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Attempt to read/write before waiting, instead of the other way around.

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This commit is contained in:
Jef Driesen 2007-10-29 09:52:28 +00:00
parent a3ae610b2e
commit 0154674573
1 changed files with 33 additions and 49 deletions
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82
serial_posix.c
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@ -420,31 +420,7 @@ posix_wait (int fd, const struct timeouts_t* timeouts, int input, unsigned int a
} }
static int int
posix_read (int fd, void* buffer, unsigned int count)
{
int rc = 0;
do {
rc = read (fd, buffer, count);
} while (rc == -1 && errno == EINTR);
return rc;
}
static int
posix_write (int fd, const void* buffer, unsigned int count)
{
int rc = 0;
do {
rc = write (fd, buffer, count);
} while (rc == -1 && errno == EINTR);
return rc;
}
int
serial_read (serial* device, void* data, unsigned int size) serial_read (serial* device, void* data, unsigned int size)
{ {
if (device == NULL) if (device == NULL)
@ -455,7 +431,22 @@ serial_read (serial* device, void* data, unsigned int size)
timeouts_init_read (device, &timeouts, size); timeouts_init_read (device, &timeouts, size);
unsigned int nbytes = 0; unsigned int nbytes = 0;
while (nbytes < size) { for (;;) {
// Attempt to read data from the file descriptor.
int n = read (device->fd, data + nbytes, size - nbytes);
if (n < 0) {
if (errno == EINTR)
continue; // Retry.
if (errno != EAGAIN) {
TRACE ("read");
return -1; // Error during read call.
}
} else {
nbytes += n;
if (!n || nbytes == size)
break; // Success or EOF.
}
// Wait until the file descriptor is ready for reading, or the timeout expires. // Wait until the file descriptor is ready for reading, or the timeout expires.
int rc = posix_wait (device->fd, &timeouts, 1, nbytes); int rc = posix_wait (device->fd, &timeouts, 1, nbytes);
if (rc < 0) { if (rc < 0) {
@ -463,18 +454,6 @@ serial_read (serial* device, void* data, unsigned int size)
return -1; // Error during select/poll call. return -1; // Error during select/poll call.
} else if (rc == 0) } else if (rc == 0)
break; // Timeout. break; // Timeout.
// Attempt to read data from the file descriptor.
int n = posix_read (device->fd, data + nbytes, size - nbytes);
if (n < 0) {
if (errno == EAGAIN) continue; // Retry.
TRACE ("posix_read");
return -1; // Error during read call.
} else if (n == 0) {
break; // EOF reached.
} else {
nbytes += n; // Success.
}
} }
return nbytes; return nbytes;
@ -492,7 +471,22 @@ serial_write (serial* device, const void* data, unsigned int size)
timeouts_init_write (device, &timeouts, size); timeouts_init_write (device, &timeouts, size);
unsigned int nbytes = 0; unsigned int nbytes = 0;
while (nbytes < size) { for (;;) {
// Attempt to write data to the file descriptor.
int n = write (device->fd, data + nbytes, size - nbytes);
if (n < 0) {
if (errno == EINTR)
continue; // Retry.
if (errno != EAGAIN) {
TRACE ("write");
return -1; // Error during write call.
}
} else {
nbytes += n;
if (nbytes == size)
break; // Success.
}
// Wait until the file descriptor is ready for writing, or the timeout expires. // Wait until the file descriptor is ready for writing, or the timeout expires.
int rc = posix_wait (device->fd, &timeouts, 0, nbytes); int rc = posix_wait (device->fd, &timeouts, 0, nbytes);
if (rc < 0) { if (rc < 0) {
@ -500,16 +494,6 @@ serial_write (serial* device, const void* data, unsigned int size)
return -1; // Error during select/poll call. return -1; // Error during select/poll call.
} else if (rc == 0) } else if (rc == 0)
break; // Timeout. break; // Timeout.
// Attempt to write data to the file descriptor.
int n = posix_write (device->fd, data + nbytes, size - nbytes);
if (n < 0) {
if (errno == EAGAIN) continue; // Retry.
TRACE ("posix_write");
return -1; // Error during write call.
} else {
nbytes += n; // Success.
}
} }
return nbytes; return nbytes;