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