Merge branch 'jc/perl-cat-blob' into maint
[git/jnareb-git.git] / vcs-svn / sliding_window.c
blobf11d490995ee7e3367c1d18e1058f2e322cfa177
1 /*
2 * Licensed under a two-clause BSD-style license.
3 * See LICENSE for details.
4 */
6 #include "git-compat-util.h"
7 #include "sliding_window.h"
8 #include "line_buffer.h"
9 #include "strbuf.h"
11 static int input_error(struct line_buffer *file)
13 if (!buffer_ferror(file))
14 return error("delta preimage ends early");
15 return error("cannot read delta preimage: %s", strerror(errno));
18 static int skip_or_whine(struct line_buffer *file, off_t gap)
20 if (buffer_skip_bytes(file, gap) != gap)
21 return input_error(file);
22 return 0;
25 static int read_to_fill_or_whine(struct line_buffer *file,
26 struct strbuf *buf, size_t width)
28 buffer_read_binary(file, buf, width - buf->len);
29 if (buf->len != width)
30 return input_error(file);
31 return 0;
34 static int check_offset_overflow(off_t offset, uintmax_t len)
36 if (len > maximum_signed_value_of_type(off_t))
37 return error("unrepresentable length in delta: "
38 "%"PRIuMAX" > OFF_MAX", len);
39 if (signed_add_overflows(offset, (off_t) len))
40 return error("unrepresentable offset in delta: "
41 "%"PRIuMAX" + %"PRIuMAX" > OFF_MAX",
42 (uintmax_t) offset, len);
43 return 0;
46 int move_window(struct sliding_view *view, off_t off, size_t width)
48 off_t file_offset;
49 assert(view);
50 assert(view->width <= view->buf.len);
51 assert(!check_offset_overflow(view->off, view->buf.len));
53 if (check_offset_overflow(off, width))
54 return -1;
55 if (off < view->off || off + width < view->off + view->width)
56 return error("invalid delta: window slides left");
57 if (view->max_off >= 0 && view->max_off < off + (off_t) width)
58 return error("delta preimage ends early");
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);
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;
76 view->off = off;
77 view->width = width;
78 return 0;