libstand(3)

NAME

libstand - support library for standalone executables

SYNOPSIS

#include <stand.h>

DESCRIPTION

The libstand library provides a set of supporting functions

for standalone applications, mimicking where possible the standard

BSD programming environment. The following sections group these func

tions by kind.
Unless specifically described here, see the corresponding

section 3 manpages for the given functions.

STRING FUNCTIONS

String functions are available as documented in string(3)

and bstring(3).

MEMORY ALLOCATION

void * malloc(size_t size)

Allocate size bytes of memory from the heap us

ing a best-fit
algorithm.

void free(void *ptr)

Free the allocated object at ptr.

void setheap(void *start, void *limit)

Initialise the heap. This function must be

called before
calling alloc() for the first time. The region

between start
and limit will be used for the heap; attempting

to allocate
beyond this will result in a panic.

char * sbrk(int junk)

Provides the behaviour of sbrk(0), i.e., returns

the highest
point that the heap has reached. This value can

be used during testing to determine the actual heap usage.

The junk
argument is ignored.

ENVIRONMENT

A set of functions are provided for manipulating a flat

variable space
similar to the traditional shell-supported environment. Ma

jor enhancements are support for set/unset hook functions.

char * getenv(const char *name)

int setenv(const char *name, char *value, int overwrite)

int putenv(const char *string)

int unsetenv(const char *name)

These functions behave similarly to their stan

dard library
counterparts.

struct env_var * env_getenv(const char *name)

Looks up a variable in the environment and re

turns its entire
data structure.

int env_setenv(const char *name, int flags, char *value,

ev_sethook_t

sethook, ev_unsethook_t unsethook)

Creates a new or sets an existing environment

variable called
name. If creating a new variable, the sethook

and unsethook
arguments may be specified.

The set hook is invoked whenever an attempt is

made to set
the variable, unless the EV_NOHOOK flag is set.

Typically a
set hook will validate the value argument, and

then call
env_setenv() again with EV_NOHOOK set to actual

ly save the
value. The predefined function env_noset() may

be specified
to refuse all attempts to set a variable.

The unset hook is invoked when an attempt is

made to unset a
variable. If it returns zero, the variable will

be unset.
The predefined function env_nounset may be used

to prevent a
variable being unset.

STANDARD LIBRARY SUPPORT

int getopt(int argc, char * const *argv, const char

*optstring)

long strtol(const char *nptr, char **endptr, int base)

void srandom(unsigned long seed)

unsigned long random(void)

char * strerror(int error)

Returns error messages for the subset of errno

values supported by libstand.

assert(expression)

Requires

int setjmp(jmp_buf env)

void longjmp(jmp_buf env, int val)

Defined as _setjmp() and _longjmp() respectively

as there is
no signal state to manipulate. Requires

CHARACTER I/O

void gets(char *buf)

Read characters from the console into buf. All

of the standard cautions apply to this function.

void ngets(char *buf, size_t size)

Read at most size - 1 characters from the con

sole into buf.
If size is less than 1, the function's behaviour

is as for
gets().

int fgetstr(char *buf, int size, int fd)

Read a line of at most size characters into buf.

Line terminating characters are stripped, and the buffer

is always NUL
terminated. Returns the number of characters in

buf if successful, or -1 if a read error occurs.

int printf(const char *fmt, ...)

void vprintf(const char *fmt, va_list ap)

int sprintf(char *buf, const char *fmt, ...)

void vsprintf(char *buf, const char *fmt, va_list ap)

The *printf functions implement a subset of the

standard
printf() family functionality and some exten

sions. The following standard conversions are supported:

c,d,n,o,p,s,u,x.
The following modifiers are supported:

+,-,#,*,0,field
width,precision,l.

The b conversion is provided to decode error

registers. Its
usage is:

printf( "reg=%b0, regval, "<base><arg>*"

);

where <base> is the output expressed as a con

trol character,
e.g. 10 gives octal, 20 gives hex. Each <arg>

is a
sequence of characters, the first of which gives

the bit number to be inspected (origin 1) and the next

characters (up to
a character less than 32) give the text to be

displayed if
the bit is set. Thus

printf( "reg=%b0, 3, "102BITTWO1BITONE0 );

would give the output

reg=3<BITTWO,BITONE>

The D conversion provides a hexdump facility,

e.g.

printf( "%6D", ptr, ":" ); gives

"XX:XX:XX:XX:XX:XX"

printf( "%*D", len, ptr, " " ); gives "XX

XX XX ..."

