You can use the following function to replace the text of one buffer
with the text of another buffer:
-@deffn Command replace-buffer-contents source
+@deffn Command replace-buffer-contents source &optional max-secs max-costs
This function replaces the accessible portion of the current buffer
with the accessible portion of the buffer @var{source}. @var{source}
may either be a buffer object or the name of a buffer. When
@code{replace-buffer-contents} succeeds, the text of the accessible
portion of the current buffer will be equal to the text of the
-accessible portion of the @var{source} buffer. This function attempts
-to keep point, markers, text properties, and overlays in the current
-buffer intact. One potential case where this behavior is useful is
-external code formatting programs: they typically write the
-reformatted text into a temporary buffer or file, and using
-@code{delete-region} and @code{insert-buffer-substring} would destroy
-these properties. However, the latter combination is typically
-faster. @xref{Deletion}, and @ref{Insertion}.
+accessible portion of the @var{source} buffer.
+
+This function attempts to keep point, markers, text properties, and
+overlays in the current buffer intact. One potential case where this
+behavior is useful is external code formatting programs: they
+typically write the reformatted text into a temporary buffer or file,
+and using @code{delete-region} and @code{insert-buffer-substring}
+would destroy these properties. However, the latter combination is
+typically faster (@xref{Deletion}, and @ref{Insertion}).
+
+For its working, @code{replace-buffer-contents} needs to compare the
+contents of the original buffer with that of @code{source} which is a
+costly operation if the buffers are huge and there is a high number of
+differences between them. In order to keep
+@code{replace-buffer-contents}'s runtime in bounds, it has two
+optional arguments.
+
+@code{max-secs} defines a hard boundary in terms of seconds. If given
+and exceeded, it will fall back to @code{delete-region} and
+@code{insert-buffer-substring}.
+
+@code{max-costs} defines the quality of the difference computation.
+If the actual costs exceed this limit, heuristics are used to provide
+a faster but suboptimal solution. The default value is 1000000.
+
+@code{replace-buffer-contents} returns t if a non-destructive
+replacement could be performed. Otherwise, i.e., if MAX-SECS was
+exceeded, it returns nil.
+@end deffn
+
+@defun Command replace-region-contents beg end replace-fn &optional max-secs max-costs
+This function replaces the region between @code{beg} and @code{end}
+using the given @code{replace-fn}. The function @code{replace-fn} is
+run in the current buffer narrowed to the specified region and it
+should return either a string or a buffer replacing the region.
+
+The replacement is performed using @code{replace-buffer-contents}
+which also describes the @code{max-secs} and @code{max-costs}
+arguments and the return value.
+
+Note: If the replacement is a string, it will be placed in a temporary
+buffer so that @code{replace-buffer-contents} can operate on it.
+Therefore, if you already have the replacement in a buffer, it makes
+no sense to convert it to a string using @code{buffer-substring} or
+similar.
@end deffn
@node Decompression
'make-network-process' now uses the correct loopback address when
asked to use :host 'local and :family 'ipv6.
++++
+** The new function `replace-region-contents' replaces the current
+region using a given replacement-function in a non-destructive manner
+(in terms of `replace-buffer-contents').
+
++++
+** The command `replace-buffer-contents' now has two optional
+arguments mitigating performance issues when operating on huge
+buffers.
+
\f
* Changes in Specialized Modes and Packages in Emacs 27.1
(substring string 0 (- (length string) (length suffix)))
string))
+(defun replace-region-contents (beg end replace-fn
+ &optional max-secs max-costs)
+ "Replace the region between BEG and END using REPLACE-FN.
+REPLACE-FN runs on the current buffer narrowed to the region. It
+should return either a string or a buffer replacing the region.
+
+The replacement is performed using `replace-buffer-contents'
+which also describes the MAX-SECS and MAX-COSTS arguments and the
+return value.
+
+Note: If the replacement is a string, it'll be placed in a
+temporary buffer so that `replace-buffer-contents' can operate on
+it. Therefore, if you already have the replacement in a buffer,
+it makes no sense to convert it to a string using
+`buffer-substring' or similar."
+ (save-excursion
+ (save-restriction
+ (narrow-to-region beg end)
+ (goto-char (point-min))
+ (let ((repl (funcall replace-fn)))
+ (if (bufferp repl)
+ (replace-buffer-contents repl max-secs max-costs)
+ (let ((source-buffer (current-buffer)))
+ (with-temp-buffer
+ (insert repl)
+ (let ((tmp-buffer (current-buffer)))
+ (set-buffer source-buffer)
+ (replace-buffer-contents tmp-buffer max-secs max-costs)))))))))
+
(provide 'subr-x)
;;; subr-x.el ends here
;; 2008-02-21 - Installed in GNU Emacs.
