Rich Felker
6e2bb7acf4
previously, fgets, fputs, fread, and fwrite completely omitted locking and access to the FILE object when their arguments yielded a zero length read or write operation independent of the FILE state. this optimization was invalid; it wrongly skipped marking the stream as byte-oriented (a C conformance bug) and exposed observably missing synchronization (a POSIX conformance bug) where one of these functions could wrongly complete despite another thread provably holding the lock.
47 lines
718 B
C
47 lines
718 B
C
#include "stdio_impl.h"
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#include <string.h>
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#define MIN(a,b) ((a)<(b) ? (a) : (b))
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char *fgets(char *restrict s, int n, FILE *restrict f)
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{
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char *p = s;
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unsigned char *z;
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size_t k;
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int c;
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FLOCK(f);
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if (n--<=1) {
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f->mode |= f->mode-1;
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FUNLOCK(f);
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if (n) return 0;
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*s = 0;
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return s;
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}
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while (n) {
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z = memchr(f->rpos, '\n', f->rend - f->rpos);
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k = z ? z - f->rpos + 1 : f->rend - f->rpos;
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k = MIN(k, n);
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memcpy(p, f->rpos, k);
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f->rpos += k;
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p += k;
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n -= k;
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if (z || !n) break;
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if ((c = getc_unlocked(f)) < 0) {
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if (p==s || !feof(f)) s = 0;
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break;
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}
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n--;
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if ((*p++ = c) == '\n') break;
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}
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if (s) *p = 0;
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FUNLOCK(f);
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return s;
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}
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weak_alias(fgets, fgets_unlocked);
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