[PATCH 12/16] vcs-svn: Learn to parse variable-length integers

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From: Jonathan Nieder
Date: Sunday, October 10, 2010 - 7:55 pm

The humble beginnings of the svn-format delta applier.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
Maybe this should be squashed with patch 16.

Ideas for eliminating the code duplication?

 vcs-svn/svndiff.c |   59 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 59 insertions(+), 0 deletions(-)
 create mode 100644 vcs-svn/svndiff.c

diff --git a/vcs-svn/svndiff.c b/vcs-svn/svndiff.c
new file mode 100644
index 0000000..4d122a5
--- /dev/null
+++ b/vcs-svn/svndiff.c
@@ -0,0 +1,59 @@
+/*
+ * Licensed under a two-clause BSD-style license.
+ * See LICENSE for details.
+ */
+
+#include "git-compat-util.h"
+#include "line_buffer.h"
+
+/*
+ * svndiff0 applier
+ *
+ * See http://svn.apache.org/repos/asf/subversion/trunk/notes/svndiff.
+ *
+ * int ::= highdigit* lowdigit;
+ * highdigit ::= # binary 1000 0000 OR-ed with 7 bit value;
+ * lowdigit ::= # 7 bit value;
+ */
+
+#define VLI_CONTINUE	0x80
+#define VLI_DIGIT_MASK	0x7f
+#define VLI_BITS_PER_DIGIT 7
+
+static int read_int(struct line_buffer *in, uintmax_t *result, off_t *len)
+{
+	off_t sz = *len;
+	uintmax_t rv = 0;
+	while (sz) {
+		int ch = buffer_read_char(in);
+		if (ch == EOF)
+			break;
+		sz--;
+		rv <<= VLI_BITS_PER_DIGIT;
+		rv += (ch & VLI_DIGIT_MASK);
+		if (!(ch & VLI_CONTINUE)) {
+			*result = rv;
+			*len = sz;
+			return 0;
+		}
+	}
+	return error("Invalid delta: incomplete integer %"PRIuMAX, rv);
+}
+
+static int parse_int(const char **buf, size_t *result, const char *end)
+{
+	const char *pos;
+	size_t rv = 0;
+	for (pos = *buf; pos != end; pos++) {
+		unsigned char ch = *pos;
+		rv <<= VLI_BITS_PER_DIGIT;
+		rv += (ch & VLI_DIGIT_MASK);
+		if (!(ch & VLI_CONTINUE)) {
+			*result = rv;
+			*buf = pos + 1;
+			return 0;
+		}
+	}
+	return error("Invalid instruction: incomplete integer %"PRIu64,
+		     (uint64_t) rv);
+}
-- 
1.7.2.3

