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