schnutibox/vendor/github.com/Nvveen/Gotty/parser.go

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// Copyright 2012 Neal van Veen. All rights reserved.
// Usage of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
package gotty
import (
"bytes"
"errors"
"fmt"
"regexp"
"strconv"
"strings"
)
var exp = [...]string{
"%%",
"%c",
"%s",
"%p(\\d)",
"%P([A-z])",
"%g([A-z])",
"%'(.)'",
"%{([0-9]+)}",
"%l",
"%\\+|%-|%\\*|%/|%m",
"%&|%\\||%\\^",
"%=|%>|%<",
"%A|%O",
"%!|%~",
"%i",
"%(:[\\ #\\-\\+]{0,4})?(\\d+\\.\\d+|\\d+)?[doxXs]",
"%\\?(.*?);",
}
var regex *regexp.Regexp
var staticVar map[byte]stacker
// Parses the attribute that is received with name attr and parameters params.
func (term *TermInfo) Parse(attr string, params ...interface{}) (string, error) {
// Get the attribute name first.
iface, err := term.GetAttribute(attr)
str, ok := iface.(string)
if err != nil {
return "", err
}
if !ok {
return str, errors.New("Only string capabilities can be parsed.")
}
// Construct the hidden parser struct so we can use a recursive stack based
// parser.
ps := &parser{}
// Dynamic variables only exist in this context.
ps.dynamicVar = make(map[byte]stacker, 26)
ps.parameters = make([]stacker, len(params))
// Convert the parameters to insert them into the parser struct.
for i, x := range params {
ps.parameters[i] = x
}
// Recursively walk and return.
result, err := ps.walk(str)
return result, err
}
// Parses the attribute that is received with name attr and parameters params.
// Only works on full name of a capability that is given, which it uses to
// search for the termcap name.
func (term *TermInfo) ParseName(attr string, params ...interface{}) (string, error) {
tc := GetTermcapName(attr)
return term.Parse(tc, params)
}
// Identify each token in a stack based manner and do the actual parsing.
func (ps *parser) walk(attr string) (string, error) {
// We use a buffer to get the modified string.
var buf bytes.Buffer
// Next, find and identify all tokens by their indices and strings.
tokens := regex.FindAllStringSubmatch(attr, -1)
if len(tokens) == 0 {
return attr, nil
}
indices := regex.FindAllStringIndex(attr, -1)
q := 0 // q counts the matches of one token
// Iterate through the string per character.
for i := 0; i < len(attr); i++ {
// If the current position is an identified token, execute the following
// steps.
if q < len(indices) && i >= indices[q][0] && i < indices[q][1] {
// Switch on token.
switch {
case tokens[q][0][:2] == "%%":
// Literal percentage character.
buf.WriteByte('%')
case tokens[q][0][:2] == "%c":
// Pop a character.
c, err := ps.st.pop()
if err != nil {
return buf.String(), err
}
buf.WriteByte(c.(byte))
case tokens[q][0][:2] == "%s":
// Pop a string.
str, err := ps.st.pop()
if err != nil {
return buf.String(), err
}
if _, ok := str.(string); !ok {
return buf.String(), errors.New("Stack head is not a string")
}
buf.WriteString(str.(string))
case tokens[q][0][:2] == "%p":
// Push a parameter on the stack.
index, err := strconv.ParseInt(tokens[q][1], 10, 8)
index--
if err != nil {
return buf.String(), err
}
if int(index) >= len(ps.parameters) {
return buf.String(), errors.New("Parameters index out of bound")
}
ps.st.push(ps.parameters[index])
case tokens[q][0][:2] == "%P":
// Pop a variable from the stack as a dynamic or static variable.
val, err := ps.st.pop()
if err != nil {
return buf.String(), err
}
index := tokens[q][2]
if len(index) > 1 {
errorStr := fmt.Sprintf("%s is not a valid dynamic variables index",
index)
return buf.String(), errors.New(errorStr)
}
// Specify either dynamic or static.
if index[0] >= 'a' && index[0] <= 'z' {
ps.dynamicVar[index[0]] = val
} else if index[0] >= 'A' && index[0] <= 'Z' {
staticVar[index[0]] = val
}
case tokens[q][0][:2] == "%g":
// Push a variable from the stack as a dynamic or static variable.
index := tokens[q][3]
if len(index) > 1 {
errorStr := fmt.Sprintf("%s is not a valid static variables index",
index)
return buf.String(), errors.New(errorStr)
}
var val stacker
if index[0] >= 'a' && index[0] <= 'z' {
val = ps.dynamicVar[index[0]]
} else if index[0] >= 'A' && index[0] <= 'Z' {
val = staticVar[index[0]]
}
ps.st.push(val)
case tokens[q][0][:2] == "%'":
// Push a character constant.
con := tokens[q][4]
if len(con) > 1 {
errorStr := fmt.Sprintf("%s is not a valid character constant", con)
return buf.String(), errors.New(errorStr)
}
ps.st.push(con[0])
case tokens[q][0][:2] == "%{":
// Push an integer constant.
con, err := strconv.ParseInt(tokens[q][5], 10, 32)
if err != nil {
return buf.String(), err
}
ps.st.push(con)
case tokens[q][0][:2] == "%l":
// Push the length of the string that is popped from the stack.
