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-rw-r--r--json_writer.c391
1 files changed, 391 insertions, 0 deletions
diff --git a/json_writer.c b/json_writer.c
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index 0000000..e8b3926
--- /dev/null
+++ b/json_writer.c
@@ -0,0 +1,391 @@
+// SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) //
+/*
+ * Simple streaming JSON writer
+ *
+ * This takes care of the annoying bits of JSON syntax like the commas
+ * after elements
+ *
+ * Authors: Stephen Hemminger <stephen@networkplumber.org>
+ */
+
+#include <stdio.h>
+#include <stdbool.h>
+#include <stdarg.h>
+#include <assert.h>
+#include <malloc.h>
+#include <inttypes.h>
+#include <stdint.h>
+
+#include "json_writer.h"
+
+struct json_writer {
+ FILE *out; /* output file */
+ unsigned int depth; /* nesting */
+ bool pretty; /* optional whitepace */
+ char sep; /* either nul or comma */
+};
+
+/* indentation for pretty print */
+static void jsonw_indent(json_writer_t *self)
+{
+ unsigned int i;
+
+ for (i = 0; i < self->depth; ++i)
+ fputs(" ", self->out);
+}
+
+/* end current line and indent if pretty printing */
+static void jsonw_eol(json_writer_t *self)
+{
+ if (!self->pretty)
+ return;
+
+ putc('\n', self->out);
+ jsonw_indent(self);
+}
+
+/* If current object is not empty print a comma */
+static void jsonw_eor(json_writer_t *self)
+{
+ if (self->sep != '\0')
+ putc(self->sep, self->out);
+ self->sep = ',';
+}
+
+
+/* Output JSON encoded string */
+/* Handles C escapes, does not do Unicode */
+static void jsonw_puts(json_writer_t *self, const char *str)
+{
+ putc('"', self->out);
+ for (; *str; ++str)
+ switch (*str) {
+ case '\t':
+ fputs("\\t", self->out);
+ break;
+ case '\n':
+ fputs("\\n", self->out);
+ break;
+ case '\r':
+ fputs("\\r", self->out);
+ break;
+ case '\f':
+ fputs("\\f", self->out);
+ break;
+ case '\b':
+ fputs("\\b", self->out);
+ break;
+ case '\\':
+ fputs("\\\\", self->out);
+ break;
+ case '"':
+ fputs("\\\"", self->out);
+ break;
+ case '\'':
+ fputs("\\\'", self->out);
+ break;
+ default:
+ putc(*str, self->out);
+ }
+ putc('"', self->out);
+}
+
+/* Create a new JSON stream */
+json_writer_t *jsonw_new(FILE *f)
+{
+ json_writer_t *self = malloc(sizeof(*self));
+
+ if (self) {
+ self->out = f;
+ self->depth = 0;
+ self->pretty = false;
+ self->sep = '\0';
+ }
+ return self;
+}
+
+/* End output to JSON stream */
+void jsonw_destroy(json_writer_t **self_p)
+{
+ json_writer_t *self = *self_p;
+
+ assert(self->depth == 0);
+ fputs("\n", self->out);
+ fflush(self->out);
+ free(self);
+ *self_p = NULL;
+}
+
+void jsonw_pretty(json_writer_t *self, bool on)
+{
+ self->pretty = on;
+}
+
+/* Basic blocks */
+static void jsonw_begin(json_writer_t *self, int c)
+{
+ jsonw_eor(self);
+ putc(c, self->out);
+ ++self->depth;
+ self->sep = '\0';
+}
+
+static void jsonw_end(json_writer_t *self, int c)
+{
+ assert(self->depth > 0);
+
+ --self->depth;
+ if (self->sep != '\0')
+ jsonw_eol(self);
+ putc(c, self->out);
+ self->sep = ',';
+}
+
+
+/* Add a JSON property name */
+void jsonw_name(json_writer_t *self, const char *name)
+{
+ jsonw_eor(self);
+ jsonw_eol(self);
+ self->sep = '\0';
+ jsonw_puts(self, name);
+ putc(':', self->out);
+ if (self->pretty)
+ putc(' ', self->out);
+}
+
+__attribute__((format(printf, 2, 3)))
+void jsonw_printf(json_writer_t *self, const char *fmt, ...)
