18131186772

Committed 30 Sep 2025 01:16PM UTC coverage: 48.731% (-3.0%) from 51.712%

Build # 18131186772

Build Type

push

github

Committed by

vigna

Commit Message

Better error message

Run Details

0 of 2 new or added lines in 1 file covered. (0.0%)

114 existing lines in 12 files now uncovered.

1728 of 3546 relevant lines covered (48.73%)

1985043.52 hits per line

Source File
Press 'n' to go to next uncovered line, 'b' for previous

54.93

/src/impls/bit_reader.rs

/*
 * SPDX-FileCopyrightText: 2023 Tommaso Fontana
 * SPDX-FileCopyrightText: 2023 Inria
 * SPDX-FileCopyrightText: 2023 Sebastiano Vigna
 *
 * SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later
 */

use core::convert::Infallible;
#[cfg(feature = "mem_dbg")]
use mem_dbg::{MemDbg, MemSize};
use std::error::Error;

use crate::codes::params::{DefaultReadParams, ReadParams};
use crate::traits::*;

/// An implementation of [`BitRead`] for a [`WordRead`] with word `u64` and of
/// [`BitSeek`] for a [`WordSeek`].
///
/// This implementation accesses randomly the underlying [`WordRead`] without
/// any buffering. It is usually slower than
/// [`BufBitReader`](crate::impls::BufBitReader).
///
/// The peek word is `u32`. The value returned by
/// [`peek_bits`](crate::traits::BitRead::peek_bits) contains at least 32 bits
/// (extended with zeros beyond end of stream), that is, a full peek word.
///
/// The additional type parameter `RP` is used to select the parameters for the
/// instantanous codes, but the casual user should be happy with the default
/// value. See [`ReadParams`] for more details.
///
/// For additional flexibility, this structures implements [`std::io::Read`].
/// Note that because of coherence rules it is not possible to implement
/// [`std::io::Read`] for a generic [`BitRead`].

#[derive(Debug, Clone)]
#[cfg_attr(feature = "mem_dbg", derive(MemDbg, MemSize))]
pub struct BitReader<E: Endianness, WR, RP: ReadParams = DefaultReadParams> {
    /// The stream which we will read words from.
    data: WR,
    /// The index of the current bit.
    bit_index: u64,
    _marker: core::marker::PhantomData<(E, RP)>,
}

impl<E: Endianness, WR, RP: ReadParams> BitReader<E, WR, RP> {
    pub fn new(data: WR) -> Self {
        check_tables(32);
        Self {
            data,
            bit_index: 0,
            _marker: core::marker::PhantomData,
        }
    }
}

impl<
        E: Error + Send + Sync + 'static,
        WR: WordRead<Error = E, Word = u64> + WordSeek<Error = E>,
        RP: ReadParams,
    > BitRead<BE> for BitReader<BE, WR, RP>
{
    type Error = <WR as WordRead>::Error;
    type PeekWord = u32;

    #[inline]
    fn skip_bits(&mut self, n_bits: usize) -> Result<(), Self::Error> {
        self.bit_index += n_bits as u64;
        Ok(())
    }

    #[inline]
    fn read_bits(&mut self, n_bits: usize) -> Result<u64, Self::Error> {
        if n_bits == 0 {
            return Ok(0);
        }

        assert!(n_bits <= 64);

        self.data.set_word_pos(self.bit_index / 64)?;
        let in_word_offset = (self.bit_index % 64) as usize;

        let res = if (in_word_offset + n_bits) <= 64 {
            // single word access
            let word = self.data.read_word()?.to_be();
            (word << in_word_offset) >> (64 - n_bits)
        } else {
            // double word access
            let high_word = self.data.read_word()?.to_be();
            let low_word = self.data.read_word()?.to_be();
            let shamt1 = 64 - n_bits;
            let shamt2 = 128 - in_word_offset - n_bits;
            ((high_word << in_word_offset) >> shamt1) | (low_word >> shamt2)
        };
        self.bit_index += n_bits as u64;
        Ok(res)
    }

