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>
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Jonathan Nieder
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ef2ac77e9f
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ec71aa2e1f
@ -138,4 +138,35 @@ test_expect_success 'reject truncated inline data (after instruction section)' '
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test_must_fail test-svn-fe -d preimage insn.trunc 11
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'
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test_expect_success 'copyfrom_data' '
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echo hi >expect &&
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printf "SVNQ%b%b%b" "QQ\003\001\003" "\0203" "hi\n" | q_to_nul >copydat &&
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test-svn-fe -d preimage copydat 13 >actual &&
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test_cmp expect actual
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'
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test_expect_success 'multiple copyfrom_data' '
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echo hi >expect &&
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printf "SVNQ%b%b%b%b%b" "QQ\003\002\003" "\0201\0202" "hi\n" \
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"QQQ\002Q" "\0200Q" | q_to_nul >copy.multi &&
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len=$(wc -c <copy.multi) &&
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test-svn-fe -d preimage copy.multi $len >actual &&
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test_cmp expect actual
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'
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test_expect_success 'incomplete multiple insn' '
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printf "SVNQ%b%b%b" "QQ\003\002\003" "\0203\0200" "hi\n" |
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q_to_nul >copy.partial &&
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len=$(wc -c <copy.partial) &&
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test_must_fail test-svn-fe -d preimage copy.partial $len
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'
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test_expect_success 'catch attempt to copy missing data' '
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printf "SVNQ%b%b%s%b%s" "QQ\002\002\001" "\0201\0201" "X" \
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"QQQQ\002" "YZ" |
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q_to_nul >copy.incomplete &&
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len=$(wc -c <copy.incomplete) &&
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test_must_fail test-svn-fe -d preimage copy.incomplete $len
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'
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test_done
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@ -15,28 +15,49 @@
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*
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* svndiff0 ::= 'SVN\0' window*
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* window ::= int int int int int instructions inline_data;
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* instructions ::= instruction*;
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* instruction ::= view_selector int int
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* | copyfrom_data int
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* | packed_view_selector int
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* | packed_copyfrom_data
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* ;
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* copyfrom_data ::= # binary 10 000000;
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* packed_copyfrom_data ::= # copyfrom_data OR-ed with 6 bit value;
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* int ::= highdigit* lowdigit;
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* highdigit ::= # binary 1000 0000 OR-ed with 7 bit value;
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* lowdigit ::= # 7 bit value;
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*/
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#define INSN_MASK 0xc0
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#define INSN_COPYFROM_DATA 0x80
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#define OPERAND_MASK 0x3f
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#define VLI_CONTINUE 0x80
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#define VLI_DIGIT_MASK 0x7f
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#define VLI_BITS_PER_DIGIT 7
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struct window {
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struct strbuf out;
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struct strbuf instructions;
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struct strbuf data;
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};
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#define WINDOW_INIT { STRBUF_INIT, STRBUF_INIT }
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#define WINDOW_INIT { STRBUF_INIT, STRBUF_INIT, STRBUF_INIT }
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static void window_release(struct window *ctx)
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{
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strbuf_release(&ctx->out);
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strbuf_release(&ctx->instructions);
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strbuf_release(&ctx->data);
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}
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static int write_strbuf(struct strbuf *sb, FILE *out)
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{
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if (fwrite(sb->buf, 1, sb->len, out) == sb->len) /* Success. */
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return 0;
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return error("cannot write delta postimage: %s", strerror(errno));
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}
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static int error_short_read(struct line_buffer *input)
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{
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if (buffer_ferror(input))
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@ -93,6 +114,25 @@ static int read_int(struct line_buffer *in, uintmax_t *result, off_t *len)
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return error_short_read(in);
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}
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static int parse_int(const char **buf, size_t *result, const char *end)
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{
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size_t rv = 0;
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const char *pos;
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for (pos = *buf; pos != end; pos++) {
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unsigned char ch = *pos;
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rv <<= VLI_BITS_PER_DIGIT;
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rv += (ch & VLI_DIGIT_MASK);
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if (ch & VLI_CONTINUE)
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continue;
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*result = rv;
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*buf = pos + 1;
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return 0;
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}
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return error("invalid delta: unexpected end of instructions section");
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}
