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