# Poco::Net

# class MessageHeader

Library: Net
Package: Messages
Header: Poco/Net/MessageHeader.h

## Description

A collection of name-value pairs that are used in various internet protocols like HTTP and SMTP.

The name is case-insensitive.

There can be more than one name-value pair with the same name.

MessageHeader supports writing and reading the header data in RFC 2822 format.

The maximum number of fields can be restricted by calling setFieldLimit(). This is useful to defend against certain kinds of denial-of-service attacks. The limit is only enforced when parsing header fields from a stream, not when programmatically adding them. The default limit is 100.

## Inheritance

Direct Base Classes: NameValueCollection

All Base Classes: NameValueCollection

Known Derived Classes: HTTPMessage, HTTPRequest, HTTPResponse, HTTPServerRequest, HTTPServerRequestImpl, HTTPServerResponseImpl, HTTPServerResponse, MailMessage

## Member Summary

Member Functions: getFieldLimit, hasToken, operator =, quote, read, setFieldLimit, splitElements, splitParameters, write

Inherited Functions: add, begin, clear, empty, end, erase, find, get, has, operator =, operator [], set, size, swap

## Constructors

### MessageHeader

MessageHeader();

Creates the MessageHeader.

### MessageHeader

MessageHeader(
const MessageHeader & messageHeader
);

Creates the MessageHeader by copying another one.

## Destructor

### ~MessageHeader

virtual ~MessageHeader();

Destroys the MessageHeader.

## Member Functions

### getFieldLimit

int getFieldLimit() const;

Returns the maximum number of header fields allowed.

See setFieldLimit() for more information.

### hasToken

bool hasToken(
const std::string & fieldName,
const std::string & token
) const;

Returns true if and only if the field with the given fieldName contains the given token. Tokens in a header field are expected to be comma-separated and are case insensitive.

### operator =

MessageHeader & operator = (
const MessageHeader & messageHeader
);

Assigns the content of another MessageHeader.

### quote

static void quote(
const std::string & value,
std::string & result,
bool allowSpace = false
);

Checks if the value must be quoted. If so, the value is appended to result, enclosed in double-quotes. Otherwise, the value is appended to result as-is.

### read

virtual void read(
std::istream & istr
);

Reads the message header from the given input stream.

See write() for the expected format. Also supported is folding of field content, according to section 2.2.3 of RFC 2822.

Reading stops at the first empty line (a line only containing \r\n or \n), as well as at the end of the stream.

Some basic sanity checking of the input stream is performed.

Throws a MessageException if the input stream is malformed.

### setFieldLimit

void setFieldLimit(
int limit
);

Sets the maximum number of header fields allowed. This limit is used to defend certain kinds of denial-of-service attacks. Specify 0 for unlimited (not recommended).

The default limit is 100.

### splitElements

static void splitElements(
const std::string & s,
std::vector < std::string > & elements,
bool ignoreEmpty = true
);

Splits the given string into separate elements. Elements are expected to be separated by commas.

For example, the string

    text/plain; q=0.5, text/html, text/x-dvi; q=0.8

is split into the elements

    text/plain; q=0.5
    text/html
    text/x-dvi; q=0.8

Commas enclosed in double quotes do not split elements.

If ignoreEmpty is true, empty elements are not returned.

### splitParameters

static void splitParameters(
const std::string & s,
std::string & value,
NameValueCollection & parameters
);

Splits the given string into a value and a collection of parameters. Parameters are expected to be separated by semicolons.

Enclosing quotes of parameter values are removed.

For example, the string

    multipart/mixed; boundary="MIME_boundary_01234567"

is split into the value

    multipart/mixed

and the parameter

    boundary -> MIME_boundary_01234567

### splitParameters

static void splitParameters(
const std::string::const_iterator & begin,
const std::string::const_iterator & end,
NameValueCollection & parameters
);

Splits the given string into a collection of parameters. Parameters are expected to be separated by semicolons.

Enclosing quotes of parameter values are removed.

### write

virtual void write(
std::ostream & ostr
) const;

Writes the message header to the given output stream.

The format is one name-value pair per line, with name and value separated by a colon and lines delimited by a carriage return and a linefeed character. See RFC 2822 for details.