[feat] implement file transfer module

src/tools/file_transfer.cpp

@@ -0,0 +1,286 @@
+#include "file_transfer.h"
+
+#include <atomic>
+#include <chrono>
+
+#include "rd_log.h"
+
+namespace crossdesk {
+
+namespace {
+std::atomic<uint32_t> g_next_file_id{1};
+constexpr uint32_t kFileChunkMagic = 0x4A4E544D;  // 'JNTM'
+}  // namespace
+
+uint32_t FileSender::NextFileId() { return g_next_file_id.fetch_add(1); }
+
+int FileSender::SendFile(const std::filesystem::path& path,
+                         const std::string& label, const SendFunc& send,
+                         std::size_t chunk_size) {
+  if (!send) {
+    LOG_ERROR("FileSender::SendFile: send function is empty");
+    return -1;
+  }
+
+  std::error_code ec;
+  if (!std::filesystem::exists(path, ec) ||
+      !std::filesystem::is_regular_file(path, ec)) {
+    LOG_ERROR("FileSender::SendFile: file [{}] not found or not regular",
+              path.string().c_str());
+    return -1;
+  }
+
+  uint64_t total_size = std::filesystem::file_size(path, ec);
+  if (ec) {
+    LOG_ERROR("FileSender::SendFile: failed to get size of [{}]: {}",
+              path.string().c_str(), ec.message().c_str());
+    return -1;
+  }
+
+  std::ifstream ifs(path, std::ios::binary);
+  if (!ifs.is_open()) {
+    LOG_ERROR("FileSender::SendFile: failed to open [{}]",
+              path.string().c_str());
+    return -1;
+  }
+
+  const uint32_t file_id = NextFileId();
+  uint64_t offset = 0;
+  bool is_first = true;
+  std::string file_name = label.empty() ? path.filename().string() : label;
+
+  std::vector<char> buffer;
+  buffer.resize(chunk_size);
+
+  while (ifs && offset < total_size) {
+    uint64_t remaining = total_size - offset;
+    uint32_t to_read =
+        static_cast<uint32_t>(std::min<uint64_t>(remaining, chunk_size));
+
+    ifs.read(buffer.data(), static_cast<std::streamsize>(to_read));
+    std::streamsize bytes_read = ifs.gcount();
+    if (bytes_read <= 0) {
+      break;
+    }
+
+    bool is_last = (offset + static_cast<uint64_t>(bytes_read) >= total_size);
+    const std::string* name_ptr = is_first ? &file_name : nullptr;
+
+    std::vector<char> chunk = BuildChunk(
+        file_id, offset, total_size, buffer.data(),
+        static_cast<uint32_t>(bytes_read), name_ptr, is_first, is_last);
+
+    int ret = send(chunk.data(), chunk.size());
+    if (ret != 0) {
+      LOG_ERROR("FileSender::SendFile: send failed for [{}], ret={}",
+                path.string().c_str(), ret);
+      return ret;
+    }
+
+    offset += static_cast<uint64_t>(bytes_read);
+    is_first = false;
+  }
+
+  return 0;
+}
+
+std::vector<char> FileSender::BuildChunk(uint32_t file_id, uint64_t offset,
+                                         uint64_t total_size, const char* data,
+                                         uint32_t data_size,
+                                         const std::string* file_name,
+                                         bool is_first, bool is_last) {
+  FileChunkHeader header{};
+  header.magic = kFileChunkMagic;
+  header.file_id = file_id;
+  header.offset = offset;
+  header.total_size = total_size;
+  header.chunk_size = data_size;
+  header.name_len =
+      (file_name && is_first) ? static_cast<uint16_t>(file_name->size()) : 0;
+  header.flags = 0;
+  if (is_first) header.flags |= 0x01;
+  if (is_last) header.flags |= 0x02;
+
+  std::size_t total_size_bytes =
+      sizeof(FileChunkHeader) + header.name_len + header.chunk_size;
+
+  std::vector<char> buffer;
+  buffer.resize(total_size_bytes);
+
+  std::size_t offset_bytes = 0;
+  memcpy(buffer.data() + offset_bytes, &header, sizeof(FileChunkHeader));
+  offset_bytes += sizeof(FileChunkHeader);
