openethereum/util/src/snappy.rs

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// Copyright 2015-2017 Parity Technologies (UK) Ltd.
// This file is part of Parity.
// Parity is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// Parity is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with Parity. If not, see <http://www.gnu.org/licenses/>.
//! Snappy compression bindings.
use std::fmt;
use libc::{c_char, c_int, size_t};
const SNAPPY_OK: c_int = 0;
const SNAPPY_INVALID_INPUT: c_int = 1;
const SNAPPY_BUFFER_TOO_SMALL: c_int = 2;
#[link(name = "snappy")]
extern {
fn snappy_compress(
input: *const c_char,
input_len: size_t,
compressed: *mut c_char,
compressed_len: *mut size_t
) -> c_int;
fn snappy_max_compressed_length(source_len: size_t) -> size_t;
fn snappy_uncompress(
compressed: *const c_char,
compressed_len: size_t,
uncompressed: *mut c_char,
uncompressed_len: *mut size_t,
) -> c_int;
fn snappy_uncompressed_length(
compressed: *const c_char,
compressed_len: size_t,
result: *mut size_t,
) -> c_int;
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fn snappy_validate_compressed_buffer(
compressed: *const c_char,
compressed_len: size_t,
) -> c_int;
}
/// Attempted to decompress an uncompressed buffer.
#[derive(Debug)]
pub struct InvalidInput;
impl fmt::Display for InvalidInput {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "Attempted snappy decompression with invalid input")
}
}
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/// The maximum compressed length given a size.
pub fn max_compressed_len(len: usize) -> usize {
unsafe { snappy_max_compressed_length(len as size_t) as usize }
}
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/// How large the given data will be when decompressed.
pub fn decompressed_len(compressed: &[u8]) -> Result<usize, InvalidInput> {
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let mut size: size_t = 0;
let len = compressed.len() as size_t;
let status = unsafe { snappy_uncompressed_length(compressed.as_ptr() as *const c_char, len, &mut size) };
if status == SNAPPY_INVALID_INPUT {
Err(InvalidInput)
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} else {
Ok(size)
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}
}
/// Compress a buffer using snappy.
pub fn compress(input: &[u8]) -> Vec<u8> {
let mut buf = Vec::new();
compress_into(input, &mut buf);
buf
}
/// Compress a buffer using snappy, writing the result into
/// the given output buffer, growing it if necessary.
/// Otherwise, returns the length of the compressed data.
pub fn compress_into(input: &[u8], output: &mut Vec<u8>) -> usize {
let mut len = max_compressed_len(input.len());
if output.len() < len {
output.resize(len, 0);
}
let status = unsafe {
snappy_compress(
input.as_ptr() as *const c_char,
input.len() as size_t,
output.as_mut_ptr() as *mut c_char,
&mut len as &mut size_t,
)
};
match status {
SNAPPY_OK => len,
SNAPPY_INVALID_INPUT => panic!("snappy compression has no concept of invalid input"),
SNAPPY_BUFFER_TOO_SMALL => panic!("buffer cannot be too small, the capacity was just ensured."),
_ => panic!("snappy returned unspecified status"),
}
}
/// Decompress a buffer using snappy. Will return an error if the buffer is not snappy-compressed.
pub fn decompress(input: &[u8]) -> Result<Vec<u8>, InvalidInput> {
let mut v = Vec::new();
decompress_into(input, &mut v).map(|_| v)
}
/// Decompress a buffer using snappy, writing the result into
/// the given output buffer, growing it if necessary.
/// Will error if the input buffer is not snappy-compressed.
/// Otherwise, returns the length of the decompressed data.
pub fn decompress_into(input: &[u8], output: &mut Vec<u8>) -> Result<usize, InvalidInput> {
let mut len = decompressed_len(input)?;
if output.len() < len {
output.resize(len, 0);
}
let status = unsafe {
snappy_uncompress(
input.as_ptr() as *const c_char,
input.len() as size_t,
output.as_mut_ptr() as *mut c_char,
&mut len as &mut size_t,
)
};
match status {
SNAPPY_OK => Ok(len as usize),
SNAPPY_INVALID_INPUT => Err(InvalidInput),
SNAPPY_BUFFER_TOO_SMALL => panic!("buffer cannot be too small, size was just set to large enough."),
_ => panic!("snappy returned unspecified status"),
}
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}
/// Validate a compressed buffer. True if valid, false if not.
pub fn validate_compressed_buffer(input: &[u8]) -> bool {
let status = unsafe { snappy_validate_compressed_buffer(input.as_ptr() as *const c_char, input.len() as size_t )};
status == SNAPPY_OK
}