Racket

libbrotli🔗ℹ

Racket bindings to Google’s Brotli compression library.

1 One-Shot Compression🔗ℹ

procedure
(brotli-compress src
[ quality
#:window window
#:mode mode
#:lgblock lgblock
#:dictionary dictionary]) → bytes?
  src : bytes?
  quality : quality/c = BROTLI_DEFAULT_QUALITY
  window : window/c = BROTLI_DEFAULT_WINDOW
  mode : mode/c = BROTLI_MODE_GENERIC
  lgblock : lgblock/c = 0
  dictionary : bytes? = #""

Compresses src and returns the compressed bytes.

(require libbrotli)

(define compressed (brotli-compress #"hello world"))
(brotli-decompress compressed)

procedure
(brotli-decompress src
[ max-decompressed-size
#:dictionary dictionary]) → bytes?
  src : bytes?
  max-decompressed-size : (or/c #f exact-positive-integer?) = #f
  dictionary : bytes? = #""

Decompresses src and returns the original bytes. If max-decompressed-size is not #f, limits the output size to prevent decompression bombs.

value
quality/c : flat-contract?

Integer in the range 0 to 11.

value
BROTLI_DEFAULT_QUALITY : exact-nonnegative-integer? = 11

Default compression quality for one-shot functions.

value
BROTLI_MIN_QUALITY : exact-nonnegative-integer? = 0

Minimum compression quality (fastest, lowest ratio).

value
BROTLI_MAX_QUALITY : exact-nonnegative-integer? = 11

Maximum compression quality (slowest, highest ratio).

value
window/c : flat-contract?

Integer in the range 10 to 24.

value
BROTLI_DEFAULT_WINDOW : exact-nonnegative-integer? = 22

Default sliding window size in bits.

value
BROTLI_MIN_WINDOW_BITS : exact-nonnegative-integer? = 10

Minimum window size (1 KB).

value
BROTLI_MAX_WINDOW_BITS : exact-nonnegative-integer? = 24

Maximum window size (16 MB).

value
mode/c : flat-contract?

One of 0, 1, or 2 (corresponding to BROTLI_MODE_GENERIC, BROTLI_MODE_TEXT, and BROTLI_MODE_FONT).

value
BROTLI_MODE_GENERIC : exact-nonnegative-integer? = 0

Default compression mode. Works for any input.

value
BROTLI_MODE_TEXT : exact-nonnegative-integer? = 1

Compression mode optimized for UTF-8 text.

value
BROTLI_MODE_FONT : exact-nonnegative-integer? = 2

Compression mode optimized for WOFF 2.0 fonts.

value
lgblock/c : flat-contract?

Either 0 (automatic) or an integer in the range 16 to 24.

2 Buffer Compression🔗ℹ

procedure
(brotli-compress! src
dst
[ quality
#:window window
#:mode mode
#:lgblock lgblock
#:dictionary dictionary])
→ exact-nonnegative-integer?
  src : bytes?
  dst : bytes?
  quality : quality/c = BROTLI_DEFAULT_QUALITY
  window : window/c = BROTLI_DEFAULT_WINDOW
  mode : mode/c = BROTLI_MODE_GENERIC
  lgblock : lgblock/c = 0
  dictionary : bytes? = #""

Compresses src into the pre-allocated buffer dst. Returns the number of bytes written. Raises an error if dst is too small.

procedure
(brotli-decompress! src
dst
[ #:dictionary dictionary])
→ exact-nonnegative-integer?
  src : bytes?
  dst : bytes?
  dictionary : bytes? = #""

Decompresses src into the pre-allocated buffer dst. Returns the number of bytes written. Raises an error if dst is too small.

3 Streaming Ports🔗ℹ

procedure
(open-brotli-output out
[ #:quality quality
#:window window
#:mode mode
#:lgblock lgblock
#:dictionary dictionary
#:close? close?
#:name name]) → output-port?
  out : output-port?
  quality : quality/c = 6
  window : window/c = BROTLI_DEFAULT_WINDOW
  mode : mode/c = BROTLI_MODE_GENERIC
  lgblock : lgblock/c = 0
  dictionary : bytes? = #""
  close? : boolean? = #t
  name : symbol? = 'brotli-output

Returns an output port that compresses data written to it and forwards the compressed bytes to out. Closing the returned port flushes the remaining compressed data. If close? is #t, closing also closes out.

Note: the default quality for streaming is 6 (not 11), which is a better tradeoff for real-time use.

(require libbrotli)

(define out (open-output-bytes))
(define brotli-out (open-brotli-output out))
(write-bytes #"hello world" brotli-out)
(close-output-port brotli-out)
(brotli-decompress (get-output-bytes out))

procedure
(open-brotli-input in
[ #:dictionary dictionary
#:close? close?
#:name name]) → input-port?
  in : input-port?
  dictionary : bytes? = #""
  close? : boolean? = #t
  name : symbol? = 'brotli-input

Returns an input port that decompresses Brotli-encoded data read from in. If close? is #t, closing the returned port also closes in.