harvey/sys/man/9/readnum

.TH READNUM 9
.SH NAME
readnum, readstr \- return values from read from device
.SH SYNOPSIS
.ta \w'\fLchar* 'u
.B
int readstr(ulong off, char *buf, ulong n, char *str)
.PP
.B
int readnum(ulong off, char *buf, ulong n, ulong val, int size)
.SH DESCRIPTION
.I Readstr
and
.I readnum
simplify the return of strings and numbers from device
.I read
routines,
because they deal with any buffering and boundary cases.
Several parameters to the read call are often handed on directly
to these functions:
the file offset, as
.IR off ;
the address of the user's buffer, as
.IR buf ;
and the number of bytes requested, as
.IR n .
Both functions return the number of bytes they have stored in
.IR buf ,
and which can often be returned directly from the device read routine.
.PP
.I Readstr
satisfies a read by copying data into
.I buf
from the NUL-terminated string in
.IR str .
The data transferred is selected and limited by
.IR off ,
.I n
and the length of
.IR str .
.PP
.I Readnum
converts the unsigned integer
.I val
to a decimal representation in
.IR buf .
The value is right-justified in a field of
.IR size "-1"
places and is followed by a blank.
.I Size
can be the global constant
.L NUMSIZE
for 32-bit integers;
the largest
.I size
allowed is 64 bytes. 
.SH SOURCE
.B /sys/src/9/port/devcons.c