unix: Add basic implementation of io.FileIO object.

Note: only read/write/close methods are defined so far, and class
is not exposed (use open() factory function, as usual).

unix/Makefile

@@ -16,6 +16,7 @@ LDFLAGS = -lm
 # source files
 SRC_C = \
 	main.c \
+	file.c \
 
 OBJ = $(addprefix $(BUILD)/, $(SRC_C:.c=.o)) $(PY_O)
 LIB = -lreadline

unix/file.c

+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+
+#include "nlr.h"
+#include "misc.h"
+#include "mpconfig.h"
+#include "mpqstr.h"
+#include "obj.h"
+#include "stream.h"
+
+typedef struct _mp_obj_fdfile_t {
+    mp_obj_base_t base;
+    int fd;
+} mp_obj_fdfile_t;
+
+static void fdfile_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in) {
+    mp_obj_fdfile_t *self = self_in;
+    print(env, "<io.FileIO %d>", self->fd);
+}
+
+static machine_int_t fdfile_read(mp_obj_t o_in, void *buf, machine_uint_t size, int *errcode) {
+    mp_obj_fdfile_t *o = o_in;
+    machine_int_t r = read(o->fd, buf, size);
+    if (r == -1) {
+        *errcode = errno;
+    }
+    return r;
+}
+
+static machine_int_t fdfile_write(mp_obj_t o_in, const void *buf, machine_uint_t size, int *errcode) {
+    mp_obj_fdfile_t *o = o_in;
+    machine_int_t r = write(o->fd, buf, size);
+    if (r == -1) {
+        *errcode = errno;
+    }
+    return r;
+}
+
+static mp_obj_t fdfile_close(mp_obj_t self_in) {
+    mp_obj_fdfile_t *self = self_in;
+    close(self->fd);
+    return mp_const_none;
+}
+static MP_DEFINE_CONST_FUN_OBJ_1(fdfile_close_obj, fdfile_close);
+
+static mp_obj_t fdfile_make_new(mp_obj_t type_in, int n_args, const mp_obj_t *args) {
+    mp_obj_fdfile_t *o = m_new_obj(mp_obj_fdfile_t);
+    o->base.type = type_in;
+
+    if (MP_OBJ_IS_SMALL_INT(args[0])) {
+        o->fd = MP_OBJ_SMALL_INT_VALUE(args[0]);
+        return o;
+    }
+
+    const char *fname = qstr_str(mp_obj_get_qstr(args[0]));
+    const char *mode_s;
+    if (n_args > 1) {
+        mode_s = qstr_str(mp_obj_get_qstr(args[1]));
+    } else {
+        mode_s = "r";
+    }
+
+    int mode = 0;
+    while (*mode_s) {
+        switch (*mode_s++) {
+            // Note: these assume O_RDWR = O_RDONLY | O_WRONLY
+            case 'r':
+                mode |= O_RDONLY;
+                break;
+            case 'w':
+                mode |= O_WRONLY | O_CREAT | O_TRUNC;
+                break;
+            case 'a':
+                mode |= O_APPEND;
+                break;
+            case '+':
+                mode |= O_RDWR;
+                break;
+        }
+    }
+
+    o->fd = open(fname, mode, 0644);
+    if (o->fd == -1) {
+        nlr_jump(mp_obj_new_exception_msg_1_arg(MP_QSTR_OSError, "[Errno %d]", (const char *)errno));
+    }
+    return o;
+}
+
+static const mp_method_t rawfile_type_methods[] = {
+        { "read", &mp_stream_read_obj },
+        { "write", &mp_stream_write_obj },
+        { "close", &fdfile_close_obj },
+        { NULL, NULL },
+};
+
+static const mp_obj_type_t rawfile_type = {
+    { &mp_const_type },
+    "io.FileIO",
+    .print = fdfile_print,
+    .make_new = fdfile_make_new,
+    .getiter = NULL,
+    .iternext = NULL,
+    .stream_p = {
+        .read = fdfile_read,
+        .write = fdfile_write,
+    },
+    .methods = rawfile_type_methods,
+};
+
+// Factory function for I/O stream classes
+mp_obj_t mp_builtin_open(int n_args, const mp_obj_t *args) {
+    // TODO: analyze mode and buffering args and instantiate appropriate type
+    return fdfile_make_new((mp_obj_t)&rawfile_type, n_args, args);
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_builtin_open_obj, 1, 2, mp_builtin_open);

unix/main.c

@@ -20,6 +20,8 @@
 #include <readline/history.h>
 #endif
 
+extern const mp_obj_fun_native_t mp_builtin_open_obj;
+
 static void execute_from_lexer(mp_lexer_t *lex, mp_parse_input_kind_t input_kind, bool is_repl) {
     if (lex == NULL) {
         return;
@@ -206,6 +208,7 @@ int main(int argc, char **argv) {
     rt_init();
 
     rt_store_name(qstr_from_str_static("test"), test_obj_new(42));
+    rt_store_name(qstr_from_str_static("open"), (mp_obj_t)&mp_builtin_open_obj);
 
     /*
     printf("bytes:\n");