lnav/src/json_ptr.cc

/**
 * Copyright (c) 2014, 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 TIMOTHY STACK 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 json_ptr.cc
 */

#include "config.h"

#include "yajl/api/yajl_gen.h"

#include "json_ptr.hh"

using namespace std;

static int handle_null(void *ctx)
{
    json_ptr_walk *jpw = (json_ptr_walk *)ctx;

    jpw->jpw_values.emplace_back(jpw->current_ptr(), yajl_t_null, "null");
    jpw->inc_array_index();

    return 1;
}

static int handle_boolean(void *ctx, int boolVal)
{
    json_ptr_walk *jpw = (json_ptr_walk *)ctx;

    jpw->jpw_values.emplace_back(jpw->current_ptr(),
                                 boolVal ? yajl_t_true : yajl_t_false,
                                 boolVal ? "true" : "false");
    jpw->inc_array_index();

    return 1;
}

static int handle_number(void *ctx, const char *numberVal, size_t numberLen)
{
    json_ptr_walk *jpw = (json_ptr_walk *)ctx;

    jpw->jpw_values.emplace_back(jpw->current_ptr(),
                                 yajl_t_number,
                                 string(numberVal, numberLen));
    jpw->inc_array_index();

    return 1;
}

static void appender(void *ctx, const char *strVal, size_t strLen)
{
    string &str = *(string *)ctx;

    str.append(strVal, strLen);
}

static int handle_string(void *ctx, const unsigned char * stringVal, size_t len)
{
    json_ptr_walk *jpw = (json_ptr_walk *)ctx;
    auto_mem<yajl_gen_t> gen(yajl_gen_free);
    string str;

    gen = yajl_gen_alloc(nullptr);
    yajl_gen_config(gen.in(), yajl_gen_print_callback, appender, &str);
    yajl_gen_string(gen.in(), stringVal, len);
    jpw->jpw_values.emplace_back(jpw->current_ptr(), yajl_t_string, str);
    jpw->inc_array_index();

    return 1;
}

static int handle_start_map(void *ctx)
{
    json_ptr_walk *jpw = (json_ptr_walk *)ctx;

    jpw->jpw_keys.emplace_back("");
    jpw->jpw_array_indexes.push_back(-1);

    return 1;
}

static int handle_map_key(void *ctx, const unsigned char * key, size_t len)
{
    json_ptr_walk *jpw = (json_ptr_walk *)ctx;
    char partially_encoded_key[len + 32];
    size_t required_len;

    jpw->jpw_keys.pop_back();

    required_len = json_ptr::encode(partially_encoded_key, sizeof(partially_encoded_key),
        (const char *)key, len);
    if (required_len < sizeof(partially_encoded_key)) {
        jpw->jpw_keys.push_back(string(partially_encoded_key, required_len));
    }
    else {
        char fully_encoded_key[required_len];

        json_ptr::encode(fully_encoded_key, sizeof(fully_encoded_key),
            (const char *)key, len);
        jpw->jpw_keys.push_back(string(fully_encoded_key, required_len));
    }

    return 1;
}

static int handle_end_map(void *ctx)
{
    json_ptr_walk *jpw = (json_ptr_walk *)ctx;

    jpw->jpw_keys.pop_back();
    jpw->jpw_array_indexes.pop_back();

    jpw->inc_array_index();

    return 1;
}

static int handle_start_array(void *ctx)
{
    json_ptr_walk *jpw = (json_ptr_walk *)ctx;

    jpw->jpw_keys.emplace_back("");
    jpw->jpw_array_indexes.push_back(0);

    return 1;
}

static int handle_end_array(void *ctx)
{
    json_ptr_walk *jpw = (json_ptr_walk *)ctx;

    jpw->jpw_keys.pop_back();
    jpw->jpw_array_indexes.pop_back();
    jpw->inc_array_index();

    return 1;
}

const yajl_callbacks json_ptr_walk::callbacks = {
    handle_null,
    handle_boolean,
    NULL,
    NULL,
    handle_number,
    handle_string,
    handle_start_map,
    handle_map_key,
    handle_end_map,
    handle_start_array,
    handle_end_array
};

size_t
json_ptr::encode(char *dst, size_t dst_len, const char *src, size_t src_len)
{
    size_t retval = 0;

    if (src_len == (size_t)-1) {
        src_len = strlen(src);
    }

    for (size_t lpc = 0; lpc < src_len; lpc++) {
        switch (src[lpc]) {
            case '/':
            case '~':
            case '#':
                if (retval < dst_len) {
                    dst[retval] = '~';
                    retval += 1;
                    if (src[lpc] == '~') {
                        dst[retval] = '0';
                    }
                    else if (src[lpc] == '#') {
                        dst[retval] = '2';
                    }
                    else {
                        dst[retval] = '1';
                    }
                }
                else {
                    retval += 1;
                }
                break;
            default:
                if (retval < dst_len) {
                    dst[retval] = src[lpc];
                }
                break;
        }
        retval += 1;
    }