    #[inline]
    fn peek_bits(&mut self, n_bits: usize) -> Result<u32, Self::Error> {
        if n_bits == 0 {
            return Ok(0);
        }

        assert!(n_bits <= 32);

        self.data.set_word_pos(self.bit_index / 64)?;
        let in_word_offset = (self.bit_index % 64) as usize;

        let res = if (in_word_offset + n_bits) <= 64 {
            // single word access
            let word = self.data.read_word()?.to_be();
            (word << in_word_offset) >> (64 - n_bits)
        } else {
            // double word access
            let high_word = self.data.read_word()?.to_be();
            let low_word = self.data.read_word()?.to_be();
            let shamt1 = 64 - n_bits;
            let shamt2 = 128 - in_word_offset - n_bits;
            ((high_word << in_word_offset) >> shamt1) | (low_word >> shamt2)
        };
        Ok(res as u32)
    }

    #[inline]
    fn read_unary(&mut self) -> Result<u64, Self::Error> {
        self.data.set_word_pos(self.bit_index / 64)?;
        let in_word_offset = self.bit_index % 64;
        let mut bits_in_word = 64 - in_word_offset;
        let mut total = 0;

        let mut word = self.data.read_word()?.to_be();
        word <<= in_word_offset;
        loop {
            let zeros = word.leading_zeros() as u64;
            // the unary code fits in the word
            if zeros < bits_in_word {
                self.bit_index += total + zeros + 1;
                return Ok(total + zeros);
            }
            total += bits_in_word;
            bits_in_word = 64;
            word = self.data.read_word()?.to_be();
        }
    }

    #[inline(always)]
    fn skip_bits_after_peek(&mut self, n: usize) {
        self.bit_index += n as u64;
    }
}

impl<WR: WordSeek, RP: ReadParams> BitSeek for BitReader<LE, WR, RP> {
    type Error = Infallible;

    fn bit_pos(&mut self) -> Result<u64, Self::Error> {
        Ok(self.bit_index)
    }

    fn set_bit_pos(&mut self, bit_index: u64) -> Result<(), Self::Error> {
        self.bit_index = bit_index;
        Ok(())
    }
}

impl<WR: WordSeek, RP: ReadParams> BitSeek for BitReader<BE, WR, RP> {
    type Error = Infallible;

    fn bit_pos(&mut self) -> Result<u64, Self::Error> {
        Ok(self.bit_index)
    }

    fn set_bit_pos(&mut self, bit_index: u64) -> Result<(), Self::Error> {
        self.bit_index = bit_index;
        Ok(())
    }
}

impl<
        E: Error + Send + Sync + 'static,
        WR: WordRead<Error = E, Word = u64> + WordSeek<Error = E>,
        RP: ReadParams,
    > BitRead<LE> for BitReader<LE, WR, RP>
{
    type Error = <WR as WordRead>::Error;
    type PeekWord = u32;

    #[inline]
    fn skip_bits(&mut self, n_bits: usize) -> Result<(), Self::Error> {
        self.bit_index += n_bits as u64;
        Ok(())
    }

    #[inline]
    fn read_bits(&mut self, n_bits: usize) -> Result<u64, Self::Error> {
        #[cfg(feature = "checks")]
        assert!(n_bits <= 64);

        if n_bits == 0 {
            return Ok(0);
        }

        self.data.set_word_pos(self.bit_index / 64)?;
        let in_word_offset = (self.bit_index % 64) as usize;

        let res = if (in_word_offset + n_bits) <= 64 {
            // single word access
            let word = self.data.read_word()?.to_le();
            let shamt = 64 - n_bits;
            (word << (shamt - in_word_offset)) >> shamt
        } else {
            // double word access
            let low_word = self.data.read_word()?.to_le();
            let high_word = self.data.read_word()?.to_le();
            let shamt1 = 128 - in_word_offset - n_bits;
            let shamt2 = 64 - n_bits;
            ((high_word << shamt1) >> shamt2) | (low_word >> in_word_offset)
        };
        self.bit_index += n_bits as u64;
        Ok(res)
    }

