Reduce the amount of code generic on W: io::Write
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220a8680ca
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21
src/lib.rs
21
src/lib.rs
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@ -19,6 +19,10 @@ pub trait Integer {
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fn write<W: io::Write>(self, W) -> io::Result<usize>;
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}
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trait IntegerPrivate {
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fn write_to(self, buf: &mut [u8; MAX_LEN]) -> &[u8];
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}
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const DEC_DIGITS_LUT: &'static[u8] =
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b"0001020304050607080910111213141516171819\
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2021222324252627282930313233343536373839\
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@ -26,13 +30,24 @@ const DEC_DIGITS_LUT: &'static[u8] =
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6061626364656667686970717273747576777879\
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8081828384858687888990919293949596979899";
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const MAX_LEN: usize = 20; // Tie between i64::MIN (including minus sign) and u64::MAX
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// Adaptation of the original implementation at
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// https://github.com/rust-lang/rust/blob/b8214dc6c6fc20d0a660fb5700dca9ebf51ebe89/src/libcore/fmt/num.rs#L188-L266
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macro_rules! impl_Integer {
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($($t:ident),* as $conv_fn:ident) => ($(
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impl Integer for $t {
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#[allow(unused_comparisons)]
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fn write<W: io::Write>(self, mut wr: W) -> io::Result<usize> {
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let mut buf = unsafe { mem::uninitialized() };
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let bytes = self.write_to(&mut buf);
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try!(wr.write_all(bytes));
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Ok(bytes.len())
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}
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}
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impl IntegerPrivate for $t {
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#[allow(unused_comparisons)]
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fn write_to(self, buf: &mut [u8; MAX_LEN]) -> &[u8] {
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let is_nonnegative = self >= 0;
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let mut n = if is_nonnegative {
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self as $conv_fn
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@ -40,7 +55,6 @@ macro_rules! impl_Integer {
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// convert the negative num to positive by summing 1 to it's 2 complement
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(!(self as $conv_fn)).wrapping_add(1)
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};
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let mut buf: [u8; 20] = unsafe { mem::uninitialized() };
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let mut curr = buf.len() as isize;
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let buf_ptr = buf.as_mut_ptr();
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let lut_ptr = DEC_DIGITS_LUT.as_ptr();
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@ -88,8 +102,7 @@ macro_rules! impl_Integer {
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}
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let len = buf.len() - curr as usize;
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try!(wr.write_all(unsafe { slice::from_raw_parts(buf_ptr.offset(curr), len) }));
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Ok(len)
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unsafe { slice::from_raw_parts(buf_ptr.offset(curr), len) }
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}
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})*);
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}
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