LineReader.cpp

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/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * Written (W) 2013 Evgeniy Andreev (gsomix)
 */

#include <shogun/io/LineReader.h>
#include <cstdio>

using namespace shogun;

CLineReader::CLineReader()
{
    init();

    m_buffer=new CCircularBuffer();
}

CLineReader::CLineReader(FILE* stream, CTokenizer* tokenizer)
{
    init();

    m_stream=stream;
    m_max_token_length=10*1024*1024;

    SG_REF(tokenizer);
    m_tokenizer=tokenizer;

    m_buffer=new CCircularBuffer(m_max_token_length);
    m_buffer->set_tokenizer(m_tokenizer);
}

CLineReader::CLineReader(int32_t max_token_length, FILE* stream, CTokenizer* tokenizer)
{
    init();

    m_stream=stream;
    m_max_token_length=max_token_length;

    SG_REF(tokenizer);
    m_tokenizer=tokenizer;

    m_buffer=new CCircularBuffer(m_max_token_length);
    m_buffer->set_tokenizer(m_tokenizer);
}

CLineReader::~CLineReader()
{
    SG_UNREF(m_tokenizer);
    SG_UNREF(m_buffer);
}

bool CLineReader::has_next()
{
    if (m_stream==NULL || m_max_token_length==0 || m_tokenizer==NULL)
    {
        SG_ERROR("CLineReader::has_next():: Class is not initialized\n");
        return false;
    }

    if (ferror(m_stream))
    {
        SG_ERROR("CLineReader::has_next():: Error reading file\n");
        return false;
    }

    if (feof(m_stream) && (m_buffer->num_bytes_contained()<=0 || !m_buffer->has_next()))
        return false; // nothing to read

    return true;    
}

void CLineReader::skip_line()
{   
    int32_t bytes_to_skip=0;
    m_next_token_length=read(bytes_to_skip);
    if (m_next_token_length==-1)
        return;
    else
        m_buffer->skip_characters(bytes_to_skip);
}

SGVector<char> CLineReader::read_line()
{
    SGVector<char> line;    

    int32_t bytes_to_skip=0;
    m_next_token_length=read(bytes_to_skip);
    if (m_next_token_length==-1)
        line=SGVector<char>();
    else
    {
        m_buffer->skip_characters(bytes_to_skip);
        line=read_token(m_next_token_length-bytes_to_skip);
    }

    return line;
}

void CLineReader::reset()
{
    rewind(m_stream);
    m_buffer->clear();
}

void CLineReader::set_tokenizer(CTokenizer* tokenizer)
{
    SG_REF(tokenizer);
    SG_UNREF(m_tokenizer);
    m_tokenizer=tokenizer;

    m_buffer->set_tokenizer(tokenizer);
}

void CLineReader::init()
{
    m_buffer=NULL;
    m_tokenizer=NULL;
    m_stream=NULL;

    m_max_token_length=0;
    m_next_token_length=-1;
}

int32_t CLineReader::read(int32_t& bytes_to_skip)
{
    int32_t line_end=0;
    int32_t bytes_to_read=0;
    int32_t temp_bytes_to_skip=0;

    while (1)
    {
        if (bytes_to_skip==line_end)
            line_end=m_buffer->next_token_idx(bytes_to_skip);
        else
            line_end=m_buffer->next_token_idx(temp_bytes_to_skip);

        if (m_buffer->num_bytes_contained()!=0 && line_end<m_buffer->num_bytes_contained())
            return line_end;
        else if (m_buffer->available()==0)
            return -1; // we need some limit in case file does not contain delimiter

        // if there is no delimiter in buffer
        // try get more data from stream
        // and write it into buffer
        if (m_buffer->available() < m_max_token_length)
            bytes_to_read=m_buffer->available();
        else
            bytes_to_read=m_max_token_length;

        if (feof(m_stream))
            return line_end;
        else
            m_buffer->push(m_stream, bytes_to_read);        
        
        if (ferror(m_stream))
        {
            SG_ERROR("CLineReader::read(int32_t&):: Error reading file\n");
            return -1;
        }
    }   
}

SGVector<char> CLineReader::read_token(int32_t line_len)
{
    SGVector<char> line;

    if (line_len==0)
        line=SGVector<char>();
    else
        line=m_buffer->pop(line_len);

    return line;
}