Merge branch 'rs/nth-switch-code-simplification'
[git/git.git] / vcs-svn / sliding_window.c
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1/*
2 * Licensed under a two-clause BSD-style license.
3 * See LICENSE for details.
4 */
5
6#include "git-compat-util.h"
7#include "sliding_window.h"
8#include "line_buffer.h"
9#include "strbuf.h"
10
11static int input_error(struct line_buffer *file)
12{
13 if (!buffer_ferror(file))
14 return error("delta preimage ends early");
1c8ead97 15 return error_errno("cannot read delta preimage");
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16}
17
18static int skip_or_whine(struct line_buffer *file, off_t gap)
19{
20 if (buffer_skip_bytes(file, gap) != gap)
21 return input_error(file);
22 return 0;
23}
24
25static int read_to_fill_or_whine(struct line_buffer *file,
26 struct strbuf *buf, size_t width)
27{
28 buffer_read_binary(file, buf, width - buf->len);
29 if (buf->len != width)
30 return input_error(file);
31 return 0;
32}
33
5b8bf029 34static int check_offset_overflow(off_t offset, uintmax_t len)
9d2f5ddf 35{
ce8ebcda 36 if (len > maximum_signed_value_of_type(off_t))
9d2f5ddf 37 return error("unrepresentable length in delta: "
5b8bf029 38 "%"PRIuMAX" > OFF_MAX", len);
ce8ebcda 39 if (signed_add_overflows(offset, (off_t) len))
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40 return error("unrepresentable offset in delta: "
41 "%"PRIuMAX" + %"PRIuMAX" > OFF_MAX",
5b8bf029 42 (uintmax_t) offset, len);
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43 return 0;
44}
45
46int move_window(struct sliding_view *view, off_t off, size_t width)
47{
48 off_t file_offset;
49 assert(view);
50 assert(view->width <= view->buf.len);
ce8ebcda 51 assert(!check_offset_overflow(view->off, view->buf.len));
9d2f5ddf 52
ce8ebcda 53 if (check_offset_overflow(off, width))
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54 return -1;
55 if (off < view->off || off + width < view->off + view->width)
56 return error("invalid delta: window slides left");
c68038ef 57 if (view->max_off >= 0 && view->max_off < off + (off_t) width)
fbdd4f6f 58 return error("delta preimage ends early");
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59
60 file_offset = view->off + view->buf.len;
61 if (off < file_offset) {
62 /* Move the overlapping region into place. */
63 strbuf_remove(&view->buf, 0, off - view->off);
64 } else {
65 /* Seek ahead to skip the gap. */
66 if (skip_or_whine(view->file, off - file_offset))
67 return -1;
68 strbuf_setlen(&view->buf, 0);
69 }
70
71 if (view->buf.len > width)
72 ; /* Already read. */
73 else if (read_to_fill_or_whine(view->file, &view->buf, width))
74 return -1;
75
76 view->off = off;
77 view->width = width;
78 return 0;
79}