Broken site based impl

lib/rt/core.h

@@ -0,0 +1,95 @@
+// Values and objects: the types that every other part uses, the object
+// header and its tags, the allocator and errors. See docs/model.md
+#pragma once
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+typedef struct { char _; } undefined_t;
+typedef struct { char _; } null_t;
+
+// A string: UTF-16 code units, as JS counts them
+typedef struct jsrt_string *string_t;
+
+// The start of every object: the site that created it, which tells its shape
+// and, for a fn, its code
+typedef struct { uint32_t site; } jsrt_header;
+
+// The sites below 3 are tags. An object of a value shape is a struct, not a
+// pointer, so its header tells if it is undefined, null or absent instead
+#define JSRT_SITE_UNDEFINED 0
+#define JSRT_SITE_NULL 1
+#define JSRT_SITE_ABSENT 2
+
+// A pointer to an object or a string can also be one of these. NULL is null
+extern jsrt_header jsrt_undefined_cell, jsrt_absent_cell;
+#define JSRT_UNDEFINED ((void *)&jsrt_undefined_cell)
+#define JSRT_ABSENT ((void *)&jsrt_absent_cell)   // a field that an object lacks
+
+// Whether the objects of each site are fns, by site. The emitted C defines it
+extern const bool jsrt_fn_sites[];
+
+// A new heap cell of `size` bytes, all zero
+void *jsrt_alloc(size_t size);
+
+// `items`, an array's elements of `size` bytes each, with room for at least
+// `need` of them. `*cap` is the room that it has, and is set to the new room
+void *jsrt_grow(void *items, int32_t *cap, int32_t need, size_t size);
+
+// Throws a TypeError. Exceptions are not supported yet, so it stops the program
+_Noreturn void jsrt_type_error(void);
+
+// `p`, a pointer to an object or a string. A sentinel for null, undefined or
+// absent throws a TypeError
+void *jsrt_some(void *p);
+
+#ifdef JSRT_IMPLEMENTATION
+#include <stdio.h>
+#include <stdlib.h>
+
+jsrt_header jsrt_undefined_cell = { JSRT_SITE_UNDEFINED };
+jsrt_header jsrt_absent_cell = { JSRT_SITE_ABSENT };
+
+void *jsrt_alloc(size_t size) {
+    void *p = calloc(1, size);
+
+    if (!p) {
+        fputs("jsrt: out of memory\n", stderr);
+        abort();
+    }
+
+    return p;
+}
+
+void *jsrt_grow(void *items, int32_t *cap, int32_t need, size_t size) {
+    if (need <= *cap) {
+        return items;
+    }
+
+    int32_t room = *cap * 2 > need ? *cap * 2 : need < 4 ? 4 : need;
+    items = realloc(items, (size_t)room * size);
+
+    if (!items) {
+        fputs("jsrt: out of memory\n", stderr);
+        abort();
+    }
+
+    *cap = room;
+    return items;
+}
+
+_Noreturn void jsrt_type_error(void) {
+    fputs("TypeError\n", stderr);
+    exit(1);
+}
+
+void *jsrt_some(void *p) {
+    if (p == NULL || p == JSRT_UNDEFINED || p == JSRT_ABSENT) {
+        jsrt_type_error();
+    }
+
+    return p;
+}
+
+#endif // JSRT_IMPLEMENTATION