;; 2011-10-17 - Patch `json-alist-p' and `json-plist-p' to avoid recursion -tzz
;; 2012-10-25 - Added pretty-printed reformatting -Ryan Crum (ryan@ryancrum.org)
+;; 2019-02-02 - Pretty-printing now uses replace-region-contents and support for
+;; minimization -tsdh
;;; Code:
(require 'map)
+(require 'subr-x)
;; Parameters
(interactive "P")
(json-pretty-print (point-min) (point-max) minimize))
+(defvar json-pretty-print-max-secs 2.0
+ "Maximum time for `json-pretty-print's comparison.
+The function `json-pretty-print' uses `replace-region-contents'
+(which see) passing the value of this variable as argument
+MAX-SECS.")
+
(defun json-pretty-print (begin end &optional minimize)
"Pretty-print selected region.
With prefix argument MINIMIZE, minimize it instead."
(json-object-type 'alist))
(replace-region-contents
begin end
- (lambda () (json-encode (json-read))))))
+ (lambda () (json-encode (json-read)))
+ json-pretty-print-max-secs
+ ;; FIXME: What's a good value here? Can we use something better,
+ ;; e.g., by deriving a value from the size of the region?
+ 64)))
(defun json-pretty-print-buffer-ordered (&optional minimize)
"Pretty-print current buffer with object keys ordered.
;; for discoverability:
(defalias 'flatten-list 'flatten-tree)
-(defun replace-region-contents (beg end replace-fn)
- "Replace the region between BEG and END using REPLACE-FN.
-REPLACE-FN runs on the current buffer narrowed to the region. It
-should return either a string or a buffer replacing the region.
-
-The replacement is performed using `replace-buffer-contents'.
-
-Note: If the replacement is a string, it'll be placed in a
-temporary buffer so that `replace-buffer-contents' can operate on
-it. Therefore, if you already have the replacement in a buffer,
-it makes no sense to convert it to a string using
-`buffer-substring' or similar."
- (save-excursion
- (save-restriction
- (narrow-to-region beg end)
- (goto-char (point-min))
- (let ((repl (funcall replace-fn)))
- (if (bufferp repl)
- (replace-buffer-contents repl)
- (let ((source-buffer (current-buffer)))
- (with-temp-buffer
- (insert repl)
- (let ((tmp-buffer (current-buffer)))
- (set-buffer source-buffer)
- (replace-buffer-contents tmp-buffer)))))))))
-
;;; subr.el ends here
#include <config.h>
#include <sys/types.h>
+#include <sys/time.h>
#include <stdio.h>
#ifdef HAVE_PWD_H
#undef EQUAL
#define USE_HEURISTIC
-#ifdef USE_HEURISTIC
-#define DIFFSEQ_HEURISTIC
-#endif
-
/* Counter used to rarely_quit in replace-buffer-contents. */
static unsigned short rbc_quitcounter;
/* Bit vectors recording for each character whether it was deleted
or inserted. */ \
unsigned char *deletions; \
- unsigned char *insertions;
+ unsigned char *insertions; \
+ struct timeval start; \
+ double max_secs; \
+ unsigned int early_abort_tests;
#define NOTE_DELETE(ctx, xoff) set_bit ((ctx)->deletions, (xoff))
#define NOTE_INSERT(ctx, yoff) set_bit ((ctx)->insertions, (yoff))
+#define EARLY_ABORT(ctx) compareseq_early_abort (ctx)
struct context;
static void set_bit (unsigned char *, OFFSET);
static bool bit_is_set (const unsigned char *, OFFSET);
static bool buffer_chars_equal (struct context *, OFFSET, OFFSET);
+static bool compareseq_early_abort (struct context *);
#include "minmax.h"
#include "diffseq.h"
DEFUN ("replace-buffer-contents", Freplace_buffer_contents,
- Sreplace_buffer_contents, 1, 1, "bSource buffer: ",
+ Sreplace_buffer_contents, 1, 3, "bSource buffer: ",
doc: /* Replace accessible portion of current buffer with that of SOURCE.
SOURCE can be a buffer or a string that names a buffer.
Interactively, prompt for SOURCE.
+
As far as possible the replacement is non-destructive, i.e. existing
buffer contents, markers, properties, and overlays in the current
buffer stay intact.
