streamParserFromFileName {qmrparser}

Creates a streamParser from a file name

Description

Creates a list of functions which allow streamParser manipulation (when defined from a file name)

Usage

streamParserFromFileName(fileName,encoding = getOption("encoding")) 

Arguments

fileName

file name

encoding

file encoding

Details

See streamParser

This function implementation uses function seek.

Documentation about this function states:

" Use of 'seek' on Windows is discouraged. We have found so many errors in the Windows implementation of file positioning that users are advised to use it only at their own risk, and asked not to waste the R developers' time with bug reports on Windows' deficiencies. "

If "fileName" is a url, seek is not possible.

In order to cover these situations, streamPaserFromFileName functions are converted in:

streamParserFromString(readLines( fileName, encoding=encoding))

Alternatively, it can be used:

streamParserFromString with: streamParserFromString(readLines(fileName))

or

streamParserFromString( iconv(readLines(fileName), encodingOrigen,encodingDestino) )

Since streamParserFromFileName also uses readChar, this last option is the one advised in Linux if encoding is different from Latin-1 or UTF-8. As documentation states, readChar may generate problems if file is in a multi-byte non UTF-8 encoding:

" 'nchars' will be interpreted in bytes not characters in a non-UTF-8 multi-byte locale, with a warning. "

Value

A list of four functions which allow stream manipulation:

streamParserNextChar

Function which takes a streamParser as argument and returns a list(status,char,stream)

streamParserNextCharSeq

Function which takes a streamParser as argument and returns list(status,char,stream)

streamParserPosition

Function which takes a streamParser as argument and returns position of next character to be read

streamParserClose

Closes the stream

Examples

  name    <- system.file("extdata","datInTest01.txt", package = "qmrparser")
  
  stream  <- streamParserFromFileName(name)
  
  cstream <- streamParserNextChar(stream)
  
  while( cstream$status == "ok" ) {
    print(streamParserPosition(cstream$stream))
    print(cstream$char)
    cstream <- streamParserNextCharSeq(cstream$stream)
  }
  
  streamParserClose(stream)