example_compact_test.go

Documentation: golang.org/x/text/internal/triegen

     1  // Copyright 2014 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package triegen_test
     6  
     7  import (
     8  	"fmt"
     9  	"io"
    10  
    11  	"golang.org/x/text/internal/triegen"
    12  )
    13  
    14  func ExampleCompacter() {
    15  	t := triegen.NewTrie("root")
    16  	for r := rune(0); r < 10000; r += 64 {
    17  		t.Insert(r, 0x9015BADA55^uint64(r))
    18  	}
    19  	sz, _ := t.Gen(io.Discard)
    20  
    21  	fmt.Printf("Size normal:    %5d\n", sz)
    22  
    23  	var c myCompacter
    24  	sz, _ = t.Gen(io.Discard, triegen.Compact(&c))
    25  
    26  	fmt.Printf("Size compacted: %5d\n", sz)
    27  
    28  	// Output:
    29  	// Size normal:    81344
    30  	// Size compacted:  3224
    31  }
    32  
    33  // A myCompacter accepts a block if only the first value is given.
    34  type myCompacter []uint64
    35  
    36  func (c *myCompacter) Size(values []uint64) (sz int, ok bool) {
    37  	for _, v := range values[1:] {
    38  		if v != 0 {
    39  			return 0, false
    40  		}
    41  	}
    42  	return 8, true // the size of a uint64
    43  }
    44  
    45  func (c *myCompacter) Store(v []uint64) uint32 {
    46  	x := uint32(len(*c))
    47  	*c = append(*c, v[0])
    48  	return x
    49  }
    50  
    51  func (c *myCompacter) Print(w io.Writer) error {
    52  	fmt.Fprintln(w, "var firstValue = []uint64{")
    53  	for _, v := range *c {
    54  		fmt.Fprintf(w, "\t%#x,\n", v)
    55  	}
    56  	fmt.Fprintln(w, "}")
    57  	return nil
    58  }
    59  
    60  func (c *myCompacter) Handler() string {
    61  	return "getFirstValue"
    62  
    63  	// Where getFirstValue is included along with the generated code:
    64  	// func getFirstValue(n uint32, b byte) uint64 {
    65  	//     if b == 0x80 { // the first continuation byte
    66  	//         return firstValue[n]
    67  	//     }
    68  	//     return 0
    69  	//  }
    70  }
    71
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