socket_read - read data from a socket
#include <zircon/syscalls.h>
zx_status_t zx_socket_read(zx_handle_t handle, uint32_t options,
void* buffer, size_t buffer_size,
size_t* actual) {
socket_read() attempts to read buffer_size bytes into buffer. If successful, the number of bytes actually read are return via actual.
If a NULL buffer and 0 buffer_size are passed in, then this syscall instead requests that the number of outstanding bytes to be returned via actual. In this case, if no bytes are available, this syscall will return ZX_OK, rather than ZX_ERR_SHOULD_WAIT.
If a NULL actual is passed in, it will be ignored.
If the socket was created with ZX_SOCKET_DATAGRAM, this syscall reads only the first available datagram in the socket (if one is present). If buffer is too small for the datagram, then the read will be truncated, and any remaining bytes in the datagram will be discarded.
If options is set to ZX_SOCKET_CONTROL, then socket_read() attempts to read from the socket control plane.
TODO(ZX-2399)
socket_read() returns ZX_OK on success, and writes into actual (if non-NULL) the exact number of bytes read.
ZX_ERR_BAD_HANDLE handle is not a valid handle.
ZX_ERR_BAD_STATE Either (a) options includes ZX_SOCKET_CONTROL and the socket was not created with ZX_SOCKET_HAS_CONTROL, or (b) reading has been disabled for this socket endpoint.
ZX_ERR_WRONG_TYPE handle is not a socket handle.
ZX_ERR_INVALID_ARGS If any of buffer or actual are non-NULL but invalid pointers, or if buffer is NULL but size is positive, or if options is not either zero or *ZX_SOCKET_CONTROL.
ZX_ERR_ACCESS_DENIED handle does not have ZX_RIGHT_READ.
ZX_ERR_SHOULD_WAIT The socket contained no data to read. (However, if a NULL buffer and 0 buffer_size are passed in, ZX_OK will be returned in this case.)
ZX_ERR_PEER_CLOSED The other side of the socket is closed and no data is readable.