Compression

Compress and decompress data using gzip, deflate, zlib, brotli, and zstd algorithms.

Loading

local compress = require("compress")

GZIP

Most widely supported format (RFC 1952).

Compress {id="gzip-compress"}

-- Compress for HTTP response
local body = json.encode(large_response)
local compressed, err = compress.gzip.encode(body)
if err then
    return nil, err
end

-- Set Content-Encoding header
res:set_header("Content-Encoding", "gzip")
res:write(compressed)

-- Maximum compression for storage
local archived = compress.gzip.encode(data, {level = 9})

-- Fast compression for real-time
local fast = compress.gzip.encode(data, {level = 1})

Options {id="gzip-compress-options"}

Returns: string, error

Decompress {id="gzip-decompress"}

-- Decompress HTTP request
local content_encoding = req:header("Content-Encoding")
if content_encoding == "gzip" then
    local body = req:body()
    local decompressed, err = compress.gzip.decode(body)
    if err then
        return nil, errors.new("INVALID", "Invalid gzip data")
    end
    body = decompressed
end

-- Decompress with size limit (prevent zip bombs)
local decompressed, err = compress.gzip.decode(data, {max_size = 10 * 1024 * 1024})
if err then
    return nil, errors.new("INVALID", "Decompressed size exceeds 10MB limit")
end

Options {id="gzip-decompress-options"}

Returns: string, error

Brotli

Best compression ratio for text (RFC 7932).

Compress {id="brotli-compress"}

-- Best for static assets and text content
local compressed = compress.brotli.encode(html_content, {level = 11})

-- Cache compressed assets
cache:set("static:" .. hash, compressed)

-- Moderate compression for API responses
local compressed = compress.brotli.encode(json_data, {level = 4})

Options {id="brotli-compress-options"}

Returns: string, error

Decompress {id="brotli-decompress"}

local decompressed, err = compress.brotli.decode(compressed_data)
if err then
    return nil, err
end

-- With size limit
local decompressed = compress.brotli.decode(data, {max_size = 50 * 1024 * 1024})

Options {id="brotli-decompress-options"}

Returns: string, error

Zstandard

Fast compression with good ratios (RFC 8878).

Compress {id="zstd-compress"}

-- Good balance of speed and ratio
local compressed = compress.zstd.encode(binary_data)

-- Higher compression for archival
local archived = compress.zstd.encode(data, {level = 19})

-- Fast mode for real-time streaming
local fast = compress.zstd.encode(data, {level = 1})

Options {id="zstd-compress-options"}

Returns: string, error

Decompress {id="zstd-decompress"}

local decompressed, err = compress.zstd.decode(compressed_data)
if err then
    return nil, err
end

Options {id="zstd-decompress-options"}

Returns: string, error

Deflate

Raw DEFLATE compression (RFC 1951). Used internally by other formats.

Compress {id="deflate-compress"}

local compressed = compress.deflate.encode(data, {level = 6})

Options {id="deflate-compress-options"}

Returns: string, error

Decompress {id="deflate-decompress"}

local decompressed = compress.deflate.decode(compressed)

Options {id="deflate-decompress-options"}

Returns: string, error

Zlib

DEFLATE with header and checksum (RFC 1950).

Compress {id="zlib-compress"}

local compressed = compress.zlib.encode(data, {level = 6})

Options {id="zlib-compress-options"}

Returns: string, error

Decompress {id="zlib-decompress"}

local decompressed = compress.zlib.decode(compressed)

Options {id="zlib-decompress-options"}

Returns: string, error

Choosing an Algorithm

-- HTTP response based on Accept-Encoding
local accept = req:header("Accept-Encoding") or ""
local body = json.encode(response_data)

if accept:find("br") then
    res:set_header("Content-Encoding", "br")
    res:write(compress.brotli.encode(body))
elseif accept:find("gzip") then
    res:set_header("Content-Encoding", "gzip")
    res:write(compress.gzip.encode(body))
else
    res:write(body)
end

Errors

See Error Handling for working with errors.