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sbuf_bcat.9freebsd

BSD mandoc

NAME

sbuf sbuf_new sbuf_new_auto sbuf_clear sbuf_setpos sbuf_bcat sbuf_bcopyin sbuf_bcpy sbuf_cat sbuf_copyin sbuf_cpy sbuf_printf sbuf_vprintf sbuf_putc sbuf_trim sbuf_overflowed sbuf_finish sbuf_data sbuf_len sbuf_done sbuf_delete - safe string formatting

SYNOPSIS

In sys/types.h In sys/sbuf.h Ft struct sbuf * Fn sbuf_new struct sbuf *s char *buf int length int flags Ft struct sbuf * Fn sbuf_new_auto Ft void Fn sbuf_clear struct sbuf *s Ft int Fn sbuf_setpos struct sbuf *s int pos Ft int Fn sbuf_bcat struct sbuf *s const void *buf size_t len Ft int Fn sbuf_bcopyin struct sbuf *s const void *uaddr size_t len Ft int Fn sbuf_bcpy struct sbuf *s const void *buf size_t len Ft int Fn sbuf_cat struct sbuf *s const char *str Ft int Fn sbuf_copyin struct sbuf *s const void *uaddr size_t len Ft int Fn sbuf_cpy struct sbuf *s const char *str Ft int Fn sbuf_printf struct sbuf *s const char *fmt ... Ft int Fn sbuf_vprintf struct sbuf *s const char *fmt va_list ap Ft int Fn sbuf_putc struct sbuf *s int c Ft int Fn sbuf_trim struct sbuf *s Ft int Fn sbuf_overflowed struct sbuf *s Ft void Fn sbuf_finish struct sbuf *s Ft char * Fn sbuf_data struct sbuf *s Ft int Fn sbuf_len struct sbuf *s Ft int Fn sbuf_done struct sbuf *s Ft void Fn sbuf_delete struct sbuf *s

DESCRIPTION

The family of functions allows one to safely allocate, construct and release bounded null-terminated strings in kernel space. Instead of arrays of characters, these functions operate on structures called Fa sbufs , defined in In sys/sbuf.h .

The Fn sbuf_new function initializes the Fa sbuf pointed to by its first argument. If that pointer is NULL Fn sbuf_new allocates a Vt struct sbuf using malloc(9). The Fa buf argument is a pointer to a buffer in which to store the actual string; if it is NULL Fn sbuf_new will allocate one using malloc(9). The Fa length is the initial size of the storage buffer. The fourth argument, Fa flags , may be comprised of the following flags:

SBUF_FIXEDLEN

The storage buffer is fixed at its initial size. Attempting to extend the sbuf beyond this size results in an overflow condition.

SBUF_AUTOEXTEND

This indicates that the storage buffer may be extended as necessary, so long as resources allow, to hold additional data.

Note that if Fa buf is not NULL it must point to an array of at least Fa length characters. The result of accessing that array directly while it is in use by the sbuf is undefined.

The Fn sbuf_new_auto function is a shortcut for creating a completely dynamic . It is the equivalent of calling Fn sbuf_new with values NULL NULL 0 and SBUF_AUTOEXTEND

The Fn sbuf_delete function clears the Fa sbuf and frees any memory allocated for it. There must be a call to Fn sbuf_delete for every call to Fn sbuf_new . Any attempt to access the sbuf after it has been deleted will fail.

The Fn sbuf_clear function invalidates the contents of the Fa sbuf and resets its position to zero.

The Fn sbuf_setpos function sets the Fa sbuf Ns 's end position to Fa pos , which is a value between zero and one less than the size of the storage buffer. This effectively truncates the sbuf at the new position.

The Fn sbuf_bcat function appends the first Fa len bytes from the buffer Fa buf to the Fa sbuf .

The Fn sbuf_bcopyin function copies Fa len bytes from the specified userland address into the Fa sbuf .

The Fn sbuf_bcpy function replaces the contents of the Fa sbuf with the first Fa len bytes from the buffer Fa buf .

The Fn sbuf_cat function appends the NUL-terminated string Fa str to the Fa sbuf at the current position.

The Fn sbuf_copyin function copies a NUL-terminated string from the specified userland address into the Fa sbuf . If the Fa len argument is non-zero, no more than Fa len characters (not counting the terminating NUL) are copied; otherwise the entire string, or as much of it as can fit in the Fa sbuf , is copied.

The Fn sbuf_cpy function replaces the contents of the Fa sbuf with those of the NUL-terminated string Fa str . This is equivalent to calling Fn sbuf_cat with a fresh Fa sbuf or one which position has been reset to zero with Fn sbuf_clear or Fn sbuf_setpos .

The Fn sbuf_printf function formats its arguments according to the format string pointed to by Fa fmt and appends the resulting string to the Fa sbuf at the current position.

The Fn sbuf_vprintf function behaves the same as Fn sbuf_printf except that the arguments are obtained from the variable-length argument list Fa ap .

The Fn sbuf_putc function appends the character Fa c to the Fa sbuf at the current position.

The Fn sbuf_trim function removes trailing whitespace from the Fa sbuf .

The Fn sbuf_overflowed function returns a non-zero value if the Fa sbuf overflowed.

The Fn sbuf_finish function null-terminates the Fa sbuf and marks it as finished, which means that it may no longer be modified using Fn sbuf_setpos , Fn sbuf_cat , Fn sbuf_cpy , Fn sbuf_printf or Fn sbuf_putc .

The Fn sbuf_data and Fn sbuf_len functions return the actual string and its length, respectively; Fn sbuf_data only works on a finished Fa sbuf . Fn sbuf_done returns non-zero if the sbuf is finished.

NOTES

If an operation caused an Fa sbuf to overflow, most subsequent operations on it will fail until the Fa sbuf is finished using Fn sbuf_finish or reset using Fn sbuf_clear , or its position is reset to a value between 0 and one less than the size of its storage buffer using Fn sbuf_setpos , or it is reinitialized to a sufficiently short string using Fn sbuf_cpy .

RETURN VALUES

The Fn sbuf_new function returns NULL if it failed to allocate a storage buffer, and a pointer to the new Fa sbuf otherwise.

The Fn sbuf_setpos function returns -1 if Fa pos was invalid, and zero otherwise.

The Fn sbuf_cat , Fn sbuf_cpy , Fn sbuf_printf , Fn sbuf_putc , and Fn sbuf_trim functions all return -1 if the buffer overflowed, and zero otherwise.

The Fn sbuf_overflowed function returns a non-zero value if the buffer overflowed, and zero otherwise.

The Fn sbuf_data and Fn sbuf_len functions return NULL and -1, respectively, if the buffer overflowed.

The Fn sbuf_copyin function returns -1 if copying string from userland failed, and number of bytes copied otherwise.

SEE ALSO

printf(3), strcat(3), strcpy(3), copyin(9), copyinstr(9), printf(9)

HISTORY

The family of functions first appeared in Fx 4.4 .

AUTHORS

An -nosplit The family of functions was designed by An Poul-Henning Kamp Aq phk@FreeBSD.org and implemented by An Dag-Erling Smørgrav Aq des@FreeBSD.org . Additional improvements were suggested by An Justin T. Gibbs Aq gibbs@FreeBSD.org . Auto-extend support added by An Kelly Yancey Aq kbyanc@FreeBSD.org .

This manual page was written by An Dag-Erling Smørgrav Aq des@FreeBSD.org .