src/libcore/fmt/num.rs - third_party/rust - Git at Google

 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.

 //! Integer and floating-point number formatting

 #![allow(deprecated)]

 // FIXME: #6220 Implement floating point formatting

 use prelude::v1::*;

 use fmt;
 use num::Zero;
 use ops::{Div, Rem, Sub};
 use str;
 use slice;
 use ptr;
 use mem;

 #[doc(hidden)]
 trait Int: Zero + PartialEq + PartialOrd + Div<Output=Self> + Rem<Output=Self> +
            Sub<Output=Self> + Copy {
     fn from_u8(u: u8) -> Self;
     fn to_u8(&self) -> u8;
     fn to_u32(&self) -> u32;
     fn to_u64(&self) -> u64;
 }

 macro_rules! doit {
     ($($t:ident)*) => ($(impl Int for $t {
         fn from_u8(u: u8) -> $t { u as $t }
         fn to_u8(&self) -> u8 { *self as u8 }
         fn to_u32(&self) -> u32 { *self as u32 }
         fn to_u64(&self) -> u64 { *self as u64 }
     })*)
 }
 doit! { i8 i16 i32 i64 isize u8 u16 u32 u64 usize }

 /// A type that represents a specific radix
 #[doc(hidden)]
 trait GenericRadix {
     /// The number of digits.
     fn base(&self) -> u8;

     /// A radix-specific prefix string.
     fn prefix(&self) -> &'static str {
         ""
     }

     /// Converts an integer to corresponding radix digit.
     fn digit(&self, x: u8) -> u8;

     /// Format an integer using the radix using a formatter.
     fn fmt_int<T: Int>(&self, mut x: T, f: &mut fmt::Formatter) -> fmt::Result {
         // The radix can be as low as 2, so we need a buffer of at least 64
         // characters for a base 2 number.
         let zero = T::zero();
         let is_nonnegative = x >= zero;
         let mut buf = [0; 64];
         let mut curr = buf.len();
         let base = T::from_u8(self.base());
         if is_nonnegative {
             // Accumulate each digit of the number from the least significant
             // to the most significant figure.
             for byte in buf.iter_mut().rev() {
                 let n = x % base;              // Get the current place value.
                 x = x / base;                  // Deaccumulate the number.
                 *byte = self.digit(n.to_u8()); // Store the digit in the buffer.
                 curr -= 1;
                 if x == zero {
                     // No more digits left to accumulate.
                     break
                 };
             }
         } else {
             // Do the same as above, but accounting for two's complement.
             for byte in buf.iter_mut().rev() {
                 let n = zero - (x % base);     // Get the current place value.
                 x = x / base;                  // Deaccumulate the number.
                 *byte = self.digit(n.to_u8()); // Store the digit in the buffer.
                 curr -= 1;
                 if x == zero {
                     // No more digits left to accumulate.
                     break
                 };
             }
         }
         let buf = unsafe { str::from_utf8_unchecked(&buf[curr..]) };
         f.pad_integral(is_nonnegative, self.prefix(), buf)
     }
 }

 /// A binary (base 2) radix
 #[derive(Clone, PartialEq)]
 struct Binary;

 /// An octal (base 8) radix
 #[derive(Clone, PartialEq)]
 struct Octal;

 /// A decimal (base 10) radix
 #[derive(Clone, PartialEq)]
 struct Decimal;

 /// A hexadecimal (base 16) radix, formatted with lower-case characters
 #[derive(Clone, PartialEq)]
 struct LowerHex;

 /// A hexadecimal (base 16) radix, formatted with upper-case characters
 #[derive(Clone, PartialEq)]
 struct UpperHex;

 macro_rules! radix {
     ($T:ident, $base:expr, $prefix:expr, $($x:pat => $conv:expr),+) => {
         impl GenericRadix for $T {
             fn base(&self) -> u8 { $base }
             fn prefix(&self) -> &'static str { $prefix }
             fn digit(&self, x: u8) -> u8 {
                 match x {
                     $($x => $conv,)+
                     x => panic!("number not in the range 0..{}: {}", self.base() - 1, x),
                 }
             }
         }
     }
 }

 radix! { Binary,    2, "0b", x @  0 ...  2 => b'0' + x }
 radix! { Octal,     8, "0o", x @  0 ...  7 => b'0' + x }
 radix! { Decimal,  10, "",   x @  0 ...  9 => b'0' + x }
 radix! { LowerHex, 16, "0x", x @  0 ...  9 => b'0' + x,
                              x @ 10 ... 15 => b'a' + (x - 10) }
 radix! { UpperHex, 16, "0x", x @  0 ...  9 => b'0' + x,
                              x @ 10 ... 15 => b'A' + (x - 10) }