    return retval;
}

size_t json_ptr::decode(char *dst, const char *src, ssize_t src_len)
{
    size_t retval = 0;

    if (src_len == -1) {
        src_len = strlen(src);
    }

    for (int lpc = 0; lpc < src_len; lpc++) {
        switch (src[lpc]) {
            case '~':
                if ((lpc + 1) < src_len) {
                    switch (src[lpc + 1]) {
                        case '0':
                            dst[retval++] = '~';
                            lpc += 1;
                            break;
                        case '1':
                            dst[retval++] = '/';
                            lpc += 1;
                            break;
                        case '2':
                            dst[retval++] = '#';
                            lpc += 1;
                            break;
                        default:
                            break;
                    }
                }
                break;
            default:
                dst[retval++] = src[lpc];
                break;
        }
    }

    dst[retval] = '\0';

    return retval;
}

bool json_ptr::expect_map(int32_t &depth, int32_t &index)
{
    bool retval;

    if (this->jp_state == MS_DONE) {
        retval = true;
    }
    else if (depth != this->jp_depth) {
        retval = true;
    }
    else if (this->reached_end()) {
        retval = true;
    }
    else if (this->jp_state == MS_VALUE &&
             (this->jp_array_index == -1 ||
                 ((index - 1) == this->jp_array_index))) {
        if (this->jp_pos[0] == '/') {
            this->jp_pos += 1;
            this->jp_depth += 1;
            this->jp_state = MS_VALUE;
            this->jp_array_index = -1;
            index = -1;
        }
        retval = true;
    }
    else {
        retval = true;
    }
    depth += 1;

    return retval;
}

bool json_ptr::at_key(int32_t depth, const char *component, ssize_t len)
{
    const char *component_end;
    int lpc;

    if (this->jp_state == MS_DONE || depth != this->jp_depth) {
        return true;
    }

    if (len == -1) {
        len = strlen(component);
    }
    component_end = component + len;

    for (lpc = 0; component < component_end; lpc++, component++) {
        char ch = this->jp_pos[lpc];

        if (this->jp_pos[lpc] == '~') {
            switch (this->jp_pos[lpc + 1]) {
                case '0':
                    ch = '~';
                    break;
                case '1':
                    ch = '/';
                    break;
                default:
                    this->jp_state = MS_ERR_INVALID_ESCAPE;
                    return false;
            }
            lpc += 1;
        }
        else if (this->jp_pos[lpc] == '/') {
            ch = '\0';
        }

        if (ch != *component) {
            return true;
        }
    }

    this->jp_pos += lpc;
    this->jp_state = MS_VALUE;

    return true;
}

void json_ptr::exit_container(int32_t &depth, int32_t &index)
{
    depth -= 1;
    if (this->jp_state == MS_VALUE &&
        depth == this->jp_depth &&
        (index == -1 || (index - 1 == this->jp_array_index)) &&
        this->reached_end()) {
        this->jp_state = MS_DONE;
        index = -1;
    }
}

bool json_ptr::expect_array(int32_t &depth, int32_t &index)
{
    bool retval;

    if (this->jp_state == MS_DONE) {
        retval = true;
    }
    else if (depth != this->jp_depth) {
        retval = true;
    }
    else if (this->reached_end()) {
        retval = true;
    }
    else if (this->jp_pos[0] == '/') {
        int offset;

        this->jp_depth += 1;

        if (sscanf(this->jp_pos, "/%d%n", &this->jp_array_index, &offset) != 1) {
            this->jp_state = MS_ERR_INVALID_INDEX;
            retval = true;
        }
        else if (this->jp_pos[offset] != '\0' && this->jp_pos[offset] != '/') {
            this->jp_state = MS_ERR_INVALID_INDEX;
            retval = true;
        }
        else {
            index = 0;
            this->jp_pos += offset;
            this->jp_state = MS_VALUE;
            retval = true;
        }
    }
    else {
        this->jp_state = MS_ERR_NO_SLASH;
        retval = true;
    }

    depth += 1;

    return retval;
}

bool json_ptr::at_index(int32_t &depth, int32_t &index, bool primitive)
{
    bool retval;

    if (this->jp_state == MS_DONE) {
        retval = false;
    }
    else if (depth < this->jp_depth) {
        retval = false;
    }
    else if (depth == this->jp_depth) {
        if (index == -1) {
            if (this->jp_array_index == -1) {
                retval = this->reached_end();
                if (primitive && retval) {
                    this->jp_state = MS_DONE;
                }
            }
            else {
                retval = false;
            }
        }
        else if (index == this->jp_array_index) {
            retval = this->reached_end();
            this->jp_array_index = -1;
            index = -1;
            if (primitive && retval) {
                this->jp_state = MS_DONE;
            }
        }
        else {
            index += 1;
            retval = false;
        }
    }
    else if (index == -1) {
        retval = this->reached_end();
    }
    else {
        retval = false;
    }

    return retval;
}