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Rewrite get_bits().
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@icefoxen
icefoxen committed Sep 5, 2018
1 parent 5aafc11 commit 4345245
Showing 1 changed file with 90 additions and 43 deletions.
133 changes: 90 additions & 43 deletions src/corrode_test.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -120,7 +120,9 @@ impl Clone for FrameInfo {
pub struct Bs<'a> {
// pub buf: *const u8,
pub buf: &'a [u8],
// TODO: Should be usize
pub pos: i32,
// TODO: Should be usize
pub limit: i32,
}

Expand Down Expand Up @@ -516,43 +518,36 @@ pub unsafe fn mp3d_find_frame(
}
}

unsafe fn get_bits(bs: &mut Bs, n: i32) -> u32 {
let mut next: u32;

// Rewritten; original is on
// https://github.com/lieff/minimp3/blob/master/minimp3.h#L232
fn get_bits(bs: &mut Bs, n: u32) -> u32 {
let n = n as i32;
let s = bs.pos & 7;
let mut cache: u32 = 0;
let s: u32 = (bs.pos & 7) as (u32);
let mut shl: i32 = (n as (u32)).wrapping_add(s) as (i32);
let mut p: *const u8 = (*bs).buf.as_ptr().offset(((*bs).pos >> 3) as isize);
if {
(*bs).pos = (*bs).pos + n;
(*bs).pos
} > (*bs).limit
{
0
} else {
next = (*{
let _old = p;
p = p.offset(1);
_old
} as (i32) & 255 >> s) as (u32);
loop {
if !({
shl = shl - 8;
shl
} > 0)
{
break;
}
cache = cache | next << shl;
next = *{
let _old = p;
p = p.offset(1);
_old
} as (u32);
}
cache | next >> -shl
let mut shl = n + s;
let mut p = (bs.pos >> 3) as usize;
bs.pos += n as i32;
if bs.pos > bs.limit {
return 0;
}
let mut next = bs.buf[p] & ((255 & s) as u8);
p += 1;
shl -= 8;
while shl > 0 {
shl -= 8;
cache |= (next as u32).wrapping_shl(shl as u32);
next = bs.buf[p];
p += 1;
}

// cache | ((next as u32) >> -shl)
// Why on Eris's earth is this shifting by an almost-certainly-negative
// number?
cache | ((next as u32).wrapping_shl(shl as u32))
}


#[derive(Copy)]
#[repr(C)]
pub struct L12ScaleInfo {
Expand Down Expand Up @@ -793,7 +788,7 @@ unsafe fn l12_read_scale_info(hdr: &[u8], bs: &mut Bs, sci: &mut L12ScaleInfo) {
let mut subband_alloc: *const L12SubbandAlloc = l12_subband_alloc_table(hdr, &mut *sci);
let mut i: i32;
let mut k: i32 = 0;
let mut ba_bits: i32 = 0;
let mut ba_bits: u32 = 0;
let mut ba_code_tab: *const u8 = G_BITALLOC_CODE_TAB.as_ptr();
i = 0;
loop {
Expand All @@ -803,7 +798,7 @@ unsafe fn l12_read_scale_info(hdr: &[u8], bs: &mut Bs, sci: &mut L12ScaleInfo) {
let mut ba: u8;
if i == k {
k = k + (*subband_alloc).band_count as (i32);
ba_bits = (*subband_alloc).code_tab_width as (i32);
ba_bits = (*subband_alloc).code_tab_width as (u32);
ba_code_tab = G_BITALLOC_CODE_TAB
.as_ptr()
.offset((*subband_alloc).tab_offset as isize);
Expand Down Expand Up @@ -884,13 +879,13 @@ unsafe fn l12_dequantize_granule(
if !(k < group_size) {
break;
}
*dst.offset(k as isize) = (get_bits(bs, ba) as (i32) - half) as f32;
*dst.offset(k as isize) = (get_bits(bs, ba as u32) as (i32) - half) as f32;
k = k + 1;
}
} else {
let mod_: u32 = ((2 << ba - 17) + 1) as (u32);
let mut code: u32 =
get_bits(bs, mod_.wrapping_add(2).wrapping_sub(mod_ >> 3) as (i32));
get_bits(bs, mod_.wrapping_add(2).wrapping_sub(mod_ >> 3) as (u32));
k = 0;
loop {
if !(k < group_size) {
Expand Down Expand Up @@ -1558,7 +1553,7 @@ unsafe fn l3_read_side_info(bs: &mut Bs, mut gr: *mut L3GrInfo, hdr: &[u8]) -> i
let mut sr_idx: i32 =
(hdr[2] as (i32) >> 2 & 3) + ((hdr[1] as (i32) >> 3 & 1) + (hdr[1] as (i32) >> 4 & 1)) * 3;
sr_idx = sr_idx - (sr_idx != 0) as (i32);
let mut gr_count: i32 = if hdr[3] as (i32) & 0xc0 == 0xc0 { 1 } else { 2 };
let mut gr_count: u32 = if hdr[3] as (i32) & 0xc0 == 0xc0 { 1 } else { 2 };
if hdr[1] as (i32) & 0x8 != 0 {
gr_count = gr_count * 2;
main_data_begin = get_bits(bs, 9) as (i32);
Expand Down Expand Up @@ -1689,7 +1684,7 @@ unsafe fn l3_restore_reservoir(
((*h).reserv >= main_data_begin) as (i32)
}

