common: move big integer math to common/math (#3699)

* common: remove CurrencyToString

Move denomination values to params instead.

* common: delete dead code

* common: move big integer operations to common/math

This commit consolidates all big integer operations into common/math and
adds tests and documentation.

There should be no change in semantics for BigPow, BigMin, BigMax, S256,
U256, Exp and their behaviour is now locked in by tests.

The BigD, BytesToBig and Bytes2Big functions don't provide additional
value, all uses are replaced by new(big.Int).SetBytes().

BigToBytes is now called PaddedBigBytes, its minimum output size
parameter is now specified as the number of bytes instead of bits. The
single use of this function is in the EVM's MSTORE instruction.

Big and String2Big are replaced by ParseBig, which is slightly stricter.
It previously accepted leading zeros for hexadecimal inputs but treated
decimal inputs as octal if a leading zero digit was present.

ParseUint64 is used in places where String2Big was used to decode a
uint64.

The new functions MustParseBig and MustParseUint64 are now used in many
places where parsing errors were previously ignored.

* common: delete unused big integer variables

* accounts/abi: replace uses of BytesToBig with use of encoding/binary

* common: remove BytesToBig

* common: remove Bytes2Big

* common: remove BigTrue

* cmd/utils: add BigFlag and use it for error-checked integer flags

While here, remove environment variable processing for DirectoryFlag
because we don't use it.

* core: add missing error checks in genesis block parser

* common: remove String2Big

* cmd/evm: use utils.BigFlag

* common/math: check for 256 bit overflow in ParseBig

This is supposed to prevent silent overflow/truncation of values in the
genesis block JSON. Without this check, a genesis block that set a
balance larger than 256 bits would lead to weird behaviour in the VM.

* cmd/utils: fixup import

1 files changed, 0 insertions, 155 deletions

diff --git a/common/bytes.go b/common/bytes.go
index cbceea8b5..0342083a1 100644
--- a/common/bytes.go
+++ b/common/bytes.go
@@ -18,12 +18,7 @@
 package common
 
 import (
-	"bytes"
-	"encoding/binary"
 	"encoding/hex"
-	"fmt"
-	"math/big"
-	"strings"
 )
 
 func ToHex(b []byte) string {
@@ -48,65 +43,6 @@ func FromHex(s string) []byte {
 	return nil
 }
 
-// Number to bytes
-//
-// Returns the number in bytes with the specified base
-func NumberToBytes(num interface{}, bits int) []byte {
-	buf := new(bytes.Buffer)
-	err := binary.Write(buf, binary.BigEndian, num)
-	if err != nil {
-		fmt.Println("NumberToBytes failed:", err)
-	}
-
-	return buf.Bytes()[buf.Len()-(bits/8):]
-}
-
-// Bytes to number
-//
-// Attempts to cast a byte slice to a unsigned integer
-func BytesToNumber(b []byte) uint64 {
-	var number uint64
-
-	// Make sure the buffer is 64bits
-	data := make([]byte, 8)
-	data = append(data[:len(b)], b...)
-
-	buf := bytes.NewReader(data)
-	err := binary.Read(buf, binary.BigEndian, &number)
-	if err != nil {
-		fmt.Println("BytesToNumber failed:", err)
-	}
-
-	return number
-}
-
-// Read variable int
-//
-// Read a variable length number in big endian byte order
-func ReadVarInt(buff []byte) (ret uint64) {
-	switch l := len(buff); {
-	case l > 4:
-		d := LeftPadBytes(buff, 8)
-		binary.Read(bytes.NewReader(d), binary.BigEndian, &ret)
-	case l > 2:
-		var num uint32
-		d := LeftPadBytes(buff, 4)
-		binary.Read(bytes.NewReader(d), binary.BigEndian, &num)
-		ret = uint64(num)
-	case l > 1:
-		var num uint16
-		d := LeftPadBytes(buff, 2)
-		binary.Read(bytes.NewReader(d), binary.BigEndian, &num)
-		ret = uint64(num)
-	default:
-		var num uint8
-		binary.Read(bytes.NewReader(buff), binary.BigEndian, &num)
-		ret = uint64(num)
-	}
-
-	return
-}
-
 // Copy bytes
 //
 // Returns an exact copy of the provided bytes
@@ -152,53 +88,6 @@ func Hex2BytesFixed(str string, flen int) []byte {
 	}
 }
 
-func StringToByteFunc(str string, cb func(str string) []byte) (ret []byte) {
-	if len(str) > 1 && str[0:2] == "0x" && !strings.Contains(str, "\n") {
-		ret = Hex2Bytes(str[2:])
-	} else {
-		ret = cb(str)
-	}
-
-	return
-}
-
-func FormatData(data string) []byte {
-	if len(data) == 0 {
-		return nil
-	}
-	// Simple stupid
-	d := new(big.Int)
-	if data[0:1] == "\"" && data[len(data)-1:] == "\"" {
-		return RightPadBytes([]byte(data[1:len(data)-1]), 32)
-	} else if len(data) > 1 && data[:2] == "0x" {
-		d.SetBytes(Hex2Bytes(data[2:]))
-	} else {
-		d.SetString(data, 0)
-	}
-
-	return BigToBytes(d, 256)
-}
-
-func ParseData(data ...interface{}) (ret []byte) {
-	for _, item := range data {
-		switch t := item.(type) {
-		case string:
-			var str []byte
-			if IsHex(t) {
-				str = Hex2Bytes(t[2:])
-			} else {
-				str = []byte(t)
-			}
-
-			ret = append(ret, RightPadBytes(str, 32)...)
-		case []byte:
-			ret = append(ret, LeftPadBytes(t, 32)...)
-		}
-	}
-
-	return
-}
-
 func RightPadBytes(slice []byte, l int) []byte {
 	if l < len(slice) {
 		return slice
@@ -220,47 +109,3 @@ func LeftPadBytes(slice []byte, l int) []byte {
 
 	return padded
 }
-
-func LeftPadString(str string, l int) string {
-	if l < len(str) {
-		return str
-	}
-
-	zeros := Bytes2Hex(make([]byte, (l-len(str))/2))
-
-	return zeros + str
-
-}
-
-func RightPadString(str string, l int) string {
-	if l < len(str) {
-		return str
-	}
-
-	zeros := Bytes2Hex(make([]byte, (l-len(str))/2))
-
-	return str + zeros
-
-}
-
-func ToAddress(slice []byte) (addr []byte) {
-	if len(slice) < 20 {
-		addr = LeftPadBytes(slice, 20)
-	} else if len(slice) > 20 {
-		addr = slice[len(slice)-20:]
-	} else {
-		addr = slice
-	}
-
-	addr = CopyBytes(addr)
-
-	return
-}
-
-func ByteSliceToInterface(slice [][]byte) (ret []interface{}) {
-	for _, i := range slice {
-		ret = append(ret, i)
-	}
-
-	return
-}