1 gzip Compression and File Creation
2 gzip Decompression
3 zip File Creation
4 tar File Creation
5 MD5 Message Digest
6 GIF File Writing
Index
On this page:
gzip
gzip-through-ports
deflate
Version: 4.0.2

 

1 gzip Compression and File Creation

 (require file/gzip)

The file/gzip library provides utilities to create archive files in gzip format, or simply to compress data using the pkzip “deflate” method.

(gzip in-file [out-file])  void?

  in-file : path-string?

  out-file : path-string? = (string-append in-file ".gz")

Compresses data to the same format as the gzip utility, writing the compressed data directly to a file. The in-file argument is the name of the file to compress. If the file named by out-file exists, it will be overwritten.

(gzip-through-ports

 

in

 

 

 

 

 

 

out

 

 

 

 

 

 

orig-filename

 

 

 

 

 

 

timestamp)

 

 

void?

  in : input-port?

  out : output-port?

  orig-filename : (or/c string? false/c)

  timestamp : exact-integer?

Reads the port in for data and compresses it to out, outputting the same format as the gzip utility. The orig-filename string is embedded in this output; orig-filename can be #f to omit the filename from the compressed stream. The timestamp number is also embedded in the output stream, as the modification date of the original file (in Unix seconds, as file-or-directory-modify-seconds would report under Unix).

(deflate in out)

 

 

exact-nonnegative-integer?

exact-nonnegative-integer?

exact-nonnegative-integer?

  in : input-port?

  out : output-port?

Writes pkzip-format “deflated” data to the port out, compressing data from the port in. The data in a file created by gzip uses this format (preceded with header information).

The result is three values: the number of bytes read from in, the number of bytes written to out, and a cyclic redundancy check (CRC) value for the input.