add json_script, a minimalistic JSON based script interpreter

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

1 files changed, 622 insertions, 0 deletions

diff --git a/json_script.c b/json_script.c
new file mode 100644
index 0000000..bc23754
--- /dev/null
+++ b/json_script.c
@@ -0,0 +1,622 @@
+/*
+ * Copyright (C) 2013 Felix Fietkau <nbd@openwrt.org>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+#include <sys/stat.h>
+#include <regex.h>
+
+#include <libubox/avl-cmp.h>
+
+#include "json_script.h"
+
+struct json_call {
+	struct json_script_ctx *ctx;
+	struct blob_attr *vars;
+	unsigned int seq;
+};
+
+struct json_handler {
+	const char *name;
+	int (*cb)(struct json_call *call, struct blob_attr *cur);
+};
+
+static int json_process_expr(struct json_call *call, struct blob_attr *cur);
+static int json_process_cmd(struct json_call *call, struct blob_attr *cur);
+
+struct json_script_file *
+json_script_file_from_blobmsg(const char *name, void *data, int len)
+{
+	struct json_script_file *f;
+	char *new_name;
+	int name_len = 0;
+
+	if (name)
+		name_len = strlen(name) + 1;
+
+	f = calloc_a(sizeof(*f) + len, &new_name, name_len);
+	memcpy(f->data, data, len);
+	if (name)
+		f->avl.key = strcpy(new_name, name);
+
+	return f;
+}
+
+static struct json_script_file *
+json_script_get_file(struct json_script_ctx *ctx, const char *filename)
+{
+	struct json_script_file *f;
+
+	f = avl_find_element(&ctx->files, filename, f, avl);
+	if (f)
+		return f;
+
+	f = ctx->handle_file(ctx, filename);
+	if (!f)
+		return NULL;
+
+	avl_insert(&ctx->files, &f->avl);
+	return f;
+}
+
+static void __json_script_run(struct json_call *call, struct json_script_file *file,
+			      struct blob_attr *context)
+{
+	struct json_script_ctx *ctx = call->ctx;
+
+	if (file->seq == call->seq) {
+		if (context)
+			ctx->handle_error(ctx, "Recursive include", context);
+
+		return;
+	}
+
+	file->seq = call->seq;
+	while (file) {
+		json_process_cmd(call, file->data);
+		file = file->next;
+	}
+}
+
+const char *json_script_find_var(struct json_script_ctx *ctx, struct blob_attr *vars,
+				 const char *name)
+{
+	struct blob_attr *cur;
+	int rem;
+
+	blobmsg_for_each_attr(cur, vars, rem) {
+		if (blobmsg_type(cur) != BLOBMSG_TYPE_STRING)
+			continue;
+
+		if (strcmp(blobmsg_name(cur), name) != 0)
+			continue;
+
+		return blobmsg_data(cur);
+	}
+
+	return ctx->handle_var(ctx, name, vars);
+}
+
+static const char *
+msg_find_var(struct json_call *call, const char *name)
+{
+	return json_script_find_var(call->ctx, call->vars, name);
+}
+
+static void
+json_get_tuple(struct blob_attr *cur, struct blob_attr **tb, int t1, int t2)
+{
+	static struct blobmsg_policy expr_tuple[3] = {
+		{ .type = BLOBMSG_TYPE_STRING },
+		{},
+		{},
+	};
+
+	expr_tuple[1].type = t1;
+	expr_tuple[2].type = t2;
+	blobmsg_parse_array(expr_tuple, 3, tb, blobmsg_data(cur), blobmsg_data_len(cur));
+}
+
+static int handle_if(struct json_call *call, struct blob_attr *expr)
+{
+	struct blob_attr *tb[4];
+	int ret;
+
+	static const struct blobmsg_policy if_tuple[4] = {
+		{ .type = BLOBMSG_TYPE_STRING },
+		{ .type = BLOBMSG_TYPE_ARRAY },
+		{ .type = BLOBMSG_TYPE_ARRAY },
+		{ .type = BLOBMSG_TYPE_ARRAY },
+	};
+
+	blobmsg_parse_array(if_tuple, 4, tb, blobmsg_data(expr), blobmsg_data_len(expr));
+
+	if (!tb[1] || !tb[2])
+		return 0;
+
+	ret = json_process_expr(call, tb[1]);
+	if (ret < 0)
+		return 0;
