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Auto merge of #30660 - nagisa:rollup, r=steveklabnik
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,162 @@ | ||
| // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT | ||
| // file at the top-level directory of this distribution and at | ||
| // http://rust-lang.org/COPYRIGHT. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | ||
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | ||
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | ||
| // option. This file may not be copied, modified, or distributed | ||
| // except according to those terms. | ||
|
|
||
| #[inline] | ||
| pub fn write_to_vec(vec: &mut Vec<u8>, position: &mut usize, byte: u8) | ||
| { | ||
| if *position == vec.len() { | ||
| vec.push(byte); | ||
| } else { | ||
| vec[*position] = byte; | ||
| } | ||
|
|
||
| *position += 1; | ||
| } | ||
|
|
||
| pub fn write_unsigned_leb128(out: &mut Vec<u8>, | ||
| start_position: usize, | ||
| mut value: u64) | ||
| -> usize { | ||
| let mut position = start_position; | ||
| loop | ||
| { | ||
| let mut byte = (value & 0x7F) as u8; | ||
| value >>= 7; | ||
| if value != 0 { | ||
| byte |= 0x80; | ||
| } | ||
|
|
||
| write_to_vec(out, &mut position, byte); | ||
|
|
||
| if value == 0 { | ||
| break; | ||
| } | ||
| } | ||
|
|
||
| return position - start_position; | ||
| } | ||
|
|
||
| pub fn read_unsigned_leb128(data: &[u8], | ||
| start_position: usize) | ||
| -> (u64, usize) { | ||
| let mut result = 0; | ||
| let mut shift = 0; | ||
| let mut position = start_position; | ||
| loop { | ||
| let byte = data[position]; | ||
| position += 1; | ||
| result |= ((byte & 0x7F) as u64) << shift; | ||
| if (byte & 0x80) == 0 { | ||
| break; | ||
| } | ||
| shift += 7; | ||
| } | ||
|
|
||
| (result, position - start_position) | ||
| } | ||
|
|
||
|
|
||
| pub fn write_signed_leb128(out: &mut Vec<u8>, | ||
| start_position: usize, | ||
| mut value: i64) -> usize { | ||
| let mut position = start_position; | ||
|
|
||
| loop { | ||
| let mut byte = (value as u8) & 0x7f; | ||
| value >>= 7; | ||
| let more = !((((value == 0 ) && ((byte & 0x40) == 0)) || | ||
| ((value == -1) && ((byte & 0x40) != 0)))); | ||
| if more { | ||
| byte |= 0x80; // Mark this byte to show that more bytes will follow. | ||
| } | ||
|
|
||
| write_to_vec(out, &mut position, byte); | ||
|
|
||
| if !more { | ||
| break; | ||
| } | ||
| } | ||
|
|
||
| return position - start_position; | ||
| } | ||
|
|
||
| pub fn read_signed_leb128(data: &[u8], | ||
| start_position: usize) | ||
| -> (i64, usize) { | ||
| let mut result = 0; | ||
| let mut shift = 0; | ||
| let mut position = start_position; | ||
| let mut byte; | ||
|
|
||
| loop { | ||
| byte = data[position]; | ||
| position += 1; | ||
| result |= ((byte & 0x7F) as i64) << shift; | ||
| shift += 7; | ||
|
|
||
| if (byte & 0x80) == 0 { | ||
| break; | ||
| } | ||
| } | ||
|
|
||
| if (shift < 64) && ((byte & 0x40) != 0) { | ||
| /* sign extend */ | ||
| result |= -(1i64 << shift); | ||
| } | ||
|
|
||
| (result, position - start_position) | ||
| } | ||
|
|
||
| #[test] | ||
| fn test_unsigned_leb128() { | ||
| let mut stream = Vec::with_capacity(10000); | ||
|
|
||
| for x in 0..62 { | ||
| let pos = stream.len(); | ||
| let bytes_written = write_unsigned_leb128(&mut stream, pos, 3 << x); | ||
| assert_eq!(stream.len(), pos + bytes_written); | ||
| } | ||
|
|
||
| let mut position = 0; | ||
| for x in 0..62 { | ||
| let expected = 3 << x; | ||
| let (actual, bytes_read) = read_unsigned_leb128(&stream, position); | ||
| assert_eq!(expected, actual); | ||
| position += bytes_read; | ||
| } | ||
| assert_eq!(stream.len(), position); | ||
| } | ||
|
|
||
| #[test] | ||
| fn test_signed_leb128() { | ||
| let mut values = Vec::new(); | ||
|
|
||
| let mut i = -500; | ||
| while i < 500 { | ||
| values.push(i * 123457i64); | ||
| i += 1; | ||
| } | ||
|
|
||
| let mut stream = Vec::new(); | ||
|
|
||
| for &x in &values { | ||
| let pos = stream.len(); | ||
| let bytes_written = write_signed_leb128(&mut stream, pos, x); | ||
| assert_eq!(stream.len(), pos + bytes_written); | ||
| } | ||
|
|
||
| let mut pos = 0; | ||
| for &x in &values { | ||
| let (value, bytes_read) = read_signed_leb128(&mut stream, pos); | ||
| pos += bytes_read; | ||
| assert_eq!(x, value); | ||
| } | ||
| assert_eq!(pos, stream.len()); | ||
| } |
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