libgo: Update to Go 1.3 release.

[official-gcc.git] / libgo / go / fmt / format.go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package fmt

import (
        "math"
        "strconv"
        "unicode/utf8"
)

const (
        // %b of an int64, plus a sign.
        // Hex can add 0x and we handle it specially.
        nByte = 65

        ldigits = "0123456789abcdef"
        udigits = "0123456789ABCDEF"
)

const (
        signed   = true
        unsigned = false
)

var padZeroBytes = make([]byte, nByte)
var padSpaceBytes = make([]byte, nByte)

func init() {
        for i := 0; i < nByte; i++ {
                padZeroBytes[i] = '0'
                padSpaceBytes[i] = ' '
        }
}

// A fmt is the raw formatter used by Printf etc.
// It prints into a buffer that must be set up separately.
type fmt struct {
        intbuf [nByte]byte
        buf    *buffer
        // width, precision
        wid  int
        prec int
        // flags
        widPresent  bool
        precPresent bool
        minus       bool
        plus        bool
        sharp       bool
        space       bool
        unicode     bool
        uniQuote    bool // Use 'x'= prefix for %U if printable.
        zero        bool
}

func (f *fmt) clearflags() {
        f.wid = 0
        f.widPresent = false
        f.prec = 0
        f.precPresent = false
        f.minus = false
        f.plus = false
        f.sharp = false
        f.space = false
        f.unicode = false
        f.uniQuote = false
        f.zero = false
}

func (f *fmt) init(buf *buffer) {
        f.buf = buf
        f.clearflags()
}

// computePadding computes left and right padding widths (only one will be non-zero).
func (f *fmt) computePadding(width int) (padding []byte, leftWidth, rightWidth int) {
        left := !f.minus
        w := f.wid
        if w < 0 {
                left = false
                w = -w
        }
        w -= width
        if w > 0 {
                if left && f.zero {
                        return padZeroBytes, w, 0
                }
                if left {
                        return padSpaceBytes, w, 0
                } else {
                        // can't be zero padding on the right
                        return padSpaceBytes, 0, w
                }
        }
        return
}

// writePadding generates n bytes of padding.
func (f *fmt) writePadding(n int, padding []byte) {
        for n > 0 {
                m := n
                if m > nByte {
                        m = nByte
                }
                f.buf.Write(padding[0:m])
                n -= m
        }
}

// pad appends b to f.buf, padded on left (w > 0) or right (w < 0 or f.minus).
func (f *fmt) pad(b []byte) {
        if !f.widPresent || f.wid == 0 {
                f.buf.Write(b)
                return
        }
        padding, left, right := f.computePadding(len(b))
        if left > 0 {
                f.writePadding(left, padding)
        }
        f.buf.Write(b)
        if right > 0 {
                f.writePadding(right, padding)
        }
}

// padString appends s to buf, padded on left (w > 0) or right (w < 0 or f.minus).
func (f *fmt) padString(s string) {
        if !f.widPresent || f.wid == 0 {
                f.buf.WriteString(s)
                return
        }
        padding, left, right := f.computePadding(utf8.RuneCountInString(s))
        if left > 0 {
                f.writePadding(left, padding)
        }
        f.buf.WriteString(s)
        if right > 0 {
                f.writePadding(right, padding)
        }
}

var (
        trueBytes  = []byte("true")
        falseBytes = []byte("false")
)

// fmt_boolean formats a boolean.
func (f *fmt) fmt_boolean(v bool) {
        if v {
                f.pad(trueBytes)
        } else {
                f.pad(falseBytes)
        }
}

// integer; interprets prec but not wid.  Once formatted, result is sent to pad()
// and then flags are cleared.
func (f *fmt) integer(a int64, base uint64, signedness bool, digits string) {
        // precision of 0 and value of 0 means "print nothing"
        if f.precPresent && f.prec == 0 && a == 0 {
                return
        }

        var buf []byte = f.intbuf[0:]
        if f.widPresent {
                width := f.wid
                if base == 16 && f.sharp {
                        // Also adds "0x".
                        width += 2
                }
                if width > nByte {
                        // We're going to need a bigger boat.
                        buf = make([]byte, width)
                }
        }

        negative := signedness == signed && a < 0
        if negative {
                a = -a
        }

        // two ways to ask for extra leading zero digits: %.3d or %03d.
        // apparently the first cancels the second.
        prec := 0
        if f.precPresent {
                prec = f.prec
                f.zero = false
        } else if f.zero && f.widPresent && !f.minus && f.wid > 0 {
                prec = f.wid
                if negative || f.plus || f.space {
                        prec-- // leave room for sign
                }
        }

        // format a into buf, ending at buf[i].  (printing is easier right-to-left.)
        // a is made into unsigned ua.  we could make things
        // marginally faster by splitting the 32-bit case out into a separate
        // block but it's not worth the duplication, so ua has 64 bits.
        i := len(buf)
        ua := uint64(a)
        for ua >= base {
                i--
                buf[i] = digits[ua%base]
                ua /= base
        }
        i--
        buf[i] = digits[ua]
        for i > 0 && prec > len(buf)-i {
                i--
                buf[i] = '0'
        }

