stream: Implement seek operation support via ioctl, wrapped in generic method.

Also, implement for unix port.

py/obj.h

@@ -231,8 +231,6 @@ void mp_get_buffer_raise(mp_obj_t obj, mp_buffer_info_t *bufinfo, mp_uint_t flag
 
 // Stream protocol
 #define MP_STREAM_ERROR (-1)
-#define MP_STREAM_FLUSH (1)
-#define MP_STREAM_POLL  (2)
 typedef struct _mp_stream_p_t {
     // On error, functions should return MP_STREAM_ERROR and fill in *errcode (values
     // are implementation-dependent, but will be exposed to user, e.g. via exception).
@@ -242,6 +240,17 @@ typedef struct _mp_stream_p_t {
     mp_uint_t is_text : 1; // default is bytes, set this for text stream
 } mp_stream_p_t;
 
+// Stream ioctl request codes
+#define MP_STREAM_FLUSH (1)
+#define MP_STREAM_SEEK  (2)
+#define MP_STREAM_POLL  (3)
+
+// Argument structure for MP_STREAM_SEEK
+struct mp_stream_seek_t {
+    mp_off_t offset;
+    int whence;
+};
+
 struct _mp_obj_type_t {
     mp_obj_base_t base;
     qstr name;

py/qstrdefs.h

@@ -455,6 +455,7 @@ Q(readall)
 Q(readinto)
 Q(readline)
 Q(readlines)
+Q(seek)
 Q(FileIO)
 Q(TextIOWrapper)
 Q(StringIO)

py/stream.c

@@ -380,6 +380,32 @@ mp_obj_t mp_stream_unbuffered_iter(mp_obj_t self) {
     return MP_OBJ_STOP_ITERATION;
 }
 
+STATIC mp_obj_t stream_seek(mp_uint_t n_args, const mp_obj_t *args) {
+    struct _mp_obj_base_t *o = (struct _mp_obj_base_t *)args[0];
+    if (o->type->stream_p == NULL || o->type->stream_p->read == NULL) {
+        // CPython: io.UnsupportedOperation, OSError subclass
+        nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "Operation not supported"));
+    }
+
+    struct mp_stream_seek_t seek_s;
+    // TODO: Could be uint64
+    seek_s.offset = mp_obj_get_int(args[1]);
+    seek_s.whence = 0;
+    if (n_args == 3) {
+        seek_s.whence = mp_obj_get_int(args[2]);
+    }
+
+    int error;
+    mp_uint_t res = o->type->stream_p->ioctl(o, MP_STREAM_SEEK, (mp_uint_t)&seek_s, &error);
+    if (res == MP_STREAM_ERROR) {
+        nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(error)));
+    }
+
+    // TODO: Could be uint64
+    return mp_obj_new_int_from_uint(seek_s.offset);
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_stream_seek_obj, 2, 3, stream_seek);
+
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_stream_read_obj, 1, 2, stream_read);
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_stream_readinto_obj, 2, 3, stream_readinto);
 MP_DEFINE_CONST_FUN_OBJ_1(mp_stream_readall_obj, stream_readall);

py/stream.h

@@ -30,6 +30,7 @@ MP_DECLARE_CONST_FUN_OBJ(mp_stream_readall_obj);
 MP_DECLARE_CONST_FUN_OBJ(mp_stream_unbuffered_readline_obj);
 MP_DECLARE_CONST_FUN_OBJ(mp_stream_unbuffered_readlines_obj);
 MP_DECLARE_CONST_FUN_OBJ(mp_stream_write_obj);
+MP_DECLARE_CONST_FUN_OBJ(mp_stream_seek_obj);
 
 // Iterator which uses mp_stream_unbuffered_readline_obj
 mp_obj_t mp_stream_unbuffered_iter(mp_obj_t self);

unix/file.c

@@ -88,6 +88,23 @@ STATIC mp_uint_t fdfile_write(mp_obj_t o_in, const void *buf, mp_uint_t size, in
     return r;
 }
 
+STATIC mp_uint_t fdfile_ioctl(mp_obj_t o_in, mp_uint_t request, mp_uint_t arg, int *errcode) {
+    mp_obj_fdfile_t *o = o_in;
+    if (request == MP_STREAM_SEEK) {
+        struct mp_stream_seek_t *s = (struct mp_stream_seek_t*)arg;
+        off_t off = lseek(o->fd, s->offset, s->whence);
+        if (off == (off_t)-1) {
+            *errcode = errno;
+            return MP_STREAM_ERROR;
+        }
+        s->offset = off;
+        return 0;
+    } else {
+        *errcode = EINVAL;
+        return MP_STREAM_ERROR;
+    }
+}
+
 STATIC mp_obj_t fdfile_flush(mp_obj_t self_in) {
     mp_obj_fdfile_t *self = self_in;
     check_fd_is_open(self);
@@ -192,6 +209,7 @@ STATIC const mp_map_elem_t rawfile_locals_dict_table[] = {
     { MP_OBJ_NEW_QSTR(MP_QSTR_readline), (mp_obj_t)&mp_stream_unbuffered_readline_obj},
     { MP_OBJ_NEW_QSTR(MP_QSTR_readlines), (mp_obj_t)&mp_stream_unbuffered_readlines_obj},
     { MP_OBJ_NEW_QSTR(MP_QSTR_write), (mp_obj_t)&mp_stream_write_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_seek), (mp_obj_t)&mp_stream_seek_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_flush), (mp_obj_t)&fdfile_flush_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_close), (mp_obj_t)&fdfile_close_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR___enter__), (mp_obj_t)&mp_identity_obj },
@@ -204,6 +222,7 @@ STATIC MP_DEFINE_CONST_DICT(rawfile_locals_dict, rawfile_locals_dict_table);
 STATIC const mp_stream_p_t fileio_stream_p = {
     .read = fdfile_read,
     .write = fdfile_write,
+    .ioctl = fdfile_ioctl,
 };
 
 const mp_obj_type_t mp_type_fileio = {

unix/mpconfigport.h

@@ -122,6 +122,13 @@ typedef unsigned int mp_uint_t; // must be pointer size
 
 #define BYTES_PER_WORD sizeof(mp_int_t)
 
+// Cannot include <sys/types.h>, as it may lead to symbol name clashes
+#if _FILE_OFFSET_BITS == 64 && !defined(__LP64__)
+typedef long long mp_off_t;
+#else
+typedef long mp_off_t;
+#endif
+
 typedef void *machine_ptr_t; // must be of pointer size
 typedef const void *machine_const_ptr_t; // must be of pointer size