357 lines
6.8 KiB
C
357 lines
6.8 KiB
C
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/*
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* Simple streaming JSON writer
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*
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* This takes care of the annoying bits of JSON syntax like the commas
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* after elements
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* Authors: Stephen Hemminger <stephen@networkplumber.org>
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*/
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#include <stdio.h>
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#include <stdbool.h>
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#include <stdarg.h>
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#include <assert.h>
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#include <malloc.h>
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#include <inttypes.h>
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#include <stdint.h>
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#include "json_writer.h"
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struct json_writer {
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FILE *out; /* output file */
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unsigned depth; /* nesting */
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bool pretty; /* optional whitepace */
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char sep; /* either nul or comma */
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};
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/* indentation for pretty print */
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static void jsonw_indent(json_writer_t *self)
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{
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unsigned i;
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for (i = 0; i < self->depth; ++i)
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fputs(" ", self->out);
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}
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/* end current line and indent if pretty printing */
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static void jsonw_eol(json_writer_t *self)
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{
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if (!self->pretty)
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return;
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putc('\n', self->out);
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jsonw_indent(self);
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}
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/* If current object is not empty print a comma */
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static void jsonw_eor(json_writer_t *self)
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{
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if (self->sep != '\0')
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putc(self->sep, self->out);
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self->sep = ',';
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}
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/* Output JSON encoded string */
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/* Handles C escapes, does not do Unicode */
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static void jsonw_puts(json_writer_t *self, const char *str)
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{
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putc('"', self->out);
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for (; *str; ++str)
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switch (*str) {
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case '\t':
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fputs("\\t", self->out);
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break;
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case '\n':
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fputs("\\n", self->out);
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break;
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case '\r':
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fputs("\\r", self->out);
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break;
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case '\f':
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fputs("\\f", self->out);
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break;
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case '\b':
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fputs("\\b", self->out);
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break;
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case '\\':
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fputs("\\n", self->out);
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break;
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case '"':
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fputs("\\\"", self->out);
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break;
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case '\'':
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fputs("\\\'", self->out);
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break;
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default:
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putc(*str, self->out);
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}
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putc('"', self->out);
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}
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/* Create a new JSON stream */
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json_writer_t *jsonw_new(FILE *f)
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{
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json_writer_t *self = malloc(sizeof(*self));
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if (self) {
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self->out = f;
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self->depth = 0;
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self->pretty = false;
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self->sep = '\0';
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}
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return self;
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}
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/* End output to JSON stream */
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void jsonw_destroy(json_writer_t **self_p)
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{
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json_writer_t *self = *self_p;
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assert(self->depth == 0);
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fputs("\n", self->out);
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fflush(self->out);
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free(self);
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*self_p = NULL;
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}
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void jsonw_pretty(json_writer_t *self, bool on)
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{
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self->pretty = on;
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}
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/* Basic blocks */
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static void jsonw_begin(json_writer_t *self, int c)
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{
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jsonw_eor(self);
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putc(c, self->out);
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++self->depth;
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self->sep = '\0';
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}
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static void jsonw_end(json_writer_t *self, int c)
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{
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assert(self->depth > 0);
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--self->depth;
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if (self->sep != '\0')
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jsonw_eol(self);
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putc(c, self->out);
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self->sep = ',';
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}
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/* Add a JSON property name */
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void jsonw_name(json_writer_t *self, const char *name)
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{
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jsonw_eor(self);
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jsonw_eol(self);
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self->sep = '\0';
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jsonw_puts(self, name);
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putc(':', self->out);
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if (self->pretty)
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putc(' ', self->out);
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}
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void jsonw_vprintf_enquote(json_writer_t *self, const char *fmt, va_list ap)
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{
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jsonw_eor(self);
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putc('"', self->out);
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vfprintf(self->out, fmt, ap);
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putc('"', self->out);
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}
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void jsonw_printf(json_writer_t *self, const char *fmt, ...)
