vmo_read - read bytes from the VMO


#include <magenta/syscalls.h>

mx_status_t mx_vmo_read(mx_handle_t handle, void* data, uint64_t offset, size_t len,
                        size_t* actual);


vmo_read() attempts to read len bytes from a VMO at offset. The number of actual bytes read is returned in actual.

data pointer to a user buffer to read bytes into.

len number of bytes to attempt to read. data buffer should be large enough for at least this many bytes.

actual returns the actual number of bytes read, which may be anywhere from 0 to len. If a read extends beyond the size of the VMO, the actual bytes read will be trimmed. If the read starts at or beyond the size of the VMO, MX_ERR_OUT_OF_RANGE will be returned.


mx_vmo_read() returns MX_OK on success. In the event of failure, a negative error value is returned.


MX_ERR_BAD_HANDLE handle is not a valid handle.

MX_ERR_WRONG_TYPE handle is not a VMO handle.

MX_ERR_ACCESS_DENIED handle does not have the MX_RIGHT_READ right.

MX_ERR_INVALID_ARGS actual or data is an invalid pointer or NULL.

MX_ERR_OUT_OF_RANGE offset starts at or beyond the end of the VMO.


vmo_create, vmo_clone, vmo_write, vmo_get_size, vmo_set_size, vmo_op_range.