string.c

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#ifndef _STRING_C_ /* -*- linux-c -*- */
#define _STRING_C_

#include <linux/config.h>

/** @file string.c
 * @brief Implements String type.
 */
/** @addtogroup string String Functions
 *
 * One of the biggest restrictions the library has is that it cannot allocate things like strings off the stack.
 * It is also not a good idea to dynamically allocate space for strings with kmalloc().  That leaves us with 
 * statically allocated space for strings. This is what is implemented in the String module.  Strings use
 * preallocated per-cpu buffers and are safe to use (unlike C strings).
 * @{
 */

/** Maximum string size allowed in Strings */
#ifndef STP_STRING_SIZE
#define STP_STRING_SIZE 2048
#endif

struct string {
        short len;
        short global;
        char buf[STP_STRING_SIZE];
};

static struct string _stp_string[STP_NUM_STRINGS][NR_CPUS];

typedef struct string *String;

/** Initialize a String for our use.
 * This grabs one of the global Strings for our use.
 *
 * @param num Number of the preallocated String to use. 
 * #STP_NUM_STRINGS are statically allocated for our use. The
 * translator (or author) should be sure to grab a free one.
 * @todo Global (and static) Strings not implemented yet. 
 */

String _stp_string_init (int num)
{
        int global = 0;
        String str;

        if (num  < 0) {
                num = -num;
                global = 1;
        }
        
        if (num >= STP_NUM_STRINGS) {
                _stp_log ("_stp_string_init internal error: requested string exceeded allocated number");
                return NULL;
        }

        if (global)
                str = &_stp_string[num][0];
        else
                str = &_stp_string[num][smp_processor_id()];

        str->global = global;
        str->len = 0;
        return str;
}


/** Sprintf into a String.
 * Like printf, except output goes into a String.
 * Safe because overflowing the buffer is not allowed.
 * Size is limited by length of String, #STP_STRING_SIZE.
 *
 * @param str String
 * @param fmt A printf-style format string followed by a 
 * variable number of args.
 */
void _stp_sprintf (String str, const char *fmt, ...)
{
        int num;
        va_list args;
        va_start(args, fmt);
        num = vscnprintf(str->buf + str->len, STP_STRING_SIZE - str->len - 1, fmt, args);
        va_end(args);
        if (num > 0)
                str->len += num;
}

/** Vsprintf into a String
 * Use this if your function already has a va_list.
 * You probably want _stp_sprintf().
 */
void _stp_vsprintf (String str, const char *fmt, va_list args)
{
        int num;
        num = vscnprintf(str->buf + str->len, STP_STRING_SIZE - str->len - 1, fmt, args);
        if (num > 0)
                str->len += num;
}

/** ConCATenate (append) a C string to a String.
 * Like strcat().
 * @param str1 String
 * @param str2 C string (char *)
 * @sa _stp_string_cat
 */
void _stp_string_cat_cstr (String str1, const char *str2)
{
        int num = strlen (str2);
        if (num > STP_STRING_SIZE - str1->len - 1)
                num = STP_STRING_SIZE - str1->len - 1;
        strncpy (str1->buf + str1->len, str2, num+1);
        str1->len += num;
}

/** ConCATenate (append) a String to a String.
 * Like strcat().
 * @param str1 String
 * @param str2 String
 * @sa _stp_string_cat
 */
void _stp_string_cat_string (String str1, String str2)
{
        int num = str2->len;
        if (num > STP_STRING_SIZE - str1->len - 1)
                num = STP_STRING_SIZE - str1->len - 1;
        strncpy (str1->buf + str1->len, str2->buf, num);
        str1->len += num;
}

/** Get a pointer to String's buffer
 * For rare cases when a C string is needed and you have a String.
 * One example is when you want to print a String with _stp_printf().
 * @param str String
 * @returns A C string (char *)
 * @note Readonly. Don't write to this pointer or it will mess up
 * the internal String state and probably mess up your output or crash something.
 */
char * _stp_string_ptr (String str)
{
        return str->buf;
}


/** ConCATenate (append) a String or C string to a String.
 * This macro selects the proper function to call.
 * @param str1 A String
 * @param str2 A String or C string (char *)
 * @sa _stp_string_cat_cstr _stp_string_cat_string
 */
#define _stp_string_cat(str1, str2)                                     \
  ({                                                            \
          if (__builtin_types_compatible_p (typeof (str2), char[])) {   \
                  char *x = (char *)str2;                               \
                  _str_string_cat_cstr(str1,x);                         \
          } else {                                                      \
                  String x = (String)str2;                              \
                  _str_string_cat_string(str1,x);                       \
          }                                                             \
  })

/** @} */
#endif /* _STRING_C_ */