diff --git a/spacy/cfile.pxd b/spacy/cfile.pxd
index c9a6aec41..cb0077587 100644
--- a/spacy/cfile.pxd
+++ b/spacy/cfile.pxd
@@ -4,6 +4,20 @@ from cymem.cymem cimport Pool
 cdef class CFile:
     cdef FILE* fp
     cdef bint is_open
+    cdef Pool mem
+    cdef int size # For compatibility with subclass
+    cdef int _capacity # For compatibility with subclass
+
+    cdef int read_into(self, void* dest, size_t number, size_t elem_size) except -1
+
+    cdef int write_from(self, void* src, size_t number, size_t elem_size) except -1
+
+    cdef void* alloc_read(self, Pool mem, size_t number, size_t elem_size) except *
+
+
+
+cdef class StringCFile(CFile):
+    cdef unsigned char* data
  
     cdef int read_into(self, void* dest, size_t number, size_t elem_size) except -1
 
diff --git a/spacy/cfile.pyx b/spacy/cfile.pyx
index b119d3b9b..95c61a468 100644
--- a/spacy/cfile.pyx
+++ b/spacy/cfile.pyx
@@ -1,4 +1,5 @@
 from libc.stdio cimport fopen, fclose, fread, fwrite, FILE
+from libc.string cimport memcpy
 
 
 cdef class CFile:
@@ -9,6 +10,7 @@ cdef class CFile:
             mode_str = mode
         if hasattr(loc, 'as_posix'):
             loc = loc.as_posix()
+        self.mem = Pool()
         cdef bytes bytes_loc = loc.encode('utf8') if type(loc) == unicode else loc
         self.fp = fopen(<char*>bytes_loc, mode_str)
         if self.fp == NULL:
@@ -45,3 +47,43 @@ cdef class CFile:
         cdef bytes py_bytes = value.encode('utf8')
         cdef char* chars = <char*>py_bytes
         self.write(sizeof(char), len(py_bytes), chars)
+
+
+cdef class StringCFile:
+    def __init__(self, mode, bytes data=b'', on_open_error=None):
+        self.mem = Pool()
+        self.is_open = 'w' in mode
+        self._capacity = max(len(data), 8)
+        self.size = len(data)
+        self.data = <unsigned char*>self.mem.alloc(1, self._capacity)
+        for i in range(len(data)):
+            self.data[i] = data
+
+    def close(self):
+        self.is_open = False
+
+    def string_data(self):
+        return (self.data-self.size)[:self.size]
+
+    cdef int read_into(self, void* dest, size_t number, size_t elem_size) except -1:
+        memcpy(dest, self.data, elem_size * number)
+        self.data += elem_size * number
+
+    cdef int write_from(self, void* src, size_t number, size_t elem_size) except -1:
+        write_size = number * elem_size
+        if (self.size + write_size) >= self._capacity:
+            self._capacity = (self.size + write_size) * 2
+            self.data = <unsigned char*>self.mem.realloc(self.data, self._capacity)
+        memcpy(self.data, src, elem_size * number)
+        self.data += write_size
+        self.size += write_size
+
+    cdef void* alloc_read(self, Pool mem, size_t number, size_t elem_size) except *:
+        cdef void* dest = mem.alloc(number, elem_size)
+        self.read_into(dest, number, elem_size)
+        return dest
+
+    def write_unicode(self, unicode value):
+        cdef bytes py_bytes = value.encode('utf8')
+        cdef char* chars = <char*>py_bytes
+        self.write(sizeof(char), len(py_bytes), chars)