添加文本转换器代码

others/C++/text converter/src/Ascii85Converter.cpp

@@ -0,0 +1,47 @@
+#include "../include/Ascii85Converter.hpp"
+#include <string>
+#include <cmath>
+#include <sstream>
+#include <cstdint>
+
+const std::string ASCII85_PREFIX = "<~";
+const std::string ASCII85_SUFFIX = "~>";
+
+std::string Ascii85Converter::convert(const std::string& input) {
+    std::stringstream result;
+    result << ASCII85_PREFIX;
+
+    size_t i = 0;
+    while (i < input.size()) {
+        uint32_t value = 0;
+        int bytes = 0;
+
+        // 读取4个字节
+        for (int j = 0; j < 4 && (i + j) < input.size(); j++) {
+            value = (value << 8) | static_cast<unsigned char>(input[i + j]);
+            bytes++;
+        }
+        i += bytes;
+
+        // 特殊处理全0的4字节
+        if (value == 0 && bytes == 4) {
+            result << 'z';
+            continue;
+        }
+
+        // 转换为Ascii85
+        char chars[5];
+        for (int j = 4; j >= 0; j--) {
+            chars[j] = value % 85 + '!';
+            value /= 85;
+        }
+
+        // 写入结果(只写入bytes+1个字符)
+        for (int j = 0; j < bytes + 1; j++) {
+            result << chars[j];
+        }
+    }
+
+    result << ASCII85_SUFFIX;
+    return result.str();
+}