70             perf_event_mmap_page.data_head = 0;  in init()
82     fn can_write(&self, data_size: usize, data_tail: usize, data_head: usize) -> bool {  in can_write()
83         if (data_head + 1) % self.data_region_size == data_tail {  in can_write()
87         let capacity = if data_head >= data_tail {  in can_write()
88             self.data_region_size - data_head + data_tail  in can_write()
90             data_tail - data_head  in can_write()
97         let data_head = unsafe { &mut (*(self.ptr as *mut perf_event_mmap_page)).data_head };  in write_event()  localVariable
103             self.can_write(sample_size, *data_tail as usize, *data_head as usize);  in write_event()
128                 *data_head as usize,  in write_event()
131                 let new_data_head = self.write_lost(*data_head as usize)?;  in write_event()
132                 *data_head = new_data_head as u64;  in write_event()
142                 let new_data_head = self.write_sample(data, *data_head as usize)?;  in write_event()
143                 *data_head = new_data_head as u64;  in write_event()
157     fn write_any(&mut self, data: &[u8], data_head: usize) -> Result<usize> {  in write_any()
161         let end = (data_head + data_len) % data_region_len;  in write_any()
162         let start = data_head;  in write_any()
174     fn write_sample(&mut self, data: &[u8], data_head: usize) -> Result<usize> {  in write_sample()
186         let new_head = self.write_any(perf_sample.s_hdr.as_bytes(), data_head)?;  in write_sample()
193     fn write_lost(&mut self, data_head: usize) -> Result<usize> {  in write_lost()
203         self.write_any(lost.as_bytes(), data_head)  in write_lost()
208         let data_head = unsafe { &(*(self.ptr as *mut perf_event_mmap_page)).data_head };  in readable()  localVariable
209         data_tail != data_head  in readable()