#include <string>
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#include <vector>
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#include <sstream>
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#include <cctype>
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#include <cstdio>
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#include <algorithm>
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// 辅助函数：修剪字符串两端的空白
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std::string trim(const std::string& s) {
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auto start = s.find_first_not_of(" \t");
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if (start == std::string::npos) return "";
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auto end = s.find_last_not_of(" \t");
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return s.substr(start, end - start + 1);
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}
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// 辅助函数：检查字符串是否以某个前缀开头
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bool starts_with(const std::string& s, const std::string& prefix) {
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return s.size() >= prefix.size() &&
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s.compare(0, prefix.size(), prefix) == 0;
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}
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// 辅助函数：分割字符串
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std::vector<std::string> split(const std::string& s, char delimiter) {
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std::vector<std::string> tokens;
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std::string token;
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std::istringstream token_stream(s);
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while (std::getline(token_stream, token, delimiter)) {
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if (!token.empty()) {
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tokens.push_back(token);
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}
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}
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return tokens;
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}
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// URL 解码（简易实现）
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std::string url_decode(const std::string& str) {
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std::string result;
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for (size_t i = 0; i < str.size(); ++i) {
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if (str[i] == '%' && i + 2 < str.size()) {
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int hex_val;
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if (sscanf(str.substr(i + 1, 2).c_str(), "%x", &hex_val) == 1) {
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result += static_cast<char>(hex_val);
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i += 2;
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} else {
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result += str[i];
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}
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} else if (str[i] == '+') {
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result += ' ';
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} else {
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result += str[i];
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}
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}
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return result;
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}
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// 解析 RFC 5987 编码（如 filename*=UTF-8''%C2%A3.txt）
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std::string decode_rfc5987(const std::string& value) {
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size_t pos = value.find("''");
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if (pos != std::string::npos) {
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std::string encoded = value.substr(pos + 2);
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return url_decode(encoded);
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}
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return value;
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}
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// 主解析函数
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std::string parse_attachment_filename_impl(const std::string& content_disp) {
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std::vector<std::string> parts = split(content_disp, ';');
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std::string filename;
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for (auto& part : parts) {
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std::string trimmed = trim(part);
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// 优先处理 RFC 5987 编码的 filename*
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if (starts_with(trimmed, "filename*=")) {
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std::string value = trimmed.substr(10);
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if (value.size() >= 2 && value.front() == '"' && value.back() == '"') {
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value = value.substr(1, value.size() - 2);
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}
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return decode_rfc5987(value);
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}
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// 其次处理普通 filename
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else if (starts_with(trimmed, "filename=")) {
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std::string value = trimmed.substr(9);
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if (value.size() >= 2 && value.front() == '"' && value.back() == '"') {
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value = value.substr(1, value.size() - 2);
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}
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filename = value;
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}
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}
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return filename;
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}
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