Add asprintf.c

asprintf.c

+#ifndef HAVE_ASPRINTF
+#include <stdio.h>  //vsnprintf
+#include <stdlib.h> //malloc
+#include <stdarg.h> //va_start et al
+
+/* The declaration, to put into a .h file.    The __attribute___ tells the compiler to check printf-style type-compliance.
+   It's not C standard, but a lot of compilers supprt it. Just remove it if yours doesn't */
+
+int asprintf(char **str, char* fmt, ...) __attribute__ ((format (printf,2,3)));
+
+
+int asprintf(char **str, char* fmt, ...){
+    va_list argp; 
+    va_start(argp, fmt);
+    char one_char[1];
+    int len = vsnprintf(one_char, 1, fmt, argp);
+    if (len < 1){
+        fprintf(stderr, "An encoding error occurred. Setting the input pointer to NULL.\n");
+        *str = NULL;
+        return len;
+    }
+    va_end(argp);
+
+    *str = malloc(len+1);
+    if (!str) {
+        fprintf(stderr, "Couldn't allocate %i bytes.\n", len+1);
+        return -1;
+    }
+    va_start(argp, fmt);
+    vsnprintf(*str, len+1, fmt, argp);
+    va_end(argp);
+    return len;
+}
+#endif
+
+#ifdef Test_asprintf
+int main(){
+    char *s;
+    asprintf(&s, "hello, %s.", "—Reader—");
+    printf("%s\n", s);
+
+    asprintf(&s, "%c", '\0');
+    printf("blank string: [%s]\n", s);
+
+    int i = 0;
+    asprintf(&s, "%i", i++);
+    printf("Zero: %s\n", s);
+}
+#endif