.\"=============================================================================
.\" Header
.\"
.\" Copyright (c) 2021 Michael Baeuerle
.\"
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.\" SPDX-License-Identifier: ICU
.\"
.\"
.TH $NAME 3 $DATE Unix "$PACKAGE $VERSION manual"
.\"
.\"
.\"=============================================================================
.\" NAME section
.\"
.SH NAME
$NAME - Execute header parser
.\"
.\"
.\"=============================================================================
.\" SYNOPSIS section
.\"
.SH SYNOPSIS
.nf
.B #include <libcanlock-3/canlock-hp.h>
.sp
.BI "char *cl_hp_get_field(const char *" data ", size_t " data_len ,
.BI "                      const char *" field );
.\"
.\"
.\"=============================================================================
.\" DESCRIPTION section
.\"
.SH DESCRIPTION
Note: Consider the function
.BR cl_hp_unfold_field ()
if the header field was already extracted by another header parser (but may
still contain folding).
.PP
The
.BR cl_hp_get_field ()
function executes the header parser to extract and unfold a single header
field.
.br
This implementation executes the
.BR canlock-mhp
utility in a separate process.
.sp
The parameter
.I data
should point to the beginning of the input data.
.br
Specify the length of the input data with the
.I data_len
parameter.
.br
The name of a single header field must be specified with the
.I field
parameter.
.PP
The input data must be a message in canonical format (with US-ASCII encoded
CRLF line breaks). If the message is in some local format (e.g. EBCDIC encoded
or with LF line breaks), it must be converted to canonical format before it
can be used as input.
.PP
The input data may be a naked header without message body, but the empty line
separator after the header must always be present.
The syntax of the extracted header field is not checked beyond the folding.
The rest of the message need not be fully RFC 5536 conformant too, as long as
all header fields start on new lines (and are correctly folded, so that there
is no ambiguity). Common syntax errors (like 8-bit characters in the header)
are ignored.
.\"
.\"
.\"=============================================================================
.\" RETURN VALUE section
.\"
.SH RETURN VALUE
If the parser reports success, a pointer to the NUL-terminated output data is
returned. Otherwise,
.B NULL
is returned.
.sp
On success, the caller is responsible to
.BR free ()
the memory block allocated for the output data.
.\"
.\"
.\"=============================================================================
.\" AUTHORS section
.\"
.SH AUTHORS
Michael Baeuerle
.\"
.\"
.\"=============================================================================
.\" REPORTING BUGS section
.\"
.SH REPORTING BUGS
Report bugs to <mailto:$BUGREPORT>.
.\"
.\"
.\"=============================================================================
.\" STANDARDS section
.\"
.SH STANDARDS
.BR $NAME ()
tries to comply with the following standards:
.PP
RFC 5322, RFC 5536
.\"
.\"
.\"=============================================================================
.\" SEE ALSO section
.\"
.SH SEE ALSO
.BR free (3),
.BR cl_hp_parse_field (3),
.BR cl_hp_unfold_field (3),
.BR canlock-hfp (1),
.BR canlock-mhp (1),
.BR canlock (1)
.\"
.\"
.\" EOF
