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struct snapshot: store start rather than header_len

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Store a pointer to the start of the actual references within the
`packed-refs` contents rather than storing the length of the header.
This is more convenient for most users of this field.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Michael Haggerty 2018-01-24 12:14:11 +01:00 committed by Junio C Hamano
parent 3013dff866
commit 4a2854f77c
1 changed files with 33 additions and 31 deletions
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64
refs/packed-backend.c
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@ -68,17 +68,21 @@ struct snapshot {
int mmapped;
/*
* The contents of the `packed-refs` file. If the file was
* already sorted, this points at the mmapped contents of the
* file. If not, this points at heap-allocated memory
* containing the contents, sorted. If there were no contents
* (e.g., because the file didn't exist), `buf` and `eof` are
* both NULL.
* The contents of the `packed-refs` file:
*
* - buf -- a pointer to the start of the memory
* - start -- a pointer to the first byte of actual references
* (i.e., after the header line, if one is present)
* - eof -- a pointer just past the end of the reference
* contents
*
* If the `packed-refs` file was already sorted, `buf` points
* at the mmapped contents of the file. If not, it points at
* heap-allocated memory containing the contents, sorted. If
* there were no contents (e.g., because the file didn't
* exist), `buf`, `start`, and `eof` are all NULL.
*/
char *buf, *eof;
/* The size of the header line, if any; otherwise, 0: */
size_t header_len;
char *buf, *start, *eof;
/*
* What is the peeled state of the `packed-refs` file that
@ -169,8 +173,7 @@ static void clear_snapshot_buffer(struct snapshot *snapshot)
} else {
free(snapshot->buf);
}
snapshot->buf = snapshot->eof = NULL;
snapshot->header_len = 0;
snapshot->buf = snapshot->start = snapshot->eof = NULL;
}
/*
@ -319,13 +322,14 @@ static void sort_snapshot(struct snapshot *snapshot)
size_t len, i;
char *new_buffer, *dst;
pos = snapshot->buf + snapshot->header_len;
pos = snapshot->start;
eof = snapshot->eof;
len = eof - pos;
if (!len)
if (pos == eof)
return;
len = eof - pos;
/*
* Initialize records based on a crude estimate of the number
* of references in the file (we'll grow it below if needed):
@ -391,9 +395,8 @@ static void sort_snapshot(struct snapshot *snapshot)
* place:
*/
clear_snapshot_buffer(snapshot);
snapshot->buf = new_buffer;
snapshot->buf = snapshot->start = new_buffer;
snapshot->eof = new_buffer + len;
snapshot->header_len = 0;
cleanup:
free(records);
@ -442,14 +445,14 @@ static const char *find_end_of_record(const char *p, const char *end)
*/
static void verify_buffer_safe(struct snapshot *snapshot)
{
const char *buf = snapshot->buf + snapshot->header_len;
const char *start = snapshot->start;
const char *eof = snapshot->eof;
const char *last_line;
if (buf == eof)
if (start == eof)
return;
last_line = find_start_of_record(buf, eof - 1);
last_line = find_start_of_record(start, eof - 1);
if (*(eof - 1) != '\n' || eof - last_line < GIT_SHA1_HEXSZ + 2)
die_invalid_line(snapshot->refs->path,
last_line, eof - last_line);
@ -495,18 +498,19 @@ static int load_contents(struct snapshot *snapshot)
bytes_read = read_in_full(fd, snapshot->buf, size);
if (bytes_read < 0 || bytes_read != size)
die_errno("couldn't read %s", snapshot->refs->path);
snapshot->eof = snapshot->buf + size;
snapshot->mmapped = 0;
break;
case MMAP_TEMPORARY:
case MMAP_OK:
snapshot->buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
snapshot->eof = snapshot->buf + size;
snapshot->mmapped = 1;
break;
}
close(fd);
snapshot->start = snapshot->buf;
snapshot->eof = snapshot->buf + size;
return 1;
}
@ -539,7 +543,7 @@ static const char *find_reference_location(struct snapshot *snapshot,
* preceding records all have reference names that come
* *before* `refname`.
*/
const char *lo = snapshot->buf + snapshot->header_len;
const char *lo = snapshot->start;
/*
* A pointer to a the first character of a record whose
@ -617,8 +621,7 @@ static struct snapshot *create_snapshot(struct packed_ref_store *refs)
/* If the file has a header line, process it: */
if (snapshot->buf < snapshot->eof && *snapshot->buf == '#') {
struct strbuf tmp = STRBUF_INIT;
char *p;
const char *eol;
char *p, *eol;
struct string_list traits = STRING_LIST_INIT_NODUP;
eol = memchr(snapshot->buf, '\n',
@ -647,7 +650,7 @@ static struct snapshot *create_snapshot(struct packed_ref_store *refs)
/* perhaps other traits later as well */
/* The "+ 1" is for the LF character. */
snapshot->header_len = eol + 1 - snapshot->buf;
snapshot->start = eol + 1;
string_list_clear(&traits, 0);
strbuf_release(&tmp);
@ -671,13 +674,12 @@ static struct snapshot *create_snapshot(struct packed_ref_store *refs)
* We don't want to leave the file mmapped, so we are
* forced to make a copy now:
*/
size_t size = snapshot->eof -
(snapshot->buf + snapshot->header_len);
size_t size = snapshot->eof - snapshot->start;
char *buf_copy = xmalloc(size);
memcpy(buf_copy, snapshot->buf + snapshot->header_len, size);
memcpy(buf_copy, snapshot->start, size);
clear_snapshot_buffer(snapshot);
snapshot->buf = buf_copy;
snapshot->buf = snapshot->start = buf_copy;
snapshot->eof = buf_copy + size;
}
@ -937,7 +939,7 @@ static struct ref_iterator *packed_ref_iterator_begin(
if (prefix && *prefix)
start = find_reference_location(snapshot, prefix, 0);
else
start = snapshot->buf + snapshot->header_len;
start = snapshot->start;
iter->pos = start;
iter->eof = snapshot->eof;