Availability::- use_module(library(sha)).(can be autoloaded)
 sha_hash_ctx(+OldContext, +Data, -NewContext, -Hash) is det
Hash is the SHA hash of Data. NewContext is the new SHA computation context, while OldContext is the old. OldContext may be produced by a prior invocation of either sha_new_ctx/3 or sha_hash_ctx/4 itself.

This predicate allows a SHA function to be computed in chunks, which may be important while working with Metalink (RFC 5854), BitTorrent or similar technologies, or simply with big files.

 sha_hash_ctx(+OldContext, +Data, -NewContext, -Hash) is det
Hash is the SHA hash of Data. NewContext is the new SHA computation context, while OldContext is the old. OldContext may be produced by a prior invocation of either sha_new_ctx/3 or sha_hash_ctx/4 itself.

This predicate allows a SHA function to be computed in chunks, which may be important while working with Metalink (RFC 5854), BitTorrent or similar technologies, or simply with big files.