+
+  if (header.name_len > 0 && file_name) {
+    memcpy(buffer.data() + offset_bytes, file_name->data(), header.name_len);
+    offset_bytes += header.name_len;
+  }
+
+  if (header.chunk_size > 0 && data) {
+    memcpy(buffer.data() + offset_bytes, data, header.chunk_size);
+  }
+
+  return buffer;
+}
+
+// ---------- FileReceiver ----------
+
+FileReceiver::FileReceiver() : output_dir_(GetDefaultDesktopPath()) {}
+
+FileReceiver::FileReceiver(const std::filesystem::path& output_dir)
+    : output_dir_(output_dir) {
+  std::error_code ec;
+  if (!output_dir_.empty()) {
+    std::filesystem::create_directories(output_dir_, ec);
+    if (ec) {
+      LOG_ERROR("FileReceiver: failed to create output dir [{}]: {}",
+                output_dir_.string().c_str(), ec.message().c_str());
+    }
+  }
+}
+
+std::filesystem::path FileReceiver::GetDefaultDesktopPath() {
+#ifdef _WIN32
+  const char* home_env = std::getenv("USERPROFILE");
+#else
+  const char* home_env = std::getenv("HOME");
+#endif
+  if (!home_env) {
+    return std::filesystem::path{};
+  }
+
+  std::filesystem::path desktop_path =
+      std::filesystem::path(home_env) / "Desktop";
+
+  std::error_code ec;
+  std::filesystem::create_directories(desktop_path, ec);
+  if (ec) {
+    LOG_ERROR("FileReceiver: failed to create desktop directory [{}]: {}",
+              desktop_path.string().c_str(), ec.message().c_str());
+  }
+
+  return desktop_path;
+}
+
+bool FileReceiver::OnData(const char* data, size_t size) {
+  if (!data || size < sizeof(FileChunkHeader)) {
+    LOG_ERROR("FileReceiver::OnData: invalid buffer");
+    return false;
+  }
+
+  FileChunkHeader header{};
+  memcpy(&header, data, sizeof(FileChunkHeader));
+
+  if (header.magic != kFileChunkMagic) {
+    return false;
+  }
+
+  std::size_t header_and_name =
+      sizeof(FileChunkHeader) + static_cast<std::size_t>(header.name_len);
+  if (size < header_and_name ||
+      size < header_and_name + static_cast<std::size_t>(header.chunk_size)) {
+    LOG_ERROR("FileReceiver::OnData: buffer too small for header + payload");
+    return false;
+  }
+
+  const char* name_ptr = data + sizeof(FileChunkHeader);
+  std::string file_name;
+  const std::string* file_name_ptr = nullptr;
+  if (header.name_len > 0) {
+    file_name.assign(name_ptr,
+                     name_ptr + static_cast<std::size_t>(header.name_len));
+    file_name_ptr = &file_name;
+  }
+
+  const char* payload = data + header_and_name;
+  std::size_t payload_size =
+      static_cast<std::size_t>(header.chunk_size);  // may be 0
+
+  return HandleChunk(header, payload, payload_size, file_name_ptr);
+}
+
+bool FileReceiver::HandleChunk(const FileChunkHeader& header,
+                               const char* payload, size_t payload_size,
+                               const std::string* file_name) {
+  auto it = contexts_.find(header.file_id);
+  if (it == contexts_.end()) {
+    // new file context must start with first chunk.
+    if ((header.flags & 0x01) == 0) {
+      LOG_ERROR("FileReceiver: received non-first chunk for unknown file_id={}",
+                header.file_id);
+      return false;
+    }
+
+    FileContext ctx;
+    ctx.total_size = header.total_size;
+
+    std::string filename;
+    if (file_name && !file_name->empty()) {
+      filename = *file_name;
+    } else {
+      filename = "received_" + std::to_string(header.file_id);
+    }
+
+    ctx.file_name = filename;
+
+    std::filesystem::path save_path = output_dir_.empty()
+                                          ? std::filesystem::path(filename)
+                                          : output_dir_ / filename;
+
+    // if file exists, append timestamp.
