Edited VFSFileImpl::read to use both read/fread (espressif#6456)

* Edited VFSFileImpl::read to use both read/fread

* Added missing include

libraries/FS/src/vfs_api.cpp

@@ -13,9 +13,12 @@
 // limitations under the License.
 
 #include "vfs_api.h"
+#include <stdio_ext.h>
 
 using namespace fs;
 
+#define READ_SIZE_SWITCH 128 //swithc to read func when read size > 128bytes
+
 FileImplPtr VFSImpl::open(const char* fpath, const char* mode, const bool create)
 {
  if(!_mountpoint) {
@@ -374,7 +377,28 @@ size_t VFSFileImpl::read(uint8_t* buf, size_t size)
  return 0;
  }
 
- return fread(buf, 1, size, _f);
+ //ERASE BYTEBUFFER and use read when size > READ_SIZE_SWITCH always
+ if(size > READ_SIZE_SWITCH)
+ {
+ //check some data in buffer exists –> clear buffer and move pointer to deleted data
+ size_t bytesinbuf = __fpending(_f);
+ if (bytesinbuf && (bytesinbuf != 128)) //buffer lenght is 128 bytes
+ {
+ fpurge(_f);
+ lseek(fileno(_f),(-128+bytesinbuf),SEEK_CUR);
+ }
+
+ int res = ::read(fileno(_f), buf, size);
+ if (res < 0) {
+ // an error occurred
+ return 0;
+ }
+ return res;
+ }
+ else
+ {
+ return fread(buf, 1, size, _f);
+ }
 }
 
 void VFSFileImpl::flush()