CHARACTER TESTS AND CONVERSIONS

int isupper(int c)

int islower(int c)

int isspace(int c)

int isdigit(int c)

int isxdigit(int c)

int isascii(int c)

int isalpha(int c)

int toupper(int c)

int tolower(int c)

FILE I/O

int open(const char *path, int flags)

Similar to the behaviour as specified in

open(2), except that
file creation is not supported, so the mode pa

rameter is not
required. The flags argument may be one of

O_RDONLY,
O_WRONLY and O_RDWR (although no file systems

currently support writing).

int close(int fd)

void closeall(void)

Close all open files.

ssize_t read(int fd, void *buf, size_t len)

ssize_t write(int fd, void *buf, size_t len)

(No file systems currently support writing.)

off_t lseek(int fd, off_t offset, int whence)

Files being automatically uncompressed during

reading cannot
seek backwards from the current point.

int stat(const char *path, struct stat *sb)

int fstat(int fd, struct stat *sb)

The stat() and fstat() functions only fill out

the following
fields in the sb structure:
st_mode,st_nlink,st_uid,st_gid,st_size. The

tftp file system
cannot provide meaningful values for this call,

and the
cd9660 file system always reports files having

uid/gid of
zero.

PAGER

The libstand library supplies a simple internal pager to

ease reading the
output of large commands.

void pager_open()

Initialises the pager and tells it that the next

line output
will be the top of the display. The environment

variable
LINES is consulted to determine the number of

lines to be
displayed before pausing.

void pager_close(void)

Closes the pager.

int pager_output(char *lines)

Sends the lines in the NUL-terminated buffer at

lines to the
pager. Newline characters are counted in order

to determine
the number of lines being output (wrapped lines

are not
accounted for). The pager_output() function

will return zero
when all of the lines have been output, or

nonzero if the
display was paused and the user elected to quit.

int pager_file(char *fname)

Attempts to open and display the file fname.

Returns -1 on
error, 0 at EOF, or 1 if the user elects to quit

while reading.

MISC

void twiddle(void)

Successive calls emit the characters in the se

quence |,/,-, followed by a backspace in order to

provide reassurance to
the user.

REQUIRED LOW-LEVEL SUPPORT

The following resources are consumed by libstand - stack,

heap, console
and devices.

The stack must be established before libstand functions can

be invoked.
Stack requirements vary depending on the functions and file

systems used
by the consumer and the support layer functions detailed be

low.

The heap must be established before calling alloc() or

open() by calling
setheap(). Heap usage will vary depending on the number of

simultaneously open files, as well as client behaviour. Automatic

decompression
will allocate more than 64K of data per open file.

Console access is performed via the getchar(), putchar() and

ischar()
functions detailed below.

Device access is initiated via devopen() and is performed

through the
dv_strategy(), dv_ioctl() and dv_close() functions in the

device switch
structure that devopen() returns.

The consumer must provide the following support functions:

int getchar(void)

Return a character from the console, used by

gets(), ngets()
and pager functions.

int ischar(void)

Returns nonzero if a character is waiting from

the console.

void putchar(int)

Write a character to the console, used by

gets(), ngets(),
*printf(), panic() and twiddle() and thus by

many other functions for debugging and informational output.

int devopen(struct open_file *of, const char *name, char

**file)

Open the appropriate device for the file named

in name,
returning in file a pointer to the remaining

body of name
which does not refer to the device. The f_dev

field in of
will be set to point to the devsw structure for

the opened
device if successful. Device identifiers must

always precede
the path component, but may otherwise be arbi

trarily formatted. Used by open() and thus for all device-re

lated I/O.

int devclose(struct open_file *of)

Close the device allocated for of. The device

driver itself
will already have been called for the close;

this call should
clean up any allocation made by devopen only.

void panic(const char *msg, ...)

Signal a fatal and unrecoverable error condi

tion. The msg
... arguments are as for printf().

INTERNAL FILE SYSTEMS

Internal file systems are enabled by the consumer exporting

the array
struct fs_ops *file_system[], which should be initialised

with pointers
to struct fs_ops structures. The following file system han

dlers are supplied by libstand, the consumer may supply other file sys

tems of their
own:

ufs_fsops The BSD UFS.

ext2fs_fsops Linux ext2fs file system.

tftp_fsops File access via TFTP.

nfs_fsops File access via NFS.

cd9660_fsops ISO 9660 (CD-ROM) file system.

gzipfs_fsops Stacked file system supporting gzipped

files. When

trying the gzipfs file system, libstand

appends .gz to
the end of the filename, and then tries to

locate the
file using the other file systems. Place

ment of this
file system in the file_system[] array de

termines
whether gzipped files will be opened in

preference to
non-gzipped files. It is only possible to

seek a
gzipped file forwards, and stat() and

fstat() on
gzipped files will report an invalid

length.

bzipfs_fsops The same as gzipfs_fsops, but for

bzip2(1)-compressed

files.

The array of struct fs_ops pointers should be terminated

with a NULL.

DEVICES

Devices are exported by the supporting code via the array

struct devsw
*devsw[] which is a NULL terminated array of pointers to de

vice switch
structures.

HISTORY

The libstand library contains contributions from many

sources, including:
+o libsa from NetBSD
+o libc and libkern from FreeBSD 3.0.
+o zalloc from Matthew Dillon <dillon@backplane.com>

The reorganisation and port to FreeBSD 3.0, the environment

functions and
this manpage were written by Mike Smith <msmith@FreeB

SD.org>.

BUGS

The lack of detailed memory usage data is unhelpful.

BSD August 6, 2004

BSD