Add an apps directory, and a json_parse program to parse an input file and report on memory usage.

This is intended to provide a way, during development, to test out the memory
and performance impacts of a change.

apps/json_parse.c

@@ -0,0 +1,175 @@
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <getopt.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "config.h"
+#include "json_object.h"
+#include "json_tokener.h"
+#include "json_util.h"
+
+#ifdef HAVE_SYS_RESOURCE_H
+#include <sys/resource.h>
+#include <sys/time.h>
+#endif
+
+static int formatted_output = 0;
+static int show_output = 1;
+static int strict_mode = 0;
+static const char *fname = NULL;
+
+static void usage(int exitval, const char *errmsg);
+static void showmem(void);
+static int parseit(int fd, int (*callback)(struct json_object *));
+static int showobj(struct json_object *new_obj);
+
+static void showmem(void)
+{
+#ifdef HAVE_GETRUSAGE
+	struct rusage rusage;
+	memset(&rusage, 0, sizeof(rusage));
+	getrusage(RUSAGE_SELF, &rusage);
+	printf("maxrss: %d KB\n", rusage.ru_maxrss);
+#endif
+}
+
+static int parseit(int fd, int (*callback)(struct json_object *))
+{
+	struct json_object *obj;
+	char buf[32768];
+	int ret;
+	int depth = JSON_TOKENER_DEFAULT_DEPTH;
+	json_tokener *tok;
+
+	tok = json_tokener_new_ex(depth);
+	if (!tok)
+	{
+		fprintf(stderr, "unable to allocate json_tokener: %s\n", strerror(errno));
+		return 1;
+	}
+	json_tokener_set_flags(tok, JSON_TOKENER_STRICT | JSON_TOKENER_ALLOW_TRAILING_CHARS);
+
+	// XXX push this into some kind of json_tokener_parse_fd API?
+	//  json_object_from_fd isn't flexible enough, and mirroring
+	//   everything you can do with a tokener into json_util.c seems
+	//   like the wrong approach.
+	size_t total_read = 0;
+	while ((ret = read(fd, buf, sizeof(buf))) > 0)
+	{
+		total_read += ret;
+		int start_pos = 0;
+		while (start_pos != ret)
+		{
+			obj = json_tokener_parse_ex(tok, &buf[start_pos], ret - start_pos);
+			enum json_tokener_error jerr = json_tokener_get_error(tok);
+			int parse_end = json_tokener_get_parse_end(tok);
+			if (obj == NULL && jerr != json_tokener_continue)
+			{
+				char *aterr = &buf[start_pos + parse_end];
+				fflush(stdout);
+				int fail_offset = total_read - ret + start_pos + parse_end;
+				fprintf(stderr, "Failed at offset %d: %s %c\n", fail_offset,
+				        json_tokener_error_desc(jerr), aterr[0]);
+				json_tokener_free(tok);
+				return 1;
+			}
+			if (obj != NULL)
+			{
+				int cb_ret = callback(obj);
+				json_object_put(obj);
+				if (cb_ret != 0)
+				{
+					json_tokener_free(tok);
+					return 1;
+				}
+			}
+			start_pos += json_tokener_get_parse_end(tok);
+			assert(start_pos <= ret);
+		}
+	}
+	if (ret < 0)
+	{
+		fprintf(stderr, "error reading fd %d: %s\n", fd, strerror(errno));
+	}
+
+	json_tokener_free(tok);
+	return 0;
+}
+
+static int showobj(struct json_object *new_obj)
+{
+	if (new_obj == NULL)
+	{
+		fprintf(stderr, "%s: Failed to parse\n", fname);
+		return 1;
+	}
+
+	printf("Successfully parsed object from %s\n", fname);
+
+	if (show_output)
+	{
+		const char *output;
+		if (formatted_output)
+			output = json_object_to_json_string(new_obj);
+		else
+			output = json_object_to_json_string_ext(new_obj, JSON_C_TO_STRING_PRETTY);
+		printf("%s\n", output);
+	}
+
+	showmem();
+	return 0;
+}
+
+static void usage(int exitval, const char *errmsg)
+{
+	FILE *fp = stdout;
+	if (exitval != 0)
+		fp = stderr;
+	if (errmsg != NULL)
+		fprintf(fp, "ERROR: %s\n\n", errmsg);
+	fprintf(fp, "Usage: %s [-f] [-n] [-s]\n");
+	fprintf(fp, "  -f - Format the output with JSON_C_TO_STRING_PRETTY\n");
+	fprintf(fp, "  -n - No output\n");
+	fprintf(fp, "  -s - Parse in strict mode, flags:\n");
+	fprintf(fp, "       JSON_TOKENER_STRICT|JSON_TOKENER_ALLOW_TRAILING_CHARS\n");
+
+	fprintf(fp, "\nWARNING WARNING WARNING\n");
+	fprintf(fp, "This is a prototype, it may change or be removed at any time!\n");
+	exit(exitval);
+}
+
+int main(int argc, char **argv)
+{
+	json_object *new_obj;
+	int opt;
+
+	while ((opt = getopt(argc, argv, "fns")) != -1)
+	{
+		switch (opt)
+		{
+		case 'f': formatted_output = 1; break;
+		case 'n': show_output = 0; break;
+		case 's': strict_mode = 1; break;
+		default: /* '?' */ fprintf(stderr, "Usage: %s [-f]\n", argv[0]); exit(EXIT_FAILURE);
+		}
+	}
+
+	if (optind >= argc)
+	{
+		fprintf(stderr, "Expected argument after options\n");
+		exit(EXIT_FAILURE);
+	}
+	fname = argv[optind];
+	int fd = open(argv[optind], O_RDONLY, 0);
+	showmem();
+	if (parseit(fd, showobj) != 0)
+		exit(EXIT_FAILURE);
+	showmem();
+
+	exit(EXIT_SUCCESS);
+}