vcs-svn: let deltas use data from preimage

The copyfrom_source instruction appends data from the preimage buffer
to the end of output.  Its arguments are a length and an offset
relative to the beginning of the source view.

With this change, the delta applier is able to reproduce all 5,636,613
blobs in the early history of the ASF repository.  Tested with

	mkfifo backflow
	svn-fe <svn-asf-public-r0:940166 3<backflow |
	git fast-import --cat-blob-fd=3 3>backflow

with svn-asf-public-r0:940166 produced by whatever version of
Subversion the dumps in /dump/ on svn.apache.org use (presumably
1.6.something).

Improved-by: Ramkumar Ramachandra <artagnon@gmail.com>
Improved-by: David Barr <david.barr@cordelta.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Acked-by: Ramkumar Ramachandra <artagnon@gmail.com>

diff --git a/t/t9011-svn-da.sh b/t/t9011-svn-da.sh
index f9573a1c40b0883f241d158fe8ed7237740283e7..b38d16f9dbd6e6f575e12f81e7d6546f07e53f1f 100755 (executable)
--- a/t/t9011-svn-da.sh
+++ b/t/t9011-svn-da.sh
@@ -210,4 +210,39 @@ test_expect_success 'catch copy that overflows' '
        test_must_fail test-svn-fe -d preimage copytarget.overflow $len
 '
 
+test_expect_success 'copyfrom source' '
+       printf foo >expect &&
+       printf "SVNQ%b%b" "Q\003\003\002Q" "\003Q" | q_to_nul >copysource.all &&
+       test-svn-fe -d preimage copysource.all 11 >actual &&
+       test_cmp expect actual
+'
+
+test_expect_success 'copy backwards' '
+       printf oof >expect &&
+       printf "SVNQ%b%b" "Q\003\003\006Q" "\001\002\001\001\001Q" |
+               q_to_nul >copysource.rev &&
+       test-svn-fe -d preimage copysource.rev 15 >actual &&
+       test_cmp expect actual
+'
+
+test_expect_success 'offsets are relative to window' '
+       printf fo >expect &&
+       printf "SVNQ%b%b%b%b" "Q\003\001\002Q" "\001Q" \
+               "\002\001\001\002Q" "\001Q" |
+               q_to_nul >copysource.two &&
+       test-svn-fe -d preimage copysource.two 18 >actual &&
+       test_cmp expect actual
+'
+
+test_expect_success 'example from notes/svndiff' '
+       printf aaaaccccdddddddd >expect &&
+       printf aaaabbbbcccc >source &&
+       printf "SVNQ%b%b%s" "Q\014\020\007\001" \
+               "\004Q\004\010\0201\0107\010" d |
+               q_to_nul >delta.example &&
+       len=$(wc -c <delta.example) &&
+       test-svn-fe -d source delta.example $len >actual &&
+       test_cmp expect actual
+'
+
 test_done

diff --git a/vcs-svn/svndiff.c b/vcs-svn/svndiff.c
index a02eee0410111a31f5a35e24cd6916c780041f05..9ee41bbc90807ddd82b63c9250f670fecf86a7f5 100644 (file)
--- a/vcs-svn/svndiff.c
+++ b/vcs-svn/svndiff.c
@@ -24,6 +24,7 @@
  * view_selector ::= copyfrom_source
  *   | copyfrom_target
  *   ;
+ * copyfrom_source ::= # binary 00 000000;
  * copyfrom_target ::= # binary 01 000000;
  * copyfrom_data ::= # binary 10 000000;
  * packed_view_selector ::= # view_selector OR-ed with 6 bit value;
@@ -34,6 +35,7 @@
  */
 
 #define INSN_MASK      0xc0
+#define INSN_COPYFROM_SOURCE   0x00
 #define INSN_COPYFROM_TARGET   0x40
 #define INSN_COPYFROM_DATA     0x80
 #define OPERAND_MASK   0x3f
@@ -43,12 +45,13 @@
 #define VLI_BITS_PER_DIGIT 7
 
 struct window {
+       struct sliding_view *in;
        struct strbuf out;
        struct strbuf instructions;
        struct strbuf data;
 };
 
-#define WINDOW_INIT    { STRBUF_INIT, STRBUF_INIT, STRBUF_INIT }
+#define WINDOW_INIT(w) { (w), STRBUF_INIT, STRBUF_INIT, STRBUF_INIT }
 
 static void window_release(struct window *ctx)
 {
@@ -161,6 +164,19 @@ static int read_length(struct line_buffer *in, size_t *result, off_t *len)
        return 0;
 }
 
+static int copyfrom_source(struct window *ctx, const char **instructions,
+                          size_t nbytes, const char *insns_end)
+{
+       size_t offset;
+       if (parse_int(instructions, &offset, insns_end))
+               return -1;
+       if (unsigned_add_overflows(offset, nbytes) ||
+           offset + nbytes > ctx->in->width)
+               return error("invalid delta: copies source data outside view");
+       strbuf_add(&ctx->out, ctx->in->buf.buf + offset, nbytes);
+       return 0;
+}
+
 static int copyfrom_target(struct window *ctx, const char **instructions,
                           size_t nbytes, const char *instructions_end)
 {
@@ -209,12 +225,14 @@ static int execute_one_instruction(struct window *ctx,
        if (parse_first_operand(instructions, &nbytes, insns_end))
                return -1;
        switch (instruction & INSN_MASK) {
+       case INSN_COPYFROM_SOURCE:
+               return copyfrom_source(ctx, instructions, nbytes, insns_end);
        case INSN_COPYFROM_TARGET:
                return copyfrom_target(ctx, instructions, nbytes, insns_end);
        case INSN_COPYFROM_DATA:
                return copyfrom_data(ctx, data_pos, nbytes);
        default:
-               return error("Unknown instruction %x", instruction);
+               return error("invalid delta: unrecognized instruction");
        }
 }
 
@@ -238,9 +256,9 @@ static int apply_window_in_core(struct window *ctx)
 }
 
 static int apply_one_window(struct line_buffer *delta, off_t *delta_len,
-                           FILE *out)
+                           struct sliding_view *preimage, FILE *out)
 {
-       struct window ctx = WINDOW_INIT;
+       struct window ctx = WINDOW_INIT(preimage);
        size_t out_len;
        size_t instructions_len;
        size_t data_len;
@@ -283,7 +301,7 @@ int svndiff0_apply(struct line_buffer *delta, off_t delta_len,
                if (read_offset(delta, &pre_off, &delta_len) ||
                    read_length(delta, &pre_len, &delta_len) ||
                    move_window(preimage, pre_off, pre_len) ||
-                   apply_one_window(delta, &delta_len, postimage))
+                   apply_one_window(delta, &delta_len, preimage, postimage))
                        return -1;
        }
        return 0;