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![Markus Armbruster](/assets/img/avatar_default.png)
We have two JSON writers written in C: qobject/qjson.c provides qobject_to_json(), and migration/qjson.c provides a more low level imperative interface. They don't share code. The latter tacitly limits numbers to int64_t, and strings contents to characters that don't need escaping. Factor out qobject_to_json()'s JSON writer as qobject/json-writer.c. Straightforward, except for numbers: since the writer is to be independent of QObject, it can't use qnum_to_string(). Open-code it instead. This is actually an improvement of sorts, because it liberates qnum_to_string() from JSON's needs: its JSON-related FIXMEs move to the JSON writer, where they belong. The next commit will replace migration/qjson.c. Signed-off-by: Markus Armbruster <armbru@redhat.com> Message-Id: <20201211171152.146877-16-armbru@redhat.com>
248 lines
6.5 KiB
C
248 lines
6.5 KiB
C
/*
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* JSON Writer
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*
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* Copyright IBM, Corp. 2009
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* Copyright (c) 2010-2020 Red Hat Inc.
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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* Markus Armbruster <armbru@redhat.com>
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*
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* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
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* See the COPYING.LIB file in the top-level directory.
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*
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*/
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#include "qemu/osdep.h"
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#include "qapi/qmp/json-writer.h"
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#include "qemu/unicode.h"
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struct JSONWriter {
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bool pretty;
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bool need_comma;
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GString *contents;
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GByteArray *container_is_array;
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};
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JSONWriter *json_writer_new(bool pretty)
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{
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JSONWriter *writer = g_new(JSONWriter, 1);
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writer->pretty = pretty;
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writer->need_comma = false;
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writer->contents = g_string_new(NULL);
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writer->container_is_array = g_byte_array_new();
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return writer;
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}
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const char *json_writer_get(JSONWriter *writer)
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{
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g_assert(!writer->container_is_array->len);
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return writer->contents->str;
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}
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GString *json_writer_get_and_free(JSONWriter *writer)
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{
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GString *contents = writer->contents;
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writer->contents = NULL;
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g_byte_array_free(writer->container_is_array, true);
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g_free(writer);
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return contents;
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}
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void json_writer_free(JSONWriter *writer)
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{
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if (writer) {
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g_string_free(json_writer_get_and_free(writer), true);
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}
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}
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static void enter_container(JSONWriter *writer, bool is_array)
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{
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unsigned depth = writer->container_is_array->len;
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g_byte_array_set_size(writer->container_is_array, depth + 1);
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writer->container_is_array->data[depth] = is_array;
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writer->need_comma = false;
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}
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static void leave_container(JSONWriter *writer, bool is_array)
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{
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unsigned depth = writer->container_is_array->len;
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assert(depth);
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assert(writer->container_is_array->data[depth - 1] == is_array);
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g_byte_array_set_size(writer->container_is_array, depth - 1);
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writer->need_comma = true;
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}
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static bool in_object(JSONWriter *writer)
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{
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unsigned depth = writer->container_is_array->len;
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return depth && !writer->container_is_array->data[depth - 1];
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}
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static void pretty_newline(JSONWriter *writer)
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{
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if (writer->pretty) {
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g_string_append_printf(writer->contents, "\n%*s",
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writer->container_is_array->len * 4, "");
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}
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}
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static void pretty_newline_or_space(JSONWriter *writer)
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{
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if (writer->pretty) {
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g_string_append_printf(writer->contents, "\n%*s",
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writer->container_is_array->len * 4, "");
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} else {
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g_string_append_c(writer->contents, ' ');
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}
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}
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static void quoted_str(JSONWriter *writer, const char *str)
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{
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const char *ptr;
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char *end;
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int cp;
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g_string_append_c(writer->contents, '"');
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for (ptr = str; *ptr; ptr = end) {
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cp = mod_utf8_codepoint(ptr, 6, &end);
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switch (cp) {
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case '\"':
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g_string_append(writer->contents, "\\\"");
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break;
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case '\\':
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g_string_append(writer->contents, "\\\\");
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break;
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case '\b':
