TH BIO 2
SH NAME
Bopen, Bfdopen, Binit, Binits, Brdline, Brdstr, Bgetc, Bgetrune, Bgetd, Bungetc, Bungetrune, Bread, Bseek, Boffset, Bfildes, Blinelen, Bputc, Bputrune, Bprint, Bvprint, Bwrite, Bflush, Bterm, Bbuffered, Blethal \- buffered input/output
SH SYNOPSIS
ta \w'Biobuf* 'u
B #include <u.h>
br
B #include <libc.h>
br
B #include <bio.h>
PP
B
Biobuf* Bopen(char *file, int mode)
PP
B
Biobuf* Bfdopen(int fd, int mode)
PP
B
int     Binit(Biobuf *bp, int fd, int mode)
PP
B
int     Binits(Biobufhdr *bp, int fd, int mode, uchar *buf, int size)
PP
B
int     Bterm(Biobufhdr *bp)
PP
B
int     Bprint(Biobufhdr *bp, char *format, ...)
PP
B
int     Bvprint(Biobufhdr *bp, char *format, va_list arglist);
PP
B
void*   Brdline(Biobufhdr *bp, int delim)
PP
B
char*   Brdstr(Biobufhdr *bp, int delim, int nulldelim)
PP
B
int     Blinelen(Biobufhdr *bp)
PP
B
vlong   Boffset(Biobufhdr *bp)
PP
B
int     Bfildes(Biobufhdr *bp)
PP
B
int     Bgetc(Biobufhdr *bp)
PP
B
long    Bgetrune(Biobufhdr *bp)
PP
B
int     Bgetd(Biobufhdr *bp, double *d)
PP
B
int     Bungetc(Biobufhdr *bp)
PP
B
int     Bungetrune(Biobufhdr *bp)
PP
B
vlong   Bseek(Biobufhdr *bp, vlong n, int type)
PP
B
int     Bputc(Biobufhdr *bp, int c)
PP
B
int     Bputrune(Biobufhdr *bp, long c)
PP
B
long    Bread(Biobufhdr *bp, void *addr, long nbytes)
PP
B
long    Bwrite(Biobufhdr *bp, void *addr, long nbytes)
PP
B
int     Bflush(Biobufhdr *bp)
PP
B
int     Bbuffered(Biobufhdr *bp)
PP
B
void    Blethal(Biobufhdr *bp, void (*errorf)(char *))
PP
B
void    Biofn(Biobufhdr *bp, int (*iof)(Biobufhdr *, void *, long))
PP
SH DESCRIPTION
These routines implement fast buffered I/O.
I/O on different file descriptors is independent.
PP
I Bopen
opens
I file
for mode
B OREAD
or creates for mode
BR OWRITE .
It calls
IR malloc (2)
to allocate a buffer.
PP
I Bfdopen
allocates a buffer for the already-open file descriptor
I fd
for mode
B OREAD
or
BR OWRITE .
It calls
IR malloc (2)
to allocate a buffer.
PP
I Binit
initializes a standard size buffer, type
IR Biobuf ,
with the open file descriptor passed in
by the user.
I Binits
initializes a non-standard size buffer, type
IR Biobufhdr ,
with the open file descriptor,
buffer area, and buffer size passed in
by the user.
I Biobuf
and
I Biobufhdr
are related by the declaration:
IP
EX
typedef struct Biobuf Biobuf;
struct Biobuf
{
       Biobufhdr;
       uchar b[Bungetsize+Bsize];
};
EE
PP
Arguments
of types pointer to Biobuf and pointer to Biobufhdr
can be used interchangeably in the following routines.
PP
IR Bopen ,
IR Binit ,
or
I Binits
should be called before any of the
other routines on that buffer.
I Bfildes
returns the integer file descriptor of the associated open file.
PP
I Bterm
flushes the buffer for
I bp
and returns
IR Bflush 's
return value.
If the buffer was allocated by
I Bopen
or
IR Bfdopen ,
the buffer is
I freed
and the file is closed.
PP
I Brdline
reads a string from the file associated with
I bp
up to and including the first
I delim
character.
The delimiter character at the end of the line is
not altered, thus the returned string probably won't be NUL-terminated.
I Brdline
returns a pointer to the start of the line or
L 0
on end-of-file or read error.