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{
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va_list ap;
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va_start(ap, fmt);
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jsonw_eor(self);
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vfprintf(self->out, fmt, ap);
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va_end(ap);
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}
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/* Collections */
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void jsonw_start_object(json_writer_t *self)
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{
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jsonw_begin(self, '{');
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}
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void jsonw_end_object(json_writer_t *self)
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{
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jsonw_end(self, '}');
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}
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void jsonw_start_array(json_writer_t *self)
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{
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jsonw_begin(self, '[');
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}
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void jsonw_end_array(json_writer_t *self)
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{
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jsonw_end(self, ']');
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}
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/* JSON value types */
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void jsonw_string(json_writer_t *self, const char *value)
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{
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jsonw_eor(self);
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jsonw_puts(self, value);
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}
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void jsonw_bool(json_writer_t *self, bool val)
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{
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jsonw_printf(self, "%s", val ? "true" : "false");
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}
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void jsonw_null(json_writer_t *self)
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{
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jsonw_printf(self, "null");
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}
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void jsonw_float_fmt(json_writer_t *self, const char *fmt, double num)
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{
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jsonw_printf(self, fmt, num);
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}
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#ifdef notused
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void jsonw_float(json_writer_t *self, double num)
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{
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jsonw_printf(self, "%g", num);
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}
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#endif
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void jsonw_hu(json_writer_t *self, unsigned short num)
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{
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jsonw_printf(self, "%hu", num);
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}
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void jsonw_uint(json_writer_t *self, uint64_t num)
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{
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jsonw_printf(self, "%"PRIu64, num);
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}
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void jsonw_lluint(json_writer_t *self, unsigned long long int num)
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{
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jsonw_printf(self, "%llu", num);
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}
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void jsonw_int(json_writer_t *self, int64_t num)
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{
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jsonw_printf(self, "%"PRId64, num);
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}
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/* Basic name/value objects */
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void jsonw_string_field(json_writer_t *self, const char *prop, const char *val)
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{
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jsonw_name(self, prop);
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jsonw_string(self, val);
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}
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void jsonw_bool_field(json_writer_t *self, const char *prop, bool val)
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{
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jsonw_name(self, prop);
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jsonw_bool(self, val);
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}
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#ifdef notused
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void jsonw_float_field(json_writer_t *self, const char *prop, double val)
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{
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jsonw_name(self, prop);
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jsonw_float(self, val);
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}
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#endif
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void jsonw_float_field_fmt(json_writer_t *self,
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const char *prop,
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const char *fmt,
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double val)
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{
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jsonw_name(self, prop);
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jsonw_float_fmt(self, fmt, val);
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}
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void jsonw_uint_field(json_writer_t *self, const char *prop, uint64_t num)
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{
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jsonw_name(self, prop);
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jsonw_uint(self, num);
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}
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void jsonw_hu_field(json_writer_t *self, const char *prop, unsigned short num)
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{
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jsonw_name(self, prop);
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jsonw_hu(self, num);
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}
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void jsonw_lluint_field(json_writer_t *self,
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const char *prop,
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unsigned long long int num)
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{
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jsonw_name(self, prop);
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jsonw_lluint(self, num);
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}
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void jsonw_int_field(json_writer_t *self, const char *prop, int64_t num)
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{
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jsonw_name(self, prop);
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jsonw_int(self, num);
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}
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void jsonw_null_field(json_writer_t *self, const char *prop)
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{
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jsonw_name(self, prop);
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jsonw_null(self);
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}
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#ifdef TEST
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int main(int argc, char **argv)
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{
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json_writer_t *wr = jsonw_new(stdout);
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jsonw_start_object(wr);
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jsonw_pretty(wr, true);
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jsonw_name(wr, "Vyatta");
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jsonw_start_object(wr);
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jsonw_string_field(wr, "url", "http://vyatta.com");
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jsonw_uint_field(wr, "downloads", 2000000ul);
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jsonw_float_field(wr, "stock", 8.16);
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jsonw_name(wr, "ARGV");
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jsonw_start_array(wr);
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while (--argc)
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jsonw_string(wr, *++argv);
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jsonw_end_array(wr);
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jsonw_name(wr, "empty");
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jsonw_start_array(wr);
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jsonw_end_array(wr);
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jsonw_name(wr, "NIL");
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jsonw_start_object(wr);
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jsonw_end_object(wr);
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jsonw_null_field(wr, "my_null");
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jsonw_name(wr, "special chars");
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jsonw_start_array(wr);
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jsonw_string_field(wr, "slash", "/");
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jsonw_string_field(wr, "newline", "\n");
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jsonw_string_field(wr, "tab", "\t");
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jsonw_string_field(wr, "ff", "\f");
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jsonw_string_field(wr, "quote", "\"");
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jsonw_string_field(wr, "tick", "\'");
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jsonw_string_field(wr, "backslash", "\\");
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jsonw_end_array(wr);
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jsonw_end_object(wr);
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jsonw_end_object(wr);
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jsonw_destroy(&wr);
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return 0;
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}
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#endif
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