lnav/src/shlex.hh

/**
 * Copyright (c) 2015, Timothy Stack
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 * * Neither the name of Timothy Stack nor the names of its contributors
 * may be used to endorse or promote products derived from this software
 * without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ''AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * @file shlex.hh
 */

#ifndef LNAV_SHLEX_HH_H
#define LNAV_SHLEX_HH_H

#include <pwd.h>

#include <map>
#include <vector>
#include <string>

#include "pcrepp/pcrepp.hh"

enum class shlex_token_t {
    ST_ERROR,
    ST_WHITESPACE,
    ST_ESCAPE,
    ST_DOUBLE_QUOTE_START,
    ST_DOUBLE_QUOTE_END,
    ST_SINGLE_QUOTE_START,
    ST_SINGLE_QUOTE_END,
    ST_VARIABLE_REF,
    ST_QUOTED_VARIABLE_REF,
    ST_TILDE,
};

class scoped_resolver {
public:
    scoped_resolver(std::initializer_list<std::map<std::string, std::string> *> l) {
        this->sr_stack.insert(this->sr_stack.end(), l.begin(), l.end());
    };

    typedef std::map<std::string, std::string>::const_iterator const_iterator;

    const_iterator find(const std::string &str) const {
        const_iterator retval;

        for (auto scope : this->sr_stack) {
            if ((retval = scope->find(str)) != scope->end()) {
                return retval;
            }
        }

        return this->end();
    };

    const_iterator end() const {
        return this->sr_stack.back()->end();
    }

    std::vector<const std::map<std::string, std::string> *> sr_stack;
};

class shlex {
public:
    shlex(const char *str, size_t len)
            : s_str(str),
              s_len(len) {
    };

    explicit shlex(const std::string &str)
            : s_str(str.c_str()),
              s_len(str.size()) {
    };

    shlex &with_ignore_quotes(bool val) {
        this->s_ignore_quotes = val;
        return *this;
    }

    bool tokenize(pcre_context::capture_t &cap_out, shlex_token_t &token_out);

    template <typename Resolver = scoped_resolver>
    bool eval(std::string &result, const Resolver &vars) {
        result.clear();

        pcre_context::capture_t cap;
        shlex_token_t token;
        int last_index = 0;

        while (this->tokenize(cap, token)) {
            result.append(&this->s_str[last_index], cap.c_begin - last_index);
            switch (token) {
                case shlex_token_t::ST_ERROR:
                    return false;
                case shlex_token_t::ST_ESCAPE:
                    result.append(1, this->s_str[cap.c_begin + 1]);
                    break;
                case shlex_token_t::ST_WHITESPACE:
                    result.append(&this->s_str[cap.c_begin], cap.length());
                    break;
                case shlex_token_t::ST_VARIABLE_REF:
                case shlex_token_t::ST_QUOTED_VARIABLE_REF: {
                    int extra = token == shlex_token_t::ST_VARIABLE_REF ? 0 : 1;
                    std::string var_name(&this->s_str[cap.c_begin + 1 + extra], cap.length() - 1 - extra * 2);
                    std::map<std::string, std::string>::const_iterator local_var;
                    const char *var_value = getenv(var_name.c_str());

                    if ((local_var = vars.find(var_name)) != vars.end()) {
                        result.append(local_var->second);
                    }
                    else if (var_value != nullptr) {
                        result.append(var_value);
                    }
                    break;
                }
                case shlex_token_t::ST_TILDE:
                    this->resolve_home_dir(result, cap);
                    break;
                default:
                    break;
            }
            last_index = cap.c_end;
        }

        result.append(&this->s_str[last_index], this->s_len - last_index);

        return true;
    };

    template <typename Resolver>
    bool split(std::vector<std::string> &result, const Resolver &vars) {
        result.clear();

        pcre_context::capture_t cap;
        shlex_token_t token;
        int last_index = 0;
        bool start_new = true;

        while (isspace(this->s_str[this->s_index])) {
            this->s_index += 1;
        }
        while (this->tokenize(cap, token)) {
            if (start_new) {
                result.emplace_back("");
                start_new = false;
            }
            result.back().append(&this->s_str[last_index], cap.c_begin - last_index);
            switch (token) {
                case shlex_token_t::ST_ERROR:
                    return false;
                case shlex_token_t::ST_ESCAPE:
                    result.back().append(1, this->s_str[cap.c_begin + 1]);
                    break;
                case shlex_token_t::ST_WHITESPACE:
                    start_new = true;
                    break;
                case shlex_token_t::ST_VARIABLE_REF:
                case shlex_token_t::ST_QUOTED_VARIABLE_REF: {
                    int extra = token == shlex_token_t::ST_VARIABLE_REF ? 0 : 1;
                    std::string var_name(&this->s_str[cap.c_begin + 1 + extra], cap.length() - 1 - extra * 2);
                    std::map<std::string, std::string>::const_iterator local_var;
                    const char *var_value = getenv(var_name.c_str());

                    if ((local_var = vars.find(var_name)) != vars.end()) {
                        result.back().append(local_var->second);
                    }
                    else if (var_value != nullptr) {
                        result.back().append(var_value);
                    }
                    break;
                }
                case shlex_token_t::ST_TILDE:
                    this->resolve_home_dir(result.back(), cap);
                    break;
                default:
                    break;
            }
            last_index = cap.c_end;
        }

        if (last_index < this->s_len) {
            if (start_new || result.empty()) {
                result.emplace_back("");
            }
            result.back().append(&this->s_str[last_index], this->s_len - last_index);
        }

        return true;
    }

    void reset() {
        this->s_index = 0;
        this->s_state = state_t::STATE_NORMAL;
    };

    void scan_variable_ref(pcre_context::capture_t &cap_out, shlex_token_t &token_out);

    void resolve_home_dir(std::string& result, const pcre_context::capture_t cap) const {
        if (cap.length() == 1) {
            const char *home_dir = getenv("HOME");

            if (home_dir != nullptr) {
                result.append(home_dir);
            } else {
                result.append("~");
            }
        } else {
            auto username = (char *) alloca(cap.length());

            memcpy(username, &this->s_str[cap.c_begin + 1], cap.length() - 1);
            username[cap.length() - 1] = '\0';
            auto pw = getpwnam(username);
            if (pw != nullptr) {
                result.append(pw->pw_dir);
            } else {
                result.append(&this->s_str[cap.c_begin], cap.length());
            }
        }
    }

    enum class state_t {
        STATE_NORMAL,
        STATE_IN_DOUBLE_QUOTE,
        STATE_IN_SINGLE_QUOTE,
    };

    const char *s_str;
    ssize_t s_len;
    bool s_ignore_quotes{false};
    ssize_t s_index{0};
    state_t s_state{state_t::STATE_NORMAL};
};

#endif //LNAV_SHLEX_HH_H