diff options
Diffstat (limited to 'src/internal')
| -rw-r--r-- | src/internal/shgetc.c | 21 | ||||
| -rw-r--r-- | src/internal/shgetc.h | 27 |
2 files changed, 40 insertions, 8 deletions
diff --git a/src/internal/shgetc.c b/src/internal/shgetc.c index e878b00a..ebd5fae7 100644 --- a/src/internal/shgetc.c +++ b/src/internal/shgetc.c @@ -1,10 +1,16 @@ #include "shgetc.h" +/* The shcnt field stores the number of bytes read so far, offset by + * the value of buf-rpos at the last function call (__shlim or __shgetc), + * so that between calls the inline shcnt macro can add rpos-buf to get + * the actual count. */ + void __shlim(FILE *f, off_t lim) { f->shlim = lim; - f->shcnt = f->rend - f->rpos; - if (lim && f->shcnt > lim) + f->shcnt = f->buf - f->rpos; + /* If lim is nonzero, rend must be a valid pointer. */ + if (lim && f->rend - f->rpos > lim) f->shend = f->rpos + lim; else f->shend = f->rend; @@ -13,15 +19,18 @@ void __shlim(FILE *f, off_t lim) int __shgetc(FILE *f) { int c; - if (f->shlim && f->shcnt >= f->shlim || (c=__uflow(f)) < 0) { + off_t cnt = shcnt(f); + if (f->shlim && cnt >= f->shlim || (c=__uflow(f)) < 0) { + f->shcnt = f->buf - f->rpos + cnt; f->shend = 0; return EOF; } - if (f->shlim && f->rend - f->rpos > f->shlim - f->shcnt - 1) - f->shend = f->rpos + (f->shlim - f->shcnt - 1); + cnt++; + if (f->shlim && f->rend - f->rpos > f->shlim - cnt) + f->shend = f->rpos + (f->shlim - cnt); else f->shend = f->rend; - if (f->rend) f->shcnt += f->rend - f->rpos + 1; + f->shcnt = f->buf - f->rpos + cnt; if (f->rpos[-1] != c) f->rpos[-1] = c; return c; } diff --git a/src/internal/shgetc.h b/src/internal/shgetc.h index 210f6468..1c30f75f 100644 --- a/src/internal/shgetc.h +++ b/src/internal/shgetc.h @@ -1,9 +1,32 @@ #include "stdio_impl.h" +/* Scan helper "stdio" functions for use by scanf-family and strto*-family + * functions. These accept either a valid stdio FILE, or a minimal pseudo + * FILE whose buffer pointers point into a null-terminated string. In the + * latter case, the sh_fromstring macro should be used to setup the FILE; + * the rest of the structure can be left uninitialized. + * + * To begin using these functions, shlim must first be called on the FILE + * to set a field width limit, or 0 for no limit. For string pseudo-FILEs, + * a nonzero limit is not valid and produces undefined behavior. After that, + * shgetc, shunget, and shcnt are valid as long as no other stdio functions + * are called on the stream. + * + * When used with a real FILE object, shunget has only one byte of pushback + * available. Further shunget (up to a limit of the stdio UNGET buffer size) + * will adjust the position but will not restore the data to be read again. + * This functionality is needed for the wcsto*-family functions, where it's + * okay because the FILE will be discarded immediately anyway. When used + * with string pseudo-FILEs, shunget has unlimited pushback, back to the + * beginning of the string. */ + hidden void __shlim(FILE *, off_t); hidden int __shgetc(FILE *); -#define shcnt(f) ((f)->shcnt + ((f)->rpos - (f)->rend)) +#define shcnt(f) ((f)->shcnt + ((f)->rpos - (f)->buf)) #define shlim(f, lim) __shlim((f), (lim)) -#define shgetc(f) (((f)->rpos < (f)->shend) ? *(f)->rpos++ : __shgetc(f)) +#define shgetc(f) (((f)->rpos != (f)->shend) ? *(f)->rpos++ : __shgetc(f)) #define shunget(f) ((f)->shend ? (void)(f)->rpos-- : (void)0) + +#define sh_fromstring(f, s) \ + ((f)->buf = (f)->rpos = (void *)(s), (f)->rend = (void*)-1) |