        // Various prefixes: 0x, -, etc.
        if f.sharp {
                switch base {
                case 8:
                        if buf[i] != '0' {
                                i--
                                buf[i] = '0'
                        }
                case 16:
                        i--
                        buf[i] = 'x' + digits[10] - 'a'
                        i--
                        buf[i] = '0'
                }
        }
        if f.unicode {
                i--
                buf[i] = '+'
                i--
                buf[i] = 'U'
        }

        if negative {
                i--
                buf[i] = '-'
        } else if f.plus {
                i--
                buf[i] = '+'
        } else if f.space {
                i--
                buf[i] = ' '
        }

        // If we want a quoted char for %#U, move the data up to make room.
        if f.unicode && f.uniQuote && a >= 0 && a <= utf8.MaxRune && strconv.IsPrint(rune(a)) {
                runeWidth := utf8.RuneLen(rune(a))
                width := 1 + 1 + runeWidth + 1 // space, quote, rune, quote
                copy(buf[i-width:], buf[i:])   // guaranteed to have enough room.
                i -= width
                // Now put " 'x'" at the end.
                j := len(buf) - width
                buf[j] = ' '
                j++
                buf[j] = '\''
                j++
                utf8.EncodeRune(buf[j:], rune(a))
                j += runeWidth
                buf[j] = '\''
        }

        f.pad(buf[i:])
}

// truncate truncates the string to the specified precision, if present.
func (f *fmt) truncate(s string) string {
        if f.precPresent && f.prec < utf8.RuneCountInString(s) {
                n := f.prec
                for i := range s {
                        if n == 0 {
                                s = s[:i]
                                break
                        }
                        n--
                }
        }
        return s
}

// fmt_s formats a string.
func (f *fmt) fmt_s(s string) {
        s = f.truncate(s)
        f.padString(s)
}

// fmt_sbx formats a string or byte slice as a hexadecimal encoding of its bytes.
func (f *fmt) fmt_sbx(s string, b []byte, digits string) {
        n := len(b)
        if b == nil {
                n = len(s)
        }
        x := digits[10] - 'a' + 'x'
        // TODO: Avoid buffer by pre-padding.
        var buf []byte
        for i := 0; i < n; i++ {
                if i > 0 && f.space {
                        buf = append(buf, ' ')
                }
                if f.sharp {
                        buf = append(buf, '0', x)
                }
                var c byte
                if b == nil {
                        c = s[i]
                } else {
                        c = b[i]
                }
                buf = append(buf, digits[c>>4], digits[c&0xF])
        }
        f.pad(buf)
}

// fmt_sx formats a string as a hexadecimal encoding of its bytes.
func (f *fmt) fmt_sx(s, digits string) {
        f.fmt_sbx(s, nil, digits)
}

// fmt_bx formats a byte slice as a hexadecimal encoding of its bytes.
func (f *fmt) fmt_bx(b []byte, digits string) {
        f.fmt_sbx("", b, digits)
}

// fmt_q formats a string as a double-quoted, escaped Go string constant.
func (f *fmt) fmt_q(s string) {
        s = f.truncate(s)
        var quoted string
        if f.sharp && strconv.CanBackquote(s) {
                quoted = "`" + s + "`"
        } else {
                if f.plus {
                        quoted = strconv.QuoteToASCII(s)
                } else {
                        quoted = strconv.Quote(s)
                }
        }
        f.padString(quoted)
}

// fmt_qc formats the integer as a single-quoted, escaped Go character constant.
// If the character is not valid Unicode, it will print '\ufffd'.
func (f *fmt) fmt_qc(c int64) {
        var quoted []byte
        if f.plus {
                quoted = strconv.AppendQuoteRuneToASCII(f.intbuf[0:0], rune(c))
        } else {
                quoted = strconv.AppendQuoteRune(f.intbuf[0:0], rune(c))
        }
        f.pad(quoted)
}

// floating-point

func doPrec(f *fmt, def int) int {
        if f.precPresent {
                return f.prec
        }
        return def
}

