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/*
* Licensed under a two-clause BSD-style license.
* See LICENSE for details.
*/
#include "git-compat-util.h"
#include "sliding_window.h"
#include "line_buffer.h"
#include "svndiff.h"
/*
* svndiff0 applier
*
* 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
struct window {
struct strbuf data;
};
#define WINDOW_INIT { STRBUF_INIT }
static void window_release(struct window *ctx)
{
strbuf_release(&ctx->data);
}
static int error_short_read(struct line_buffer *input)
{
if (buffer_ferror(input))
return error("error reading delta: %s", strerror(errno));
return error("invalid delta: unexpected end of file");
}
static int read_chunk(struct line_buffer *delta, off_t *delta_len,
struct strbuf *buf, size_t len)
{
strbuf_reset(buf);
if (len > *delta_len ||
buffer_read_binary(delta, buf, len) != len)
return error_short_read(delta);
*delta_len -= buf->len;
return 0;
}
static int read_magic(struct line_buffer *in, off_t *len)
{
static const char magic[] = {'S', 'V', 'N', '\0'};
struct strbuf sb = STRBUF_INIT;
if (read_chunk(in, len, &sb, sizeof(magic))) {
strbuf_release(&sb);
return -1;
}
if (memcmp(sb.buf, magic, sizeof(magic))) {
strbuf_release(&sb);
return error("invalid delta: unrecognized file type");
}
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)
{
struct window ctx = WINDOW_INIT;
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))
goto error_out;
if (instructions_len) {
error("What do you think I am? A delta applier?");
goto error_out;
}
if (read_chunk(delta, delta_len, &ctx.data, data_len))
goto error_out;
window_release(&ctx);
return 0;
error_out:
window_release(&ctx);
return -1;
}
int svndiff0_apply(struct line_buffer *delta, off_t delta_len,
struct sliding_view *preimage, FILE *postimage)
{
assert(delta && preimage && postimage);
if (read_magic(delta, &delta_len))
return -1;
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) ||
move_window(preimage, pre_off, pre_len) ||
apply_one_window(delta, &delta_len))
return -1;
}
return 0;
}
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