Various minor changes to allow compliation with msvc (#22182)

Summary:
This change is aiming to reduce some of the forking changes we have internally in order to use CxxReact for some additional out of tree platforms.

Some of the fixes allow more of the code to compile when using Microsoft Visual Studio Compiler. In particular the change around the default value of RN_EXPORT and some changes around how to enable the packing attribute.

Another change moves more of the code for JSBigFileString into the cpp file, so that people can share the header but replace the implementation as appropriate for other platforms.

And finally the removal of an unused header include.

This is unlikely to be the extent of the changes required for MSVC, but at least gets one of our complication blocks to work against an unforked RN.
Pull Request resolved: https://github.com/facebook/react-native/pull/22182

Differential Revision: D12967758

Pulled By: cpojer

fbshipit-source-id: a2cc018aedaa9916cd644bfbd9e3a55330cd4c52

ReactCommon/cxxreact/JSBigString.cpp

@@ -9,11 +9,65 @@
 #include <sys/stat.h>
 
 #include <folly/Memory.h>
+#include <folly/portability/SysMman.h>
 #include <folly/ScopeGuard.h>
 
 namespace facebook {
 namespace react {
 
+JSBigFileString::JSBigFileString(int fd, size_t size, off_t offset /*= 0*/)
+  : m_fd { -1 }
+  , m_data { nullptr } {
+  folly::checkUnixError(m_fd = dup(fd),
+    "Could not duplicate file descriptor");
+
+  // Offsets given to mmap must be page aligend. We abstract away that
+  // restriction by sending a page aligned offset to mmap, and keeping track
+  // of the offset within the page that we must alter the mmap pointer by to
+  // get the final desired offset.
+  if (offset != 0) {
+    const static auto ps = getpagesize();
+    auto d = lldiv(offset, ps);
+
+    m_mapOff = d.quot;
+    m_pageOff = d.rem;
+    m_size = size + m_pageOff;
+  } else {
+    m_mapOff = 0;
+    m_pageOff = 0;
+    m_size = size;
+  }
+}
+
+JSBigFileString::~JSBigFileString() {
+  if (m_data) {
+    munmap((void *)m_data, m_size);
+  }
+  close(m_fd);
+}
+
+
+const char *JSBigFileString::c_str() const {
+  if (!m_data) {
+    m_data =
+      (const char *) mmap(0, m_size, PROT_READ, MAP_SHARED, m_fd, m_mapOff);
+    CHECK(m_data != MAP_FAILED)
+      << " fd: " << m_fd
+      << " size: " << m_size
+      << " offset: " << m_mapOff
+      << " error: " << std::strerror(errno);
+  }
+  return m_data + m_pageOff;
+}
+
+size_t JSBigFileString::size() const {
+  return m_size - m_pageOff;
+}
+
+int JSBigFileString::fd() const {
+  return m_fd;
+}
+
 std::unique_ptr<const JSBigFileString> JSBigFileString::fromPath(const std::string& sourceURL) {
   int fd = ::open(sourceURL.c_str(), O_RDONLY);
   folly::checkUnixError(fd, "Could not open file", sourceURL);

ReactCommon/cxxreact/JSBigString.h

@@ -13,7 +13,11 @@
 #include <folly/Exception.h>
 
 #ifndef RN_EXPORT
-#define RN_EXPORT __attribute__((visibility("default")))
+# ifdef _MSC_VER
+#  define RN_EXPORT
+# else
+#  define RN_EXPORT __attribute__((visibility("default")))
+# endif
 #endif
 
 namespace facebook {
@@ -74,7 +78,7 @@ private:
 // buffer, and provides an accessor for writing to it.  This can be
 // used to construct a JSBigString in place, such as by reading from a
 // file.
-class JSBigBufferString : public JSBigString {
+class RN_EXPORT JSBigBufferString : public JSBigString {
 public:
   JSBigBufferString(size_t size)
   : m_data(new char[size + 1])
@@ -113,62 +117,17 @@ private:
 class RN_EXPORT JSBigFileString : public JSBigString {
 public:
 
