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authorJonathan Nieder <jrnieder@gmail.com>2010-10-13 09:39:44 (GMT)
committerJonathan Nieder <jrnieder@gmail.com>2011-03-28 04:27:55 (GMT)
commitec71aa2e1f229b90092e6678ac7c2dca3d15b5f3 (patch)
tree020d2f4773ec563f9458ef7fe786b0631ec3a13d /vcs-svn/svndiff.c
parentef2ac77e9f8f4819f75cf52721567463e60a805c (diff)
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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>
Diffstat (limited to 'vcs-svn/svndiff.c')
-rw-r--r--vcs-svn/svndiff.c115
1 files changed, 108 insertions, 7 deletions
diff --git a/vcs-svn/svndiff.c b/vcs-svn/svndiff.c
index 8968fdb..ed1d4a0 100644
--- 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;