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https://github.com/git/git
synced 2024-09-13 13:24:41 +00:00
ce8ebcdaf3
The canonical interpretation of a range a,b is as an interval [a,b), not [a,a+b), so this function taking argument names a and b feels unnatural. Use more explicit names "offset" and "len" to make the arguments' type and function clearer. While at it, rename the function to convey that we are making sure the sum of this offset and length do not overflow an off_t, not a size_t. [jn: split out from a patch from Ramsay Jones, then improved with advice from Thomas Rast, Dmitry Ivankov, and David Barr] Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Improved-by: Dmitry Ivankov <divanorama@gmail.com>
80 lines
2.1 KiB
C
80 lines
2.1 KiB
C
/*
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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("cannot read delta preimage: %s", strerror(errno));
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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, size_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", (uintmax_t) 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, (uintmax_t) 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 + 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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