ehrmann / vcdiff-java / 26

package com.davidehrmann.vcdiff.engine;

import java.util.Objects;

import com.davidehrmann.vcdiff.util.VarInt;

import com.davidehrmann.vcdiff.util.ZeroInitializedAdler32;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import java.io.IOException;

import java.nio.ByteBuffer;

import java.util.concurrent.atomic.AtomicInteger;

import java.util.zip.Adler32;

import static com.davidehrmann.vcdiff.engine.VCDiffCodeTableData.VCD_ADD;

import static com.davidehrmann.vcdiff.engine.VCDiffCodeTableData.VCD_COPY;

import static com.davidehrmann.vcdiff.engine.VCDiffCodeTableData.VCD_INSTRUCTION_END_OF_DATA;

import static com.davidehrmann.vcdiff.engine.VCDiffCodeTableData.VCD_RUN;

import static com.davidehrmann.vcdiff.engine.VCDiffCodeTableWriterImpl.VCD_CHECKSUM;

import static com.davidehrmann.vcdiff.engine.VCDiffCodeTableWriterImpl.VCD_SOURCE;

import static com.davidehrmann.vcdiff.engine.VCDiffCodeTableWriterImpl.VCD_TARGET;

@SuppressWarnings("UnnecessaryInitCause")

class VCDiffDeltaFileWindow {

    // Resets the pointers to the data sections in the current window.

    public void Reset() {

        // Mark the start of the current target window.

    public void useCodeTable(VCDiffCodeTableData code_table_data, short max_mode) {

    // Decodes a single delta window using the input data from *parseable_chunk.

    // Appends the decoded target window to parent->decodedTarget().  Returns

    // RESULT_SUCCESS if an entire window was decoded, or RESULT_END_OF_DATA if

    // the end of input was reached before the entire window could be decoded and

    // more input is expected (only possible if isInterleaved() is true), or

    // RESULT_ERROR if an error occurred during decoding.  In the RESULT_ERROR

    // case, the value of parseable_chunk->pointer_ is undefined; otherwise,

    // parseable_chunk->Advance() is called to point to the input data position

    // just after the data that has been decoded.

    //

    public int DecodeWindow(ByteBuffer parseable_chunk) throws IOException {

            }

            // reset address cache between windows (RFC section 5.1)

        } else {

            // We are resuming a window that was partially decoded before a

            // RESULT_END_OF_DATA was returned.  This can only happen on the first

            // loop iteration, and only if the interleaved format is enabled and used.

            }

            // FIXME: ?

        }

            case VCDiffHeaderParser.RESULT_END_OF_DATA:

                } else {

                }

            default:

                break;  // decodeBody succeeded

        }

        // Get ready to read a new delta window

    }

    public boolean FoundWindowHeader() {

    }

    public boolean moreDataExpected() {

        // When parsing an interleaved-format delta file,

        // every time decodeBody() exits, interleavedBytesExpected

        // will be decremented by the number of bytes parsed.  If it

        // reaches zero, then there is no more data expected because

        // the size of the interleaved section (given in the window

        // header) has been reached.

    }

    public void setTargetWindowStartPos(int new_start_pos) {

    // Returns the number of bytes remaining to be decoded in the target window.

    // If not in the process of decoding a window, returns 0.

    public int targetBytesRemaining() {

            // There is no window being decoded at present

        } else {

        }

    }

    // Reads the header of the window section as described in RFC sections 4.2 and

    // 4.3, up to and including the value "Length of addresses for COPYs".  If the

    // entire header is found, this function sets up the DeltaWindowSections

    // instructionsAndSizes, dataForAddAndRun, and addressesForCopy so

    // that the decoder can begin decoding the opcodes in these sections.  Returns

    // RESULT_ERROR if an error occurred, or RESULT_END_OF_DATA if the end of

    // available data was reached before the entire header could be read.  (The

    // latter may be an error condition if there is no more data available.)

    // Otherwise, returns RESULT_SUCCESS and advances parseableChunk past the

    // parsed header.