 /// A radix with in the range of `2..36`.
 #[derive(Clone, Copy, PartialEq)]
 #[unstable(feature = "fmt_radix",
            reason = "may be renamed or move to a different module",
            issue = "27728")]
 #[rustc_deprecated(since = "1.7.0", reason = "not used enough to stabilize")]
 pub struct Radix {
     base: u8,
 }

 impl Radix {
     fn new(base: u8) -> Radix {
         assert!(2 <= base && base <= 36,
                 "the base must be in the range of 2..36: {}",
                 base);
         Radix { base: base }
     }
 }

 impl GenericRadix for Radix {
     fn base(&self) -> u8 {
         self.base
     }
     fn digit(&self, x: u8) -> u8 {
         match x {
             x @  0 ... 9 => b'0' + x,
             x if x < self.base() => b'a' + (x - 10),
             x => panic!("number not in the range 0..{}: {}", self.base() - 1, x),
         }
     }
 }

 /// A helper type for formatting radixes.
 #[unstable(feature = "fmt_radix",
            reason = "may be renamed or move to a different module",
            issue = "27728")]
 #[rustc_deprecated(since = "1.7.0", reason = "not used enough to stabilize")]
 #[derive(Copy, Clone)]
 pub struct RadixFmt<T, R>(T, R);

 /// Constructs a radix formatter in the range of `2..36`.
 ///
 /// # Examples
 ///
 /// ```
 /// #![feature(fmt_radix)]
 ///
 /// use std::fmt::radix;
 /// assert_eq!(format!("{}", radix(55, 36)), "1j".to_string());
 /// ```
 #[unstable(feature = "fmt_radix",
            reason = "may be renamed or move to a different module",
            issue = "27728")]
 #[rustc_deprecated(since = "1.7.0", reason = "not used enough to stabilize")]
 pub fn radix<T>(x: T, base: u8) -> RadixFmt<T, Radix> {
     RadixFmt(x, Radix::new(base))
 }

 macro_rules! radix_fmt {
     ($T:ty as $U:ty, $fmt:ident) => {
         #[stable(feature = "rust1", since = "1.0.0")]
         impl fmt::Debug for RadixFmt<$T, Radix> {
             fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
                 fmt::Display::fmt(self, f)
             }
         }
         #[stable(feature = "rust1", since = "1.0.0")]
         impl fmt::Display for RadixFmt<$T, Radix> {
             fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
                 match *self { RadixFmt(ref x, radix) => radix.$fmt(*x as $U, f) }
             }
         }
     }
 }

 macro_rules! int_base {
     ($Trait:ident for $T:ident as $U:ident -> $Radix:ident) => {
         #[stable(feature = "rust1", since = "1.0.0")]
         impl fmt::$Trait for $T {
             fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
                 $Radix.fmt_int(*self as $U, f)
             }
         }
     }
 }

 macro_rules! debug {
     ($T:ident) => {
         #[stable(feature = "rust1", since = "1.0.0")]
         impl fmt::Debug for $T {
             fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
                 fmt::Display::fmt(self, f)
             }
         }
     }
 }

 macro_rules! integer {
     ($Int:ident, $Uint:ident) => {
         int_base! { Binary   for $Int as $Uint  -> Binary }
         int_base! { Octal    for $Int as $Uint  -> Octal }
         int_base! { LowerHex for $Int as $Uint  -> LowerHex }
         int_base! { UpperHex for $Int as $Uint  -> UpperHex }
         radix_fmt! { $Int as $Int, fmt_int }
         debug! { $Int }

         int_base! { Binary   for $Uint as $Uint -> Binary }
         int_base! { Octal    for $Uint as $Uint -> Octal }
         int_base! { LowerHex for $Uint as $Uint -> LowerHex }
         int_base! { UpperHex for $Uint as $Uint -> UpperHex }
         radix_fmt! { $Uint as $Uint, fmt_int }
         debug! { $Uint }
     }
 }
 integer! { isize, usize }
 integer! { i8, u8 }
 integer! { i16, u16 }
 integer! { i32, u32 }
 integer! { i64, u64 }

 const DEC_DIGITS_LUT: &'static[u8] =
     b"0001020304050607080910111213141516171819\
       2021222324252627282930313233343536373839\
       4041424344454647484950515253545556575859\
       6061626364656667686970717273747576777879\
       8081828384858687888990919293949596979899";

