;
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if (first <= 0x7F) {
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sequence_length = 1;
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} else if (first >= 0xC2 && first <= 0xDF) {
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sequence_length = 2;
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} else if (first >= 0xE0 && first <= 0xEF) {
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sequence_length = 3;
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} else if (first >= 0xF0 && first <= 0xF4) {
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sequence_length = 4;
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} else {
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break;
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}
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if (offset + sequence_length > max_bytes) break;
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bool complete = true;
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for (size_t i = 1; i < sequence_length; i++) {
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if (text[offset + i] == '\0' || !isUtf8Continuation(static_cast<uint8_t>(text[offset + i]))) {
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complete = false;
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break;
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}
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}
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if (!complete) break;
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if (sequence_length == 3) {
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const uint8_t second = static_cast<uint8_t>(text[offset + 1]);
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if ((first == 0xE0 && second < 0xA0) || (first == 0xED && second > 0x9F)) break;
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} else if (sequence_length == 4) {
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const uint8_t second = static_cast<uint8_t>(text[offset + 1]);
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if ((first == 0xF0 && second < 0x90) || (first == 0xF4 && second > 0x8F)) break;
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}
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offset += sequence_length;
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}
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return offset;
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}
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} // namespace mesh
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