    #[inline]
    fn peek_bits(&mut self, n_bits: usize) -> Result<u32, Self::Error> {
        if n_bits == 0 {
            return Ok(0);
        }

        assert!(n_bits <= 32);

        self.data.set_word_pos(self.bit_index / 64)?;
        let in_word_offset = (self.bit_index % 64) as usize;

        let res = if (in_word_offset + n_bits) <= 64 {
            // single word access
            let word = self.data.read_word()?.to_le();
            let shamt = 64 - n_bits;
            (word << (shamt - in_word_offset)) >> shamt
        } else {
            // double word access
            let low_word = self.data.read_word()?.to_le();
            let high_word = self.data.read_word()?.to_le();
            let shamt1 = 128 - in_word_offset - n_bits;
            let shamt2 = 64 - n_bits;
            ((high_word << shamt1) >> shamt2) | (low_word >> in_word_offset)
        };
        Ok(res as u32)
    }

    #[inline]
    fn read_unary(&mut self) -> Result<u64, Self::Error> {
        self.data.set_word_pos(self.bit_index / 64)?;
        let in_word_offset = self.bit_index % 64;
        let mut bits_in_word = 64 - in_word_offset;
        let mut total = 0;

        let mut word = self.data.read_word()?.to_le();
        word >>= in_word_offset;
        loop {
            let zeros = word.trailing_zeros() as u64;
            // the unary code fits in the word
            if zeros < bits_in_word {
                self.bit_index += total + zeros + 1;
                return Ok(total + zeros);
            }
            total += bits_in_word;
            bits_in_word = 64;
            word = self.data.read_word()?.to_le();
        }
    }

    #[inline(always)]
    fn skip_bits_after_peek(&mut self, n: usize) {
        self.bit_index += n as u64;
    }
}

impl<
        E: Error + Send + Sync + 'static,
        WR: WordRead<Error = E, Word = u64> + WordSeek<Error = E>,
        RP: ReadParams,
    > std::io::Read for BitReader<LE, WR, RP>
{
    fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
        let mut iter = buf.chunks_exact_mut(8);

        for chunk in &mut iter {
            let word = self
                .read_bits(64)
                .map_err(|_| std::io::ErrorKind::UnexpectedEof)?;
            chunk.copy_from_slice(&word.to_le_bytes());
        }

        let rem = iter.into_remainder();
        if !rem.is_empty() {
            let word = self
                .read_bits(rem.len() * 8)
                .map_err(|_| std::io::ErrorKind::UnexpectedEof)?;
            rem.copy_from_slice(&word.to_le_bytes()[..rem.len()]);
        }

        Ok(buf.len())
    }
}

impl<
        E: Error + Send + Sync + 'static,
        WR: WordRead<Error = E, Word = u64> + WordSeek<Error = E>,
        RP: ReadParams,
    > std::io::Read for BitReader<BE, WR, RP>
{
    fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
        let mut iter = buf.chunks_exact_mut(8);

        for chunk in &mut iter {
            let word = self
                .read_bits(64)
                .map_err(|_| std::io::ErrorKind::UnexpectedEof)?;
            chunk.copy_from_slice(&word.to_be_bytes());
        }

        let rem = iter.into_remainder();
        if !rem.is_empty() {
            let word = self
                .read_bits(rem.len() * 8)
                .map_err(|_| std::io::ErrorKind::UnexpectedEof)?;
            rem.copy_from_slice(&word.to_be_bytes()[8 - rem.len()..]);
        }

