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includefile(header.inc)
COMMENT(manpage, section, releasedate, archive, short name)
manpage(FBB::CGI)(3bobcat)(_CurYrs_)(libbobcat1-dev__CurVers_-x.tar.gz)
(CGI interface)
manpagename(FBB::CGI)(handles GET and POST submitted form data)
manpagesynopsis()
bf(#include <bobcat/cgi>)nl()
Linking option: tt(-lbobcat)
manpagedescription()
The class tt(CGI) offers an interface to data submitted by web-forms. The
data is sent to a script handling the data using a tt(<form
action="/path/to/form/script">) stanza. Very often this is indeed a script,
like a Perl script, but there is no need to use a scripting language. The
class tt(CGI) allows bf(C++) programmers to process the form by an executable
which usually results in faster processing and at construction time benefits
from the type safety offered by bf(C++). The class tt(CGI) handles data
submitted using the tt(GET) method as well as data submitted using the
tt(POST) method automatically.
By default the class's constructor writes the customary tt(Content-type)
header lines to the standard output stream. Additional (html) output of a
reply page must be provided by other code. Therefore, a program processing an
uploaded form will have an organization comparable to the following basic
setup:
verb(
// assume includes and namespace std/FBB were defined
int main()
{
CGI cgi;
cout << "<html><body>\n";
if (parametersOK(cgi))
{
process(cgi);
generateReplyPage();
}
else
generateErrorPage();
cout << "</body></html>\n;
}
)
When errors in the received form-data are detected an error message is
written to the standard output stream and an tt(FBB::Errno) exception is
thrown.
includefile(namespace.inc)
manpagesection(INHERITS FROM)
-
manpagesection(TYPEDEF)
itemization(
itb(CGI::MapStringVector)
A shorthand for tt(std::map<std::string, std::vector<std::string> >),
which is the data type in which form-variables are stored.
)
manpagesection(ENUMERATIONS)
The tt(CGI::Method) enumeration specifies values indicating the way the
form's data were submitted:
itemization(
itb(CGI::UNDETERMINED)
Used internally indicating that the form's method was neither tt(GET)
nor tt(POST).
itb(CGI::GET)
Indicates that the tt(GET) method was used when submitting the form's
data;
itb(CGI::POST)
Indicates that the tt(POST) method was used when submitting the form's
data.
)
The tt(CGI::Create) enumeration is used to request or suppress creation of
the directory to contain any file uploaded by a form:
itemization(
itb(CGI::DONT_CREATE_PATH)
When uploading files, the destination directory must exist;
itb(CGI::CREATE_PATH)
When uploading files, the destination directory will be created.
)
manpagesection(CONSTRUCTORS)
itemization(
itb(CGI(bool defaultEscape = true,
char const *header = "Content-type: text/html",
std::ostream &out = std::cout))
The default constructor writes the standard content type header to the
standard output stream and will use tt(std::cout) for output. Specifying tt(0)
as header suppresses outputting the tt(Content-type) line. Otherwise the
content type line is also followed by two tt(\r\n) character combinations. By
default all characters in retrieved form-variables are escaped. The overloaded
insertion operators (see below) can be used to modify the default set of
characters which will be escaped. The backslash is the escape character. It
will be used unescaped only if the tt(defaultEscape) value is specified as
tt(false) and no insertions were performed.
)
The copy constructor is available.
manpagesection(OERLOADED OPERATORS)
bf(Note:) the following three insertion operators defining sets of
characters that should be escaped can only be used until the first time one of
the tt(param(), begin()) or tt(end()) members is called. Once one of these
latter three members has been called the set of characters to be escaped is
fixed and attempts to modify them will fail silently.
itemization(
itb(CGI &operator<<(std::string const &accept))
This member's actions are suppressed once tt(param(), begin()) or
tt(end()) (see below) has been called.
The insertion operator can be used to fine-tune the set of characters
that will be shown escaped in strings returned by tt(param()) (see
below). Depending on the value of the constructor's tt(defaultEscape)
parameter characters inserted into the tt(CGI) object will or will not
be escaped by a backslash. If the constructor's tt(defaultEscape)
parameter was specified as tt(true) then the insertion operator will
define a set of characters that will em(not) be escaped. If
tt(defaultEscape) was specified as tt(false) then the insertion
operator will define a set of characters that em(will) be
escaped. Once an insertion operator has been used the backlash itself
will always be escaped and a request to use it unescaped is silently
ignored. The tt(accept) string can be specified as a regular
expression character set without specifying the surrounding square
brackets. E.g., an insertion like tt(cgi << "-a-z0-9") will accept the
dash, lower case letters and the digits. Individual characters,
character ranges using the dash and all standard character classes
(tt([:alnum:], [:alpha:], [:cntrl:], [:digit:], [:graph:], [:lower:],
[:print:], [:punct:], [:space:], [:upper:]), and tt([:xdigit:])) can be
used to specify a set of characters. In addition to these standard
character classes the class tt([:cgi:]) is available representing the
set tt(" ' ` ;) and tt(\). Note that standard character classes
em(do) require you to specify square brackets. When a series of
insertions are performed then the union of the sets defined by these
insertions are used. bf(Note): using unescaped single quotes, the
double quotes, backtick characters and semicolons in CGI-programs
might be risky and is not advised.
itb(CGI &operator<<(int c))
This member's actions are suppressed once tt(param(), begin()) or
tt(end()) (see below) has been called.