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Messages in current thread:
[PATCH 0/8] Resurrect rr/svn-export, Ramkumar Ramachandra, (Thu Jul 15, 9:22 am)
[PATCH 1/8] Export parse_date_basic() to convert a date st ..., Ramkumar Ramachandra, (Thu Jul 15, 9:22 am)
[PATCH 2/8] Introduce vcs-svn lib, Ramkumar Ramachandra, (Thu Jul 15, 9:22 am)
[PATCH 3/8] Add memory pool library, Ramkumar Ramachandra, (Thu Jul 15, 9:22 am)
[PATCH 4/8] Add treap implementation, Ramkumar Ramachandra, (Thu Jul 15, 9:23 am)
[PATCH 5/8] Add string-specific memory pool, Ramkumar Ramachandra, (Thu Jul 15, 9:23 am)
[PATCH 6/8] Add stream helper library, Ramkumar Ramachandra, (Thu Jul 15, 9:23 am)
[PATCH 7/8] Add infrastructure to write revisions in fast- ..., Ramkumar Ramachandra, (Thu Jul 15, 9:23 am)
[PATCH 8/8] Add SVN dump parser, Ramkumar Ramachandra, (Thu Jul 15, 9:23 am)
Re: [PATCH 2/8] Introduce vcs-svn lib, Jonathan Nieder, (Thu Jul 15, 10:46 am)
Re: [PATCH 3/8] Add memory pool library, Jonathan Nieder, (Thu Jul 15, 11:57 am)
Re: [PATCH 4/8] Add treap implementation, Jonathan Nieder, (Thu Jul 15, 12:09 pm)
Re: [PATCH 3/8] Add memory pool library, Ramkumar Ramachandra, (Thu Jul 15, 12:12 pm)
Re: [PATCH 2/8] Introduce vcs-svn lib, Ramkumar Ramachandra, (Thu Jul 15, 12:15 pm)
Re: [PATCH 4/8] Add treap implementation, Ramkumar Ramachandra, (Thu Jul 15, 12:18 pm)
Re: [PATCH 6/8] Add stream helper library, Jonathan Nieder, (Thu Jul 15, 12:19 pm)
Re: [PATCH 8/8] Add SVN dump parser, Jonathan Nieder, (Thu Jul 15, 12:52 pm)
Re: [PATCH 8/8] Add SVN dump parser, Jonathan Nieder, (Thu Jul 15, 1:04 pm)
Re: [PATCH 0/8] Resurrect rr/svn-export, Jonathan Nieder, (Fri Jul 16, 3:13 am)
[PATCH 3/9] Add memory pool library, Jonathan Nieder, (Fri Jul 16, 3:16 am)
[PATCH 4/9] Add treap implementation, Jonathan Nieder, (Fri Jul 16, 3:23 am)
Re: [PATCH 4/9] Add treap implementation, Jonathan Nieder, (Fri Jul 16, 11:26 am)
[PATCH 0/10] rr/svn-export reroll, Jonathan Nieder, (Mon Aug 9, 2:57 pm)
[PATCH 02/10] Introduce vcs-svn lib, Jonathan Nieder, (Mon Aug 9, 3:04 pm)
[PATCH 03/10] Add memory pool library, Jonathan Nieder, (Mon Aug 9, 3:11 pm)
[PATCH 04/10] Add treap implementation, Jonathan Nieder, (Mon Aug 9, 3:17 pm)
[PATCH 05/10] Add string-specific memory pool, Jonathan Nieder, (Mon Aug 9, 3:34 pm)
[PATCH 06/10] Add stream helper library, Jonathan Nieder, (Mon Aug 9, 3:39 pm)
[PATCH 08/10] SVN dump parser, Jonathan Nieder, (Mon Aug 9, 3:55 pm)
PATCH 09/10] Update svn-fe manual, Jonathan Nieder, (Mon Aug 9, 3:55 pm)
Re: [PATCH 0/10] rr/svn-export reroll, Ramkumar Ramachandra, (Tue Aug 10, 5:53 am)
Re: [PATCH 0/10] rr/svn-export reroll, Jonathan Nieder, (Tue Aug 10, 6:53 pm)
Re: [PATCH 05/10] Add string-specific memory pool, Junio C Hamano, (Thu Aug 12, 10:22 am)
Re: [PATCH 04/10] Add treap implementation, Junio C Hamano, (Thu Aug 12, 10:22 am)
Re: [PATCH 08/10] SVN dump parser, Junio C Hamano, (Thu Aug 12, 10:22 am)
Re: [PATCH 05/10] Add string-specific memory pool, Jonathan Nieder, (Thu Aug 12, 2:30 pm)
Re: [PATCH 04/10] Add treap implementation, Jonathan Nieder, (Thu Aug 12, 3:02 pm)
Re: [PATCH 04/10] Add treap implementation, Jonathan Nieder, (Thu Aug 12, 3:11 pm)
Re: [PATCH 04/10] Add treap implementation, Junio C Hamano, (Thu Aug 12, 3:44 pm)
[PATCH/WIP 00/16] svn delta applier, Jonathan Nieder, (Sun Oct 10, 7:34 pm)
[PATCH 01/16] vcs-svn: Eliminate global byte_buffer[] array, Jonathan Nieder, (Sun Oct 10, 7:37 pm)
[PATCH 03/16] vcs-svn: Collect line_buffer data in a struct, Jonathan Nieder, (Sun Oct 10, 7:39 pm)
[PATCH 07/16] vcs-svn: Add binary-safe read() function, Jonathan Nieder, (Sun Oct 10, 7:47 pm)
[PATCH 10/16] vcs-svn: Allow character-oriented input, Jonathan Nieder, (Sun Oct 10, 7:52 pm)
[PATCH 12/16] vcs-svn: Learn to parse variable-length integers, Jonathan Nieder, (Sun Oct 10, 7:55 pm)
[PATCH 13/16] vcs-svn: Learn to check for SVN\0 magic, Jonathan Nieder, (Sun Oct 10, 7:58 pm)
[PATCH 14/16] compat: helper for detecting unsigned overflow, Jonathan Nieder, (Sun Oct 10, 7:59 pm)
[PATCH/RFC 16'/16] vcs-svn: Add svn delta parser, Jonathan Nieder, (Sun Oct 10, 9:01 pm)
[PATCH/RFC 0/11] Building up the delta parser, Jonathan Nieder, (Wed Oct 13, 2:17 am)
[PATCH 02/11] vcs-svn: Skeleton of an svn delta parser, Jonathan Nieder, (Wed Oct 13, 2:21 am)
[PATCH 04/11] vcs-svn: Read inline data from deltas, Jonathan Nieder, (Wed Oct 13, 2:35 am)
[PATCH 05/11] vcs-svn: Read instructions from deltas, Jonathan Nieder, (Wed Oct 13, 2:38 am)
[PATCH 07/11] vcs-svn: Check declared number of output bytes, Jonathan Nieder, (Wed Oct 13, 2:41 am)
[PATCH 09/11] vcs-svn: Let deltas use data from postimage, Jonathan Nieder, (Wed Oct 13, 2:50 am)
[PATCH 11/11] vcs-svn: Allow deltas to copy from preimage, Jonathan Nieder, (Wed Oct 13, 2:58 am)
[PATCH 11/11] vcs-svn: Allow deltas to copy from preimage, Jonathan Nieder, (Wed Oct 13, 3:00 am)
Re: [PATCH/RFC 0/11] Building up the delta parser, Ramkumar Ramachandra, (Mon Oct 18, 10:00 am)
Re: [PATCH/RFC 0/11] Building up the delta parser, Jonathan Nieder, (Mon Oct 18, 10:03 am)