2018-10-18 01:13:26 +03:00
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#ifndef SLIDING_WINDOW_H
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#define SLIDING_WINDOW_H
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vcs-svn: learn to maintain a sliding view of a file
Each section of a Subversion-format delta only requires examining (and
keeping in random-access memory) a small portion of the preimage. At
any moment, this portion starts at a certain file offset and has a
well-defined length, and as the delta is applied, the portion advances
from the beginning to the end of the preimage. Add a move_window
function to keep track of this view into the preimage.
You can use it like this:
buffer_init(f, NULL);
struct sliding_view window = SLIDING_VIEW_INIT(f);
move_window(&window, 3, 7); /* (1) */
move_window(&window, 5, 5); /* (2) */
move_window(&window, 12, 2); /* (3) */
strbuf_release(&window.buf);
buffer_deinit(f);
The data structure is called sliding_view instead of _window to
prevent confusion with svndiff0 Windows.
In this example, (1) reads 10 bytes and discards the first 3;
(2) discards the first 2, which are not needed any more; and (3) skips
2 bytes and reads 2 new bytes to work with.
When move_window returns, the file position indicator is at position
window->off + window->width and the data from positions window->off to
the current file position are stored in window->buf.
This function performs only sequential access from the input file and
never seeks, so it can be safely used on pipes and sockets.
On end-of-file, move_window silently reads less than the caller
requested. On other errors, it prints a message and returns -1.
Helped-by: David Barr <david.barr@cordelta.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
2011-01-03 06:54:58 +03:00
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#include "strbuf.h"
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struct sliding_view {
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struct line_buffer *file;
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off_t off;
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size_t width;
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2011-05-27 13:07:44 +04:00
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off_t max_off; /* -1 means unlimited */
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vcs-svn: learn to maintain a sliding view of a file
Each section of a Subversion-format delta only requires examining (and
keeping in random-access memory) a small portion of the preimage. At
any moment, this portion starts at a certain file offset and has a
well-defined length, and as the delta is applied, the portion advances
from the beginning to the end of the preimage. Add a move_window
function to keep track of this view into the preimage.
You can use it like this:
buffer_init(f, NULL);
struct sliding_view window = SLIDING_VIEW_INIT(f);
move_window(&window, 3, 7); /* (1) */
move_window(&window, 5, 5); /* (2) */
move_window(&window, 12, 2); /* (3) */
strbuf_release(&window.buf);
buffer_deinit(f);
The data structure is called sliding_view instead of _window to
prevent confusion with svndiff0 Windows.
In this example, (1) reads 10 bytes and discards the first 3;
(2) discards the first 2, which are not needed any more; and (3) skips
2 bytes and reads 2 new bytes to work with.
When move_window returns, the file position indicator is at position
window->off + window->width and the data from positions window->off to
the current file position are stored in window->buf.
This function performs only sequential access from the input file and
never seeks, so it can be safely used on pipes and sockets.
On end-of-file, move_window silently reads less than the caller
requested. On other errors, it prints a message and returns -1.
Helped-by: David Barr <david.barr@cordelta.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
2011-01-03 06:54:58 +03:00
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struct strbuf buf;
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};
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2011-05-27 13:07:44 +04:00
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#define SLIDING_VIEW_INIT(input, len) { (input), 0, 0, (len), STRBUF_INIT }
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vcs-svn: learn to maintain a sliding view of a file
Each section of a Subversion-format delta only requires examining (and
keeping in random-access memory) a small portion of the preimage. At
any moment, this portion starts at a certain file offset and has a
well-defined length, and as the delta is applied, the portion advances
from the beginning to the end of the preimage. Add a move_window
function to keep track of this view into the preimage.
You can use it like this:
buffer_init(f, NULL);
struct sliding_view window = SLIDING_VIEW_INIT(f);
move_window(&window, 3, 7); /* (1) */
move_window(&window, 5, 5); /* (2) */
move_window(&window, 12, 2); /* (3) */
strbuf_release(&window.buf);
buffer_deinit(f);
The data structure is called sliding_view instead of _window to
prevent confusion with svndiff0 Windows.
In this example, (1) reads 10 bytes and discards the first 3;
(2) discards the first 2, which are not needed any more; and (3) skips
2 bytes and reads 2 new bytes to work with.
When move_window returns, the file position indicator is at position
window->off + window->width and the data from positions window->off to
the current file position are stored in window->buf.
This function performs only sequential access from the input file and
never seeks, so it can be safely used on pipes and sockets.
On end-of-file, move_window silently reads less than the caller
requested. On other errors, it prints a message and returns -1.
Helped-by: David Barr <david.barr@cordelta.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
2011-01-03 06:54:58 +03:00
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2019-04-29 11:28:14 +03:00
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int move_window(struct sliding_view *view, off_t off, size_t width);
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vcs-svn: learn to maintain a sliding view of a file
Each section of a Subversion-format delta only requires examining (and
keeping in random-access memory) a small portion of the preimage. At
any moment, this portion starts at a certain file offset and has a
well-defined length, and as the delta is applied, the portion advances
from the beginning to the end of the preimage. Add a move_window
function to keep track of this view into the preimage.
You can use it like this:
buffer_init(f, NULL);
struct sliding_view window = SLIDING_VIEW_INIT(f);
move_window(&window, 3, 7); /* (1) */
move_window(&window, 5, 5); /* (2) */
move_window(&window, 12, 2); /* (3) */
strbuf_release(&window.buf);
buffer_deinit(f);
The data structure is called sliding_view instead of _window to
prevent confusion with svndiff0 Windows.
In this example, (1) reads 10 bytes and discards the first 3;
(2) discards the first 2, which are not needed any more; and (3) skips
2 bytes and reads 2 new bytes to work with.
When move_window returns, the file position indicator is at position
window->off + window->width and the data from positions window->off to
the current file position are stored in window->buf.
This function performs only sequential access from the input file and
never seeks, so it can be safely used on pipes and sockets.
On end-of-file, move_window silently reads less than the caller
requested. On other errors, it prints a message and returns -1.
Helped-by: David Barr <david.barr@cordelta.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
2011-01-03 06:54:58 +03:00
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#endif
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