support builtin features with Ruby and C.

Support loading builtin features written in Ruby, which implement
with C builtin functions.
[Feature #16254]

Several features:

(1) Load .rb file at boottime with native binary.

Now, prelude.rb is loaded at boottime. However, this file is contained
into the interpreter as a text format and we need to compile it.
This patch contains a feature to load from binary format.

(2) __builtin_func() in Ruby call func() written in C.

In Ruby file, we can write `__builtin_func()` like method call.
However this is not a method call, but special syntax to call
a function `func()` written in C. C functions should be defined
in a file (same compile unit) which load this .rb file.

Functions (`func` in above example) should be defined with
  (a) 1st parameter: rb_execution_context_t *ec
  (b) rest parameters (0 to 15).
  (c) VALUE return type.
This is very similar requirements for functions used by
rb_define_method(), however `rb_execution_context_t *ec`
is new requirement.

(3) automatic C code generation from .rb files.

tool/mk_builtin_loader.rb creates a C code to load .rb files
needed by miniruby and ruby command. This script is run by
BASERUBY, so *.rb should be written in BASERUBY compatbile
syntax. This script load a .rb file and find all of __builtin_
prefix method calls, and generate a part of C code to export
functions.

tool/mk_builtin_binary.rb creates a C code which contains
binary compiled Ruby files needed by ruby command.

1 files changed, 89 insertions, 0 deletions

diff --git a/mini_builtin.c b/mini_builtin.c
new file mode 100644
index 0000000000..d19f9da4c5
--- /dev/null
+++ b/mini_builtin.c
@@ -0,0 +1,89 @@
+#include "internal.h"
+#include "vm_core.h"
+#include "iseq.h"
+#include "builtin.h"
+
+// include from miniinits.c
+
+static const char *
+read_file(const char *fname, size_t *psize)
+{
+    struct stat st;
+    char *code;
+    FILE *fp;
+
+    if (stat(fname, &st) != 0) {
+        rb_bug("stat fails: %s", fname);
+    }
+
+    size_t fsize = st.st_size;
+    if ((code = malloc(fsize + 1)) == NULL) {
+        rb_bug("can't allocate memory: %s (%d)", fname, (int)fsize);
+    }
+
+    if ((fp = fopen(fname, "rb")) == NULL) {
+        rb_bug("can't open file: %s", fname);
+    }
+
+    size_t read_size = fread(code, 1, fsize, fp);
+    if (read_size != fsize) {
+        rb_bug("can't read file enough: %s (expect %d but was %d)", fname, (int)fsize, (int)read_size);
+    }
+
+    code[fsize] = 0;
+    *psize = fsize;
+    return code;
+}
+
+static struct st_table *loaded_builtin_table;
+
+void
+rb_load_with_builtin_functions(const char *feature_name, const char *fname, const struct rb_builtin_function *table)
+{
+    size_t fsize;
+    const char *code = read_file(fname, &fsize);
+    VALUE code_str = rb_utf8_str_new_static(code, fsize);
+    VALUE name_str = rb_sprintf("<internal:%s>", feature_name);
+    rb_obj_hide(code_str);
+
+    rb_ast_t *ast = rb_parser_compile_string_path(rb_parser_new(), name_str, code_str, 1);
+
+    GET_VM()->builtin_function_table = table;
+    const rb_iseq_t *iseq = rb_iseq_new(&ast->body, name_str, name_str, Qnil, NULL, ISEQ_TYPE_TOP);
+    GET_VM()->builtin_function_table = NULL;
+
+    rb_ast_dispose(ast);
+    free((void *)code); // code_str becomes broken.
+
+    // register (loaded iseq will not be freed)
+    st_insert(loaded_builtin_table, (st_data_t)feature_name, (st_data_t)iseq);
+    rb_gc_register_mark_object((VALUE)iseq);
+
+    // eval
+    rb_iseq_eval(iseq);
+}
+
+static int
+each_builtin_i(st_data_t key, st_data_t val, st_data_t dmy)
+{
+    const char *feature = (const char *)key;
+    const rb_iseq_t *iseq = (const rb_iseq_t *)val;
+
+    rb_yield_values(2, rb_str_new2(feature), rb_iseqw_new(iseq));
+
+    return ST_CONTINUE;
+}
+
+static VALUE
+each_builtin(VALUE self)
+{
+    st_foreach(loaded_builtin_table, each_builtin_i, 0);
+    return Qnil;
+}
+
+void
+Init_builtin(void)
+{
+    rb_define_singleton_method(rb_cRubyVM, "each_builtin", each_builtin, 0);
+    loaded_builtin_table = st_init_strtable();
+}