-Warning: this function can be slow if there's a large number of small
-differences between the two buffers. */)
- (Lisp_Object source)
+
+Because this function can be very slow if there is a large number of
+differences between the two buffers, there are two optional arguments
+mitigating this issue.
+
+The MAX-SECS argument, if given, defines a hard limit on the time used
+for comparing the buffers. If it takes longer than MAX-SECS, the
+function falls back to a plain `delete-region' and
+`insert-buffer-substring'. (Note that the checks are not performed
+too evenly over time, so in some cases it may run a bit longer than
+allowed).
+
+The optional argument MAX-COSTS defines the quality of the difference
+computation. If the actual costs exceed this limit, heuristics are
+used to provide a faster but suboptimal solution. The default value
+is 1000000.
+
+This function returns t if a non-destructive replacement could be
+performed. Otherwise, i.e., if MAX-SECS was exceeded, it returns
+nil. */)
+ (Lisp_Object source, Lisp_Object max_secs, Lisp_Object max_costs)
{
struct buffer *a = current_buffer;
Lisp_Object source_buffer = Fget_buffer (source);
empty. */
if (a_empty && b_empty)
- return Qnil;
+ return Qt;
if (a_empty)
- return Finsert_buffer_substring (source, Qnil, Qnil);
+ {
+ Finsert_buffer_substring (source, Qnil, Qnil);
+ return Qt;
+ }
if (b_empty)
{
del_range_both (BEGV, BEGV_BYTE, ZV, ZV_BYTE, true);
- return Qnil;
+ return Qt;
}
ptrdiff_t count = SPECPDL_INDEX ();
ptrdiff_t *buffer;
USE_SAFE_ALLOCA;
SAFE_NALLOCA (buffer, 2, diags);
+
+ if (NILP (max_costs))
+ XSETFASTINT (max_costs, 1000000);
+ else
+ CHECK_FIXNUM (max_costs);
+
/* Micro-optimization: Casting to size_t generates much better
code. */
ptrdiff_t del_bytes = (size_t) size_a / CHAR_BIT + 1;
.insertions = SAFE_ALLOCA (ins_bytes),
.fdiag = buffer + size_b + 1,
.bdiag = buffer + diags + size_b + 1,
-#ifdef DIFFSEQ_HEURISTIC
.heuristic = true,
-#endif
- /* FIXME: Find a good number for .too_expensive. */
- .too_expensive = 64,
+ .too_expensive = XFIXNUM (max_costs),
+ .max_secs = FLOATP (max_secs) ? XFLOAT_DATA (max_secs) : -1.0,
+ .early_abort_tests = 0
};
memclear (ctx.deletions, del_bytes);
memclear (ctx.insertions, ins_bytes);
+
+ gettimeofday (&ctx.start, NULL);
/* compareseq requires indices to be zero-based. We add BEGV back
later. */
bool early_abort = compareseq (0, size_a, 0, size_b, false, &ctx);
- /* Since we didn’t define EARLY_ABORT, we should never abort
- early. */
- eassert (! early_abort);
+
+ if (early_abort)
+ {
+ del_range (min_a, ZV);
+ Finsert_buffer_substring (source, Qnil,Qnil);
+ SAFE_FREE_UNBIND_TO (count, Qnil);
+ return Qnil;
+ }
rbc_quitcounter = 0;
--i;
--j;
}
+
SAFE_FREE_UNBIND_TO (count, Qnil);
rbc_quitcounter = 0;
update_compositions (BEGV, ZV, CHECK_INSIDE);
}
- return Qnil;
+ return Qt;
}
static void
== BUF_FETCH_MULTIBYTE_CHAR (ctx->buffer_b, bpos_b);
}
+static bool
+compareseq_early_abort (struct context *ctx)
+{
+ if (ctx->max_secs < 0.0)
+ return false;
+
+ struct timeval now, diff;
+ gettimeofday (&now, NULL);
+ timersub (&now, &ctx->start, &diff);
+ return diff.tv_sec + diff.tv_usec / 1000000.0 > ctx->max_secs;
+}
+
\f
static void
subst_char_in_region_unwind (Lisp_Object arg)
binary_as_unsigned = true;
#endif
+ DEFVAR_LISP ("replace-buffer-contents-max-secs",
+ Vreplace_buffer_contents_max_secs,
+ doc: /* If differencing the two buffers takes longer than this,
+`replace-buffer-contents' falls back to a plain delete and insert. */);
+ Vreplace_buffer_contents_max_secs = Qnil;
+
defsubr (&Spropertize);
defsubr (&Schar_equal);
defsubr (&Sgoto_char);
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