    //

    private int readHeader(ByteBuffer parseableChunk) throws IOException {

        // Here are the elements of the delta window header to be parsed,

        // from section 4 of the RFC:

        //

        //                     Window1

        //                         Win_Indicator                            - byte

        //                         [Source segment size]                    - integer

        //                         [Source segment position]                - integer

        //                         The delta encoding of the target window

        //                             Length of the delta encoding         - integer

        //                             The delta encoding

        //                                 Size of the target window        - integer

        //                                 Delta_Indicator                  - byte

        //                                 Length of data for ADDs and RUNs - integer

        //                                 Length of instructions and sizes - integer

        //                                 Length of addresses for COPYs    - integer

        //                                 Data section for ADDs and RUNs   - array of bytes

        //                                 Instructions and sizes section   - array of bytes

        //                                 Addresses section for COPYs      - array of bytes

        //

        );

        }

        }

        // Throws an exception if targetWindowWouldExceedSizeLimits

        }

        /*

        // Reserve enough space in the output string for the current target window.

        final int wanted_capacity = targetWindowStartPos + targetWindowLength;

        if (decodedTarget.capacity() < wanted_capacity) {

            decodedTarget.reserve(wanted_capacity);

        }

        */

        // Get a pointer to the start of the source segment.

            // This assignment must happen after the reserve().

            // decodedTarget should not be resized again while processing this window,

            // so sourceSegment should remain valid.

        }

        // The whole window header was found and parsed successfully.

    }

    // After the window header has been parsed as far as the Delta_Indicator,

    // this function is called to parse the following delta window header fields:

    //

    //     Length of data for ADDs and RUNs - integer (VarintBE format)

    //     Length of instructions and sizes - integer (VarintBE format)

    //     Length of addresses for COPYs    - integer (VarintBE format)

    //

    // If hasChecksum is true, it also looks for the following element:

    //

    //     Adler32 checksum            - unsigned 32-bit integer (VarintBE format)

    //

    // It sets up the DeltaWindowSections instructionsAndSizes,

    // dataForAddAndRun, and addressesForCopy.  If the interleaved format

    // is being used, all three sections will include the entire window body; if

    // the standard format is used, three non-overlapping window sections will be

    // defined.  Returns RESULT_ERROR if an error occurred, or RESULT_END_OF_DATA

    // if standard format is being used and there is not enough input data to read

    // the entire window body.  Otherwise, returns RESULT_SUCCESS.

    private int setUpWindowSections(VCDiffHeaderParser header_parser) throws IOException {

        }

        // KLUDGE: this code knows what the structure of the data looks like

                        + 1

                        + sectionLengths.add_and_run_data_length

                        + sectionLengths.addresses_length

                        + sectionLengths.instructions_and_sizes_length;

        }

                (sectionLengths.add_and_run_data_length == 0) &&

                (sectionLengths.addresses_length == 0)) {

            // The interleaved format is being used.

        } else {

            // If interleaved format is not used, then the whole window contents

            // must be available before decoding can begin.  If only part of

            // the current window is available, then report end of data

            // and re-parse the whole header when decodeChunk() is called again.

                    sectionLengths.instructions_and_sizes_length +

                    sectionLengths.addresses_length)) {

            }

            }

        }

    }

    // Decodes the body of the window section as described in RFC sections 4.3,

    // including the sections "Data section for ADDs and RUNs", "Instructions

    // and sizes section", and "Addresses section for COPYs".  These sections

    // must already have been set up by ReadWindowHeader().  Returns a

    // non-negative value on success, or RESULT_END_OF_DATA if the end of input

    // was reached before the entire window could be decoded (only possible if

    // isInterleaved() is true), or RESULT_ERROR if an error occurred during

    // decoding.  Appends as much of the decoded target window as possible to

    // parent->decodedTarget().

    //

    private int decodeBody(ByteBuffer parseable_chunk) throws IOException {

        // TODO: this was originally pointer comparison between instructionsAndSizes and parseable_chunk

            throw new IllegalStateException("Internal error: interleaved format is used, but the input pointer does not point to the instructions section");

        }

                case VCD_INSTRUCTION_END_OF_DATA:

                default:

                    break;

            }

            // The value of "size" itself could be enormous (say, INT32_MAX)

            // so check it individually against the limit to protect against

            // overflow when adding it to something else.

                        "%s with size %d plus existing %d bytes of target data exceeds length of target window (%d bytes)",

                ));

            }

            int result;

                case VCD_ADD:

                case VCD_RUN:

                case VCD_COPY:

                default:

            }

                case VCDiffHeaderParser.RESULT_END_OF_DATA:

                case VCDiffHeaderParser.RESULT_SUCCESS:

                    break;

            }

                    "Decoded target window size (%d bytes) does not match expected size (%d bytes)",

            ));

        }

            }

        }

        }

            // Standard format is being used, with three separate sections for the

            // instructions, data, and addresses.

            }

            }

            // Reached the end of the window.  Update the ParseableChunk to point to the

            // end of the addresses section, which is the last section in the window.

        } else {

            // Interleaved format is being used.

