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Top Forums Programming write() issue during a low level hdd access Post 302397295 by sponnusa on Sunday 21st of February 2010 06:22:37 PM
Old 02-21-2010
Quote:
Originally Posted by Corona688
The crux is that the kernel doesn't do reads when or how you tell it to. It might bundle it with other reads, feed you data from cache, or make you wait until other reads are done. It may have to do a little or a lot of translation between the device and you. This is true for most multitasking operating systems.

Have you tried doing reads?

it may also be using linux's ancient, soon-to-be-removed obsolete and unportable raw system.
Yes. I have tried the read call. It does not return a failure for the read operation on bad sectors.

It returns success. It says it had read the amount of data I request for.

The only way I can identify the error is when I try to compare / analyse the read data with the known pattern.

Thank you.
 

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curl_easy_recv(3)						  libcurl Manual						 curl_easy_recv(3)

NAME
curl_easy_recv - receives raw data on an "easy" connection SYNOPSIS
#include <curl/easy.h> CURLcode curl_easy_recv( CURL *curl, void *buffer, size_t buflen, size_t *n); DESCRIPTION
This function receives raw data from the established connection. You may use it together with curl_easy_send(3) to implement custom proto- cols using libcurl. This functionality can be particularly useful if you use proxies and/or SSL encryption: libcurl will take care of proxy negotiation and connection set-up. buffer is a pointer to your buffer that will get the received data. buflen is the maximum amount of data you can get in that buffer. The variable n points to will receive the number of received bytes. To establish the connection, set CURLOPT_CONNECT_ONLY(3) option before calling curl_easy_perform(3) or curl_multi_perform(3). Note that curl_easy_recv(3) does not work on connections that were created without this option. The call will return CURLE_AGAIN if there is no data to read - the socket is used in non-blocking mode internally. When CURLE_AGAIN is returned, use your operating system facilities like select(2) to wait for data. The socket may be obtained using curl_easy_getinfo(3) with CURLINFO_ACTIVESOCKET(3). Wait on the socket only if curl_easy_recv(3) returns CURLE_AGAIN. The reason for this is libcurl or the SSL library may internally cache some data, therefore you should call curl_easy_recv(3) until all data is read which would include any cached data. Furthermore if you wait on the socket and it tells you there is data to read, curl_easy_recv(3) may return CURLE_AGAIN if the only data that was read was for internal SSL processing, and no other data is available. AVAILABILITY
Added in 7.18.2. RETURN VALUE
On success, returns CURLE_OK, stores the received data into buffer, and the number of bytes it actually read into *n. On failure, returns the appropriate error code. The function may return CURLE_AGAIN. In this case, use your operating system facilities to wait until data can be read, and retry. Reading exactly 0 bytes indicates a closed connection. If there's no socket available to use from the previous transfer, this function returns CURLE_UNSUPPORTED_PROTOCOL. EXAMPLE
See sendrecv.c in docs/examples directory for usage example. SEE ALSO
curl_easy_setopt(3), curl_easy_perform(3), curl_easy_getinfo(3), curl_easy_send(3) libcurl 7.54.0 December 18, 2016 curl_easy_recv(3)
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