{"thread":{"id":"13001","subject":"[PATCH] Add description of OFS_DELTA to the pack format description","startedAt":"2008-04-06T13:47:39Z","lastAt":"2008-04-06T22:26:36Z","messageCount":6,"participants":["Peter Eriksen","Shawn O. Pearce"],"isPatch":true,"patchVersion":1,"patchTotal":null},"messages":[{"id":"73741","messageId":"20080406134739.GA29815@bohr.gbar.dtu.dk","threadId":"13001","inReplyTo":null,"subject":"[PATCH] Add description of OFS_DELTA to the pack format description","fromName":"Peter Eriksen","fromEmail":"s022018@student.dtu.dk","sentAt":"2008-04-06T13:47:39Z","receivedAt":"2008-04-06T13:47:39Z","isPatch":true,"sender":{"key":"s022018@student.dtu.dk","avatar":null},"body":"\n\nSigned-off-by: Peter Eriksen \n---\n\nI'll take it in smaller steps this time.\n\n Documentation/technical/pack-format.txt | 12 +++++++++++-\n 1 files changed, 11 insertions(+), 1 deletions(-)\n\ndiff --git a/Documentation/technical/pack-format.txt b/Documentation/technical/pack-format.txt\nindex aa87756..f6b1405 100644\n--- a/Documentation/technical/pack-format.txt\n+++ b/Documentation/technical/pack-format.txt\n@@ -103,10 +103,20 @@ Pack file entry: <+\n packed object data:\n If it is not DELTA, then deflated bytes (the size above\n \t\tis the size before compression).\n-\tIf it is DELTA, then\n+\tIf it is REF_DELTA, then\n \t 20-byte base object name SHA1 (the size above is the\n \t\tsize of the delta data that follows).\n delta data, deflated.\n+\tIf it is OFS_DELTA, then\n+\t n-byte offset (see below) (the size above is the\n+\t\tsize of the delta data that follows).\n+ delta data, deflated.\n+\n+ offset encoding:\n+ n bytes with MSB set in all but the last one.\n+ The offset is then the number constructed by\n+ concatenating the lower 7 bit of each byte, and\n+ adding 2^7 + 2^14 + ... + 2^(7*(n-1)) to the result.\n \n \n = Version 2 pack-*.idx files support packs larger than 4 GiB, and\n-- \n1.5.5-rc3.GIT\n"},{"id":"73764","messageId":"20080406190724.GG10274@spearce.org","threadId":"13001","inReplyTo":"20080406134739.GA29815@bohr.gbar.dtu.dk","subject":"Re: [PATCH] Add description of OFS_DELTA to the pack format description","fromName":"Shawn O. Pearce","fromEmail":"spearce@spearce.org","sentAt":"2008-04-06T19:07:24Z","receivedAt":"2008-04-06T19:07:24Z","isPatch":true,"sender":{"key":"spearce@spearce.org","avatar":"https://avatars.githubusercontent.com/u/34844?v=4"},"body":"Peter Eriksen wrote:\n> diff --git a/Documentation/technical/pack-format.txt b/Documentation/technical/pack-format.txt\n> index aa87756..f6b1405 100644\n> --- a/Documentation/technical/pack-format.txt\n> +++ b/Documentation/technical/pack-format.txt\n> @@ -103,10 +103,20 @@ Pack file entry: <+\n> packed object data:\n> If it is not DELTA, then deflated bytes (the size above\n> \t\tis the size before compression).\n> -\tIf it is DELTA, then\n> +\tIf it is REF_DELTA, then\n> \t 20-byte base object name SHA1 (the size above is the\n> \t\tsize of the delta data that follows).\n> delta data, deflated.\n> +\tIf it is OFS_DELTA, then\n> +\t n-byte offset (see below) (the size above is the\n> +\t\tsize of the delta data that follows).\n> + delta data, deflated.\n\nYou are missing the description that the position within _this_\npackfile is determined by:\n\n\toffset_of_type_byte - n_byte_offset\n\nThe above can still be taken to mean the offset is from the start\nof the packfile or something like that.\n\n> + offset encoding:\n> + n bytes with MSB set in all but the last one.\n> + The offset is then the number constructed by\n> + concatenating the lower 7 bit of each byte, and\n> + adding 2^7 + 2^14 + ... + 2^(7*(n-1)) to the result.