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/*
** BASIC-like string operations
**
** public domain by Bob Stout
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>
#include <assert.h>
static int stralloc_ptr;
static char *strings[8];
static int str_tag[8];
/*
** stralloc() is the key function in this package, maintaining a pool of
** reusable strings.
*/
char *stralloc(size_t length)
{
register int i;
i = stralloc_ptr++;
if ((!strings[i]) || (length > strlen(strings[i])))
{
assert(strings[i] = (char *)realloc(strings[i], length));
str_tag[i] = -1;
}
else str_tag[i] = 0;
stralloc_ptr &= 7;
return (strings[i]);
/* Maintains 8 strings in a circular buffer */
}
/*
** free the string pool.
*/
void str_free(char *string)
{
register int i;
for (i = 0; i < 8; ++i)
{
if (strings[i] == string)
{
if (str_tag[i])
free(strings[i]);
return;
}
}
}
/*
** return the leftmost N characters from a string
*/
char *left(char *string, size_t N)
{
char *buf;
size_t strlength = strlen(string);
if (N > strlength)
N = strlength;
buf = stralloc(N + 1);
memcpy(buf, string, N);
buf[N] = '\0';
return buf;
}
/*
** return the rightmost N characters from a string
*/
char *right(char *string, size_t N)
{
char *buf;
size_t strlength = strlen(string);
if (N > strlength)
N = strlength;
buf = stralloc(N + 1);
strcpy(buf, &string[strlength-N]);
return buf;
}
/*
** return a substring, N characters long beginning at position M
*/
char *mid(char *string, size_t M, size_t N)
{
char *buf;
size_t strlength = strlen(string);
if (M > strlength)
return NULL;
if (N > (strlength - M))
N = strlength - M;
buf = stralloc(N + 1);
memcpy(buf, &string[M-1], N);
buf[N] = '\0';
return buf;
}
/*
** string concatenation function, equivalent to A$=B$+C$+...
*/
char *string_add(char *string, ...)
{
va_list arg_ptr;
char *temp1, *temp2, *buf;
va_start(arg_ptr, string);
temp1 = string;
do
{
if(NULL == (temp2 = va_arg(arg_ptr, char *)))
break;
buf = stralloc(strlen(temp1) + strlen(temp2) + 1);
temp1 = strcat(strcpy(buf, temp1), temp2);
} while (NULL != temp2);
return temp1;
}
#ifdef TEST
/*
** Demo main()
*/
void main(void)
{
char *x = "European", *y = "Hardware", *z = "Skaters";
z = string_add(left(x, 2), right(y, 2), mid(z, 2, 2), "!", NULL);
puts(z);
}
#endif /* TEST */
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