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authorJonathan Nieder <jrnieder@gmail.com>2010-10-13 09:21:43 (GMT)
committerJonathan Nieder <jrnieder@gmail.com>2011-03-28 03:42:53 (GMT)
commit252712111fad127db365e3dd764309fe5658679a (patch)
tree3f28203392bb674751e05fb20908f882aa3d50f8 /vcs-svn/svndiff.c
parentddcc8c5b469d2564dbacd629a873e7703f2dbd83 (diff)
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vcs-svn: parse svndiff0 window header
Each window in a subversion delta (svndiff0-format file) starts with a window header, consisting of five integers with variable-length representation: source view offset source view length output length instructions length auxiliary data length Parse it. The result is not usable for deltas with nonempty postimage yet; in fact, this only adds support for deltas without any instructions or auxiliary data. This is a good place to stop, though, since that little support lets us add some simple passing tests concerning error handling to the test suite. Improved-by: Ramkumar Ramachandra <artagnon@gmail.com> Improved-by: David Barr <david.barr@cordelta.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Diffstat (limited to 'vcs-svn/svndiff.c')
-rw-r--r--vcs-svn/svndiff.c92
1 files changed, 87 insertions, 5 deletions
diff --git a/vcs-svn/svndiff.c b/vcs-svn/svndiff.c
index 5916036..249efb6 100644
--- a/vcs-svn/svndiff.c
+++ b/vcs-svn/svndiff.c
@@ -13,8 +13,16 @@
* See http://svn.apache.org/repos/asf/subversion/trunk/notes/svndiff.
*
* svndiff0 ::= 'SVN\0' window*
+ * window ::= int int int int int instructions inline_data;
+ * 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 error_short_read(struct line_buffer *input)
{
if (buffer_ferror(input))
@@ -28,17 +36,84 @@ static int read_magic(struct line_buffer *in, off_t *len)
struct strbuf sb = STRBUF_INIT;
if (*len < sizeof(magic) ||
- buffer_read_binary(in, &sb, sizeof(magic)) != sizeof(magic))
- return error_short_read(in);
+ buffer_read_binary(in, &sb, sizeof(magic)) != sizeof(magic)) {
+ error_short_read(in);
+ strbuf_release(&sb);
+ return -1;
+ }
- if (memcmp(sb.buf, magic, sizeof(magic)))
+ if (memcmp(sb.buf, magic, sizeof(magic))) {
+ strbuf_release(&sb);
return error("invalid delta: unrecognized file type");
+ }
*len -= sizeof(magic);
strbuf_release(&sb);
return 0;
}
+static int read_int(struct line_buffer *in, uintmax_t *result, off_t *len)
+{
+ uintmax_t rv = 0;
+ off_t sz;
+ for (sz = *len; sz; sz--) {
+ const int ch = buffer_read_char(in);
+ if (ch == EOF)
+ break;
+
+ rv <<= VLI_BITS_PER_DIGIT;
+ rv += (ch & VLI_DIGIT_MASK);
+ if (ch & VLI_CONTINUE)
+ continue;
+
+ *result = rv;
+ *len = sz - 1;
+ return 0;
+ }
+ return error_short_read(in);
+}
+
+static int read_offset(struct line_buffer *in, off_t *result, off_t *len)
+{
+ uintmax_t val;
+ if (read_int(in, &val, len))
+ return -1;
+ if (val > maximum_signed_value_of_type(off_t))
+ return error("unrepresentable offset in delta: %"PRIuMAX"", val);
+ *result = val;
+ return 0;
+}
+
+static int read_length(struct line_buffer *in, size_t *result, off_t *len)
+{
+ uintmax_t val;
+ if (read_int(in, &val, len))
+ return -1;
+ if (val > SIZE_MAX)
+ return error("unrepresentable length in delta: %"PRIuMAX"", val);
+ *result = val;
+ return 0;
+}
+
+static int apply_one_window(struct line_buffer *delta, off_t *delta_len)
+{
+ size_t out_len;
+ size_t instructions_len;
+ size_t data_len;
+ assert(delta_len);
+
+ /* "source view" offset and length already handled; */
+ if (read_length(delta, &out_len, delta_len) ||
+ read_length(delta, &instructions_len, delta_len) ||
+ read_length(delta, &data_len, delta_len))
+ return -1;
+ if (instructions_len)
+ return error("What do you think I am? A delta applier?");
+ if (data_len)
+ return error("No support for inline data yet");
+ return 0;
+}
+
int svndiff0_apply(struct line_buffer *delta, off_t delta_len,
struct sliding_view *preimage, FILE *postimage)
{
@@ -46,7 +121,14 @@ int svndiff0_apply(struct line_buffer *delta, off_t delta_len,
if (read_magic(delta, &delta_len))
return -1;
- if (delta_len)
- return error("What do you think I am? A delta applier?");
+ while (delta_len) { /* For each window: */
+ off_t pre_off;
+ size_t pre_len;
+
+ if (read_offset(delta, &pre_off, &delta_len) ||
+ read_length(delta, &pre_len, &delta_len) ||
+ apply_one_window(delta, &delta_len))
+ return -1;
+ }
return 0;
}