зеркало из https://github.com/microsoft/git.git
Merge branch 'kg/packed-ref-cache-fix'
Avoid mmapping small files while using packed refs (especially ones with zero size, which would cause later munmap() to fail). * kg/packed-ref-cache-fix: packed_ref_cache: don't use mmap() for small files load_contents(): don't try to mmap an empty file packed_ref_iterator_begin(): make optimization more general find_reference_location(): make function safe for empty snapshots create_snapshot(): use `xmemdupz()` rather than a strbuf struct snapshot: store `start` rather than `header_len`
This commit is contained in:
Junio C Hamano
Коммит
9db22910f7
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@ -68,17 +68,21 @@ struct snapshot {
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int mmapped;
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/*
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* The contents of the `packed-refs` file. If the file was
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* already sorted, this points at the mmapped contents of the
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* file. If not, this points at heap-allocated memory
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* containing the contents, sorted. If there were no contents
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* (e.g., because the file didn't exist), `buf` and `eof` are
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* both NULL.
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* The contents of the `packed-refs` file:
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*
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* - buf -- a pointer to the start of the memory
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* - start -- a pointer to the first byte of actual references
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* (i.e., after the header line, if one is present)
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* - eof -- a pointer just past the end of the reference
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* contents
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*
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* If the `packed-refs` file was already sorted, `buf` points
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* at the mmapped contents of the file. If not, it points at
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* heap-allocated memory containing the contents, sorted. If
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* there were no contents (e.g., because the file didn't
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* exist), `buf`, `start`, and `eof` are all NULL.
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*/
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char *buf, *eof;
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/* The size of the header line, if any; otherwise, 0: */
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size_t header_len;
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char *buf, *start, *eof;
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/*
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* What is the peeled state of the `packed-refs` file that
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@ -169,8 +173,7 @@ static void clear_snapshot_buffer(struct snapshot *snapshot)
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} else {
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free(snapshot->buf);
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}
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snapshot->buf = snapshot->eof = NULL;
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snapshot->header_len = 0;
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snapshot->buf = snapshot->start = snapshot->eof = NULL;
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}
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/*
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@ -319,13 +322,14 @@ static void sort_snapshot(struct snapshot *snapshot)
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size_t len, i;
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char *new_buffer, *dst;
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pos = snapshot->buf + snapshot->header_len;
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pos = snapshot->start;
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eof = snapshot->eof;
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len = eof - pos;
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if (!len)
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if (pos == eof)
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return;
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len = eof - pos;
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/*
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* Initialize records based on a crude estimate of the number
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* of references in the file (we'll grow it below if needed):
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@ -391,9 +395,8 @@ static void sort_snapshot(struct snapshot *snapshot)
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* place:
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*/
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clear_snapshot_buffer(snapshot);
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snapshot->buf = new_buffer;
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snapshot->buf = snapshot->start = new_buffer;
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snapshot->eof = new_buffer + len;
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snapshot->header_len = 0;
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cleanup:
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free(records);
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@ -442,23 +445,26 @@ static const char *find_end_of_record(const char *p, const char *end)
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*/
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static void verify_buffer_safe(struct snapshot *snapshot)
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{
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const char *buf = snapshot->buf + snapshot->header_len;
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const char *start = snapshot->start;
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const char *eof = snapshot->eof;
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const char *last_line;
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if (buf == eof)
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if (start == eof)
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return;
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last_line = find_start_of_record(buf, eof - 1);
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last_line = find_start_of_record(start, eof - 1);
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if (*(eof - 1) != '\n' || eof - last_line < GIT_SHA1_HEXSZ + 2)
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die_invalid_line(snapshot->refs->path,
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last_line, eof - last_line);
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}
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#define SMALL_FILE_SIZE (32*1024)
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/*
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* Depending on `mmap_strategy`, either mmap or read the contents of
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* the `packed-refs` file into the snapshot. Return 1 if the file
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* existed and was read, or 0 if the file was absent. Die on errors.
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* existed and was read, or 0 if the file was absent or empty. Die on
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* errors.
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*/
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static int load_contents(struct snapshot *snapshot)
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{
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@ -489,24 +495,23 @@ static int load_contents(struct snapshot *snapshot)
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die_errno("couldn't stat %s", snapshot->refs->path);
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size = xsize_t(st.st_size);
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switch (mmap_strategy) {
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case MMAP_NONE:
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if (!size) {
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return 0;
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} else if (mmap_strategy == MMAP_NONE || size <= SMALL_FILE_SIZE) {
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snapshot->buf = xmalloc(size);
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bytes_read = read_in_full(fd, snapshot->buf, size);
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if (bytes_read < 0 || bytes_read != size)
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die_errno("couldn't read %s", snapshot->refs->path);
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snapshot->eof = snapshot->buf + size;
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snapshot->mmapped = 0;
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break;
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case MMAP_TEMPORARY:
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case MMAP_OK:
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} else {
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snapshot->buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
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snapshot->eof = snapshot->buf + size;
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snapshot->mmapped = 1;
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break;
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}
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close(fd);
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snapshot->start = snapshot->buf;
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snapshot->eof = snapshot->buf + size;
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return 1;
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}
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@ -515,9 +520,11 @@ static int load_contents(struct snapshot *snapshot)
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* `refname` starts. If `mustexist` is true and the reference doesn't
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* exist, then return NULL. If `mustexist` is false and the reference
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* doesn't exist, then return the point where that reference would be
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* inserted. In the latter mode, `refname` doesn't have to be a proper
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* reference name; for example, one could search for "refs/replace/"
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* to find the start of any replace references.
