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Man Pages

Manual Reference Pages  -  SBUF_DETACH (3)


sbuf_init, sbuf_free, sbuf_clear, sbuf_zero, sbuf_add, sbuf_add2, sbuf_trim, sbuf_detach, sbuf_extend, sbuf_sprintf, sbuf_vsprintf, sbuf_fetch, sbuf_fgets - smart buffers manipulation functions


Return Values
See Also


.Fd #include <strfunc.h>

Create, and destroy the buffer sbuf * sbuf_init void void sbuf_free sbuf *sb

Clean and truncate the buffer int sbuf_clear sbuf *sb

Just clean the buffer int sbuf_zero sbuf *sb

Add values to the end of the buffer ssize_t sbuf_add sbuf *sb conat char *string ssize_t sbuf_add2 sbuf *sb const void *data size_t nbytes

Trim buffer from left or right side ssize_t sbuf_trim sbuf *sb int _from_left size_t nbytes

Detach the buffer contents char * sbuf_detach sbuf *sb size_t *optLength size_t *optSize

Extend the buffer ssize_t sbuf_extend sbuf * size_t upto

Add the formatted string ssize_t sbuf_sprintf sbuf * const char *fmt ... ssize_t sbuf_vsprintf sbuf * const char *fmt va_list ap

Get a first len characters or token char * sbuf_fetch sbuf * size_t optLen char *optDelimiter size_t *optRetLen int flags

Get a line from the stream char * sbuf_fgets sbuf * FILE *stream


These routines give the user a method of manipulating smart buffers. Smart buffers are used to omit headache of checking the buffer boundaries every time you’re trying to add something.

Buffers may be used to handle any types of data. Internally, the buffer always contain the terminating NULL and thus significiantly simplifies the string handling.

Here is the sbuf structure (public):

typedef struct {
        char *buf;      /* The buffer data */
        size_t len;     /* Offset to end of real data (’ ’) */
        size_t size;    /* Allocated memory */
        size_t off;     /* Offset to start of real data */
} sbuf;

The following macros are available for your convenience
#define sbuf2ptr(sb)    ((sb)->buf + (sb)->off)
#define sbuf_len(sb)    ((sb)->len - (sb)->off) /* Meaningful length */

To create a buffer, you must invoke sbuf_init first. After all the necessary operations, the sbuf * structure must be disposed with sbuf_free.

After the buffer is created, you might want to add a data to the buffer. It can be done using sbuf_add sbuf *sb const char *string and sbuf_add2 sbuf *sb const void *data size_t nbytes functions. The second function does not rely on ASCIIZ idea and places the nbytes of the data into the smart buffer. Both functions automatically extend buffer to fit all the characters provided. In case of error, the functions will return -1 and the buffer will be left intact. Upon success, sbuf_add returns with the number of written bytes and sbuf_add2 returns with the adjusted len field of the passed sbuf * structure. Otherwise a -1 is returned by both functions.

sbuf_trim trims given number of characters off the buffer from the left or right side, returning a number of bytes actually trimmed (which may be less than requested in case the actual buffer length is smaller). This is a zero-cost operation, as it just shifts pointers.

sbuf_detach used to detach the buffer from the smart buffer descriptor, and return a pointer to that detached memory. If the optional optLength or optSize are given, sbuf_detach will fill them with the actual values of the buffer length (number of meaningful bytes) and buffer size (allocated memory) appropriately. Upon detach, the smart buffer descriptor will be re-initialized to contain new, empty buffer. After detaching, the buffer descriptor ( sbuf) will be reinitialized (read "empty").

To pre-extend the buffer up to the specified size, use sbuf_extend. This function will also clear the buffer from the current position ( sb->len) to the end of the allocated memory.

sbuf_sprintf and sbuf_vsprintf functions used to add the formatted string to the end of the buffer. These functions returns the number of bytes actually writen. Buffer will be automatically extended to fit the string. In case of error, -1 will be returned and buffer will be left intact. See the manual pages on sprintf(3) and vsprintf(3) to learn more.

sbuf_fetch used to fetch the substring or token from the start of the buffer. If optLen argument is zero optDdelimiter must contain the set of delimiting characters, overwise ignored. The flags argument controls the behavior of splitting routinge most like in splitf(3) function, with exception that the buffer can’t be split by regular expression. optRetLen will contain the length of returned string.

sbuf_fgets is analogous to plain fgets(3), but has the significant feature. It adds the whole line from the given stream to the buffer and returns the pointer. The buffer is reallocated to suffice the memory requirements by this line.


All functions returning ssize_t may fail with -1 and the set errno to the appropriate value.

All functions returning pointer values ( sbuf *, char *) may fail with NULL and the set errno to the appropriate value.

By default, functions may not fail with ENOMEM unless the library memory control behavior was changed, see sf_mem(3).


Here is an example of creating and filling the smart buffer.
void main() {
        sbuf *sb;       /* Declare a buffer pointer */

        sb=sbuf_init(); /* Create and initialize buffer */

        /* Add some data */         sbuf_add(sb, "one\n");         sbuf_add2(sb, "two\n", sizeof("two\n") - 1);

        /* This will print:          * "one\ntwo\n"          */         printf("%s", sb->buf);

        /* Add the formatted string */         sbuf_sprintf(sb, "one: %d\n", 1);

        /* This will print:          * "one\ntwo\none: 1\n"          */         printf("%s", sb->buf);

        /* Destroy the buffer */         sbuf_free(sb); };

Here is an example of reading the stream line-by-line.

void readfile(FILE *stream) {
        sbuf *sb;
        char *p;

        sb = sbuf_init();

        while((p = sbuf_fgets(sb, stream) != NULL) {                 printf("Read line: %s", p);

                /* Rewind buffer */                 sbuf_zero(sb);         };

        sbuf_free(sb); };


strfunc(3), splitf(3), sprintf(3), fgets(3).


.An Lev Walkin <>
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