Tony wrote:
> I see that since Vim 8.1.765, there is a new type, the Blob. But what > is a Blob, exactly? What is it good for? I gather from the help that a > Blob is defined as any string of 0 or more hex bytes, including null > bytes if desired, and that a Blob can be created by assigning it > either a Blob literal (0z or 0Z followed by any even number of hex > digits) or the value of another Blob. > > :echo displays a Blob as a List of numbers in hex, e.g. ":echo > 0z00112233445566778899AABBCCDDEEFF" (without the double quotes) gives > [0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xAA, > 0xBB, 0xCC, 0xDD, 0xEE, 0xFF] but a Blob cannot be treated as either a > List or a String: ":echo ['Mary', 'had', 'a', 'little', 'lamb'] + > 0z12345678" gives E745: Using a List as a Number (sic) while "echo > 'Mary had a little lamb' . 0z12345678" gives E976: Using a Blob as a > String. But ":echo 0z01234567 + 0z89ABCDEF" gives [0x01, 0x23, 0x45, > 0x67, 0x89, 0xAB, 0xCD, 0xEF]. > > I have read somewhere in the help that blob[n] is the, er, (n-1)th > byte I think, of the Blob, but experiment shows that it is returned as > a Number, not a Blob; and that blob[i:j] returns a Blob containing all > bytes from blob[i] to blob[j] inclusive, and experiment shows that in > this case the result is indeed a Blob; but neither blob + blob nor > blob[i] with a single index are covered (yet) under :h > expression-syntax and its subtags AFAICT. So what other operations are > possible? Ah yes: Blobs can be tested for equality (i.e. :echo > 0zabcdef == 0zABCDEF returns 1) and for emptyness (:echo empty(0z) > returns 1 but :echo empty(0z00) returns 0) but not for comparison > (:echo 0z123456 < 0zABCDEF returns E978: Invalid operation for Blob). > What else? The main reason for supporting a Blob is to deal with raw data. That can be an image, sound file, etc. Normally these would only be moved around. E.g., read it from a file and send it on a channel. In some cases it is useful to manupliate the Blob, e.g. concatenate or split it up. The use of this is limited. However, since a Blob mostly behaves as a List of bytes, Yasuhiro added several operations that are available for List. I have to admit that it's quite a bit of code for something that isn't going to be used much. But when a plugin needs to manipulate binary data, it's essintial. -- hundred-and-one symptoms of being an internet addict: 189. You put your e-mail address in the upper left-hand corner of envelopes. /// Bram Moolenaar -- b...@moolenaar.net -- http://www.Moolenaar.net \\\ /// sponsor Vim, vote for features -- http://www.Vim.org/sponsor/ \\\ \\\ an exciting new programming language -- http://www.Zimbu.org /// \\\ help me help AIDS victims -- http://ICCF-Holland.org /// -- -- You received this message from the "vim_use" maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php --- You received this message because you are subscribed to the Google Groups "vim_use" group. To unsubscribe from this group and stop receiving emails from it, send an email to vim_use+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
