基于Golang编写的词法分析

package main

import (
   "bufio"
   "fmt"
   "io"
   "os"
)

var key = make(map[string]int)

var (
   FileName = "main.cpp"

   InputFile *os.File

   InputError error
   status     = false
)

//初始化,特征序
func keyInit() {
   key["if"] = 1
   key["int"] = 1
   key["for"] = 1
   key["while"] = 1
   key["do"] = 1
   key["return"] = 1
   key["break"] = 1
   key["continue"] = 1
   key["main"] = 2
   key["("] = 5
   key[")"] = 5
   key["{"] = 5
   key["}"] = 5
   key[","] = 5
   key["="] = 4
   key["+"] = 4
   key["-"] = 4
   key["*"] = 4
   key["/"] = 4
   key[";"] = 5
   key[">"] = 4
   key["<"] = 4
}

func main() {

   InputFile, InputError = os.OpenFile(FileName, os.O_RDWR, 0644)

   if InputError != nil {
      fmt.Println("Error")
      return
   }
   defer InputFile.Close()

   inputReader := bufio.NewReader(InputFile)

   //初始化
   keyInit()

   judgeMent()

   for {
      inputString, readerError := inputReader.ReadString('\n') //我们将inputReader里面的字符串按行进行读取。
      judgeToken(inputString)
      if readerError == io.EOF {
         return
      }
   }

}

func judgeMent() {
   InputFile, InputError = os.OpenFile(FileName, os.O_RDWR, 0644)
   defer InputFile.Close()
   inputReader := bufio.NewReader(InputFile)
   status := make([]uint8, 0, 0)
   for {
      inputString, readerError := inputReader.ReadByte() //我们将inputReader里面的字符串按行进行读取。
      if inputString == uint8('(') || inputString == uint8('{') {
         status = append(status, inputString)
      } else if (inputString == uint8(')') && status[len(status)-1] == uint8('(')) || (inputString == uint8('}') && status[len(status)-1] == uint8('{')) {
         status = append(status[:len(status)-1])
      }
      if readerError == io.EOF {
         break
      }
   }
   if len(status) != 0 {
      panic("符号不匹配")
   }
}

func judgeToken(line string) {

   token := ""

   for i := 0; i < len(line); i++ {

      if status {
         if i+1 < len(line) && line[i] == uint8('*') && line[i+1] == uint8('/') {
            status = false
            i++
         }
         continue
      }

      if i+1 < len(line) && line[i] == uint8('/') && line[i+1] == uint8('/') {
         break
      } else if i+1 < len(line) && line[i] == uint8('/') && line[i+1] == uint8('*') {
         status = true
         i++
         continue
      }

      if isLetter(line[i]) {
         token += string(line[i])

         //得到关键字
         if _, ok := key[token]; ok && !isLetter(line[i+1]) && !isNumber(line[i+1]) {
            Display(key[token], token)
            token = ""
         }
      } else if line[i] == uint8('(') || line[i] == uint8(')') {
         Display(key[string(line[i])], string(line[i]))
      } else if line[i] == uint8('{') || line[i] == uint8('}') {
         Display(key[string(line[i])], string(line[i]))
      } else if (line[i] == uint8(' ') || line[i] == uint8('\n')) && token != "" {
         if token[0] == uint8('-') && isNumber(token[1]) || isNumber(token[0]) {
            Display(3, token)
         } else {
            Display(2, token)
         }
         token = ""
      } else if line[i] == uint8(',') {
         Display(2, token)
         token = ""
         Display(key[string(line[i])], string(line[i]))
      } else if isOperation(line[i]) || line[i] == uint8(';') { //处理操作符号前面的类型
         if token != "" {
            if _, ok := key[token]; ok {
               Display(key[token], token)
            } else {
               if token[0] == uint8('-') && isNumber(token[1]) || isNumber(token[0]) {
                  Display(3, token)
               } else {
                  Display(2, token)
               }
            }
            token = ""
         }
         //得到/=，*=，+=，-=
         if isOperation(line[i]) {
            if line[i+1] == '=' {
               Display(4, string(line[i])+string(line[i+1]))
               i++
            } else {
               Display(key[string(line[i])], string(line[i]))
            }
            if line[i+1] == '-' {
               token += string(line[i+1])
               Display(key[string(line[i])], string(line[i]))
               i++
            }
         } else {
            Display(key[string(line[i])], string(line[i]))
         }

      } else if isNumber(line[i]) {
         token += string(line[i])
         if line[i+1] == uint8('.') && isNumberString(token) {
            token += string(line[i+1])
            i++
         }
         if line[i+1] == uint8('E') {
            token += string(line[i+1])
            i++
            if line[i+1] == uint8('-') {
               token += string(line[i+1])
               i++
            }
         }
      }
   }

}

//确定得到的token是整数类型
func isNumber(token uint8) bool {
   if token <= uint8('9') && token >= uint8('0') {
      return true
   }
   return false
}

//确定是范围内a-z或者A-Z

func isLetter(token uint8) bool {
   if (token <= uint8('z') && token >= uint8('a')) || (token <= uint8('Z') && token >= uint8('A')) {
      return true
   }
   return false
}

//提取格式 fmt.Printf("(%d,\"%s\")\n", key[string(line[i])], string(line[i]))
func Display(value int, key string) {
   fmt.Printf("(%d,\"%s\")\n", value, key)
}

//确保是操作符号
func isOperation(token uint8) bool {
   if token == uint8('/') || token == uint8('*') || token == uint8('+') || token == uint8('-') || token == uint8('=') {
      return true
   }
   if token == uint8('>') || token == uint8('<') || token == uint8('=') {
      return true
   }
   return false
}

func isNumberString(token string) bool {
   for i := 0; i < len(token); i++ {
      if !isNumber(token[i]) {
         return false
      }
   }
   return true
}