 macro_rules! impl_Display {
     ($($t:ident),*: $conv_fn:ident) => ($(
     #[stable(feature = "rust1", since = "1.0.0")]
     impl fmt::Display for $t {
         #[allow(unused_comparisons)]
         fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
             let is_nonnegative = *self >= 0;
             let mut n = if is_nonnegative {
                 self.$conv_fn()
             } else {
                 // convert the negative num to positive by summing 1 to it's 2 complement
                 (!self.$conv_fn()).wrapping_add(1)
             };
             let mut buf: [u8; 20] = unsafe { mem::uninitialized() };
             let mut curr = buf.len() as isize;
             let buf_ptr = buf.as_mut_ptr();
             let lut_ptr = DEC_DIGITS_LUT.as_ptr();

             unsafe {
                 // eagerly decode 4 characters at a time
                 if <$t>::max_value() as u64 >= 10000 {
                     while n >= 10000 {
                         let rem = (n % 10000) as isize;
                         n /= 10000;

                         let d1 = (rem / 100) << 1;
                         let d2 = (rem % 100) << 1;
                         curr -= 4;
                         ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
                         ptr::copy_nonoverlapping(lut_ptr.offset(d2), buf_ptr.offset(curr + 2), 2);
                     }
                 }

                 // if we reach here numbers are <= 9999, so at most 4 chars long
                 let mut n = n as isize; // possibly reduce 64bit math

                 // decode 2 more chars, if > 2 chars
                 if n >= 100 {
                     let d1 = (n % 100) << 1;
                     n /= 100;
                     curr -= 2;
                     ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
                 }

                 // decode last 1 or 2 chars
                 if n < 10 {
                     curr -= 1;
                     *buf_ptr.offset(curr) = (n as u8) + 48;
                 } else {
                     let d1 = n << 1;
                     curr -= 2;
                     ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
                 }
             }

             let buf_slice = unsafe {
                 str::from_utf8_unchecked(
                     slice::from_raw_parts(buf_ptr.offset(curr), buf.len() - curr as usize))
             };
             f.pad_integral(is_nonnegative, "", buf_slice)
         }
     })*);
 }

 impl_Display!(i8, u8, i16, u16, i32, u32: to_u32);
 impl_Display!(i64, u64: to_u64);
 #[cfg(target_pointer_width = "32")]
 impl_Display!(isize, usize: to_u32);
 #[cfg(target_pointer_width = "64")]
 impl_Display!(isize, usize: to_u64);
	// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
	// file at the top-level directory of this distribution and at
	// http://rust-lang.org/COPYRIGHT.
	//
	// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
	// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
	// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
	// option. This file may not be copied, modified, or distributed
	// except according to those terms.

	//! Integer and floating-point number formatting

	#![allow(deprecated)]

	// FIXME: #6220 Implement floating point formatting

	use prelude::v1::*;

	use fmt;
	use num::Zero;
	use ops::{Div, Rem, Sub};
	use str;
	use slice;
	use ptr;
	use mem;

	#[doc(hidden)]
	trait Int: Zero + PartialEq + PartialOrd + Div<Output=Self> + Rem<Output=Self> +
	Sub<Output=Self> + Copy {
	fn from_u8(u: u8) -> Self;
	fn to_u8(&self) -> u8;
	fn to_u32(&self) -> u32;
	fn to_u64(&self) -> u64;
	}

	macro_rules! doit {
	($($t:ident)*) => ($(impl Int for $t {
	fn from_u8(u: u8) -> $t { u as $t }
	fn to_u8(&self) -> u8 { *self as u8 }
	fn to_u32(&self) -> u32 { *self as u32 }
	fn to_u64(&self) -> u64 { *self as u64 }
	})*)
	}
	doit! { i8 i16 i32 i64 isize u8 u16 u32 u64 usize }

	/// A type that represents a specific radix
	#[doc(hidden)]
	trait GenericRadix {
	/// The number of digits.
	fn base(&self) -> u8;

	/// A radix-specific prefix string.
	fn prefix(&self) -> &'static str {
	""
	}

	/// Converts an integer to corresponding radix digit.
	fn digit(&self, x: u8) -> u8;

