git/list[1] front-page[2] threads[3] people[4] search[5] about
 

[PATCH v2 08/11] streaming_write_entry(): support files with holes

From
Junio C Hamano <gitster@pobox.com>
Date
May 19, 2011, 21:33 UTC
Message-ID
<1305840826-7783-9-git-send-email-gitster@pobox.com>
In-Reply-To
<1305840826-7783-1-git-send-email-gitster@pobox.com>

One typical use of a large binary file is to hold a sparse on-disk hash table with a lot of holes. Help preserving the holes with lseek().

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 entry.c |   21 +++++++++++++++++++--
 1 files changed, 19 insertions(+), 2 deletions(-)
diff --git a/entry.c b/entry.c
index 7733a6b..f751c60 100644
--- a/entry.c
+++ b/entry.c
@@ -123,6 +123,7 @@ static int streaming_write_entry(struct cache_entry *ce, char *path,
 	enum object_type type;
 	unsigned long sz;
 	int result = -1;
+	ssize_t kept = 0;
 	int fd = -1;
 
 	st = open_istream(ce->sha1, &type, &sz);
@@ -136,18 +137,34 @@ static int streaming_write_entry(struct cache_entry *ce, char *path,
 		goto close_and_exit;
 
 	for (;;) {
-		char buf[10240];
-		ssize_t wrote;
+		char buf[1024 * 16];
+		ssize_t wrote, holeto;
 		ssize_t readlen = read_istream(st, buf, sizeof(buf));
 
 		if (!readlen)
 			break;
+		if (sizeof(buf) == readlen) {
+			for (holeto = 0; holeto < readlen; holeto++)
+				if (buf[holeto])
+					break;
+			if (readlen == holeto) {
+				kept += holeto;
+				continue;
+			}
+		}
 
+		if (kept && lseek(fd, kept, SEEK_CUR) == (off_t) -1)
+			goto close_and_exit;
+		else
+			kept = 0;
 		wrote = write_in_full(fd, buf, readlen);
 
 		if (wrote != readlen)
 			goto close_and_exit;
 	}
+	if (kept && (lseek(fd, kept - 1, SEEK_CUR) == (off_t) -1 ||
+		     write(fd, "", 1) != 1))
+		goto close_and_exit;
 	*fstat_done = fstat_output(fd, state, statbuf);
 
 close_and_exit:
-- 
1.7.5.1.416.gac10c8
Previous: Junio C HamanoNext: Junio C Hamano
Message 44 of 49 in “writing out a huge blob to working tree”
  1. 00/11 writing out a huge blob to working treeJunio C Hamano, May 16, 2011
  2. 01/11 packed_object_info_detail(): do not return a stringJunio C Hamano, May 16, 2011
  3. Thiago FarinaMay 17, 2011
  4. Junio C HamanoMay 17, 2011
  5. 02/11 sha1_object_info_extended(): expose a bit more infoJunio C Hamano, May 16, 2011
  6. 03/11 sha1_object_info_extended(): hint about objects in delta-base cacheJunio C Hamano, May 16, 2011
  7. Shawn PearceMay 16, 2011
  8. 04/11 unpack_object_header(): make it publicJunio C Hamano, May 16, 2011
  9. 05/11 write_entry(): separate two helper functions outJunio C Hamano, May 16, 2011
  10. 06/11 streaming: a new API to read from the object storeJunio C Hamano, May 16, 2011
  11. Jeff KingMay 18, 2011
  12. Junio C HamanoMay 19, 2011
  13. 07/11 streaming_write_entry(): use streaming API in write_entry()Junio C Hamano, May 16, 2011
  14. 08/11 streaming_write_entry(): support files with holesJunio C Hamano, May 16, 2011
  15. Nguyen Thai Ngoc DuyMay 16, 2011
  16. Junio C HamanoMay 16, 2011
  17. Nguyen Thai Ngoc DuyMay 17, 2011
  18. Junio C HamanoMay 17, 2011
  19. Thiago FarinaMay 16, 2011
  20. 09/11 streaming: read non-delta incrementally from a packJunio C Hamano, May 16, 2011
  21. Shawn PearceMay 16, 2011
  22. Junio C HamanoMay 16, 2011
  23. 10/11 sha1_file.c: expose helpers to read loose objectsJunio C Hamano, May 16, 2011
  24. 11/11 streaming: read loose objects incrementallyJunio C Hamano, May 16, 2011
  25. Shawn PearceMay 16, 2011
  26. Jeff KingMay 18, 2011
  27. Jeff KingMay 18, 2011
  28. Jeff KingMay 18, 2011
  29. Junio C HamanoMay 18, 2011
  30. Jeff KingMay 18, 2011
  31. 00/11 writing out a huge blob to working treeJunio C Hamano, May 19, 2011
  32. 01/11 packed_object_info_detail(): do not return a stringJunio C Hamano, May 19, 2011
  33. 02/11 sha1_object_info_extended(): expose a bit more infoJunio C Hamano, May 19, 2011
  34. 03/11 sha1_object_info_extended(): hint about objects in delta-base cacheJunio C Hamano, May 19, 2011
  35. René ScharfeMay 20, 2011
  36. Junio C HamanoMay 21, 2011
  37. 04/11 unpack_object_header(): make it publicJunio C Hamano, May 19, 2011
  38. 05/11 write_entry(): separate two helper functions outJunio C Hamano, May 19, 2011
  39. 06/11 streaming: a new API to read from the object storeJunio C Hamano, May 19, 2011
  40. René ScharfeMay 20, 2011
  41. Junio C HamanoMay 21, 2011
  42. 07/11 streaming_write_entry(): use streaming API in write_entry()Junio C Hamano, May 19, 2011
  43. Junio C HamanoMay 20, 2011
  44. 08/11 streaming_write_entry(): support files with holesJunio C Hamano, May 19, 2011
  45. 09/11 streaming: read non-delta incrementally from a packJunio C Hamano, May 19, 2011
  46. 10/11 sha1_file.c: expose helpers to read loose objectsJunio C Hamano, May 19, 2011
  47. 11/11 streaming: read loose objects incrementallyJunio C Hamano, May 19, 2011
  48. 02/11 interdiffJunio C Hamano, May 19, 2011
  49. Jeff KingMay 19, 2011

Read the whole thread, see it on lore, or plain text.

$ cat FOOTERMessages come from the public archive at lore.kernel.org/git, fetched every hour. The front page is chosen and written each morning by an AI editor and can be wrong; the threads themselves are the record. About and API. For agents: an MCP server at https://gitlist.dev/mcp, and any thread, story or person page as Markdown by adding .md to its URL (or sending Accept: text/markdown). Details in /llms.txt.