+
+	if (ret)
+		return json_process_cmd(call, tb[2]);
+
+	if (!tb[3])
+		return 0;
+
+	return json_process_cmd(call, tb[3]);
+}
+
+static int handle_case(struct json_call *call, struct blob_attr *expr)
+{
+	struct blob_attr *tb[3], *cur;
+	const char *var;
+	int rem;
+
+	json_get_tuple(expr, tb, BLOBMSG_TYPE_STRING, BLOBMSG_TYPE_TABLE);
+	if (!tb[1] || !tb[2])
+		return 0;
+
+	var = msg_find_var(call, blobmsg_data(tb[1]));
+	if (!var)
+		return 0;
+
+	blobmsg_for_each_attr(cur, tb[2], rem) {
+		if (!strcmp(var, blobmsg_name(cur)))
+			return json_process_cmd(call, cur);
+	}
+
+	return 0;
+}
+
+static int handle_return(struct json_call *call, struct blob_attr *expr)
+{
+	return -2;
+}
+
+static int handle_include(struct json_call *call, struct blob_attr *expr)
+{
+	struct blob_attr *tb[3];
+	struct json_script_file *f;
+
+	json_get_tuple(expr, tb, BLOBMSG_TYPE_STRING, 0);
+	if (!tb[1])
+		return 0;
+
+	f = json_script_get_file(call->ctx, blobmsg_data(tb[1]));
+	if (!f)
+		return 0;
+
+	__json_script_run(call, f, expr);
+	return 0;
+}
+
+static const struct json_handler cmd[] = {
+	{ "if", handle_if },
+	{ "case", handle_case },
+	{ "return", handle_return },
+	{ "include", handle_include },
+};
+
+static int eq_regex_cmp(const char *str, const char *pattern, bool regex)
+{
+	regex_t reg;
+	int ret;
+
+	if (!regex)
+		return !strcmp(str, pattern);
+
+	if (regcomp(&reg, pattern, REG_EXTENDED | REG_NOSUB))
+		return 0;
+
+	ret = !regexec(&reg, str, 0, NULL, 0);
+	regfree(&reg);
+
+	return ret;
+}
+
+static int expr_eq_regex(struct json_call *call, struct blob_attr *expr, bool regex)
+{
+	struct json_script_ctx *ctx = call->ctx;
+	struct blob_attr *tb[3], *cur;
+	const char *var;
+	int rem;
+
+	json_get_tuple(expr, tb, BLOBMSG_TYPE_STRING, 0);
+	if (!tb[1] || !tb[2])
+		return -1;
+
+	var = msg_find_var(call, blobmsg_data(tb[1]));
+	if (!var)
+		return 0;
+
+	switch(blobmsg_type(tb[2])) {
+	case BLOBMSG_TYPE_STRING:
+		return eq_regex_cmp(var, blobmsg_data(tb[2]), regex);
+	case BLOBMSG_TYPE_ARRAY:
+		blobmsg_for_each_attr(cur, tb[2], rem) {
+			if (blobmsg_type(cur) != BLOBMSG_TYPE_STRING) {
+				ctx->handle_error(ctx, "Unexpected element type", cur);
+				return -1;
+			}
+
+			if (eq_regex_cmp(var, blobmsg_data(cur), regex))
+				return 1;
+		}
+		return 0;
+	default:
+		ctx->handle_error(ctx, "Unexpected element type", tb[2]);
+		return -1;
+	}
+}
+
+static int handle_expr_eq(struct json_call *call, struct blob_attr *expr)
+{
+	return expr_eq_regex(call, expr, false);
+}
+
+static int handle_expr_regex(struct json_call *call, struct blob_attr *expr)
+{
+	return expr_eq_regex(call, expr, true);
+}
+
+static int handle_expr_has(struct json_call *call, struct blob_attr *expr)
+{
+	struct json_script_ctx *ctx = call->ctx;
+	struct blob_attr *tb[3], *cur;
+	int rem;
+
+	json_get_tuple(expr, tb, 0, 0);
+	if (!tb[1])
+		return -1;
+
+	switch(blobmsg_type(tb[1])) {
+	case BLOBMSG_TYPE_STRING:
+		return !!msg_find_var(call, blobmsg_data(tb[1]));
+	case BLOBMSG_TYPE_ARRAY:
+		blobmsg_for_each_attr(cur, tb[1], rem) {
+			if (blobmsg_type(cur) != BLOBMSG_TYPE_STRING) {
+				ctx->handle_error(ctx, "Unexpected element type", cur);
+				return -1;
+			}
+
+			if (msg_find_var(call, blobmsg_data(cur)))
+				return 1;
+		}
+		return 0;
+	default:
+		ctx->handle_error(ctx, "Unexpected element type", tb[1]);
+		return -1;
+	}
+}
+