	/// Format an integer using the radix using a formatter.
	fn fmt_int<T: Int>(&self, mut x: T, f: &mut fmt::Formatter) -> fmt::Result {
	// The radix can be as low as 2, so we need a buffer of at least 64
	// characters for a base 2 number.
	let zero = T::zero();
	let is_nonnegative = x >= zero;
	let mut buf = [0; 64];
	let mut curr = buf.len();
	let base = T::from_u8(self.base());
	if is_nonnegative {
	// Accumulate each digit of the number from the least significant
	// to the most significant figure.
	for byte in buf.iter_mut().rev() {
	let n = x % base; // Get the current place value.
	x = x / base; // Deaccumulate the number.
	*byte = self.digit(n.to_u8()); // Store the digit in the buffer.
	curr -= 1;
	if x == zero {
	// No more digits left to accumulate.
	break
	};
	}
	} else {
	// Do the same as above, but accounting for two's complement.
	for byte in buf.iter_mut().rev() {
	let n = zero - (x % base); // Get the current place value.
	x = x / base; // Deaccumulate the number.
	*byte = self.digit(n.to_u8()); // Store the digit in the buffer.
	curr -= 1;
	if x == zero {
	// No more digits left to accumulate.
	break
	};
	}
	}
	let buf = unsafe { str::from_utf8_unchecked(&buf[curr..]) };
	f.pad_integral(is_nonnegative, self.prefix(), buf)
	}
	}

	/// A binary (base 2) radix
	#[derive(Clone, PartialEq)]
	struct Binary;

	/// An octal (base 8) radix
	#[derive(Clone, PartialEq)]
	struct Octal;

	/// A decimal (base 10) radix
	#[derive(Clone, PartialEq)]
	struct Decimal;

	/// A hexadecimal (base 16) radix, formatted with lower-case characters
	#[derive(Clone, PartialEq)]
	struct LowerHex;

	/// A hexadecimal (base 16) radix, formatted with upper-case characters
	#[derive(Clone, PartialEq)]
	struct UpperHex;

	macro_rules! radix {
	($T:ident, $base:expr, $prefix:expr, $($x:pat => $conv:expr),+) => {
	impl GenericRadix for $T {
	fn base(&self) -> u8 { $base }
	fn prefix(&self) -> &'static str { $prefix }
	fn digit(&self, x: u8) -> u8 {
	match x {
	$($x => $conv,)+
	x => panic!("number not in the range 0..{}: {}", self.base() - 1, x),
	}
	}
	}
	}
	}

	radix! { Binary, 2, "0b", x @ 0 ... 2 => b'0' + x }
	radix! { Octal, 8, "0o", x @ 0 ... 7 => b'0' + x }
	radix! { Decimal, 10, "", x @ 0 ... 9 => b'0' + x }
	radix! { LowerHex, 16, "0x", x @ 0 ... 9 => b'0' + x,
	x @ 10 ... 15 => b'a' + (x - 10) }
	radix! { UpperHex, 16, "0x", x @ 0 ... 9 => b'0' + x,
	x @ 10 ... 15 => b'A' + (x - 10) }

	/// A radix with in the range of `2..36`.
	#[derive(Clone, Copy, PartialEq)]
	#[unstable(feature = "fmt_radix",
	reason = "may be renamed or move to a different module",
	issue = "27728")]
	#[rustc_deprecated(since = "1.7.0", reason = "not used enough to stabilize")]
	pub struct Radix {
	base: u8,
	}

	impl Radix {
	fn new(base: u8) -> Radix {
	assert!(2 <= base && base <= 36,
	"the base must be in the range of 2..36: {}",
	base);
	Radix { base: base }
	}
	}

	impl GenericRadix for Radix {
	fn base(&self) -> u8 {
	self.base
	}
	fn digit(&self, x: u8) -> u8 {
	match x {
	x @ 0 ... 9 => b'0' + x,
	x if x < self.base() => b'a' + (x - 10),
	x => panic!("number not in the range 0..{}: {}", self.base() - 1, x),
	}
	}
	}

	/// A helper type for formatting radixes.
	#[unstable(feature = "fmt_radix",
	reason = "may be renamed or move to a different module",
	issue = "27728")]
	#[rustc_deprecated(since = "1.7.0", reason = "not used enough to stabilize")]
	#[derive(Copy, Clone)]
	pub struct RadixFmt<T, R>(T, R);

	/// Constructs a radix formatter in the range of `2..36`.
	///
	/// # Examples
	///
	/// ```
	/// #![feature(fmt_radix)]
	///
	/// use std::fmt::radix;
	/// assert_eq!(format!("{}", radix(55, 36)), "1j".to_string());
	/// ```
	#[unstable(feature = "fmt_radix",
	reason = "may be renamed or move to a different module",
	issue = "27728")]
	#[rustc_deprecated(since = "1.7.0", reason = "not used enough to stabilize")]
	pub fn radix<T>(x: T, base: u8) -> RadixFmt<T, Radix> {
	RadixFmt(x, Radix::new(base))
	}