+{
+ va_list ap;
+
+ va_start(ap, fmt);
+ jsonw_eor(self);
+ vfprintf(self->out, fmt, ap);
+ va_end(ap);
+}
+
+/* Collections */
+void jsonw_start_object(json_writer_t *self)
+{
+ jsonw_begin(self, '{');
+}
+
+void jsonw_end_object(json_writer_t *self)
+{
+ jsonw_end(self, '}');
+}
+
+void jsonw_start_array(json_writer_t *self)
+{
+ jsonw_begin(self, '[');
+ if (self->pretty)
+ putc(' ', self->out);
+}
+
+void jsonw_end_array(json_writer_t *self)
+{
+ if (self->pretty && self->sep)
+ putc(' ', self->out);
+ self->sep = '\0';
+ jsonw_end(self, ']');
+}
+
+/* JSON value types */
+void jsonw_string(json_writer_t *self, const char *value)
+{
+ jsonw_eor(self);
+ jsonw_puts(self, value);
+}
+
+void jsonw_bool(json_writer_t *self, bool val)
+{
+ jsonw_printf(self, "%s", val ? "true" : "false");
+}
+
+void jsonw_null(json_writer_t *self)
+{
+ jsonw_printf(self, "null");
+}
+
+void jsonw_float(json_writer_t *self, double num)
+{
+ jsonw_printf(self, "%g", num);
+}
+
+void jsonw_hhu(json_writer_t *self, unsigned char num)
+{
+ jsonw_printf(self, "%hhu", num);
+}
+
+void jsonw_hu(json_writer_t *self, unsigned short num)
+{
+ jsonw_printf(self, "%hu", num);
+}
+
+void jsonw_uint(json_writer_t *self, unsigned int num)
+{
+ jsonw_printf(self, "%u", num);
+}
+
+void jsonw_u64(json_writer_t *self, uint64_t num)
+{
+ jsonw_printf(self, "%"PRIu64, num);
+}
+
+void jsonw_xint(json_writer_t *self, uint64_t num)
+{
+ jsonw_printf(self, "%"PRIx64, num);
+}
+
+void jsonw_luint(json_writer_t *self, unsigned long num)
+{
+ jsonw_printf(self, "%lu", num);
+}
+
+void jsonw_lluint(json_writer_t *self, unsigned long long num)
+{
+ jsonw_printf(self, "%llu", num);
+}
+
+void jsonw_int(json_writer_t *self, int num)
+{
+ jsonw_printf(self, "%d", num);
+}
+
+void jsonw_s64(json_writer_t *self, int64_t num)
+{
+ jsonw_printf(self, "%"PRId64, num);
+}
+
+/* Basic name/value objects */
+void jsonw_string_field(json_writer_t *self, const char *prop, const char *val)
+{
+ jsonw_name(self, prop);
+ jsonw_string(self, val);
+}
+
+void jsonw_bool_field(json_writer_t *self, const char *prop, bool val)
+{
+ jsonw_name(self, prop);
+ jsonw_bool(self, val);
+}
+
+void jsonw_float_field(json_writer_t *self, const char *prop, double val)
+{
+ jsonw_name(self, prop);
+ jsonw_float(self, val);
+}
+
+void jsonw_uint_field(json_writer_t *self, const char *prop, unsigned int num)
+{
+ jsonw_name(self, prop);
+ jsonw_uint(self, num);
+}
+
+void jsonw_u64_field(json_writer_t *self, const char *prop, uint64_t num)
+{
+ jsonw_name(self, prop);
+ jsonw_u64(self, num);
+}
+
+void jsonw_xint_field(json_writer_t *self, const char *prop, uint64_t num)
+{
+ jsonw_name(self, prop);
+ jsonw_xint(self, num);
+}
+
+void jsonw_hhu_field(json_writer_t *self, const char *prop, unsigned char num)
+{
+ jsonw_name(self, prop);
+ jsonw_hhu(self, num);
+}
+
+void jsonw_hu_field(json_writer_t *self, const char *prop, unsigned short num)
+{
+ jsonw_name(self, prop);
+ jsonw_hu(self, num);
+}
+
+void jsonw_luint_field(json_writer_t *self,
+ const char *prop,
+ unsigned long num)
+{
+ jsonw_name(self, prop);
+ jsonw_luint(self, num);
+}
+
+void jsonw_lluint_field(json_writer_t *self,
+ const char *prop,
+ unsigned long long num)
+{
+ jsonw_name(self, prop);
+ jsonw_lluint(self, num);
+}
+
+void jsonw_int_field(json_writer_t *self, const char *prop, int num)
+{
+ jsonw_name(self, prop);
+ jsonw_int(self, num);
+}
+
+void jsonw_s64_field(json_writer_t *self, const char *prop, int64_t num)
+{
+ jsonw_name(self, prop);
+ jsonw_s64(self, num);
+}
+
+void jsonw_null_field(json_writer_t *self, const char *prop)
+{
+ jsonw_name(self, prop);
+ jsonw_null(self);
+}
+
+#ifdef TEST
+int main(int argc, char **argv)
+{
+ json_writer_t *wr = jsonw_new(stdout);
+
+ jsonw_start_object(wr);
+ jsonw_pretty(wr, true);
+ jsonw_name(wr, "Vyatta");
+ jsonw_start_object(wr);
+ jsonw_string_field(wr, "url", "http://vyatta.com");
+ jsonw_uint_field(wr, "downloads", 2000000ul);
+ jsonw_float_field(wr, "stock", 8.16);
+
+ jsonw_name(wr, "ARGV");
+ jsonw_start_array(wr);
+ while (--argc)
+ jsonw_string(wr, *++argv);
+ jsonw_end_array(wr);
+
+ jsonw_name(wr, "empty");
+ jsonw_start_array(wr);
+ jsonw_end_array(wr);
+
+ jsonw_name(wr, "NIL");
+ jsonw_start_object(wr);
+ jsonw_end_object(wr);
+
+ jsonw_null_field(wr, "my_null");
+
+ jsonw_name(wr, "special chars");
+ jsonw_start_array(wr);
+ jsonw_string_field(wr, "slash", "/");
+ jsonw_string_field(wr, "newline", "\n");
+ jsonw_string_field(wr, "tab", "\t");
+ jsonw_string_field(wr, "ff", "\f");
+ jsonw_string_field(wr, "quote", "\"");
+ jsonw_string_field(wr, "tick", "\'");
+ jsonw_string_field(wr, "backslash", "\\");
+ jsonw_end_array(wr);
+
+ jsonw_end_object(wr);
+
+ jsonw_end_object(wr);
+ jsonw_destroy(&wr);
+ return 0;
+}
+
+#endif