1 #include "stdio_impl.h" 2 3 /* Scan helper "stdio" functions for use by scanf-family and strto*-family 4 * functions. These accept either a valid stdio FILE, or a minimal pseudo 5 * FILE whose buffer pointers point into a null-terminated string. In the 6 * latter case, the sh_fromstring macro should be used to setup the FILE; 7 * the rest of the structure can be left uninitialized. 8 * 9 * To begin using these functions, shlim must first be called on the FILE 10 * to set a field width limit, or 0 for no limit. For string pseudo-FILEs, 11 * a nonzero limit is not valid and produces undefined behavior. After that, 12 * shgetc, shunget, and shcnt are valid as long as no other stdio functions 13 * are called on the stream. 14 * 15 * When used with a real FILE object, shunget has only one byte of pushback 16 * available. Further shunget (up to a limit of the stdio UNGET buffer size) 17 * will adjust the position but will not restore the data to be read again. 18 * This functionality is needed for the wcsto*-family functions, where it's 19 * okay because the FILE will be discarded immediately anyway. When used 20 * with string pseudo-FILEs, shunget has unlimited pushback, back to the 21 * beginning of the string. */ 22 23 hidden void __shlim(FILE *, off_t); 24 hidden int __shgetc(FILE *); 25 26 #define shcnt(f) ((f)->shcnt + ((f)->rpos - (f)->buf)) 27 #define shlim(f, lim) __shlim((f), (lim)) 28 #define shgetc(f) (((f)->rpos != (f)->shend) ? *(f)->rpos++ : __shgetc(f)) 29 #define shunget(f) ((f)->shlim>=0 ? (void)(f)->rpos-- : (void)0) 30 31 #define sh_fromstring(f, s) \ 32 ((f)->buf = (f)->rpos = (void *)(s), (f)->rend = (void*)-1) 33