\n\nHmm. I've just spent 5 minutes reading this and I'm still not\ncertain what the result is. 2^0 only gets added to the result if\nthere is at least 2 bytes of data in the offset encoding; in your\ndescription above it sounds like we should add 2^0 (1) even when\nthere is only 1 offset byte (n=1), which is not correct.\n\n-- \nShawn.\n"},{"id":"73769","messageId":"20080406201907.GB7075@bohr.gbar.dtu.dk","threadId":"13001","inReplyTo":"20080406190724.GG10274@spearce.org","subject":"[PATCH v2] Add description of OFS_DELTA to the pack format description","fromName":"Peter Eriksen","fromEmail":"s022018@student.dtu.dk","sentAt":"2008-04-06T20:19:07Z","receivedAt":"2008-04-06T20:19:07Z","isPatch":true,"sender":{"key":"s022018@student.dtu.dk","avatar":null},"body":"\nSigned-off-by: Peter Eriksen \n---\n Documentation/technical/pack-format.txt | 16 +++++++++++++++-\n 1 files changed, 15 insertions(+), 1 deletions(-)\n\n\nOn Sun, Apr 06, 2008 at 03:07:24PM -0400, Shawn O. Pearce wrote:\n...\n> You are missing the description that the position within _this_\n> packfile is determined by:\n> \n> \toffset_of_type_byte - n_byte_offset\n> \n> The above can still be taken to mean the offset is from the start\n> of the packfile or something like that.\n\nYes, I misunderstood that.\n\nPeter\n\ndiff --git a/Documentation/technical/pack-format.txt b/Documentation/technical/pack-format.txt\nindex aa87756..953c7ee 100644\n--- a/Documentation/technical/pack-format.txt\n+++ b/Documentation/technical/pack-format.txt\n@@ -103,10 +103,24 @@ Pack file entry: <+\n packed object data:\n If it is not DELTA, then deflated bytes (the size above\n \t\tis the size before compression).\n-\tIf it is DELTA, then\n+\tIf it is REF_DELTA, then\n \t 20-byte base object name SHA1 (the size above is the\n \t\tsize of the delta data that follows).\n delta data, deflated.\n+\tIf it is OFS_DELTA, then\n+\t n-byte offset (see below) counted from the type-byte\n+ of the header of the ofs-delta entry.\n+ (the size above is the size of the delta data\n+ that follows).\n+ delta data, deflated.\n+\n+ offset encoding:\n+ n bytes with MSB set in all but the last one.\n+ The offset is then the number constructed by\n+ concatenating the lower 7 bit of each byte, and\n+ for n >= 2 adding 2^7 + 2^14 + ... + 2^(7*(n-1))\n+ to the result.\n+ \n \n \n = Version 2 pack-*.idx files support packs larger than 4 GiB, and\n-- \n1.5.5-rc3.GIT\n"},{"id":"73770","messageId":"20080406202821.GN10274@spearce.org","threadId":"13001","inReplyTo":"20080406201907.GB7075@bohr.gbar.dtu.dk","subject":"Re: [PATCH v2] Add description of OFS_DELTA to the pack format description","fromName":"Shawn O. Pearce","fromEmail":"spearce@spearce.org","sentAt":"2008-04-06T20:28:21Z","receivedAt":"2008-04-06T20:28:21Z","isPatch":true,"sender":{"key":"spearce@spearce.org","avatar":"https://avatars.githubusercontent.com/u/34844?v=4"},"body":"Peter Eriksen wrote:\n> \n> diff --git a/Documentation/technical/pack-format.txt b/Documentation/technical/pack-format.txt\n> index aa87756..953c7ee 100644\n> --- a/Documentation/technical/pack-format.txt\n> +++ b/Documentation/technical/pack-format.txt\n> @@ -103,10 +103,24 @@ Pack file entry: <+\n> packed object data:\n> If it is not DELTA, then deflated bytes (the size above\n> \t\tis the size before compression).\n> -\tIf it is DELTA, then\n> +\tIf it is REF_DELTA, then\n> \t 20-byte base object name SHA1 (the size above is the\n> \t\tsize of the delta data that follows).\n> delta data, deflated.\n> +\tIf it is OFS_DELTA, then\n> +\t n-byte offset (see below) counted from the type-byte\n> + of the header of the ofs-delta entry.