This insertion operator is used to change the default escape handling
of a single character tt(c). The tt(int) parameter is cast internally
to a tt(char).
itb(CGI &operator<<(std::pair<char, char> range))
This member's actions are suppressed once tt(param(), begin()) or
tt(end()) (see below) has been called.
This insertion operator can be used to change the default escape
handling of a range of characters. The pair's second character must be
equal to or exceed the position of the pair's first character in the
ASCII collating sequence or the member will have no effect.
itb(std::ostream &std::operator<<(std::ostream &out, CGI const &cgi))
tt(CGI) objects can be inserted into tt(ostreams) to display the
characters that will appear escaped in strings returned by the
tt(param()) member function. Each character for which tt(isprint())
returns tt(true) will be displayed as character, surrounded by single
quotes. For all other characters their ASCII values are displayed.
Each character is displayed on a line by itself.
itb(char const *operator[](std::string const &key) const)
The index operator returns the value of the environment variable
specified as the index. An empty string is returned if the variable
specified at tt(key) is not defined.
)
The assignment operator is available.
manpagesection(MEMBER FUNCTIONS)
itemization(
itb(CGI::MapStringVector::const_iterator begin() const)
Returns the begin iterator of the form's parameter map. Iterator values
unequal tt(end()) (see below) point to a pair of values, the first of
which is the name of a field defined by the form, the second is a
vector of strings containing the field's value(s). See also the
description of the tt(param()) member below.
itb(CGI::MapStringVector::const_iterator end() const)
Returns the end iterator of the form's parameter map.
itb(unsigned long long maxUploadSize() const)
Returns the current maximum file upload size in bytes.
itb(CGI::Method method() const)
Returns the method used when submitting the form as either tt(CGI::GET)
or tt(CGI::POST).
itb(std::string const &query() const)
Returns the query-string submitted with tt(CGI::GET) or tt(CGI::POST)
forms (if the tt(POST)ed form specified
tt(ENCTYPE="multipart/form-data") the query string is empty).
itb(std::vector<std::string> const ¶m(std::string const &variable)
const)
Returns the value of the form-variable specified by the function's
argument. An empty vector is returned if the variable was not provided
by the form's data. If the same variable was specified multiple times
or if its value extends over multiple lines (only with
tt(multipart/form-data)) then the vector will contain multiple
strings. With tt(GET) and tt(POST) methods not using
tt(multipart/form-data) input fields extending over multiple lines are
stored in one string, using tt(\r\n) combinations between those
lines.
nl() When files are uploaded the vectors contain sets of four
strings. The first string provides the path nme of the uploaded file;
the second string provides the file name specified in the form itself
(so it is the name of the file at the remote location); the third
string shows the content type specified by the remote browser (e.g.,
tt(application/octet-stream)), the fourth string contains tt(OK) if
the file was successfully uploaded and tt(truncated) if the file was
truncated. Existing files will not be overwritten. When uploading a
file a usable filename must be found within 100 trials.
itb(void setFileDestination(std::string const &path,
std::string const &prefix = "",
Create create = CREATE_PATH))
This member is used to specify the path and prefix of uploaded
files. Uploaded files will be stored at tt(path/prefixNr) where tt(Nr)
is an internally used number starting at one. When tt(CREATE_PATH) is
specified tt(path) must be available or the bf(CGI) object must be
able to create the path. If tt(DONT_CREATE_PATH) is specified the
specified path must be available. If not, an tt(FBB::Errno) exception
will be thrown.
itb(void setMaxUploadSize(size_t maxSize, int unit = 'M'))
This member can be used to change the maximum size of uploaded
files. Its default value is 100Mb. The tt(unit) can be one of tt(b)
(bytes, the default), tt(K) (Kbytes), tt(M) (Mbytes) or tt(G)
(Gbytes). Unit-specifiers are interpreted case insensitively. File
uploads will continue until the maximum upload size is exceeded,
followed by discarding any remainder.
)
The first time one of the tt(param(), begin()) or tt(end()) members is
called these members may detect errors in the the received form data. If so,
an error message is written to the standard output stream and an
tt(FBB::Errno) exception will be thrown.
manpagesection(EXAMPLE)
verbinclude(../../cgi/driver/driver.cc)
To test the program provide it, e.g., with the following file at its standard
input:
verbinclude(../../cgi/driver/get)
manpagefiles()
em(bobcat/cgi) - defines the class interface
manpageseealso()
bf(bobcat)(7)
manpagebugs()
None Reported.
includefile(trailer.inc)
|
