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cJSON: Fix print_number to print significant digits of doubles

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This commit is contained in:
Debora Grosse
2017-04-20 10:55:09 -04:00
parent 6ccfd5d603
commit 3fc9bc0648
2 changed files with 21 additions and 59 deletions
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56
cJSON.c
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@ -410,27 +410,6 @@ static void update_offset(printbuffer * const buffer)
buffer->offset += strlen((const char*)buffer_pointer);
}
/* Removes trailing zeroes from the end of a printed number */
static int trim_trailing_zeroes(const unsigned char * const number, int length, const unsigned char decimal_point)
{
if ((number == NULL) || (length <= 0))
{
return -1;
}
while ((length > 0) && (number[length - 1] == '0'))
{
length--;
}
if ((length > 0) && (number[length - 1] == decimal_point))
{
/* remove trailing decimal_point */
length--;
}
return length;
}
/* Render the number nicely from the given item into a string. */
static cJSON_bool print_number(const cJSON * const item, printbuffer * const output_buffer, const internal_hooks * const hooks)
{
@ -438,9 +417,9 @@ static cJSON_bool print_number(const cJSON * const item, printbuffer * const out
double d = item->valuedouble;
int length = 0;
size_t i = 0;
cJSON_bool trim_zeroes = true; /* should zeroes at the end be removed? */
unsigned char number_buffer[64]; /* temporary buffer to print the number into */
unsigned char number_buffer[26]; /* temporary buffer to print the number into */
unsigned char decimal_point = get_decimal_point();
double test;
if (output_buffer == NULL)
{
@ -452,20 +431,22 @@ static cJSON_bool print_number(const cJSON * const item, printbuffer * const out
{
length = sprintf((char*)number_buffer, "null");
}
else if ((fabs(floor(d) - d) <= DBL_EPSILON) && (fabs(d) < 1.0e60))
/* This checks for negative zero */
else if (d == 0)
{
/* integer */
length = sprintf((char*)number_buffer, "%.0f", d);
trim_zeroes = false; /* don't remove zeroes for "big integers" */
}
else if ((fabs(d) < 1.0e-6) || (fabs(d) > 1.0e9))
{
length = sprintf((char*)number_buffer, "%e", d);
trim_zeroes = false; /* don't remove zeroes in engineering notation */
length = sprintf((char*)number_buffer, "0");
}
else
{
length = sprintf((char*)number_buffer, "%f", d);
/* Try 15 decimal places of precision to avoid nonsignificant nonzero digits */
length = sprintf((char*)number_buffer, "%1.15g", d);
/* Check whether the original double can be recovered */
if ((sscanf((char*)number_buffer, "%lg", &test) != 1) || ((double)test != d))
{
/* If not, print with 17 decimal places of precision */
length = sprintf((char*)number_buffer, "%1.17g", d);
}
}
/* sprintf failed or buffer overrun occured */
@ -474,15 +455,6 @@ static cJSON_bool print_number(const cJSON * const item, printbuffer * const out
return false;
}
if (trim_zeroes)
{
length = trim_trailing_zeroes(number_buffer, length, decimal_point);
if (length <= 0)
{
return false;
}
}
/* reserve appropriate space in the output */
output_pointer = ensure(output_buffer, (size_t)length, hooks);
if (output_pointer == NULL)