gen.go

     1  // Copyright 2019 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  //go:build ignore
     6  
     7  // Gen generates sais2.go by duplicating functions in sais.go
     8  // using different input types.
     9  // See the comment at the top of sais.go for details.
    10  package main
    11  
    12  import (
    13  	"bytes"
    14  	"log"
    15  	"os"
    16  	"strings"
    17  )
    18  
    19  func main() {
    20  	log.SetPrefix("gen: ")
    21  	log.SetFlags(0)
    22  
    23  	data, err := os.ReadFile("sais.go")
    24  	if err != nil {
    25  		log.Fatal(err)
    26  	}
    27  
    28  	x := bytes.Index(data, []byte("\n\n"))
    29  	if x < 0 {
    30  		log.Fatal("cannot find blank line after copyright comment")
    31  	}
    32  
    33  	var buf bytes.Buffer
    34  	buf.Write(data[:x])
    35  	buf.WriteString("\n\n// Code generated by go generate; DO NOT EDIT.\n\npackage suffixarray\n")
    36  
    37  	for {
    38  		x := bytes.Index(data, []byte("\nfunc "))
    39  		if x < 0 {
    40  			break
    41  		}
    42  		data = data[x:]
    43  		p := bytes.IndexByte(data, '(')
    44  		if p < 0 {
    45  			p = len(data)
    46  		}
    47  		name := string(data[len("\nfunc "):p])
    48  
    49  		x = bytes.Index(data, []byte("\n}\n"))
    50  		if x < 0 {
    51  			log.Fatalf("cannot find end of func %s", name)
    52  		}
    53  		fn := string(data[:x+len("\n}\n")])
    54  		data = data[x+len("\n}"):]
    55  
    56  		if strings.HasSuffix(name, "_32") {
    57  			buf.WriteString(fix32.Replace(fn))
    58  		}
    59  		if strings.HasSuffix(name, "_8_32") {
    60  			// x_8_32 -> x_8_64 done above
    61  			fn = fix8_32.Replace(stripByteOnly(fn))
    62  			buf.WriteString(fn)
    63  			buf.WriteString(fix32.Replace(fn))
    64  		}
    65  	}
    66  
    67  	if err := os.WriteFile("sais2.go", buf.Bytes(), 0666); err != nil {
    68  		log.Fatal(err)
    69  	}
    70  }
    71  
    72  var fix32 = strings.NewReplacer(
    73  	"32", "64",
    74  	"int32", "int64",
    75  )
    76  
    77  var fix8_32 = strings.NewReplacer(
    78  	"_8_32", "_32",
    79  	"byte", "int32",
    80  )
    81  
    82  func stripByteOnly(s string) string {
    83  	lines := strings.SplitAfter(s, "\n")
    84  	w := 0
    85  	for _, line := range lines {
    86  		if !strings.Contains(line, "256") && !strings.Contains(line, "byte-only") {
    87  			lines[w] = line
    88  			w++
    89  		}
    90  	}
    91  	return strings.Join(lines[:w], "")
    92  }
    93
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