github.com/Enlighten-Fund/go-ethereum@v1.9.7/core/asm/compiler.go (about)

     1  // Copyright 2017 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package asm
    18  
    19  import (
    20  	"fmt"
    21  	"math/big"
    22  	"os"
    23  	"strings"
    24  
    25  	"github.com/ethereum/go-ethereum/common/math"
    26  	"github.com/ethereum/go-ethereum/core/vm"
    27  )
    28  
    29  // Compiler contains information about the parsed source
    30  // and holds the tokens for the program.
    31  type Compiler struct {
    32  	tokens []token
    33  	binary []interface{}
    34  
    35  	labels map[string]int
    36  
    37  	pc, pos int
    38  
    39  	debug bool
    40  }
    41  
    42  // newCompiler returns a new allocated compiler.
    43  func NewCompiler(debug bool) *Compiler {
    44  	return &Compiler{
    45  		labels: make(map[string]int),
    46  		debug:  debug,
    47  	}
    48  }
    49  
    50  // Feed feeds tokens in to ch and are interpreted by
    51  // the compiler.
    52  //
    53  // feed is the first pass in the compile stage as it
    54  // collects the used labels in the program and keeps a
    55  // program counter which is used to determine the locations
    56  // of the jump dests. The labels can than be used in the
    57  // second stage to push labels and determine the right
    58  // position.
    59  func (c *Compiler) Feed(ch <-chan token) {
    60  	var prev token
    61  	for i := range ch {
    62  		switch i.typ {
    63  		case number:
    64  			num := math.MustParseBig256(i.text).Bytes()
    65  			if len(num) == 0 {
    66  				num = []byte{0}
    67  			}
    68  			c.pc += len(num)
    69  		case stringValue:
    70  			c.pc += len(i.text) - 2
    71  		case element:
    72  			c.pc++
    73  		case labelDef:
    74  			c.labels[i.text] = c.pc
    75  			c.pc++
    76  		case label:
    77  			c.pc += 4
    78  			if prev.typ == element && isJump(prev.text) {
    79  				c.pc++
    80  			}
    81  		}
    82  
    83  		c.tokens = append(c.tokens, i)
    84  		prev = i
    85  	}
    86  	if c.debug {
    87  		fmt.Fprintln(os.Stderr, "found", len(c.labels), "labels")
    88  	}
    89  }
    90  
    91  // Compile compiles the current tokens and returns a
    92  // binary string that can be interpreted by the EVM
    93  // and an error if it failed.
    94  //
    95  // compile is the second stage in the compile phase
    96  // which compiles the tokens to EVM instructions.
    97  func (c *Compiler) Compile() (string, []error) {
    98  	var errors []error
    99  	// continue looping over the tokens until
   100  	// the stack has been exhausted.
   101  	for c.pos < len(c.tokens) {
   102  		if err := c.compileLine(); err != nil {
   103  			errors = append(errors, err)
   104  		}
   105  	}
   106  
   107  	// turn the binary to hex
   108  	var bin string
   109  	for _, v := range c.binary {
   110  		switch v := v.(type) {
   111  		case vm.OpCode:
   112  			bin += fmt.Sprintf("%x", []byte{byte(v)})
   113  		case []byte:
   114  			bin += fmt.Sprintf("%x", v)
   115  		}
   116  	}
   117  	return bin, errors
   118  }
   119  
   120  // next returns the next token and increments the
   121  // position.
   122  func (c *Compiler) next() token {
   123  	token := c.tokens[c.pos]
   124  	c.pos++
   125  	return token
   126  }
   127  
   128  // compileLine compiles a single line instruction e.g.
   129  // "push 1", "jump @label".
   130  func (c *Compiler) compileLine() error {
   131  	n := c.next()
   132  	if n.typ != lineStart {
   133  		return compileErr(n, n.typ.String(), lineStart.String())
   134  	}
   135  
   136  	lvalue := c.next()
   137  	switch lvalue.typ {
   138  	case eof:
   139  		return nil
   140  	case element:
   141  		if err := c.compileElement(lvalue); err != nil {
   142  			return err
   143  		}
   144  	case labelDef:
   145  		c.compileLabel()
   146  	case lineEnd:
   147  		return nil
   148  	default:
   149  		return compileErr(lvalue, lvalue.text, fmt.Sprintf("%v or %v", labelDef, element))
   150  	}
   151  
   152  	if n := c.next(); n.typ != lineEnd {
   153  		return compileErr(n, n.text, lineEnd.String())
   154  	}
   155  
   156  	return nil
   157  }
   158  
   159  // compileNumber compiles the number to bytes
   160  func (c *Compiler) compileNumber(element token) (int, error) {
   161  	num := math.MustParseBig256(element.text).Bytes()
   162  	if len(num) == 0 {
   163  		num = []byte{0}
   164  	}
   165  	c.pushBin(num)
   166  	return len(num), nil
   167  }
   168  
   169  // compileElement compiles the element (push & label or both)
   170  // to a binary representation and may error if incorrect statements
   171  // where fed.
