tinysql::TableFile Class Reference

Reads and changes the rows of one table's data file. More...

#include <TableFile.hpp>

Public Member Functions
	TableFile (const TableSchema &schema, std::filesystem::path path)
	Prepares access to one data file.
std::vector< Row >	readRows () const
	Reads every row of the file.
long long	nextId () const
	The ID to give the next new row.
void	append (const Row &values) const
	Adds one row at the end of the file.
void	appendRows (const std::vector< Row > &rows) const
	Adds several rows at the end of the file, in one write.
std::size_t	removeRows (const std::function< bool(const Row &)> &shouldRemove) const
	Removes the rows that match a test.
std::size_t	updateRows (const std::function< bool(const Row &)> &shouldUpdate, const std::vector< std::pair< std::size_t, std::string > > &newValues) const
	Changes some columns in the rows that match a test.

Private Types
enum class	Change { Keep , Remove , Update }
	What rewrite() does with one line. More...

Private Member Functions
std::size_t	rewrite (const std::function< Change(std::string &line, const Row &row)> &decide) const
	Rewrites the file through a temporary copy, line by line.
Row	splitLine (std::string_view line) const
	Cuts one line of the file into its column values.

Private Attributes
const TableSchema &	schema_
	The table's definition.
std::filesystem::path	path_
	The data file.

Detailed Description

Reads and changes the rows of one table's data file.

Each line of the file is one row; each column sits at the fixed positions given by the schema. Changes that rewrite the file (removeRows(), updateRows()) go through a temporary file, so a crash half-way never leaves a half-written table.

Definition at line 26 of file TableFile.hpp.

Member Enumeration Documentation

Change

enum class tinysql::TableFile::Change

strongprivate

What rewrite() does with one line.

Enumerator
Keep	Write the line back unchanged.
Remove	Leave the line out.
Update	Write the line back as decide edited it.

Definition at line 71 of file TableFile.hpp.

Constructor & Destructor Documentation

TableFile()

tinysql::TableFile::TableFile	(	const TableSchema &	schema,
		std::filesystem::path	path
	)

Prepares access to one data file.

Parameters

schema	The table's definition; it must outlive this object.
path	The data file, usually from Catalog::dataFile().

Definition at line 43 of file TableFile.cpp.

Member Function Documentation

append()

void tinysql::TableFile::append

(

const Row &

values

)

const

Adds one row at the end of the file.

Parameters

values

One value per column, ID included.

Exceptions

SqlError

If the number of values is wrong, a value is too long for its column, or the file cannot be written.

Definition at line 162 of file TableFile.cpp.

appendRows()

void tinysql::TableFile::appendRows

(

const std::vector< Row > &

rows

)

const

Adds several rows at the end of the file, in one write.

Parameters

rows	The rows; each has one value per column, ID included.

Exceptions

SqlError

As append(); every row is checked before the file is touched, so a bad row adds nothing.

Definition at line 167 of file TableFile.cpp.

nextId()

long long tinysql::TableFile::nextId

(

)

const

The ID to give the next new row.

Returns

The highest numeric ID in the file plus one, or 1 for an empty or missing file.

Definition at line 149 of file TableFile.cpp.

readRows()

std::vector< Row > tinysql::TableFile::readRows

(

)

const

Reads every row of the file.

Returns

The rows, each split into one value per column; blank lines are skipped.

Exceptions

SqlError

If the file does not exist.

Definition at line 48 of file TableFile.cpp.

removeRows()

std::size_t tinysql::TableFile::removeRows

(

const std::function< bool(const Row &)> &

shouldRemove

)

const

Removes the rows that match a test.

Parameters

shouldRemove

Called for every row; returns true to remove it.

Returns

How many rows were removed.

Exceptions

SqlError

If the file does not exist or cannot be rewritten.

Definition at line 77 of file TableFile.cpp.

rewrite()

std::size_t tinysql::TableFile::rewrite ( const std::function< Change(std::string &line, const Row &row)> &  decide ) const

private

Rewrites the file through a temporary copy, line by line.

Parameters

decide

Called for every line with the raw line (which it may edit in place) and the same line split into a Row; returns what to do with that line.

Returns

How many lines were removed or edited; when 0, the file is left untouched.

Exceptions

SqlError

If the file does not exist or the temporary file cannot be written.

Definition at line 103 of file TableFile.cpp.

splitLine()

Row tinysql::TableFile::splitLine ( std::string_view  line ) const

private

Cuts one line of the file into its column values.

Parameters

line	A raw line; a line shorter than the row length gives empty values at the end.

Returns

One value per column, trailing spaces removed.

Definition at line 66 of file TableFile.cpp.

updateRows()

std::size_t tinysql::TableFile::updateRows	(	const std::function< bool(const Row &)> &	shouldUpdate,
		const std::vector< std::pair< std::size_t, std::string > > &	newValues
	)		const

Changes some columns in the rows that match a test.

Parameters

shouldUpdate	Called for every row; returns true to change it.
newValues	Pairs of (column index, new value) to set in every matching row.

Returns

How many rows were changed.

Exceptions

SqlError

If a new value is too long for its column (checked before the file is touched), or the file does not exist or cannot be rewritten.

Definition at line 82 of file TableFile.cpp.

Member Data Documentation

path_

std::filesystem::path tinysql::TableFile::path_

private

The data file.

Definition at line 90 of file TableFile.hpp.

schema_

const TableSchema& tinysql::TableFile::schema_

private

The table's definition.

Definition at line 89 of file TableFile.hpp.

---

The documentation for this class was generated from the following files:

• include/TableFile.hpp
• src/TableFile.cpp