common/json_filter: routines for json filtering.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

common/Makefile

@@ -48,6 +48,7 @@ COMMON_SRC_NOGEN :=				\
 	common/initial_channel.c		\
 	common/initial_commit_tx.c		\
 	common/iso4217.c			\
+	common/json_filter.c			\
 	common/json_param.c			\
 	common/json_parse.c			\
 	common/json_parse_simple.c		\

common/json_filter.c

@@ -0,0 +1,192 @@
+#include "config.h"
+#include <assert.h>
+#include <ccan/strmap/strmap.h>
+#include <ccan/tal/str/str.h>
+#include <common/json_filter.h>
+#include <common/utils.h>
+
+/* If they set a filter, we keep it in a tree. */
+struct json_filter {
+	/* We accumulate errors: if they treat an array as an object */
+	bool misused;
+
+	/* Pointer to parent, or NULL at top. */
+	struct json_filter *parent;
+
+	/* Tracks how far we are into filter, e.g.
+	 * if they specify "peers.foo" and we're
+	 * in "peer.foo.bar" depth will be 1. */
+	size_t depth;
+	/* If we're in "peer.bar", we're negative */
+	bool positive;
+
+	/* If this is an array */
+	struct json_filter *filter_array;
+
+	/* Otherwise, object: one per keyword */
+	STRMAP(struct json_filter *) filter_map;
+};
+
+/* Returns true if we should print this member: this is a shortcut for:
+ *
+ *   json_filter_down(filter, member);
+ *   ret = json_filter_ok(filter, NULL);
+ *   json_filter_up(filter);
+ *
+ */
+bool json_filter_ok(const struct json_filter *filter, const char *member)
+{
+	if (!filter)
+		return true;
+	if (filter->depth > 0 || !member)
+		return filter->positive;
+	return strmap_get(&filter->filter_map, member) != NULL;
+}
+
+/* Returns true if we should print this new obj/array */
+bool json_filter_down(struct json_filter **filter, const char *member)
+{
+	struct json_filter *child;
+
+	if (!*filter)
+		return true;
+	if ((*filter)->depth > 0) {
+		(*filter)->depth++;
+		return (*filter)->positive;
+	}
+
+	/* If we're a leaf node: all true. */
+	if (!(*filter)->filter_array && strmap_empty(&(*filter)->filter_map)) {
+		assert((*filter)->positive);
+		(*filter)->depth = 1;
+		return true;
+	}
+
+	/* Array? */
+	if (!member) {
+		if (!(*filter)->filter_array) {
+			(*filter)->misused = true;
+			goto fail;
+		}
+		child = (*filter)->filter_array;
+	} else {
+		if ((*filter)->filter_array) {
+			(*filter)->misused = true;
+			goto fail;
+		}
+		child = strmap_get(&(*filter)->filter_map, member);
+	}
+
+	if (child) {
+		/* Should have been cleaned up last time. */
+		assert(child->depth == 0);
+		/* We only have positive filters natively. */
+		assert(child->positive == true);
+		*filter = child;
+		return true;
+	}
+
+	/* OK, this path wasn't specified. */
+fail:
+	(*filter)->positive = false;
+	(*filter)->depth = 1;
+	return false;
+}
+
+/* Returns true if we were printing (i.e. close object/arr) */
+bool json_filter_up(struct json_filter **filter)
+{
+	if (!*filter)
+		return true;
+
+	if ((*filter)->depth == 0) {
+		assert((*filter)->parent);
+		assert((*filter)->parent->depth == 0);
+		/* Reset for next time */
+		(*filter)->positive = true;
+		*filter = (*filter)->parent;
+		return true;
+	}
+
+	(*filter)->depth--;
+	return (*filter)->positive;
+}
+
+static void destroy_json_filter(struct json_filter *filter)
+{
+	strmap_clear(&filter->filter_map);
+}
+
+struct json_filter *json_filter_new(const tal_t *ctx)
+{
+	struct json_filter *filter = tal(ctx, struct json_filter);
+	filter->misused = false;
+	filter->parent = NULL;
+	filter->depth = 0;
+	filter->positive = true;
+	filter->filter_array = NULL;
+	strmap_init(&filter->filter_map);
+	tal_add_destructor(filter, destroy_json_filter);
+	return filter;
+}
+
+struct json_filter *json_filter_subobj(struct json_filter *filter,
+				       const char *fieldname,
+				       size_t fieldnamelen)
+{
+	struct json_filter *subfilter = json_filter_new(filter);
+	subfilter->parent = filter;
+	strmap_add(&filter->filter_map,
+		   tal_strndup(filter, fieldname, fieldnamelen),
+		   subfilter);
+	return subfilter;
+}
+
+struct json_filter *json_filter_subarr(struct json_filter *filter)
+{
+	struct json_filter *subfilter = json_filter_new(filter);
+	subfilter->parent = filter;
+	filter->filter_array = subfilter;
+	return subfilter;
+}
+
+bool json_filter_finished(const struct json_filter *filter)
+{
+	return !filter->parent && filter->depth == 0;
+}
+
+static bool strmap_filter_misused(const char *member,
+				  struct json_filter *filter,
+				  const char **ret)
+{
+	*ret = json_filter_misused(tmpctx, filter);
+	if (*ret == NULL)
+		return true;
+
+	/* If there was a problem, prepend member and stop iterating */
+	*ret = tal_fmt(tmpctx, ".%s%s", member, *ret);
+	return false;
+}
+
+const char *json_filter_misused(const tal_t *ctx, const struct json_filter *f)
+{
+	const char *ret;
+
+	if (f->misused) {
+		if (f->filter_array)
+			return tal_fmt(ctx, " is an object");
+		else
+			return tal_fmt(ctx, " is an array");
+	}
+
+	if (f->filter_array) {
+		ret = json_filter_misused(tmpctx, f->filter_array);
+		if (ret)
+			return tal_fmt(ctx, "[]%s", ret);
+		return NULL;
+	} else {
+		ret = NULL;
+		strmap_iterate(&f->filter_map, strmap_filter_misused, &ret);
+		return tal_steal(ctx, ret);
+	}
+}