+static int expr_and_or(struct json_call *call, struct blob_attr *expr, bool and)
+{
+	struct blob_attr *cur;
+	int ret, rem;
+	int i = 0;
+
+	blobmsg_for_each_attr(cur, expr, rem) {
+		if (i++ < 1)
+			continue;
+
+		ret = json_process_expr(call, cur);
+		if (ret < 0)
+			return ret;
+
+		if (ret != and)
+			return ret;
+	}
+
+	return and;
+}
+
+static int handle_expr_and(struct json_call *call, struct blob_attr *expr)
+{
+	return expr_and_or(call, expr, 1);
+}
+
+static int handle_expr_or(struct json_call *call, struct blob_attr *expr)
+{
+	return expr_and_or(call, expr, 0);
+}
+
+static int handle_expr_not(struct json_call *call, struct blob_attr *expr)
+{
+	struct blob_attr *tb[3];
+
+	json_get_tuple(expr, tb, BLOBMSG_TYPE_ARRAY, 0);
+	if (!tb[1])
+		return -1;
+
+	return json_process_expr(call, tb[1]);
+}
+
+static const struct json_handler expr[] = {
+	{ "eq", handle_expr_eq },
+	{ "regex", handle_expr_regex },
+	{ "has", handle_expr_has },
+	{ "and", handle_expr_and },
+	{ "or", handle_expr_or },
+	{ "not", handle_expr_not },
+};
+
+static int
+__json_process_type(struct json_call *call, struct blob_attr *cur,
+		    const struct json_handler *h, int n, bool *found)
+{
+	const char *name = blobmsg_data(blobmsg_data(cur));
+	int i;
+
+	for (i = 0; i < n; i++) {
+		if (strcmp(name, h[i].name) != 0)
+			continue;
+
+		*found = true;
+		return h[i].cb(call, cur);
+	}
+
+	*found = false;
+	return -1;
+}
+
+static int json_process_expr(struct json_call *call, struct blob_attr *cur)
+{
+	struct json_script_ctx *ctx = call->ctx;
+	bool found;
+	int ret;
+
+	if (blobmsg_type(cur) != BLOBMSG_TYPE_ARRAY ||
+	    blobmsg_type(blobmsg_data(cur)) != BLOBMSG_TYPE_STRING) {
+		ctx->handle_error(ctx, "Unexpected element type", cur);
+		return -1;
+	}
+
+	ret = __json_process_type(call, cur, expr, ARRAY_SIZE(expr), &found);
+	if (!found)
+		ctx->handle_error(ctx, "Unknown expression type", cur);
+
+	return ret;
+}
+
+static int cmd_add_string(struct json_call *call, const char *pattern)
+{
+	struct json_script_ctx *ctx = call->ctx;
+	char *dest, *next, *str;
+	int len = 0;
+	bool var = false;
+	char c = '%';
+
+	dest = blobmsg_alloc_string_buffer(&ctx->buf, NULL, 1);
+	next = alloca(strlen(pattern) + 1);
+	strcpy(next, pattern);
+
+	for (str = next; str; str = next) {
+		const char *cur;
+		char *end;
+		int cur_len = 0;
+		bool cur_var = var;
+
+		end = strchr(str, '%');
+		if (end) {
+			*end = 0;
+			next = end + 1;
+			var = !var;
+		} else {
+			end = str + strlen(str);
+			next = NULL;
+		}
+
+		if (cur_var) {
+			if (next > str) {
+				cur = msg_find_var(call, str);
+				if (!cur)
+					continue;
+
+				cur_len = strlen(cur);
+			} else {
+				cur = &c;
+				cur_len = 1;
+			}
+		} else {
+			if (str == end)
+				continue;
+
+			cur = str;
+			cur_len = end - str;
+		}
+
+		dest = blobmsg_realloc_string_buffer(&ctx->buf, cur_len + 1);
+		memcpy(dest + len, cur, cur_len);
+		len += cur_len;
+	}
+
+	if (var)
+		return -1;
+
+	dest[len] = 0;
+	blobmsg_add_string_buffer(&ctx->buf);
+	return 0;
+}
+
+static int cmd_process_strings(struct json_call *call, struct blob_attr *attr)
+{
+	struct json_script_ctx *ctx = call->ctx;
+	struct blob_attr *cur;
+	int args = -1;
+	int rem, ret;
+	void *c;
+
+	blob_buf_init(&ctx->buf, 0);
+	c = blobmsg_open_array(&ctx->buf, NULL);
+	blobmsg_for_each_attr(cur, attr, rem) {
+		if (args++ < 0)
+			continue;
+
+		if (blobmsg_type(cur) != BLOBMSG_TYPE_STRING) {
