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qemu/qapi/string-output-visitor.c
Markus Armbruster 54addb01d8 string-output-visitor: Fix to use sufficient precision 
The string output visitor should serialize numbers so that the string
input visitor deserializes them back to the same number.  It fails to
do so.

print_type_number() uses format %f.  This is prone to nasty rounding
errors.  For instance, numbers between 0 and 0.0000005 get flushed to
zero.

We currently use this visitor only for HMP info migrate, info network,
info qtree, and info memdev.  No double values occur there as far as I
can tell.

Fix anyway by formatting with %.17g.  17 decimal digits always suffice
for IEEE double.

See also recent commit "qobject: Fix qnum_to_string() to use
sufficient precision".

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20201210161452.2813491-9-armbru@redhat.com>
2020-12-19 10:37:16 +01:00

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/*
* String printing Visitor
*
* Copyright Red Hat, Inc. 2012-2016
*
* Author: Paolo Bonzini <pbonzini@redhat.com>
*
* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
* See the COPYING.LIB file in the top-level directory.
*
*/
#include "qemu/osdep.h"
#include "qemu/cutils.h"
#include "qapi/string-output-visitor.h"
#include "qapi/visitor-impl.h"
#include "qemu/host-utils.h"
#include <math.h>
#include "qemu/range.h"
enum ListMode {
LM_NONE, /* not traversing a list of repeated options */
LM_STARTED, /* next_list() ready to be called */
LM_IN_PROGRESS, /* next_list() has been called.
*
* Generating the next list link will consume the most
* recently parsed QemuOpt instance of the repeated
* option.
*
* Parsing a value into the list link will examine the
* next QemuOpt instance of the repeated option, and
* possibly enter LM_SIGNED_INTERVAL or
* LM_UNSIGNED_INTERVAL.
*/
LM_SIGNED_INTERVAL, /* next_list() has been called.
*
* Generating the next list link will consume the most
* recently stored element from the signed interval,
* parsed from the most recent QemuOpt instance of the
* repeated option. This may consume QemuOpt itself
* and return to LM_IN_PROGRESS.
*
* Parsing a value into the list link will store the
* next element of the signed interval.
*/
LM_UNSIGNED_INTERVAL,/* Same as above, only for an unsigned interval. */
LM_END, /* next_list() called, about to see last element. */
};
typedef enum ListMode ListMode;
struct StringOutputVisitor
{
Visitor visitor;
bool human;
GString *string;
char **result;
ListMode list_mode;
union {
int64_t s;
uint64_t u;
} range_start, range_end;
GList *ranges;
void *list; /* Only needed for sanity checking the caller */
};
static StringOutputVisitor *to_sov(Visitor *v)
{
return container_of(v, StringOutputVisitor, visitor);
}
static void string_output_set(StringOutputVisitor *sov, char *string)
{
if (sov->string) {
g_string_free(sov->string, true);
}
sov->string = g_string_new(string);
g_free(string);
}
static void string_output_append(StringOutputVisitor *sov, int64_t a)
{
Range *r = g_malloc0(sizeof(*r));
range_set_bounds(r, a, a);
sov->ranges = range_list_insert(sov->ranges, r);
}
static void string_output_append_range(StringOutputVisitor *sov,
int64_t s, int64_t e)
{
Range *r = g_malloc0(sizeof(*r));
range_set_bounds(r, s, e);
sov->ranges = range_list_insert(sov->ranges, r);
}
static void format_string(StringOutputVisitor *sov, Range *r, bool next,
bool human)
{
if (range_lob(r) != range_upb(r)) {
if (human) {
g_string_append_printf(sov->string, "0x%" PRIx64 "-0x%" PRIx64,
range_lob(r), range_upb(r));
} else {
g_string_append_printf(sov->string, "%" PRId64 "-%" PRId64,
range_lob(r), range_upb(r));
}
} else {
if (human) {
g_string_append_printf(sov->string, "0x%" PRIx64, range_lob(r));
} else {
g_string_append_printf(sov->string, "%" PRId64, range_lob(r));
}
}
if (next) {
g_string_append(sov->string, ",");
}
}
static bool print_type_int64(Visitor *v, const char *name, int64_t *obj,
Error **errp)
{
StringOutputVisitor *sov = to_sov(v);
GList *l;
switch (sov->list_mode) {
case LM_NONE:
string_output_append(sov, *obj);
break;
case LM_STARTED:
sov->range_start.s = *obj;
sov->range_end.s = *obj;
sov->list_mode = LM_IN_PROGRESS;
return true;
case LM_IN_PROGRESS:
if (sov->range_end.s + 1 == *obj) {
sov->range_end.s++;
} else {
if (sov->range_start.s == sov->range_end.s) {
string_output_append(sov, sov->range_end.s);
} else {
assert(sov->range_start.s < sov->range_end.s);
string_output_append_range(sov, sov->range_start.s,
sov->range_end.s);
}
sov->range_start.s = *obj;
sov->range_end.s = *obj;
}
return true;
case LM_END:
