Use string_view::substr when making string_views out of other strings

substr is both more convenient and also slightly safer when C++ hardening is enabled.

PiperOrigin-RevId: 697644082

quiche/http2/adapter/oghttp2_session.cc

diff --git a/quiche/http2/adapter/oghttp2_session.cc b/quiche/http2/adapter/oghttp2_session.cc
index 6d9bb13..7c4fabf 100644
--- a/quiche/http2/adapter/oghttp2_session.cc
+++ b/quiche/http2/adapter/oghttp2_session.cc
@@ -778,8 +778,7 @@
       }
       if (static_cast<size_t>(result) < frame.size()) {
         // The frame was partially written, so the rest must be buffered.
-        buffered_data_.Append(
-            absl::string_view(frame.data() + result, frame.size() - result));
+        buffered_data_.Append(absl::string_view(frame).substr(result));
         return SendResult::SEND_BLOCKED;
       }
     }

quiche/quic/core/crypto/crypto_secret_boxer.cc

diff --git a/quiche/quic/core/crypto/crypto_secret_boxer.cc b/quiche/quic/core/crypto/crypto_secret_boxer.cc
index e133a7f..bdc87e0 100644
--- a/quiche/quic/core/crypto/crypto_secret_boxer.cc
+++ b/quiche/quic/core/crypto/crypto_secret_boxer.cc
@@ -129,14 +129,12 @@
     absl::ReaderMutexLock l(&lock_);
     for (const bssl::UniquePtr<EVP_AEAD_CTX>& ctx : state_->ctxs) {
       size_t bytes_written;
-      if (EVP_AEAD_CTX_open(ctx.get(),
-                            reinterpret_cast<uint8_t*>(
-                                const_cast<char*>(out_storage->data())),
-                            &bytes_written, ciphertext_len, nonce,
-                            kSIVNonceSize, ciphertext, ciphertext_len, nullptr,
-                            0)) {
+      if (EVP_AEAD_CTX_open(
+              ctx.get(), reinterpret_cast<uint8_t*>(out_storage->data()),
+              &bytes_written, ciphertext_len, nonce, kSIVNonceSize, ciphertext,
+              ciphertext_len, nullptr, 0)) {
         ok = true;
-        *out = absl::string_view(out_storage->data(), bytes_written);
+        *out = absl::string_view(*out_storage).substr(0, bytes_written);
         break;
       }
 

quiche/quic/tools/quic_memory_cache_backend.cc

diff --git a/quiche/quic/tools/quic_memory_cache_backend.cc b/quiche/quic/tools/quic_memory_cache_backend.cc
index 5290636..1f64bf6 100644
--- a/quiche/quic/tools/quic_memory_cache_backend.cc
+++ b/quiche/quic/tools/quic_memory_cache_backend.cc
@@ -40,7 +40,7 @@
                      << file_name_;
     return;
   }
-  file_contents_ = *maybe_file_contents;
+  file_contents_ = *std::move(maybe_file_contents);
 
   // First read the headers.
   for (size_t start = 0; start < file_contents_.length();) {
@@ -54,12 +54,11 @@
     if (file_contents_[pos - 1] == '\r') {
       len -= 1;
     }
-    absl::string_view line(file_contents_.data() + start, len);
+    auto line = absl::string_view(file_contents_).substr(start, len);
     start = pos + 1;
     // Headers end with an empty line.
     if (line.empty()) {
-      body_ = absl::string_view(file_contents_.data() + start,
-                                file_contents_.size() - start);
+      body_ = absl::string_view(file_contents_).substr(start);
       break;
     }
     // Extract the status from the HTTP first line.
@@ -137,8 +136,7 @@
   if (it == responses_.end()) {
     uint64_t ignored = 0;
     if (generate_bytes_response_) {
-      if (absl::SimpleAtoi(absl::string_view(path.data() + 1, path.size() - 1),
-                           &ignored)) {
+      if (absl::SimpleAtoi(path.substr(1), &ignored)) {
         // The actual parsed length is ignored here and will be recomputed
         // by the caller.
         return generate_bytes_response_.get();