Improve Slice::truncate usage.

td/mtproto/ProxySecret.h

@@ -32,9 +32,9 @@ class ProxySecret {
   }
 
   Slice get_proxy_secret() const {
-    auto proxy_secret = Slice(secret_).truncate(17);
+    Slice proxy_secret(secret_);
-    if (proxy_secret.size() == 17) {
+    if (proxy_secret.size() >= 17) {
-      proxy_secret.remove_prefix(1);
+      return proxy_secret.substr(1, 16);
     }
     return proxy_secret;
   }

td/mtproto/TcpTransport.cpp

@@ -63,7 +63,7 @@ void IntermediateTransport::write_prepare_inplace(BufferWriter *message, bool qu
   size_t append_size = 0;
   if (with_padding()) {
     append_size = Random::secure_uint32() % 16;
-    MutableSlice append = message->prepare_append().truncate(append_size);
+    MutableSlice append = message->prepare_append().substr(0, append_size);
     CHECK(append.size() == append_size);
     Random::secure_bytes(append);
     message->confirm_append(append.size());

td/mtproto/Transport.cpp

@@ -226,7 +226,7 @@ Status Transport::read_crypto_impl(int X, MutableSlice message, const AuthKey &a
   auto *header = reinterpret_cast<HeaderT *>(message.begin());
   *header_ptr = header;
   auto to_decrypt = MutableSlice(header->encrypt_begin(), message.uend());
-  to_decrypt = to_decrypt.truncate(to_decrypt.size() & ~15);
+  to_decrypt.truncate(to_decrypt.size() & ~15);
   if (to_decrypt.size() % 16 != 0) {
     return Status::Error(PSLICE() << "Invalid mtproto message: size of encrypted part is not multiple of 16 [size = "
                                   << to_decrypt.size() << "]");

td/telegram/SecretChatActor.cpp

@@ -2041,7 +2041,7 @@ void SecretChatActor::calc_key_hash() {
   auto sha256_slice = MutableSlice(sha256_buf, 32);
   sha256(pfs_state_.auth_key.key(), sha256_slice);
 
-  auth_state_.key_hash = sha1_slice.truncate(16).str() + sha256_slice.truncate(20).str();
+  auth_state_.key_hash = PSTRING() << sha1_slice.substr(0, 16) << sha256_slice.substr(0, 20);
 }
 
 void SecretChatActor::send_update_secret_chat() {

td/telegram/files/FileDownloader.cpp

@@ -367,7 +367,7 @@ Result<size_t> FileDownloader::process_part(Part part, NetQueryPtr net_query) {
                     bytes.as_slice());
   }
 
-  auto slice = bytes.as_slice().truncate(part.size);
+  auto slice = bytes.as_slice().substr(0, part.size);
   TRY_STATUS(acquire_fd());
   LOG(INFO) << "Got " << slice.size() << " bytes at offset " << part.offset << " for \"" << path_ << '"';
   TRY_RESULT(written, fd_.pwrite(slice, part.offset));

tddb/td/db/binlog/BinlogEvent.cpp

@@ -28,8 +28,7 @@ Status BinlogEvent::init(BufferSlice &&raw_event, bool check_crc) {
   data_ = MutableSlice(const_cast<char *>(slice_data.begin()), slice_data.size());
   crc32_ = static_cast<uint32>(parser.fetch_int());
   if (check_crc) {
-    CHECK(size_ >= TAIL_SIZE);
+    auto calculated_crc = crc32(raw_event.as_slice().substr(0, size_ - TAIL_SIZE));
-    auto calculated_crc = crc32(raw_event.as_slice().truncate(size_ - TAIL_SIZE));
     if (calculated_crc != crc32_) {
       return Status::Error(PSLICE() << "crc mismatch " << tag("actual", format::as_hex(calculated_crc))
                                     << tag("expected", format::as_hex(crc32_)) << public_to_string());
@@ -44,7 +43,7 @@ Status BinlogEvent::validate() const {
   if (raw_event_.size() < 4) {
     return Status::Error("Too small event");
   }
-  uint32 size = TlParser(raw_event_.as_slice().truncate(4)).fetch_int();
+  uint32 size = TlParser(raw_event_.as_slice().substr(0, 4)).fetch_int();
   if (size_ != size) {
     return Status::Error(PSLICE() << "Size of event changed: " << tag("was", size_) << tag("now", size));
   }

tdutils/td/utils/BufferedFd.h

@@ -101,7 +101,8 @@ Result<size_t> BufferedFdBase<FdT>::flush_read(size_t max_read) {
   CHECK(read_);
   size_t result = 0;
   while (::td::can_read_local(*this) && max_read) {
-    MutableSlice slice = read_->prepare_append().truncate(max_read);
+    MutableSlice slice = read_->prepare_append();
+    slice.truncate(max_read);
     TRY_RESULT(x, FdT::read(slice));
     slice.truncate(x);
     read_->confirm_append(x);

tdutils/td/utils/BufferedUdp.h

@@ -36,7 +36,7 @@ class UdpWriter {
     }
 
     size_t cnt;
-    auto status = fd.send_messages(::td::Span<UdpSocketFd::OutboundMessage>(messages).truncate(to_send_n), cnt);
+    auto status = fd.send_messages(Span<UdpSocketFd::OutboundMessage>(messages).truncate(to_send_n), cnt);
     queue.pop_n(cnt);
     return status;
   }
@@ -51,7 +51,7 @@ class UdpReaderHelper {
       buffer_ = BufferSlice(RESERVED_SIZE);
     }
     CHECK(buffer_.size() >= MAX_PACKET_SIZE);
-    message.data = buffer_.as_slice().truncate(MAX_PACKET_SIZE);
+    message.data = buffer_.as_slice().substr(0, MAX_PACKET_SIZE);
   }
 
   UdpMessage extract_udp_message(UdpSocketFd::InboundMessage &message) {

tdutils/td/utils/port/StdStreams.cpp

@@ -201,7 +201,8 @@ class BufferedStdinImpl {
     size_t result = 0;
     ::td::sync_with_poll(*this);
     while (::td::can_read_local(*this) && max_read) {
-      MutableSlice slice = writer_.prepare_append().truncate(max_read);
+      MutableSlice slice = writer_.prepare_append();
+      slice.truncate(max_read);
       TRY_RESULT(x, file_fd_.read(slice));
       slice.truncate(x);
       writer_.confirm_append(x);