        Ok(buf.len())
    }
}

1	/*
2	* SPDX-FileCopyrightText: 2023 Tommaso Fontana
3	* SPDX-FileCopyrightText: 2023 Inria
4	* SPDX-FileCopyrightText: 2023 Sebastiano Vigna
5	*
6	* SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later
7	*/
8
9	use core::convert::Infallible;
10	#[cfg(feature = "mem_dbg")]
11	use mem_dbg::{MemDbg, MemSize};
12	use std::error::Error;
13
14	use crate::codes::params::{DefaultReadParams, ReadParams};
15	use crate::traits::*;
16
17	/// An implementation of [`BitRead`] for a [`WordRead`] with word `u64` and of
18	/// [`BitSeek`] for a [`WordSeek`].
19	///
20	/// This implementation accesses randomly the underlying [`WordRead`] without
21	/// any buffering. It is usually slower than
22	/// [`BufBitReader`](crate::impls::BufBitReader).
23	///
24	/// The peek word is `u32`. The value returned by
25	/// [`peek_bits`](crate::traits::BitRead::peek_bits) contains at least 32 bits
26	/// (extended with zeros beyond end of stream), that is, a full peek word.
27	///
28	/// The additional type parameter `RP` is used to select the parameters for the
29	/// instantanous codes, but the casual user should be happy with the default
30	/// value. See [`ReadParams`] for more details.
31	///
32	/// For additional flexibility, this structures implements [`std::io::Read`].
33	/// Note that because of coherence rules it is not possible to implement
34	/// [`std::io::Read`] for a generic [`BitRead`].
35
36	#[derive(Debug, Clone)]
37	#[cfg_attr(feature = "mem_dbg", derive(MemDbg, MemSize))]
38	pub struct BitReader<E: Endianness, WR, RP: ReadParams = DefaultReadParams> {
39	/// The stream which we will read words from.
40	data: WR,
41	/// The index of the current bit.
42	bit_index: u64,
43	_marker: core::marker::PhantomData<(E, RP)>,
44	}
45
46	impl<E: Endianness, WR, RP: ReadParams> BitReader<E, WR, RP> {
47	pub fn new(data: WR) -> Self {	938✔
48	check_tables(32);	938✔
49	Self {
50	data,
51	bit_index: 0,
52	_marker: core::marker::PhantomData,
53	}
54	}
55	}
56
57	impl<
58	E: Error + Send + Sync + 'static,
59	WR: WordRead<Error = E, Word = u64> + WordSeek<Error = E>,
60	RP: ReadParams,
61	> BitRead<BE> for BitReader<BE, WR, RP>
62	{
63	type Error = <WR as WordRead>::Error;
64	type PeekWord = u32;
65
66	#[inline]
67	fn skip_bits(&mut self, n_bits: usize) -> Result<(), Self::Error> {	×
68	self.bit_index += n_bits as u64;	×
69	Ok(())	×
70	}
71
72	#[inline]
73	fn read_bits(&mut self, n_bits: usize) -> Result<u64, Self::Error> {	2,497✔
74	if n_bits == 0 {	2,497✔
75	return Ok(0);	12✔
76	}
77
UNCOV 78	assert!(n_bits <= 64);	×
79
80	self.data.set_word_pos(self.bit_index / 64)?;	7,455✔
81	let in_word_offset = (self.bit_index % 64) as usize;	2,485✔
82
83	let res = if (in_word_offset + n_bits) <= 64 {	2,485✔
84	// single word access
85	let word = self.data.read_word()?.to_be();	6,270✔
86	(word << in_word_offset) >> (64 - n_bits)	×
87	} else {
88	// double word access
89	let high_word = self.data.read_word()?.to_be();	790✔
90	let low_word = self.data.read_word()?.to_be();	395✔
91	let shamt1 = 64 - n_bits;	×
92	let shamt2 = 128 - in_word_offset - n_bits;	×
93	((high_word << in_word_offset) >> shamt1) \| (low_word >> shamt2)	×
94	};
95	self.bit_index += n_bits as u64;	×
96	Ok(res)	×
97	}
98
99	#[inline]
100	fn peek_bits(&mut self, n_bits: usize) -> Result<u32, Self::Error> {	66✔
101	if n_bits == 0 {	66✔
102	return Ok(0);	×
103	}
104
UNCOV 105	assert!(n_bits <= 32);	×
106
107	self.data.set_word_pos(self.bit_index / 64)?;	198✔
