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/*
* tools/testing/selftests/kvm/lib/io.c
*
* Copyright (C) 2018, Google LLC.
*
* This work is licensed under the terms of the GNU GPL, version 2.
*/
#include "test_util.h"
/* Test Write
*
* A wrapper for write(2), that automatically handles the following
* special conditions:
*
* + Interrupted system call (EINTR)
* + Write of less than requested amount
* + Non-block return (EAGAIN)
*
* For each of the above, an additional write is performed to automatically
* continue writing the requested data.
* There are also many cases where write(2) can return an unexpected
* error (e.g. EIO). Such errors cause a TEST_ASSERT failure.
*
* Note, for function signature compatibility with write(2), this function
* returns the number of bytes written, but that value will always be equal
* to the number of requested bytes. All other conditions in this and
* future enhancements to this function either automatically issue another
* write(2) or cause a TEST_ASSERT failure.
*
* Args:
* fd - Opened file descriptor to file to be written.
* count - Number of bytes to write.
*
* Output:
* buf - Starting address of data to be written.
*
* Return:
* On success, number of bytes written.
* On failure, a TEST_ASSERT failure is caused.
*/
ssize_t test_write(int fd, const void *buf, size_t count)
{
ssize_t rc;
ssize_t num_written = 0;
size_t num_left = count;
const char *ptr = buf;
/* Note: Count of zero is allowed (see "RETURN VALUE" portion of
* write(2) manpage for details.
*/
TEST_ASSERT(count >= 0, "Unexpected count, count: %li", count);
do {
rc = write(fd, ptr, num_left);
switch (rc) {
case -1:
TEST_ASSERT(errno == EAGAIN || errno == EINTR,
"Unexpected write failure,\n"
" rc: %zi errno: %i", rc, errno);
continue;
case 0:
TEST_ASSERT(false, "Unexpected EOF,\n"
" rc: %zi num_written: %zi num_left: %zu",
rc, num_written, num_left);
break;
default:
TEST_ASSERT(rc >= 0, "Unexpected ret from write,\n"
" rc: %zi errno: %i", rc, errno);
num_written += rc;
num_left -= rc;
ptr += rc;
break;
}
} while (num_written < count);
return num_written;
}
/* Test Read
*
* A wrapper for read(2), that automatically handles the following
* special conditions:
*
* + Interrupted system call (EINTR)
* + Read of less than requested amount
* + Non-block return (EAGAIN)
*
* For each of the above, an additional read is performed to automatically
* continue reading the requested data.
* There are also many cases where read(2) can return an unexpected
* error (e.g. EIO). Such errors cause a TEST_ASSERT failure. Note,
* it is expected that the file opened by fd at the current file position
* contains at least the number of requested bytes to be read. A TEST_ASSERT
* failure is produced if an End-Of-File condition occurs, before all the
* data is read. It is the callers responsibility to assure that sufficient
* data exists.
*
* Note, for function signature compatibility with read(2), this function
* returns the number of bytes read, but that value will always be equal
* to the number of requested bytes. All other conditions in this and
* future enhancements to this function either automatically issue another
* read(2) or cause a TEST_ASSERT failure.
*
* Args:
* fd - Opened file descriptor to file to be read.
* count - Number of bytes to read.
*
* Output:
* buf - Starting address of where to write the bytes read.
*
* Return:
* On success, number of bytes read.
* On failure, a TEST_ASSERT failure is caused.
*/
ssize_t test_read(int fd, void *buf, size_t count)
{
ssize_t rc;
ssize_t num_read = 0;
size_t num_left = count;
char *ptr = buf;
/* Note: Count of zero is allowed (see "If count is zero" portion of
* read(2) manpage for details.
*/
TEST_ASSERT(count >= 0, "Unexpected count, count: %li", count);
do {
rc = read(fd, ptr, num_left);
switch (rc) {
case -1:
TEST_ASSERT(errno == EAGAIN || errno == EINTR,
"Unexpected read failure,\n"
" rc: %zi errno: %i", rc, errno);
break;
case 0:
TEST_ASSERT(false, "Unexpected EOF,\n"
" rc: %zi num_read: %zi num_left: %zu",
rc, num_read, num_left);
break;
default:
TEST_ASSERT(rc > 0, "Unexpected ret from read,\n"
" rc: %zi errno: %i", rc, errno);
num_read += rc;
num_left -= rc;
ptr += rc;
break;
}
} while (num_read < count);
return num_read;
}
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