Emacs minor mode that allows viewing, editing and searching large files in batches. Batch size can be adjusted on the fly and bounds the memory that is to be used for operations on the file.
This is development version of the GNU ELPA vlf.el package. Here’s what it does in a nutshell:
- regular expression search on whole file (in constant memory determined by current batch size)
- chunk editing (if size has changed, saving is done in constant memory determined by current batch size)
- occur like indexing
- options to jump to beginning, end or arbitrary file chunk
- ability to jump/insert given number of batches at once
- newly added content is acknowledged if file has changed size meanwhile
- automatic scrolling of batches
- as VLF is minor mode, font locking and functionality of the respective major mode is also present
- VLF is added as an option when opening large files
GNU Emacs 23 and 24 are supported.
M-x vlf PATH-TO-FILE
Emacs’ Unicode support is leveraged so you’ll not see bare bytes but characters decoded as if file is normally opened. This holds for editing, search and indexing.
Regular Emacs integers are used, so if you use 32-bit Emacs without bignum support and have really huge file (with size beyond the maximum integer value), VLF will probably not quite work.
vlf-batch-size bounds the memory used for all operations.
You can control when vlf-mode is invoked or offered as choice with the vlf-application customization option. By default it will offer VLF when opening large files. There are also options to never use it (you can still call vlf command explicitly); to use it without asking for large files or to invoke it on all files. Here’s example setup such that vlf-mode automatically launches for large files:
(custom-set-variables '(vlf-application 'dont-ask))
All VLF operations are grouped under the C-c C-v prefix by default. Here’s example how to add another prefix (C-x v):
(eval-after-load "vlf" '(define-key vlf-prefix-map "\C-xv" vlf-mode-map))
C-c C-v + and C-c C-v - control current batch size by factors of 2.
You can also set by hand local variable vlf-batch-size and then refresh with C-c C-v g.
Scrolling automatically triggers moving to previous or next chunk at the beginning or end respectively of the current one.
C-c C-v n and C-c C-v p move batch by batch. With positive prefix argument they move prefix number of batches. With negative - append prefix number of batches.
C-c C-v SPC displays batch starting from current point.
C-c C-v [ and C-c C-v ] take you to the beginning and end of file respectively.
C-c C-v j jumps to given chunk. To see where you are in file and how many chunks there are (using the current batch size), look at the parenthesized part of the buffer name, batch size is also indicated at the end.
Intelligent continuous recenter around point in current buffer can be enabled with:
M-x vlf-start-following
You are asked for number of idle seconds interval for automatic update. To cancel following invoke M-x vlf-stop-following.
C-c C-v s and C-c C-v r search forward and backward respectively over the whole file. This is done batch by batch so if you have really huge file - you’d better set somewhat bigger batch size beforehand.
C-c C-v o builds index for given regular expression just like M-x occur. It does this batch by batch over the whole file. Note that even if you prematurely stop it with C-g, it will still show index of what’s found so far.
C-c C-v l jumps to given line in file. This is done by searching from the beginning, so again the bigger current batch size, the quicker. With negative argument, lines are counted from the end of file.
If editing doesn’t change size of the chunk, only this chunk is saved. Otherwise the remaining part of the file is adjusted batch by batch, so again you’d better have bigger current batch size.