VarExpander Class Reference

#include <elm/io/VarExpander.h>

Inheritance diagram for VarExpander:

Public Member Functions
	VarExpander ()
	VarExpander (OutStream &out)
char	escape () const
VarExpander &	escape (char e)
VarExpander &	resetBrace ()
VarExpander &	brace (char o, char c)
string	expand (string s)
int	write (const char *buffer, int size) override
int	write (char byte) override
int	flush (void) override
CString	lastErrorMessage (void) override
bool	supportsANSI () const override
Public Member Functions inherited from OutStream
virtual	~OutStream (void)

Protected Member Functions
virtual string	resolve (string name, bool &record)

Additional Inherited Members
Static Public Attributes inherited from OutStream
static OutStream &	null = _null

Detailed Description

This class a character flow filter replacing symbol invocation by the symbol value. Basically, a symbol invocation is of an escape character (default to '$') followed by a brace open character (one of '(', '{'), the symbol name and a brace close character (one of ')', '}'). This string is replaced in the character flow with the string associated with the symbol.

The association is implemented by a call to function VarExpander::resolve(). If required, the association is cached and no more call to this function is performed for this symbol. To specialize the variable expansion, one has to overload this function. The default implementation returns an empty string.

This class may be used as an OutStream or simply by passing a string and getting the result from the function VarExpander::expand().

The code below expands the variable of the chacter flow using OS environment variables:

class OSExpander: public io::VarExpander {
protected:
    string resolve(string name, bool& rec) override {
        return sys::System::getEnv(&name);
    }
};
 
OSExpander e;
sys::Path p = e.expand("${HOME}/mydir");

Constructor & Destructor Documentation

VarExpander() [1/2]

VarExpander

(

)

Default expander constructor: output is performed to starandard output.

VarExpander() [2/2]

VarExpander

(

OutStream &

out

)

Expander constructor with the given output.

Parameters

out	Output stream to use.

Member Function Documentation

brace()

VarExpander & brace ( char  o, char  c  )

inline

Added the given set of brace characters.

Parameters

o	Open brace character.
c	Close brace character.

escape() [1/2]

char escape ( ) const

inline

Get escape character.

Returns

Escape chacter.

escape() [2/2]

VarExpander & escape ( char  e )

inline

Change the escape character.

Parameters

e	new escape character.

expand()

string expand

(

string

s

)

Expand the given string.

Parameters

s	String to expand.

Returns

s with symbols expanded.

References CString::chars(), Output::flush(), String::length(), StringBuffer::stream(), String::toCString(), StringBuffer::toString(), and VarExpander::write().

Referenced by elm::io::expandOSVars().

flush()

int flush ( void  )

overridevirtual

Cause the current stream to dump its buffer to the medium.

Returns

0 for success, less than 0 for error.

Implements OutStream.

References OutStream::flush().

lastErrorMessage()

CString lastErrorMessage ( void  )

overridevirtual

Return a message for the last error.

Returns

Message of the last error.

Reimplemented from OutStream.

References OutStream::lastErrorMessage().

resetBrace()

VarExpander & resetBrace ( )

inline

Reset the list of supported open-close characters.

resolve()

string resolve ( string  name, bool &  record  )

protectedvirtual

This function has to be overridden to provide symbol definition. The default implementation just returns the empty string.

Parameters

name	Symbol name to look for.
record	If set to false, the symbol will not be cached.

Returns

Symbol value corresponding to the given symbol name.

Reimplemented in OSExpander.

Referenced by VarExpander::write().

supportsANSI()

bool supportsANSI ( ) const

overridevirtual

Test if the current stream knows how to decode ANSI special codes. The default implementation returns false.

Returns

True if ANSI code are supported, false else.

Reimplemented from OutStream.

References OutStream::supportsANSI().

write() [1/2]

int write ( char  byte )

overridevirtual

Write a byte to the stream.

Parameters

byte	Byte to write.

Returns

1 for success or less than 0 for an error.

Reimplemented from OutStream.

References elm::io::byte(), CString::chars(), String::indexOf(), String::length(), elm::io::p(), StringBuffer::reset(), VarExpander::resolve(), String::toCString(), StringBuffer::toString(), and OutStream::write().

write() [2/2]

int write ( const char *  buffer, int  size  )

overridevirtual

This is the main method of an output stream: the given buffer is put on the stream.

Parameters

buffer	Byte buffer to write.
size	Size of the byte buffer.

Returns

Number of transferred bytes or less than 0 for an error.

Implements OutStream.

Referenced by VarExpander::expand().

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

• include/elm/io/VarExpander.h
• src/io_VarExpander.cpp