From: Michael Haggerty <mhagger@alum.mit.edu>
To: Junio C Hamano <gitster@pobox.com>
Cc: Kim Gybels <kgybels@infogroep.be>,
Johannes Schindelin <johannes.schindelin@gmx.de>,
Jeff King <peff@peff.net>,
git@vger.kernel.org, Michael Haggerty <mhagger@alum.mit.edu>
Subject: [PATCH 1/6] struct snapshot: store `start` rather than `header_len`
Date: Wed, 24 Jan 2018 12:14:11 +0100 [thread overview]
Message-ID: <2adb70b238a5f7f65f19344007e1743cc96644b8.1516791909.git.mhagger@alum.mit.edu> (raw)
In-Reply-To: <cea5e366-dc95-6f41-6373-f8bbef103561@alum.mit.edu>
In-Reply-To: <cover.1516791909.git.mhagger@alum.mit.edu>
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>
---
refs/packed-backend.c | 64 ++++++++++++++++++++++++++-------------------------
1 file changed, 33 insertions(+), 31 deletions(-)
diff --git a/refs/packed-backend.c b/refs/packed-backend.c
index 023243fd5f..b872267f02 100644
--- a/refs/packed-backend.c
+++ b/refs/packed-backend.c
@@ -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;
--
2.14.2
next prev parent reply other threads:[~2018-01-24 11:14 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-13 16:11 [PATCH] packed_ref_cache: don't use mmap() for small files Kim Gybels
2018-01-13 18:56 ` Johannes Schindelin
2018-01-14 19:14 ` [PATCH v2] " Kim Gybels
2018-01-15 12:17 ` [PATCH 0/3] Supplements to "packed_ref_cache: don't use mmap() for small files" Michael Haggerty
2018-01-15 12:17 ` [PATCH 1/3] SQUASH? Mention that `snapshot::buf` can be NULL for empty files Michael Haggerty
2018-01-15 12:17 ` [PATCH 2/3] create_snapshot(): exit early if the file was empty Michael Haggerty
2018-01-15 12:17 ` [PATCH 3/3] find_reference_location(): don't invoke if `snapshot->buf` is NULL Michael Haggerty
2018-01-17 20:23 ` [PATCH 0/3] Supplements to "packed_ref_cache: don't use mmap() for small files" Johannes Schindelin
2018-01-17 21:52 ` Junio C Hamano
2018-01-15 21:15 ` [PATCH] packed_ref_cache: don't use mmap() for small files Jeff King
2018-01-15 23:37 ` Kim Gybels
2018-01-15 23:52 ` Jeff King
2018-01-16 19:38 ` [PATCH v3] " Kim Gybels
2018-01-17 22:09 ` Jeff King
2018-01-21 4:41 ` Michael Haggerty
2018-01-22 19:31 ` Junio C Hamano
2018-01-24 11:05 ` Michael Haggerty
2018-01-24 11:14 ` [PATCH 0/6] Yet another approach to handling empty snapshots Michael Haggerty
2018-01-24 11:14 ` Michael Haggerty [this message]
2018-01-24 20:36 ` [PATCH 1/6] struct snapshot: store `start` rather than `header_len` Jeff King
2018-01-24 11:14 ` [PATCH 2/6] create_snapshot(): use `xmemdupz()` rather than a strbuf Michael Haggerty
2018-01-24 11:14 ` [PATCH 3/6] find_reference_location(): make function safe for empty snapshots Michael Haggerty
2018-01-24 20:27 ` Jeff King
2018-01-24 21:11 ` Junio C Hamano
2018-01-24 21:34 ` Jeff King
2018-01-24 11:14 ` [PATCH 4/6] packed_ref_iterator_begin(): make optimization more general Michael Haggerty
2018-01-24 20:32 ` Jeff King
2018-01-24 11:14 ` [PATCH 5/6] load_contents(): don't try to mmap an empty file Michael Haggerty
2018-01-24 11:14 ` [PATCH 6/6] packed_ref_cache: don't use mmap() for small files Michael Haggerty
2018-01-24 20:38 ` [PATCH 0/6] Yet another approach to handling empty snapshots Jeff King
2018-01-24 20:54 ` Junio C Hamano
2018-02-15 16:54 ` Johannes Schindelin
2018-01-24 18:05 ` [PATCH v3] packed_ref_cache: don't use mmap() for small files Junio C Hamano
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=2adb70b238a5f7f65f19344007e1743cc96644b8.1516791909.git.mhagger@alum.mit.edu \
--to=mhagger@alum.mit.edu \
--cc=git@vger.kernel.org \
--cc=gitster@pobox.com \
--cc=johannes.schindelin@gmx.de \
--cc=kgybels@infogroep.be \
--cc=peff@peff.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).