- Reference manual
- SWI-Prolog C-library
- library(process): Create processes and redirect I/O
- library(filesex): Extended operations on files
- library(uid): User and group management on Unix systems
- library(syslog): Unix syslog interface
- library(socket): Network socket (TCP and UDP) library
- The stream_pool library
- library(uri): Process URIs
- CGI Support library
- Password encryption library
- library(uuid): Universally Unique Identifier (UUID) Library
- SHA* Secure Hash Algorithms
- library(md5): MD5 hashes
- library(hash_stream): Maintain a hash on a stream
- Memory files
- Time and alarm library
- library(unix): Unix specific operations
- Limiting process resources
- library(udp_broadcast): A UDP broadcast proxy
- library(prolog_stream): A stream with Prolog callbacks
- SWI-Prolog C-library
- See also
- In addition to this hash library, SWI-Prolog provides
library(sha)and hash functions through
library(crypto), part of the
This library defines a filter stream that maintains a hash of the data that passes through the stream. It can be used to compute the hash of input data while it is being processed. This is notably interesting if data is processed from a socket as it avoids the need for collecting the data first in a temporary file.
A typical processing sequence is illustrated below, where process/2 somehow processed the data and save_result/3 records the result as obtained from URL with content digest SHA256 its Result.
..., http_open(URL, In0, ), open_hash_stream(In0, In, [algorithm(sha256)]), process(In, Result), stream_hash(In, SHA256), close(In), save_result(URL, SHA256, Result)
This library can also be used to compute the hash for the content of a file. The advantage is that this code doesn't rely on external tools. It is considerably faster for short files, but considerably slower on large files because Prolog I/O is based on character streams rather than blocks.
file_hash(Algorithm, File, Hash) :- setup_call_cleanup( open(File, read, In0, [type(binary)]), setup_call_cleanup( open_hash_stream(In0, In, [ algorithm(Algorithm), close_parent(false) ]), ( setup_call_cleanup( open_null_stream(Null), copy_stream_data(In, Null), close(Null)), stream_hash(In, Hash) ), close(In)), close(In0)).
- [det]open_hash_stream(+OrgStream, -HashStream, +Options)
- Open a filter stream on OrgStream that maintains a hash. The
hash can be retrieved at any time using stream_hash/2.
- One of
sha512. Default is
true(default), closing the filter stream also closes the original (parent) stream.
- [det]stream_hash(+HashStream, -Digest:atom)
- Unify Digest with a hash for the bytes send to or read from HashStream. Note that the hash is computed on the stream buffers. If the stream is an output stream, it is first flushed and the Digest represents the hash at the current location. If the stream is an input stream the Digest represents the hash of the processed input including the already buffered data.