retrace/json.cpp

/**************************************************************************
 *
 * Copyright 2011 Jose Fonseca
 * All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 **************************************************************************/

/*
 * JSON writing functions.
 */


#include <assert.h>
#include <string.h>

#include <sstream>

#include "json.hpp"


void
JSONWriter::newline(void) {
    os << "\n";
    for (int i = 0; i < level; ++i)
        os << "  ";
}

void
JSONWriter::separator(void) {
    if (value) {
        os << ",";
        switch (space) {
        case '\0':
            break;
        case '\n':
            newline();
            break;
        default:
            os << space;
            break;
        }
    } else {
        if (space == '\n') {
            newline();
        }
    }
}

static void
escapeAsciiString(std::ostream &os, const char *str) {
    os << "\"";

    const unsigned char *src = (const unsigned char *)str;
    unsigned char c;
    while ((c = *src++)) {
        if ((c == '\"') ||
            (c == '\\')) {
            // escape character
            os << '\\' << (unsigned char)c;
        } else if ((c >= 0x20 && c <= 0x7e) ||
                    c == '\t' ||
                    c == '\r' ||
                    c == '\n') {
            // pass-through character
            os << (unsigned char)c;
        } else {
            assert(0);
            os << "?";
        }
    }

    os << "\"";
}

static void
escapeUnicodeString(std::ostream &os, const char *str) {
    os << "\"";

    const char *locale = setlocale(LC_CTYPE, "");
    const char *src = str;
    mbstate_t state;

    memset(&state, 0, sizeof state);

    do {
        // Convert characters one at a time in order to recover from
        // conversion errors
        wchar_t c;
        size_t written = mbsrtowcs(&c, &src, 1, &state);
        if (written == 0) {
            // completed
            break;
        } if (written == (size_t)-1) {
            // conversion error -- skip
            os << "?";
            do {
                ++src;
            } while (*src & 0x80);
        } else if ((c == '\"') ||
                   (c == '\\')) {
            // escape character
            os << '\\' << (unsigned char)c;
        } else if ((c >= 0x20 && c <= 0x7e) ||
                    c == '\t' ||
                    c == '\r' ||
                    c == '\n') {
            // pass-through character
            os << (unsigned char)c;
        } else {
            // unicode
            os << "\\u" << std::hex << std::setfill('0') << std::setw(4) << (unsigned)c << std::setfill(' ') << std::dec;
        }
    } while (src);

    setlocale(LC_CTYPE, locale);

    os << "\"";
}

static void
encodeBase64String(std::ostream &os, const unsigned char *bytes, size_t size) {
    const char *table64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
    unsigned char c0, c1, c2, c3;
    char buf[4];
    unsigned written;

    os << "\"";

    written = 0;
    while (size >= 3) {
        c0 = bytes[0] >> 2;
        c1 = ((bytes[0] & 0x03) << 4) | ((bytes[1] & 0xf0) >> 4);
        c2 = ((bytes[1] & 0x0f) << 2) | ((bytes[2] & 0xc0) >> 6);
        c3 = bytes[2] & 0x3f;

        buf[0] = table64[c0];
        buf[1] = table64[c1];
        buf[2] = table64[c2];
        buf[3] = table64[c3];

        os.write(buf, 4);

        bytes += 3;
        size -= 3;
        ++written;

        if (written >= 76/4 && size) {
            os << "\n";
            written = 0;
        }
    }

    if (size > 0) {
        c0 = bytes[0] >> 2;
        c1 = ((bytes[0] & 0x03) << 4);
        buf[2] = '=';
        buf[3] = '=';

        if (size > 1) {
            c1 |= ((bytes[1] & 0xf0) >> 4);
            c2 = ((bytes[1] & 0x0f) << 2);
            if (size > 2) {
                c2 |= ((bytes[2] & 0xc0) >> 6);
                c3 = bytes[2] & 0x3f;
                buf[3] = table64[c3];
            }
            buf[2] = table64[c2];
        }
        buf[1] = table64[c1];
        buf[0] = table64[c0];

        os.write(buf, 4);
    }

    os << "\"";
}

JSONWriter::JSONWriter(std::ostream &_os) :
    os(_os),
    level(0),
    value(false),
    space(0)
{
    beginObject();
}

JSONWriter::~JSONWriter() {
    endObject();
    newline();
}

void
JSONWriter::beginObject() {
    separator();
    os << "{";
    ++level;
    value = false;
}

void
JSONWriter::endObject() {
    --level;
    if (value)
        newline();
    os << "}";
    value = true;
    space = '\n';
}

void
JSONWriter::beginMember(const char * name) {
    space = 0;
    separator();
    newline();
    escapeAsciiString(os, name);
    os << ": ";
    value = false;
}

void
JSONWriter::endMember(void) {
    assert(value);
    value = true;
    space = 0;
}

void
JSONWriter::beginArray() {
    separator();
    os << "[";
    ++level;
    value = false;
    space = 0;
}

void
JSONWriter::endArray(void) {
    --level;
    if (space == '\n') {
        newline();
    }
    os << "]";
    value = true;
    space = '\n';
}

void
JSONWriter::writeString(const char *s) {
    if (!s) {
        writeNull();
        return;
    }

    separator();
    escapeUnicodeString(os, s);
    value = true;
    space = ' ';
}

void
JSONWriter::writeBase64(const void *bytes, size_t size) {
    separator();
    encodeBase64String(os, (const unsigned char *)bytes, size);
    value = true;
    space = ' ';
}

void
JSONWriter::writeNull(void) {
    separator();
    os << "null";
    value = true;
    space = ' ';
}

void
JSONWriter::writeBool(bool b) {
    separator();
    os << (b ? "true" : "false");
    value = true;
    space = ' ';
}