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# zx_channel_read_etc
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Read a message from a channel.
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#include <zircon/syscalls.h>
zx_status_t zx_channel_read_etc(zx_handle_t handle,
uint32_t options,
void* bytes,
zx_handle_info_t* handles,
uint32_t num_bytes,
uint32_t num_handles,
uint32_t* actual_bytes,
uint32_t* actual_handles);
See [`zx_channel_read()`] for a full description.
Both forms of read behave the same except that [`zx_channel_read()`] returns an
array of raw `zx_handle_t` handle values while `zx_channel_read_etc()` returns
an array of `zx_handle_info_t` structures of the form:
typedef struct {
zx_handle_t handle; // handle value
zx_obj_type_t type; // type of object, see ZX_OBJ_TYPE_
zx_rights_t rights; // handle rights
uint32_t unused; // set to zero
} zx_handle_info_t;
When communicating to an untrusted party over a channel, it is recommended
that the `zx_channel_read_etc()` form is used and each handle type and rights
are validated against the expected values.
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*handle* must be of type **ZX_OBJ_TYPE_CHANNEL** and have **ZX_RIGHT_READ**.
Both forms of read return **ZX_OK** on success, if *actual_bytes*
and *actual_handles* (if non-NULL), contain the exact number of bytes
and count of handles read.
**ZX_ERR_BAD_HANDLE** *handle* is not a valid handle.
**ZX_ERR_WRONG_TYPE** *handle* is not a channel handle.
**ZX_ERR_INVALID_ARGS** If any of *bytes*, *handles*, *actual_bytes*, or
*actual_handles* are non-NULL and an invalid pointer.
**ZX_ERR_ACCESS_DENIED** *handle* does not have **ZX_RIGHT_READ**.
**ZX_ERR_SHOULD_WAIT** The channel contained no messages to read.
**ZX_ERR_PEER_CLOSED** The other side of the channel is closed.
**ZX_ERR_NO_MEMORY** Failure due to lack of memory.
There is no good way for userspace to handle this (unlikely) error.
In a future build this error will no longer occur.
**ZX_ERR_BUFFER_TOO_SMALL** The provided *bytes* or *handles* buffers
are too small (in which case, the minimum sizes necessary to receive
the message will be written to *actual_bytes* and *actual_handles*,
provided they are non-NULL). If *options* has **ZX_CHANNEL_READ_MAY_DISCARD**
set, then the message is discarded.
*num_handles* and *actual_handles* are counts of the number of elements
in the *handles* array, not its size in bytes.
- [`zx_channel_call()`]
- [`zx_channel_create()`]
- [`zx_channel_read()`]
- [`zx_channel_write()`]
- [`zx_channel_write_etc()`]
- [`zx_handle_close()`]
- [`zx_handle_duplicate()`]
- [`zx_handle_replace()`]
- [`zx_object_wait_async()`]
- [`zx_object_wait_many()`]
- [`zx_object_wait_one()`]
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