THUAI6/CAPI/cpp/grpc/include/google/protobuf/io/gzip_stream.h

// Protocol Buffers - Google's data interchange format
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// Author: brianolson@google.com (Brian Olson)
//
// This file contains the definition for classes GzipInputStream and
// GzipOutputStream.
//
// GzipInputStream decompresses data from an underlying
// ZeroCopyInputStream and provides the decompressed data as a
// ZeroCopyInputStream.
//
// GzipOutputStream is an ZeroCopyOutputStream that compresses data to
// an underlying ZeroCopyOutputStream.

#ifndef GOOGLE_PROTOBUF_IO_GZIP_STREAM_H__
#define GOOGLE_PROTOBUF_IO_GZIP_STREAM_H__

#include <google/protobuf/stubs/common.h>
#include <google/protobuf/io/zero_copy_stream.h>
#include <google/protobuf/port.h>
#include "zlib.h"

// Must be included last.
#include <google/protobuf/port_def.inc>

namespace google
{
    namespace protobuf
    {
        namespace io
        {

            // A ZeroCopyInputStream that reads compressed data through zlib
            class PROTOBUF_EXPORT GzipInputStream PROTOBUF_FUTURE_FINAL : public ZeroCopyInputStream
            {
            public:
                // Format key for constructor
                enum Format
                {
                    // zlib will autodetect gzip header or deflate stream
                    AUTO = 0,

                    // GZIP streams have some extra header data for file attributes.
                    GZIP = 1,

                    // Simpler zlib stream format.
                    ZLIB = 2,
                };

                // buffer_size and format may be -1 for default of 64kB and GZIP format
                explicit GzipInputStream(ZeroCopyInputStream* sub_stream, Format format = AUTO, int buffer_size = -1);
                virtual ~GzipInputStream();

                // Return last error message or NULL if no error.
                inline const char* ZlibErrorMessage() const
                {
                    return zcontext_.msg;
                }
                inline int ZlibErrorCode() const
                {
                    return zerror_;
                }

                // implements ZeroCopyInputStream ----------------------------------
                bool Next(const void** data, int* size) override;
                void BackUp(int count) override;
                bool Skip(int count) override;
                int64_t ByteCount() const override;

            private:
                Format format_;

                ZeroCopyInputStream* sub_stream_;

                z_stream zcontext_;
                int zerror_;

                void* output_buffer_;
                void* output_position_;
                size_t output_buffer_length_;
                int64_t byte_count_;

                int Inflate(int flush);
                void DoNextOutput(const void** data, int* size);

                GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(GzipInputStream);
            };

            class PROTOBUF_EXPORT GzipOutputStream PROTOBUF_FUTURE_FINAL : public ZeroCopyOutputStream
            {
            public:
                // Format key for constructor
                enum Format
                {
                    // GZIP streams have some extra header data for file attributes.
                    GZIP = 1,

                    // Simpler zlib stream format.
                    ZLIB = 2,
                };

                struct PROTOBUF_EXPORT Options
                {
                    // Defaults to GZIP.
                    Format format;

                    // What size buffer to use internally.  Defaults to 64kB.
                    int buffer_size;

                    // A number between 0 and 9, where 0 is no compression and 9 is best
                    // compression.  Defaults to Z_DEFAULT_COMPRESSION (see zlib.h).
                    int compression_level;

                    // Defaults to Z_DEFAULT_STRATEGY.  Can also be set to Z_FILTERED,
                    // Z_HUFFMAN_ONLY, or Z_RLE.  See the documentation for deflateInit2 in
                    // zlib.h for definitions of these constants.
                    int compression_strategy;

                    Options();  // Initializes with default values.
                };

                // Create a GzipOutputStream with default options.
                explicit GzipOutputStream(ZeroCopyOutputStream* sub_stream);

                // Create a GzipOutputStream with the given options.
                GzipOutputStream(ZeroCopyOutputStream* sub_stream, const Options& options);

                virtual ~GzipOutputStream();

                // Return last error message or NULL if no error.
                inline const char* ZlibErrorMessage() const
                {
                    return zcontext_.msg;
                }
                inline int ZlibErrorCode() const
                {
                    return zerror_;
                }

                // Flushes data written so far to zipped data in the underlying stream.
                // It is the caller's responsibility to flush the underlying stream if
                // necessary.
                // Compression may be less efficient stopping and starting around flushes.
                // Returns true if no error.
                //
                // Please ensure that block size is > 6. Here is an excerpt from the zlib
                // doc that explains why:
                //
                // In the case of a Z_FULL_FLUSH or Z_SYNC_FLUSH, make sure that avail_out
                // is greater than six to avoid repeated flush markers due to
                // avail_out == 0 on return.
                bool Flush();

                // Writes out all data and closes the gzip stream.
                // It is the caller's responsibility to close the underlying stream if
                // necessary.
                // Returns true if no error.
                bool Close();

                // implements ZeroCopyOutputStream ---------------------------------
                bool Next(void** data, int* size) override;
                void BackUp(int count) override;
                int64_t ByteCount() const override;

            private:
                ZeroCopyOutputStream* sub_stream_;
                // Result from calling Next() on sub_stream_
                void* sub_data_;
                int sub_data_size_;

                z_stream zcontext_;
                int zerror_;
                void* input_buffer_;
                size_t input_buffer_length_;

                // Shared constructor code.
                void Init(ZeroCopyOutputStream* sub_stream, const Options& options);

                // Do some compression.
                // Takes zlib flush mode.
                // Returns zlib error code.
                int Deflate(int flush);

                GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(GzipOutputStream);
            };

        }  // namespace io
    }      // namespace protobuf
}  // namespace google

#include <google/protobuf/port_undef.inc>

#endif  // GOOGLE_PROTOBUF_IO_GZIP_STREAM_H__