1 /*
2  * Copyright 2003-2021 The Music Player Daemon Project
3  * http://www.musicpd.org
4  *
5  * This program is free software; you can redistribute it and/or modify
6  * it under the terms of the GNU General Public License as published by
7  * the Free Software Foundation; either version 2 of the License, or
8  * (at your option) any later version.
9  *
10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13  * GNU General Public License for more details.
14  *
15  * You should have received a copy of the GNU General Public License along
16  * with this program; if not, write to the Free Software Foundation, Inc.,
17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
18  */
19 
20 #include "Pack.hxx"
21 #include "util/ByteOrder.hxx"
22 
23 static void
pack_sample(uint8_t * dest,const int32_t * src0)24 pack_sample(uint8_t *dest, const int32_t *src0) noexcept
25 {
26 	const auto *src = (const uint8_t *)src0;
27 
28 	if (IsBigEndian())
29 		++src;
30 
31 	*dest++ = *src++;
32 	*dest++ = *src++;
33 	*dest++ = *src++;
34 }
35 
36 void
pcm_pack_24(uint8_t * dest,const int32_t * src,const int32_t * src_end)37 pcm_pack_24(uint8_t *dest, const int32_t *src, const int32_t *src_end) noexcept
38 {
39 	/* duplicate loop to help the compiler's optimizer (constant
40 	   parameter to the pack_sample() inline function) */
41 
42 	while (src < src_end) {
43 		pack_sample(dest, src++);
44 		dest += 3;
45 	}
46 }
47 
48 /**
49  * Construct a signed 24 bit integer from three bytes into a int32_t.
50  */
51 static constexpr int32_t
ConstructS24(uint8_t low,uint8_t mid,uint8_t high)52 ConstructS24(uint8_t low, uint8_t mid, uint8_t high) noexcept
53 {
54 	return int32_t(low) | (int32_t(mid) << 8) | (int32_t(high) << 16) |
55 		/* extend the sign bit */
56 		(high & 0x80 ? ~int32_t(0xffffff) : 0);
57 }
58 
59 /**
60  * Read a packed signed little-endian 24 bit integer.
61  */
62 gcc_pure
63 static int32_t
ReadS24LE(const uint8_t * src)64 ReadS24LE(const uint8_t *src) noexcept
65 {
66 	return ConstructS24(src[0], src[1], src[2]);
67 }
68 
69 /**
70  * Read a packed signed big-endian 24 bit integer.
71  */
72 gcc_pure
73 static int32_t
ReadS24BE(const uint8_t * src)74 ReadS24BE(const uint8_t *src) noexcept
75 {
76 	return ConstructS24(src[2], src[1], src[0]);
77 }
78 
79 /**
80  * Read a packed signed native-endian 24 bit integer.
81  */
82 gcc_pure
83 static int32_t
ReadS24(const uint8_t * src)84 ReadS24(const uint8_t *src) noexcept
85 {
86 	return IsBigEndian() ? ReadS24BE(src) : ReadS24LE(src);
87 }
88 
89 void
pcm_unpack_24(int32_t * dest,const uint8_t * src,const uint8_t * src_end)90 pcm_unpack_24(int32_t *dest,
91 	      const uint8_t *src, const uint8_t *src_end) noexcept
92 {
93 	while (src < src_end) {
94 		*dest++ = ReadS24(src);
95 		src += 3;
96 	}
97 }
98 
99 void
pcm_unpack_24be(int32_t * dest,const uint8_t * src,const uint8_t * src_end)100 pcm_unpack_24be(int32_t *dest,
101 		const uint8_t *src, const uint8_t *src_end) noexcept
102 {
103 	while (src < src_end) {
104 		*dest++ = ReadS24BE(src);
105 		src += 3;
106 	}
107 }
108