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dfilter: Use an exact floating-point string representation 

The FTREPR_DFILTER format for floating-point numbers
is using an inexact representation so using "apply as
filter" on a floating-point protocol field does not produce a
match, as could be reasonably expected, because we don't
get back the same floating-point number.

Using g_ascii_dtostr() instead produces a string with enough
precision to get back the same machine number with IEEE 754 doubles.

Fixes #16483.
This commit is contained in:
João Valverde 2022-07-22 21:55:27 +01:00
parent fd830dff58
commit 5f85c1f8aa
1 changed files with 13 additions and 9 deletions
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22
epan/ftypes/ftype-double.c
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@ -44,7 +44,7 @@ val_from_literal(fvalue_t *fv, const char *s, gboolean allow_partial_value _U_,
if (endptr == s || *endptr != '\0') {
/* This isn't a valid number. */
if (err_msg != NULL)
*err_msg = ws_strdup_printf("\"%s\" is not a valid number.", s);
*err_msg = ws_strdup_printf("\"%s\" is not a valid floating-point number.", s);
return FALSE;
}
if (errno == ERANGE) {
@ -68,20 +68,24 @@ val_from_literal(fvalue_t *fv, const char *s, gboolean allow_partial_value _U_,
}
static char *
float_val_to_repr(wmem_allocator_t *scope, const fvalue_t *fv, ftrepr_t rtype _U_, int field_display _U_)
float_val_to_repr(wmem_allocator_t *scope, const fvalue_t *fv, ftrepr_t rtype, int field_display _U_)
{
size_t size = G_ASCII_DTOSTR_BUF_SIZE;
char *buf = wmem_alloc(scope, size);
g_ascii_formatd(buf, (gint)size, "%." G_STRINGIFY(FLT_DIG) "g", fv->value.floating);
char *buf = wmem_alloc(scope, G_ASCII_DTOSTR_BUF_SIZE);
if (rtype == FTREPR_DFILTER)
g_ascii_dtostr(buf, G_ASCII_DTOSTR_BUF_SIZE, fv->value.floating);
else
g_ascii_formatd(buf, G_ASCII_DTOSTR_BUF_SIZE, "%." G_STRINGIFY(FLT_DIG) "g", fv->value.floating);
return buf;
}
static char *
double_val_to_repr(wmem_allocator_t *scope, const fvalue_t *fv, ftrepr_t rtype _U_, int field_display _U_)
double_val_to_repr(wmem_allocator_t *scope, const fvalue_t *fv, ftrepr_t rtype, int field_display _U_)
{
size_t size = G_ASCII_DTOSTR_BUF_SIZE;
char *buf = wmem_alloc(scope, size);
g_ascii_formatd(buf, (gint)size, "%." G_STRINGIFY(DBL_DIG) "g", fv->value.floating);
char *buf = wmem_alloc(scope, G_ASCII_DTOSTR_BUF_SIZE);
if (rtype == FTREPR_DFILTER)
g_ascii_dtostr(buf, G_ASCII_DTOSTR_BUF_SIZE, fv->value.floating);
else
g_ascii_formatd(buf, G_ASCII_DTOSTR_BUF_SIZE, "%." G_STRINGIFY(DBL_DIG) "g", fv->value.floating);
return buf;
}