-  JSBigFileString(int fd, size_t size, off_t offset = 0)
-  : m_fd   {-1}
-  , m_data {nullptr}
-  {
-    folly::checkUnixError(m_fd = dup(fd),
-      "Could not duplicate file descriptor");
-
-    // Offsets given to mmap must be page aligend. We abstract away that
-    // restriction by sending a page aligned offset to mmap, and keeping track
-    // of the offset within the page that we must alter the mmap pointer by to
-    // get the final desired offset.
-    if (offset != 0) {
-      const static auto ps = getpagesize();
-      auto d  = lldiv(offset, ps);
-
-      m_mapOff  = d.quot;
-      m_pageOff = d.rem;
-      m_size    = size + m_pageOff;
-    } else {
-      m_mapOff  = 0;
-      m_pageOff = 0;
-      m_size    = size;
-    }
-  }
-
-  ~JSBigFileString() {
-    if (m_data) {
-      munmap((void *)m_data, m_size);
-    }
-    close(m_fd);
-  }
+  JSBigFileString(int fd, size_t size, off_t offset = 0);
+  ~JSBigFileString();
 
   bool isAscii() const override {
     return true;
   }
 
-  const char *c_str() const override {
-    if (!m_data) {
-      m_data =
-        (const char *)mmap(0, m_size, PROT_READ, MAP_PRIVATE, m_fd, m_mapOff);
-      CHECK(m_data != MAP_FAILED)
-      << " fd: " << m_fd
-      << " size: " << m_size
-      << " offset: " << m_mapOff
-      << " error: " << std::strerror(errno);
-    }
-    return m_data + m_pageOff;
-  }
+  const char *c_str() const override;
 
-  size_t size() const override {
-    return m_size - m_pageOff;
-  }
-
-  int fd() const {
-    return m_fd;
-  }
+  size_t size() const override;
+  int fd() const;
 
   static std::unique_ptr<const JSBigFileString> fromPath(const std::string& sourceURL);
 

ReactCommon/cxxreact/JSBundleType.h

@@ -7,6 +7,7 @@
 
 #include <cstdint>
 #include <cstring>
+#include <folly/Portability.h>
 
 #ifndef RN_EXPORT
 #define RN_EXPORT __attribute__((visibility("default")))
@@ -34,7 +35,8 @@ enum struct ScriptTag {
  * 4 bytes, for BC bundles this is 12 bytes. This structure holds the first 12
  * bytes from a bundle in a way that gives access to that information.
  */
-struct __attribute__((packed)) BundleHeader {
+FOLLY_PACK_PUSH
+struct FOLLY_PACK_ATTR BundleHeader {
   BundleHeader() {
     std::memset(this, 0, sizeof(BundleHeader));
   }
@@ -43,6 +45,7 @@ struct __attribute__((packed)) BundleHeader {
   uint32_t reserved_;
   uint32_t version;
 };
+FOLLY_PACK_POP
 
 /**
  * parseTypeFromHeader

ReactCommon/cxxreact/RAMBundleRegistry.cpp

@@ -8,8 +8,6 @@
 #include <folly/Memory.h>
 #include <folly/String.h>
 
-#include <libgen.h>
-
 namespace facebook {
 namespace react {
 

ReactCommon/cxxreact/tests/BUCK

@@ -32,6 +32,7 @@ jni_instrumentation_test_lib(
         "xplat//third-party/linker_lib:android",
         "xplat//third-party/linker_lib:atomic",
         react_native_xplat_target("cxxreact:bridge"),
+        react_native_xplat_target("cxxreact:jsbigstring"),
     ],
 )
 
@@ -50,5 +51,6 @@ fb_xplat_cxx_test(
         "xplat//folly:molly",
         "xplat//third-party/gmock:gtest",
         react_native_xplat_target("cxxreact:bridge"),
+        react_native_xplat_target("cxxreact:jsbigstring"),
     ],
 )