108	let in_word_offset = (self.bit_index % 64) as usize;	66✔
109
110	let res = if (in_word_offset + n_bits) <= 64 {	66✔
111	// single word access
112	let word = self.data.read_word()?.to_be();	192✔
113	(word << in_word_offset) >> (64 - n_bits)	×
114	} else {
115	// double word access
116	let high_word = self.data.read_word()?.to_be();	4✔
117	let low_word = self.data.read_word()?.to_be();	2✔
118	let shamt1 = 64 - n_bits;	×
119	let shamt2 = 128 - in_word_offset - n_bits;	×
120	((high_word << in_word_offset) >> shamt1) \| (low_word >> shamt2)	×
121	};
122	Ok(res as u32)	×
123	}
124
125	#[inline]
126	fn read_unary(&mut self) -> Result<u64, Self::Error> {	814✔
127	self.data.set_word_pos(self.bit_index / 64)?;	2,442✔
128	let in_word_offset = self.bit_index % 64;	814✔
UNCOV 129	let mut bits_in_word = 64 - in_word_offset;	×
UNCOV 130	let mut total = 0;	×
131
132	let mut word = self.data.read_word()?.to_be();	814✔
133	word <<= in_word_offset;	×
134	loop {	×
135	let zeros = word.leading_zeros() as u64;	14,174✔
136	// the unary code fits in the word
137	if zeros < bits_in_word {	7,087✔
138	self.bit_index += total + zeros + 1;	814✔
139	return Ok(total + zeros);	814✔
140	}
UNCOV 141	total += bits_in_word;	×
UNCOV 142	bits_in_word = 64;	×
143	word = self.data.read_word()?.to_be();	6,273✔
144	}
145	}
146
147	#[inline(always)]
148	fn skip_bits_after_peek(&mut self, n: usize) {	10✔
149	self.bit_index += n as u64;	10✔
150	}
151	}
152
153	impl<WR: WordSeek, RP: ReadParams> BitSeek for BitReader<LE, WR, RP> {
154	type Error = Infallible;
155
156	fn bit_pos(&mut self) -> Result<u64, Self::Error> {	3,225✔
157	Ok(self.bit_index)	3,225✔
158	}
159
160	fn set_bit_pos(&mut self, bit_index: u64) -> Result<(), Self::Error> {	×
161	self.bit_index = bit_index;	×
162	Ok(())	×
163	}
164	}
165
166	impl<WR: WordSeek, RP: ReadParams> BitSeek for BitReader<BE, WR, RP> {
167	type Error = Infallible;
168
169	fn bit_pos(&mut self) -> Result<u64, Self::Error> {	3,225✔
170	Ok(self.bit_index)	3,225✔
171	}
172
173	fn set_bit_pos(&mut self, bit_index: u64) -> Result<(), Self::Error> {	×
174	self.bit_index = bit_index;	×
175	Ok(())	×
176	}
177	}
178
179	impl<
180	E: Error + Send + Sync + 'static,
181	WR: WordRead<Error = E, Word = u64> + WordSeek<Error = E>,
182	RP: ReadParams,
183	> BitRead<LE> for BitReader<LE, WR, RP>
184	{
185	type Error = <WR as WordRead>::Error;
186	type PeekWord = u32;
187
188	#[inline]
189	fn skip_bits(&mut self, n_bits: usize) -> Result<(), Self::Error> {	×
190	self.bit_index += n_bits as u64;	×
191	Ok(())	×
192	}
193
194	#[inline]
195	fn read_bits(&mut self, n_bits: usize) -> Result<u64, Self::Error> {	2,497✔
196	#[cfg(feature = "checks")]
197	assert!(n_bits <= 64);	4,994✔
198
199	if n_bits == 0 {	2,497✔
200	return Ok(0);	12✔
201	}
202
UNCOV 203	self.data.set_word_pos(self.bit_index / 64)?;	×
204	let in_word_offset = (self.bit_index % 64) as usize;	2,485✔
205
206	let res = if (in_word_offset + n_bits) <= 64 {	2,485✔
207	// single word access
208	let word = self.data.read_word()?.to_le();	6,270✔
209	let shamt = 64 - n_bits;	×
210	(word << (shamt - in_word_offset)) >> shamt	×
211	} else {
212	// double word access
213	let low_word = self.data.read_word()?.to_le();	790✔
214	let high_word = self.data.read_word()?.to_le();	395✔
215	let shamt1 = 128 - in_word_offset - n_bits;	×
216	let shamt2 = 64 - n_bits;	×
217	((high_word << shamt1) >> shamt2) \| (low_word >> in_word_offset)	×
218	};
219	self.bit_index += n_bits as u64;	×
220	Ok(res)	×
221	}
222
