func (l *Lexer) VariableSimple() {
// When we enter this state we know we have at least one readable
// char for the varname. That means that any character not valid
// just terminates the parsing and we dont have to
// worry about the case of an empty varname
l.buffer.WriteRune(SentinalSubstitution)
sv := SubVariable{SubType: VarSubNormal}
varbuf := bytes.Buffer{}
c := l.nextChar()
switch {
case char.IsSpecial(c):
varbuf.WriteRune(c)
case char.IsDigit(c):
// Positional argv
for {
varbuf.WriteRune(c)
c = l.nextChar()
if !char.IsDigit(c) {
l.backup()
break
}
}
case char.IsFirstInVarName(c):
for {
varbuf.WriteRune(c)
c = l.nextChar()
if !char.IsInVarName(c) {
l.backup()
break
}
}
default:
l.backup()
}
sv.VarName = varbuf.String()
l.subs = append(l.subs, sv)
return
}
func (l *Lexer) Substitution() {
// Upon entering we have only read the '$'
// Perform the lex of a single complete substitution before returning
// control to the calling location
c := l.nextChar()
switch {
default:
l.buffer.WriteRune('$')
l.backup()
case c == '(':
if l.hasNext('(') {
l.Arith()
} else {
l.Subshell()
}
case char.IsFirstInVarName(c), char.IsDigit(c), char.IsSpecial(c):
l.backup()
l.VariableSimple()
case c == '{':
l.VariableComplex()
}
}
func (l *Lexer) VariableComplex() {
// Upon entering we have read the opening '{'
l.buffer.WriteRune(SentinalSubstitution)
sv := SubVariable{}
varbuf := bytes.Buffer{}
defer func() {
// We defer this as there are multiple return points
sv.VarName = varbuf.String()
l.subs = append(l.subs, sv)
}()
if l.hasNext('#') {
// The NParam Special Var
if l.hasNext('}') {
varbuf.WriteRune('#')
return
}
// Length variable operator
sv.SubType = VarSubLength
}
c := l.nextChar()
switch {
case char.IsSpecial(c):
varbuf.WriteRune(c)
case char.IsDigit(c):
for {
varbuf.WriteRune(c)
c = l.nextChar()
if !char.IsDigit(c) {
l.backup()
break
}
}
case char.IsFirstInVarName(c):
for {
varbuf.WriteRune(c)
c = l.nextChar()
if !char.IsInVarName(c) {
l.backup()
break
}
}
case c == EOFRune:
l.backup()
return
}
// Either a Enclosed variable '${foo}' or a length operation '${#foo}'
if l.hasNext('}') {
return
}
// Length operator should have returned since only ${#varname} is valid
if sv.SubType == VarSubLength {
l.log.Error("Line %d: Bad substitution (%s)", l.lineNo, l.input[l.lastPosition:l.position])
os.Exit(1)
}
if l.hasNext(':') {
sv.CheckNull = true
}
switch l.nextChar() {
case '-':
sv.SubType = VarSubMinus
case '+':
sv.SubType = VarSubPlus
case '?':
sv.SubType = VarSubQuestion
case '=':
sv.SubType = VarSubAssign
case '#':
if l.hasNext('#') {
sv.SubType = VarSubTrimLeftMax
} else {
sv.SubType = VarSubTrimLeft
}
case '%':
if l.hasNext('%') {
sv.SubType = VarSubTrimRightMax
} else {
sv.SubType = VarSubTrimRight
}
default:
l.log.Error("Line %d: Bad substitution (%s)", l.lineNo, l.input[l.lastPosition:l.position])
os.Exit(1)
}
// Read until '}'
// In the future to support Nested vars etc create new sublexer from
// l.input[l.pos:] and take the first lexitem as the sub val then adjust
// this lexer's position and trash sublexer
c = l.nextChar()
subValBuf := bytes.Buffer{}
for {
if c == '}' {
break
}
subValBuf.WriteRune(c)
c = l.nextChar()
}
sv.SubVal = subValBuf.String()
}
// Lex returns the next Token in the input string and an interface value.
// The interface will also contain a value dependant on the Token
// If Token == ArithNumber then interface will be an int64
// If Token == ArithVariable then interface will be a string
// If Token == ArithError then interface will be an error
func (l *Lexer) Lex() (Token, interface{}) {
var t Token
var checkAssignmentOp bool
var startPos, endPos int
c := l.next()
// Ignore whitespace
for {
if c == ' ' || c == '\n' || c == '\t' {
c = l.next()
} else {
break
}
}
if c == EOFRune {
return ArithEOF, nil
}
if char.IsDigit(c) {
return lexDigit(l, c)
}
// Finds variable names.
if char.IsFirstInVarName(c) {
startPos = l.pos - l.lastRuneWidth
endPos = l.pos
for {
if l.hasNextFunc(char.IsInVarName) {
endPos++
} else {
break
}
}
return ArithVariable, l.input[startPos:endPos]
}
switch c {
case '>':
switch l.next() {
case '>':
t = ArithRightShift
checkAssignmentOp = true
case '=':
t = ArithGreaterEqual
default:
t = ArithGreaterThan
l.backup()
}
case '<':
switch l.next() {
case '<':
t = ArithLeftShift
checkAssignmentOp = true
case '=':
t = ArithLessEqual
default:
t = ArithLessThan
l.backup()
}
case '|':
if l.hasNext('|') {
t = ArithOr
} else {
t = ArithBinaryOr
checkAssignmentOp = true
}
case '&':
if l.hasNext('&') {
t = ArithAnd
} else {
t = ArithBinaryAnd
checkAssignmentOp = true
}
case '*':
t = ArithMultiply
checkAssignmentOp = true
case '/':
t = ArithDivide
checkAssignmentOp = true
case '%':
t = ArithRemainder
checkAssignmentOp = true
case '+':
t = ArithAdd
checkAssignmentOp = true
case '-':
t = ArithSubtract
checkAssignmentOp = true
case '^':
t = ArithBinaryXor
checkAssignmentOp = true
case '!':
if l.hasNext('=') {
t = ArithNotEqual
} else {
t = ArithNot
}
case '=':
if l.hasNext('=') {
t = ArithEqual
} else {
t = ArithAssignment
}
case '(':
t = ArithLeftParen
case ')':
t = ArithRightParen
case '~':
t = ArithBinaryNot
case '?':
t = ArithQuestionMark
case ':':
t = ArithColon
default:
t = ArithError
}
if checkAssignmentOp {
if l.hasNext('=') {
t += ArithAssignDiff
}
}
return t, nil
}