[Chicken-users] Fwd: Peeking N characters in string ports
Hi there, I'm reading from a (string) port and have a need to peek 2 characters inside without actually reading off the port (read-char). I believe procedures such as unread-char seen in other Schemes would solve my problem however, this isn't available in Chicken it seems. Would anyone have any suggestions? Thanks David ___ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users
Re: [Chicken-users] Fwd: Peeking N characters in string ports
Hi David, On Jan 11 2019, David Ireland wrote: Hi there, I'm reading from a (string) port and have a need to peek 2 characters inside without actually reading off the port (read-char). I believe procedures such as unread-char seen in other Schemes would solve my problem however, this isn't available in Chicken it seems. I do not recall that I ever used unread-char ever. I roughly recall that it usually can only "un-read" a single character. But that might be wrong. Would anyone have any suggestions? If you really need such a thing, my only suggestion would be to look into http://wiki.call-cc.org/man/5/Module%20(chicken%20port) make-input-port combined with make-concatenated-port and some tricks could do the trick. Best /Jörg ___ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users
Re: [Chicken-users] Fwd: Peeking N characters in string ports
Hello David, I've run into a similar problem when trying to detect magic bytes for unknown image formats. Most allowed figuring out the format by checking four bytes, one after three bytes. I've solved this problem by rethinking it a bit, first read in three bytes and compare, if it's not the three bytes format, read in one more byte and check the remaining signatures against the combination of the last three bytes and the fourth one. While this was slightly more verbose than an `unread-char` solution, it was still simple enough to understand. Vasilij signature.asc Description: PGP signature ___ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users
