Boot core library from image rather than source

This should speed up start time and reduce malloc/free
usage to about 15% of what is what previously for startup.
The current cost is slightly larger binary as the representaion
of the image is currently less compact than source code.

src/boot/boot.c

@@ -0,0 +1,43 @@
+/*
+* Copyright (c) 2019 Calvin Rose
+*
+* Permission is hereby granted, free of charge, to any person obtaining a copy
+* of this software and associated documentation files (the "Software"), to
+* deal in the Software without restriction, including without limitation the
+* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+* sell copies of the Software, and to permit persons to whom the Software is
+* furnished to do so, subject to the following conditions:
+*
+* The above copyright notice and this permission notice shall be included in
+* all copies or substantial portions of the Software.
+*
+* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+* IN THE SOFTWARE.
+*/
+
+#include <janet/janet.h>
+
+extern const unsigned char *janet_gen_boot;
+extern int32_t janet_gen_boot_size;
+
+int main() {
+    int status;
+    JanetTable *env;
+
+    /* Set up VM */
+    janet_init();
+    env = janet_core_env();
+
+    /* Run bootstrap script to generate core image */
+    status = janet_dobytes(env, janet_gen_boot, janet_gen_boot_size, "boot.janet", NULL);
+
+    /* Deinitialize vm */
+    janet_deinit();
+
+    return status;
+}

src/boot/boot.janet

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+# Copyright (C) Calvin Rose 2019
+
+# The bootstrap script is used to produce the source file for
+# embedding the core image.
+
+# Tool to dump a marshalled version of the janet core to stdout. The
+# image should eventually allow janet to be started from a pre-compiled
+# image rather than recompiled every time from the embedded source. More
+# work will go into shrinking the image (it isn't currently that large but
+# could be smaller), creating the mechanism to load the image, and modifying
+# the build process to compile janet with a built image rather than
+# embedded source.
+
+# Get image. This image contains as much of the core library and documentation that
+# can be written to an image (no cfunctions, no abstracts (stdout, stdin, stderr)),
+# everything else goes. Cfunctions and abstracts will be referenced from a registry
+# table which will be generated on janet startup.
+(do
+  (def image (let [env-pairs (pairs (env-lookup *env*))
+                   essential-pairs (filter (fn [[k v]] (or (cfunction? v) (abstract? v))) env-pairs)
+                   lookup (table ;(mapcat identity essential-pairs))
+                   reverse-lookup (invert lookup)]
+               (marshal *env* reverse-lookup)))
+
+  # Create C source file that contains images a uint8_t buffer. This
+  # can be compiled and linked statically into the main janet library
+  # and example client.
+  (def chunks (seq [b :in image] (string b)))
+  (def image-file (file/open "build/core_image.c" :w))
+  (file/write image-file
+              "#include <janet/janet.h>\n"
+              "static const unsigned char janet_core_image_bytes[] = {")
+  (loop [line :in (partition 16 chunks)]
+    (def str (string ;(interpose ", " line)))
+    (file/write image-file str ",\n"))
+  (file/write image-file
+              "0};\n\n"
+              "const unsigned char *janet_core_image = janet_core_image_bytes;\n"
+              "size_t janet_core_image_size = sizeof(janet_core_image_bytes);\n")
+  (file/close image-file))