	macro_rules! radix_fmt {
	($T:ty as $U:ty, $fmt:ident) => {
	#[stable(feature = "rust1", since = "1.0.0")]
	impl fmt::Debug for RadixFmt<$T, Radix> {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
	fmt::Display::fmt(self, f)
	}
	}
	#[stable(feature = "rust1", since = "1.0.0")]
	impl fmt::Display for RadixFmt<$T, Radix> {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
	match self { RadixFmt(ref x, radix) => radix.$fmt(x as $U, f) }
	}
	}
	}
	}

	macro_rules! int_base {
	($Trait:ident for $T:ident as $U:ident -> $Radix:ident) => {
	#[stable(feature = "rust1", since = "1.0.0")]
	impl fmt::$Trait for $T {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
	$Radix.fmt_int(*self as $U, f)
	}
	}
	}
	}

	macro_rules! debug {
	($T:ident) => {
	#[stable(feature = "rust1", since = "1.0.0")]
	impl fmt::Debug for $T {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
	fmt::Display::fmt(self, f)
	}
	}
	}
	}

	macro_rules! integer {
	($Int:ident, $Uint:ident) => {
	int_base! { Binary for $Int as $Uint -> Binary }
	int_base! { Octal for $Int as $Uint -> Octal }
	int_base! { LowerHex for $Int as $Uint -> LowerHex }
	int_base! { UpperHex for $Int as $Uint -> UpperHex }
	radix_fmt! { $Int as $Int, fmt_int }
	debug! { $Int }

	int_base! { Binary for $Uint as $Uint -> Binary }
	int_base! { Octal for $Uint as $Uint -> Octal }
	int_base! { LowerHex for $Uint as $Uint -> LowerHex }
	int_base! { UpperHex for $Uint as $Uint -> UpperHex }
	radix_fmt! { $Uint as $Uint, fmt_int }
	debug! { $Uint }
	}
	}
	integer! { isize, usize }
	integer! { i8, u8 }
	integer! { i16, u16 }
	integer! { i32, u32 }
	integer! { i64, u64 }

	const DEC_DIGITS_LUT: &'static[u8] =
	b"0001020304050607080910111213141516171819\
	2021222324252627282930313233343536373839\
	4041424344454647484950515253545556575859\
	6061626364656667686970717273747576777879\
	8081828384858687888990919293949596979899";

	macro_rules! impl_Display {
	($($t:ident),*: $conv_fn:ident) => ($(
	#[stable(feature = "rust1", since = "1.0.0")]
	impl fmt::Display for $t {
	#[allow(unused_comparisons)]
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
	let is_nonnegative = *self >= 0;
	let mut n = if is_nonnegative {
	self.$conv_fn()
	} else {
	// convert the negative num to positive by summing 1 to it's 2 complement
	(!self.$conv_fn()).wrapping_add(1)
	};
	let mut buf: [u8; 20] = unsafe { mem::uninitialized() };
	let mut curr = buf.len() as isize;
	let buf_ptr = buf.as_mut_ptr();
	let lut_ptr = DEC_DIGITS_LUT.as_ptr();

	unsafe {
	// eagerly decode 4 characters at a time
	if <$t>::max_value() as u64 >= 10000 {
	while n >= 10000 {
	let rem = (n % 10000) as isize;
	n /= 10000;

	let d1 = (rem / 100) << 1;
	let d2 = (rem % 100) << 1;
	curr -= 4;
	ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
	ptr::copy_nonoverlapping(lut_ptr.offset(d2), buf_ptr.offset(curr + 2), 2);
	}
	}

	// if we reach here numbers are <= 9999, so at most 4 chars long
	let mut n = n as isize; // possibly reduce 64bit math

	// decode 2 more chars, if > 2 chars
	if n >= 100 {
	let d1 = (n % 100) << 1;
	n /= 100;
	curr -= 2;
	ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
	}

	// decode last 1 or 2 chars
	if n < 10 {
	curr -= 1;
	*buf_ptr.offset(curr) = (n as u8) + 48;
	} else {
	let d1 = n << 1;
	curr -= 2;
	ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
	}
	}

	let buf_slice = unsafe {
	str::from_utf8_unchecked(
	slice::from_raw_parts(buf_ptr.offset(curr), buf.len() - curr as usize))
	};
	f.pad_integral(is_nonnegative, "", buf_slice)
	}
	})*);
	}

	impl_Display!(i8, u8, i16, u16, i32, u32: to_u32);
	impl_Display!(i64, u64: to_u64);
	#[cfg(target_pointer_width = "32")]
	impl_Display!(isize, usize: to_u32);
	#[cfg(target_pointer_width = "64")]
	impl_Display!(isize, usize: to_u64);