unsafe fn l3_read_scalefactors(
fn l3_read_scalefactors(
mut scf: &mut [u8],
mut ist_pos: &mut [u8],
scf_size: &[u8],
Expand All @@ -1713,7 +1708,7 @@ unsafe fn l3_read_scalefactors(
// );
scf.copy_from_slice(&ist_pos[..cnt]);
} else {
let bits: i32 = scf_size[i] as (i32);
let bits: u32 = scf_size[i] as (u32);
if bits == 0 {
// memset(scf as (*mut ::std::os::raw::c_void), 0, cnt as usize);
// memset(
Expand Down Expand Up @@ -1785,7 +1780,7 @@ fn l3_ldexp_q2(mut y: f32, mut exp_q2: i32) -> f32 {
y
}

unsafe fn l3_decode_scalefactors(
fn l3_decode_scalefactors(
hdr: &[u8],
ist_pos: &mut [u8],
bs: &mut Bs,
Expand Down Expand Up @@ -2781,7 +2776,7 @@ fn l3_change_sign(mut grbuf: &mut [f32]) {
}
}

unsafe fn l3_decode(h: &mut Mp3Dec, s: &mut Mp3DecScratch, mut gr_info: &mut [L3GrInfo], nch: i32) {
fn l3_decode(h: &mut Mp3Dec, s: &mut Mp3DecScratch, mut gr_info: &mut [L3GrInfo], nch: i32) {
let mut ch: i32;
ch = 0;
loop {
Expand All @@ -2797,13 +2792,15 @@ unsafe fn l3_decode(h: &mut Mp3Dec, s: &mut Mp3DecScratch, mut gr_info: &mut [L3
&mut s.scf,
ch,
);
unsafe {
l3_huffman(
(*s).grbuf[ch as usize].as_mut_ptr(),
&mut (*s).bs,
&gr_info[ch as usize],
(*s).scf.as_mut_ptr() as (*const f32),
layer3gr_limit,
);
}
ch = ch + 1;
}
if (*h).header[3] as (i32) & 0x10 != 0 {
Expand Down Expand Up @@ -3075,7 +3072,7 @@ mod tests {
assert_eq!(2 + 2, 4);
}

use super::increment_by_mut;
use super::*;
#[test]
fn test_increment_by_mut() {
let slice: Vec<i32> = vec![1, 2, 3, 4, 5, 6];
Expand All @@ -3099,4 +3096,54 @@ mod tests {
let mut slice_to_mongle: &mut [i32] = &mut slice.clone();
increment_by_mut(&mut slice_to_mongle, 99);
}

#[test]
fn test_rewritten_get_bits() {
unsafe fn get_bits_corroded(bs: &mut Bs, n: i32) -> u32 {
let mut next: u32;
let mut cache: u32 = 0;
let s: u32 = (bs.pos & 7) as (u32);
let mut shl: i32 = (n as (u32)).wrapping_add(s) as (i32);
let mut p: *const u8 = (*bs).buf.as_ptr().offset(((*bs).pos >> 3) as isize);
if {
(*bs).pos = (*bs).pos + n;
(*bs).pos
} > (*bs).limit
{
0
} else {
next = (*{
let _old = p;
p = p.offset(1);
_old
} as (i32) & 255 >> s) as (u32);
loop {
if !({
shl = shl - 8;
shl
} > 0)
{
break;
}
cache = cache | next << shl;
next = *{
let _old = p;
p = p.offset(1);
_old
} as (u32);
}
cache | next >> -shl
}
}

let data = vec![1,2,3,4,5,6,7,8,9,10];
let bs = &mut Bs::new(&data, 0);
// I'm going to crudely assume 0x8FFF is
// Big Enough, I suppose.
for i in 0..0x8FFF {
let orig = unsafe { get_bits_corroded(bs, i as i32) };
let rewritten = get_bits(bs, i);
assert_eq!(orig, rewritten);
}
}
}

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