vcs-svn: implement copyfrom_data delta instruction

The copyfrom_data instruction copies a few bytes verbatim from the
novel text section of a window to the postimage.

[jn: with memory leak fix from David]

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 d9acd0c8a61f519bf99eaa4d8856ace56cefca96..ba8ce052aa05606290d8b23c101c9e0dacc9d318 100755 (executable)
--- a/t/t9011-svn-da.sh
+++ b/t/t9011-svn-da.sh
@@ -138,4 +138,35 @@ test_expect_success 'reject truncated inline data (after instruction section)' '
        test_must_fail test-svn-fe -d preimage insn.trunc 11
 '
 
+test_expect_success 'copyfrom_data' '
+       echo hi >expect &&
+       printf "SVNQ%b%b%b" "QQ\003\001\003" "\0203" "hi\n" | q_to_nul >copydat &&
+       test-svn-fe -d preimage copydat 13 >actual &&
+       test_cmp expect actual
+'
+
+test_expect_success 'multiple copyfrom_data' '
+       echo hi >expect &&
+       printf "SVNQ%b%b%b%b%b" "QQ\003\002\003" "\0201\0202" "hi\n" \
+               "QQQ\002Q" "\0200Q" | q_to_nul >copy.multi &&
+       len=$(wc -c <copy.multi) &&
+       test-svn-fe -d preimage copy.multi $len >actual &&
+       test_cmp expect actual
+'
+
+test_expect_success 'incomplete multiple insn' '
+       printf "SVNQ%b%b%b" "QQ\003\002\003" "\0203\0200" "hi\n" |
+               q_to_nul >copy.partial &&
+       len=$(wc -c <copy.partial) &&
+       test_must_fail test-svn-fe -d preimage copy.partial $len
+'
+
+test_expect_success 'catch attempt to copy missing data' '
+       printf "SVNQ%b%b%s%b%s" "QQ\002\002\001" "\0201\0201" "X" \
+                       "QQQQ\002" "YZ" |
+               q_to_nul >copy.incomplete &&
+       len=$(wc -c <copy.incomplete) &&
+       test_must_fail test-svn-fe -d preimage copy.incomplete $len
+'
+
 test_done

diff --git a/vcs-svn/svndiff.c b/vcs-svn/svndiff.c
index 8968fdb4eb7c5d09edc3a865a9639dc9c7cf8491..ed1d4a08be83b2255fb967b628d24483ba782a5c 100644 (file)
--- a/vcs-svn/svndiff.c
+++ b/vcs-svn/svndiff.c
@@ -15,28 +15,49 @@
  *
  * svndiff0 ::= 'SVN\0' window*
  * window ::= int int int int int instructions inline_data;
+ * instructions ::= instruction*;
+ * instruction ::= view_selector int int
+ *   | copyfrom_data int
+ *   | packed_view_selector int
+ *   | packed_copyfrom_data
+ *   ;
+ * copyfrom_data ::= # binary 10 000000;
+ * packed_copyfrom_data ::= # copyfrom_data OR-ed with 6 bit value;
  * int ::= highdigit* lowdigit;
  * highdigit ::= # binary 1000 0000 OR-ed with 7 bit value;
  * lowdigit ::= # 7 bit value;
  */
 
+#define INSN_MASK      0xc0
+#define INSN_COPYFROM_DATA     0x80
+#define OPERAND_MASK   0x3f
+
 #define VLI_CONTINUE   0x80
 #define VLI_DIGIT_MASK 0x7f
 #define VLI_BITS_PER_DIGIT 7
 
 struct window {
+       struct strbuf out;
        struct strbuf instructions;
        struct strbuf data;
 };
 
-#define WINDOW_INIT    { STRBUF_INIT, STRBUF_INIT }
+#define WINDOW_INIT    { STRBUF_INIT, STRBUF_INIT, STRBUF_INIT }
 
 static void window_release(struct window *ctx)
 {
+       strbuf_release(&ctx->out);
        strbuf_release(&ctx->instructions);
        strbuf_release(&ctx->data);
 }
 
+static int write_strbuf(struct strbuf *sb, FILE *out)
+{
+       if (fwrite(sb->buf, 1, sb->len, out) == sb->len)        /* Success. */
+               return 0;
+       return error("cannot write delta postimage: %s", strerror(errno));
+}
+
 static int error_short_read(struct line_buffer *input)
 {
        if (buffer_ferror(input))
@@ -93,6 +114,25 @@ static int read_int(struct line_buffer *in, uintmax_t *result, off_t *len)
        return error_short_read(in);
 }
 
