Make hb_blob_create_from_file more portable (#1027)

This makes it compatible with ARMCC which I had access in
a collaboration with @imgtec, thanks!

Basically hb_blob_create_from_file features three code paths,
mmap, Win32 and fallback.

We had fallback implementation even before this but it was relied
to "open" which is not available on some environments. This change
improved the situtation by using only fopen and friends for
fallback path.

Interestingly we could use "open" on Windows but in fact it was
emulated by MSVCRT so I've completely split that from Unix path
now that we have a distinct path for fallback path also.

src/hb-blob.cc

 /*
  * Copyright © 2009  Red Hat, Inc.
+ * Copyright © 2018  Ebrahim Byagowi
  *
  *  This is part of HarfBuzz, a text shaping library.
  *
@@ -43,10 +44,6 @@
 #include <stdio.h>
 #include <errno.h>
 #include <stdlib.h>
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <fcntl.h>
-
 
 
 /**
@@ -484,6 +481,12 @@ hb_blob_t::try_make_writable (void)
  * Mmap
  */
 
+#ifdef HAVE_MMAP
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#endif
+
 #if defined(_WIN32) || defined(__CYGWIN__)
 #include <windows.h>
 #include <io.h>
@@ -542,31 +545,40 @@ hb_blob_t *
 hb_blob_create_from_file (const char *file_name)
 {
   // Adopted from glib's gmappedfile.c with Matthias Clasen and
-  // Allison Lortie permission but changed to suit our need.
+  // Allison Lortie permission but changed a lot to suit our need.
   bool writable = false;
   hb_memory_mode_t mm = HB_MEMORY_MODE_READONLY_MAY_MAKE_WRITABLE;
+  hb_mapped_file_t *file = (hb_mapped_file_t *) calloc (1, sizeof (hb_mapped_file_t));
+  if (unlikely (!file)) return hb_blob_get_empty ();
 
+#ifdef HAVE_MMAP
   int fd = open (file_name, (writable ? O_RDWR : O_RDONLY) | _O_BINARY, 0);
-  if (unlikely (fd == -1)) return hb_blob_get_empty ();
-
-  hb_mapped_file_t *file = (hb_mapped_file_t *) calloc (1, sizeof (hb_mapped_file_t));
+# define CLOSE close
+  if (unlikely (fd == -1)) goto fail_without_close;
 
   struct stat st;
   if (unlikely (fstat (fd, &st) == -1)) goto fail;
 
-  // If the file size is 0 and is a regular file, give up
   // See https://github.com/GNOME/glib/blob/f9faac7/glib/gmappedfile.c#L139-L142
   if (unlikely (st.st_size == 0 && S_ISREG (st.st_mode))) goto fail;
 
   file->length = (unsigned long) st.st_size;
-
-#ifdef HAVE_MMAP
   file->contents = (char *) mmap (nullptr, file->length,
 				  writable ? PROT_READ|PROT_WRITE : PROT_READ,
 				  MAP_PRIVATE, fd, 0);
+
   if (unlikely (file->contents == MAP_FAILED)) goto fail;
+
 #elif defined(_WIN32) || defined(__CYGWIN__)
-  file->mapping = CreateFileMapping ((HANDLE) _get_osfhandle (fd), nullptr,
+  HANDLE fd = CreateFile (file_name, GENERIC_READ, FILE_SHARE_READ, nullptr,
+			  OPEN_EXISTING,
+			  FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED, nullptr);
+# define CLOSE CloseHandle
+
+  if (unlikely (fd == INVALID_HANDLE_VALUE)) goto fail_without_close;
+
+  file->length = (unsigned long) GetFileSize (fd, nullptr);
+  file->mapping = CreateFileMapping (fd, nullptr,
 				     writable ? PAGE_WRITECOPY : PAGE_READONLY,
 				     0, 0, nullptr);
   if (unlikely (file->mapping == nullptr)) goto fail;
@@ -574,24 +586,34 @@ hb_blob_create_from_file (const char *file_name)
   file->contents = (char *) MapViewOfFile (file->mapping,
 					   writable ? FILE_MAP_COPY : FILE_MAP_READ,
 					   0, 0, 0);
-  if (unlikely (file->contents == nullptr))
-  {
-    CloseHandle (file->mapping);
-    goto fail;
-  }
+  if (unlikely (file->contents == nullptr)) goto fail;
+
 #else
+  mm = HB_MEMORY_MODE_WRITABLE;
+
+  FILE *fd = fopen (file_name, "rb");
+# define CLOSE fclose
+  if (unlikely (!fd)) goto fail_without_close;
+
+  fseek (fd, 0, SEEK_END);
+  file->length = ftell (fd);
+  rewind (fd);
   file->contents = (char *) malloc (file->length);
   if (unlikely (!file->contents)) goto fail;
-  read (fd, file->contents, file->length);
-  mm = HB_MEMORY_MODE_WRITABLE;
+
+  if (unlikely (fread (file->contents, 1, file->length, fd) != file->length))
+    goto fail;
+
 #endif
 
-  close (fd);
+  CLOSE (fd);
   return hb_blob_create (file->contents, file->length, mm, (void *) file,
 			 (hb_destroy_func_t) _hb_mapped_file_destroy);
 
 fail:
-  close (fd);
+  CLOSE (fd);
+#undef CLOSE
+fail_without_close:
   free (file);
   return hb_blob_get_empty ();
 }