Add internal routing to convert a number to string

Add internal routing to write a number to a char buffer.
This commit is contained in:
Eugen Wissner 2017-07-28 09:08:58 +02:00
parent 3afb40e09e
commit 51ade45108

View File

@ -607,3 +607,102 @@ private @nogc unittest
assert(exception !is null); assert(exception !is null);
defaultAllocator.dispose(exception); defaultAllocator.dispose(exception);
} }
package char[] number2String(T)(const T number, char[] buffer)
{
// abs the integer.
ulong n64 = number < 0 ? -cast(long) number : number;
char[20] rightAligned;
char* start = rightAligned.ptr + rightAligned.sizeof;
while (true)
{
// Do in 32-bit chunks (avoid lots of 64-bit divides even with constant
// denominators).
char* o = start - 8;
uint n;
if (n64 >= 100000000)
{
n = n64 % 100000000;
n64 /= 100000000;
}
else
{
n = cast(uint) n64;
n64 = 0;
}
while (n)
{
*--start = cast(char) (n % 10) + '0';
n /= 10;
}
// Ignore the leading zero if it was the last part of the integer.
if (n64 == 0)
{
if ((start[0] == '0')
&& (start != (rightAligned.ptr + rightAligned.sizeof)))
{
++start;
}
break;
}
// Copy leading zeros if it wasn't the most significant part of the
// integer.
while (start != o)
{
*--start = '0';
}
}
// Get the length that we copied.
auto l = cast(uint) ((rightAligned.ptr + rightAligned.sizeof) - start);
if (l == 0)
{
*--start = '0';
l = 1;
}
// Write the string.
char* bp = buffer.ptr;
// Set sign.
if (number < 0)
{
*bp++ = '-';
}
// Copy the string into the target buffer.
uint n = l;
while (n)
{
int i = n;
n -= i;
while (i >= 4)
{
*cast(uint*) bp = *cast(uint*) start;
bp += 4;
start += 4;
i -= 4;
}
while (i)
{
*bp++ = *start++;
--i;
}
}
return buffer[0 .. bp - buffer.ptr];
}
private @nogc unittest
{
char[21] buf;
assert(number2String(80, buf) == "80");
assert(number2String(-80, buf) == "-80");
assert(number2String(0, buf) == "0");
assert(number2String(uint.max, buf) == "4294967295");
assert(number2String(int.min, buf) == "-2147483648");
}