Use copy_from instead of memcoy if possible.

GitOrigin-RevId: 63981da8864d16ce46bca4b9580e7d9613c837c5

td/mtproto/HttpTransport.cpp

@@ -17,7 +17,6 @@
 
 // TODO: do I need \r\n as delimiter?
 
-#include <cstring>
 #include <tuple>
 
 namespace td {
@@ -73,8 +72,7 @@ void Transport::write(BufferWriter &&message, bool quick_ack) {
   Slice src = r_head.ok();
   // LOG(DEBUG) << src;
   MutableSlice dst = message.prepare_prepend();
-  LOG_CHECK(dst.size() >= src.size()) << dst.size() << " >= " << src.size();
-  std::memcpy(dst.end() - src.size(), src.begin(), src.size());
+  dst.substr(dst.size() - src.size()).copy_from(src);
   message.confirm_prepend(src.size());
   output_->append(message.as_buffer_slice());
   turn_ = Read;

td/mtproto/crypto.cpp

@@ -23,8 +23,6 @@
 #include <openssl/pem.h>
 #include <openssl/rsa.h>
 
-#include <cstring>
-
 namespace td {
 
 /*** RSA ***/
@@ -113,8 +111,7 @@ size_t RSA::encrypt(unsigned char *from, size_t from_len, unsigned char *to) con
   while (chunks-- > 0) {
     BigNum x = BigNum::from_binary(Slice(from, 255));
     BigNum::mod_exp(y, x, e_, n_, ctx);
-    string result = y.to_binary(256);
-    std::memcpy(to, result.c_str(), 256);
+    MutableSlice(to, 256).copy_from(y.to_binary(256));
     to += 256;
   }
   return chunks * 256;
@@ -126,8 +123,7 @@ void RSA::decrypt(Slice from, MutableSlice to) const {
   BigNum x = BigNum::from_binary(from);
   BigNum y;
   BigNum::mod_exp(y, x, e_, n_, ctx);
-  string result = y.to_binary(256);
-  std::memcpy(to.data(), result.c_str(), 256);
+  to.copy_from(y.to_binary(256));
 }
 
 }  // namespace td

tdutils/td/utils/BufferedReader.h

@@ -11,8 +11,6 @@
 #include "td/utils/Slice.h"
 #include "td/utils/Status.h"
 
-#include <cstring>
-
 namespace td {
 
 class BufferedReader {
@@ -34,13 +32,13 @@ inline Result<size_t> BufferedReader::read(MutableSlice slice) {
   size_t available = end_pos_ - begin_pos_;
   if (available >= slice.size()) {
     // have enough data in buffer
-    std::memcpy(slice.begin(), &buff_[begin_pos_], slice.size());
+    slice.copy_from({&buff_[begin_pos_], slice.size()});
     begin_pos_ += slice.size();
     return slice.size();
   }
 
   if (available) {
-    std::memcpy(slice.begin(), &buff_[begin_pos_], available);
+    slice.copy_from({&buff_[begin_pos_], available});
     begin_pos_ += available;
     slice.remove_prefix(available);
   }
@@ -55,8 +53,8 @@ inline Result<size_t> BufferedReader::read(MutableSlice slice) {
   end_pos_ = result;
 
   size_t left = min(end_pos_, slice.size());
-  std::memcpy(slice.begin(), &buff_[begin_pos_], left);
-  begin_pos_ += left;
+  slice.copy_from({&buff_[0], left});
+  begin_pos_ = left;
   return left + available;
 }
 

tdutils/td/utils/buffer.h

@@ -13,7 +13,6 @@
 #include "td/utils/Slice.h"
 
 #include <atomic>
-#include <cstring>
 #include <limits>
 #include <memory>
 
@@ -120,7 +119,7 @@ class BufferSlice {
   }
 
   explicit BufferSlice(Slice slice) : BufferSlice(slice.size()) {
-    std::memcpy(as_slice().begin(), slice.begin(), slice.size());
+    as_slice().copy_from(slice);
   }
 
   BufferSlice(const char *ptr, size_t size) : BufferSlice(Slice(ptr, size)) {
@@ -510,7 +509,7 @@ class ChainBufferIterator {
       // copy to dest if possible
       auto to_dest_size = min(ready.size(), dest.size());
       if (to_dest_size != 0) {
-        std::memcpy(dest.data(), ready.data(), to_dest_size);
+        dest.copy_from(ready.substr(0, to_dest_size));
         dest.remove_prefix(to_dest_size);
       }
 
@@ -691,7 +690,7 @@ class ChainBufferWriter {
     while (!slice.empty()) {
       auto ready = prepare_append(td::max(slice.size(), hint));
       auto shift = min(ready.size(), slice.size());
-      std::memcpy(ready.data(), slice.data(), shift);
+      ready.copy_from(slice.substr(0, shift));
       confirm_append(shift);
       slice.remove_prefix(shift);
     }

tdutils/td/utils/crypto.cpp

@@ -6,6 +6,7 @@
 //
 #include "td/utils/crypto.h"
 
+#include "td/utils/as.h"
 #include "td/utils/BigNum.h"
 #include "td/utils/logging.h"
 #include "td/utils/misc.h"
@@ -35,7 +36,6 @@
 #endif
 
 #include <algorithm>
-#include <cstring>
 #include <mutex>
 #include <utility>
 
@@ -143,20 +143,16 @@ void init_crypto() {
 
 template <class FromT>
 static string as_big_endian_string(const FromT &from) {
-  size_t size = sizeof(from);
-  string res(size, '\0');
+  char res[sizeof(FromT)];
+  as<FromT>(res) = from;
 
-  auto ptr = reinterpret_cast<const unsigned char *>(&from);
-  std::memcpy(&res[0], ptr, size);
-
-  size_t i = size;
+  size_t i = sizeof(FromT);
   while (i && res[i - 1] == 0) {
     i--;
   }
 
-  res.resize(i);
-  std::reverse(res.begin(), res.end());
-  return res;
+  std::reverse(res, res + i);
+  return string(res, res + i);
 }
 
 static int pq_factorize_big(Slice pq_str, string *p_str, string *q_str) {