+			ctx->handle_error(ctx, "Invalid argument in command", attr);
+			return -1;
+		}
+
+		ret = cmd_add_string(call, blobmsg_data(cur));
+		if (ret) {
+			ctx->handle_error(ctx, "Unterminated variable reference in string", attr);
+			return ret;
+		}
+	}
+
+	blobmsg_close_array(&ctx->buf, c);
+
+	return 0;
+}
+
+static int __json_process_cmd(struct json_call *call, struct blob_attr *cur)
+{
+	struct json_script_ctx *ctx = call->ctx;
+	const char *name;
+	bool found;
+	int ret;
+
+	if (blobmsg_type(cur) != BLOBMSG_TYPE_ARRAY ||
+	    blobmsg_type(blobmsg_data(cur)) != BLOBMSG_TYPE_STRING) {
+		ctx->handle_error(ctx, "Unexpected element type", cur);
+		return -1;
+	}
+
+	ret = __json_process_type(call, cur, cmd, ARRAY_SIZE(cmd), &found);
+	if (found)
+		return ret;
+
+	name = blobmsg_data(blobmsg_data(cur));
+	ret = cmd_process_strings(call, cur);
+	if (ret)
+		return ret;
+
+	ctx->handle_command(ctx, name, blob_data(ctx->buf.head), call->vars);
+
+	return 0;
+}
+
+static int json_process_cmd(struct json_call *call, struct blob_attr *block)
+{
+	struct json_script_ctx *ctx = call->ctx;
+	struct blob_attr *cur;
+	int rem;
+	int ret;
+	int i = 0;
+
+	if (blobmsg_type(block) != BLOBMSG_TYPE_ARRAY) {
+		ctx->handle_error(ctx, "Unexpected element type", block);
+		return -1;
+	}
+
+	blobmsg_for_each_attr(cur, block, rem) {
+		switch(blobmsg_type(cur)) {
+		case BLOBMSG_TYPE_STRING:
+			if (!i)
+				return __json_process_cmd(call, block);
+		default:
+			ret = json_process_cmd(call, cur);
+			if (ret < -1)
+				return ret;
+			break;
+		}
+		i++;
+	}
+
+	return 0;
+}
+
+void json_script_run(struct json_script_ctx *ctx, const char *name,
+		     struct blob_attr *vars)
+{
+	struct json_script_file *file;
+	static unsigned int _seq = 0;
+	struct json_call call = {
+		.ctx = ctx,
+		.vars = vars,
+		.seq = ++_seq,
+	};
+
+	/* overflow */
+	if (!call.seq)
+		call.seq = ++_seq;
+
+	file = json_script_get_file(ctx, name);
+	if (!file)
+		return;
+
+	__json_script_run(&call, file, NULL);
+}
+
+static void __json_script_file_free(struct json_script_ctx *ctx, struct json_script_file *f)
+{
+	struct json_script_file *next;
+
+	for (next = f->next; f; f = next, next = f->next)
+		free(f);
+}
+
+void
+json_script_free(struct json_script_ctx *ctx)
+{
+	struct json_script_file *f, *next;
+
+	avl_remove_all_elements(&ctx->files, f, avl, next)
+		__json_script_file_free(ctx, f);
+
+	blob_buf_free(&ctx->buf);
+}
+
+static void
+__default_handle_error(struct json_script_ctx *ctx, const char *msg,
+		       struct blob_attr *context)
+{
+}
+
+static const char *
+__default_handle_var(struct json_script_ctx *ctx, const char *name,
+		     struct blob_attr *vars)
+{
+	return NULL;
+}
+
+static int
+__default_handle_expr(struct json_script_ctx *ctx, const char *name,
+		      struct blob_attr *expr, struct blob_attr *vars)
+{
+	return -1;
+}
+
+static struct json_script_file *
+__default_handle_file(struct json_script_ctx *ctx, const char *name)
+{
+	return NULL;
+}
+
+void json_script_init(struct json_script_ctx *ctx)
+{
+	avl_init(&ctx->files, avl_strcmp, false, NULL);
+
+	if (!ctx->handle_error)
+		ctx->handle_error = __default_handle_error;
+
+	if (!ctx->handle_var)
+		ctx->handle_var = __default_handle_var;
+
+	if (!ctx->handle_expr)
+		ctx->handle_expr = __default_handle_expr;
+
+	if (!ctx->handle_file)
+		ctx->handle_file = __default_handle_file;
+}