   172  func (c *Compiler) compileElement(element token) error {
   173  	// check for a jump. jumps must be read and compiled
   174  	// from right to left.
   175  	if isJump(element.text) {
   176  		rvalue := c.next()
   177  		switch rvalue.typ {
   178  		case number:
   179  			// TODO figure out how to return the error properly
   180  			c.compileNumber(rvalue)
   181  		case stringValue:
   182  			// strings are quoted, remove them.
   183  			c.pushBin(rvalue.text[1 : len(rvalue.text)-2])
   184  		case label:
   185  			c.pushBin(vm.PUSH4)
   186  			pos := big.NewInt(int64(c.labels[rvalue.text])).Bytes()
   187  			pos = append(make([]byte, 4-len(pos)), pos...)
   188  			c.pushBin(pos)
   189  		case lineEnd:
   190  			c.pos--
   191  		default:
   192  			return compileErr(rvalue, rvalue.text, "number, string or label")
   193  		}
   194  		// push the operation
   195  		c.pushBin(toBinary(element.text))
   196  		return nil
   197  	} else if isPush(element.text) {
   198  		// handle pushes. pushes are read from left to right.
   199  		var value []byte
   200  
   201  		rvalue := c.next()
   202  		switch rvalue.typ {
   203  		case number:
   204  			value = math.MustParseBig256(rvalue.text).Bytes()
   205  			if len(value) == 0 {
   206  				value = []byte{0}
   207  			}
   208  		case stringValue:
   209  			value = []byte(rvalue.text[1 : len(rvalue.text)-1])
   210  		case label:
   211  			value = big.NewInt(int64(c.labels[rvalue.text])).Bytes()
   212  			value = append(make([]byte, 4-len(value)), value...)
   213  		default:
   214  			return compileErr(rvalue, rvalue.text, "number, string or label")
   215  		}
   216  
   217  		if len(value) > 32 {
   218  			return fmt.Errorf("%d type error: unsupported string or number with size > 32", rvalue.lineno)
   219  		}
   220  
   221  		c.pushBin(vm.OpCode(int(vm.PUSH1) - 1 + len(value)))
   222  		c.pushBin(value)
   223  	} else {
   224  		c.pushBin(toBinary(element.text))
   225  	}
   226  
   227  	return nil
   228  }
   229  
   230  // compileLabel pushes a jumpdest to the binary slice.
   231  func (c *Compiler) compileLabel() {
   232  	c.pushBin(vm.JUMPDEST)
   233  }
   234  
   235  // pushBin pushes the value v to the binary stack.
   236  func (c *Compiler) pushBin(v interface{}) {
   237  	if c.debug {
   238  		fmt.Printf("%d: %v\n", len(c.binary), v)
   239  	}
   240  	c.binary = append(c.binary, v)
   241  }
   242  
   243  // isPush returns whether the string op is either any of
   244  // push(N).
   245  func isPush(op string) bool {
   246  	return strings.ToUpper(op) == "PUSH"
   247  }
   248  
   249  // isJump returns whether the string op is jump(i)
   250  func isJump(op string) bool {
   251  	return strings.ToUpper(op) == "JUMPI" || strings.ToUpper(op) == "JUMP"
   252  }
   253  
   254  // toBinary converts text to a vm.OpCode
   255  func toBinary(text string) vm.OpCode {
   256  	return vm.StringToOp(strings.ToUpper(text))
   257  }
   258  
   259  type compileError struct {
   260  	got  string
   261  	want string
   262  
   263  	lineno int
   264  }
   265  
   266  func (err compileError) Error() string {
   267  	return fmt.Sprintf("%d syntax error: unexpected %v, expected %v", err.lineno, err.got, err.want)
   268  }
   269  
   270  func compileErr(c token, got, want string) error {
   271  	return compileError{
   272  		got:    got,
   273  		want:   want,
   274  		lineno: c.lineno,
   275  	}
   276  }