+static int parse_int(const char **buf, size_t *result, const char *end)
+{
+       size_t rv = 0;
+       const char *pos;
+       for (pos = *buf; pos != end; pos++) {
+               unsigned char ch = *pos;
+
+               rv <<= VLI_BITS_PER_DIGIT;
+               rv += (ch & VLI_DIGIT_MASK);
+               if (ch & VLI_CONTINUE)
+                       continue;
+
+               *result = rv;
+               *buf = pos + 1;
+               return 0;
+       }
+       return error("invalid delta: unexpected end of instructions section");
+}
+
 static int read_offset(struct line_buffer *in, off_t *result, off_t *len)
 {
        uintmax_t val;
@@ -115,7 +155,64 @@ static int read_length(struct line_buffer *in, size_t *result, off_t *len)
        return 0;
 }
 
-static int apply_one_window(struct line_buffer *delta, off_t *delta_len)
+static int copyfrom_data(struct window *ctx, size_t *data_pos, size_t nbytes)
+{
+       const size_t pos = *data_pos;
+       if (unsigned_add_overflows(pos, nbytes) ||
+           pos + nbytes > ctx->data.len)
+               return error("invalid delta: copies unavailable inline data");
+       strbuf_add(&ctx->out, ctx->data.buf + pos, nbytes);
+       *data_pos += nbytes;
+       return 0;
+}
+
+static int parse_first_operand(const char **buf, size_t *out, const char *end)
+{
+       size_t result = (unsigned char) *(*buf)++ & OPERAND_MASK;
+       if (result) {   /* immediate operand */
+               *out = result;
+               return 0;
+       }
+       return parse_int(buf, out, end);
+}
+
+static int execute_one_instruction(struct window *ctx,
+                               const char **instructions, size_t *data_pos)
+{
+       unsigned int instruction;
+       const char *insns_end = ctx->instructions.buf + ctx->instructions.len;
+       size_t nbytes;
+       assert(ctx);
+       assert(instructions && *instructions);
+       assert(data_pos);
+
+       instruction = (unsigned char) **instructions;
+       if (parse_first_operand(instructions, &nbytes, insns_end))
+               return -1;
+       if ((instruction & INSN_MASK) != INSN_COPYFROM_DATA)
+               return error("Unknown instruction %x", instruction);
+       return copyfrom_data(ctx, data_pos, nbytes);
+}
+
+static int apply_window_in_core(struct window *ctx)
+{
+       const char *instructions;
+       size_t data_pos = 0;
+
+       /*
+        * Fill ctx->out.buf using data from the source, target,
+        * and inline data views.
+        */
+       for (instructions = ctx->instructions.buf;
+            instructions != ctx->instructions.buf + ctx->instructions.len;
+            )
+               if (execute_one_instruction(ctx, &instructions, &data_pos))
+                       return -1;
+       return 0;
+}
+
+static int apply_one_window(struct line_buffer *delta, off_t *delta_len,
+                           FILE *out)
 {
        struct window ctx = WINDOW_INIT;
        size_t out_len;
@@ -127,13 +224,17 @@ static int apply_one_window(struct line_buffer *delta, off_t *delta_len)
        if (read_length(delta, &out_len, delta_len) ||
            read_length(delta, &instructions_len, delta_len) ||
            read_length(delta, &data_len, delta_len) ||
-           read_chunk(delta, delta_len, &ctx.instructions, instructions_len))
+           read_chunk(delta, delta_len, &ctx.instructions, instructions_len) ||
+           read_chunk(delta, delta_len, &ctx.data, data_len))
+               goto error_out;
+       strbuf_grow(&ctx.out, out_len);
+       if (apply_window_in_core(&ctx))
                goto error_out;
-       if (instructions_len) {
-               error("What do you think I am?  A delta applier?");
+       if (ctx.out.len != out_len) {
+               error("invalid delta: incorrect postimage length");
                goto error_out;
        }
-       if (read_chunk(delta, delta_len, &ctx.data, data_len))
+       if (write_strbuf(&ctx.out, out))
                goto error_out;
        window_release(&ctx);
        return 0;
@@ -156,7 +257,7 @@ 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))
+                   apply_one_window(delta, &delta_len, postimage))
                        return -1;
        }
        return 0;