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* inserted, or `snapshot->eof` (which might be NULL) if it would be
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* inserted at the end of the file. In the latter mode, `refname`
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* doesn't have to be a proper reference name; for example, one could
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* search for "refs/replace/" to find the start of any replace
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* references.
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*
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* The record is sought using a binary search, so `snapshot->buf` must
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* be sorted.
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@ -539,7 +546,7 @@ static const char *find_reference_location(struct snapshot *snapshot,
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* preceding records all have reference names that come
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* *before* `refname`.
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*/
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const char *lo = snapshot->buf + snapshot->header_len;
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const char *lo = snapshot->start;
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/*
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* A pointer to a the first character of a record whose
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@ -547,7 +554,7 @@ static const char *find_reference_location(struct snapshot *snapshot,
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*/
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const char *hi = snapshot->eof;
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while (lo < hi) {
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while (lo != hi) {
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const char *mid, *rec;
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int cmp;
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@ -616,9 +623,7 @@ static struct snapshot *create_snapshot(struct packed_ref_store *refs)
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/* If the file has a header line, process it: */
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if (snapshot->buf < snapshot->eof && *snapshot->buf == '#') {
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struct strbuf tmp = STRBUF_INIT;
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char *p;
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const char *eol;
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char *tmp, *p, *eol;
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struct string_list traits = STRING_LIST_INIT_NODUP;
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eol = memchr(snapshot->buf, '\n',
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@ -628,9 +633,9 @@ static struct snapshot *create_snapshot(struct packed_ref_store *refs)
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snapshot->buf,
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snapshot->eof - snapshot->buf);
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strbuf_add(&tmp, snapshot->buf, eol - snapshot->buf);
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tmp = xmemdupz(snapshot->buf, eol - snapshot->buf);
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if (!skip_prefix(tmp.buf, "# pack-refs with:", (const char **)&p))
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if (!skip_prefix(tmp, "# pack-refs with:", (const char **)&p))
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die_invalid_line(refs->path,
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snapshot->buf,
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snapshot->eof - snapshot->buf);
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@ -647,10 +652,10 @@ static struct snapshot *create_snapshot(struct packed_ref_store *refs)
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/* perhaps other traits later as well */
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/* The "+ 1" is for the LF character. */
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snapshot->header_len = eol + 1 - snapshot->buf;
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snapshot->start = eol + 1;
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string_list_clear(&traits, 0);
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strbuf_release(&tmp);
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free(tmp);
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}
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verify_buffer_safe(snapshot);
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@ -671,13 +676,12 @@ static struct snapshot *create_snapshot(struct packed_ref_store *refs)
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* We don't want to leave the file mmapped, so we are
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* forced to make a copy now:
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*/
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size_t size = snapshot->eof -
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(snapshot->buf + snapshot->header_len);
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size_t size = snapshot->eof - snapshot->start;
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char *buf_copy = xmalloc(size);
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memcpy(buf_copy, snapshot->buf + snapshot->header_len, size);
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memcpy(buf_copy, snapshot->start, size);
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clear_snapshot_buffer(snapshot);
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snapshot->buf = buf_copy;
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snapshot->buf = snapshot->start = buf_copy;
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snapshot->eof = buf_copy + size;
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}
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@ -924,7 +928,12 @@ static struct ref_iterator *packed_ref_iterator_begin(
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*/
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snapshot = get_snapshot(refs);
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if (!snapshot->buf)
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if (prefix && *prefix)
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start = find_reference_location(snapshot, prefix, 0);
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else
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start = snapshot->start;
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if (start == snapshot->eof)
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return empty_ref_iterator_begin();
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iter = xcalloc(1, sizeof(*iter));
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@ -934,11 +943,6 @@ static struct ref_iterator *packed_ref_iterator_begin(
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iter->snapshot = snapshot;
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acquire_snapshot(snapshot);
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if (prefix && *prefix)
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start = find_reference_location(snapshot, prefix, 0);
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else
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start = snapshot->buf + snapshot->header_len;
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iter->pos = start;
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iter->eof = snapshot->eof;
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strbuf_init(&iter->refname_buf, 0);
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