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At Mon, 27 Sep 2004 22:03:48 -0700, Dale Jordan wrote: > > A number of Schemes (Scheme48 and Chicken, at least) support > byte-vectors for doing aggregate binary io. This seems to satisfy most > needs for doing something beyond simple scalar io, while still allowing > the application to perform whatever interpretation is necessary. > > I suppose some might consider it onerous to require implementing such a > data type for this SRFI, but I consider byte-vectors extraordinarily useful. Would these be equivalent to SRFI-4 u8vectors and SRFI-47 au8 arrays (which have the comment "Byte arrays can be implemented independently and distinctly from strings")? I did consider utilities to read/write directly to/from these data types, but came across a few stumbling blocks. First, there are two competing SRFIs. Second there is the question of interface - do you provide separate procedures on each type: (read-u8block! u8vec port) ; fill u8vec from port, SRFI-4 style (read-u16-block! u16vec port) ... or do generic dispatch on type: (read-array! u8vec port) ; fill u8vec from port, SRFI-47 style With generic dispatch the reference implementation becomes slow and non-extensible. This would still be my preference, but it's enough added complexity that I would rather it go in a separate SRFI. Basically all I wanted for SRFI-56 was to make binary I/O *possible* via 4 primitives and throw in some useful library procedures that wouldn't really be controversial. Regardless, this feature is orthogonal to the current debate which is that *if* you allow binary operations (including potentially operations on byte arrays), can you perform said operations on all ports and if not how do you designate for a given port if it supports binary vs character operations? I'm sorry for the delay, I really haven't come up with any better ideas, so when I release an updated version (RSN) the API will become (with hopefully better wording): ;; new port predicates, not necessarily disjoint (binary-port? port) (character-port? port) ;; new procedures such that the port generated is guaranteed to ;; return #t for BINARY-PORT?, whereas the R5RS equivalents always ;; return #t for CHARACTER-PORT?. (open-binary-input-file file) (open-binary-output-file file) (call-with-input-binary-file file proc) (call-with-output-binary-file file proc) (with-input-from-binary-file file thunk) (with-output-to-binary-file file thunk) READ-CHAR, WRITE-CHAR, READ, WRITE, DISPLAY and all other R5RS I/O procedures are guaranteed to be allowed on any port for which CHARACTER-PORT? returns #t, assuming all other qualifications are met (i.e. you're not trying to read from an OUTPUT-PORT?). READ-BYTE, WRITE-BYTE, PEEK-BYTE and BYTE-READY? plus the library procedures provided in SRFI-56 are guaranteed to be allowed on any port for which BINARY-PORT? returns #t, assuming other qualifications are met. String ports are guaranteed to return #t for at least CHARACTER-PORT?. Implementations are free and encouraged to make no distinction between the port types, while program authors are encouraged to use the *-binary-* equivalents for port creation when they don't intend to perform any character-level operations, both for portability and as a reminder of the purpose of the port. When both binary and character operations are to be used, the R5RS procedures are preferred. -- Alex