Example usage for android.os ParcelFileDescriptor checkError

Introduction

In this page you can find the example usage for android.os ParcelFileDescriptor checkError.

Prototype

public void checkError() throws IOException 

Source Link

Document

Detect and throw if the other end of a pipe or socket pair encountered an error or crashed.

Usage

From source file:com.example.android.vault.EncryptedDocument.java

/**
 * Encrypt and write both the metadata and content sections of this
 * document, reading the content from the given pipe. Internally uses
 * {@link ParcelFileDescriptor#checkError()} to verify that content arrives
 * without errors. Writes to temporary file to keep atomic view of contents,
 * swapping into place only when write is successful.
 * <p/>/* w w  w . j a  v  a2  s  .c o m*/
 * Pipe is left open, so caller is responsible for calling
 * {@link ParcelFileDescriptor#close()} or
 * {@link ParcelFileDescriptor#closeWithError(String)}.
 *
 * @param contentIn read end of a pipe.
 */
public void writeMetadataAndContent(JSONObject meta, ParcelFileDescriptor contentIn)
        throws IOException, GeneralSecurityException {
    // Write into temporary file to provide an atomic view of existing
    // contents during write, and also to recover from failed writes.
    final String tempName = mFile.getName() + ".tmp_" + Thread.currentThread().getId();
    final File tempFile = new File(mFile.getParentFile(), tempName);

    RandomAccessFile f = new RandomAccessFile(tempFile, "rw");
    try {
        // Truncate any existing data
        f.setLength(0);

        // Write content first to detect size
        if (contentIn != null) {
            f.seek(CONTENT_OFFSET);
            final int plainLength = writeSection(f, new FileInputStream(contentIn.getFileDescriptor()));
            meta.put(Document.COLUMN_SIZE, plainLength);

            // Verify that remote side of pipe finished okay; if they
            // crashed or indicated an error then this throws and we
            // leave the original file intact and clean up temp below.
            contentIn.checkError();
        }

        meta.put(Document.COLUMN_DOCUMENT_ID, mDocId);
        meta.put(Document.COLUMN_LAST_MODIFIED, System.currentTimeMillis());

        // Rewind and write metadata section
        f.seek(0);
        f.writeInt(MAGIC_NUMBER);

        final ByteArrayInputStream metaIn = new ByteArrayInputStream(
                meta.toString().getBytes(StandardCharsets.UTF_8));
        writeSection(f, metaIn);

        if (f.getFilePointer() > CONTENT_OFFSET) {
            throw new IOException("Metadata section was too large");
        }

        // Everything written fine, atomically swap new data into place.
        // fsync() before close would be overkill, since rename() is an
        // atomic barrier.
        f.close();
        tempFile.renameTo(mFile);

    } catch (JSONException e) {
        throw new IOException(e);
    } finally {
        // Regardless of what happens, always try cleaning up.
        f.close();
        tempFile.delete();
    }
}

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