Implement caching compilation results

Unfortunately they aren't yet reused, but that will come later.

c/ton/main.c

#include <assert.h>
#include <errno.h>
#include <getopt.h>
#include <libgen.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
JSStringRef to_string(JSContextRef ctx, JSValueRef val);
JSValueRef evaluate_script(JSContextRef ctx, char *script, char *source);
char *value_to_c_string(JSContextRef ctx, JSValueRef val);
JSValueRef evaluate_source(JSContextRef ctx, char *type, char *source_value, bool expression, char *set_ns);
char *munge(char *s);
JSObjectRef get_function(JSContextRef ctx, char *namespace, char *name);
char* get_contents(char *path);
void write_contents(char *path, char *contents);
int mkdir_p(char *path);
#ifdef DEBUG
#define debug_print_value(prefix, ctx, val)	print_value(prefix ": ", ctx, val)
	return JSObjectMakeArray(ctx, 0, NULL, NULL);
}
JSValueRef function_cache(JSContextRef ctx, JSObjectRef function, JSObjectRef thisObject,
		size_t argc, const JSValueRef args[], JSValueRef* exception) {
	if (argc == 4 &&
			JSValueGetType (ctx, args[0]) == kJSTypeString &&
			JSValueGetType (ctx, args[1]) == kJSTypeString &&
			(JSValueGetType (ctx, args[2]) == kJSTypeString
				|| JSValueGetType (ctx, args[2]) == kJSTypeNull) &&
			(JSValueGetType (ctx, args[3]) == kJSTypeString
				|| JSValueGetType (ctx, args[3]) == kJSTypeNull)) {
		debug_print_value("cache", ctx, args[0]);
		char *cache_prefix = value_to_c_string(ctx, args[0]);
		char *source = value_to_c_string(ctx, args[1]);
		char *cache = value_to_c_string(ctx, args[2]);
		char *sourcemap = value_to_c_string(ctx, args[3]);
		char *suffix = NULL;
		int max_suffix_len = 20;
		int prefix_len = strlen(cache_prefix);
		char *path = malloc((prefix_len + max_suffix_len) * sizeof(char));
		suffix = ".js";
		strncpy(path, cache_prefix, prefix_len);
		path[prefix_len] = '\0';
		strncat(path, suffix, strlen(suffix));
		write_contents(path, source);
		suffix = ".cache.json";
		strncpy(path, cache_prefix, prefix_len);
		path[prefix_len] = '\0';
		strncat(path, suffix, strlen(suffix));
		write_contents(path, cache);
		suffix = ".js.map.json";
		strncpy(path, cache_prefix, prefix_len);
		path[prefix_len] = '\0';
		strncat(path, suffix, strlen(suffix));
		write_contents(path, sourcemap);
		free(cache_prefix);
		free(source);
		free(cache);
		free(sourcemap);
		free(path);
	}
	return  JSValueMakeNull(ctx);
}
JSValueRef function_eval(JSContextRef ctx, JSObjectRef function, JSObjectRef thisObject,
		size_t argc, const JSValueRef args[], JSValueRef* exception) {
	JSValueRef val = NULL;
	register_global_function(ctx, "PLANCK_READ_FILE", function_read_file);
	register_global_function(ctx, "PLANCK_LOAD", function_load);
	register_global_function(ctx, "PLANCK_LOAD_DEPS_CLJS_FILES", function_load_deps_cljs_files);
	register_global_function(ctx, "PLANCK_CACHE", function_cache);
	register_global_function(ctx, "PLANCK_EVAL", function_eval);
	return val;
}
char *value_to_c_string(JSContextRef ctx, JSValueRef val) {
	if (!JSValueIsString(ctx, val)) {
#ifdef DEBUG
		fprintf(stderr, "WARN: not a string\n");
#endif
		return NULL;
	}
	JSStringRef str_ref = JSValueToStringCopy(ctx, val, NULL);
	size_t len = JSStringGetLength(str_ref);
	char *str = malloc(len * sizeof(char));
	JSStringGetUTF8CString(str_ref, str, len);
	JSStringRelease(str_ref);
	return str;
}
JSValueRef get_value_on_object(JSContextRef ctx, JSObjectRef obj, char *name) {
	JSStringRef name_str = JSStringCreateWithUTF8CString(name);
	JSValueRef val = JSObjectGetProperty(ctx, obj, name_str, NULL);
	printf("get_contents(\"%s\"): %s: %s\n", path, err_prefix, strerror(errno));
	return NULL;
}
void write_contents(char *path, char *contents) {
	char *err_prefix;
	char *path_copy = strdup(path);
	char *dir = dirname(path_copy);
	if (mkdir_p(dir) < 0) {
		err_prefix = "mkdir_p";
		free(path_copy);
		goto err;
	}
	free(path_copy);
	FILE *f = fopen(path, "w");
	if (f == NULL) {
		err_prefix = "fopen";
		goto err;
	}
	int len = strlen(contents);
	int offset = 0;
	do {
		int res = fwrite(contents+offset, 1, len-offset, f);
		if (res < 0) {
			err_prefix = "fwrite";
			goto err;
		}
		offset += res;
	} while (offset < len);
	if (fclose(f) < 0) {
		err_prefix = "fclose";
		goto err;
	}
	return;
err:
	printf("write_contents(\"%s\", ...): %s: %s\n", path, err_prefix, strerror(errno));
	return;
}
int mkdir_p(char *path) {
	int res = mkdir(path, 0755);
	if (res < 0 && errno == EEXIST) {
		return 0;
	}
	return res;
}