+    std::error_code ec;
+    if (std::filesystem::exists(save_path, ec)) {
+      auto now = std::chrono::system_clock::now();
+      auto ts = std::chrono::duration_cast<std::chrono::milliseconds>(
+                    now.time_since_epoch())
+                    .count();
+      save_path = save_path.parent_path() /
+                  (save_path.stem().string() + "_" + std::to_string(ts) +
+                   save_path.extension().string());
+    }
+
+    ctx.ofs.open(save_path, std::ios::binary | std::ios::trunc);
+    if (!ctx.ofs.is_open()) {
+      LOG_ERROR("FileReceiver: failed to open [{}] for writing",
+                save_path.string().c_str());
+      return false;
+    }
+
+    contexts_.emplace(header.file_id, std::move(ctx));
+    it = contexts_.find(header.file_id);
+  }
+
+  FileContext& ctx = it->second;
+
+  if (payload_size > 0 && payload) {
+    ctx.ofs.seekp(static_cast<std::streamoff>(header.offset), std::ios::beg);
+    ctx.ofs.write(payload, static_cast<std::streamsize>(payload_size));
+    if (!ctx.ofs.good()) {
+      LOG_ERROR("FileReceiver: write failed for file_id={}", header.file_id);
+      return false;
+    }
+    ctx.received += static_cast<uint64_t>(payload_size);
+  }
+
+  bool is_last = (header.flags & 0x02) != 0;
+  if (is_last || ctx.received >= ctx.total_size) {
+    ctx.ofs.close();
+
+    std::filesystem::path saved_path =
+        output_dir_.empty() ? std::filesystem::path(ctx.file_name)
+                            : output_dir_ / ctx.file_name;
+
+    LOG_INFO("FileReceiver: file received complete, file_id={}, size={}",
+             header.file_id, ctx.received);
+
+    if (on_file_complete_) {
+      on_file_complete_(saved_path);
+    }
+
+    contexts_.erase(header.file_id);
+  }
+
+  return true;
+}
+
+}  // namespace crossdesk

src/tools/file_transfer.h

@@ -0,0 +1,99 @@
+/*
+ * @Author: DI JUNKUN
+ * @Date: 2025-12-18
+ * Copyright (c) 2025 by DI JUNKUN, All Rights Reserved.
+ */
+
+#ifndef _FILE_TRANSFER_H_
+#define _FILE_TRANSFER_H_
+
+#include <cstdint>
+#include <filesystem>
+#include <fstream>
+#include <functional>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+namespace crossdesk {
+
+#pragma pack(push, 1)
+struct FileChunkHeader {
+  uint32_t magic;       // magic to identify file-transfer chunks
+  uint32_t file_id;     // unique id per file transfer
+  uint64_t offset;      // offset in file
+  uint64_t total_size;  // total file size
+  uint32_t chunk_size;  // payload size in this chunk
+  uint16_t name_len;    // filename length (bytes), only set on first chunk
+  uint8_t flags;        // bit0: is_first, bit1: is_last, others reserved
+};
+#pragma pack(pop)
+
+class FileSender {
+ public:
+  using SendFunc = std::function<int(const char* data, size_t size)>;
+
+ public:
+  FileSender() = default;
+
+  // generate a new file id
+  static uint32_t NextFileId();
+
+  // synchronously send a file using the provided send function.
+  // `path`  : full path to the local file.
+  // `label` : logical filename to send (usually path.filename()).
+  // `send`  : callback that pushes one encoded chunk into the data channel.
+  // Return 0 on success, <0 on error.
+  int SendFile(const std::filesystem::path& path, const std::string& label,
+               const SendFunc& send, std::size_t chunk_size = 64 * 1024);
+
+  // build a single encoded chunk buffer according to FileChunkHeader protocol.
+  static std::vector<char> BuildChunk(uint32_t file_id, uint64_t offset,
+                                      uint64_t total_size, const char* data,
+                                      uint32_t data_size,
+                                      const std::string* file_name,
+                                      bool is_first, bool is_last);
+};
+
+class FileReceiver {
+ public:
+  struct FileContext {
+    std::string file_name;
+    uint64_t total_size = 0;
+    uint64_t received = 0;
+    std::ofstream ofs;
+  };
+
+  using OnFileComplete =
+      std::function<void(const std::filesystem::path& saved_path)>;
+
+ public:
+  // save to default desktop directory.
+  FileReceiver();
+
+  // save to a specified directory.
+  explicit FileReceiver(const std::filesystem::path& output_dir);
+
+  // process one received data buffer (one chunk).
+  // return true if parsed and processed successfully, false otherwise.
+  bool OnData(const char* data, size_t size);
+
+  void SetOnFileComplete(OnFileComplete cb) { on_file_complete_ = cb; }
+
+  const std::filesystem::path& OutputDir() const { return output_dir_; }
+
+ private:
+  static std::filesystem::path GetDefaultDesktopPath();
+
+  bool HandleChunk(const FileChunkHeader& header, const char* payload,
+                   size_t payload_size, const std::string* file_name);
+
+ private:
+  std::filesystem::path output_dir_;
+  std::unordered_map<uint32_t, FileContext> contexts_;
+  OnFileComplete on_file_complete_ = nullptr;
+};
+
+}  // namespace crossdesk
+
+#endif