=head1 NAME

qio - Quick I/O routines for reading files

=head1 SYNOPSIS

B<#include E<lt>inn/qio.hE<gt>>

B<QIOSTATE *QIOopen(const char *>I<name>B<);>

B<QIOSTATE *QIOfdopen(int> I<fd>B<);>

B<void QIOclose(QIOSTATE *>I<qp>B<);>

B<char *QIOread(QIOSTATE *>I<qp>B<);>

B<int QIOfileno(QIOSTATE *>I<qp>B<);>

B<size_t QIOlength(QIOSTATE *>I<qp>B<);>

B<int QIOrewind(QIOSTATE *>I<qp>B<);>

B<off_t QIOtell(QIOSTATE *>I<qp>B<);>

B<bool QIOerror(QIOSTATE *>I<qp>B<);>

B<bool QIOtoolong(QIOSTATE *>I<qp>B<);>

=head1 DESCRIPTION

The routines described in this manual page are part of libinn(3).  They
are used to provide quick read access to files; the QIO routines use
buffering adapted to the block size of the device, similar to stdio, but
with a more convenient syntax for reading newline-terminated lines.  QIO
is short for "Quick I/O" (a bit of a misnomer, as QIO provides read-only
access to files only).

The QIOSTATE structure returned by B<QIOopen> and B<QIOfdopen> is the
analog to stdio's FILE structure and should be treated as a black box by
all users of these routines.  Only the above API should be used.

B<QIOopen> opens the given file for reading.  For regular files, if your
system provides that information and the size is reasonable, QIO will use
the block size of the underlying file system as its buffer size;
otherwise, it will default to a buffer of 8 KB.  Returns a pointer to use
for subsequent calls, or NULL on error.  B<QIOfdopen> performs the same
operation except on an already-open file descriptor (I<fd> must designate
a file open for reading).

B<QIOclose> closes the open file and releases any resources used by the
QIOSTATE structure.  The QIOSTATE pointer should not be used again after
it has been passed to this function.

B<QIOread> reads the next newline-terminated line in the file and returns
a pointer to it, with the trailing newline replaced by nul.  The returned
pointer is a pointer into a buffer in the QIOSTATE object and therefore
will remain valid until B<QIOclose> is called on that object.  If EOF is
reached, an error occurs, or if the line is longer than the buffer size,
NULL is returned instead.  To distinguish between the error cases, use
B<QIOerror> and B<QIOtoolong>.

B<QIOfileno> returns the descriptor of the open file.

B<QIOlength> returns the length in bytes of the last line returned by
B<QIOread>.  Its return value is only defined after a successful call to
B<QIOread>.

B<QIOrewind> sets the read pointer back to the beginning of the file and
reads the first block of the file in anticipation of future reads.  It
returns 0 if successful and -1 on error.

B<QIOtell> returns the current value of the read pointer (the lseek(2)
offset at which the next line will start).

B<QIOerror> returns true if there was an error in the last call to
B<QIOread>, false otherwise.  B<QIOtoolong> returns true if there was an
error and the error was that the line was too long.  If B<QIOread> returns
NULL, these functions should be called to determine what happened.  If
B<QIOread> returned NULL and B<QIOerror> is false, EOF was reached.  Note
that if B<QIOtoolong> returns true, the next call to B<QIOread> will try
to read the remainder of the line and will likely return a partial line;
users of this library should in general treat long lines as fatal errors.

=head1 EXAMPLES

This block of code opens F</etc/motd> and reads it a line at a time,
printing out each line preceeded by its offset in the file.

    QIOSTATE *qp;
    off_t offset;
    char *p;

    qp = QIOopen("/etc/motd");
    if (qp == NULL) {
        perror("Open error");
        exit(1);
    }
    for (p = QIOread(qp); p != NULL; p = QIOread(qp))
        printf("%ld: %s\n", (unsigned long) QIOtell(qp), p);
    if (QIOerror(qp)) {
        perror("Read error");
        exit(1);
    }
    QIOclose(qp);

=head1 HISTORY

Written by Rich $alz <rsalz@uunet.uu.net> for InterNetNews.  Updated by
Russ Allbery <rra@stanford.edu>.

$Id: qio.pod 5909 2002-12-03 05:17:18Z vinocur $