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baff1af72d
The original Scheme implementation is astonishingly slow. Rewriting SHA-2 in C yields around x10000 speed boost for premade strings and bytevectors. For input ports this is alleviated to x100 boost. The implementation is divided into two parts: native computational backend and thin Scheme interface. It is tedious to properly do IO from C, so the Scheme code handles reading data from an input port and the C code performs actual computations on byte buffers (which is also used to handle strings and bytevectors directly). Scheme wrapper reads data in chunked manner with 'read-bytevector'. Currently, the chunk size has insignificant impact on performance as soon as it is bigger than 64. Also, using simply read-bytevector turned out to be 33% faster than preallocating a buffer and filling it with read-bytevector! One tricky part is how to get exact 32-bit integers in C89. We have no <inttypes.h> there, so instead we use <limits.h> to see whether we have a standard type with suitable boundaries. The other one is how to return a properly tagged sha_context from C. Chibi FFI currently cannot handle the case when a procedure returns either a C pointer (which needs to be boxed) or an exception (which should be left as is). To workaround this sexp_start_sha() receives a dummy argument of type sha_context; this makes Chibi FFI to put a proper type tag into 'self', which is then extracted in the C code. This commits adds a new shared library 'crypto$(SO)' with intent to keep there all native code of (chibi crypto) libraries. This allows to simply put any future native implementation of SHA-512 or MD5 in some md5.c and just include those files into crypto.stub.
24 lines
833 B
Scheme
24 lines
833 B
Scheme
;; sha2-native.scm -- SHA-2 digest algorithms native interface
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;; Copyright (c) 2015 Alexei Lozovsky. All rights reserved.
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;; BSD-style license: http://synthcode.com/license.txt
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(define (procees-sha-data! context src)
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(cond ((or (bytevector? src) (string? src))
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(add-sha-data! context src))
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((input-port? src)
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(let lp ((chunk (read-bytevector 1024 src)))
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(unless (eof-object? chunk)
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(add-sha-data! context chunk)
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(lp (read-bytevector 1024 src)))))
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(else
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(error "unknown digest source: " src))))
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(define (sha-224 src)
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(let ((context (start-sha type-sha-224)))
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(procees-sha-data! context src)
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(get-sha context)))
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(define (sha-256 src)
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(let ((context (start-sha type-sha-256)))
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(procees-sha-data! context src)
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(get-sha context)))
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