100 lines
2.1 KiB
ReStructuredText
100 lines
2.1 KiB
ReStructuredText
C API
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=====
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You can write Picrin's extension by yourself from both sides of C and Scheme. This page describes the way to control the interpreter from the C world.
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Extension Library
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-----------------
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If you want to create a contribution library with C, the only thing you need to do is make a directory under contrib/. Below is a sample code of extension library.
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* contrib/add/nitro.mk
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.. sourcecode:: cmake
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CONTRIB_INITS += add
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CONTRIB_SRCS += contrib/add/add.c
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* contrib/add/add.c
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.. sourcecode:: c
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#include "picrin.h"
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static pic_value
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pic_add(pic_state *pic)
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{
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double a, b;
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pic_get_args(pic, "ff", &a, &b);
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return pic_float_value(pic, a + b);
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}
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void
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pic_init_add(pic_state *pic)
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{
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pic_deflibrary (pic, "(picrin add)") {
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pic_defun(pic, "add", pic_add);
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}
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}
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After recompiling the interpreter, the library "(picrin add)" is available in the REPL, which library provides a funciton "add".
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User-data vs GC
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^^^^^^^^^^^^^^^
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When you use dynamic memory allocation inside C APIs, you must be caseful about Picrin's GC. Fortunately, we provides a set of wrapper functions for complete abstraction of GC. In the case below, the memory (de)allocators *create_foo* and *finalize_foo* are wrapped in pic_data object, so that when an instance of foo losts all references from others to it picrin can automatically finalize the orphan object.
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.. sourcecode:: c
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/** foo.c **/
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#include <stdlib.h>
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#include "picrin.h"
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/*
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* C-side API
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*/
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struct foo {
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// blah blah blah
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};
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struct foo *
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create_foo ()
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{
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return malloc(sizeof(struct foo));
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}
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void
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finalize_foo (void *foo) {
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struct foo *f = foo;
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free(f);
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}
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/*
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* picrin-side FFI interface
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*/
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static const pic_data_type foo_type = { "foo", finalize_foo };
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static pic_value
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pic_create_foo(pic_state *pic)
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{
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struct foo *f;
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pic_get_args(pic, ""); // no args here
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f = create_foo();
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return pic_data_value(pic, md, &foo_type);
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}
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void
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pic_init_foo(pic_state *pic)
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{
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pic_defun(pic, "create-foo", pic_create_foo); // (create-foo)
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}
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