BIO(2) BIO(2)
NAME
Bopen, Binit, Binits, Brdline, Brdstr, Bgetc, Bgetrune,
Bgetd, Bungetc, Bungetrune, Bread, Bseek, Boffset, Bfildes,
Blinelen, Bputc, Bputrune, Bprint, Bvprint, Bwrite, Bflush,
Bterm, Bbuffered - buffered input/output
SYNOPSIS
#include <u.h>
#include <libc.h>
#include <bio.h>
Biobuf* Bopen(char *file, int mode)
int Binit(Biobuf *bp, int fd, int mode)
int Binits(Biobufhdr *bp, int fd, int mode, uchar *buf,
int size)
int Bterm(Biobufhdr *bp)
int Bprint(Biobufhdr *bp, char *format, ...)
int Bvprint(Biobufhdr *bp, char *format, va_list
arglist);
void* Brdline(Biobufhdr *bp, int delim)
char* Brdstr(Biobufhdr *bp, int delim, int nulldelim)
int Blinelen(Biobufhdr *bp)
vlong Boffset(Biobufhdr *bp)
int Bfildes(Biobufhdr *bp)
int Bgetc(Biobufhdr *bp)
long Bgetrune(Biobufhdr *bp)
int Bgetd(Biobufhdr *bp, double *d)
int Bungetc(Biobufhdr *bp)
int Bungetrune(Biobufhdr *bp)
vlong Bseek(Biobufhdr *bp, vlong n, int type)
int Bputc(Biobufhdr *bp, int c)
int Bputrune(Biobufhdr *bp, long c)
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long Bread(Biobufhdr *bp, void *addr, long nbytes)
long Bwrite(Biobufhdr *bp, void *addr, long nbytes)
int Bflush(Biobufhdr *bp)
int Bbuffered(Biobufhdr *bp)
DESCRIPTION
These routines implement fast buffered I/O. I/O on differ-
ent file descriptors is independent.
Bopen opens file for mode OREAD or creates for mode OWRITE.
It calls malloc(2) to allocate a buffer.
Binit initializes a standard size buffer, type Biobuf, with
the open file descriptor passed in by the user. Binits ini-
tializes a non-standard size buffer, type Biobufhdr, with
the open file descriptor, buffer area, and buffer size
passed in by the user. Biobuf and Biobufhdr are related by
the declaration:
typedef struct Biobuf Biobuf;
struct Biobuf
{
Biobufhdr;
uchar b[Bungetsize+Bsize];
};
Arguments of types pointer to Biobuf and pointer to
Biobufhdr can be used interchangeably in the following rou-
tines.
Bopen, Binit, or Binits should be called before any of the
other routines on that buffer. Bfildes returns the integer
file descriptor of the associated open file.
Bterm flushes the buffer for bp and returns Bflush's return
value. If the buffer was allocated by Bopen, the buffer is
freed and the file is closed.
Brdline reads a string from the file associated with bp up
to and including the first delim character. The delimiter
character at the end of the line is not altered, thus the
returned string probably won't be NUL-terminated. Brdline
returns a pointer to the start of the line or `0' on end-
of-file or read error. Blinelen returns the length (includ-
ing the delimiter) of the most recent string returned by
Brdline.
Brdstr returns a malloc(2)-allocated buffer containing the
next line of input delimited by delim, terminated by a NUL
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(0) byte. Unlike Brdline, which returns when its buffer is
full even if no delimiter has been found, Brdstr will return
an arbitrarily long line in a single call. If nulldelim is
set, the terminal delimiter will be overwritten with a NUL.
After a successful call to Brdstr, the return value of
Blinelen will be the length of the returned buffer, exclud-
ing the NUL.
Bgetc returns the next character from bp, or a negative
value at end of file. Bungetc may be called immediately
after Bgetc to allow the same character to be reread.
Bgetrune calls Bgetc to read the bytes of the next 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. Bungetrune may be called immediately
after Bgetrune to allow the same UTF sequence to be reread
as either bytes or a rune. Bungetc and Bungetrune may back
up a maximum of five bytes.
Bgetd uses charstod (see atof(2)) and Bgetc to read the for-
matted floating-point number in the input stream, skipping
initial blanks and tabs. The value is stored in *d.
Bread reads nbytes of data from bp into memory starting at
addr. The number of bytes read is returned on success and a
negative value is returned if a read error occurred.
Bseek applies seek(2) to bp. It returns the new file offset.
Boffset returns the file offset of the next character to be
processed.
Bputc outputs the low order 8 bits of c on bp. If this
causes a write to occur and there is an error, a negative
value is returned. Otherwise, a zero is returned.
Bputrune calls Bputc to output the low order 21 bits of c as
a rune in UTF format on the output stream.
Bprint is a buffered interface to print(2). If this causes a
write to occur and there is an error, a negative value
(Beof) is returned. Otherwise, Bprint returns the number of
bytes written. Bvprint does the same except it takes as
argument a va_list parameter, so it can be called within a
variadic function.
Bwrite outputs nbytes of data starting at addr to bp. If
this causes a write to occur and there is an error, a nega-
tive value is returned. Otherwise, the number of bytes
written is returned.
Bflush causes any buffered output associated with bp to be
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BIO(2) BIO(2)
written. The return is as for Bputc. Bflush is called on
exit for every buffer still open for writing.
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.
SOURCE
/sys/src/libbio
SEE ALSO
open(2), print(2), exits(2), utf(6),
DIAGNOSTICS
Bio routines that return integers yield Beof if bp is not
the descriptor of an open file. Bopen returns zero if the
file cannot be opened in the given mode. All routines set
errstr on error.
BUGS
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. Blinelen will tell how many
characters are available in these cases. In the case of a
true end-of-file, Blinelen will return zero. At the cost of
allocating a buffer, Brdstr sidesteps these issues.
Only the low byte of Brdstr's delim is examined, so delim
cannot be an arbitrary rune.
The data returned by Brdline may be overwritten by calls to
any other bio routine on the same bp.
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