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/*
* Licensed under a two-clause BSD-style license.
* See LICENSE for details.
*/
#include "git-compat-util.h"
#include "sliding_window.h"
#include "line_buffer.h"
#include "strbuf.h"
static int input_error(struct line_buffer *file)
{
if (!buffer_ferror(file))
return error("delta preimage ends early");
return error("cannot read delta preimage: %s", strerror(errno));
}
static int skip_or_whine(struct line_buffer *file, off_t gap)
{
if (buffer_skip_bytes(file, gap) != gap)
return input_error(file);
return 0;
}
static int read_to_fill_or_whine(struct line_buffer *file,
struct strbuf *buf, size_t width)
{
buffer_read_binary(file, buf, width - buf->len);
if (buf->len != width)
return input_error(file);
return 0;
}
static int check_overflow(off_t a, size_t b)
{
if (b > maximum_signed_value_of_type(off_t))
return error("unrepresentable length in delta: "
"%"PRIuMAX" > OFF_MAX", (uintmax_t) b);
if (signed_add_overflows(a, (off_t) b))
return error("unrepresentable offset in delta: "
"%"PRIuMAX" + %"PRIuMAX" > OFF_MAX",
(uintmax_t) a, (uintmax_t) b);
return 0;
}
int move_window(struct sliding_view *view, off_t off, size_t width)
{
off_t file_offset;
assert(view);
assert(view->width <= view->buf.len);
assert(!check_overflow(view->off, view->buf.len));
if (check_overflow(off, width))
return -1;
if (off < view->off || off + width < view->off + view->width)
return error("invalid delta: window slides left");
if (view->max_off >= 0 && view->max_off < off + width)
return error("delta preimage ends early");
file_offset = view->off + view->buf.len;
if (off < file_offset) {
/* Move the overlapping region into place. */
strbuf_remove(&view->buf, 0, off - view->off);
} else {
/* Seek ahead to skip the gap. */
if (skip_or_whine(view->file, off - file_offset))
return -1;
strbuf_setlen(&view->buf, 0);
}
if (view->buf.len > width)
; /* Already read. */
else if (read_to_fill_or_whine(view->file, &view->buf, width))
return -1;
view->off = off;
view->width = width;
return 0;
}
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