[refactor] reorganize platform and wire sources

libs/wire/src/file_transfer.cpp

@@ -0,0 +1,81 @@
+#include <file_transfer_format.h>
+
+#include <cstring>
+#include <limits>
+
+namespace crossdesk {
+
+std::vector<char> EncodeFileChunk(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) {
+  const std::size_t name_size = file_name && is_first ? file_name->size() : 0;
+  if (name_size > std::numeric_limits<uint16_t>::max() ||
+      offset > total_size || data_size > total_size - offset ||
+      (data_size > 0 && data == nullptr)) {
+    return {};
+  }
+
+  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 = static_cast<uint16_t>(name_size);
+  header.flags = (is_first ? 0x01 : 0) | (is_last ? 0x02 : 0);
+
+  std::vector<char> output(sizeof(header) + name_size + data_size);
+  std::memcpy(output.data(), &header, sizeof(header));
+  std::size_t cursor = sizeof(header);
+  if (name_size > 0) {
+    std::memcpy(output.data() + cursor, file_name->data(), name_size);
+    cursor += name_size;
+  }
+  if (data_size > 0) {
+    std::memcpy(output.data() + cursor, data, data_size);
+  }
+  return output;
+}
+
+bool DecodeFileChunk(const char* data, std::size_t size,
+                     FileChunkView* output) {
+  if (!data || !output || size < sizeof(FileChunkHeader)) return false;
+
+  FileChunkHeader header{};
+  std::memcpy(&header, data, sizeof(header));
+  if (header.magic != kFileChunkMagic) return false;
+
+  const std::size_t name_size = header.name_len;
+  const std::size_t payload_size = header.chunk_size;
+  if (name_size > size - sizeof(header)) return false;
+  const std::size_t payload_offset = sizeof(header) + name_size;
+  if (payload_size > size - payload_offset || header.offset > header.total_size ||
+      payload_size > header.total_size - header.offset) {
+    return false;
+  }
+
+  output->header = header;
+  output->file_name.assign(data + sizeof(header), name_size);
+  output->payload = data + payload_offset;
+  output->payload_size = payload_size;
+  return true;
+}
+
+std::array<char, sizeof(FileTransferAck)> EncodeFileTransferAck(
+    const FileTransferAck& ack) {
+  std::array<char, sizeof(FileTransferAck)> output{};
+  std::memcpy(output.data(), &ack, sizeof(ack));
+  return output;
+}
+
+bool DecodeFileTransferAck(const char* data, std::size_t size,
+                           FileTransferAck* output) {
+  if (!data || !output || size != sizeof(FileTransferAck)) return false;
+  std::memcpy(output, data, sizeof(*output));
+  return output->magic == kFileAckMagic &&
+         output->acked_offset <= output->total_size;
+}
+
+}  // namespace crossdesk