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wget: explain clearerr more clearly

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2011-02-11 22:01:33 +01:00
parent 8766a791e8
commit f9af375668
1 changed files with 10 additions and 1 deletions
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11
networking/wget.c
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@ -466,6 +466,14 @@ static void NOINLINE retrieve_file_data(FILE *dfp, int output_fd)
polldata.fd = fileno(dfp); polldata.fd = fileno(dfp);
polldata.events = POLLIN | POLLPRI; polldata.events = POLLIN | POLLPRI;
/* Must use nonblocking I/O, otherwise fread will loop
* and *block* until it reads full buffer,
* which messes up progress bar and/or timing out.
* Because of nonblocking I/O, we need to dance
* very carefully around EAGAIN. See explanation at
* clearerr() call.
*/
ndelay_on(polldata.fd); ndelay_on(polldata.fd);
#endif #endif
progress_meter(PROGRESS_START); progress_meter(PROGRESS_START);
@ -504,7 +512,7 @@ static void NOINLINE retrieve_file_data(FILE *dfp, int output_fd)
/* Needed for "stalled" indicator */ /* Needed for "stalled" indicator */
progress_meter(PROGRESS_BUMP); progress_meter(PROGRESS_BUMP);
} }
#endif
/* fread internally uses read loop, which in our case /* fread internally uses read loop, which in our case
* is usually exited when we get EAGAIN. * is usually exited when we get EAGAIN.
* In this case, libc sets error marker on the stream. * In this case, libc sets error marker on the stream.
@ -515,6 +523,7 @@ static void NOINLINE retrieve_file_data(FILE *dfp, int output_fd)
*/ */
clearerr(dfp); clearerr(dfp);
errno = 0; errno = 0;
#endif
n = fread(G.wget_buf, 1, rdsz, dfp); n = fread(G.wget_buf, 1, rdsz, dfp);
/* man fread: /* man fread:
* If error occurs, or EOF is reached, the return value * If error occurs, or EOF is reached, the return value