src/json2pb/zero_copy_stream_reader.h

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

#ifndef  BRPC_JSON2PB_ZERO_COPY_STREAM_READER_H
#define  BRPC_JSON2PB_ZERO_COPY_STREAM_READER_H

#include <google/protobuf/io/zero_copy_stream.h> // ZeroCopyInputStream

namespace json2pb {

class ZeroCopyStreamReader {
public:
    typedef char Ch;
    ZeroCopyStreamReader(google::protobuf::io::ZeroCopyInputStream *stream)
            : _data(NULL), _data_size(0), _nread(0), _stream(stream) {
    }
    //Take a charactor and return its address.
    const char* PeekAddr() { 
        if (!ReadBlockTail()) {
            return _data;
        }
        while (_stream->Next((const void **)&_data, &_data_size)) {
            if (!ReadBlockTail()) {
                return _data;
            }
        }
        return NULL;
    }
    const char* TakeWithAddr() {
        const char* c = PeekAddr();
        if (c) {
            ++_nread;
            --_data_size;
            return _data++;
        }
        return NULL;
    }
    char Take() {
        const char* c = PeekAddr();
        if (c) {
            ++_nread;
            --_data_size;
            ++_data;
            return *c;
        }
        return '\0';
    }
    
    char Peek() {
        const char* c = PeekAddr();
        return (c ? *c : '\0');
    }
    //Tell whether read the end of this block.
    bool ReadBlockTail() {
        return !_data_size;
    }
    size_t Tell() { return _nread; }
    void Put(char) {}
    void Flush() {}
    char *PutBegin() { return NULL; }
    size_t PutEnd(char *) { return 0; }
private:
    const char *_data;
    int _data_size;
    size_t _nread;
    google::protobuf::io::ZeroCopyInputStream *_stream;
};

} // namespace json2pb

#endif  //BRPC_JSON2PB_ZERO_COPY_STREAM_READER_H