popStr, err := ps.st.pop()
if err != nil {
return buf.String(), err
}
if _, ok := popStr.(string); !ok {
errStr := fmt.Sprintf("Stack head is not a string")
return buf.String(), errors.New(errStr)
}
ps.st.push(len(popStr.(string)))
case tokens[q][0][:2] == "%?":
// If-then-else construct. First, the whole string is identified and
// then inside this substring, we can specify which parts to switch on.
ifReg, _ := regexp.Compile("%\\?(.*)%t(.*)%e(.*);|%\\?(.*)%t(.*);")
ifTokens := ifReg.FindStringSubmatch(tokens[q][0])
var (
ifStr string
err error
)
// Parse the if-part to determine if-else.
if len(ifTokens[1]) > 0 {
ifStr, err = ps.walk(ifTokens[1])
} else { // else
ifStr, err = ps.walk(ifTokens[4])
}
// Return any errors
if err != nil {
return buf.String(), err
} else if len(ifStr) > 0 {
// Self-defined limitation, not sure if this is correct, but didn't
// seem like it.
return buf.String(), errors.New("If-clause cannot print statements")
}
var thenStr string
// Pop the first value that is set by parsing the if-clause.
choose, err := ps.st.pop()
if err != nil {
return buf.String(), err
}
// Switch to if or else.
if choose.(int) == 0 && len(ifTokens[1]) > 0 {
thenStr, err = ps.walk(ifTokens[3])
} else if choose.(int) != 0 {
if len(ifTokens[1]) > 0 {
thenStr, err = ps.walk(ifTokens[2])
} else {
thenStr, err = ps.walk(ifTokens[5])
}
}
if err != nil {
return buf.String(), err
}
buf.WriteString(thenStr)
case tokens[q][0][len(tokens[q][0])-1] == 'd': // Fallthrough for printing
fallthrough
case tokens[q][0][len(tokens[q][0])-1] == 'o': // digits.
fallthrough
case tokens[q][0][len(tokens[q][0])-1] == 'x':
fallthrough
case tokens[q][0][len(tokens[q][0])-1] == 'X':
fallthrough
case tokens[q][0][len(tokens[q][0])-1] == 's':
token := tokens[q][0]
// Remove the : that comes before a flag.
if token[1] == ':' {
token = token[:1] + token[2:]
}
digit, err := ps.st.pop()
if err != nil {
return buf.String(), err
}
// The rest is determined like the normal formatted prints.
digitStr := fmt.Sprintf(token, digit.(int))
buf.WriteString(digitStr)
case tokens[q][0][:2] == "%i":
// Increment the parameters by one.
if len(ps.parameters) < 2 {
return buf.String(), errors.New("Not enough parameters to increment.")
}
val1, val2 := ps.parameters[0].(int), ps.parameters[1].(int)
val1++
val2++
ps.parameters[0], ps.parameters[1] = val1, val2
default:
// The rest of the tokens is a special case, where two values are
// popped and then operated on by the token that comes after them.
op1, err := ps.st.pop()
if err != nil {
return buf.String(), err
}
op2, err := ps.st.pop()
if err != nil {
return buf.String(), err
}
var result stacker
switch tokens[q][0][:2] {
case "%+":
// Addition
result = op2.(int) + op1.(int)
case "%-":
// Subtraction
result = op2.(int) - op1.(int)
case "%*":
// Multiplication
result = op2.(int) * op1.(int)
case "%/":
// Division
result = op2.(int) / op1.(int)
case "%m":
// Modulo
result = op2.(int) % op1.(int)
case "%&":
// Bitwise AND
result = op2.(int) & op1.(int)
case "%|":
// Bitwise OR
result = op2.(int) | op1.(int)
case "%^":
// Bitwise XOR
result = op2.(int) ^ op1.(int)
case "%=":
// Equals
result = op2 == op1
case "%>":
// Greater-than
result = op2.(int) > op1.(int)
case "%<":
// Lesser-than
result = op2.(int) < op1.(int)
case "%A":
// Logical AND
result = op2.(bool) && op1.(bool)
case "%O":
// Logical OR
result = op2.(bool) || op1.(bool)
case "%!":
// Logical complement
result = !op1.(bool)
case "%~":
// Bitwise complement
result = ^(op1.(int))
}
ps.st.push(result)
}
i = indices[q][1] - 1
q++
} else {
// We are not "inside" a token, so just skip until the end or the next
// token, and add all characters to the buffer.
j := i
if q != len(indices) {
for !(j >= indices[q][0] && j < indices[q][1]) {
j++
}
} else {
j = len(attr)
}
buf.WriteString(string(attr[i:j]))
i = j
}
}
// Return the buffer as a string.
return buf.String(), nil
}
// Push a stacker-value onto the stack.
func (st *stack) push(s stacker) {
*st = append(*st, s)
}
// Pop a stacker-value from the stack.
func (st *stack) pop() (stacker, error) {
if len(*st) == 0 {
return nil, errors.New("Stack is empty.")
}
newStack := make(stack, len(*st)-1)
val := (*st)[len(*st)-1]
copy(newStack, (*st)[:len(*st)-1])
*st = newStack
return val, nil
}
// Initialize regexes and the static vars (that don't get changed between
// calls.
func init() {
// Initialize the main regex.
expStr := strings.Join(exp[:], "|")
regex, _ = regexp.Compile(expStr)
// Initialize the static variables.
staticVar = make(map[byte]stacker, 26)
}