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g_string_append(writer->contents, "\\b");
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break;
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case '\f':
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g_string_append(writer->contents, "\\f");
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break;
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case '\n':
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g_string_append(writer->contents, "\\n");
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break;
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case '\r':
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g_string_append(writer->contents, "\\r");
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break;
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case '\t':
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g_string_append(writer->contents, "\\t");
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break;
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default:
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if (cp < 0) {
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cp = 0xFFFD; /* replacement character */
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}
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if (cp > 0xFFFF) {
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/* beyond BMP; need a surrogate pair */
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g_string_append_printf(writer->contents, "\\u%04X\\u%04X",
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0xD800 + ((cp - 0x10000) >> 10),
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0xDC00 + ((cp - 0x10000) & 0x3FF));
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} else if (cp < 0x20 || cp >= 0x7F) {
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g_string_append_printf(writer->contents, "\\u%04X", cp);
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} else {
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g_string_append_c(writer->contents, cp);
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}
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}
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};
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g_string_append_c(writer->contents, '"');
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}
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static void maybe_comma_name(JSONWriter *writer, const char *name)
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{
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if (writer->need_comma) {
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g_string_append_c(writer->contents, ',');
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pretty_newline_or_space(writer);
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} else {
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if (writer->contents->len) {
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pretty_newline(writer);
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}
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writer->need_comma = true;
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}
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if (in_object(writer)) {
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quoted_str(writer, name);
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g_string_append(writer->contents, ": ");
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}
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}
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void json_writer_start_object(JSONWriter *writer, const char *name)
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{
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maybe_comma_name(writer, name);
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g_string_append_c(writer->contents, '{');
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enter_container(writer, false);
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}
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void json_writer_end_object(JSONWriter *writer)
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{
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leave_container(writer, false);
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pretty_newline(writer);
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g_string_append_c(writer->contents, '}');
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}
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void json_writer_start_array(JSONWriter *writer, const char *name)
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{
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maybe_comma_name(writer, name);
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g_string_append_c(writer->contents, '[');
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enter_container(writer, true);
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}
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void json_writer_end_array(JSONWriter *writer)
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{
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leave_container(writer, true);
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pretty_newline(writer);
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g_string_append_c(writer->contents, ']');
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}
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void json_writer_bool(JSONWriter *writer, const char *name, bool val)
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{
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maybe_comma_name(writer, name);
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g_string_append(writer->contents, val ? "true" : "false");
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}
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void json_writer_null(JSONWriter *writer, const char *name)
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{
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maybe_comma_name(writer, name);
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g_string_append(writer->contents, "null");
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}
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void json_writer_int64(JSONWriter *writer, const char *name, int64_t val)
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{
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maybe_comma_name(writer, name);
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g_string_append_printf(writer->contents, "%" PRId64, val);
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}
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void json_writer_uint64(JSONWriter *writer, const char *name, uint64_t val)
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{
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maybe_comma_name(writer, name);
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g_string_append_printf(writer->contents, "%" PRIu64, val);
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}
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void json_writer_double(JSONWriter *writer, const char *name, double val)
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{
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maybe_comma_name(writer, name);
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/*
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* FIXME: g_string_append_printf() is locale dependent; but JSON
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* requires numbers to be formatted as if in the C locale.
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* Dependence on C locale is a pervasive issue in QEMU.
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*/
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/*
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* FIXME: This risks printing Inf or NaN, which are not valid
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* JSON values.
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*/
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g_string_append_printf(writer->contents, "%.17g", val);
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}
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void json_writer_str(JSONWriter *writer, const char *name, const char *str)
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{
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maybe_comma_name(writer, name);
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quoted_str(writer, str);
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}
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