if (sov->range_end.s + 1 == *obj) {
sov->range_end.s++;
assert(sov->range_start.s < sov->range_end.s);
string_output_append_range(sov, sov->range_start.s,
sov->range_end.s);
} else {
if (sov->range_start.s == sov->range_end.s) {
string_output_append(sov, sov->range_end.s);
} else {
assert(sov->range_start.s < sov->range_end.s);
string_output_append_range(sov, sov->range_start.s,
sov->range_end.s);
}
string_output_append(sov, *obj);
}
break;
default:
abort();
}
l = sov->ranges;
while (l) {
Range *r = l->data;
format_string(sov, r, l->next != NULL, false);
l = l->next;
}
if (sov->human) {
l = sov->ranges;
g_string_append(sov->string, " (");
while (l) {
Range *r = l->data;
format_string(sov, r, l->next != NULL, true);
l = l->next;
}
g_string_append(sov->string, ")");
}
return true;
}
static bool print_type_uint64(Visitor *v, const char *name, uint64_t *obj,
Error **errp)
{
/* FIXME: print_type_int64 mishandles values over INT64_MAX */
int64_t i = *obj;
return print_type_int64(v, name, &i, errp);
}
static bool print_type_size(Visitor *v, const char *name, uint64_t *obj,
Error **errp)
{
StringOutputVisitor *sov = to_sov(v);
uint64_t val;
char *out, *psize;
if (!sov->human) {
out = g_strdup_printf("%"PRIu64, *obj);
string_output_set(sov, out);
return true;
}
val = *obj;
psize = size_to_str(val);
out = g_strdup_printf("%"PRIu64" (%s)", val, psize);
string_output_set(sov, out);
g_free(psize);
return true;
}
static bool print_type_bool(Visitor *v, const char *name, bool *obj,
Error **errp)
{
StringOutputVisitor *sov = to_sov(v);
string_output_set(sov, g_strdup(*obj ? "true" : "false"));
return true;
}
static bool print_type_str(Visitor *v, const char *name, char **obj,
Error **errp)
{
StringOutputVisitor *sov = to_sov(v);
char *out;
if (sov->human) {
out = *obj ? g_strdup_printf("\"%s\"", *obj) : g_strdup("<null>");
} else {
out = g_strdup(*obj ? *obj : "");
}
string_output_set(sov, out);
return true;
}
static bool print_type_number(Visitor *v, const char *name, double *obj,
Error **errp)
{
StringOutputVisitor *sov = to_sov(v);
string_output_set(sov, g_strdup_printf("%.17g", *obj));
return true;
}
static bool print_type_null(Visitor *v, const char *name, QNull **obj,
Error **errp)
{
StringOutputVisitor *sov = to_sov(v);
char *out;
if (sov->human) {
out = g_strdup("<null>");
} else {
out = g_strdup("");
}
string_output_set(sov, out);
return true;
}
static bool
start_list(Visitor *v, const char *name, GenericList **list, size_t size,
Error **errp)
{
StringOutputVisitor *sov = to_sov(v);
/* we can't traverse a list in a list */
assert(sov->list_mode == LM_NONE);
/* We don't support visits without a list */
assert(list);
sov->list = list;
/* List handling is only needed if there are at least two elements */
if (*list && (*list)->next) {
sov->list_mode = LM_STARTED;
}
return true;
}
static GenericList *next_list(Visitor *v, GenericList *tail, size_t size)
{
StringOutputVisitor *sov = to_sov(v);
GenericList *ret = tail->next;
if (ret && !ret->next) {
sov->list_mode = LM_END;
}
return ret;
}
static void end_list(Visitor *v, void **obj)
{
StringOutputVisitor *sov = to_sov(v);
assert(sov->list == obj);
assert(sov->list_mode == LM_STARTED ||
sov->list_mode == LM_END ||
sov->list_mode == LM_NONE ||
sov->list_mode == LM_IN_PROGRESS);
sov->list_mode = LM_NONE;
}
static void string_output_complete(Visitor *v, void *opaque)
{
StringOutputVisitor *sov = to_sov(v);
assert(opaque == sov->result);
*sov->result = g_string_free(sov->string, false);
sov->string = NULL;
}
static void free_range(void *range, void *dummy)
{
g_free(range);
}
static void string_output_free(Visitor *v)
{
StringOutputVisitor *sov = to_sov(v);
if (sov->string) {
g_string_free(sov->string, true);
}
g_list_foreach(sov->ranges, free_range, NULL);
g_list_free(sov->ranges);
g_free(sov);
}
Visitor *string_output_visitor_new(bool human, char **result)
{
StringOutputVisitor *v;
v = g_malloc0(sizeof(*v));
v->string = g_string_new(NULL);
v->human = human;
v->result = result;
*result = NULL;
v->visitor.type = VISITOR_OUTPUT;
v->visitor.type_int64 = print_type_int64;
v->visitor.type_uint64 = print_type_uint64;
v->visitor.type_size = print_type_size;
v->visitor.type_bool = print_type_bool;
v->visitor.type_str = print_type_str;
v->visitor.type_number = print_type_number;
v->visitor.type_null = print_type_null;
v->visitor.start_list = start_list;
v->visitor.next_list = next_list;
v->visitor.end_list = end_list;
v->visitor.complete = string_output_complete;
v->visitor.free = string_output_free;
return &v->visitor;
}
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