media/mtp/MtpStringBuffer.cpp

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#define LOG_TAG "MtpStringBuffer"

#include <codecvt>
#include <locale>
#include <string>
#include <vector>

#include "MtpDataPacket.h"
#include "MtpStringBuffer.h"

namespace {

const char * utf16_cerror = "__CONVERSION_ERROR__";
const char16_t * utf8_cerror = u"__CONVERSION_ERROR__";

std::wstring_convert<std::codecvt_utf8_utf16<char16_t>,char16_t> gConvert(utf16_cerror, utf8_cerror);

static std::string utf16ToUtf8(std::u16string input_str) {
    std::string conversion = gConvert.to_bytes(input_str);

    if (conversion == utf16_cerror) {
        ALOGE("Unable to convert UTF-16 string to UTF-8");
        return "";
    } else {
        return conversion;
    }
}

static std::u16string utf8ToUtf16(std::string input_str) {
    std::u16string conversion = gConvert.from_bytes(input_str);

    if (conversion == utf8_cerror) {
        ALOGE("Unable to convert UTF-8 string to UTF-16");
        return u"";
    } else {
        return conversion;
    }
}

} // namespace

namespace android {

MtpStringBuffer::MtpStringBuffer(const char* src)
{
    set(src);
}

MtpStringBuffer::MtpStringBuffer(const uint16_t* src)
{
    set(src);
}

MtpStringBuffer::MtpStringBuffer(const MtpStringBuffer& src)
{
    mString = src.mString;
}

void MtpStringBuffer::set(const char* src) {
    mString = std::string(src);
}

void MtpStringBuffer::set(const uint16_t* src) {
    mString = utf16ToUtf8(std::u16string((const char16_t*)src));
}

bool MtpStringBuffer::readFromPacket(MtpDataPacket* packet) {
    uint8_t count;
    if (!packet->getUInt8(count))
        return false;
    if (count == 0)
        return true;

    std::vector<char16_t> buffer(count);
    for (int i = 0; i < count; i++) {
        uint16_t ch;
        if (!packet->getUInt16(ch))
            return false;
        buffer[i] = ch;
    }
    if (buffer[count-1] != '\0') {
        ALOGE("Mtp string not null terminated\n");
        return false;
    }
    mString = utf16ToUtf8(std::u16string(buffer.data()));
    return true;
}

void MtpStringBuffer::writeToPacket(MtpDataPacket* packet) const {
    std::u16string src16 = utf8ToUtf16(mString);
    int count = src16.length();

    if (count == 0) {
        packet->putUInt8(0);
        return;
    }
    packet->putUInt8(std::min(count + 1, MTP_STRING_MAX_CHARACTER_NUMBER));

    int i = 0;
    for (char16_t &c : src16) {
        if (i == MTP_STRING_MAX_CHARACTER_NUMBER - 1) {
            // Leave a slot for null termination.
            ALOGI("Mtp truncating long string\n");
            break;
        }
        packet->putUInt16(c);
        i++;
    }
    // only terminate with zero if string is not empty
    packet->putUInt16(0);
}

}  // namespace android