223	#[inline]
224	fn peek_bits(&mut self, n_bits: usize) -> Result<u32, Self::Error> {	66✔
225	if n_bits == 0 {	66✔
226	return Ok(0);	×
227	}
228
UNCOV 229	assert!(n_bits <= 32);	×
230
231	self.data.set_word_pos(self.bit_index / 64)?;	198✔
232	let in_word_offset = (self.bit_index % 64) as usize;	66✔
233
234	let res = if (in_word_offset + n_bits) <= 64 {	66✔
235	// single word access
236	let word = self.data.read_word()?.to_le();	192✔
237	let shamt = 64 - n_bits;	×
238	(word << (shamt - in_word_offset)) >> shamt	×
239	} else {
240	// double word access
241	let low_word = self.data.read_word()?.to_le();	4✔
242	let high_word = self.data.read_word()?.to_le();	2✔
243	let shamt1 = 128 - in_word_offset - n_bits;	×
244	let shamt2 = 64 - n_bits;	×
245	((high_word << shamt1) >> shamt2) \| (low_word >> in_word_offset)	×
246	};
247	Ok(res as u32)	×
248	}
249
250	#[inline]
251	fn read_unary(&mut self) -> Result<u64, Self::Error> {	814✔
252	self.data.set_word_pos(self.bit_index / 64)?;	2,442✔
253	let in_word_offset = self.bit_index % 64;	814✔
UNCOV 254	let mut bits_in_word = 64 - in_word_offset;	×
UNCOV 255	let mut total = 0;	×
256
257	let mut word = self.data.read_word()?.to_le();	814✔
258	word >>= in_word_offset;	×
259	loop {	×
260	let zeros = word.trailing_zeros() as u64;	14,174✔
261	// the unary code fits in the word
262	if zeros < bits_in_word {	7,087✔
263	self.bit_index += total + zeros + 1;	814✔
264	return Ok(total + zeros);	814✔
265	}
UNCOV 266	total += bits_in_word;	×
UNCOV 267	bits_in_word = 64;	×
268	word = self.data.read_word()?.to_le();	6,273✔
269	}
270	}
271
272	#[inline(always)]
273	fn skip_bits_after_peek(&mut self, n: usize) {	10✔
274	self.bit_index += n as u64;	10✔
275	}
276	}
277
278	impl<
279	E: Error + Send + Sync + 'static,
280	WR: WordRead<Error = E, Word = u64> + WordSeek<Error = E>,
281	RP: ReadParams,
282	> std::io::Read for BitReader<LE, WR, RP>
283	{
284	fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {	7✔
285	let mut iter = buf.chunks_exact_mut(8);	21✔
286
287	for chunk in &mut iter {	33✔
288	let word = self	26✔
289	.read_bits(64)
290	.map_err(\|_\| std::io::ErrorKind::UnexpectedEof)?;	13✔
291	chunk.copy_from_slice(&word.to_le_bytes());	×
292	}
293
294	let rem = iter.into_remainder();	7✔
UNCOV 295	if !rem.is_empty() {	×
296	let word = self	12✔
UNCOV 297	.read_bits(rem.len() * 8)	×
UNCOV 298	.map_err(\|_\| std::io::ErrorKind::UnexpectedEof)?;	×
299	rem.copy_from_slice(&word.to_le_bytes()[..rem.len()]);	×
300	}
301
302	Ok(buf.len())	7✔
303	}
304	}
305
306	impl<
307	E: Error + Send + Sync + 'static,
308	WR: WordRead<Error = E, Word = u64> + WordSeek<Error = E>,
309	RP: ReadParams,
310	> std::io::Read for BitReader<BE, WR, RP>
311	{
312	fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {	7✔
313	let mut iter = buf.chunks_exact_mut(8);	21✔
314
315	for chunk in &mut iter {	33✔
316	let word = self	26✔
317	.read_bits(64)
318	.map_err(\|_\| std::io::ErrorKind::UnexpectedEof)?;	13✔
319	chunk.copy_from_slice(&word.to_be_bytes());	×
320	}
321
322	let rem = iter.into_remainder();	7✔
UNCOV 323	if !rem.is_empty() {	×
324	let word = self	12✔
UNCOV 325	.read_bits(rem.len() * 8)	×
UNCOV 326	.map_err(\|_\| std::io::ErrorKind::UnexpectedEof)?;	×
327	rem.copy_from_slice(&word.to_be_bytes()[8 - rem.len()..]);	×
328	}
329
330	Ok(buf.len())	7✔
331	}
332	}

vigna / dsi-bitstream-rs / 18131186772

Source File Press 'n' to go to next uncovered line, 'b' for previous

Source File
Press 'n' to go to next uncovered line, 'b' for previous