protected void doCheckFileHash()

in sshd-sftp/src/main/java/org/apache/sshd/sftp/server/AbstractSftpSubsystemHelper.java [930:1023]
83 lines of code
14 McCabe index (conditional complexity)

    protected void doCheckFileHash(
            int id, Path file, NamedFactory<? extends Digest> factory,
            long startOffset, long length, int blockSize, Buffer buffer)
            throws Exception {
        ValidateUtils.checkTrue(startOffset >= 0L, "Invalid start offset: %d", startOffset);
        ValidateUtils.checkTrue(length >= 0L, "Invalid length: %d", length);
        ValidateUtils.checkTrue(
                (blockSize == 0) || (blockSize >= SftpConstants.MIN_CHKFILE_BLOCKSIZE),
                "Invalid block size: %d", blockSize);
        Objects.requireNonNull(factory, "No digest factory provided");
        buffer.putString(factory.getName());

        long effectiveLength = length;
        long totalLength = Files.size(file);
        if (effectiveLength == 0L) {
            effectiveLength = totalLength - startOffset;
        } else {
            long maxRead = startOffset + length;
            if (maxRead > totalLength) {
                effectiveLength = totalLength - startOffset;
            }
        }
        ValidateUtils.checkTrue(effectiveLength > 0L,
                "Non-positive effective hash data length: %d", effectiveLength);

        byte[] digestBuf = (blockSize == 0)
                ? new byte[Math.min((int) effectiveLength, IoUtils.DEFAULT_COPY_SIZE)]
                : new byte[Math.min((int) effectiveLength, blockSize)];
        ByteBuffer wb = ByteBuffer.wrap(digestBuf);
        SftpFileSystemAccessor accessor = getFileSystemAccessor();
        ServerSession session = getServerSession();
        try (SeekableByteChannel channel = accessor.openFile(
                this, null, file, null, Collections.emptySet())) {
            channel.position(startOffset);

            Digest digest = factory.create();
            digest.init();

            boolean traceEnabled = log.isTraceEnabled();
            if (blockSize == 0) {
                while (effectiveLength > 0L) {
                    int remainLen = Math.min(digestBuf.length, (int) effectiveLength);
                    ByteBuffer bb = wb;
                    if (remainLen < digestBuf.length) {
                        bb = ByteBuffer.wrap(digestBuf, 0, remainLen);
                    }
                    bb.clear(); // prepare for next read

                    int readLen = channel.read(bb);
                    if (readLen < 0) {
                        break;
                    }

                    effectiveLength -= readLen;
                    digest.update(digestBuf, 0, readLen);
                }

                byte[] hashValue = digest.digest();
                if (traceEnabled) {
                    log.trace("doCheckFileHash({})[{}] offset={}, length={} - algo={}, hash={}",
                            session, file, startOffset, length,
                            digest.getAlgorithm(), BufferUtils.toHex(':', hashValue));
                }
                buffer.putBytes(hashValue);
            } else {
                for (int count = 0; effectiveLength > 0L; count++) {
                    int remainLen = Math.min(digestBuf.length, (int) effectiveLength);
                    ByteBuffer bb = wb;
                    if (remainLen < digestBuf.length) {
                        bb = ByteBuffer.wrap(digestBuf, 0, remainLen);
                    }
                    bb.clear(); // prepare for next read

                    int readLen = channel.read(bb);
                    if (readLen < 0) {
                        break;
                    }

                    effectiveLength -= readLen;
                    digest.update(digestBuf, 0, readLen);

                    byte[] hashValue = digest.digest(); // NOTE: this also resets the hash for the next read
                    if (traceEnabled) {
                        log.trace("doCheckFileHash({})({})[{}] offset={}, length={} - algo={}, hash={}",
                                session, file, count, startOffset, length,
                                digest.getAlgorithm(), BufferUtils.toHex(':', hashValue));
                    }
                    buffer.putBytes(hashValue);
                }
            }

            accessor.closeFile(this, null, file, null, channel, Collections.emptySet());
        }
    }