These routines implement fast buffered I/O. I/O on different 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 initializes
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:
Arguments of types pointer to Biobuf and pointer to Biobufhdr
can be used interchangeably in the following routines.
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
the length (including 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 (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,
excluding the NUL.
Bgetc returns the next byte (sic) 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 formatted
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 negative value
is returned. Otherwise, the number of bytes written is returned.
Bflush causes any buffered output associated with bp to be 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
typedef struct Biobuf Biobuf;|