C++ FileMap::create方法代码示例

FileMap*
FileMapBuffer::createMap(const char* filename)
{
	int fd;
	size_t length;

	fd = ::open(filename, O_RDONLY | O_BINARY);
	if (fd < 0) {
		LOGW("Unable to open file '%s': %s\n", filename, strerror(errno));
		return NULL;
	}

	length = lseek(fd, 0, SEEK_END);
	lseek(fd, 0, SEEK_SET);

	FileMap* map = new FileMap();
	if (!map) {
		LOGW("Unable to create file map for '%s': %s\n", filename, strerror(errno));
		return NULL;
	}

	if (!map->create(filename, fd, 0, length, true)) {
		map->release();
		LOGW("Unable to create file map for '%s': %s\n", filename, strerror(errno));
		return NULL;
	}

	close(fd);

	return map;
}

status_t Tokenizer::open(const String8& filename, Tokenizer** outTokenizer) {
    *outTokenizer = NULL;

    int result = NO_ERROR;
    int fd = ::open(filename.string(), O_RDONLY);
    if (fd < 0) {
        result = -errno;
        ALOGE("Error opening file '%s', %s.", filename.string(), strerror(errno));
    } else {
        struct stat stat;
        if (fstat(fd, &stat)) {
            result = -errno;
            ALOGE("Error getting size of file '%s', %s.", filename.string(), strerror(errno));
        } else {
            size_t length = size_t(stat.st_size);

            FileMap* fileMap = new FileMap();
            bool ownBuffer = false;
            char* buffer;
            if (fileMap->create(NULL, fd, 0, length, true)) {
                fileMap->advise(FileMap::SEQUENTIAL);
                buffer = static_cast<char*>(fileMap->getDataPtr());
            } else {
                delete fileMap;
                fileMap = NULL;

                // Fall back to reading into a buffer since we can't mmap files in sysfs.
                // The length we obtained from stat is wrong too (it will always be 4096)
                // so we must trust that read will read the entire file.
                buffer = new char[length];
                ownBuffer = true;
                ssize_t nrd = read(fd, buffer, length);
                if (nrd < 0) {
                    result = -errno;
                    ALOGE("Error reading file '%s', %s.", filename.string(), strerror(errno));
                    delete[] buffer;
                    buffer = NULL;
                } else {
                    length = size_t(nrd);
                }
            }

            if (!result) {
                *outTokenizer = new Tokenizer(filename, fileMap, buffer, ownBuffer, length);
            }
        }
        close(fd);
    }
    return result;
}

/*
 * Create a new FileMap object that spans the data in "entry".
 */
FileMap* ZipFileRO::createEntryFileMap(ZipEntryRO entry) const
{
    const _ZipEntryRO *zipEntry = reinterpret_cast<_ZipEntryRO*>(entry);
    const ZipEntry& ze = zipEntry->entry;
    int fd = GetFileDescriptor(mHandle);
    size_t actualLen = 0;

    if (ze.method == kCompressStored) {
        actualLen = ze.uncompressed_length;
    } else {
        actualLen = ze.compressed_length;
    }

    FileMap* newMap = new FileMap();
    if (!newMap->create(mFileName, fd, ze.offset, actualLen, true)) {
        newMap->release();
        return NULL;
    }

    return newMap;
}

/*
 * Return a read-only pointer to a buffer.
 *
 * We can either read the whole thing in or map the relevant piece of
 * the source file.  Ideally a map would be established at a higher
 * level and we'd be using a different object, but we didn't, so we
 * deal with it here.
 */
const void* _FileAsset::getBuffer(bool wordAligned)
{
    /* subsequent requests just use what we did previously */
    if (mBuf != NULL)
        return mBuf;
    if (mMap != NULL) {
        if (!wordAligned) {
            return  mMap->getDataPtr();
        }
        return ensureAlignment(mMap);
    }

    assert(mFp != NULL);

    if (mLength < kReadVsMapThreshold) {
        unsigned char* buf;
        long allocLen;

        /* zero-length files are allowed; not sure about zero-len allocs */
        /* (works fine with gcc + x86linux) */
        allocLen = mLength;
        if (mLength == 0)
            allocLen = 1;

        buf = new unsigned char[allocLen];
        if (buf == NULL) {
            ALOGE("alloc of %ld bytes failed\n", (long) allocLen);
            return NULL;
        }

        ALOGV("Asset %p allocating buffer size %d (smaller than threshold)", this, (int)allocLen);
        if (mLength > 0) {
            long oldPosn = ftell(mFp);
            fseek(mFp, mStart, SEEK_SET);
            if (fread(buf, 1, mLength, mFp) != (size_t) mLength) {
                ALOGE("failed reading %ld bytes\n", (long) mLength);
                delete[] buf;
                return NULL;
            }
            fseek(mFp, oldPosn, SEEK_SET);
        }

        ALOGV(" getBuffer: loaded into buffer\n");

        mBuf = buf;
        return mBuf;
    } else {
        FileMap* map;

        map = new FileMap;
        if (!map->create(NULL, fileno(mFp), mStart, mLength, true)) {
            delete map;
            return NULL;
        }

        ALOGV(" getBuffer: mapped\n");

        mMap = map;
        if (!wordAligned) {
            return  mMap->getDataPtr();
        }
        return ensureAlignment(mMap);
    }
}