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Source file src/strconv/makeisprint.go

Documentation: strconv

  // Copyright 2012 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.
  
  // +build ignore
  
  //
  // usage:
  //
  // go run makeisprint.go -output isprint.go
  //
  
  package main
  
  import (
  	"bytes"
  	"flag"
  	"fmt"
  	"go/format"
  	"io/ioutil"
  	"log"
  	"unicode"
  )
  
  var filename = flag.String("output", "isprint.go", "output file name")
  
  var (
  	range16  []uint16
  	except16 []uint16
  	range32  []uint32
  	except32 []uint32
  )
  
  // bsearch16 returns the smallest i such that a[i] >= x.
  // If there is no such i, bsearch16 returns len(a).
  func bsearch16(a []uint16, x uint16) int {
  	i, j := 0, len(a)
  	for i < j {
  		h := i + (j-i)/2
  		if a[h] < x {
  			i = h + 1
  		} else {
  			j = h
  		}
  	}
  	return i
  }
  
  // bsearch32 returns the smallest i such that a[i] >= x.
  // If there is no such i, bsearch32 returns len(a).
  func bsearch32(a []uint32, x uint32) int {
  	i, j := 0, len(a)
  	for i < j {
  		h := i + (j-i)/2
  		if a[h] < x {
  			i = h + 1
  		} else {
  			j = h
  		}
  	}
  	return i
  }
  
  func isPrint(r rune) bool {
  	// Same algorithm, either on uint16 or uint32 value.
  	// First, find first i such that rang[i] >= x.
  	// This is the index of either the start or end of a pair that might span x.
  	// The start is even (rang[i&^1]) and the end is odd (rang[i|1]).
  	// If we find x in a range, make sure x is not in exception list.
  
  	if 0 <= r && r < 1<<16 {
  		rr, rang, except := uint16(r), range16, except16
  		i := bsearch16(rang, rr)
  		if i >= len(rang) || rr < rang[i&^1] || rang[i|1] < rr {
  			return false
  		}
  		j := bsearch16(except, rr)
  		return j >= len(except) || except[j] != rr
  	}
  
  	rr, rang, except := uint32(r), range32, except32
  	i := bsearch32(rang, rr)
  	if i >= len(rang) || rr < rang[i&^1] || rang[i|1] < rr {
  		return false
  	}
  	j := bsearch32(except, rr)
  	return j >= len(except) || except[j] != rr
  }
  
  func scan(min, max rune) (rang, except []uint32) {
  	lo := rune(-1)
  	for i := min; ; i++ {
  		if (i > max || !unicode.IsPrint(i)) && lo >= 0 {
  			// End range, but avoid flip flop.
  			if i+1 <= max && unicode.IsPrint(i+1) {
  				except = append(except, uint32(i))
  				continue
  			}
  			rang = append(rang, uint32(lo), uint32(i-1))
  			lo = -1
  		}
  		if i > max {
  			break
  		}
  		if lo < 0 && unicode.IsPrint(i) {
  			lo = i
  		}
  	}
  	return
  }
  
  func to16(x []uint32) []uint16 {
  	var y []uint16
  	for _, v := range x {
  		if uint32(uint16(v)) != v {
  			panic("bad 32->16 conversion")
  		}
  		y = append(y, uint16(v))
  	}
  	return y
  }
  
  func main() {
  	flag.Parse()
  
  	rang, except := scan(0, 0xFFFF)
  	range16 = to16(rang)
  	except16 = to16(except)
  	range32, except32 = scan(0x10000, unicode.MaxRune)
  
  	for i := rune(0); i <= unicode.MaxRune; i++ {
  		if isPrint(i) != unicode.IsPrint(i) {
  			log.Fatalf("%U: isPrint=%v, want %v\n", i, isPrint(i), unicode.IsPrint(i))
  		}
  	}
  
  	var buf bytes.Buffer
  
  	fmt.Fprintf(&buf, `// Copyright 2013 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.`+"\n\n")
  	fmt.Fprintf(&buf, "// DO NOT EDIT.  GENERATED BY\n")
  	fmt.Fprintf(&buf, "//     go run makeisprint.go -output isprint.go\n\n")
  	fmt.Fprintf(&buf, "package strconv\n\n")
  
  	fmt.Fprintf(&buf, "// (%d+%d+%d)*2 + (%d)*4 = %d bytes\n\n",
  		len(range16), len(except16), len(except32),
  		len(range32),
  		(len(range16)+len(except16)+len(except32))*2+
  			(len(range32))*4)
  
  	fmt.Fprintf(&buf, "var isPrint16 = []uint16{\n")
  	for i := 0; i < len(range16); i += 2 {
  		fmt.Fprintf(&buf, "\t%#04x, %#04x,\n", range16[i], range16[i+1])
  	}
  	fmt.Fprintf(&buf, "}\n\n")
  
  	fmt.Fprintf(&buf, "var isNotPrint16 = []uint16{\n")
  	for _, r := range except16 {
  		fmt.Fprintf(&buf, "\t%#04x,\n", r)
  	}
  	fmt.Fprintf(&buf, "}\n\n")
  
  	fmt.Fprintf(&buf, "var isPrint32 = []uint32{\n")
  	for i := 0; i < len(range32); i += 2 {
  		fmt.Fprintf(&buf, "\t%#06x, %#06x,\n", range32[i], range32[i+1])
  	}
  	fmt.Fprintf(&buf, "}\n\n")
  
  	fmt.Fprintf(&buf, "var isNotPrint32 = []uint16{ // add 0x10000 to each entry\n")
  	for _, r := range except32 {
  		if r >= 0x20000 {
  			log.Fatalf("%U too big for isNotPrint32\n", r)
  		}
  		fmt.Fprintf(&buf, "\t%#04x,\n", r-0x10000)
  	}
  	fmt.Fprintf(&buf, "}\n\n")
  
  	// The list of graphic but not "printable" runes is short. Just make one easy table.
  	fmt.Fprintf(&buf, "// isGraphic lists the graphic runes not matched by IsPrint.\n")
  	fmt.Fprintf(&buf, "var isGraphic = []uint16{\n")
  	for r := rune(0); r <= unicode.MaxRune; r++ {
  		if unicode.IsPrint(r) != unicode.IsGraphic(r) {
  			// Sanity check.
  			if !unicode.IsGraphic(r) {
  				log.Fatalf("%U is printable but not graphic\n", r)
  			}
  			if r > 0xFFFF { // We expect only 16-bit values.
  				log.Fatalf("%U too big for isGraphic\n", r)
  			}
  			fmt.Fprintf(&buf, "\t%#04x,\n", r)
  		}
  	}
  	fmt.Fprintf(&buf, "}\n")
  
  	data, err := format.Source(buf.Bytes())
  	if err != nil {
  		log.Fatal(err)
  	}
  	err = ioutil.WriteFile(*filename, data, 0644)
  	if err != nil {
  		log.Fatal(err)
  	}
  }
  

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