feat(render): add base64 encode/decode helpers

render/Base64.cpp

@@ -0,0 +1,55 @@
+#include "Base64.h"
+
+namespace vf {
+
+std::string base64Encode(const std::vector<uint8_t>& bytes) {
+    static const char* table =
+        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+    std::string out;
+    out.reserve((bytes.size() + 2) / 3 * 4);
+    std::size_t i = 0;
+    for (; i + 2 < bytes.size(); i += 3) {
+        uint32_t n = (bytes[i] << 16) | (bytes[i + 1] << 8) | bytes[i + 2];
+        out.push_back(table[(n >> 18) & 63]);
+        out.push_back(table[(n >> 12) & 63]);
+        out.push_back(table[(n >> 6) & 63]);
+        out.push_back(table[n & 63]);
+    }
+    if (i < bytes.size()) {
+        uint32_t n = bytes[i] << 16;
+        bool two = (i + 1 < bytes.size());
+        if (two) n |= bytes[i + 1] << 8;
+        out.push_back(table[(n >> 18) & 63]);
+        out.push_back(table[(n >> 12) & 63]);
+        out.push_back(two ? table[(n >> 6) & 63] : '=');
+        out.push_back('=');
+    }
+    return out;
+}
+
+std::vector<uint8_t> base64Decode(const std::string& text) {
+    auto value = [](char c) -> int {
+        if (c >= 'A' && c <= 'Z') return c - 'A';
+        if (c >= 'a' && c <= 'z') return c - 'a' + 26;
+        if (c >= '0' && c <= '9') return c - '0' + 52;
+        if (c == '+') return 62;
+        if (c == '/') return 63;
+        return -1;
+    };
+    std::vector<uint8_t> out;
+    int buffer = 0, bits = 0;
+    for (char c : text) {
+        if (c == '=') break;
+        int v = value(c);
+        if (v < 0) continue;
+        buffer = (buffer << 6) | v;
+        bits += 6;
+        if (bits >= 8) {
+            bits -= 8;
+            out.push_back(static_cast<uint8_t>((buffer >> bits) & 0xff));
+        }
+    }
+    return out;
+}
+
+} // namespace vf

render/Base64.h

@@ -0,0 +1,12 @@
+#pragma once
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+namespace vf {
+
+std::string base64Encode(const std::vector<uint8_t>& bytes);
+std::vector<uint8_t> base64Decode(const std::string& text);
+
+} // namespace vf