        }

    }

    // Returns the number of bytes already decoded into the target window.

    private int targetBytesDecoded() {

    }

    // Decodes a single ADD instruction, updating parent->decoded_target_.

    private int decodeAdd(int size) {

        }

        // Write the next "size" data bytes

    }

    // Decodes a single RUN instruction, updating parent->decoded_target_.

    private int decodeRun(int size) {

        }

        // Write "size" copies of the next data byte

    }

    // Decodes a single COPY instruction, updating parent->decoded_target_.

    private int decodeCopy(int size, short mode) throws IOException {

        // Keep track of the number of target bytes decoded as a local variable

        // to avoid recalculating it each time it is needed.

        final int decodedAddress;

        try {

                    here_address,

                    mode,

                    addressesForCopy

            );

        }

                    "Internal error: unexpected address %d returned from DecodeAddress, with here_address = %d",

            ));

        }

        // TODO: source_segment_length should be sourceSegment.remaining()

            // copy all data from source segment

        }

        // copy some data from target window...

            // ... plus some data from source segment

        }

        // address is now based at start of target window

        // const char* const target_segment_ptr = parent.decodedTarget().data() + targetWindowStartPos;

            // Recursive copy that extends into the yet-to-be-copied target data

            // TODO: does targetSegment need to be recreated each time?

            // This might not be needed, but refresh targetSegment since bytes were just copied into target

    }

    // When using the interleaved format, this function is called both on parsing

    // the header and on resuming after a RESULT_END_OF_DATA was returned from a

    // previous call to decodeBody().  It sets up all three section pointers to

    // reference the same interleaved stream of instructions, sizes, addresses,

    // and data.  These pointers must be reset every time that work resumes on a

    // delta window,  because the input data string may have been changed or

    // resized since decodeBody() last returned.

    private void updateInterleavedSectionPointers(ByteBuffer data) {

        // Don't read past the end of currently-available data

        }

    // If true, the interleaved format described in allowInterleaved() is used

    // for the current delta file.  Only valid after ReadWindowHeader() has been

    // called and returned a positive number (i.e., the whole header was parsed),

    // but before the window has finished decoding.

    //

    private boolean isInterleaved() {

        // If the sections are interleaved, both addressesForCopy and

        // dataForAddAndRun should point at instructionsAndSizes.

    }

    // Executes a single COPY or ADD instruction, appending data to

    // parent->decodedTarget().

    private void copyBytes(ByteBuffer buffer, int size) {

        // TODO: optimize

        }

    // Executes a single RUN instruction, appending data to

    // parent->decodedTarget().

    private void runByte(byte b, int size) {

        }

    // Advance *parseableChunk to point to the current position in the

    // instructions/sizes section.  If interleaved format is used, then

    // decrement the number of expected bytes in the instructions/sizes section

    // by the number of instruction/size bytes parsed.

    private void updateInstructionPointer(ByteBuffer parseableChunk) {

            // Reduce expected instruction segment length by bytes parsed

        }

    // The parent object which was passed to init().

    private final VCDiffStreamingDecoderImpl parent;

    // This value will be true if VCDiffDeltaFileWindow::ReadDeltaWindowHeader()

    // has been called and succeeded in parsing the delta window header, but the

    // entire window has not yet been decoded.

    private boolean foundHeader;

    // Contents and length of the current source window.  sourceSegment

    // will be non-NULL if (a) the window section header for the current window

    // has been read, but the window has not yet finished decoding; or

    // (b) the window did not specify a source segment.

    private ByteBuffer sourceSegment;

    // The delta encoding window sections as defined in RFC section 4.3.

    // The pointer for each section will be incremented as data is consumed and

    // decoded from that section.  If the interleaved format is used,

    // dataForAddAndRun and addressesForCopy will both point to

    // instructionsAndSizes; otherwise, they will be separate data sections.

    private ByteBuffer instructionsAndSizes;

    private ByteBuffer dataForAddAndRun;

    private ByteBuffer addressesForCopy;

    // The expected bytes left to decode in instructionsAndSizes.  Only used

    // for the interleaved format.

    private int interleavedBytesExpected;

    // The expected length of the target window once it has been decoded.

    private Integer targetWindowLength;

    // The index in decodedTarget at which the first byte of the current

    // target window was/will be written.

    private int targetWindowStartPos;

    // If hasChecksum is true, then expectedChecksum contains an Adler32

    // checksum of the target window data.  This is an extension included in the

    // VCDIFF 'S' (SDCH) format, but is not part of the RFC 3284 draft standard.

    private boolean hasChecksum;

}