common/json_filter.h

@@ -0,0 +1,34 @@
+/*
+ * Helpers for filtering JSON results while generating.
+ */
+#ifndef LIGHTNING_COMMON_JSON_FILTER_H
+#define LIGHTNING_COMMON_JSON_FILTER_H
+#include "config.h"
+#include <ccan/tal/tal.h>
+#include <stdbool.h>
+
+struct json_filter;
+
+/* Print this? */
+bool json_filter_ok(const struct json_filter *filter, const char *member);
+
+/* Returns true if we should print this new obj/array */
+bool json_filter_down(struct json_filter **filter, const char *member);
+
+/* Returns true if we were printing (i.e. close object/arr) */
+bool json_filter_up(struct json_filter **filter);
+
+/* Is filter finished (i.e. balanced!) */
+bool json_filter_finished(const struct json_filter *filter);
+
+/* Has filter been misused?  If so, returns explanatory string, otherwise NULL */
+const char *json_filter_misused(const tal_t *ctx, const struct json_filter *f);
+
+/* Filter allocation */
+struct json_filter *json_filter_new(const tal_t *ctx);
+struct json_filter *json_filter_subobj(struct json_filter *filter,
+				       const char *fieldname,
+				       size_t fieldnamelen);
+struct json_filter *json_filter_subarr(struct json_filter *filter);
+
+#endif /* LIGHTNING_COMMON_JSON_FILTER_H */

common/test/run-json.c

@@ -4,6 +4,7 @@
 #include <assert.h>
 #include <ccan/tal/str/str.h>
 #include <common/channel_type.h>
+#include <common/json_filter.h>
 #include <common/setup.h>
 #include <inttypes.h>
 #include <stdio.h>
@@ -17,6 +18,18 @@ bool fromwire_tlv(const u8 **cursor UNNEEDED, size_t *max UNNEEDED,
 		  void *record UNNEEDED, struct tlv_field **fields UNNEEDED,
 		  const u64 *extra_types UNNEEDED, size_t *err_off UNNEEDED, u64 *err_type UNNEEDED)
 { fprintf(stderr, "fromwire_tlv called!\n"); abort(); }
+/* Generated stub for json_filter_down */
+bool json_filter_down(struct json_filter **filter UNNEEDED, const char *member UNNEEDED)
+{ fprintf(stderr, "json_filter_down called!\n"); abort(); }
+/* Generated stub for json_filter_finished */
+bool json_filter_finished(const struct json_filter *filter UNNEEDED)
+{ fprintf(stderr, "json_filter_finished called!\n"); abort(); }
+/* Generated stub for json_filter_ok */
+bool json_filter_ok(const struct json_filter *filter UNNEEDED, const char *member UNNEEDED)
+{ fprintf(stderr, "json_filter_ok called!\n"); abort(); }
+/* Generated stub for json_filter_up */
+bool json_filter_up(struct json_filter **filter UNNEEDED)
+{ fprintf(stderr, "json_filter_up called!\n"); abort(); }
 /* Generated stub for towire_tlv */
 void towire_tlv(u8 **pptr UNNEEDED,
 		const struct tlv_record_type *types UNNEEDED, size_t num_types UNNEEDED,

lightningd/test/run-jsonrpc.c

@@ -1,4 +1,5 @@
 #include "config.h"
+#include "../../common/json_filter.c"
 #include "../../common/json_stream.c"
 #include "../jsonrpc.c"
 #include "../feerate.c"

plugins/Makefile

@@ -140,6 +140,7 @@ PLUGIN_COMMON_OBJS :=				\
 	common/json_param.o			\
 	common/json_parse.o			\
 	common/json_parse_simple.o		\
+	common/json_filter.o			\
 	common/json_stream.o			\
 	common/lease_rates.o			\
 	common/memleak.o			\