1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
#![no_std]
use core::{mem, ptr};
use libc::c_int;
pub mod ffi {
#![allow(clippy::all, non_camel_case_types)]
include!("bindings.rs");
}
#[cfg(not(feature = "float"))]
pub type Sample = i16;
#[cfg(feature = "float")]
pub type Sample = f32;
pub struct Decoder<'a> {
data: &'a [u8],
ffi_frame: ffi::mp3dec_frame_info_t,
instance: ffi::mp3dec_t,
pcm: [Sample; ffi::MINIMP3_MAX_SAMPLES_PER_FRAME as usize],
last_frame_len: Option<usize>,
}
#[derive(Debug)]
pub struct Frame<'a> {
pub bitrate: u32,
pub channels: u32,
pub mpeg_layer: u32,
pub samples: &'a [Sample],
pub sample_count: u32,
pub sample_rate: u32,
pub source_len: usize,
}
impl<'a> Decoder<'a> {
pub fn new(data: &'a (impl AsRef<[u8]> + ?Sized)) -> Self {
Self {
data: data.as_ref(),
ffi_frame: unsafe { mem::zeroed() },
instance: unsafe {
let mut decoder: ffi::mp3dec_t = mem::zeroed();
ffi::mp3dec_init(&mut decoder);
decoder
},
pcm: [Default::default(); ffi::MINIMP3_MAX_SAMPLES_PER_FRAME as usize],
last_frame_len: None,
}
}
pub fn next_frame(&mut self) -> Option<Frame> {
self.last_frame_len = None;
unsafe {
let out_ptr: *mut Sample = self.pcm.as_mut_ptr();
let samples = self.ffi_decode_frame(out_ptr) as u32;
self.data = self
.data
.get_unchecked(self.ffi_frame.frame_bytes as usize..);
if samples > 0 {
Some(Frame {
bitrate: self.ffi_frame.bitrate_kbps as u32,
channels: self.ffi_frame.channels as u32,
samples: self
.pcm
.get_unchecked(..(samples * self.ffi_frame.channels as u32) as usize),
sample_rate: self.ffi_frame.hz as u32,
mpeg_layer: self.ffi_frame.layer as u32,
sample_count: samples,
source_len: self.ffi_frame.frame_bytes as usize,
})
} else if self.ffi_frame.frame_bytes != 0 {
self.next_frame()
} else {
None
}
}
}
pub fn peek_frame(&mut self) -> Option<Frame> {
let samples = unsafe { self.ffi_decode_frame(ptr::null_mut()) as u32 };
if self.ffi_frame.frame_bytes != 0 {
self.last_frame_len = Some(self.ffi_frame.frame_bytes as usize);
Some(Frame {
bitrate: self.ffi_frame.bitrate_kbps as u32,
channels: self.ffi_frame.channels as u32,
mpeg_layer: self.ffi_frame.layer as u32,
samples: &[],
sample_rate: self.ffi_frame.hz as u32,
sample_count: samples,
source_len: self.ffi_frame.frame_bytes as usize,
})
} else {
None
}
}
pub fn skip_frame(&mut self) {
if let Some(len) = self.frame_bytes() {
unsafe { self.data = self.data.get_unchecked(len..) }
}
}
fn frame_bytes(&mut self) -> Option<usize> {
let len = self
.last_frame_len
.or_else(|| self.peek_frame().map(|f| f.source_len));
self.last_frame_len = None;
len
}
unsafe fn ffi_decode_frame(&mut self, pcm: *mut Sample) -> c_int {
ffi::mp3dec_decode_frame(
&mut self.instance,
self.data.as_ptr(),
self.data.len() as c_int,
pcm,
&mut self.ffi_frame,
)
}
}