let Cursor::peek return span

Summary:
Currently, `CursorBase::peek()` returns `pair<uint8_t const*, size_t>` and `CursorBase::peekView()` returns `basic_string_view<uint8_t>`. Consolidate them into `CursorBase::peek()` returning `span<uint8_t const>`.

As one motivation, libc++ v19 removes `basic_string_view<uint8_t>`.

Reviewed By: thevinster

Differential Revision: D62460851

fbshipit-source-id: 72d567817faf778287594c10dfd7f6f379bf2446

folly/io/BUCK

@@ -34,6 +34,7 @@ cpp_library(
         "//folly:portability",
         "//folly:range",
         "//folly:scope_guard",
+        "//folly/container:span",
         "//folly/detail:iterators",
         "//folly/lang:bits",
         "//folly/lang:checked_math",

folly/io/Cursor.h

@@ -22,13 +22,13 @@
 #include <cstring>
 #include <memory>
 #include <stdexcept>
-#include <string_view>
 #include <type_traits>
 
 #include <folly/Likely.h>
 #include <folly/Memory.h>
 #include <folly/Portability.h>
 #include <folly/Range.h>
+#include <folly/container/span.h>
 #include <folly/io/IOBuf.h>
 #include <folly/io/IOBufQueue.h>
 #include <folly/lang/Bits.h>
@@ -678,29 +678,16 @@ class CursorBase {
   }
 
   /**
-   * Alternate version of peekBytes() that returns a std::basic_string_view
+   * Alternate version of peekBytes() that returns a std::span
    * instead of a ByteRage.
    *
    * @methodset Accessors
    */
-  std::basic_string_view<uint8_t> peekView() {
+  span<uint8_t const> peek() {
     auto bytes = peekBytes();
     return {bytes.data(), bytes.size()};
   }
 
-  /**
-   * Alternate version of peekBytes() that returns a std::pair
-   * instead of a ByteRange.
-   *
-   * @methodset Accessors
-   *
-   * This function will eventually be deprecated.
-   */
-  std::pair<const uint8_t*, size_t> peek() {
-    auto bytes = peekBytes();
-    return std::make_pair(bytes.data(), bytes.size());
-  }
-
   /**
    * Clone len bytes from this cursor into an IOBuf.
    *

folly/io/test/IOBufCursorTest.cpp

@@ -218,18 +218,18 @@ TEST(IOBuf, PullAndPeek) {
   {
     RWPrivateCursor cursor(iobuf1.get());
     auto b = cursor.peekBytes();
-    EXPECT_EQ(b.data(), cursor.peekView().data());
-    EXPECT_EQ(b.size(), cursor.peekView().size());
+    EXPECT_EQ(b.data(), cursor.peek().data());
+    EXPECT_EQ(b.size(), cursor.peek().size());
     EXPECT_EQ("he", StringPiece(b));
     cursor.skip(b.size());
     b = cursor.peekBytes();
-    EXPECT_EQ(b.data(), cursor.peekView().data());
-    EXPECT_EQ(b.size(), cursor.peekView().size());
+    EXPECT_EQ(b.data(), cursor.peek().data());
+    EXPECT_EQ(b.size(), cursor.peek().size());
     EXPECT_EQ("llo ", StringPiece(b));
     cursor.skip(b.size());
     b = cursor.peekBytes();
-    EXPECT_EQ(b.data(), cursor.peekView().data());
-    EXPECT_EQ(b.size(), cursor.peekView().size());
+    EXPECT_EQ(b.data(), cursor.peek().data());
+    EXPECT_EQ(b.size(), cursor.peek().size());
     EXPECT_EQ("world", StringPiece(b));
     cursor.skip(b.size());
     EXPECT_EQ(3, iobuf1->countChainElements());
@@ -240,8 +240,8 @@ TEST(IOBuf, PullAndPeek) {
     RWPrivateCursor cursor(iobuf1.get());
     cursor.gather(11);
     auto b = cursor.peekBytes();
-    EXPECT_EQ(b.data(), cursor.peekView().data());
-    EXPECT_EQ(b.size(), cursor.peekView().size());
+    EXPECT_EQ(b.data(), cursor.peek().data());
+    EXPECT_EQ(b.size(), cursor.peek().size());
     EXPECT_EQ("hello world", StringPiece(b));
     EXPECT_EQ(1, iobuf1->countChainElements());
     EXPECT_EQ(11, iobuf1->computeChainDataLength());
@@ -1568,18 +1568,18 @@ TEST(IOBuf, BoundedCursorPullAndPeek) {
   {
     Cursor subCursor(iobuf1.get(), 13);
     auto b = subCursor.peekBytes();
-    EXPECT_EQ(b.data(), subCursor.peekView().data());
-    EXPECT_EQ(b.size(), subCursor.peekView().size());
+    EXPECT_EQ(b.data(), subCursor.peek().data());
+    EXPECT_EQ(b.size(), subCursor.peek().size());
     EXPECT_EQ("he", StringPiece(b));
     subCursor.skip(b.size());
     b = subCursor.peekBytes();
-    EXPECT_EQ(b.data(), subCursor.peekView().data());
-    EXPECT_EQ(b.size(), subCursor.peekView().size());
+    EXPECT_EQ(b.data(), subCursor.peek().data());
+    EXPECT_EQ(b.size(), subCursor.peek().size());
     EXPECT_EQ("llo ", StringPiece(b));
     subCursor.skip(b.size());
     b = subCursor.peekBytes();
-    EXPECT_EQ(b.data(), subCursor.peekView().data());
-    EXPECT_EQ(b.size(), subCursor.peekView().size());
+    EXPECT_EQ(b.data(), subCursor.peek().data());
+    EXPECT_EQ(b.size(), subCursor.peek().size());
     EXPECT_EQ("world a", StringPiece(b));
     subCursor.skip(b.size());
     EXPECT_EQ(3, iobuf1->countChainElements());

folly/somerge_defs.bzl

@@ -2,7 +2,7 @@
 
 Generated by xplat/cross_plat_devx/somerge_maps/compute_merge_maps.py
 
-@generated SignedSource<<4d6c648a98484ebd6d13a39719f413d2>>
+@generated SignedSource<<be29d3bd36c7d732d1042df61b88bf15>>
 """
 
 # Entry Points:
@@ -132,6 +132,7 @@ FOLLY_BASE_NATIVE_LIBRARY_MERGE_MAP = [
     "fbsource//xplat/folly/container:reserveAndroid",
     "fbsource//xplat/folly/container:small_vectorAndroid",
     "fbsource//xplat/folly/container:sorted_vector_typesAndroid",
+    "fbsource//xplat/folly/container:spanAndroid",
     "fbsource//xplat/folly/container:viewAndroid",
     "fbsource//xplat/folly/coro:traitsAndroid",
     "fbsource//xplat/folly/detail:async_traceAndroid",