I Blinelen
returns the length (including the delimiter)
of the most recent string returned by
IR Brdline .
PP
I Brdstr
returns a
IR malloc (2)-allocated
buffer containing the next line of input delimited by
IR delim ,
terminated by a NUL (0) byte.
Unlike
IR Brdline ,
which returns when its buffer is full even if no delimiter has been found,
I Brdstr
will return an arbitrarily long line in a single call.
If
I nulldelim
is set, the terminal delimiter will be overwritten with a NUL.
After a successful call to
IR Brdstr ,
the return value of
I Blinelen
will be the length of the returned buffer, excluding the NUL.
PP
I Bgetc
returns the next character from
IR bp ,
or a negative value
at end of file.
I Bungetc
may be called immediately after
I Bgetc
to allow the same character to be reread.
PP
I Bgetrune
calls
I Bgetc
to read the bytes of the next
SM UTF
sequence in the input stream and returns the value of the rune
represented by the sequence.
It returns a negative value
at end of file.
I Bungetrune
may be called immediately after
I Bgetrune
to allow the same
SM UTF
sequence to be reread as either bytes or a rune.
I Bungetc
and
I Bungetrune
may back up a maximum of five bytes.
PP
I Bgetd
uses
I charstod
(see
IR atof (2))
and
I Bgetc
to read the formatted
floating-point number in the input stream,
skipping initial blanks and tabs.
The value is stored in
BR *d.
PP
I Bread
reads
I nbytes
of data from
I bp
into memory starting at
IR addr .
The number of bytes read is returned on success
and a negative value is returned if a read error occurred.
PP
I Bseek
applies
IR seek (2)
to
IR bp .
It returns the new file offset.
I Boffset
returns the file offset of the next character to be processed.
PP
I Bputc
outputs the low order 8 bits of
I c
on
IR bp .
If this causes a
I write
to occur and there is an error,
a negative value is returned.
Otherwise, a zero is returned.
PP
I Bputrune
calls
I Bputc
to output the low order
16 bits of
I c
as a rune
in
SM UTF
format
on the output stream.
PP
I Bprint
is a buffered interface to
IR print (2).
If this causes a
I write
to occur and there is an error,
a negative value
RB ( Beof )
is returned.
Otherwise,
I Bprint
returns the number of bytes written.
I Bvprint
does the same except it takes as argument a
B va_list
parameter, so it can be called within a variadic function.
PP
I Bwrite
outputs
I nbytes
of data starting at
I addr
to
IR bp .
If this causes a
I write
to occur and there is an error,
a negative value is returned.
Otherwise, the number of bytes written is returned.
PP
I Bflush
causes any buffered output associated with
I bp
to be written.
The return is as for
IR Bputc .
I Bflush
is called on
exit for every buffer still open
for writing.
PP
I Bbuffered
returns the number of bytes in the buffer.
When reading, this is the number of bytes still available from the last
read on the file; when writing, it is the number of bytes ready to be
written.
PP
I Blethal
arranges
I errorf
to be called in case of an error happening on read/write.
An argument of
B nil
will have the program terminated in case of error.
PP
If
I Biofn
is called with a non-nil
I iof
function, then that function is called for I/O in lieu of
IR read (2)
and
IR write .
A nil argument for
I iof
restores normal behaviour.
SH SOURCE
B /sys/src/libbio
SH SEE ALSO
IR open (2),
IR read (2),
IR print (2),
IR exits (2),
IR utf (6),
SH DIAGNOSTICS
I Bio
routines that return integers yield
B Beof
if
I bp
is not the descriptor of an open file.
I Bopen
returns zero if the file cannot be opened in the given mode.
All routines set
I errstr
on error.
PP
An error during read or write will call an error handler specified by
IR Blethal ,
if any.
SH BUGS
I Brdline
returns an error on strings longer than the buffer associated
with the file
and also if the end-of-file is encountered
before a delimiter.
I Blinelen
will tell how many characters are available
in these cases.
In the case of a true end-of-file,
I Blinelen
will return zero.
At the cost of allocating a buffer,
I Brdstr
sidesteps these issues.
PP
Only the low byte of
IR Brdstr 's
I delim
is examined, so
I delim
cannot be an arbitrary rune.
PP
The data returned by
I Brdline
may be overwritten by calls to any other
I bio
routine on the same
IR bp.

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