extmod/vfs_posix_file: Implement sys.std*.buffer objects.

Add the buffer attribute to sys.stdin, sys.stdout and sys.stderr.  This
provides raw access to underlying stdio streams for the unix port (and
others that use VfsPosix).

Signed-off-by: stephanelsmith <stephane.smith@titansensor.com>

extmod/vfs_posix_file.c

@@ -274,12 +274,58 @@ STATIC const mp_stream_p_t vfs_posix_textio_stream_p = {
     .is_text = true,
 };
 
+#if MICROPY_PY_SYS_STDIO_BUFFER
+
+const mp_obj_vfs_posix_file_t mp_sys_stdin_buffer_obj = {{&mp_type_vfs_posix_fileio}, STDIN_FILENO};
+const mp_obj_vfs_posix_file_t mp_sys_stdout_buffer_obj = {{&mp_type_vfs_posix_fileio}, STDOUT_FILENO};
+const mp_obj_vfs_posix_file_t mp_sys_stderr_buffer_obj = {{&mp_type_vfs_posix_fileio}, STDERR_FILENO};
+
+// Forward declarations.
+const mp_obj_vfs_posix_file_t mp_sys_stdin_obj;
+const mp_obj_vfs_posix_file_t mp_sys_stdout_obj;
+const mp_obj_vfs_posix_file_t mp_sys_stderr_obj;
+
+STATIC void vfs_posix_textio_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
+    if (dest[0] != MP_OBJ_NULL) {
+        // These objects are read-only.
+        return;
+    }
+
+    if (attr == MP_QSTR_buffer) {
+        // Implement the `buffer` attribute only on std{in,out,err} instances.
+        if (MP_OBJ_TO_PTR(self_in) == &mp_sys_stdin_obj) {
+            dest[0] = MP_OBJ_FROM_PTR(&mp_sys_stdin_buffer_obj);
+            return;
+        }
+        if (MP_OBJ_TO_PTR(self_in) == &mp_sys_stdout_obj) {
+            dest[0] = MP_OBJ_FROM_PTR(&mp_sys_stdout_buffer_obj);
+            return;
+        }
+        if (MP_OBJ_TO_PTR(self_in) == &mp_sys_stderr_obj) {
+            dest[0] = MP_OBJ_FROM_PTR(&mp_sys_stderr_buffer_obj);
+            return;
+        }
+    }
+
+    // Any other attribute - forward to locals dict.
+    dest[1] = MP_OBJ_SENTINEL;
+};
+
+#define VFS_POSIX_TEXTIO_TYPE_ATTR attr, vfs_posix_textio_attr,
+
+#else
+
+#define VFS_POSIX_TEXTIO_TYPE_ATTR
+
+#endif // MICROPY_PY_SYS_STDIO_BUFFER
+
 MP_DEFINE_CONST_OBJ_TYPE(
     mp_type_vfs_posix_textio,
     MP_QSTR_TextIOWrapper,
     MP_TYPE_FLAG_ITER_IS_STREAM,
     print, vfs_posix_file_print,
     protocol, &vfs_posix_textio_stream_p,
+    VFS_POSIX_TEXTIO_TYPE_ATTR
     locals_dict, &vfs_posix_rawfile_locals_dict
     );
 

tests/io/file_stdio.py

@@ -2,3 +2,4 @@ import sys
 
 print(sys.stdin.fileno())
 print(sys.stdout.fileno())
+print(sys.stderr.fileno())

tests/io/file_stdio2.py

@@ -0,0 +1,65 @@
+# Test sys.std*.buffer objects.
+
+import sys
+
+try:
+    sys.stdout.buffer
+    sys.stdin.buffer
+    sys.stderr.buffer
+except AttributeError:
+    print("SKIP")
+    raise SystemExit
+
+
+# force cpython to flush after every print
+# this is to sequence stdout and stderr
+def print_flush(*args, **kwargs):
+    try:
+        print(*args, **kwargs, flush=True)
+    except TypeError:
+        print(*args, **kwargs)
+
+
+print_flush("==stdin==")
+print_flush(sys.stdin.buffer.fileno())
+
+
+print_flush("==stdout==")
+print_flush(sys.stdout.buffer.fileno())
+n_text = sys.stdout.write("The quick brown fox jumps over the lazy dog\n")
+sys.stdout.flush()
+n_binary = sys.stdout.buffer.write("The quick brown fox jumps over the lazy dog\n".encode("utf-8"))
+sys.stdout.buffer.flush()
+print_flush("n_text:{} n_binary:{}".format(n_text, n_binary))
+
+# temporarily disabling unicode tests until future PR which fixes unicode write character count
+# n_text = sys.stdout.write("🚀")
+# sys.stdout.flush()
+# n_binary = sys.stdout.buffer.write("🚀".encode("utf-8"))
+# sys.stdout.buffer.flush()
+# print_flush("")
+# print_flush("n_text:{} n_binary:{}".format(n_text, n_binary))
+# n_text = sys.stdout.write("1🚀2a3α4b5β6c7γ8d9δ0ぁ1🙐")
+# sys.stdout.flush()
+# n_binary = sys.stdout.buffer.write("1🚀2a3α4b5β6c7γ8d9δ0ぁ1🙐".encode("utf-8"))
+# sys.stdout.buffer.flush()
+# print_flush("")
+# print_flush("n_text:{} n_binary:{}".format(n_text, n_binary))
+
+
+print_flush("==stderr==")
+print_flush(sys.stderr.buffer.fileno())
+n_text = sys.stderr.write("The quick brown fox jumps over the lazy dog\n")
+sys.stderr.flush()
+n_binary = sys.stderr.buffer.write("The quick brown fox jumps over the lazy dog\n".encode("utf-8"))
+sys.stderr.buffer.flush()
+print_flush("n_text:{} n_binary:{}".format(n_text, n_binary))
+
+# temporarily disabling unicode tests until future PR which fixes unicode write character count
+# n_text = sys.stderr.write("🚀")
+# sys.stderr.flush()
+# n_binary = sys.stderr.buffer.write("🚀".encode("utf-8"))
+# sys.stderr.buffer.flush()
+# print_flush("")
+# print_flush("n_text:{} n_binary:{}".format(n_text, n_binary))
+# print_flush("")