\n\nExcept that only a positive offset value is here, as it is always\na treated as a negative offset (you can only refer to a base that\nwas before you, as that is the only way to know the base's offset\nin the pack).\n\n> + (the size above is the size of the delta data\n> + that follows).\n> + delta data, deflated.\n> +\n> + offset encoding:\n> + n bytes with MSB set in all but the last one.\n> + The offset is then the number constructed by\n> + concatenating the lower 7 bit of each byte, and\n> + for n >= 2 adding 2^7 + 2^14 + ... + 2^(7*(n-1))\n> + to the result.\n\nYes, that sounds correct.\n\n-- \nShawn.\n"},{"id":"73777","messageId":"20080406205149.GD7075@bohr.gbar.dtu.dk","threadId":"13001","inReplyTo":"20080406202821.GN10274@spearce.org","subject":"[PATCH v3] Add description of OFS_DELTA to the pack format description","fromName":"Peter Eriksen","fromEmail":"s022018@student.dtu.dk","sentAt":"2008-04-06T20:51:49Z","receivedAt":"2008-04-06T20:51:49Z","isPatch":true,"sender":{"key":"s022018@student.dtu.dk","avatar":null},"body":"\nSigned-off-by: Peter Eriksen \n---\n Documentation/technical/pack-format.txt | 16 +++++++++++++++-\n 1 files changed, 15 insertions(+), 1 deletions(-)\n\ndiff --git a/Documentation/technical/pack-format.txt b/Documentation/technical/pack-format.txt\nindex aa87756..6b2170f 100644\n--- a/Documentation/technical/pack-format.txt\n+++ b/Documentation/technical/pack-format.txt\n@@ -103,10 +103,24 @@ Pack file entry: <+\n packed object data:\n If it is not DELTA, then deflated bytes (the size above\n \t\tis the size before compression).\n-\tIf it is DELTA, then\n+\tIf it is REF_DELTA, then\n \t 20-byte base object name SHA1 (the size above is the\n \t\tsize of the delta data that follows).\n delta data, deflated.\n+\tIf it is OFS_DELTA, then\n+\t n-byte offset (see below) interpreted as a negative\n+ offset from the type-byte of the header of the\n+ ofs-delta entry (the size above is the size of\n+ the delta data that follows).\n+ delta data, deflated.\n+\n+ offset encoding:\n+ n bytes with MSB set in all but the last one.\n+ The offset is then the number constructed by\n+ concatenating the lower 7 bit of each byte, and\n+ for n >= 2 adding 2^7 + 2^14 + ... + 2^(7*(n-1))\n+ to the result.\n+ \n \n \n = Version 2 pack-*.idx files support packs larger than 4 GiB, and\n-- \n1.5.5-rc3.GIT\n"},{"id":"73786","messageId":"20080406222636.GP10274@spearce.org","threadId":"13001","inReplyTo":"20080406205149.GD7075@bohr.gbar.dtu.dk","subject":"Re: [PATCH v3] Add description of OFS_DELTA to the pack format description","fromName":"Shawn O. Pearce","fromEmail":"spearce@spearce.org","sentAt":"2008-04-06T22:26:36Z","receivedAt":"2008-04-06T22:26:36Z","isPatch":true,"sender":{"key":"spearce@spearce.org","avatar":"https://avatars.githubusercontent.com/u/34844?v=4"},"body":"Peter Eriksen wrote:\n> -\tIf it is DELTA, then\n> +\tIf it is REF_DELTA, then\n> \t 20-byte base object name SHA1 (the size above is the\n> \t\tsize of the delta data that follows).\n> delta data, deflated.\n> +\tIf it is OFS_DELTA, then\n> +\t n-byte offset (see below) interpreted as a negative\n> + offset from the type-byte of the header of the\n> + ofs-delta entry (the size above is the size of\n> + the delta data that follows).\n> + delta data, deflated.\n> +\n> + offset encoding:\n> + n bytes with MSB set in all but the last one.\n> + The offset is then the number constructed by\n> + concatenating the lower 7 bit of each byte, and\n> + for n >= 2 adding 2^7 + 2^14 + ... + 2^(7*(n-1))\n> + to the result.\n> + \n\nYup. :-)\n\nAcked-by: Shawn O. Pearce \n\n-- \nShawn.\n"}]}