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static int read_offset(struct line_buffer *in, off_t *result, off_t *len)
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{
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uintmax_t val;
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@ -115,7 +155,64 @@ static int read_length(struct line_buffer *in, size_t *result, off_t *len)
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return 0;
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}
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static int apply_one_window(struct line_buffer *delta, off_t *delta_len)
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static int copyfrom_data(struct window *ctx, size_t *data_pos, size_t nbytes)
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{
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const size_t pos = *data_pos;
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if (unsigned_add_overflows(pos, nbytes) ||
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pos + nbytes > ctx->data.len)
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return error("invalid delta: copies unavailable inline data");
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strbuf_add(&ctx->out, ctx->data.buf + pos, nbytes);
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*data_pos += nbytes;
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return 0;
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}
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static int parse_first_operand(const char **buf, size_t *out, const char *end)
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{
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size_t result = (unsigned char) *(*buf)++ & OPERAND_MASK;
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if (result) { /* immediate operand */
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*out = result;
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return 0;
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}
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return parse_int(buf, out, end);
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}
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static int execute_one_instruction(struct window *ctx,
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const char **instructions, size_t *data_pos)
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{
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unsigned int instruction;
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const char *insns_end = ctx->instructions.buf + ctx->instructions.len;
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size_t nbytes;
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assert(ctx);
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assert(instructions && *instructions);
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assert(data_pos);
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instruction = (unsigned char) **instructions;
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if (parse_first_operand(instructions, &nbytes, insns_end))
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return -1;
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if ((instruction & INSN_MASK) != INSN_COPYFROM_DATA)
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return error("Unknown instruction %x", instruction);
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return copyfrom_data(ctx, data_pos, nbytes);
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}
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static int apply_window_in_core(struct window *ctx)
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{
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const char *instructions;
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size_t data_pos = 0;
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/*
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* Fill ctx->out.buf using data from the source, target,
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* and inline data views.
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*/
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for (instructions = ctx->instructions.buf;
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instructions != ctx->instructions.buf + ctx->instructions.len;
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)
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if (execute_one_instruction(ctx, &instructions, &data_pos))
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return -1;
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return 0;
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}
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static int apply_one_window(struct line_buffer *delta, off_t *delta_len,
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FILE *out)
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{
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struct window ctx = WINDOW_INIT;
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size_t out_len;
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@ -127,13 +224,17 @@ static int apply_one_window(struct line_buffer *delta, off_t *delta_len)
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if (read_length(delta, &out_len, delta_len) ||
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read_length(delta, &instructions_len, delta_len) ||
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read_length(delta, &data_len, delta_len) ||
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read_chunk(delta, delta_len, &ctx.instructions, instructions_len))
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read_chunk(delta, delta_len, &ctx.instructions, instructions_len) ||
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read_chunk(delta, delta_len, &ctx.data, data_len))
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goto error_out;
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if (instructions_len) {
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error("What do you think I am? A delta applier?");
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strbuf_grow(&ctx.out, out_len);
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if (apply_window_in_core(&ctx))
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goto error_out;
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if (ctx.out.len != out_len) {
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error("invalid delta: incorrect postimage length");
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goto error_out;
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}
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if (read_chunk(delta, delta_len, &ctx.data, data_len))
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if (write_strbuf(&ctx.out, out))
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goto error_out;
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window_release(&ctx);
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return 0;
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@ -156,7 +257,7 @@ int svndiff0_apply(struct line_buffer *delta, off_t delta_len,
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if (read_offset(delta, &pre_off, &delta_len) ||
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read_length(delta, &pre_len, &delta_len) ||
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move_window(preimage, pre_off, pre_len) ||
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apply_one_window(delta, &delta_len))
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apply_one_window(delta, &delta_len, postimage))
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return -1;
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}
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return 0;
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