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Use a faster deflate setting #37298

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merged 2 commits into from
Oct 22, 2016
Merged

Use a faster deflate setting #37298

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feefe77
Remove `{in,de}flate_bytes_zlib`.
nnethercote Oct 20, 2016
94771a1
Use fast decompression in `deflate_bytes`.
nnethercote Oct 20, 2016
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35 changes: 10 additions & 25 deletions src/libflate/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -94,11 +94,14 @@ extern "C" {
-> *mut c_void;
}

const LZ_NORM: c_int = 0x80; // LZ with 128 probes, "normal"
const TINFL_FLAG_PARSE_ZLIB_HEADER: c_int = 0x1; // parse zlib header and adler32 checksum
const TDEFL_WRITE_ZLIB_HEADER: c_int = 0x01000; // write zlib header and adler32 checksum
const LZ_FAST: c_int = 0x01; // LZ with 1 probe, "fast"
const TDEFL_GREEDY_PARSING_FLAG: c_int = 0x04000; // fast greedy parsing instead of lazy parsing

fn deflate_bytes_internal(bytes: &[u8], flags: c_int) -> Bytes {
/// Compress a buffer without writing any sort of header on the output. Fast
/// compression is used because it is almost twice as fast as default
/// compression and the compression ratio is only marginally worse.
pub fn deflate_bytes(bytes: &[u8]) -> Bytes {
let flags = LZ_FAST | TDEFL_GREEDY_PARSING_FLAG;
unsafe {
let mut outsz: size_t = 0;
let res = tdefl_compress_mem_to_heap(bytes.as_ptr() as *const _,
Expand All @@ -113,17 +116,9 @@ fn deflate_bytes_internal(bytes: &[u8], flags: c_int) -> Bytes {
}
}

/// Compress a buffer, without writing any sort of header on the output.
pub fn deflate_bytes(bytes: &[u8]) -> Bytes {
deflate_bytes_internal(bytes, LZ_NORM)
}

/// Compress a buffer, using a header that zlib can understand.
pub fn deflate_bytes_zlib(bytes: &[u8]) -> Bytes {
deflate_bytes_internal(bytes, LZ_NORM | TDEFL_WRITE_ZLIB_HEADER)
}

fn inflate_bytes_internal(bytes: &[u8], flags: c_int) -> Result<Bytes, Error> {
/// Decompress a buffer without parsing any sort of header on the input.
pub fn inflate_bytes(bytes: &[u8]) -> Result<Bytes, Error> {
let flags = 0;
unsafe {
let mut outsz: size_t = 0;
let res = tinfl_decompress_mem_to_heap(bytes.as_ptr() as *const _,
Expand All @@ -141,16 +136,6 @@ fn inflate_bytes_internal(bytes: &[u8], flags: c_int) -> Result<Bytes, Error> {
}
}

/// Decompress a buffer, without parsing any sort of header on the input.
pub fn inflate_bytes(bytes: &[u8]) -> Result<Bytes, Error> {
inflate_bytes_internal(bytes, 0)
}

/// Decompress a buffer that starts with a zlib header.
pub fn inflate_bytes_zlib(bytes: &[u8]) -> Result<Bytes, Error> {
inflate_bytes_internal(bytes, TINFL_FLAG_PARSE_ZLIB_HEADER)
}

#[cfg(test)]
mod tests {
#![allow(deprecated)]
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