py/stream: Add adapter methods with POSIX-compatible signatures.

Previoussly such read() and write() methods were used by modussl_axtls,
move to py/stream for reuse.

extmod/modussl_axtls.c

@@ -200,34 +200,4 @@ const mp_obj_module_t mp_module_ussl = {
     .globals = (mp_obj_dict_t*)&mp_module_ssl_globals,
 };
 
-
-// These functions might be split to stream_posix.c. They are referenced by
-// axtls os_port.h .
-ssize_t mp_stream_posix_write(void *sock_obj, const void *buf, size_t len);
-ssize_t mp_stream_posix_read(void *sock_obj, void *buf, size_t len);
-
-int mp_stream_errno;
-
-ssize_t mp_stream_posix_write(void *sock_obj, const void *buf, size_t len) {
-    struct _mp_obj_base_t *o = (struct _mp_obj_base_t *)sock_obj;
-    const mp_stream_p_t *stream_p = o->type->protocol;
-    mp_uint_t out_sz = stream_p->write(o, buf, len, &mp_stream_errno);
-    if (out_sz == MP_STREAM_ERROR) {
-        return -1;
-    } else {
-        return out_sz;
-    }
-}
-
-ssize_t mp_stream_posix_read(void *sock_obj, void *buf, size_t len) {
-    struct _mp_obj_base_t *o = (struct _mp_obj_base_t *)sock_obj;
-    const mp_stream_p_t *stream_p = o->type->protocol;
-    mp_uint_t out_sz = stream_p->read(o, buf, len, &mp_stream_errno);
-    if (out_sz == MP_STREAM_ERROR) {
-        return -1;
-    } else {
-        return out_sz;
-    }
-}
-
 #endif // MICROPY_PY_USSL

py/stream.c

@@ -510,3 +510,61 @@ STATIC mp_obj_t stream_ioctl(size_t n_args, const mp_obj_t *args) {
     return mp_obj_new_int(res);
 }
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_stream_ioctl_obj, 2, 3, stream_ioctl);
+
+/*
+ * POSIX-like functions
+ *
+ * These functions have POSIX-compatible signature (except for "void *stream"
+ * first argument instead of "int fd"). They are useful to port existing
+ * POSIX-compatible software to work with MicroPython streams.
+ */
+
+
+// errno-like variable. If any of the functions below returned with error
+// status, this variable will contain error no.
+int mp_stream_errno;
+
+ssize_t mp_stream_posix_write(mp_obj_t stream, const void *buf, size_t len) {
+    mp_obj_base_t* o = (mp_obj_base_t*)MP_OBJ_TO_PTR(stream);
+    const mp_stream_p_t *stream_p = o->type->protocol;
+    mp_uint_t out_sz = stream_p->write(stream, buf, len, &mp_stream_errno);
+    if (out_sz == MP_STREAM_ERROR) {
+        return -1;
+    } else {
+        return out_sz;
+    }
+}
+
+ssize_t mp_stream_posix_read(mp_obj_t stream, void *buf, size_t len) {
+    mp_obj_base_t* o = (mp_obj_base_t*)MP_OBJ_TO_PTR(stream);
+    const mp_stream_p_t *stream_p = o->type->protocol;
+    mp_uint_t out_sz = stream_p->read(stream, buf, len, &mp_stream_errno);
+    if (out_sz == MP_STREAM_ERROR) {
+        return -1;
+    } else {
+        return out_sz;
+    }
+}
+
+off_t mp_stream_posix_lseek(mp_obj_t stream, off_t offset, int whence) {
+    const mp_obj_base_t* o = (mp_obj_base_t*)MP_OBJ_TO_PTR(stream);
+    const mp_stream_p_t *stream_p = o->type->protocol;
+    struct mp_stream_seek_t seek_s;
+    seek_s.offset = offset;
+    seek_s.whence = whence;
+    mp_uint_t res = stream_p->ioctl(stream, MP_STREAM_SEEK, (mp_uint_t)(uintptr_t)&seek_s, &mp_stream_errno);
+    if (res == MP_STREAM_ERROR) {
+        return -1;
+    }
+    return seek_s.offset;
+}
+
+int mp_stream_posix_fsync(mp_obj_t stream) {
+    mp_obj_base_t* o = (mp_obj_base_t*)MP_OBJ_TO_PTR(stream);
+    const mp_stream_p_t *stream_p = o->type->protocol;
+    mp_uint_t res = stream_p->ioctl(stream, MP_STREAM_FLUSH, 0, &mp_stream_errno);
+    if (res == MP_STREAM_ERROR) {
+        return -1;
+    }
+    return res;
+}

py/stream.h

@@ -84,6 +84,12 @@ mp_uint_t mp_stream_rw(mp_obj_t stream, void *buf, mp_uint_t size, int *errcode,
 
 void mp_stream_write_adaptor(void *self, const char *buf, size_t len);
 
+// Functions with POSIX-compatible signatures
+ssize_t mp_stream_posix_write(mp_obj_t stream, const void *buf, size_t len);
+ssize_t mp_stream_posix_read(mp_obj_t stream, void *buf, size_t len);
+off_t mp_stream_posix_lseek(mp_obj_t stream, off_t offset, int whence);
+int mp_stream_posix_fsync(mp_obj_t stream);
+
 #if MICROPY_STREAMS_NON_BLOCK
 #define mp_is_nonblocking_error(errno) ((errno) == EAGAIN || (errno) == EWOULDBLOCK)
 #else