// formatFloat formats a float64; it is an efficient equivalent to  f.pad(strconv.FormatFloat()...).
func (f *fmt) formatFloat(v float64, verb byte, prec, n int) {
        // Format number, reserving space for leading + sign if needed.
        num := strconv.AppendFloat(f.intbuf[0:1], v, verb, prec, n)
        if num[1] == '-' || num[1] == '+' {
                num = num[1:]
        } else {
                num[0] = '+'
        }
        // Special handling for infinity, which doesn't look like a number so shouldn't be padded with zeros.
        if math.IsInf(v, 0) {
                if f.zero {
                        defer func() { f.zero = true }()
                        f.zero = false
                }
        }
        // num is now a signed version of the number.
        // If we're zero padding, want the sign before the leading zeros.
        // Achieve this by writing the sign out and then padding the unsigned number.
        if f.zero && f.widPresent && f.wid > len(num) {
                if f.space && v >= 0 {
                        f.buf.WriteByte(' ') // This is what C does: even with zero, f.space means space.
                        f.wid--
                } else if f.plus || v < 0 {
                        f.buf.WriteByte(num[0])
                        f.wid--
                }
                f.pad(num[1:])
                return
        }
        // f.space says to replace a leading + with a space.
        if f.space && num[0] == '+' {
                num[0] = ' '
                f.pad(num)
                return
        }
        // Now we know the sign is attached directly to the number, if present at all.
        // We want a sign if asked for, if it's negative, or if it's infinity (+Inf vs. -Inf).
        if f.plus || num[0] == '-' || math.IsInf(v, 0) {
                f.pad(num)
                return
        }
        // No sign to show and the number is positive; just print the unsigned number.
        f.pad(num[1:])
}

// fmt_e64 formats a float64 in the form -1.23e+12.
func (f *fmt) fmt_e64(v float64) { f.formatFloat(v, 'e', doPrec(f, 6), 64) }

// fmt_E64 formats a float64 in the form -1.23E+12.
func (f *fmt) fmt_E64(v float64) { f.formatFloat(v, 'E', doPrec(f, 6), 64) }

// fmt_f64 formats a float64 in the form -1.23.
func (f *fmt) fmt_f64(v float64) { f.formatFloat(v, 'f', doPrec(f, 6), 64) }

// fmt_g64 formats a float64 in the 'f' or 'e' form according to size.
func (f *fmt) fmt_g64(v float64) { f.formatFloat(v, 'g', doPrec(f, -1), 64) }

// fmt_G64 formats a float64 in the 'f' or 'E' form according to size.
func (f *fmt) fmt_G64(v float64) { f.formatFloat(v, 'G', doPrec(f, -1), 64) }

// fmt_fb64 formats a float64 in the form -123p3 (exponent is power of 2).
func (f *fmt) fmt_fb64(v float64) { f.formatFloat(v, 'b', 0, 64) }

// float32
// cannot defer to float64 versions
// because it will get rounding wrong in corner cases.

// fmt_e32 formats a float32 in the form -1.23e+12.
func (f *fmt) fmt_e32(v float32) { f.formatFloat(float64(v), 'e', doPrec(f, 6), 32) }

// fmt_E32 formats a float32 in the form -1.23E+12.
func (f *fmt) fmt_E32(v float32) { f.formatFloat(float64(v), 'E', doPrec(f, 6), 32) }

// fmt_f32 formats a float32 in the form -1.23.
func (f *fmt) fmt_f32(v float32) { f.formatFloat(float64(v), 'f', doPrec(f, 6), 32) }

// fmt_g32 formats a float32 in the 'f' or 'e' form according to size.
func (f *fmt) fmt_g32(v float32) { f.formatFloat(float64(v), 'g', doPrec(f, -1), 32) }

// fmt_G32 formats a float32 in the 'f' or 'E' form according to size.
func (f *fmt) fmt_G32(v float32) { f.formatFloat(float64(v), 'G', doPrec(f, -1), 32) }

// fmt_fb32 formats a float32 in the form -123p3 (exponent is power of 2).
func (f *fmt) fmt_fb32(v float32) { f.formatFloat(float64(v), 'b', 0, 32) }

// fmt_c64 formats a complex64 according to the verb.
func (f *fmt) fmt_c64(v complex64, verb rune) {
        f.fmt_complex(float64(real(v)), float64(imag(v)), 32, verb)
}

// fmt_c128 formats a complex128 according to the verb.
func (f *fmt) fmt_c128(v complex128, verb rune) {
        f.fmt_complex(real(v), imag(v), 64, verb)
}

// fmt_complex formats a complex number as (r+ji).
func (f *fmt) fmt_complex(r, j float64, size int, verb rune) {
        f.buf.WriteByte('(')
        oldPlus := f.plus
        oldSpace := f.space
        oldWid := f.wid
        for i := 0; ; i++ {
                switch verb {
                case 'b':
                        f.formatFloat(r, 'b', 0, size)
                case 'e':
                        f.formatFloat(r, 'e', doPrec(f, 6), size)
                case 'E':
                        f.formatFloat(r, 'E', doPrec(f, 6), size)
                case 'f', 'F':
                        f.formatFloat(r, 'f', doPrec(f, 6), size)
                case 'g':
                        f.formatFloat(r, 'g', doPrec(f, -1), size)
                case 'G':
                        f.formatFloat(r, 'G', doPrec(f, -1), size)
                }
                if i != 0 {
                        break
                }
                // Imaginary part always has a sign.
                f.plus = true
                f.space = false
                f.wid = oldWid
                r = j
        }
        f.space = oldSpace
        f.plus = oldPlus
        f.wid = oldWid
        f.buf.Write(irparenBytes)
}