PointWriter module

Module contents

class PointWriter

Write points of any type as delimited text.

This class writes a sequence of points to a file in delimited text format. You can control the destination, the delimiter, the record separator (usually newline) and whether or not a header line is written.

The header line contains information about the point’s dimension, coordinate system, object ID and timestamp (for trajectory points) and custom properties (if any).

Public Functions

PointWriter()

PointWriter(PointWriter const &other)

PointWriter(std::ostream &_output)

PointWriter &operator=(PointWriter const &other)

bool operator==(PointWriter const &other) const

bool operator!=(PointWriter const &other) const

void set_output(std::ostream &out)

Set the stream where points will be written.

This can be any std::ostream.

NOTE: You are resposible for ensuring that the stream does not go out of scope until you are done writing points.

Parameters

• [in] out: Stream where points will be written

std::ostream &output() const

Return the stream where points will be written.

void set_field_delimiter(string_type const &delim)

Set the field delimiter.

This string will be inserted between each field as points are written.

Parameters

• [in] delim: Delimiter string

string_type field_delimiter() const

Return the field delimiter.

void set_record_delimiter(string_type const &sep)

Set the record separator (end-of-line string)

This string will be written after each point. By default it’s std::endl (the newline string).

Parameters

• [in] sep: String separator

void set_timestamp_format(string_type const &format)

Set format for writing timestamps.

There are as many ways to write timestamps as there are programs to write them. We have our default (YYYY-MM-DD HH:MM:SS) but sometimes you will need to specify some other format for interoperability.

This method sets a format string for timestamps using the flags in boost::date_time::time_facet. If you do not call it,

Parameters

• [in] format: Format string for timestamps

string_type timestamp_format() const

string_type record_delimiter() const

Return the record separator (end-of-line string)

void set_quote_character(string_type const &quotes)

Set the quote character.

This character may be used to enclose a field containing lots of characters that would otherwise need to be escaped. We have to know what it is so that we can escape it ourselves when we encounter the quote character inside fields.

Parameters

• [in] quotes: Zero or one character to be used as quotation marks

string_type quote_character() const

Return the current quote characters.

void set_write_header(bool onoff)

Set whether or not to write a header.

The header string describes the contents of a point: coordinate system, properties (if any), number of coordinates. By default it will be written at the beginning of a sequence of points. You can turn it off with this function.

Parameters

• [in] onoff: Boolean flag

bool write_header() const

Return whether or not the header will be written.

template<typename point_iter_type>
int write(point_iter_type point_begin, point_iter_type point_end)

void set_coordinate_precision(std::size_t num_digits)

Set the decimal precision for writing coordinates.

Internally, Tracktable stores coordinates as double-precision floating numbers. It is highly unlikely that trajectory data needs absolutely all of that precision. Since it takes up lots of space when we write data to disk, it is useful to be able to ask for reduced (or increased) precision.

Parameters

• [in] num_digits: Number of digits of precision

std::size_t coordinate_precision() const

void set_null_value(string_type const &_null_value)

Set the string representation for nulls.

Property values that were never set are considered to hold a null value. This method lets you set how nulls will be written to disk. The default value is the empty string “”.

Parameters

• [in] _null_value: Desired string representation of nulls

string_type null_value() const

Private Functions

void set_default_configuration()

template<typename point_type, typename out_iter_type>
void write_point_header_tokens(point_type const &example_point, out_iter_type _output)

template<typename point_iter_type, typename out_iter_type>
int write_many_points_to_tokens(point_iter_type point_begin, point_iter_type point_end, out_iter_type _output)

template<typename point_type, typename out_iter_type>
void write_point_tokens(point_type const &point, out_iter_type _output, std::size_t num_properties_expected)

template<typename token_iter_type>
void write_tokens_to_stream(token_iter_type begin, token_iter_type end)

Private Members

std::size_t CoordinatePrecision

PropertyConverter PropertyWriter

string_type TimestampFormat

TokenWriter TokenSink

bool WriteHeader

Friends

friend tracktable::PointWriter::TrajectoryWriter